Patent Application
20230241767
The present disclosure relates to a control device and an operation method of a robot hand.
A robot hand including a parallel gripper and a manipulator including a parallel gripper in an effector have been already known (PTL 1).
PTL 1: Japanese Unexamined Patent Application Publication No. 2017-164899
In a parallel gripper, a target object is gripped by bringing a set or a pair of movable members that are parallel to each other close to or away from each other; therefore, in many cases, contact of the parallel gripper with the target object is line contact or point contact, and a contact area formed between the parallel gripper and the target object upon gripping is narrow. For stable gripping of target objects having various shapes, it is desired to secure an appropriate contact area and enhance gripping stability. However, in order to achieve these by adoption of a multi-flexible multi-finger hand, it is necessary to increase degrees of freedom of motion of a robot hand, which causes an issue that an increase in size of the robot hand occurs and complication of the configuration and control of the robot hand occurs.
It is desirable to provide a control device and an operation method of a robot hand that make it possible to achieve both securing of gripping stability and suppression of increase in size.
A control device of a robot hand according to an embodiment of the present disclosure is a control device of a robot hand including a first finger and a second finger of which finger pad surfaces are opposed to each other, and the control device includes: a target object determining unit that is configured to be able to determine a target object; a operation mode selector that is configured to be able to select an operation mode between a first operation mode and a second operation mode in accordance with the target object determined by the target object determining unit, the second operation mode in which contact areas of the finger pad surfaces of the first finger and the second finger with the target object are wider than in the first operation mode; and a hand controller that is configured to be able to control an operation of the robot hand upon gripping the target object in the operation mode selected by the operation mode selector.
An operation method of a robot hand according to an embodiment of the present disclosure is an operation method of a robot hand including a first finger and a second finger of which finger pad surfaces are opposed to each other, and the operation method includes: determining a target object; selecting an operation mode between a first operation mode and a second operation mode in accordance with the determined target object, the second operation mode in which contact areas of the finger pad surfaces of the first finger and the second finger with the target object are wider than in the first operation mode; and gripping the target object in the selected operation mode.
In the following, some embodiments of the present disclosure are described in detail with reference to the drawings. The following description is given of specific examples of the present disclosure, and the present disclosure is not limited to the following embodiments. Moreover, similarly, the present disclosure is not limited to positions and dimensions of respective components, and dimension ratios between components illustrated in the respective drawings.
Description is given in the following order.
The robot hand H is mounted on a tip of an operation arm A, and configures an effector of a manipulator. In the present embodiment, the manipulator has a series type configuration, and includes the operation arm A and the robot hand H. The operation arm A includes a base end and a terminal end, and has a long shape in an axial direction from the base end to the terminal end. The base end of the operation arm A is mountable to a main body of any robot. The robot hand H is coupled to the terminal end of the operation arm A. In the present embodiment, the robot hand H includes a wrist section 5, and is rotatable about an axis parallel or perpendicular to a longitudinal axis of the operation arm A by joint motion of the wrist section 5. In the following description, side away from the base end of the operation arm A toward a fingertip section of the robot hand H is referred to as distal side, and side approaching the base end of the operation arm A from the fingertip section of the robot hand H is referred to as proximal side.
The robot hand H roughly includes the palm section 1, a first finger 2, and the second finger 3.
The palm section 1 serves as a mount that supports fingers of the robot hand H, that is, the first finger 2 and the second finger 3 that are to be described below, and determines a shortest separation distance between a base of the first finger 2 and a base of the second finger 3. In the present embodiment, the shortest separation distance is a distance formed between the base of the first finger 2 and the base of the second finger 3 in a state in which the second finger 3 is stretched in parallel to the central axis Ax0 of the palm section 1 ((b) of
The first finger 2 extends from the palm section 1 to the distal side, and has a finger pad surface 21 opposed to the central axis Ax0 of the palm section 1. In the present embodiment, the central axis Ax0 of the palm section 1 coincides with the longitudinal axis of the operation arm A, and passes through the distal surface 11.
The second finger 3 extends from the palm section 1 to the distal side, and has finger pad surfaces 31a and 31b opposed to the finger pad surface 21 of the first finger 2 with the central axis Ax0 of the palm section 1 interposed therebetween. The finger pad surface 21 of the first finger 2 and the finger pad surfaces 31a and 31b of the second finger 3 serve as contact surfaces with an object targeted for gripping by the robot hand H (hereinafter referred to as a “target object”). That is, for gripping, the robot hand H makes contact with the target object with these finger pad surfaces 21, 31a, and 31b to exert grip force on the target object. In the present embodiment, the first finger 2 has the finger pad surface 21 entirely from a fingertip section to the base. In contrast, the second finger 3 has the finger pad surface 31a in a distal phalanx section l3 and the finger pad surface 31b in a middle phalanx section l2.
