Patent Application
20220203549
The present invention relates to a suction pad and a deformation measuring device.
A known industrial robot may include a robotic arm including multiple arm components. For example, Patent Literature 1 describes a robotic hand (robotic arm) for gripping a transport-target object. The robotic hand is included in a transport robot that transports a transport-target object. The robotic hand includes a hand unit with multiple bellows suction pads that are axially extendable under an elastic force to suction a transport-target object under vacuum pressure, and an axial-dimension sensor for measuring the axial dimension of each bellows suction pad that is suctioning the object.
Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2011-107011
With the above known technique, the axial-dimension sensor included in the robotic hand detects a transport-target object but does not detect a deformation of each suction pad. This structure may fail to precisely determine whether each suction pad is suctioning the transport-target object. Further, the suction pads described in Patent Literature 1 may not allow measurement of their deformations for controlling the movement of the robotic hand in accordance with the changing deformations of the suction pads.
In response to this, one or more aspects of the present invention are directed to a suction pad that allows measurement of its deformation.
In response to the above issue, the suction pad according to one or more aspects of the present invention has the structure described below.
A suction pad according to one aspect of the present disclosure is a suction pad for suctioning an object under a negative pressure. The suction pad includes a stationary section fixable on a support, and a deformable section deformable under the negative pressure. The deformable section includes a plurality of marks at a plurality of positions spaced from one another and displaceable with respect to the stationary section in response to deformation of the deformable section. The plurality of marks are optically identifiable. The plurality of marks are continuous across the plurality of positions or are separate at the plurality of positions.
The above structure allows measurement of the loading force and the tilting of the suction pad as the deformations of the suction pad, and allows precise detection of whether the suction pad is in contact with the object.
In the suction pad according to the above aspect, the plurality of marks may include a lattice pattern.
The above structure allows more detailed measurement of the deformations of the suction pad, and allows more precise detection of whether the suction pad is in contact with the object.
In the suction pad according to the above aspect, the plurality of marks may include a plurality of markers at the plurality of positions on the deformable section viewable from one viewpoint.
The above structure allows more precise measurement of the deformations of the suction pad, and allows precise detection of whether the suction pad is in contact with the object.
In the suction pad according to the above aspect, the plurality of marks may include a plurality of markers at three or more positions spaced from one another on the deformable section as viewed in a lateral direction of the suction pad.
The above structure allows measurement of the tilting of the suction pad in the two directions in addition to the loading force of the suction pad as the deformations of the suction pad, and allows precise detection of whether the suction pad is in contact with the object.
In the suction pad according to the above aspect, the plurality of marks may be adjacent to a part of the deformable section to be in contact with the object.
The above structure includes the marks close to the area of contact between the suction pad and the object with larger deformations of the suction pad, and thus facilitates detection of the deformations.
In the suction pad according to the above aspect, the deformable section may have a bellows shape.
The above structure facilitates detection of the deformations and improves the precision of measurement performed by the deformation measuring device including the suction pad.
In the suction pad according to the above aspect, the plurality of marks may include a retroreflective material.
The above structure facilitates detection of the deformations and improves the precision of measurement performed by the deformation measuring device including the suction pad.
A deformation measuring device according to another aspect of the present disclosure is a deformation measuring device including the suction pad, an image obtainer that obtains image data by capturing an image of the deformable section, a feature point specifier that specifies, based on the plurality of marks included in the image data, a plurality of feature points included in the image data corresponding to the plurality of positions on the deformable section, and a deformation determiner that determines a deformation at each of the plurality of positions on the deformable section based on the plurality of feature points.
The above structure can determine the deformations of the suction pad, and allows precise determination of whether the suction pad is suctioning the object.
The deformation measuring device may further include an imaging device installable lateral to the suction pad. The imaging device may capture an image of the deformable section.
The above structure specifies the feature points from the image data obtained by capturing the deformable section of the suction pad, and can determine the deformation of the deformable section.
The suction pad according to the above aspects of the present invention allows measurement of its deformation.
One or more embodiments of the present invention (hereafter, the present embodiment) will now be described with reference to the drawings.
