Patent Application
20200256750
The present invention relates to a force sensor, and more particularly to a sensor having a function of outputting a force applied in a predetermined axial direction and a moment (torque) applied around a predetermined rotational axis as an electric signal.
For example, Patent Literature 1 describes a force sensor having a function of outputting a force applied in a predetermined axial direction and a moment applied around a predetermined rotational axis as an electric signal, and widely used for force control in industrial robots. In recent years, force sensors are also adopted in life supporting robots. With expansion of the market of the force sensor, there are increased demands for lower prices and higher performance in the force sensors.
Meanwhile, the force sensor includes a capacitance type force sensor that detects one of a force and a moment on the basis of a variation amount of an electrostatic capacitance value of a capacitive element, and a strain gauge type force sensor that detects one of the force and the moment on the basis of a variation amount of an electric resistance value of a strain gauge. Among them, the strain gauge type force sensor includes a strain body (elastic body) having a complicated structure, and further needs a step of attaching the strain gauge to the strain generating body in the manufacturing process. Due to this high manufacturing cost of the strain gauge type force sensor, it is difficult to achieve lower prices.
In contrast, the electrostatic capacitance type force sensor can measure one of a force and a moment applied by a pair of parallel flat plates (capacitive elements), making it possible to simplify the structure of the strain generating body including the capacitive elements. That is, since the capacitance type force sensor needs relatively lower manufacturing cost, there is an advantage of easily lowering the price. Therefore, by further simplifying the structure of the strain generating body including the capacitive elements, it is possible to further lower the price in the capacitance type force sensor.
Under such backgrounds, the applicants proposed in the international patent application PCT/JP 2017/008843 (JP No. 2017-539470 A) a force sensor including an annular deformable body arranged so as to surround an origin O when viewed in the Z-axis direction and configured to generate elastic deformation by action of one of a force and a moment, in which the deformable body includes a curved portion. More specifically, the force sensor includes a deformable body including: two fixed portions fixed with respect to the XYZ three-dimensional coordinate system; two force receiving portions positioned alternately with the two fixed portions in an annular path of the deformable body and configured to receive ation of one of the force and the moment; and four deformable portions positioned between the fixed portion and the force receiving portion adjacent to each other in the annular path, and each of the deformable portions is curved (bulges) in the negative direction on the Z-axis, for example.
The applicants performed intensive studies to further enhance the force sensor as described above and have found that providing a curved portion at a connecting portion between the deformable portion and the fixed portion and the force receiving portion can alleviate stress concentration on the connecting portion to further enhance the reliability of the force sensor.
The present invention is on the basis of the above findings. That is, an object of the present invention is to provide a highly reliable capacitance type force sensor including a deformable body having a curved portion.
A force sensor according to a first aspect of the present invention detects at least one of a force in each axial direction and a moment around each axis in an XYZ three-dimensional coordinate system, the force sensor including:
a closed loop shaped deformable body configured to generate elastic deformation by action of the force and the moment; and
a detection circuit configured to output an electric signal indicating the applied force and the moment on the basis of the elastic deformation generated in the deformable body,
in which the deformable body includes: at least two fixed portions fixed with respect to the XYZ three-dimensional coordinate system; at least two force receiving portions positioned adjacent to the fixed portions in a closed loop shaped path of the deformable body and configured to receive action of the force and the moment; and a deformable portion positioned between the fixed portion and the force receiving portion adjacent to each other in the closed loop shaped path,
the deformable portion includes:
a main curved portion including a main curved surface curved in the Z-axis direction;
a fixed portion-side curved portion connecting the main curved portion with the corresponding fixed portion and including a fixed portion-side curved surface curved in the Z-axis direction; and
a force receiving portion-side curved portion connecting the main curved portion with the corresponding force receiving portion and including a force receiving portion-side curved surface curved in the Z-axis direction,
the main curved surface and each of the fixed portion-side curved surface and the force receiving portion-side curved surface are provided on one of the positive side on the Z-axis and the negative side on the Z-axis of the deformable portion, the curved surfaces having mutually different curved directions, and
the detection circuit outputs the electric signal on the basis of the elastic deformation generated in the main curved portion.
This force sensor may have a configuration in which
the main curved surface, and the fixed portion-side curved surface and the force receiving portion-side curved surface are provided on the negative side on the Z-axis of the deformable portion,
the main curved surface is curved toward the negative side on the Z-axis, and
the fixed portion-side curved surface and the force receiving portion-side curved surface are curved toward the positive side on the Z-axis.
A force sensor according to a second aspect of the present invention detects at least one of a force in each axial direction and a moment around each axis in an XYZ three-dimensional coordinate system, the force sensor including:
a closed loop shaped deformable body configured to generate elastic deformation by action of the force and the moment; and
a detection circuit configured to output an electric signal indicating the applied force and the moment on the basis of the elastic deformation generated in the deformable body,
in which the deformable body includes: at least two fixed portions fixed with respect to the XYZ three-dimensional coordinate system; at least two force receiving portions positioned adjacent to the fixed portions in a closed loop shaped path of the deformable body and configured to receive action of the force and the moment; and a deformable portion positioned between the fixed portion and the force receiving portion adjacent to each other in the closed loop shaped path,
the deformable portion includes:
a main curved portion including a main curved surface curved toward the inside or outside of the closed loop shaped path;
a fixed portion-side curved portion connecting the main curved portion with the corresponding fixed portion and including a fixed portion-side curved surface curved toward the inside or outside of the closed loop shaped path; and a force receiving portion-side curved portion connecting
the main curved portion with the corresponding force receiving portion and including a force receiving portion-side curved surface curved toward the inside or outside of the closed loop shaped path,
the main curved surface and each of the fixed portion-side curved surface and the force receiving portion-side curved surface are provided on one of an inner peripheral surface and an outer peripheral surface of the deformable body, the curved surfaces having mutually different curved directions, and
the detection circuit outputs the electric signal on the basis of the elastic deformation generated in the main curved portion.
This force sensor may be configured to further include: a fixed body fixed with respect to the XYZ three-dimensional coordinate system; and
a force receiving body configured to move relative to the fixed body by the action of the force and the moment, and may have a configuration
in which the fixed body is connected to each of the fixed portions via a fixed body-side connecting member, and the force receiving body is connected to each of the force receiving portions via a force receiving body-side connecting member.
This force sensor may be configured to further include: a fixed body fixed with respect to the XYZ three-dimensional coordinate system; and
a force receiving body configured to move relative to the fixed body by the action of the force and the moment, and may have a configuration
in which the fixed body is integrally formed with each of the fixed portions, and
the force receiving body is integrally formed with each of the force receiving portions.
The deformable body may be arranged so as to surround an origin when viewed in the Z-axis direction, and
a through hole through which the Z-axis is inserted may be formed in each of the fixed body and the force receiving body.
The deformable body may have a circular shape or rectangular shape about an origin as a center, when viewed in the Z-axis direction.
A force sensor according to a third aspect of the present invention detects at least one of a force in each axial direction and a moment around each axis in an XYZ three-dimensional coordinate system, the force sensor including:
a fixed body fixed with respect to the XYZ three-dimensional coordinate system;
a closed loop shaped deformable body surrounding the Z-axis and configured to be connected to the fixed body to generate elastic deformation by action of the force and the moment;
a force receiving body connected to the deformable body and configured to move relative to the fixed body by the action of the force and the moment; and
a detection circuit configured to output an electric signal indicating the force and the moment applied to the force receiving body on the basis of the elastic deformation generated in the deformable body,
in which the deformable body includes: at least two fixed portions connected to the fixed body; at least two force receiving portions connected to the force receiving body and positioned adjacent to the fixed portions in a circumferential direction of the deformable body; and a deformable portion positioned between the fixed portion and the force receiving portion adjacent to each other,
the deformable portion includes:
a main curved portion including a main curved surface curved in the Z-axis direction;
a fixed portion-side curved portion connecting the main curved portion with the corresponding fixed portion and including a fixed portion-side curved surface curved in the Z-axis direction; and
a force receiving portion-side curved portion connecting the main curved portion with the corresponding force receiving portion and including a force receiving portion-side curved surface curved in the Z-axis direction,
the main curved surface and each of the fixed portion-side curved surface and the force receiving portion-side curved surface are provided on one of the positive side on the Z-axis and the negative side on the Z-axis, the curved surfaces having mutually different curved directions,
the detection circuit outputs the electric signal on the basis of the elastic deformation generated in the main curved portion,
the force receiving body includes a force receiving body surface facing one of the positive direction on the Z-axis and the negative direction on the Z-axis, the fixed body includes a fixed body surface facing one of
the positive direction on the Z-axis and the negative direction on the Z-axis, and
a distance from the deformable body to the force receiving body surface differs from a distance from the deformable body to the fixed body surface.
A force sensor according to a fourth aspect of the present invention detects at least one of a force in each axial direction and a moment around each axis in an XYZ three-dimensional coordinate system, the force sensor including:
a fixed body fixed with respect to the XYZ three-dimensional coordinate system;
a closed loop shaped deformable body surrounding the Z-axis and configured to be connected to the fixed body to generate elastic deformation by action of the force and the moment;
a force receiving body connected to the deformable body and configured to move relative to the fixed body by the actioin of the force and the moment; and
a detection circuit configured to output an electric signal indicating the force and the moment applied to the force receiving body on the basis of the elastic deformation generated in the deformable body,
in which the deformable body includes: at least two fixed portions connected to the fixed body; at least two force receiving portions connected to the force receiving body and positioned adjacent to the fixed portions in a circumferential direction of the deformable body; and a deformable portion positioned between the fixed portion and the force receiving portion adjacent to each other,
the deformable portion includes:
a main curved portion including a main curved surface curved toward the inside or outside of the closed loop shaped path;
a fixed portion-side curved portion connecting the main curved portion with the corresponding fixed portion and including a fixed portion-side curved surface curved toward the inside or outside of the closed loop shaped path; and
a force receiving portion-side curved portion connecting the main curved portion with the corresponding force receiving portion and including a force receiving portion-side curved surface curved toward the inside or outside of the closed loop shaped path,
the main curved surface and each of the fixed portion-side curved surface and the force receiving portion-side curved surface are provided on an inner peripheral surface or an outer peripheral surface of the deformable body, the curved surfaces having mutually different curved directions,
the detection circuit outputs the electric signal on the basis of the elastic deformation generated in the main curved portion,
the force receiving body includes a force receiving body surface facing one of the positive direction on the Z-axis and the negative direction on the Z-axis,
the fixed body includes a fixed body surface facing one of the positive direction on the Z-axis and the negative direction on the Z-axis, and
a distance from the deformable body to the force receiving body surface differs from a distance from the deformable body to the fixed body surface.