The robot hand H has four degrees of freedom contributing to gripping of the target object in addition to a degree of freedom given by the wrist section 5.
The robot hand H includes a proximal joint j1 in the palm section 1. The proximal joint j1 couples the second finger 3 to the palm section 1 pivotably about a first axis (which may be referred to as a first pitch axis) Ax1. The second finger 3 includes a base phalanx section (which may be referred to as a first or base joint link) l1 provided close to the palm section 1, a distal phalanx section (which may be referred to as a third or distal joint link) l3 provided closer to the distal side than the base phalanx section l1, and a middle phalanx section (which may be referred to as a second or middle joint link) l2 provided between the base phalanx section l1 and the distal phalanx section l3, and includes two joints j2 and j3. One of the two joints j2 and j3 is a middle joint j2 that causes the middle phalanx section l2 to be coupled to the base phalanx section l1 bendably and strechably about a second axis (which may be referred to as a second pitch axis) Ax2, and the other one is a distal joint j3 that causes the distal phalanx section l3 to be coupled to the middle phalanx section l2 bendably and strechably about a third axis (which may be referred to as a third pitch axis) Ax3. In the present embodiment, the first, second, and third axes Ax1, Ax2, and A3 are parallel to each other, and the first axis Ax1 and the central axis Ax0 of the palm section 1 have a positional relationship in which the first axis Ax1 and the central axis Ax0 three-dimensionally intersect with each other.
In contrast, the first finger 2 does not have degrees of freedom in bending and stretching directions, and is revolvable about a fourth axis (may be referred to as a yaw axis y relative to the pitch axis p) Ax4 with respect to the palm section 1. The fourth axis is coincident with or parallel to the central axis Ax0 of the palm section 1. The fourth axis Ax4 is located at a position three-dimensionally intersecting with the first axis Ax1, and is coincident with the central axis Ax0 of the palm section 1 in the present embodiment. For example, the first finger 2 is formed with use of a single link member entirely from the fingertip section to the base, which makes it possible to have a configuration having rigidity in the bending and stretching directions and having no degree of freedom.
Thus, the robot hand H has the following four degrees of freedom as degrees of freedom contributing to gripping of the target object. A first degree of freedom is one degree of freedom (a degree of freedom in a revolving direction about the fourth axis Ax4) given to the first finger 3 by the palm section 1. A second degree of freedom is one degree of freedom (a degree of freedom in a rotating direction about the first axis Ax1) given to the second finger 3 by the proximal joint j1 of the palm section 1. Third and fourth degrees of freedom are two degrees of freedom (degrees of freedom in bending and stretching directions about the second axis Ax2 and the third axis Ax3) of the middle joint j2 and the distal joint j3 of the second finger 3.
In the present embodiment, the first finger 2 has a narrower finger width than the second finger 3, and as illustrated in (b) of
Furthermore, as illustrated in (a) and the upper part of (b) in
In the present embodiment, in addition to the above degrees of freedom, the following two degrees of freedom are set as degrees of freedom by the wrist section 5. The two degrees of freedom include one degree of freedom in a rotating direction about the central axis (that is, the yaw axis y) of the palm section 1, and one degree of freedom in a swinging direction about an axis (that is, the pitch axis p) parallel to the first axis Ax1. Thus, it is possible for the robot hand H to apply a twist to the operation arm A by the wrist section 5, and it is possible to swing the entire robot hand H with the wrist section 5 as a starting point. It is possible to give a degree of freedom in a swinging direction about a roll axis r perpendicular to the central axis Ax0 of the palm section 1 in place of or in addition to the degree of freedom about the pitch axis p.
The robot hand H includes the number of actuators corresponding to the degrees of freedom in the wrist section 5, and includes an actuator for each of the palm section 1 (including the proximal join j1), and the middle joint j2 and the distal joint j3 of the second finger 3. In the present embodiment, the proximal joint j1 has a larger diameter than each of the middle joint j2 and the distal joint j3, and as an actuator included in the proximal joint j1, it is possible to adopt an actuator having a larger output than actuators included in the middle joint j2 and the distal joint j3. Examples of an applicable actuator may include an electric motor, and it is possible to adopt, for the proximal joint j1, an electric motor that is able to output a higher torque than those for the middle joint j2 and the distal joint j3.
In the present embodiment, a control unit 101 configured as an electronic control device is provided, and operations of the actuators are controlled by the control unit 101, which makes it possible to control a posture and an operation of the robot hand H upon gripping the target object. A control system including the control unit 101 is described in more detail later.
The respective dimensions illustrated in
L3+L8/2<L7 (1)
L1=L2=L3 (2)
The control system S roughly includes the control unit 101 (
The sensors 201 to 204 are disposed at different parts of the robot hand H, and are used to grasp a positional relationship between the robot hand H and the target object and detect contact of the robot hand H with the target object.