As shown in
The suction pad 112 includes such optically identifiable marks on the deformable section to measure three-dimensional (3D) deformation behavior of the suction pad 112. The optically identifiable marks at multiple positions spaced from one another and displaceable with respect to the stationary section 117 in response to deformation of the deformable section (hereafter, at multiple positions on the deformable section 118) allow detection of the deformations of the suction pad 112. The deformations of the suction pad 112 can be used to precisely detect whether the suction pad 112 is in contact with an object. The deformations of the suction pad 112 with any shape and formed from any material can be measured. Defining Deformations of Suction Pad 112
The deformations of the suction pad 112 will be defined with reference to
The definition 1 for the deformations of the suction pad 112 will first be described with reference to
As shown in
The definition 2 for the deformations of the suction pad 112 will be described with reference to
A vector P connects the center of the suctioning surface of the undeformed suction pad 112 and the center of the suctioning surface of the suction pad 112 being deformed. The suction pad 112 being deformed has a unit normal vector N. In the definition 2, the projection of the vector N to the X-axis is the projection ex, the projection of the vector N to the Y-axis is the projection ey, and the projection of the vector P to the Z-axis is the projection ez. In the definition 2, the vector N has the X-axis component ex and the Y-axis component ey, and the vector P has the Z-axis component ez. In the definition 2, the deformations of the suction pad 112 are represented by {ex, ey, ez}.
For the definitions 1 and 2, an equivalent volume of information is obtained as the deformation of the suction pad 112.
2. Structure
Suction Pad
In the example of
In the example of
A largely deformable part of the deformable section 118, such as a part close to the suctioning surface, may have marks for easier detection of the deformations. The deformable section 118 may have marks adjacent to an area of contact between the deformable section 118 and an object.
Loading force=(dI+dr)/2 (1)
Tilt=W1×(dl−dr)/2 (2)
In Formula 2, W1 is a constant determined through calibration (described later).
Tilt=W2×(dc−(dI+dr)/2) (3)
In Formula 3, W2 is a constant determined through calibration (described later).
In the example of
In the example of
The imaging device 121 captures an image of the deformable section 118 of the suction pad 112. The image data may be monochrome or colored. In the example of
The image obtainer 120 obtains image data generated through image capturing performed by the imaging device 121. The image data is then input into the feature point specifier 123.
The feature point specifier 123 specifies feature points expressing the deformable section 118 included in the image data input from the image obtainer 120. In the example of
The deformation determiner 124 determines deformations at multiple positions on the deformable section 118 (and thus the deformations of the suction pad) based on the feature points (coordinate values) output from the feature point specifier 123 and the coordinates for the stationary section 117. A function that specifies (predicts) and returns a deformation against an input feature point is referred to as a predictive model for predicting the deformations of the suction pad. The predictive model may be a white box model using a-priori information such as the mechanism of or the material for the suction pad 112 or may be a black box model using approximation of a nonlinear input-output system, such as a neural network.
To allow precise deformation determination using the predictive model for the deformations of the suction pad, the parameters for the predictive model may be adjusted (calibrated). The parameters resulting from such calibration are referred to as calibrated parameters. The calibration may be referred to as the calibration for the deformation measuring device. The calibration process will be described later.
The manipulator controller 13 determines the operation of the manipulator 111 based on the deformations determined by the deformation determiner 124. The manipulator controller 13 then controls the manipulator 111 to perform the determined operation.
The manipulator 111 is driven together with the suction pad 112 in the robotic arm 11 as controlled by the manipulator controller 13.
A suction transport apparatus 100 including the deformation measuring device according to the present embodiment will now be described with reference to
The deformation information obtainer 113 obtains information about the deformation behavior of the suction pad 112. For example, the deformation information obtainer 113 obtains data indicating distortion of the suction pad 112 from a torsion sensor 114. The deformation information obtainer 113 determines the deformations of the suction pad 112 based on data indicating the distortion. Specific examples of the distortion will be described later.
The deformation information obtainer 113 may obtain, from the torsion sensor 114, information about the deformations, the deformation speed, or the acceleration of deformation as information about such distortion behavior. In this case, the torsion sensor 114 performs the processing for obtaining the deformations, the deformation speed, or the acceleration of deformation.
The deformation information obtainer 113 may obtain, from multiple torsion sensors, information about deformation behavior at multiple positions on the suction pad 112. In the present embodiment, the deformation information obtainer 113 may have any structure that can obtain information about the deformation behavior of the suction pad 112. In the present embodiment, the deformation information obtainer 113 may obtain, for example, information about deformation behavior from one or more sensors installed on or incorporated in the suction pad 112. The sensor(s) installed on or incorporated in the suction pad 112 facilitate detection of the deformation behavior of the suction pad 112. The sensor(s) may be incorporated in the suction pad 112 at positions corresponding to the torsion sensor 114. The sensor(s) to be incorporated in the suction pad 112 may be, for example, distortion gauge sensors or pressure-sensitive conductive sensors formed from rubber or resin containing a conductive material, such as carbon nanotubes or a carbon resin.