The force sensor according to the third and fourth aspects may have a configuration in which the force receiving body surface and the fixed body surface are parallel to the XY plane, and
a Z-coordinate value of the force receiving body surface differs from a Z-coordinate value of the fixed body surface.
The deformable body may surround one of the fixed body and the force receiving body, and
the other of the fixed body and the force receiving body may surround the deformable body.
Each of the fixed body, the force receiving body, and the deformable body may have a circular shape or a rectangular shape about the origin as a center, when viewed in the Z-axis direction.
The at least two fixed portions may be integrally formed with the fixed body, and
the at least two force receiving portions may be integrally formed with the force receiving body.
In each of the force sensor described above, the at least two force receiving portions and the at least two fixed portions may be each provided in the number of n (n is a natural number of 2 or more), being alternately positioned along the closed loop shaped path of the deformable body, and
the deformable portions may be provided in the number of 2n (n is a natural number of 2 or more) and each of the deformable portions may be arranged between the force receiving portion and the fixed portion adjacent to each other.
Moreover, in each of the force sensors described above, the detection circuit may include a displacement sensor arranged in the main curved portion and may output an electric signal indicating the applied force and the moment on the basis of a measurement value of the displacement sensor.
The displacement sensor may include a capacitive element having a displacement electrode arranged in the main curved portion and a fixed electrode arranged to face the displacement electrode and connected to the at least two fixed portions, and
the detection circuit may output an electric signal indicating the applied force and the moment on the basis of a variation amount of an electrostatic capacitance value of the capacitive element.
Alternatively, it is allowable to have a configuration in which
the at least two force receiving portions and the at least two fixed portions are provided in the number of two for each,
each of the fixed portions is arranged symmetrically with each other about the Y-axis at a site where the deformable body overlaps with the X-axis when viewed in the Z-axis direction,
each of the force receiving portions is arranged symmetrically about the X-axis at a site where the deformable body overlaps with the Y-axis when viewed in the Z-axis direction,
four deformable portions are provided, one each being arranged between the force receiving portion and the fixed portion adjacent to each other,
the displacement sensor includes four capacitive elements having four displacement electrodes each arranged at each of the main curved portions of each of the deformable portions and having four fixed electrodes each arranged to face each of the displacement electrodes and connected to each of the corresponding fixed portions,
each of the four capacitive elements is arranged at each of four sites at which the deformable body intersects the V-axis and the W-axis when viewed in the Z-axis direction, and
the detection circuit outputs an electric signal indicating the applied force and the moment on the basis of the variation amount of the electrostatic capacitance value of the four capacitive elements.
A deformable body-side support may be connected to each of the main curved portions of the deformable body, and
the displacement electrodes may be supported by the corresponding deformable body-side support.
A force sensor according to a fifth aspect of the present invention detects at least one of a force in each axial direction and a moment around each axis in an XYZ three-dimensional coordinate system, the force sensor including:
a closed loop shaped deformable body configured to generate elastic deformation by action of the force and the moment; and
a detection circuit configured to output an electric signal indicating the applied force and the moment on the basis of the elastic deformation generated in the deformable body,
in which the deformable body includes: four fixed portions fixed with respect to the XYZ three-dimensional coordinate system; four force receiving portions positioned adjacent to the fixed portions in a closed loop shaped path of the deformable body and configured to receive action of the force and the moment; and a deformable portion positioned between each of the fixed portions and each of the force receiving portions adjacent to each other in the closed loop shaped path, the deformable portion includes:
a main curved portion including a main curved surface
curved in the Z-axis direction;
a fixed portion-side curved portion connecting the main curved portion with the corresponding fixed portion and including a fixed portion-side curved surface curved in the Z-axis direction; and
a force receiving portion-side curved portion connecting the main curved portion with the corresponding force receiving portion and including a force receiving portion-side curved surface curved in the Z-axis direction,
the main curved surface and each of the fixed portion-side curved surface and the force receiving portion-side curved surface are provided on one of the positive side on the Z-axis and the negative side on the Z-axis of each of the deformable portions, the curved surfaces having mutually different curved directions, and
the detection circuit outputs the electric signal on the basis of the elastic deformation generated in the main curved portion.
A force sensor according to a sixth aspect of the present invention detects at least one of a force in each axial direction and a moment around each axis in an XYZ three-dimensional coordinate system, the force sensor including:
a detection circuit configured to output an electric signal indicating the applied force and the moment on the basis of the elastic deformation generated in the deformable body,
in which the deformable body includes: four fixed portions fixed with respect to the XYZ three-dimensional coordinate system; four force receiving portions positioned adjacent to the fixed portions in a closed loop shaped path of the deformable body and configured to receive action of the force and the moment; and a deformable portion positioned between the fixed portion and the force receiving portion adjacent to each other in the closed loop shaped path,
the deformable portion includes:
a main curved portion including a main curved surface curved toward the inside or outside of the closed loop shaped path;
a fixed portion-side curved portion connecting the main curved portion with the corresponding fixed portion and including a fixed portion-side curved surface curved toward the inside or outside of the closed loop shaped path; and
a force receiving portion-side curved portion connecting the main curved portion with the corresponding force receiving portion and including a force receiving portion-side curved surface curved toward the inside or outside of the closed loop shaped path,
the main curved surface and each of the fixed portion-side curved surface and the force receiving portion-side curved surface are provided on one of an inner peripheral surface and an outer peripheral surface of the deformable body, the curved surfaces having mutually different curved directions, and
the detection circuit outputs the electric signal on the basis of the elastic deformation generated in the main curved portion.
In each of the above force sensor according to the fifth and sixth aspects, the four force receiving portions and the four fixed portions may be alternately positioned along the closed loop shaped path of the deformable body, and
the deformable portions may be provided in the number of eight, each being arranged between the force receiving portion and the fixed portion adjacent to each other.
This force sensor may be configured to further include: a fixed body fixed with respect to the XYZ three-dimensional coordinate system; and
a force receiving body configured to move relative to the fixed body by the action of the force and the moment, and may have a configuration
in which the four fixed bodies are connected to the fixed portions via a fixed body-side connecting member, and the four force receiving portions are connected to the force receiving bodies via a force receiving body-side connecting member.
Alternatively, this force sensor may be configured to further include: a fixed body fixed with respect to the XYZ three-dimensional coordinate system; and
a force receiving body configured to move relative to the fixed body by the action of the force and the moment, and may have a configuration
in which the four fixed bodies are integrally formed with the fixed portions, and
the four force receiving bodies are integrally formed with the force receiving portions.
The closed loop shaped deformable body may have a circular shape or a rectangular shape.
The detection circuit may include a displacement sensor arranged in the main curved portion and may output an electric signal indicating the applied force and the moment on the basis of a measurement value of the displacement sensor.
The displacement sensor may include a capacitive element having a displacement electrode arranged in the main curved portion and a fixed electrode arranged to face the displacement electrode and connected to at least one of the four fixed portions, and
the detection circuit may output an electric signal indicating the applied force and the moment on the basis of a variation amount of the electrostatic capacitance value of the capacitive element.
It is allowable to have a configuration in which
two of the four force receiving portions are arranged symmetrically about an origin on the X-axis when viewed in the Z-axis direction,
the remaining two of the four force receiving portions are arranged symmetrically about the origin on the Y-axis when viewed in the Z-axis direction, and
in a case where the V-axis and W-axis passing through the origin and forming an angle of 45° with respect to the X-axis and the Y-axis are defined on the XY plane,
two of the four fixed portions are arranged symmetrically about the origin on the V-axis when viewed in the Z-axis direction, and
the remaining two of the four fixed portions are arranged symmetrically about the origin on the W-axis when viewed in the Z-axis direction,
the deformable portions are provided in the number of eight, each being arranged between the force receiving portion and the fixed portion adjacent to each other,
the displacement sensor includes eight capacitive elements having eight displacement electrodes each arranged at each of the main curved portions of each of the deformable portions and having eight fixed electrodes each arranged to face each of the displacement electrodes and connected to each of the corresponding fixed portions, and
the detection circuit outputs an electric signal indicating the applied force and the moment on the basis of the variation amount of the electrostatic capacitance value of the eight capacitive elements.
In each of the force sensors described above, the main curved surface of the main curved portion may be formed with a smooth curved surface having no inflection point when observed along the closed loop shaped path.
Alternatively, in each of the force sensors described above, the main curved surface of the main curved portion may be formed with a curved surface along an arc when observed along the closed loop shaped path.
Alternatively, in each of the force sensors described above, the main curved surface of the main curved portion may be configured by a curved surface along an arc of an ellipse when observed along the closed loop shaped path.
In each of the force sensors described above, the main curved portion may have a non-curved linear section in at least one end region when observed along the closed loop shaped path.