The sensor 201 is provided in the palm section 1, and is able to detect the position of the target object relative to the palm section 1 and detect contact of the target object with the distal surface 11 of the palm section 1. Examples of a sensor applicable to the sensor 201 may include a tactile sensor and a proximity sensor, and it is possible to use a visual sensor or a camera as a substitute.
The sensor 202 is provided in the first finger 2, and detects contact of the target object with the finger pad surface 21 of the first finger 2. Examples of a sensor applicable to the sensor 202 may include a tactile sensor and a proximity sensor.
The sensor 203 is provided in the middle phalanx section l2 of the second finger 3, and detects contact of the target object with the finger pad surface 31b of the middle phalanx section l2. Examples of a sensor applicable to the sensor 203 may include a tactile sensor and a proximity sensor.
The sensor 204 is provided in the distal phalanx section l3 of the second finger 3, and detects contact of the target object with the finger pad surface 31a of the distal phalanx section l3. Examples of a sensor applicable to the sensor 204 may include a tactile sensor and a proximity sensor.
In the present embodiment, the sensor 204 provided in the distal phalanx section l3 has higher resolution than the sensor provided in the middle phalanx section l2, but has a low load range. This is because of a difference in use of sensor output upon gripping the target object. In the first operation mode (same plane parallel track gripping mode) to be described later, a relatively small and light object is a target for gripping, and the high-resolution sensor 204 included in the distal phalanx section l3 is used to control grip force of the robot hand H. In contrast, in the second operation mode (multi-point contact gripping mode), a relatively large and heavy object is a target for gripping, and the high-load range sensor 203 included in the middle phalanx section l2 is used to control the grip force of the robot hand H. Thus, in the present embodiment, a sensor to be used for control of the grip force is switched between the sensors 203 and 204 depending on the size, shape, and the like of the target object.
It is possible to provide a sensor in the base phalanx section l1 in addition to the middle phalanx section l2 and the distal phalanx section l3 of the second finger 3 and use the sensor for control of the actuator ACT upon gripping the target object.
As one example, the control unit 101 is configured as a microcomputer that includes a central processing unit (CPU) including a processor and the like, various storage devices such as a ROM or a RAM, an input/output interface, and the like, and receives detection signals inputted from the sensors 201 to 204 and executes an operation in accordance with a command of a predetermined program on the basis of inputted sensor signals. A command signal obtained as a result of the operation is then outputted to a driving unit of the actuator ACT.
In the present embodiment, the control unit 101 determines the target object, and selects an operation mode between the first operation mode, that is, the same plane parallel track gripping mode, and the second operation mode, that is, the multi-point contact gripping mode in accordance with the determined target object. The control unit 101 then controls the operation of the robot hand H upon gripping the target object in the selected operation mode. Here, the second operation mode is selected upon gripping a relatively large target object, and is characterized as an operation mode in which contact areas of the finger pad surfaces 21, 31a, and 31b of the first finger 2 and the second finger 3 with the target object are wider than in the first operation mode. In the present embodiment, switching of the contact areas is caused by changing parts to be brought into contact with the target object upon gripping, of the palm section 1, the first finger 2, and the second finger 3. The control unit 101 roughly includes a target object determining unit 111, an operation mode selector 121, and a hand controller 131.
The target object determining unit 111 determines the target object. In the present embodiment, determination of the target object includes determination of the size, shape, material, and the like of the target object. Determination of the target object is achievable by creating a list in which information about the sizes, shapes, materials, and the like of target objects is determined in advance, and storing the list in the control unit 101, and is also achievable by providing a camera to be capable of photographing the target object, and determining the type or attribute of the target object on the basis of image data or the like obtained by the camera.
The operation mode selector 121 selects the operation mode between the first operation mode and the second operation mode in accordance with the target object determined by the target object determining unit 111.
Specifically, the operation mode selector 121 compares a dimension of the target object with a preset reference dimension, and in a case where the dimension of the target object is smaller than the reference dimension, the operation mode selector 121 selects the first operation mode. In contrast, in a case where the dimension of the target object is larger than the reference dimension, the operation mode selector 121 selects the second operation mode. As described above, the second operation mode is an operation mode in which contact areas of the finger pad surfaces 21, 31a, and 31b of the robot hand H with the target object are wider than in the first operation mode.
The reference dimension is, for example, a possible maximum value of a distance between an end of the fingertip section of the first finger 2 and an end of the distal phalanx section l3 of the second finger 3 in a state in which the fingertip section of the first finger 2 and the distal phalanx section l3 of the second finger 3 are located on the same plane perpendicular to the central axis Ax0 of the palm section 1. The reference dimension in this case is given as a dimension indicated by the sign L6 in (a) of
Alternatively, the reference dimension may be a distance determined in a direction parallel to the central axis Ax0 of the palm section 1 between the tip of the first finger 2 and the distal surface 11 of the palm section 1. The reference dimension in this case is given as a dimension indicated by the sign L7 in (a) and (b) of
In the present embodiment, the operation mode selector 121 selects the first operation mode in a case where the horizontal width dimension of the target object is smaller than a first reference dimension L6 and the height dimension of the target object is smaller than a second reference dimension L7, and selects the second operation mode in a case where the horizontal width dimension of the target object is larger than the first reference dimension L6 or the height dimension of the target object is larger than the second reference dimension L7.
