Robot hand device, robot device, and gripping method

Abstract

Provided is a robot hand device that can connect to a robot arm, said robot hand device comprising: a plurality of finger parts that can grip an object; a drive part that drives a driven part of at least one finger part from among the plurality of finger parts in order to cause the plurality of finger parts to grip the object; and a force increasing part that applies force to at least one finger part from among the plurality of finger parts in order to increase the gripping force on the object. Thus, the gripping force on the object can be increased without increasing the size of the robot hand or particularly increasing the complexity thereof.

Description

Robot hand device, robot device, and gripping method

[0001] The present invention relates to a robot hand device, a robot device, and a method for gripping an object using the robot hand device.

[0002] Robot devices equipped with robot hands (end effectors) are used to grasp various objects. Also, in order to stably grasp an object, robot devices are used that use image information of the object to determine a grasping method appropriate for the object (see, for example, Patent Document 1). In such technology, it is desirable to be able to increase the grasping force of the robot hand on an object without increasing the size or complexity of the robot hand.

[0003] Special Publication No. 2020-532440

[0004] According to a first aspect of the present invention, there is provided a robot hand device connectable to a robot arm, the robot hand device comprising: a plurality of finger portions capable of grasping an object; a drive unit that drives a driven portion of at least one of the plurality of finger portions to cause the plurality of finger portions to grasp the object; and a force amplifier unit that applies force to at least one of the plurality of finger portions to increase the gripping force with which the object is grasped. According to a second aspect, there is provided a robot device comprising the robot hand device according to the first aspect and an arm unit that drives the robot hand device.

[0005] According to a third aspect, there is provided a method for grasping an object using a plurality of finger portions of a robot hand device, the method including: using a drive unit to drive a driven portion of at least one of the plurality of finger portions to grasp the object with the plurality of finger portions; and using a force amplifier unit to apply force to at least one of the plurality of finger portions to increase the grasping force on the object.

[0006] 1 is a perspective view showing a robot device according to an example embodiment; (A) is a cross-sectional view showing a robot hand; (B) is a cross-sectional view showing a state in which a workpiece is gripped by the fingers of the robot hand; (C) is a cross-sectional view showing a state in which the fingers have been released from the workpiece; and (D) is a cross-sectional view showing a state in which the fingers are gradually opened.

[0023] FIG. 1 is a diagram showing an example of a control device for the robot device and the robot hand; (A) is a flowchart showing an example of a method for calculating the attractive force of a magnetic body; and (B) is a flowchart showing an example of a method for gripping a workpiece with the robot hand. (A), (B), (C), and (D) are front views showing robot hands according to first, second, third, and fourth modifications, respectively; (A) and (B) are front views showing robot hands according to fifth and sixth modifications, respectively; and (C) and (D) are partially cut-away front views showing a robot hand according to a seventh modification; (A) and (B) are front views showing robot hands according to eighth and ninth modifications, respectively.

[0007] An example of an embodiment will be described below with reference to FIGS. 1 to 4. FIG. 1 shows an articulated robotic device 2 according to this embodiment. Note that the robotic device 2 is not limited to an articulated type, and any other robotic device configuration, such as a horizontal articulated type (SCARA type), can be used. In FIG. 1, as an example, the X and Y axes are taken as being parallel to and orthogonal to the installation surface of the robotic device 2, and the Z axis is taken as being perpendicular to the installation surface. The installation surface is a substantially horizontal plane, and the direction above the installation surface (the direction opposite to the vertical direction) is the positive direction of the Z axis. The coordinate system consisting of positions on the X, Y, and Z axes is referred to as the robot coordinate system (X, Y, Z).