A force sensor according to a seventh aspect of the present invention detects at least one of a force in each axial direction and a moment around each axis in an XYZ three-dimensional coordinate system, the force sensor including:
a fixed body surrounding the Z-axis and fixed with respect to the XYZ three-dimensional coordinate system;
a closed loop shaped deformable body surrounding the Z-axis and connected to the fixed body and configured to generate elastic deformation by action of the force and the moment;
a force receiving body surrounding the Z-axis and connected to the deformable body, and configured to move relative to the fixed body by the action of the force and the moment; and
a detection circuit configured to output an electric signal indicating the force and the moment applied to the force receiving body on the basis of elastic deformation generated in the deformable body,
in which the deformable body includes: at least two fixed portions connected to the fixed body; at least two force receiving portions connected to the force receiving body and positioned adjacent to the fixed portion in a circumferential direction of the deformable body; and a deformable portion positioned between the fixed portion and the force receiving portion adjacent to each other,
the deformable portion includes a curved portion curved in a predetermined direction,
the detection circuit outputs the electric signal on the basis of elastic deformation generated in the curved portion,
the force receiving body includes a force receiving body surface facing one of the positive direction on the Z-axis and the negative direction on the Z-axis, and
the deformable body includes a deformable body surface facing the same direction as the force receiving body surface, with the Z-coordinate of the deformable body surface being different from the Z-coordinate of the force receiving body surface.
The fixed body may have a fixed body surface facing the same direction as the force receiving body surface, and the Z-coordinate of the fixed body surface may differ from the Z-coordinate of the deformable body surface and from the Z-coordinate of the force receiving body surface.
Alternatively, a force sensor according to an eighth aspect of the present invention detects at least one of a force in each axial direction and a moment around each axis in an XYZ three-dimensional coordinate system, the force sensor including:
a fixed body surrounding the Z-axis and fixed with respect to the XYZ three-dimensional coordinate system;
a closed loop shaped deformable body surrounding the Z-axis and connected to the fixed body, and configured to generate elastic deformation by action of the force and the moment;
a force receiving body surrounding the Z-axis and connected to the deformable body, and configured to move relative to the fixed body by the action of the force and the moment; and
a detection circuit configured to output an electric signal indicating the force and the moment applied to the force receiving body on the basis of elastic deformation generated in the deformable body,
in which the deformable body includes: at least two fixed portions connected to the fixed body; at least two force receiving portions connected to the force receiving body and positioned adjacent to the fixed portion in a circumferential direction of the deformable body; and a deformable portion positioned between the fixed portion and the force receiving portion adjacent to each other,
the deformable portion includes a curved portion curved in a predetermined direction,
the detection circuit outputs the electric signal on the basis of elastic deformation generated in the curved portion,
the fixed body includes a fixed body surface facing one of the positive direction on the Z-axis and the negative direction on the Z-axis, and
the deformable body includes a deformable body surface facing the same direction as the fixed body surface, with the Z-coordinate of the deformable body surface being different from the Z-coordinate of the fixed body surface.
In the above force sensor according to the seventh and eighth aspects, each of the fixed body, the force receiving body, and the deformable body may have a circular or rectangular shape about an origin as a center, when viewed in the Z-axis direction.
Moreover, the force receiving body and the fixed body may be arranged so as to sandwich the deformable body.
Alternatively, the force receiving body and the fixed body may be arranged on the same side with respect to the deformable body.
Moreover, it is allowable to have a configuration,
in which one of the fixed body and the force receiving body includes a sensor-side projection in a region facing an attachment object to which the force sensor is attached,
the sensor-side projection is accommodated in an attachment recess formed in the attachment object when the force sensor is attached to the attachment object, and
the sensor-side projection is pressed toward the inside of the attachment recess by an inner peripheral surface of the attachment recess.
Alternatively, it is allowable to have a configuration,
in which one of the fixed body and the force receiving body includes a sensor-side recess in a region facing an attachment object to which the force sensor is attached,
the sensor-side recess accommodates an attachment projection formed in the attachment object when the force sensor is attached to the attachment object, and
an inner peripheral surface of the sensor-side recess presses the attachment projection toward the inside of the sensor-side recess.
A force sensor according to a ninth aspect of the present invention is attached to an attachment object having an attachment recess and configured to detect at least one of a force in each axial direction and a moment around each axis in the XYZ three-dimensional coordinate system, the force sensor
a deformable body configured to generate elastic deformation by the action of the force and the moment;
a fixed body connected to the deformable body and fixed with respect to XYZ three-dimensional coordinates; and
a force receiving body connected to the deformable body and configured to move relative to the fixed body by the action of the force and the moment,
in which one of the fixed body and the force receiving body includes a sensor-side projection to be accommodated in the attachment recess, in a region facing the attachment object, and
the sensor-side projection is pressed toward the inside of the attachment recess by an inner peripheral surface of the attachment recess when the sensor-side projection is accommodated in the attachment recess.
An acute angle formed by an outer peripheral surface of the sensor-side projection with respect to an attachment direction when the force sensor according to the ninth aspect is attached to the attachment object may be smaller than an acute angle formed by the inner peripheral surface of the attachment recess with respect to the attachment direction.
The sensor-side projection may be provided to face each other with an interval when viewed in an attachment direction when the force sensor is attached to the attachment object, or may be provided continuously or intermittently along a closed loop shaped path.
A force sensor according to a tenth aspect of the present invention is attached to an attachment object having an attachment projection and configured to detect at least one of a force in each axial direction and a moment around each axis in the XYZ three-dimensional coordinate system, the force sensor including:
a deformable body configured to generate elastic deformation by action of the force and the moment;
a fixed body connected to the deformable body and fixed with respect to XYZ three-dimensional coordinates; and
a force receiving body connected to the deformable body and configured to move relative to the fixed body by the action of the force and the moment,
in which one of the fixed body and the force receiving body includes a sensor-side recess to be accommodated in the attachment projection, in a region facing the attachment object, and
an inner peripheral surface of the sensor-side recess presses the attachment projection toward the inside of the sensor-side recess when the sensor-side recess accommodates the attachment projection.
The acute angle formed by the inner peripheral surface of the sensor-side recess with respect to the attachment direction when the force sensor is attached to the attachment object may be greater than the acute angle formed by the outer peripheral surface of the attachment projection with respect to the attachment direction.
Moreover, the attachment projection is provided to face each other with an interval when viewed in an attachment direction when the force sensor is attached to the attachment object, or may be provided continuously or intermittently along a closed loop shaped path.
Note that a combination body including the force sensor according to the tenth aspect and
the attachment object to which the force sensor is attached is also within the scope of the present invention.
Alternatively, a force sensor according to an eleventh aspect of the present invention is attached to an attachment object having an attachment hole and configured to detect at least one of a force in each axial direction and a moment around each axis in an XYZ three-dimensional coordinate system, the force sensor including:
a deformable body configured to generate elastic deformation by action of the force and the moment;
a fixed body connected to the deformable body and fixed with respect to XYZ three-dimensional coordinates; and
a force receiving body connected to the deformable body and configured to move relative to the fixed body by the action of the force and the moment,
in which one of the fixed body and the force receiving body includes a through hole through which a fixture for attaching the force sensor to the attachment object passes,
an attachment object-side edge of the through hole includes a protrusion protruding toward the attachment object, and
the protrusion presses an edge of the attachment hole when the force sensor is attached to the attachment object.
In the force sensor according to the eleventh aspect described above, it is allowable to have a configuration in which
a cone-shaped attachment-side tapered surface is formed at the edge of the attachment hole,
a sensor-side tapered surface tapered toward the attachment object is formed on an outer peripheral surface of the protrusion,
the sensor-side tapered surface presses the attachment-side tapered surface when the force sensor is attached to the attachment object, and
an acute angle formed by the sensor-side tapered surface with respect to an attachment direction when the force sensor is attached to the attachment object is smaller than an acute angle formed by the attachment-side tapered surface with respect to the attachment direction.
Note that a combination body including the force sensor according to the eleventh aspect and the attachment object to which the force sensor is attached is also within the scope of the present invention.
Hereinafter, a force sensor according to a first embodiment of the present invention will be described in detail with reference to the accompanying drawings.
As illustrated in
In the basic structure 1 according to the present embodiment, a capacitive element is arranged at a predetermined position of a gap formed between the deformable body 40 and the fixed body 10, and functions as a force sensor by connecting a predetermined detection circuit 50 to the capacitive element. The detection circuit 50 is provided for measuring one or both of the applied force and the moment on the basis of a variation amount in the electrostatic capacitance value of the capacitive element. A specific arrangement mode of the capacitive element and a specific method applied to measure the applied force and the moment will be described below.
As illustrated in
As illustrated in
As illustrated in
As illustrated in
Next, each of the deformable portions 45 to 48 of the deformable body 40 will be described in detail with reference to
More specifically, as illustrated in
Furthermore, as illustrated in
In contrast, as illustrated in
With the above configuration, the second deformable portion 46 is formed to have a center of the closed loop shaped path from the second fixed portion 42 to the first force receiving portion 43 to be on the most toward the negative side on the Z-axis when observed along the path. As illustrated in
Furthermore, although not illustrated, the first, third and fourth deformable portions 45, 47, and 48 are also configured similarly to the second deformable portion 46. That is, each of the first, third and fourth deformable portions 45, 47, and 48 includes a fixed portion-side curved portion and a force receiving portion-side curved portion having the curvature as described above, and includes a main curved portion sandwiched between these portions. In each of the deformable portions 45, 47, and 48, first, third, and fourth measurement sites are defined at individual sites located on the most toward the negative side on the Z-axis when observed along the closed loop shaped path. As a result, as illustrated in
Next, application of the basic structure 1 will be described.