The deformation information obtainer 113 may obtain information about deformation behavior from one or more optical displacement gauges (range sensors such as laser displacement sensors) or shape measurement sensors, instead of the torsion sensor 114. Similarly to the torsion sensor(s) 114, for example, one or more optical displacement gauges or shape measurement sensors may be installed on the suction pad 112. The optical displacement gauges or the shape measurement sensors can detect the deformation behavior (shape changes) of the suction pad 112 by detecting light reflected from the suction pad 112 and measuring the displacement of the suction pad 112. In particular, a single two-dimensional (2D) shape measurement sensor in the suction pad 112 can detect deformation behavior at multiple positions on the suction pad 112. The optical displacement gauge(s) may be, for example, short-range displacement sensors that are inexpensive. The shape measurement sensor(s) may be, for example, 2D shape measurement sensors that are smart sensors.
In some embodiments, the deformation information obtainer 113 may include a proximity sensor instead of the torsion sensor 114. For example, the deformation information obtainer 113 may include one or more proximity sensors on the suction pad 112, similarly to the torsion sensor(s) 114. The proximity sensor(s) can measure the displacement in the distance between the proximity sensor(s) and the suction pad 112 to detect the deformation behavior (shape changes) of the suction pad 112. The proximity sensors may be, for example, ultrasonic sensors, induction proximity sensors, capacitance proximity sensors, or optical proximity sensors.
The deformation information obtainer 113 outputs deformation data including the deformations of the suction pad 112, the deformation speed, and the acceleration of deformation to the manipulator controller 13 and a negative pressure controller 21. Abnormality Determiner
An abnormality determiner 115 may determine that an object is being suctioned by the suction pad 112 in response to the deformation(s) of the suction pad 112 being a predetermined amount or more in a predetermined period after the suction pad 112 stops suctioning (vacuuming) the object and releasing the object. In other words, the abnormality determiner 115 may determine that the object is being suctioned by the suction pad 112 in response to the deformation(s) of the suction pad 112 being a predetermined amount or more in a predetermined period after the vacuum disappears between the suction pad 112 and the object (after the vacuum breaks).
In this case, the abnormality determiner 115 may generate an alert or may cause the suction pad 112 to perform an operation to drop the object (to place the object). This prevents a failure in the placement operation due to, for example, the object remaining on the suction pad 112 after the vacuum breaks.
The vacuum pump 12 generates a negative pressure in accordance with its drive amount, and provides the negative pressure to the suction pad 112. In the example described below, the deformation measuring device 1 in the suction transport apparatus 100 includes the vacuum pump 12. In the present embodiment, the vacuum pump 12 may not be included in the deformation measuring device 1 in the suction transport apparatus 100 but may be external to the deformation measuring device 1 and the suction transport apparatus 100. In this case, the negative pressure controller 21 controls the drive amount of the vacuum pump 12 to allow this structure to produce the same advantageous effects as described in the above embodiment.
The operation controller 13 includes, for example, a central processing unit (CPU), a random-access memory (RAM), or a read-only memory (ROM). The operation controller 13 performs control in accordance with intended information processing. The manipulator controller 13 controls the manipulator 111 in the robotic arm 11 based on manipulator control signals output from the negative pressure controller 21. The manipulator controller 13 thus controls the manipulator 111 that then moves the suction pad 112. More specifically, the manipulator controller 13 drives the manipulator 111 to cause the suction pad 112 in the robotic arm 11 to be at the work position to suction an object. After the suction pad 112 moves to the work position, the manipulator controller 13 may control the manipulator 111 to cause the suction pad 112 to be at a predetermined angle with the object. This precisely aligns the suction pad 112 at an intended position. Once the suction pad 112 suctions the object, the manipulator controller 13 may drive the manipulator 111 to cause the suction pad 112 in the robotic arm 11 to be in a predetermined box (not shown) installed in an upper portion of the manipulator controller 13.
The manipulator controller 13 may determine the direction in which the suction pad 112 is to move and cause suctioning of the object again based on the deformations of the suction pad 112 at multiple positions.
To prevent the suction transport apparatus 100 in operation from being stopped at varying positions in an operation of picking (or suctioning) an object with the suction pad 112, the suction transport apparatus 100 measures the positional relationship between the apparatus and the object using 2D vision or 3D vision. In this case, for example, errors in measuring the positional relationship between the object and the suction transport apparatus 100 may cause the suction pad 112 to perform an erroneous operation for picking the object.
In response to this, the above structure can move the suction pad 112 not in full contact with the object in a direction to cause the suction pad 112 to suction the object again. This structure prevents the suction pad 112 from performing an erroneous operation for picking the object.
When the suction pad 112 undergoes a larger deformation at a first position than at a second position among other positions of the suction pad 112, the manipulator controller 13 may move the suction pad 112 toward the first position away from the second position (opposite to the position at which the sensor for measuring a smaller deformation is located) to cause suctioning of the object again. This prevents the suction pad 112 from deviating from the suction position. The suction pad 112 is thus less likely to perform an erroneous operation for picking the object.