The hand controller 131 controls the operation of the robot hand H upon gripping the target object in the operation mode selected by the operation mode selector 121.
As described above, distinction between the first operation mode and the second operation mode is made in a contact area formed between the target object and the robot hand H upon gripping, and the first operation mode is characterized as an operation mode of a relatively small contact area, and the second operation mode is characterized as an operation mode of a relatively large contact area. Furthermore, in the present embodiment, magnitude of grip force to be exerted on the target object by the robot hand H differs between the first operation mode and the second operation mode, and the positions and characteristics of the sensors 203 and 204 used for control of the grip force, that is, resolutions and load ranges of the sensors are changed in accordance with this.
The above operation is a basic operation to be performed by the robot hand H upon gripping the target object. In the present embodiment, in addition to the above-described modes, the following two modes are adopted as derivative modes classified into the first operation mode and the second operation mode.
One of the modes is a derivative mode in a case where an object having an inclined side surface or a tapered shape is a target for gripping, and is classified into the first operation mode. Specifically, in advance of bringing the finger pad surface 31a of the distal phalanx section l3 of the second finger 3 into contact with the target object, the first finger 2 is revolved about the fourth axis Ax4 to bring the orientation of the finger pad surface 21 of the first finger 2 close to the orientation of the side surface of the target object, thereby matching inclination of the finger pad surface 21 to inclination of the side surface of the target object.
The other mode is a derivative mode in a case where an object having a narrow horizontal width W or a small height H but having a large moment load (e.g., an object like a handle of a frying pan or a rod having a long tip) is a target for gripping, and is classified into the second operation mode. Specifically, the distal surface 11 of the palm section 1 is brought into contact with the target object, and the finger pad surface 21 of the first finger 2 is further brought into contact with the target object, and thereafter, the proximal joint j1 is rotated, and the middle joint j2 and the distal joint j3 are bent. Thus, the second finger 3 is closed to surround the target object by the second finger 3, thereby exerting grip force. This is a generally known gripping form as a form closure.
In S101, a target object 101 is recognized.
In S102, dimensions of the target object 101 are obtained. In the present embodiment, a horizontal width dimension W of a part, on which grip force is to be exerted by the robot hand H, of the target object, and a height dimension H of the target object are obtained.
In S103, whether or not a load applied from the target object upon gripping is within a range of a standard load is determined. In a case where the load is within the range of the standard load, the flow proceeds to S104, and in a case where the load is not within the range of the standard load, the flow proceeds to S107. It is possible to determine the standard load as the weight of the target object or a moment load applied from the target object to the robot hand H.
In S104, whether or not the horizontal width dimension W of the target object is equal to or smaller than the first reference dimension L6 is determined. In a case where the horizontal width dimension W is equal to or smaller than the first reference dimension L6, the flow proceeds to S105, and in a case where the horizontal width dimension W exceeds the first reference dimension L6, the flow proceeds to S107.
In S105, whether or not the height dimension H of the target object is equal to or smaller than the second reference dimension L7 is determined. In a case where the height dimension H is equal to or smaller than the second reference dimension L7, the flow proceeds to S106, and in a case where the height dimension H exceeds the second reference dimension L7, the flow proceeds to S107.
In S106, as the operation mode of the robot hand H, the first operation mode is selected.
In S107, as the operation mode of the robot hand H, the second operation mode is selected.
In a case where the first operation mode is selected, the flow proceeds to the flowchart illustrated in
In S201, the fingertip section of the first finger 2 is adjusted roughly to the height of the center of gravity of the target object, and the angle of the fingertip section of the first finger 2 is adjusted to make the finger pad surface 21 of the first finger 2 roughly parallel to a side surface of the target object. This adjustment is enabled mainly by an operation of the wrist section 5.
In S202, the fingertip section of the first finger 2 is brought close to the target object to bring the finger pad surface 21 of the first finger 2 into contact with a side surface disposed at the height of the center of gravity of the target object.
In S203, the angle of a side surface of the target object on side opposite to the side surface in contact with the finger pad surface 21 of the first finger 2 is measured.