(1-2-1. Case where Moment Mx Around X-Axis is Applied to Basic Structure 1)
As illustrated in
At this time, as illustrated in
In
As a result, when the moment +Mx around the positive X-axis is applied to the force receiving body 20 of the basic structure 1, the separation distances between each of the first and second measurement sites A1 and A2 and the upper surface of the fixed body 10 (refer to
Although not illustrated, in a case where the moment −Mx around the negative X-axis is applied to the force receiving body 20 of the basic structure 1, the moving direction of each of the measurement sites A1 to A4 is opposite to the above-described direction. That is, due to the action of the moment −Mx around the negative X-axis, the separation distances between each of the first and second measurement sites A1 and A2 and the upper surface of the fixed body 10 (refer to
(1-2-2. Case where Moment My Around Y-Axis is Applied to Basic Structure 1)
As illustrated in
At this time, as illustrated in
Moreover, as illustrated in
Meanwhile, as illustrated in
As a result, when a moment +My around the positive Y-axis is applied to the force receiving body 20 of the basic structure 1, the separation distances between each of the first and fourth measurement sites A1 and A4 and the upper surface of the fixed body 10 (refer to
Although not illustrated, in a case where the moment −My around the negative Y-axis is applied to the force receiving body 20 of the basic structure 1, the moving direction of each of the measurement sites A1 to A4 is opposite to the above-described direction. That is, due to the action of the moment −My around the negative Y-axis, the separation distances between each of the first and fourth measurement sites A1 and A4 and the upper surface of the fixed body 10 (refer to
(1-2-3. Case where Moment Mz Around Z-Axis is Applied to Basic Structure 1)
As illustrated in
At this time, as illustrated in
Moreover, since the second force receiving portion 44 moves in the positive direction on the X-axis due to the force in the positive direction on the X-axis applied to the second force receiving portion 44, a tensile force along the X-axis direction is applied to the third deformable portion 47. As a result, a third main curved portion 47p elastically deforms so as to increase the radius of curvature while maintaining the Z-coordinate values of the both end portions. That is, the third measurement site A3 moves upward. Meanwhile, the movement of the second force receiving portion 44 in the positive direction on the X-axis causes a compressive force along the X-axis direction to be applied to the fourth deformable portion 48. As a result, a fourth main curved portion 48p elastically deforms so as to decrease the radius of curvature while maintaining the Z-coordinate values of the both end portions. That is, the fourth measurement site A4 moves downward.
As a result, when a moment +Mz around the positive Z-axis is applied to the force receiving body 20 of the basic structure 1, the separation distances between each of the first and third measurement sites A1 and A3 and the upper surface of the fixed body 10 both increase, and the separation distance between each of the second and fourth measurement sites A2 and A4 and the upper surface of the fixed body 10 (refer to
Although not illustrated, in a case where the moment −Mz around the negative Z-axis is applied to the force receiving body 20 of the basic structure 1, the moving direction of each of the measurement sites A1 to A4 is opposite to the above-described direction. That is, due to the action of the moment −Mz around the negative Z-axis, the separation distances between each of the first and third measurement sites A1 and A3 and the upper surface of the fixed body 10 both decrease, and the separation distance between each of the second and fourth measurement sites A2 and A4 and the upper surface of the fixed body 10 (refer to
(1-2-4. Case where Force Fz in Z Direction is Applied to Basic Structure 1)
As illustrated in
At this time, as illustrated in
As a result, when the force +Fz in the positive direction on the Z-axis is applied to the force receiving body 20 of the basic structure 1, the separation distance between the first to fourth measurement sites A1 to A4 and the upper surface of the fixed body 10 (refer to
Although not illustrated, in a case where the force −Fz in the negative direction on the Z-axis is applied to the force receiving body 20 of the basic structure 1, the moving direction of each of the measurement sites A1 to A4 is opposite to the above-described direction. That is, due to the action of the force −Fz in the negative direction on the Z-axis, the separation distance between each of the first to fourth measurement sites A1 to A4 and the upper surface of the fixed body 10 (refer to
(1-3-1. Configuration of Force Sensor)
The basic structure 1 described in detail in § 1-1 and § 1-2 can be suitably used as a capacitive element type force sensor 1c. Herein, this force sensor 1c will be described in detail below.
As illustrated in
Although not illustrated, the force sensor 1c includes a third displacement electrode Em3 arranged at the third measurement site A3 and a third fixed electrode Ef3 arranged to face the third displacement electrode Em3 and configured not to move relative to the fixed body 10, and also includes a fourth displacement electrode Em4 arranged at the fourth measurement site A4 and a fourth fixed electrode Ef4 arranged to face the fourth displacement electrode Em4 and configured not to move relative to the fixed body 10. The electrode Em3 and the electrode Ef3 constitute the third capacitive element C3, and the electrode Em4 and the electrode Ef4 constitute the fourth capacitive element C4.
Specifically, as illustrated in
Furthermore, as illustrated in
Note that in a case where the fixed body 10, the force receiving body 20, and the deformable body 40 are formed of a conductive material such as a metal, the first to fourth displacement substrates Im1 to Im4 and the first to fourth fixed substrates If1 to If4 need to be formed of an insulator so as to prevent short-circuit in each of the electrodes.
(1-3-2. Variation in Electrostatic Capacitance Value of Each of Capacitive Elements when Moment Mx Around X-Axis is Applied to Force Sensor 1c)
Next,
First, when the moment +Mx around the positive X-axis is applied to the force sensor 1c according to the present embodiment, as observed from the behaviors of the measurement sites A1 to A4 described in § 1-2-1, the separation distance between the electrodes constituting the first capacitive element C1 and the second capacitive element C2 both increase. Due to this, the electrostatic capacitance values of the first capacitive element C1 and the second capacitive element C2 both decrease. In contrast, the separation distance between the electrodes constituting the third capacitive element C3 and the fourth capacitive element C4 both decrease. Therefore, the electrostatic capacitance values of the third capacitive element C3 and the fourth capacitive element C4 both increase. The variation of the electrostatic capacitance value of each of the capacitive elements C1 to C4 is summarized in the column of “Mx” in
(1-3-3. Variation in Electrostatic Capacitance Value of Each of Capacitive Elements when Moment My Around the Y-Axis is Applied to Force Sensor 1c)
Next, when a moment +My around the positive Y-axis is applied to the force sensor 1c according to the present embodiment, as observed from the behaviors of the measurement sites A1 to A4 described in § 1-2-2, the separation distance between the electrodes constituting the first capacitive element C1 and the fourth capacitive element C4 both decrease. Therefore, the electrostatic capacitance values of the first capacitive element C1 and the fourth capacitive element C4 both increase. In contrast, the separation distance between the electrodes constituting the second capacitive element C2 and the third capacitive element C3 both increase. Therefore, the electrostatic capacitance values of the second capacitive element C2 and the third capacitive element C3 both decrease. The variation of the electrostatic capacitance value of each of the capacitive elements C1 to C4 is summarized in the column of “My” in
(1-3-4. Variation in Electrostatic Capacitance Value of Each of Capacitive Elements when Moment Mz Around the Z-Axis is Applied to Force Sensor Lc)
First, when a moment +Mz around the positive Z-axis is applied to the force sensor 1c according to the present embodiment, as observed from the behaviors of the measurement sites A1 to A4 described in § 1-2-3, the separation distance between the electrodes constituting the first capacitive element C1 and the third capacitive element C3 both increase. Therefore, the electrostatic capacitance values of the first capacitive element C1 and the third capacitive element C3 both decrease. In contrast, the separation distance between the electrodes constituting the second capacitive element C2 and the fourth capacitive element C4 both decrease. Therefore, the electrostatic capacitance values of the second capacitive element C2 and the fourth capacitive element C4 both increase. The variation of the electrostatic capacitance value of each of the capacitive elements C1 to C4 is summarized in the column of “Mz” in
(1-3-5. Variation in Electrostatic Capacitance Value of Each of Capacitive Elements when Force Fz in Z-Axis Direction is Applied to Force Sensor Lc)
Next, when the force+Fz about the positive direction on the Z-axis is applied to the force sensor 1c according to the present embodiment, as observed from the behaviors of the measurement sites A1 to A4 described in § 1-2-4, the separation distance between the electrodes constituting each of the capacitive elements C1 to C4 all increase. Therefore, the electrostatic capacitance values of the capacitive elements C1 to C4 all decrease. The variation of the electrostatic capacitance value of each of the capacitive elements C1 to C4 is summarized in the column of “Fz” in
(1-3-6. Calculation Method of Applied Force and Moment)
In View of the Variation of the Electrostatic Capacitance Values of the Capacitive Elements C1 to C4 as Described Above, the detection circuit 50 calculates the moments Mx, My, and Mz and the force Fz applied to the force sensor 1c using the following [Expression 1] calculate. In [Expression 1], symbols C1 to C4 indicate the variation amounts in electrostatic capacitance values of the first to fourth capacitive elements C1 to C4, respectively.
Mx=−C1−C2+C3+C4
My=C1−C2−C3+C4
Mz=−C1 +C2−C3+C4
Fz=−(C1+C2+C3+C4) [Expression 1]
In a case where the force and the moment applied to the force sensor 1c is in the negative direction, Mx, My, Mz and Fz on the left side may be substituted by −Mx, −My, −Mz and −Fz. In this case, however, the signs of C1 to C4 on the right side are also reversed, leading to measurement of the force and moment applied by [Expression 1] regardless of whether the applied force and moment are positive or negative.
According to the force sensor 1c of the present embodiment as described above, the fixed portion-side curved portions 45f to 48f and the force receiving portion-side curved portions 45m to 48m are respectively interposed between the main curved portions 45p to 48p and the adjacent portions, namely, the fixed portions 41 and 42 and the force receiving portions 43 and 44. With this configuration, it is possible to avoid stress concentration to the connecting portions between the main curved portions 45p to 48p and the adjacent portions, namely, the fixed portions 41 and 42 and the force receiving portions 43 and 44. Accordingly, with the present embodiment, it is possible to provide the highly reliable capacitance type force sensor 1c.
Moreover, the force sensor 1c further includes the fixed body 10 fixed with respect to the XYZ three-dimensional coordinate system and the force receiving body 20 configured to move relative to the fixed portions 41 and 42 by the action of one or both of a force and a moment, and the fixed portions 41 and 42 of the deformable body 40 are connected to the fixed body 10, while the force receiving portions 43 and 44 of the deformable body 40 are connected to the force receiving body 20. This makes it easy to apply the force and the moment to the deformable body 40.