[0008] In FIG. 1 , the robot device 2 includes a robot main body 4, a robot hand 6 connected to the robot main body 4, a control device 10 that controls the operation of the robot device 2, and a control device 12 that controls the operation of the robot hand 6. The robot hand 6 can also be called an end effector. As an example, the robot hand 6 has two fingers 40A and 40B, as described below, and therefore the robot hand 6 will be referred to as a two-fingered gripper 6 below. Note that a multi-fingered gripper having three or more fingers can also be used instead of the two-fingered gripper 6. The robot main body 4 includes a base 14, a rotating unit 16 connected to the base 14, and a first robot arm 18A, a second robot arm 18B, and a third robot arm 18C that are connected to the rotating unit 16 so as to be displaceable in sequence. The two-fingered gripper 6 is connected to a tip 20A of the third robot arm 18C.

[0009] As an example, the rotation angle θ1 of the rotating unit 16 around an axis parallel to the Z axis can be controlled, the swing angle φ1 of the first robot arm 18A can be controlled, the swing angle φ2 of the second robot arm 18B can be controlled, and the swing angle φ3 of the third robot arm 18C and the swing angle θ2 of the tip end 20A (two-finger gripper 6) around an axis parallel to the Z axis can be controlled. The third robot arm 18C also has a rotating unit 20C that changes the rotation angle θ2 of the tip end 20A and a tilting drive unit 20B that changes the swing angle φ3. The rotating unit 20C and the tilting drive unit 20B each have a drive motor and an encoder that detects the rotation angle. The rotating unit 16 and the other robot arms 18A and 18B also have drive motors and encoders. Therefore, the two-finger gripper 6 attached to the third robot arm 18C can be controlled in terms of four degrees of freedom (including angle), including at least the position in the X direction (direction along the X axis; the same applies below), the Y direction, the Z direction, and the rotation angle around the Z axis.

[0010] The origin of the robot coordinate system (X, Y, Z) is, for example, the center of the base unit 14, but the origin can be set or changed to any position. As an example, the two-fingered gripper 6 is driven by the rotating unit 16 and robot arms 18A to 18C (hereinafter referred to as robot arms 18A to 18C, etc.) so as to move parallel to the Z axis. Note that, because the robot device 2 has at least five encoders, it is also possible to control the position of the two-fingered gripper 6 with three degrees of freedom and the angle with two degrees of freedom. Furthermore, instead of the robot device 2, the two-fingered gripper 6 and the like may be attached to a robot device (not shown) that is capable of controlling the position with three degrees of freedom and the angle with three degrees of freedom.

[0011] The robot apparatus 2 also includes an imaging device 22 and a lighting device (not shown). As an example, the imaging device 22 is provided on the ceiling of the room in which the robot apparatus 2 is installed. However, the imaging device 22 may also be provided on the side of the room, at a measurement position on the installation surface of the robot apparatus 2, or on the robot arm. In this case, multiple imaging devices may be provided so that the workpiece gripped by the two-finger gripper 6 can be constantly observed. Furthermore, the imaging device 22 may also be provided on the side of the robot arm 18C or the side of the two-finger gripper 6. As an example, the imaging device 22 is a camera that captures ordinary two-dimensional images, and its focal position is set, for example, near the placement surface FL on which the workpiece to be gripped by the two-finger gripper 6 is placed, and its focal depth is set relatively deep. The imaging device 22 may also include an autofocus lens. However, a stereo camera or the like may also be used as the imaging device 22.

[0012] The two-finger gripper 6 of this embodiment has two fingers 40A, 40B that can be driven to open and close, and a workpiece 48 as a processing object is gripped between the tips of the fingers 40A, 40B. That is, by closing the fingers 40A, 40B, the workpiece can be gripped or supported between the tips of the fingers 40A, 40B. Furthermore, by opening the fingers 40A, 40B, the fingers 40A, 40B can be detached from the workpiece. As an example, the workpiece 48 is a thin cable with a connector at one end 48a, but any object such as a bolt 50 can be gripped as the workpiece. As such, the shape and size of the workpiece are arbitrary as long as it has a grippable portion. Furthermore, the workpiece may be, for example, a long string-like or cable-like object, as long as the diameter of the cross-sectional shape can be gripped by the two-finger gripper 6.