In S204, the angle of the distal phalanx section l3 of the second finger 3 is adjusted close to the measured angle. This adjustment is made by appropriately operating the proximal joint j1, the middle joint j2, and the distal joint j3. Thereafter, while the distal phalanx section l3 is moved so as to maintain the adjusted angle of the distal phalanx section l3, the distal phalanx section l3 of the second finger 3 is brought close to the target object. Here, if necessary, it is possible to assist an operation of maintaining the angle of the distal phalanx section l3 by relatively rotating the first finger 2 about the fourth axis Ax4.
In S205, the finger pad surface 31a of the distal phalanx section l3 of the second finger 3 is brought into contact with the side surface of the target object on the opposite side.
In S206, grip force by the robot hand H is exerted on the target object to complete gripping.
In a case where the second operation mode is selected, the flow proceeds to the flowchart illustrated in
In S301, the second finger 3 is outwardly rotated about the first axis Ax1 by an operation of the proximal joint l1 to expand an opening formed between the first finger 2 and the second finger 3 to such an extent that an object targeted for gripping is receptible.
In S302, the robot hand H is brought close to the target object to bring the distal surface 11 of the palm section 1 into contact with the target object.
In the following S202 and subsequent steps, operations similar to those in S202 to S206 in the first operation mode are performed. That is, the fingertip section of the first finger 2 is brought close to the target object to bring the finger pad surface 21 of the first finger 2 into contact with the side surface located at the height of the center of gravity of the target object (S202). The angle of the side surface of the target object on side opposite to the side surface in contact with the finger pad surface 21 of the fingertip section of the first finger 2 is measured (S203). The angle of the distal phalanx section l3 of the second finger 3 is adjusted close to the measured angle, and the distal phalanx section l3 of the second finger 3 is brought close to the target object while maintaining the adjusted angle of the distal phalanx section l3 (S204). The finger pad surface 31a is brought into contact with the side surface of the target object on the opposite side (S205). Furthermore, grip force on the target object is produced (S206). Thus, gripping is completed.
It is possible to perform production of grip force in S206 as follows, for example.
A state of “partial sliding” that occurs before occurrence of sliding of the target object with respect to a contact section of the robot hand H, that is, with respect to the finger pad surfaces 21, 31a, and 31b of the first finger 2 and the second finger 3 in the present embodiment (that is a state in which the entire target object is relatively moved with respect to the finger pad surfaces 21, 31a, and 31b, and may be hereinafter referred to as “entire sliding”) is detected. The partial sliding is a state in which only a portion of a contact section of the target object with the robot hand H is moved before the entire sliding of the target object occurs. It is possible to detect the partial sliding, for example, by a distributed pressure sensor in which a surface of a sensor element is covered with a viscous or elastic material such as urethane gel or silicon gel. At least two pressure sensors that are different from each other in coefficient of friction of a covering material are disposed at different parts of the finger pad surfaces 21, 31a, and 31b, and a state in which pressure in accordance with movement of the target object is changed only in outputs from some sensor elements covered with a material having a low coefficient of friction is detected on the basis of signals outputted from these two or more pressure sensors. Then, in a case where the partial sliding occurs, grip force of the robot hand H is maintained as it is. In contrast, in a case where the entire sliding occurs, grip force of the robot hand H is increased to prevent the target object from dropping off. In a case where pressure in accordance with movement of the target object is not changed in outputs from all the pressures sensors, it is considered that there is a margin in the current grip force, and it is possible to decrease the grip force. This makes it possible to reduce electric power consumed by driving of actuators. The grip force obtained through monitoring of the partial sliding is minimum grip force not to cause the entire sliding of the target object.
Examples of gripping of specific target objects in the first operation mode and the second operation mode are described below.
In addition to the above modes, in the present embodiment, a third operation mode is adopted in which the first finger 2 is opened in a plane perpendicular to the central axis Ax0 of the palm section 1.
According to a typical parallel gripper as an effector included in a manipulator of a robot arm or the like, a target object is gripped by bringing a set or a pair of movable members, which are parallel to each other, close to or away from each other; therefore, in many cases, contact of the parallel gripper with the target object is line contact or point contact, and the shape of the target object that is stably grippable is limited. For stable gripping of target objects having various shapes, it is desired to make controllable the position of a contact section of the robot hand with the target object and the angle of the robot hand or a finger thereof upon bringing the robot hand close to the target object. However, it is necessary to increase degrees of freedom of motion of the robot hand, which causes an issue that an increase in size of the robot hand occurs and complication of the configuration and control of the robot hand further occurs. Furthermore, the increase in size of the robot hand causes an increase in load on an arm supporting the robot hand, which induces an issue that applications to which the robot hand is applicable are limited.
Here, the robot hand having a multi-flexible multi-finger configuration makes it possible to secure gripping stability. However, in a multi-flexible multi-finger hand, an increase in size and configuration complication are not avoidable, and control also tends to be complicated. In addition, in many cases, a mechanism that interlocks a DIP joint and a PIP joint with each other is adopted; therefore, it is difficult to secure sufficient operability. The same applies to an underactuated hand by tendon drive, and it is difficult to sufficiently cope with adjustment of a relative angle between fingers.