In addition, since the fixed body 10 and the force receiving body 20 includes the through holes through which the Z-axis passes, it is possible to reduce the weight of the force sensor 1c and to enhance the flexibility in installation of the force sensor 1c.
In the force sensor 1c according to the present embodiment, in a case where the V-axis and the W-axis passing through the origin O and forming an angle of 45° with respect to the X-axis and the Y-axis are defined on the XY plane, the four sets of capacitive elements C1 to C4 are arranged at each of the four sites overlapping with the V-axis and the W-axis when viewed in the Z-axis direction. This results in arranging the capacitive elements C1 to C4 symmetrically about the X-axis and the Y-axis, the electrostatic capacitance values of the capacitive elements C1 to C4 vary with high symmetry. This makes it possible to measure the applied force and the moment on the basis of the variation amount in the electrostatic capacitance values of the capacitive elements C1 to C4 very easily.
In the above description, the four capacitive elements C1 to C4 have the individual fixed substrates If1 to If4 and individual fixed electrodes Ef1 to Ef4. Alternatively, however, it is allowable in another embodiment to configure the fixed substrate to be common to the four capacitive elements and configure to provide individual fixed electrodes on the fixed substrate. Alternatively, the fixed substrate and the fixed electrode may be configured to be common to the four capacitive elements. Even with such a configuration, it is possible to measure the force and the moment similarly to the above-described force sensor 1c. Note that these configurations are also available for each of the embodiments described below.
In addition, sensitivity of the force sensor 1c to the applied force and the moment changes with a change in the cross-sectional shape of the deformable body 40. Specific description will be given as follows. While the radial sectional shape of the deformable body 40 in the present embodiment is a square (refer to
Alternatively, the sensitivity to the applied force and the moment in the force sensor 1c also changes together with the radius of curvature (degree of curvature) of the main curved portions 45p to 48p. Specifically, decreasing the radius of curvature of the main curved portions 45p to 48p (increasing the degree of curvature) increases the sensitivity to the applied force and the moment. In contrast, increasing the radius of curvature of the main curved portions 45p to 48p (decreasing the degree of curvature) decreases the sensitivity to the applied force and the moment.
In consideration of the relationship between the cross-sectional shape of the deformable body 40 and the radius of curvature of the main curved portions 45p to 48p, and the sensitivity to the force and the moment as described above, it is possible to optimize the sensitivity of the force sensor 1c for the use environment. Of course, the above description also applies to each of embodiments described below.
Next, a force sensor 201c according to a second embodiment of the present invention will be described.
As illustrated in
As illustrated in
Together with the arrangement of the fixed body 210, the force receiving body 220, and the deformable body 40 as described above, the arrangement of the first to fourth connecting members 231 to 234 is also different from the case of the force sensor 1c according to the first embodiment. That is, as illustrated in
Although not illustrated, the force sensor 201c can be configured by arranging four capacitive elements in an arrangement similar to the force sensor 1c according to the first embodiment in the basic structure 201 as described above. Although a member for arranging the fixed electrode is not illustrated in
The force sensor 201c as described above can be suitably installed in a mechanism formed with a first member and a second member that move relative to each other, for example, a joint of a robot. That is, by coupling the fixed body 210 to the first member and coupling the force receiving body 220 to the second member, it is possible to arrange the force sensor 201c in a limited space in a mode of avoiding interference with other members.
The method for measuring the force and the moment applied to the force sensor 201c is similar to the method for the force sensor 1c according to the first embodiment, and thus, a detailed description thereof will be omitted here.
The basic structure 201 as described above includes the force receiving body 220, the deformable body 40, and the fixed body 210 being concentrically arranged along the XY plane. Therefore, each of components of the basic structures 201 and 202 can be integrally formed by cutting working. With this processing, the force sensor 201c without hysteresis can be provided.
Next, with reference to
While the annular deformable body 40 illustrated in
The deformable body 640 according to the present modification has a rectangular shape as a whole. Herein, as illustrated in
As illustrated in
As illustrated in
Furthermore, as illustrated in
Such a configuration is also adopted in the remaining three deformable portions 646, 647, and 648. That is, the second deformable portion 646 has a configuration in which the lowermost site of a second main curved portion 646p exists on the positive W-axis and has a symmetrical shape about the positive W-axis. The third deformable portion 647 has a configuration in which the lowermost site of a third main curved portion 647p exists on the negative V-axis and has a symmetrical shape about the negative V-axis. The fourth deformable portion 648 has a configuration in which the lowermost site of a fourth main curved portion 648p exists on the negative W-axis and has a symmetrical shape about the negative V-axis.
As illustrated in
Consequently, the deformable body 640 is a modification of the annular deformable body 40 of the force sensor 1c and 201c described in § 1 and § 2, in which simply the entire shape has been changed to a rectangular shape while substantially maintaining the structure of each of the deformable portions. Therefore, even when the annular deformable body 40 of the force sensor 1c and 201c is replaced with the deformable body 640 described above, it is possible to achieve operational effects similar to the cases of the force sensor 1c and 201c.
Next, a force sensor according to a third embodiment of the present invention will be described.
Specifically, as illustrated in
The first deformable portion 345A is arranged between the first force receiving portion 343a and the first fixed portion 341a in parallel with the Y-axis. The second deformable portion 345B is arranged between the first fixed portion 341a and the second force receiving portion 343b in parallel with the X-axis. The third deformable portion 345C is arranged between the second force receiving portion 343b and the second fixed portion 341b in parallel with the X-axis. The fourth deformable portion 345D is arranged between the second fixed portion 341b and the third force receiving portion 343c in parallel with the Y-axis. The fifth deformable portion 345E is arranged between the third force receiving portion 343c and the third fixed portion 341c in parallel with the Y-axis. The sixth deformable portion 345F is arranged between the third fixed portion 341c and the fourth force receiving portion 343d in parallel with the X-axis. The seventh deformable portion 345G is arranged between the fourth force receiving portion 343d and the fourth fixed portion 341d in parallel with the X-axis. The eighth deformable portion 345H is arranged between the fourth fixed portion 341d and the first force receiving portion 343a in parallel with the Y-axis. Specifically, the structure of each of the deformable portions 345A to 345H is a curved structure similar to each of the deformable portions 45 to 48 respectively in the first embodiment (refer to
The force receiving body 320 and the rectangular deformable body 340 are connected to each other in the four force receiving portions 343a to 343d of the rectangular deformable body 340 by four force receiving portion-side connecting members 332a to 332d. Specifically, the first force receiving portion-side connecting member 332a connects the first force receiving portion 343a of the rectangular deformable body 340 to the force receiving body 320, the second force receiving portion-side connecting member 332b connects the second force receiving portion 343b of the rectangular deformable body 340 to the force receiving body 320, the third force receiving portion-side connecting member 332c connects the third force receiving portion 343c of the rectangular deformable body 340 to the force receiving body 320, and the fourth force receiving portion-side connecting member 332d connects the fourth force receiving portion 343d of the rectangular deformable body 340 to the force receiving body 320. With the above configuration, the force and moment applied to the force receiving body 320 are reliably transmitted to the rectangular deformable body 340. In
Next, application of the basic structure 301 will be described.
(4-2-1. Case where Force +Fx in Positive Direction on X-Axis +Fx is Applied)
The force +Fx in the positive direction on the X-axis is applied to the force receiving portions 343a to 343d via the force receiving body 320, such that each of the force receiving portions 341a to 341d is displaced in the positive direction on the X-axis. As a result, the third deformable portion 345C and the sixth deformable portion 345F receive action of a compressive force. In this case, as observed from 1-2 above, the third deformable portion 345C and the sixth deformable portion 345F elastically deform so as to decrease the radius of curvature of each of curved portions 345Cp and 345Fp. Therefore, each of the detection points A3 and A6 is displaced in the negative direction on the Z-axis. Meanwhile, as illustrated in
Moreover, the two force receiving portions 343a and 343c located on the X-axis move in a direction (X-axis direction) orthogonal to an alignment direction (Y-axis direction) of the first, fourth, fifth, and eighth deformable portions 345A, 345D, 345E, and 345H. Therefore, there is substantially no displacement in the Z-axis direction at the detection points A1, A4, A5, and A8 corresponding to the four deformable portions 345A, 345D, 345E, and 345H, respectively.
The application of the basic structure 301 when the force +Fy in the positive direction on the Y-axis is applied to the force receiving portions 343a to 343d of the basic structure 301 corresponds to the application of the basic structure 301 when the force+Fx in the positive direction on the X-axis is applied while being rotated by 90° counterclockwise around the origin O as a center. Therefore, a detailed description thereof will be omitted here.
(4-2-2. Case where Force +Fz in Positive Direction on Z-Axis is Applied)
Next,
The force +Fz in the positive direction on the Z-axis is applied to the force receiving portions 343a to 343d via the force receiving body 320, such that each of the force receiving portions 343a to 343d is displaced in the positive direction on the Z-axis. As a result, as illustrated in
(4-2-3. Case where Moment +Mx Around Positive X-Axis is Applied)
Next,
When the moment +Mx around the positive X-axis is applied to the force receiving body 320, the second force receiving portion 343b located on the positive Y-axis is displaced in the positive direction on the Z-axis (front direction in
Furthermore, as illustrated in
The application of the basic structure 301 when the moment +My around the positive Y-axis is applied to the force receiving portions 343a to 343d of the basic structure 301 corresponds to the application in the case where the moment +Mx around the positive X-axis is applied while being rotated 90° counterclockwise about the origin O as a center. Therefore, a detailed description thereof will be omitted here.