[0013] Note that one of the fingers 40A, 40B, 40A, may be fixed, and only the other finger 40B may be movable. That is, the fingers 40A, 40B may be capable of opening and closing relative to each other. Furthermore, when a multi-fingered gripper is used instead of the two-fingered gripper 6, at least one of the three or more fingers may be movable, and the other fingers may be fixed.

[0014] 2A to 2D each show the two-fingered gripper 6 in FIG. 1. Hereinafter, for convenience of explanation, the direction in which the finger portions 40A and 40B of the two-fingered gripper 6 open and close will be described as a direction parallel to the Y axis (Y direction). The fingers 40A and 40B may open and close in any direction. FIG. 2A shows the fingers 40A and 40B in a closed state. In FIG. 2A, the two-fingered gripper 6 includes a joint portion 30 joined to the lower end of the tip portion 20A of the robot arm 18C, an actuator portion 32 connected to the joint portion 30, and a pair of fingers 40A and 40B that are opened and closed by the actuator portion 32.

[0015] The joint 30 is fixed to the tip end 20A by, for example, a movable claw mechanism 20Aa. The joining method of the joint 30 may be other mechanical methods (e.g., fixing with a screw or a leaf spring) or electrical methods (e.g., fixing with an electromagnet). The claw mechanism 20Aa is not shown in FIG. 2(C) and subsequent figures. Furthermore, the joint 30 is provided with connection parts (not shown) such as electrical wiring, compressed air piping, and / or vacuum suction piping, as needed. The joint 30 is provided with positioning parts (not shown) such as multiple protrusions or recesses so that the position and rotation angle relative to the tip end 20A are predetermined.

[0016] The actuation unit 32 of the two-finger gripper 6 also includes a drive shaft 38 parallel to the Y direction (opening / closing direction), a motor 34 that rotates the drive shaft 38, and an encoder 36, such as a rotary encoder, that detects the rotation angle of the motor 34. As an example, a right-handed screw 38a and a left-handed screw 38b are formed on the right and left halves of the drive shaft 38, respectively. Driven portions (threaded portions) 40Aa and 40Ba of the finger portions 40A and 40B are threadedly engaged with the left-handed screw 38b and the right-handed screw 38a, respectively. When the drive shaft 38 is rotated by the motor 34, the finger portions 40A and 40B move in opposite directions along the Y direction, allowing the finger portions 40A and 40B to open and close.

[0017] Furthermore, the control device 12 (see FIG. 3 ) for the two-finger gripper 6 determines the spacing (or position) between the finger portions 40A, 40B from the detection value of the encoder 36, and drives the motor 34 based on this spacing, thereby controlling the spacing (or position) between the finger portions 40A, 40B. The configuration of the drive mechanism for the finger portions 40A, 40B is arbitrary. For example, the finger portions 40A, 40B may be driven individually in the Y direction using separate motors. Furthermore, the fingers 40A, 40B may be driven using a linear motor and a linear encoder. Furthermore, instead of the two-finger gripper 6, a robot hand may be used in which the tips of the fingers 40A, 40B support the movable parts of a tool, such as tweezers, for gripping an object.

[0018] When the motor 34 is driven in a predetermined rotational direction to apply a gripping force F1 between the fingers 40A and 40B to grip the workpiece 48, a force (-F1) in the -Y direction acts on the finger 40A, and a force (F) in the +Y direction acts on the finger 40B (see FIG. 2B). Conversely, when the motor 34 is driven in the reverse rotational direction to apply a force (F1') in the +Y direction on the finger 40A, and a force (-F1') in the -Y direction acts on the finger 40B, a separation force (hereinafter referred to as separation force) F1' acts between the fingers 40A and 40B. In this case, the maximum value of the gripping force F1 of the fingers 40A and 40B generated by the motor 34 is substantially equal to the maximum value of the separation force F1' of the fingers 40A and 40B generated by the motor 34.