The operation controller 13 may further include a contact point determiner 131. The contact point determiner 131 determines the point of contact between the suction pad 112 and the object based on the deformation behavior of the suction pad 112 (the deformations, the deformation speed, or the acceleration of deformation). The contact point determiner 131 also determines the point of contact between the object and a placement target surface while the suction pad 112 is suctioning the object based on the deformation behavior of the suction pad 112 (the deformations, the deformation speed, or the acceleration of deformation). The operation controller 13 causes the manipulator 111 to move the suction section (suction pad) 112 toward the suctioning surface with reference to the point of contact determined by the contact point determiner 131 to accommodate any errors in measuring the positional and orientational relationship between the object and the suction transport apparatus 100.
The suction section 112 is still less likely to perform an erroneous operation for picking the object.
The transporter (unmanned carrier) 2 includes the negative pressure controller (control signal output unit) 21 and an unmanned carrier 22.
The negative pressure controller 21 includes, for example, a CPU, a RAM, or a ROM. The negative pressure controller 21 performs control in accordance with intended information processing. The negative pressure controller 21 includes, for example, a programmable logic controller (PLC) or a microcomputer. The negative pressure controller 21 controls the vacuum pump 12 that generates a negative pressure based on output signals received from one or more torsion sensors 114 included in the deformation information obtainer 113 and based on transport state signals received from a transport controller 221 included in the unmanned carrier 22.
The negative pressure controller 21 controls the on and off states of the vacuum pump 12 based on signals from the operation controller 13. For picking an object, for example, the negative pressure controller 21 turns on the vacuum pump in response to a determination that the suction pad 112 has sufficiently loaded the object based on the deformation behavior of the suction pad 112. For placing an object on a platform, the negative pressure controller 21 turns off the vacuum pump when the operation controller 13 determines that the entire bottom of the object is in contact with the placement target surface of the platform.
The negative pressure controller 21 outputs, to the manipulator controller 13, manipulator control signals for controlling the manipulator 111.
The negative pressure controller 21 may include an analogue signal output unit 211 that outputs an analogue signal as a control signal for the vacuum pump 12. The analogue signal output unit 211 may perform control that allows a monotonic increase or a monotonic decrease in an output analogue signal. This allows the drive amount of the vacuum pump 12 to change with a gradient, thus reducing an inrush current and consumption power and allowing stable control.
In the example of
The battery 3 supplies power to the components of the suction transport apparatus 100, or more specifically, the deformation measuring device 1 and the transporter 2, to control the components of the suction transport apparatus 100.
Although the suction transport apparatus 100 operates on the battery 3 in the above example, the present embodiment is not limited to this example. In the present embodiment, the suction transport apparatus 100 may supply power externally through a power supply cord.
A controller 5 includes the deformation information obtainer 113, which obtains information about the deformation behavior of the suction pad 112, and the operation controller 13, which controls the movement of the suction pad 112 in accordance with the deformation behavior of the suction pad 112. More specifically, the operation controller 13 changes the movement (at least one of the direction of movement, the speed, or the tilting) of the suction pad 112 in accordance with the deformation behavior of the suction pad 112.
The controller 5 further includes an object information obtainer 14, which obtains information about an object, and a placement information obtainer 15, which obtains information about a platform onto which an object is to be placed.
The controller 5 may be included in the suction transport apparatus 100, or may be provided separate from the suction transport apparatus. For example, the controller 5 may communicate with the suction transport apparatus and may transmit, to the suction transport apparatus, control signals for controlling the suction transport apparatus.
The processes performed in the present embodiment will now be described with reference to
In step S01, a human or a robot loads the suction pad 112 by a predetermined amount in Z-direction. In step S02, the loading force Z and the feature points resulting from the processing in step SO1 are recorded.
In step S03, a human or a robot tilts the suction pad 112 by a predetermined amount about the X-axis. In step SO4, the rotational amount (tilt) Mx indicating the tilting resulting from the processing in step S03 and the feature points are recorded.
In step S05, a human or a robot tilts the suction pad 112 by a predetermined amount about the Y-axis. In step S06, the rotational amount (tilt) My indicating the tilting resulting from the processing in step S05 and the feature points are recorded.