(4-2-4. Case where the Moment Around the Positive Z-Axis +Mz is Applied)
Next,
When the moment +Mz around the positive Z-axis is applied to the force receiving body 320, displacement occurs as illustrated in
Meanwhile, as illustrated in
In a case where the forces and moments applied to the force receiving body 320 are in the negative direction or around the negative axis, the directions of the forces applied to the deformable portions 345A to 345H are reversed. Accordingly, the increase and decrease of the separation distance between the detection points A1 to A8 listed in
(4-3. Configuration of Force Sensor)
Next, a configuration of the force sensor 301c having the basic structure 301 described in 4-1 and 4-2 will be described.
As illustrated in
The specific configuration of the eight capacitive elements C1 to C8 is similar to the case of the first embodiment. That is, as illustrated in
Furthermore, although not illustrated in detail, the basic structure 301 has a configuration in which the first and fourth to eighth displacement electrodes Em1 and Em4 to Em8 are respectively provided for the first, fourth to eighth detection points A1 and A4 to A8, with the first and fourth to eighth fixed electrodes E1l and Ef4 to Ef8 being provided on the fixed body 310 so as to face these displacement electrodes Em1, Em4 to Em8, respectively. The displacement electrodes Em1, Em4 to Em8 and the fixed electrodes Ef1 and Ef4 to Ef8, facing each other respectively, constitute the first and fourth to eighth capacitive elements C1 and C4 to C8, respectively.
Specifically, as illustrated in
Furthermore, as illustrated in
Note that in a case where the fixed body 310, the force receiving body 320, and the deformable body 340 are formed of a conductive material such as a metal, the first to eighth displacement substrates Im1 to Im8 and the first to eighth fixed substrates If1 to If8 need to be formed of an insulator so as to prevent short-circuit in each of the electrodes. This point is similar to the case of the first embodiment.
Next, application of the force sensor 301c when the force Fx, Fy, and Fz in each of the axial directions and the moments Mx, My, and Mz around the each of the axes, in the XYZ three-dimensional coordinate system, are applied to the force sensor 301c will be described.
(4-4-1. Case where Force +Fx in the Positive Direction on X-Axis is Applied)
First, when the force +Fx in the positive direction on the X-axis is applied to the force sensor 301c, the separation distance between the electrodes increases in both the second and seventh capacitive elements C2 and C7, leading to a decrease in the electrostatic capacitance value as observed from the fields of +Fx in
(4-4-2. Case where Force +Fy in Positive Direction on Y-Axis is Applied)
Next, when the force +Fy in the positive direction on the Y-axis is applied to the force sensor 301c, the separation distance between the electrodes increases in both the fifth and eighth capacitive elements C5 and C8, leading to a decrease in the electrostatic capacitance value as observed from the fields of +Fy in
(4-4-3. Case where Force +Fz in Positive Direction on Z-Axis is Applied)
Next, when the force +Fz in the positive direction on the Z-axis is applied to the force sensor 301c, the separation distance between the electrodes increases in all the capacitive elements C1 to C8, leading to a decrease in the electrostatic capacitance value as observed from the fields of +Fz in
(4-4-4. Case where Moment +Mx Around Positive X-Axis is Applied)
Next, when the moment +Mx around the positive X-axis is applied to the force sensor 301c, the separation distance between the electrodes increases in each of the first to fourth capacitive elements C1 to C4, leading to a decrease in the electrostatic capacitance value as observed from the fields of +Mx in
(4-4-5. Case where Moment +My Around Positive Y-Axis is Applied)
Next, when the moment +My around the positive Y-axis is applied to the force sensor 301c, the separation distance between the electrodes increases in each of the first, second, seventh, and eighth capacitive elements C1, C2, C7, C8, leading to a decrease in the electrostatic capacitance value as observed from the fields of +My in
(4-4-6. Case where Moment +Mz Around Positive Z-Axis is Applied)
Next, when the moment +Mz around the positive Z-axis is applied to the force sensor 301c, the separation distance between the electrodes increases in each of the first, third, fifth, and seventh capacitive elements C1, C3, C5, and C7, leading to a decrease in the electrostatic capacitance value as observed from the fields of +Mz in
The increase or decrease of the electrostatic capacitance values of the capacitive elements C1 to C8 described above are summarized in
(4-4-7. Calculation Method of Applied Force and Moment)
In view of the variation of the electrostatic capacitance values of the capacitive elements C1 to C8 as described above, the detection circuit 350 calculates the forces Fx, Fy, and Fz and the moments Mx, My, and Mz, applied to the force sensor 301c, using the following [Expression 2]. In [Expression 2], symbols C1 to C8 indicate the variation amounts in electrostatic capacitance values of the first to eighth capacitive elements C1 to C8, respectively.
Fx=−C2+C3+C6−C7
Fy=C1+C4−C5−C8
Fz=−C1−C2−C3−C4−C5−C6−C7−C8
Mx=−C1−C2−C3−C4+C5+C6+C7+C8
My=−C1−C2+C3+C4+C5+C6−C7−C8
Mz=−C1+C2−C3+C4−C5+C6−C7+C8[Expression 2]
In a case where the force and the moment applied to the force sensor 301c are in the negative direction, Fx, Fy, Fz, Mx, My, and Mz on the left side may be substituted by −Fx, −Fy, −Fz, −Mx, −My, and −Mz. In this case, however, the signs of C1 to C4 on the right side are also reversed, leading to measurement of the force and moment applied by [Expression 2] regardless of whether the applied force and moment are positive or negative.
Note that with [Expression 2], the force Fz in the Z-axis direction is obtained by the sum of −C1 to −C8. For this reason, it is necessary to pay attention to the fact that the force Fz is susceptible to the influence of a temperature change and common mode noise in the use environment of the force sensor 301c.
Next, cross-axis sensitivity of the force sensor 301c according to the present embodiment will be described with reference to
The numbers given in the table of
In the absence of cross-axis sensitivity, all the cells other than the six cells located on a diagonal line from the upper left to the lower right in the table of
According to the force sensor 301c of the present embodiment as described above, the fixed portion-side curved portions 345Af to 345Hf and the force receiving portion-side curved portions 345Am to 345Hm are respectively interposed between the main curved portions 345Ap to 345Hp and the adjacent fixed portions 341a to 341d and the force receiving portions 343a to 343d. With this configuration, it is possible to avoid stress concentration to the connecting portions between the main curved portions 345Ap to 345Hp and the adjacent fixed portions 341a to 341d and the force receiving portions 343a to 343d. Accordingly, with the present embodiment, it is possible to provide the highly reliable capacitance type force sensor 301c.
In addition, the force sensor 301c according to the present embodiment can measure all six components of the forces Fx, Fy, and Fz in each of the axial directions and the moments Mx, My, and Mz around each of the axes, of the XYZ three-dimensional coordinate system. Furthermore, the force sensor 301c can detect five components except the force Fz in the Z-axis direction by the difference between the electrostatic capacitance values of the eight capacitive elements C1 to C8. That is, according to the present embodiment, it is possible to provide the force sensor 301c not easily influenced by a temperature change and common mode noise of the use environment in measuring the five components Fx, Fy, Mx, My, and Mz excluding the force Fz.
In addition, since the deformable body is provided as the rectangular deformable body 340 having a square shape symmetrical with respect to the X-axis and the Y-axis, the rectangular deformable body 340 is symmetrically deformed by the applied force and moment. This makes it easy to measure the applied force and the moment on the basis of the deformation.
In particular, the rectangular deformable body 340 is positioned on the XY plane to as to set the center of the body to match with the origin O of the XYZ three-dimensional coordinate system. Each of the four force receiving portions 343a to 343d is arranged at a midpoint of each of sides of the rectangular deformable body 340, and each of four fixed portions is arranged at each of vertexes of the rectangular deformable body 340. With such a symmetrical configuration, the capacitive elements C1 to C8 are arranged symmetrically with respect to the X-axis and the Y-axis, making it possible to extremely easily measure the applied force and moment on the basis of the variation amount of the electrostatic capacitance values of each of the capacitive elements C1 to C8.
Main curved surfaces 345Apa to 345Hpa of the main curved portions 345Ap to 345Hp are formed by curved surfaces along an arc when observed along a closed loop shaped rectangular path of the rectangular deformable body 340. This makes it possible to further stabilize the elastic deformation generated in the main curved portions 345Ap to 345Hp due to the force and the moment applied to the force sensor 301c.
Next, a force sensor according to a fourth embodiment of the present invention will be described.
As illustrated in
In addition, together with the adoption of the annular deformable body 440, each of the fixed body 410 and the force receiving body 420 is also configured to have an outline of the outer periphery as a circle having the origin O as a center. Note that, for the sake of convenience of explanation, illustration of the force receiving body 420 is omitted in
Next, application of the basic structure 401 will be described. As described above, the annular deformable body 440 can be regarded as a body obtained by curving each of the sides of the rectangular deformable body 340 according to the third embodiment. Therefore, the increase or decrease of the separation distance between each of the measurement sites A1 to A8 of the deformable portions 445A to 445H and the fixed body 410 when the forces Fx, Fy, and Fz in each of the axial directions and the moments Mx, My, and Mz around each of the axes, on the XYZ three-dimensional coordinate system are applied to the force receiving portions 443a to 443d of the annular deformable body 440 is substantially the same as the increase or decrease of the separation distance in the third embodiment.
Note that, due to the change in the shape of the deformable body from a rectangular shape to a circular shape, action of the force +Fx in the positive direction on the X-axis to the force receiving portions 443a to 443d via the force receiving body 420 results in observation of elastic deformation at the curved portions 445Ap, 445Dp, 445Ep, and 445Hp of the first, fourth, fifth, and eighth deformable portions 445A, 445D, 445E, and 445H, respectively. Specifically, the first and eighth deformable portions 445A, 445H are slightly compression-deformed, leading to displacement of the corresponding first and eighth measurement sites A1 and A8 in the negative direction on the Z-axis. In contrast, the fourth and fifth deformable portions 445D and 445E are slightly tensile-deformed, leading to displacement of the corresponding fourth and fifth measurement sites A4 and A5 in the positive direction on the Z-axis. Similarly, when a force +Fy in the positive direction on the Y-axis is applied to the force receiving portions 443a to 443d via the force receiving body 420, the sixth and seventh deformable portions 445F and 445G are slightly compression-deformed, leading to displacement of the corresponding sixth and seventh measurement sites A6 and A7 in the negative direction on the Z-axis. In contrast, the second and third deformable portions 445B and 445C are slightly tensile-deformed, leading to displacement of the corresponding second and third measurement sites A2 and A3 in the positive direction on the Z-axis. In the case where the other forces Fz and moments Mx, My, and Mz are applied, the displacement in the Z-axis direction generated in each of the measurement sites A1 to A8 is similar to the case of the third embodiment.