[0019] Furthermore, in the two-finger gripper 6 of this embodiment, suction portions 40Ab, 40Bb are provided with a narrow gap in the Y direction between the driven portions 40Aa, 40Ba of the fingers 40A, 40B and the gripping portions 40Ac, 40Bc at the tips of the fingers 40A, 40B for gripping a workpiece 48. In this case, the gap between the suction portions 40Ab, 40Bb is set narrower in the Y direction than the gap between the gripping portions 40Ac, 40Bc at the tips of the fingers 40A, 40B. Furthermore, the gap between the driven portions 40Aa, 40Ba is set wider than the gap between the suction portions 40Ab, 40Bb, so that a predetermined gap remains between the driven portions 40Aa, 40Ba even when the suction portions 40Ab, 40Bb are in close contact with each other. 2(A), with the suction portions 40Ab, 40Bb in close contact with each other, the distance between the gripping portions 40Ac, 40Bc of the fingers 40A, 40B is set to be slightly narrower than the width of the workpiece 48 to be gripped by the two-finger gripper 6. Therefore, as shown in FIG. 2(B), by opening the fingers 40A, 40B so that a certain distance is created between the suction portions 40Ab, 40Bb, the workpiece 48 can be gripped between the gripping portions 40Ac, 40Bc.

[0020] Furthermore, magnetic bodies 42A and 42B are embedded inside the central attraction portions 40Ab and 40Bb of the fingers 40A and 40B to generate an attractive force (an example of an attractive force) between the attraction portions 40Ab and 40Bb. The magnetic bodies 42A and 42B are, for example, permanent magnets with polarities that attract each other. In this case, the fingers 40A and 40B may be formed from, for example, a non-magnetic material (e.g., aluminum, copper, non-magnetic stainless steel, etc.). The attractive force F2 between the magnetic bodies 42A and 42B (see FIG. 2B) reaches a maximum value F2max when the distance between the attraction portions 40Ab and 40Bb is zero. Furthermore, the wider the distance between the attraction portions 40Ab and 40Bb, the smaller the attractive force F2. 2B, when the workpiece 48 is held between the gripping portions 40Ac and 40Bc of the fingers 40A and 40B, the workpiece 48 is held by a gripping force F3 which is the sum of the gripping force F1 generated in the fingers 40A and 40B by the motor 34 and the attractive force F2 of the magnetic bodies 42A and 42B. That is, the following equation is established: F3=F1+F2 (1)

[0021] By providing the magnetic bodies 42A and 42B in this manner, the gripping force on the workpiece 48 can be increased with a simple configuration without enlarging the motor 34, i.e., without enlarging the two-finger gripper 6. Therefore, the magnetic bodies 42A and 42B can also be called a force amplifier for increasing the gripping force on the fingers 40A and 40B. However, in order to open the fingers 40A and 40B against the attractive force F2, for example, from the state shown in FIG. 2B or the state shown in FIG. 2A, the maximum value of the gripping force (in this case, the separation force) F1 of the fingers 40A and 40B generated by the motor 34 must be greater than the maximum value of the attractive force F2 of the magnetic bodies 42A and 42B, as shown in the following equation. In other words, the maximum value of the gripping force (attraction force F2) applied to the fingers 40A and 40B by the magnetic bodies 42A and 42B is smaller than the maximum value of the gripping force F1 obtained by the motor 34. Maximum value of F1 > Maximum value of F2 (2)

[0022] The magnetic elements 42A and 42B are preferably positioned so that their attractive force F2 is not blocked by the object to be grasped (workpiece 48). The magnetic elements 42A and 42B are also preferably installed in a manner that avoids mechanical interference with the drive unit (e.g., motor 34) that drives the fingers 40A and 40B. If the sign of the force from the outside of the workpiece 48 toward the center is + and the sign of the force from the center of the workpiece 48 toward the outside is −, then the gripping force is +F1, the release force is −F1, and the attractive force is +F2. Equation (2) indicates that the maximum absolute value of F1 (the gripping force or release force) is greater than the maximum absolute value of F2 (the attractive force). Next, FIG. 3 shows the control device 10 of the robot device 2 and the control device 12 of the two-finger gripper 6. The control devices 10 and 12 may be installed, for example, in an operating device (not shown) located away from the robot body 4 of the robot device 2. Furthermore, the control device 12 may be provided, for example, in the actuation unit 32 of the two-finger gripper 6. In Fig. 3, the control device 10 includes, for example, a control information input / output unit 11A that inputs and outputs control information (such as the type and position of the object to be processed) to and from an operator, a main control unit 11B that transmits and receives control information to and from the control device 12 of the two-finger gripper 6 and controls the operation of the entire device, and a coordinate calculation unit 11C that processes the detection results of at least five-axis encoders that detect the movements of the robot arms 18A to 18C, etc., and calculates the coordinates and rotation angle of the tip of the two-finger gripper 6 at the tip of the third robot arm 18C.