In step S07, calibration parameters are generated based on the recorded deformations (the loading force Z and the tilts Mx and My) and the recorded feature points. For example, the calibration parameters of the predictive model can be determined by adjusting the parameters for the predictive model to reduce the error between each recorded deformation and the corresponding data output from the predictive model in response to input displacement of the feature point obtained based on the reference coordinates and the feature point coordinates. For a predictive model as a white box model using a-priori information such as the mechanism of or the material for the suction pad 112, the calibration parameters can be determined through fitting that minimizes the squared error between a deformation output by the predictive model and a real deformation. For a predictive model as a black box model using a neural network or other approximation, the calibration parameters can be determined through backpropagation, in which the weights of the neural network are determined to minimize the error between a deformation output from the prediction model and a real deformation.
The deformations (the loading force Z and the tilts Mx and My) may be measured in any order.
In step S101, the manipulator controller 13 controls the suction pad 112 to move toward the object 61 (workpiece W).
In step S104, the manipulator controller 13 controls the manipulator 111 to lift the object 61.
In step S107, the manipulator controller 13 lowers the object 61 to the intended position.
An operation performed by the suction transport apparatus 100 with the workpiece W (transport-target object W or object 61) including picking and placing the workpiece W will now be described with reference to
In step S10, the operation controller 13 vertically lowers the suction pad 112 toward the workpiece W.
In step S12, the operation controller 13 determines whether at least a part of the suction pad 112 is in contact with the workpiece W. The suction pad 112 in contact with the workpiece W tilts in X- and Y-directions, and has a tilt written using the absolute value of a vector (ex, ey) exceeding a threshold ε1, or a loading force ez in Z-direction exceeding a threshold ε2. In this state, the formula below holds.
|(ex, ey)|>ε1 or ez>ε2
More specifically, the operation controller 13 determines that the suction pad 112 is in contact with the workpiece W when the above formula holds in this step, and determines that the suction pad 112 is not in contact with the workpiece W in any other cases.
When the operation controller 13 determines that the suction pad 112 is in contact with the workpiece W (Yes in step S12), the processing advances to step S14.
When the operation controller 13 determines that the suction pad 112 is not in contact with the workpiece W (No in step S12), the processing returns to step S10, in which the suction pad 112 is further moved toward the workpiece W.
In step S14, the operation controller 13 determines whether the suction pad 112 is entirely in contact with the workpiece W. The suction pad 112 entirely in contact with the workpiece W has no tilting. The formula below holds.
|(ex, ey)|<ε1
Thus, the operation controller 13 determines that the suctioning surface of the suction pad 112 is entirely in contact with the workpiece W when the above formula holds in this step, and determines that the suctioning surface of the suction pad 112 is not entirely in contact with the workpiece W in any other cases.
When the operation controller 13 determines that the suctioning surface of the suction pad 112 is entirely in contact with the workpiece W (Yes in step S14), the control over the tilting of the suction pad 112 ends. The processing then advances to the control over the loading force (described below).
When the operation controller 13 determines that the suctioning surface of the suction pad 112 is not entirely in contact with the workpiece W (No in step S14), the processing advances to step S16.
In step S16, the contact point determiner 131 determines the position of a point of contact between the suction pad 112 and the workpiece W based on the deformation behavior of the suction pad 112.
θ=arctan(ey/ex)
The contact point determiner 131 determines a point of contact between the suction pad 112 and the workpiece W based on the angle θ.
After the point of contact is determined, the processing advances to step S18.
In step S18, the operation controller 13 changes the tilting of the suction pad 112 while maintaining the contact between the suction pad 112 and the workpiece W at the determined point of contact. More specifically, the operation controller 13 changes the tilting of the suction pad 112 to have a smaller angle between the suctioning surface of the suction pad 112 and the surface of the workpiece W to be suctioned. The operation controller 13 performs the process below to generate an operation command for the manipulator 111 to change the tilting of the suction pad 112 to align the suctioning surface with the surface of the workpiece W to be suctioned, while maintaining the contact at the point of contact.
The suction pad 112 is attachable to and detachable from the robotic arm. The operation controller 13 calculates a command speed (Pv) and a command angular speed (φw) for controlling the position and the angle (orientation) of the transport hand end at the root of the suction pad 112 in the form of a combination (simple sum) of the two command values below. The command angular speed (φw) is the rate of change of the angle of the transport hand end.
1. Command speed Pv (more specifically, command speed vector) for maintaining contact between the suction pad 112 and the workpiece W at the point of contact
Pv=(Pvr−Gv·ez)h
where Pvr is the target movement speed of the suction pad 112, Gv is the constant gain, ez is the Z-axis component of the normal vector R representing the tilting of the suction pad 112, and h is the direction vector of the hand end orientation (φ). The center dot represents multiplication.