(5-3. Configuration of Force Sensor)
Next, a configuration of the force sensor 401c having the basic structure 401 described in 5-1 and 5-2 will be described.
As observed from the above description, the force sensor 401c behaves substantially similarly to the force sensor 301c according to the third embodiment toward the applied force and moment. In particular, in a case where the four components of the force Fz in the Z-axis direction, and the moments Mx, My, and Mz around each of the XYZ axes are applied to the force sensor 401c, variation of the electrostatic capacitance values of the capacitive elements C1 to C8 exhibits the same behavior as the case of the force sensor 301c according to the third embodiment.
In contrast, in a case where the forces Fx and Fy in the X- and Y-axis directions are applied corresponding to the difference in the shape of the deformable body, the variation of the electrostatic capacitance value of each of the capacitive elements C1 to C8 is slightly different from the case of the force sensor 301c according to the third embodiment. For example, when the force +Fx in the positive direction on the X-axis is applied to the force receiving body 420, each of the force receiving portions 443a to 443d of the annular deformable body 440 is displaced in the positive direction on the X-axis. At this time, with the displacement of the first force receiving portion 443a toward the center (origin O) of the annular deformable body 440, the first and eighth deformable portions 445A and 445H are slightly compressed in the radial direction of the annular deformable body 440. As a result, the first and eighth main curved portions 445Ap and 445Hp elastically deform to slightly decrease the radius of curvature, leading to a slight displacement of each of the corresponding detection points A1 and A8 in the negative direction on the Z-axis. Similarly, with the displacement of the third force receiving portion 443c so as to move away from the center (origin O) of the annular deformable body 440, the fourth and fifth deformable portions 445D and 445E are slightly pulled in the circumferential direction of the annular deformable body 440. As a result, the fourth and fifth main curved portions 445Dp and 445Ep elastically deform to slightly increase the radius of curvature, leading to slight displacement of the corresponding detection points A4 and A5 in the positive direction on the Z-axis.
In contrast, the elastic deformation generated in the remaining second, third, sixth and seventh deformable portions 445B, 445C, 445F, and 445G and the corresponding displacement of the measurement sites A2, A3, A6, and A7 are similar to the case of the third embodiment. The absolute values of the displacements of these measurement sites A2, A3, A6, and A7 are of course larger than the absolute values of the displacements of the measurement sites A1, A4, A5, and A8. In a case where a force in the negative direction on the X-axis is applied to the force receiving body 420 of the force sensor 401c, the direction of the force applied to each of the deformable portions 445A to 445H is reversed, resulting in a reversed direction of displacement of each of the detection points A1 to A8.
The case where the force Fy in the Y-axis direction is applied to the force receiving body 420 of the force sensor 401c corresponds to the case where the above-described force Fx in the X-axis direction is applied while being rotated 90° counterclockwise about the origin O as a center. Therefore, the force sensor 401c detects a slight displacement in the Z-axis direction also in the second, third, sixth and seventh measurement sites A2, A3, A6, and A7, at which no displacement is generated in a case where the force Fy in the Y-axis direction is applied to the force receiving body 320 of the force sensor 301c according to the third embodiment.
From the above, in the case of the force sensor 401c according to the present embodiment, with the action of the forces Fx, Fy, and Fz in each of the axial directions and the moments Mx, My, and Mz around each of the axes, in the XYZ three-dimensional coordinate system, the electrostatic capacitance values of the capacitive elements C1 to C8 respectively associated with the individual detection points A1 to A8 vary substantially similarly to the case of the third embodiment. Note that in the present embodiment, a slight displacement in the Z-axis direction is generated in the measurement sites A1, A4, A5, A8 when the force Fx in the X-axis direction is applied, leading to a slight variation in the electrostatic capacitance values of the capacitive elements C1, C4, C5, and C8. Similarly, a slight displacement in the Z-axis direction is generated in the measurement sites A2, A3, A6, A7 when the force Fy in the Y-axis direction is applied, leading to a slight variation in the electrostatic capacitance values of the capacitive elements C2, C3, C6, and C7.
The increase and decrease of the electrostatic capacitance values of the capacitive elements C1 to C8 described above are summarized in
In view of the variation of the electrostatic capacitance values of the capacitive elements C1 to C8 as described above, the detection circuit 450 calculates the forces Fx, Fy, and Fz and the moments Mx, My, and Mz, applied to the force sensor 401c, using the following [Expression 3]. In [Expression 3], symbols C1 to C8 indicate the variation amounts in electrostatic capacitance values of the first to eighth capacitive elements C1 to C8, respectively.
Fx=−C2+C3+C6−C7
Fy=+C4−C5−C8
Fz=−C1−C2−C3−C4−C5−C6−C7−C8
Mx=−C1−C2−C3−C4+C5+C6+C7+C8
My=−C1−C2+C3+C4+C5+C6−C7−C8
Mz=−C1+C2−C3+C4−C5+C6−C7+C8 [Expression 3]
Alternatively, the detection circuit 450 may calculate applied forces Fx, Fy, and Fz and the moments Mx, My, and Mz selectively using the capacitive elements labeled with the signs “++” and “−−” in
Fx=−C2+C3+C6−C7
Fy=C1+C4−C5−C8
Fz=−C1−C2−C3−C4−C5−C6−C7−C8
Mx=−C2−C3+C6+C7
My=−C1−C2+C3+C4+C5+C6−C7−C8
Mz=−C1+C2−C3+C4−C5+C6−C7+C8 [Expression 4]
This [Expression 3] is the same as [Expression 2] described in the third embodiment. As described above, the force sensor 401c includes the capacitive element in which the electrostatic capacitance value slightly varies when the forces Fx and Fy in the X- and Y-axis directions are applied, as indicated by the bracketed signs in
In a case where the force and the moment applied to the force sensor 401c is in the negative direction, Fx, Fy, Fz, Mx, My, and Mz on the left side may be substituted by −Fx, -Fy, −Fz, -Mx, −My, and −Mz. Note that since the force Fz in the Z-axis direction is obtained by the sum of −C1 to −C8, it is necessary to pay attention to the fact that the force Fz is susceptible to the influence of a temperature change and common mode noise in the use environment of the force sensor 301c. In addition, correction calculation for canceling the cross-axis sensitivity can employ a method similar to the method in the third embodiment. This makes it possible to reduce the influence of the cross-axis sensitivity to substantially zero, leading to achievement of a highly accurate force sensor 401c.
Even with the force sensor 401c according to the present embodiment as described above, it is possible to achieve operational effects similar to the case of the force sensor 301c according to the third embodiment.
Now, a method of correction calculation will be described in detail.
The electrostatic capacitance value of each of the capacitive elements C1 to C8 varies as illustrated in
Evaluation of cross-axis sensitivity of the force sensor 401c according to the present embodiment based on the numerical values illustrated in
The table of
In each of the force sensors described above, the deformable body 40 illustrated in
In the example illustrated in
Moreover, while a main curved surface 546pa of the main curved portion 546Ap is a curved surface along an arc having a radius r2 about a point O2 as a center similarly to
That is, the Z-axis negative-side surface of the deformable body 540A illustrated in
Note that the main curved portions 545Ap to 548Ap may be directly connected to the fixed portion-side curved portions 545Af to 548Af respectively without interposing the fixed portion-side linear portions 545Afs to 548Afs. Furthermore, the main curved portions 545Ap to 548Ap may be directly connected to the force receiving portion-side curved portions 545Am to 548Am respectively without interposing the force receiving portion-side linear portions 545Ams to 548Ams. An example of this is illustrated in
Even with the force sensor that adopts the deformable bodies 540A and 540B respectively illustrated in
While four or eight capacitive elements are arranged in each of the force sensors of § 1 to § 5, five to seven capacitive elements or nine or more capacitive elements may be arranged. In this case, it is also possible to provide application similar to the case of each of the above-described force sensors by outputting each of electric signals T1 to T3 in accordance with individual cases. In addition, while each of the force sensor of § 1 to § 5 has a configuration in which the fixed portions and the force receiving portions are all adjacent to each other, the present invention is not limited to such a mode. That is, some of the force receiving portions may be adjacent to each other, or some of the fixed portions may be adjacent to each other. In this case, however, it is necessary to provide at least one pair of the force receiving portion and the fixed portion adjacent to each other.
<First Modification>
In each of the force sensors described above, the main curved portion curved toward the negative side on the Z-axis and the fixed portion-side curved surface and the force receiving portion-side curved surface curved toward the positive side on the Z-axis are provided on the Z-axis negative-side surface of the deformable body. However, the present invention is not limited to this mode. For example, a main curved portion curved toward the positive side on the Z-axis, a fixed portion-side curved surface and a force receiving portion-side curved surface curved toward the negative side on the Z-axis may be provided on a Z-axis positive-side surface of the deformable body. In this case, the measurement sites A1 to A4 or A1 to A8 of each of the deformable bodies are defined on the positive side on the Z-axis of each of the main curved portion.