[0023] The control device 10 further includes an image processing unit 11D that processes an image signal from an image capturing device 22 on the ceiling of a room in which the robot device 2 is installed to determine, for example, the positional relationship between the tip of the two-finger gripper 6 and an object, an arm control unit 11E that controls the movement of the robot arms 18A-18C based on the processing results of the coordinate calculation unit 11C and the image processing unit 11D, and a memory unit 11F that stores various data. Note that if the image capturing device 22 is provided in the two-finger gripper 6, the image processing unit 11D may be provided in the control device 12 on the two-finger gripper 6 side. The memory unit 11F may include, for example, a storage device such as a hard disk drive (HDD) or a solid state drive (SSD), or a non-volatile memory such as a USB (universal serial bus) memory. The memory unit 11F stores programs and various setting values ​​for the control device 10.

[0024] The control device 12 also includes a hand control unit 13A that exchanges control information between the main control unit 11B and the arm control unit 11E of the control device 10 and controls the operation of the entire two-finger gripper 6, a finger drive unit 13C that drives the motor 34 to open and close the fingers 40A, 40B, and a gap detection unit 13B that processes the detection signal from the encoder 36 to detect the gap and position of the fingers 40A, 40B. The control device 12 also includes a finger gripping force detection unit 13D that detects a reaction force from the workpiece 48 on the fingers 40A, 40B (or a force that offsets the attractive forces of the magnetic bodies 42A, 42B when the fingers 40A, 40B are opened) as a finger gripping force FF (or a finger separation force FF) from the drive current of the motor 34, an attraction force detection unit 13E (described in detail later) that detects an attractive force F2 of the magnetic bodies 42A, 42B, and a memory unit 13F. The configuration of the storage unit 13F is the same as that of the storage unit 11F, and the storage unit 13F stores the programs of the control device 12, various setting values, and the like.

[0025] As an example, when a workpiece 48 is gripped between the fingers 40A and 40B, the motor 34 may be driven using a feedforward method so that the gripping force F1 detected by the finger gripping force detection unit 13D is maintained at a predetermined target value. However, when the workpiece 48 is not between the fingers 40A and 40B, the load on the motor 34 is small, and therefore the current flowing through the motor 34 (detected gripping force) is small. The finger gripping force detection unit 13D may be, for example, a strain gauge or a pressure sensor provided on the fingers 40A and 40B. The control information input to the hand control unit 13A includes, for example, a command to start gripping the workpiece by the fingers 40A and 40B and a command to release the gripping. The control information output from the hand control unit 13A to the main control unit 11B includes, for example, information indicating the completion of gripping the workpiece by the fingers 40A and 40B and information indicating the completion of release of the fingers 40A and 40B from the workpiece (completion of grip release).