2. Command speed (Pv) and command angular speed (φw) for rotating the suction pad 112 about the point of contact
The point of contact is used as an extension of the hand end. The position and the orientation of the point of contact are then {Pe, φe}. In step S18, the values ex and ey are small, and thus φe=φ. The formula for {Pe, φe} is given below, where Po is the pad installation position offset and Pr is the radius of the pad in
{Pe, φe}=FK({P, φ}, {Po, Pr, θ})
In this formula, Pe is the center of rotation, Po is the offset of the suction pad installation position (the distance between the center of the suctioning surface of the suction pad 112 and the hand end position of the transport apparatus), and Pr is the radius of the suction pad 112. Further, FK is the kinematic function to return {Pe, ϕe} from {P, ϕ}. The kinematic function FK has the corresponding inverse kinematic function IK, which is written as follows.
{P, φ}=IK({Pe, φe}. {Po, Pr, θ})
When a command {Pev, φev} is generated for providing a rotation on a plane including the central axis of the suction pad 112 using the center of rotation Pe, the operation controller 13 determines the function {Pv, φω} using the function IK or the Jacobian matrix derived from the function IK. This combination is used as the command speed and the command angular speed.
The operation controller 13 changes the tilting of the suction pad 112 in accordance with the command speed calculated as described above. The processing then advances to step S20.
In step S20, the operation controller 13 determines whether the suction pad 112 is entirely in contact with the workpiece W. More specifically, the operation controller 13 performs the determination through the same processing as in step S14 described above. When the operation controller 13 determines that the suctioning surface of the suction pad 112 is entirely in contact with the workpiece W (Yes in step S20), the control over the tilting of the suction pad 112 ends. The processing then advances to the control over the loading force. When the operation controller 13 determines that the suctioning surface of the suction pad 112 is not entirely in contact with the workpiece W (No in step S20), the processing returns to step S18 to continue the control over the tilting of the suction pad 112.
Through the operation example described above, the operation controller 13 determines the position of the point of contact and the tilting of the suction pad 112 after the suction pad 112 is in contact with the workpiece W, and changes the tilting of the suction pad 112 to cause the suction pad 112 to be in full contact with the surface of the workpiece W to be suctioned, while maintaining the contact at the point of contact. The orientation of the suction pad 112 can thus be corrected precisely to allow reliable picking of the workpiece W.
In step S110, the operation controller 13 vertically lowers the suction pad 112 toward the workpiece W.
In step S112, the operation controller 13 determines whether the suction pad 112 is in contact with the workpiece W based on a deformation of the suction pad 112.
When the operation controller 13 determines that the suction pad 112 is in contact with the workpiece W based on the deformation of the suction pad 112 (Yes in step S112), the processing advances to step S114. When the operation controller 13 determines that the suction pad 112 is not in contact with the workpiece W based on the deformation of the suction pad 112 (No in step S112), the processing returns to step S110, in which the suction pad 112 is further moved toward the workpiece W.
In step S114, the operation controller 13 continues to load the suction pad 112 toward the workpiece W. The operation controller 13 may change the movement speed of the suction pad 112 in accordance with the deformation behavior of the suction pad 112. For example, the operation controller 13 may reduce the speed of moving the suction pad 112 toward the workpiece W when the deformation of the suction pad 112 (the loading force ez) exceeds a first threshold. More specifically, the operation controller 13 may reduce the movement speed of the suction pad 112 in step S114 to below the movement speed of the suction pad 112 in step S110. The processing then advances to step S116.
In step S116, the operation controller 13 determines whether the suction pad 112 is loaded against the workpiece W. In this step, the operation controller 13 determines that the loading force is sufficient when the formula below holds, where c2 is the threshold for the loading force ez of the workpiece W against the suction pad 112. The operation controller 13 determines that the loading force is not sufficient in any other cases.
ez>ε2
When determining that the suction pad 112 has been loaded sufficiently against the workpiece W (Yes in step S116), the operation controller 13 stops moving the suction pad 112. For example, the operation controller 13 may stop the operation of moving the suction pad 112 toward the workpiece W when the deformation of the suction pad 112 exceeds a second threshold greater than the first threshold.
When the control over the loading force ends, the deformation information obtainer 113 turns on the vacuum pump 12 to start suctioning the object. When the manipulator controller 13 determines that the suction pad 112 has not been sufficiently loaded against the workpiece W (No in step S116), the processing returns to step S114, in which the loading operation is performed continuously.
Through the operation example described above, the deformation information obtainer 113 determines whether to continue or stop the loading operation by monitoring the loading force of the suction pad 112 against the workpiece W based on the deformation of the suction pad 112. This control allows the loading force ez of the suction pad 112 against the workpiece W within a predetermined range to allow loading of the workpiece W in picking or placing the workpiece W.
Referring now to
In step S210, the operation controller 13 vertically lowers the suction pad 112 (workpiece W) toward the platform.