In contrast, according to the present embodiment, relative positions and angles of the finger pad surfaces 21, 31a, and 31b of the first finger 2 and the second finger 3 are changed in accordance with the size, shape, and the like of the target object, which makes it possible to secure a necessary contact area of the robot hand H for gripping the target object and secure gripping stability of the robot hand H.
Specifically, the target object is determined, and the contact areas of the finger pad surfaces 21, 31a, and 31b of the first finger 2 and the second finger 3 with the target object are switchable in accordance with a result of determination, which makes it possible to grip the target object with a contact area corresponding to the size, shape, and the like of the target object. This makes it possible to form a more appropriate contact area for obtaining necessary grip force, and makes it possible to enhance gripping stability.
Here, for gripping a relatively small target object, the first operation mode in which the contact area is narrow is selected, and for gripping a relatively large target object, the second operation mode in which the contact area is wide is selected, which makes it possible to have an appropriate contact area.
Furthermore, while the degrees of freedom in the bending and stretching directions by the middle joint j2 and the distal joint j3 in addition to the proximal joint j1 are given to the second finger 3, the degrees of freedom in the bending and stretching directions are not given to the first finger 1 to make the robot hand H realizable with a simple configuration, which makes it possible to minimize the number of degrees of freedom given to fingers and suppress an increase in the number of components. As described above, according to the present embodiment, it is possible to achieve both securing of gripping stability and suppression of an increase in size due to an increase in the degrees of freedom, and further achieve suppression of complication of the configuration and control.
Of a plurality of sensors disposed at different parts, a sensor used for control is switched in accordance with the operation mode, which makes it possible to grasp an actual contact area and obtain useful sensor information for production of appropriate grip force. Specifically, in the first operation mode, adopting a high-resolution sensor included in the distal phalanx section l3 makes it possible to obtain useful sensor information for production of grip force on a relatively small and light target object. In contrast, in the second operation mode, adopting a high-load range sensor included in the middle phalanx section l2 makes it possible to obtain useful sensor information for production of grip force on a relatively large and heavy target object.
In the first operation mode, the finger pad surface 21 of the first finger 2 is first brought into contact with the target object, and the distal phalanx section l3 of the second finger 3 is then brought close to the target object along a track on the same plane while maintaining the adjusted angle of the distal phalanx section l3 to bring the finger pad surface 31a of the distal phalanx section l3 of the second finger 3 into contact with a side surface of the target object, which makes it possible to bring the entire finger pad surface 31a into contact with the side surface of the target object while suppressing movement of the target object while bringing the distal phalanx section l3 of the second finger 3 close to the target object.
Furthermore, the first finger 2 is revolvable about the fourth axis Ax4, and in advance of bringing the finger pad surface 31a into contact with the side surface of the target object, the first finger 2 is relatively revolved about the fourth axis Ax4 to change an angle formed between the finger pad surface 21 of the first finger 2 and the finger pad surfaces 31a and 31b of the second finger 3, which makes it possible to achieve gripping with a widest possible contact area with a target object not having gripping surfaces that are not parallel to each other, such as an inclined surface or a tapered shape. This makes it possible to achieve further improvement in gripping stability.
In contrast, in the second operation mode, the distal surface 11 of the palm section 1 is first brought into contact the target object, and the finger pad surface 21 of the first finger 2 is then brought into contact with the target object, and thereafter, the finger pad surface 31b of the middle phalanx section l2 and the finger pad surface 31a of the distal phalanx section l3 in the second finger 3 are brought into contact with the target object in this order. This makes it possible to bring the entire finger pad surfaces 21, 31a, and 31b of the robot hand H into contact with the target object while suppressing movement of the target object during gripping, and produce grip force with use of the entire first finger 2 and the entire second finger 3.
The first finger 2 does not have degrees of freedom in bending and stretching directions, which allows for high-load manipulation on a target object having a large weight. For example, manipulation is possible such as pushing, pulling, rotating, crushing, tapping, rubbing, supporting, and hooking and moving of the target object. Moreover, rattling of a joint due to backlash does not occur, which allows for a highly accurate operation by the first finger 2. Furthermore, it is possible to eliminate joints due to reduction in degrees of freedom, which makes it easy to apply treatment such as waterproofing and dustproofing.
The finger width of the first finger 2, especially, the finger width of the fingertip section of the first finger 2 is narrow, which allows for manipulation on a fine target object. For example, it is easy to perform, for example, an operation such as inserting the fingertip section into a narrow hole or depression (hooking on a handle and pulling a target), or pushing a narrow surface with a fingertip section (locally pushing the target object). Moreover, while the finger pad surface 21 of the first finger 2 is put to an inner surface of a shell of the target object having a shell shape, specifically the finger pad surface 31a of the distal phalanx section l3 of the second finger is put to an outer surface of the shell, which makes it possible to secure contact areas with both the inner surface and the outer surface of the shell by pinching an edge of the target object, and provide stable gripping.