Alternatively, the deformable portion of the deformable body may be curved in the radial direction rather than the Z-axis direction. That is, the deformable body 40 illustrated in
Specifically, in a case where the main curved portion is curved radially toward the outside, the main curved surface, the fixed portion-side curved surface, and the force receiving portion-side curved surface are defined on the outer peripheral surface of the deformable body. At this time, the fixed portion-side curved surface and the force receiving portion-side curved surface may be curved radially toward the inside with respect to the closed loop shaped path. In this case, the measurement sites A1 to A4 or A1 to A8 of each of the deformable bodies are defined on the outer peripheral surface of the deformable body (radially outer surface of the main curved portion). Alternatively, in a case where the main curved portion is curved radially toward the inside, the main curved surface, the fixed portion-side curved surface, and the force receiving portion-side curved surface are defined on the inner peripheral surface of the deformable body. At this time, the fixed portion-side curved surface and the force receiving portion-side curved surface may be curved radially toward the outside with respect to the closed loop shaped path. In this case, the measurement sites A1 to A4 or A1 to A8 of each of the deformable bodies are defined on the inner peripheral surface of the deformable body (radially inner surface of the main curved portion).
<Second Modification>
Next, a modification in which the fixed body 10 and the force receiving body 20 illustrated in
In the example illustrated in
Also, as illustrated in
<Third Modification>
These modifications can also be adopted for the deformable body 40 illustrated in
Next, a devise for firmly attaching each of the above-described force sensors to the attachment object such as a robot will be described.
In each of the force sensors described above, a fixed body is coupled to a robot main body, for example, and an end effector such as a gripper is coupled to the force receiving body. With this configuration, a force or torque applied to the end effector is measured by the force sensor. The coupling of the force sensor with the robot main body and the end effector is typically implemented by fastening screws or bolts to two to four fastening portions provided on the force receiving body and the fixed body of the force sensor.
Meanwhile, each of the force sensors described above is suitably adopted for measuring one or both of the force and the torque (moment) of high load. This easily leads to a problem of hysteresis, for which countermeasures are critical. In particular, countermeasures for hysteresis are critical in the force Fx in the X-axis direction, the force Fy in the Y-axis direction, and the moment Mz around the Z-axis.
In order to avoid hysteresis, it is necessary to increase the fastening force of a fastening portion of the force sensor. This needs to increase the diameter of the bolt or increase the number of fastening portions. This case, however, leads to another problem of enlarged external dimension of the force sensor even though the problem of hysteresis is eliminated or reduced. In order to solve such a problem, a combination body 1000 is formed by the force sensor together with one or both of the robot main body and the end effector as illustrated in
As illustrated in
As illustrated in
The force sensor 101c is fixed to the attachment object 2 by a bolt 3 as a fixture. That is, the same number of bolts 3 as the through holes 110a are prepared, and these bolts 3 are inserted into the individual through holes 110a from the side opposite to the side where the attachment object 2 is present. Subsequently, each of the bolts 3 is screwed into the corresponding attachment hole 2a. In this process of screwing, the sensor-side projection 110p abuts the inner peripheral surface 2f of the attachment recess 2r. By further tightening the bolts 3 from this state, the sensor-side projection 110p is pressed by the inner peripheral surface 2f of the attachment recess 2r toward the inside of the attachment recess 2r, that is, toward the side on which the pair of projections forming the sensor-side projection 110p comes close to each other. With this pressing, the sensor-side projection 110p is elastically deformed (flexurally deformed) toward the inside of the attachment recess 2r. This elastic deformation of the sensor-side projection 110p is smoothly implemented by the relationship between the angle θ2 related to the inner peripheral surface 2f of the attachment recess 2r and the angle θ1 related to the outer peripheral surface 110f of the sensor-side projection 110p.
By further tightening the bolts 3, the sensor-side projection 110p further elastically deforms toward the inside of the inner peripheral surface 2f of the attachment recess 2r, so as to gradually reduce a gap between the force sensor 101c and the attachment object 2 to eventually reach zero. This completes attachment of the force sensor 101c to the attachment object 2. At this time, the outer peripheral surface 110f of the sensor-side projection 110p has substantially a same level of inclination as the inner peripheral surface 2f of the attachment recess 2r. As a result, due to a restoring force of the sensor-side projection 110p, a large force is applied between the sensor-side projection 110p and the attachment recess 2r.
By combining the force sensor 101c and the attachment object 2 to be configured as the above-described combination body 1000, the force sensor 101c can be firmly fixed without unsteadiness to the attachment object 2, and the problem of hysteresis is effectively eliminated or reduced. It is preferable, of course, that the above-described attachment mode is adopted also at a connecting site between a force receiving body (not illustrated) and an end effector.
Contrary to the above example, a sensor-side recess may be provided on the force sensor side and an attachment projection to be accommodated in the sensor-side recess may be provided on the attachment object side. In this case, a structure corresponding to the above-described sensor-side projection 110p may be adopted for the attachment projection and a structure corresponding to the above-described attachment recess 2r may be adopted for the sensor-side recess. In this case, like the above-described example, the force sensor can be firmly fixed without unsteadiness to the attachment object.
Moreover, the above description is an exemplary case where the sensor-side projection 110p is a pair of projections facing each other. The sensor-side protrusion 110p, however, is not limited to this example. For example, the attachment projections illustrated in
Furthermore, the attachment projections may be formed continuously or intermittently along various closed loop shaped paths having shapes such as a rectangle, a triangle, and a polygon.
Next, another example for eliminating or reducing the hysteresis problem will be described with reference to
Furthermore, the attachment object 2A constituting the combination body 1001 is chamfered at a force sensor 101Ac-side edge of the attachment hole 2Aa, so as to be formed into a cone-shaped attachment-side tapered surface 2At. An acute angle θ3 formed by the above-described sensor-side tapered surface 110At with respect to an attachment direction (Z-axis direction) when the force sensor 101Ac is attached to the attachment object 2A is smaller than an acute angle θ4 formed by the attachment-side tapered surface 2At with respect to the attachment direction. While the sensor-side tapered surface 110At need not be constant over the entire circumference of the edge of the through hole 110Aa, the acute angle formed with respect to the attachment direction is constantly formed to be smaller than the acute angle formed by the corresponding attachment-side tapered surface 2At with respect to the attachment direction. The other configuration of the combination body 1001 is the same as the case of the combination body 1000 illustrated in
This force sensor 101Ac is fixed to the attachment object 2A by a bolt 3 as a fixture. Specifically, the bolts 3 of the same number as the through holes 110Aa are prepared, and these bolts 3 are inserted into the through holes 110Aa from the side opposite to the side where the attachment object 2A is present. Subsequently, each of the bolts 3 is screwed into the corresponding attachment hole 2Aa. In the process of screwing, the sensor-side tapered surface 110At comes in contact with the attachment-side tapered surface 2At. By further tightening the bolts 3 from this state, the protrusion 110Ap presses the edge of the attachment hole 2Aa, that is, the attachment-side tapered surface 2At. In other words, the protrusion 110Ap is pressed toward the inside of the attachment hole 2Aa by the attachment-side tapered surface 2At. With this pressing, the protrusion 110Ap is elastically deformed (flexurally deformed) toward the inside of the attachment hole 2Aa. This elastic deformation of the protrusion 110Ap is smoothly implemented by the magnitude relation between the acute angle θ3 with respect to the sensor-side tapered surface 110At and the acute angle θ4 with respect to the attachment-side tapered surface 2At.
By further tightening the bolts 3, the protrusion 110Ap further elastically deforms toward the inside of the attachment hole 2Aa, so as to gradually reduce a gap between the force sensor 101Ac and the attachment object 2A to eventually reach zero. This completes attachment of the force sensor 101Ac to the attachment object 2A. At this time, the sensor-side tapered surface 110At of the protrusion 110Ap has substantially the same level of inclination as the attachment-side tapered surface 2At. As a result, due to a restoring force of the protrusion 110Ap, a large force is applied between the sensor-side tapered surface 110At and the attachment-side tapered surface 2At.
By combining the force sensor 101Ac and the attachment object 2A to be configured as the above-described combination body 1001, the force sensor 101Ac can be firmly fixed without unsteadiness to the attachment object 2A, and the problem of hysteresis is effectively eliminated or reduced. It is preferable, of course, that the above-described attachment mode is adopted also at a connecting site between a force receiving body (not illustrated) and an end effector.
Next, an example of a method of manufacturing a deformable body will be described with reference to
First, as illustrated in
Next, as illustrated in
While the above description is the method of forming the second deformable portion 46, by forming the first, third, and fourth deformable portions 45, 47, and 48 in a similar manner, it is possible to easily manufacture the deformable body 40. Furthermore, this manufacturing method can be adopted in the above-described deformable body of each of the force sensors. In this case, the manufacturing method can be appropriately modified in accordance with the shape of each of the deformable bodies. For example, the deformable body having the main curved surface, the fixed portion-side curved surface, and the force receiving portion-side curved surface, curved in radially inner or radially outer direction of the deformable body described in § 6 has a configuration in which the above-described through holes H1 and H2 are formed in a direction parallel to the Z-axis. Furthermore, the deformable body in which the main curved surface, the fixed portion-side curved surface, and the force receiving portion-side curved surface are provided on the positive side on the Z-axis, that is, the deformable body in which the main curved surface is curved toward the positive side on the Z-axis and the fixed portion-side curved surface and the force receiving portion-side curved surface are curved toward the negative side on the Z-axis has a configuration of the above-described through holes H1 and H2, in which the Z-axis negative-side curved surface of the through hole H1 formed in the connecting portion between the second deformable portion 46 and the fixed portion 42 constitutes the fixed portion-side curved surface 46fa, and the Z-axis negative-side curved surface of the through hole H2 formed in the connecting portion between the second deformable portion 46 and the force receiving portion 43 constitutes the force receiving portion-side curved surface 46ma. Accordingly, the Z-axis negative-side portion of the through hole H1 becomes the fixed portion-side curved portion 46f, and the Z-axis negative-side portion of the through hole H2 becomes the force receiving portion-side curved portion 46m.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2018/004518 | 2/9/2018 | WO | 00 |