In step S212, the operation controller 13 determines whether at least a part of the workpiece W gripped by the suction pad 112 is in contact with the platform at the point of contact. The operation controller 13 performs basically the same processing as in step S12 described in Operation Example 1 above. With the suctioning and the weight of the workpiece W, the deformation {ex0, ey0, ez0} of the suction pad 112 before the workpiece W is in contact with the platform is not zero in this operation. The operation controller 13 records the deformation {ex0, ey0, ez0} before the workpiece W is in contact with the platform. More specifically, the operation controller 13 determines that the workpiece W gripped by the suction pad 112 is in contact with the platform when the formula below holds, and determines that the workpiece W is not in contact with the platform in any other cases.
|(ex−ex0, ey−ey0)|>ε4 or |(ez−ez0|>ε5
When the operation controller 13 determines that a part of the workpiece W (a surface not to be suctioned) is in contact with the platform (Yes in step S212), the processing advances to step S214. When the operation controller 13 determines that a part of the workpiece W is not in contact with the platform (No in step S212), the processing returns to step S210, in which the workpiece W is further moved toward the platform.
In step S214, the operation controller 13 determines whether the lower surface of the workpiece W is entirely in contact with the platform. When the lower surface of the workpiece W is entirely in contact with the platform, the suction pad 112 and the workpiece W each have no tilting. The formula below holds.
|(ex−ex0, ey−ey0)|<ε4
Thus, the operation controller 13 determines that the lower surface of the workpiece W is entirely in contact with the platform when the above formula holds, and determines that the lower surface of the workpiece W is not entirely in contact with the platform in any other cases.
When determining that the lower surface of the workpiece W is entirely in contact with the platform (Yes in step S214), the operation controller 13 ends the control over the tilting of the suction pad 112. The processing then advances to the control over the loading force described above. When the operation controller 13 determines that the workpiece W is not entirely in contact with the platform (No in step S14), the processing advances to step S216.
In step S216, the contact point determiner 131 determines the position of a point of contact between the workpiece W and the placement target surface of the platform on which the workpiece W is to be placed based on the deformation behavior of the suction pad 112. The deformation information obtainer 113 performs basically the same processing as in step S16 in Operation Example 1. The calculation is performed with the formula below using the recorded offset {ex0, ey0, ez0}.
θ=arctan((ey−ey0)/(ex−ex0))
After the point of contact between the workpiece W and the placement target surface of the platform on which the workpiece W is to be placed is determined, the processing advances to step S218.
In step S218, the operation controller 13 changes the tilting of the suction pad 112 while maintaining the contact between the workpiece W and the placement target surface of the platform at the determined point of contact (along the contact side). The operation controller 13 changes the tilting of the suction pad 112 to have a smaller angle between the surface of the suction pad 112 not to be suctioned and the placement target surface of the platform.
The operation controller 13 performs basically the same processing as in step S18 described in Operation Example 1 above to calculate the command speed for changing the tilting of the workpiece W to align the suctioning surface of the suction pad 112 with the surface of the platform while maintaining the contact at the point of contact.
The operation controller 13 performs the calculation with the formula below using the recorded offset {ex0, ey0, ez0}, with the terms being changed in the manner described below.
The term ez is replaced with ez−ez0.
For the term {Pe, φe}, the point of contact between the suction pad 112 and the workpiece W is replaced with the point of contact between the workpiece W and the platform.
The term {FK({P, φp}, {Po, Pr, θ}) is replaced with {FK({P, φ}, {Po+Wh/2, Pr+WI/2, θ}).
In the above formula, Wh is the height of the workpiece W, WI is the length of the workpiece W, and FK is the same kinematic function as FK in step S18 in Operation Example 1.
Thus, the term
{P, φ}=IK({Pe, φe}, {Po, Pr, θ}) is replaced with {P, φ}=IK({Pe, φe }, {Po+Wh/2, Pr+WI/2, θ}).
In the above formula as well, IK is the same kinematic function as IK in step S18 in Operation Example 1.
Through the processing described above, the operation controller 13 changes the tilting of the suction pad 112 in accordance with the command speed calculated as described above. The processing then advances to step S220.
In step S220, the operation controller 13 determines whether the surface of the workpiece W that is not the surface to be suctioned is entirely in contact with the placement target surface of the platform. The operation controller 13 performs the same processing as in step S214 above.
When determining that the surface of the workpiece W that is not the surface to be suctioned is entirely in contact with the placement target surface of the platform (Yes in step S220), the operation controller 13 ends the control over the tilting of the suction pad 112, and stops the suctioning operation and releases the workpiece. When the operation controller 13 determines that the surface of the workpiece W that is not the surface to be suctioned is not entirely in contact with the placement target surface of the platform (No in step S220), the processing returns to step S218 to continue the control over the tilting.