In contrast, the finger width of the second finger 3 is wide, which makes it easy to secure mounting space for an actuator that drives a joint of the second finger 3 (in other words, to achieve an increase in grip force by mounting a large actuator) and mount a sensor on the second finger 3. For example, it is possible to mount a plurality of sensors on each of link portions between joints, that is, the base phalanx section l1, the middle phalanx section l2, and the distal phalanx section l3.
The first finger 2 is revolvable about the fourth axis Ax4 in parallel to the central axis Ax0 with respect to the palm section 1, which makes it possible to change relative angles of the finger pad surfaces 21, 31a, and 31b of the first finger 2 and the second finger 3 in a plane perpendicular to the central axis Ax0 of the palm section 1, and grip the target object having a inclined surface or a tapered shape with the angle or direction of the finger pad section that is coincident with the target object. Furthermore, upon gripping, it is possible to adjust a positional relationship of the first finger 2 and the second finger 3 in accordance with dimensions of the target object and achieve appropriate grip force. The first finger 2 is revolved about the fourth axis Ax4 to bring the first axis 2 and the second finger 3 close to each other and reduce volumetric capacity of space occupied by the entire robot hand H, which makes it possible to reduce storage space and cope with applications in a narrow place.
The first finger 2 is opened in a plane perpendicular to the central axis Ax0 of the palm section 1, which makes it possible to naturally execute interaction accompanied by contact such as handshaking with a human, and makes it possible to cope with applications (e.g., an operation of wiping a table) in a state in which the palm section 1 is widely opened. Furthermore, disposing a pair of robot hands H in such an operation mode in mirror symmetry enables execution of gripping with both hands using both arms, which makes it possible to take an approach of supporting the target object with a large plane or holding the target object by sandwiching the target object from both sides. In such a case, it is possible to avoid the first finger 2 from being an obstruction.
An angle upon making the finger pad surface 21 of the first finger 2 in contact with the target object is adjustable by the wrist section 5, which makes it possible to achieve higher gripping stability.
In the first modification example, a gripping assist unit U that supports gripping of the target object is disposed in each of the phalanx sections l1, l2, and l3 of the second finger 3. Examples of units applicable to the gripping assist unit U may include a variable adhesion unit or a variable friction unit in which adhesive force or friction force is adjustable. As the gripping assist unit U, it is possible to adopt a variable suction unit in which suction force is exerted on the target object and the suction force is adjustable.
In the second modification example, a brake mechanism B that is configured to be able to fix a relative positional relationship of the base phalanx section l1, the middle phalanx section l2, and the distal phalanx section l3 is disposed in the robot hand H. Examples of the applicable brake mechanism B may include a wire-driving brake mechanism. The brake mechanism makes it possible to support grip force by an actuator, and produce grip force by a mechanical limit of the brake mechanism independent of output of the actuator.
In place of or in addition to the brake mechanism, it is possible to provide a biasing mechanism that is configured to be able to bias the proximal joint j1, the middle joint j2, and the distal joint j3 in a bending or stretching direction of the second finger 3. The second finger 3 is bent by the biasing mechanism at the time of stopping the robot hand H so as to fold the finger, which makes it possible to reduce volumetric capacity of space occupied by the entire robot hand H, and reduce storage space.
In the present embodiment, a size relationship of the finger widths of the first finger 2 and the second finger 3 included in a robot hand H′ is opposite to that in the first embodiment described above. In such a manner, the robot hand H′ may have a configuration including the first finger 2 having a wide finger width (specifically, a finger width of a tip) and the second finger 3 having a narrower finger width (specifically, a finger width of a distal phalanx section) than the first finger 2. As with the first embodiment described above, the first finger 2 does not have degrees of freedom in the bending and stretching directions, and the second finger 3 has three degrees of freedom by the proximal, middle, and distal joints j1, j2, and j3.
In the above description, the robot hand H is adopted that includes two fingers, of which one finger (first finger 2) does not have degrees of freedom in bending and stretching directions and of which the other finger (second finger 3) has a degree of freedom in a rotation direction about the first axis Ax1 and degrees of freedom in bending and stretching direction about the second axis Ax2 and the third axis Ax3, and an example of application of the technology according to the present disclosure to the robot hand H according has been described. However, the applicable robot hand H is not limited thereto. It is possible to adopt any robot hand having a configuration in which a contact area formed between a target object and a finger pad surface upon gripping, that is, a part to be brought into contact with the target object upon gripping is changeable.
The embodiments of the present disclosure have been described in detail above with reference to the drawings. According to the embodiments of the present disclosure, it is possible to achieve both securing of gripping stability and suppression of an increase in size.
The technology according to the present disclosure is not limited to the embodiments described above, and may be modified in a variety of ways, and a combination of modification examples is also possible.
Further, not all of the configurations and operations described in the respective embodiments are indispensable as the configurations and operations of the present disclosure. For example, among the components in the respective embodiments, components not described in the independent claim indicating the most significant concepts of the present disclosure are to be understood as optional components.
Terms used throughout this specification and the appended claims should be construed as “non-limiting” terms. For example, the term “including” or “included” should be construed as “not limited to what is described as being included”. The term “having” should be construed as “not limited to what is described as being had”.
The terms used herein are used merely for the convenience of description and include terms that are not used to limit the configuration, the operation, and the like. For example, the terms such as “right”, “left”, “up”, and “down” only indicate directions in the drawings being referred to. In addition, the terms “inside” and “outside” only indicate a direction toward the center of a component of interest and a direction away from the center of a component of interest, respectively. The same applies to terms similar to these and to terms with the similar purpose.
The technology according to the present disclosure may have the following configurations. According to the technology according to the present disclosure having the following configurations, it is possible to achieve both securing of gripping stability and suppression of an increase in size. Effects attained by the technology according to the present disclosure are not necessarily limited to the effects described herein, but may include any of the effects described in the present disclosure.
(1)
A control device of a robot hand, the robot hand including a first finger and a second finger of which finger pad surfaces are opposed to each other, the control device including:
The control device of the robot hand according to (1), further including a plurality of sensors disposed at different parts of the robot hand, in which
The control device of the robot hand according to (2), in which
The control device of the robot hand according to any one of (1) to (3), further including a palm section, in which
The control device of the robot hand according to any one of (1) to (3), in which
The control device of the robot hand according to (5), in which the hand controller changes parts to be brought into contact with the target object upon gripping, of the palm section, and the distal phalanx section and the middle phalanx section of the second finger in accordance with the selected operation mode.
(7)
The control device of the robot hand according to (5) or (6), further including a first sensor included in the distal phalanx section of the second finger, and a second sensor included in the middle phalanx section of the second finger, in which
The control device of the robot hand according to (7), in which the first sensor has higher resolution than the second sensor.
(9)
The control device of the robot hand according to (5) or (6), further including a first sensor included in the distal phalanx section of the second finger, and a second sensor included in the middle phalanx section of the second finger, in which
The control device of the robot hand according to (9), in which the second sensor has a higher load range than the first sensor.
The control device of the robot hand according to any one of (5) to (10), in which the operation mode selector selects the first operation mode in a case where a dimension of the target object is smaller than a preset reference dimension, and selects the second operation mode in a case where the dimension of the target object is larger than the reference dimension.
(12)
The control device of the robot hand according to (11), in which the reference dimension is a possible maximum value of a distance between the ends of the fingertip section of the first finger and the distal phalanx section of the second finger in a state in which the fingertip section of the first finger and the distal phalanx section of the second finger are located on a same plane perpendicular to a central axis of the palm section.
(13)
The control device of the robot hand according to (11), in which the reference dimension is a distance determined in a direction parallel to a central axis of the palm section between a tip of a fingertip section of the first finger and a distal surface of the palm section.
(14)
The control device of the robot hand according to any one of (11) to (13), in which the hand controller first brings the finger pad surface of the first finger into contact with the target object in the first operation mode.
(15)
The control device of the robot hand according to (14), in which in the first operation mode, the hand controller brings the finger pad surface of the first finger into contact with the target object, and thereafter brings the distal phalanx section of the second finger and a fingertip section of the first finger close to each other on a same plane to bring the distal phalanx section of the second finger into contact with the target object.
(16)
The control device of the robot hand according to (14) or (15), in which
The control device of the robot hand according to any one of (11) to (16), in which in the second operation mode, the hand controller first brings a distal surface of the palm section into contact with the target object.
(18)
The control device of the robot hand according to (17), in which in the second operation mode, after the hand controller brings the distal surface of the palm section into contact with the target object, the hand controller brings the finger pad surface of the first finger into contact with the target object, and thereafter, further brings the finger pad surface of the second finger into contact with the target object.
(19)
The control device of the robot hand according to (18), in which in the second operation mode, after the hand controller brings the finger pad surface of the first finger into contact with the target object, the hand controller closes the second finger to surround the target object by the second finger.
(20)
An operation method of a robot hand, the robot hand including a first finger and a second finger of which finger pad surfaces are opposed to each other, the operation method including:
This application claims the benefit of Japanese Priority Patent Application JP2020-112136 filed with Japan Patent Office on Jun. 29, 2020, the entire contents of which are incorporated herein by reference.
It should be understood by those skilled in the art that various modifications, combinations, sub-combinations, and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-112136 | Jun 2020 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/018720 | 5/18/2021 | WO |