Through the operation example described above, the operation controller 13 determines the position of the point of contact and the tilting of the suction pad 112 after the surface of the workpiece W that is not the surface to be suctioned is in contact with the placement target surface of the platform, and changes the tilting of the suction pad 112 to cause the surface of the workpiece W that is not the surface to be suctioned to be entirely in contact with the placement target surface of the platform, while maintaining the contact at the point of contact. The orientation of the suction pad 112 can thus be corrected precisely to allow placement of the workpiece W onto an accurate position. This structure also prevents the released workpiece W from receiving impact or the released workpiece W from falling.
The embodiments of the present invention described in detail above are mere examples of the present invention in all respects. The embodiments may be variously modified or altered without departing from the scope of the present invention. For example, the embodiments may be modified in the following forms. The same components as those in the above embodiments are hereafter given the same numerals, and the operations that are the same as those in the above embodiments will not be described. The modifications described below may be combined as appropriate.
The structure of a deformation measuring device according to each of modifications will be described with reference to
The deformation change rate calculator 36 calculates a deformation change rate by calculating a time integral of the deformation determined by the deformation determiner 124. The deformation change rate calculator 36 outputs the deformation change rate to the constant gain multiplier 37.
The constant gain multiplier 37 calculates a deceleration value by multiplying, by a constant, the deformation change rate (e.g., the angular speed of the suctioning surface of the suction pad) calculated by the deformation change rate calculator 36. The constant gain multiplier 37 outputs the deceleration value to the manipulator controller 13.
The manipulator controller (operation controller) 13 has a target movement speed for the suction pad 112 to transport an object. The manipulator controller 13 obtains the command speed by subtracting the deceleration value from the target movement speed. The manipulator controller 13 controls the manipulator 111 to move the hand end (suction pad 112) of the manipulator at the command speed. The speed for moving the hand end of the robotic arm is changed to lower the deformation change rate of the suction pad 112 to dampen vibrations of the suction pad 112 (vibrations of the object).
Similarly, the manipulator controller 13 may change the tilting of the suction pad 112 to decrease the deformation change rate based on the deformation change rate. The tilting of the suction pad 112 is changed to dampen vibrations of the suction pad 112. The tilting of the suction pad 112 is used in such vibration damping to minimize the time for positioning when the transportation is stopped, and also to shorten the processing time for transportation (takt time in transportation).
In step S201, the manipulator controller 13 controls the suction pad 112 to move toward the object 61.
In step S204, the manipulator controller 13 controls the manipulator 111 to lift the object 61.
In step S207, the manipulator controller 13 determines whether the suction pad 112 being transported is vibrating. The manipulator controller 13 determines that the suction pad 112 being transported is vibrating in response to the deformation change rate of the suction pad 112 being greater than or equal to another threshold. When determining that the suction pad 112 being transported is not vibrating (Yes in step S207), the manipulator controller 13 transports the object 61 to an intended position without changing the tilting of the object 61 (step S208). In response to a determination that the suction pad 112 being transported is vibrating (Yes in step S207), the manipulator controller 13 controls the tilting of the suction pad 112 (step S212). The processing in step S207 is then repeated.
In step S209, the manipulator controller 13 controls the manipulator 111 to lower the object 61 to the intended position.
The control blocks of the deformation measuring device 1 (in particular, the image processor 119, the image obtainer 120, the feature point specifier 123, the deformation determiner 124, the manipulator controller 13, the manipulator deceleration command calculator 113, the deformation change rate calculator 36, and the constant gain multiplier 37) may be implemented by, for example, a logic circuit (hardware) in an integrated circuit (IC chip) or by software.
When using software for implementing these control blocks, the deformation measuring device 1 includes a computer for executing instructions included in a software program for implementing the functions of the control blocks. The computer includes, for example, one or more processors and a computer-readable recording medium storing the program. The processors in the computer read the program from the recording medium and execute the program to achieve the aspects of the present invention. The processors are, for example, CPUs. The recording medium may be a non-transitory tangible medium, such as a ROM, a tape medium, a disk, a card, a semiconductor memory, or a programmable logic circuit. The computer may additionally include a RAM for expanding the program. The program may be provided through any transmission medium (such as a communication network or broadcast waves) that can transmit the program to the computer. One aspect of the present invention may be a data signal superimposed on carrier waves representing the program through electronic transmission.
The embodiments described herein should not be construed to be restrictive, but may be modified within the scope of the claims. The technical features described in different embodiments may be combined in other embodiments within the technical scope of the invention. The technical means disclosed in different embodiments may be combined to produce a new technical feature.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/018988 | 5/13/2019 | WO | 00 |