[0026] Next, an example of the basic operation of the robot device 2 of this embodiment will be described. First, the width of the gripping portions 40Ac, 40Bc of the fingers 40A, 40B shown in FIG. 2A is set wider than the width of the workpiece 48. The two-finger gripper 6 is then driven using the robot arms 18A-18C, etc., to move the gripping portions 40Ac, 40Bc of the fingers 40A, 40B to a position where they can clamp the workpiece 48. The motor 34 is then driven to close the fingers 40A, 40B. After the fingers 40A, 40B come into contact with the workpiece 48, as shown in FIG. 2B, the motor 34 is driven so that the gripping force F1 is maintained at a predetermined value. At this time, the magnetic bodies 42A, 42B apply an attractive force F2 to the fingers 40A, 40B, so that the total gripping force F3 of the fingers 40A, 40B on the workpiece 48 increases to (F1 + F2). As described above, the maximum value of the suction force F2 is smaller than the maximum value of the gripping force F1, so the total gripping force F3 on the workpiece 48 can be increased to less than twice the maximum gripping force of the fingers 40A, 40B generated by the motor 34. Therefore, even if the workpiece 48 is heavy, the workpiece 48 can be gripped without dropping.

[0027] 2C, to release the fingers 40A, 40B from the workpiece 48, the motor 34 is rotated in the reverse direction to apply a release force F5 (>F2) to the fingers 40A, 40B that offsets the attractive force F2 of the magnetic bodies 42A, 42B. This causes the fingers 40A, 40B to open against the attractive force F2 of the magnetic bodies 42A, 42B, allowing the fingers 40A, 40B to release from the workpiece 48. By providing the magnetic bodies 42A, 42B on the fingers 40A, 40B in this manner, the gripping force of the fingers 40A, 40B on the workpiece 48 can be increased with a simple configuration without increasing the size of the two-finger gripper 6. Furthermore, because the maximum value of the attractive force F2 is smaller than the maximum value of the gripping force (release force) F1, the fingers 40A, 40B can open against the attractive force F2 of the magnetic bodies 42A, 42B.

[0028] Next, the attractive force F2 of the magnetic bodies 42A, 42B varies depending on the distance between the fingers 40A, 40B. Therefore, an example of a method for determining the attractive force F2 of the magnetic bodies 42A, 42B according to the distance d between the fingers 40A, 40B (attraction portions 40Ab, 40Bb) and gripping the workpiece 48 so that the sum of the gripping force F1 and the attractive force F2 of the fingers 40A, 40B generated by the motor 34 becomes a target value determined for the workpiece 48 will be described with reference to the flowcharts in Figures 4(A) and (B). First, in order to determine the attractive force F2 of the magnetic bodies 42A, 42B, in the absence of the workpiece 48, as shown in Figure 2(A), the fingers 40A, 40B are closed to bring the attraction portions 40Ab, 40Bb into close contact with each other, and the distance between the fingers 40A, 40B detected by the distance detection portion 13B at this time is preset to 0. Thereafter, the distance d detected by the distance detector 13B is the distance between the suction units 40Ab and 40Bb.

[0029] Then, in step 104, the motor 34 is driven in a direction that opens the fingers 40A, 40B, and the attraction force detection unit 13E detects the attraction force F2 of the magnetic bodies 42A, 42B from the drive current of the motor 34. Furthermore, in step 106, the motor 34 is further driven to add a small distance δd to the distance d between the fingers 40A, 40B. Then, in step 108, it is determined whether the distance d has reached a predetermined upper limit. If the distance d has not reached the upper limit, steps 104 and 106 are repeated. In this case, as shown in FIG. 2(D), for each distance d between the fingers 40A, 40B, the attraction force F4 by the magnetic bodies 42A, 42B is calculated as the separation force F4 in the opening direction of the fingers 40A, 40B by the motor 34. The attraction force F4 is detected every time the distance d changes by δd. In step 108, if the distance d reaches its upper limit, the process proceeds to step 110, where the attraction force detection unit 13E calculates the attraction force F4 of the magnetic bodies 42A and 42B as a function of the distance d between the fingers 40A and 40B, for example by interpolation. The function is stored in the memory unit 13F.

[0030] Thereafter, when gripping a workpiece 48 with the fingers 40A and 40B of the two-fingered gripper 6, in step 122 of FIG. 4B, the robot arms 18A-18C, etc. are driven to move the two-fingered gripper 6 (robot hand) to a position (gripping position) for gripping the workpiece 48. Then, the fingers 40A and 40B are closed, and the workpiece 48 is gripped between the gripping portions 40Ac and 40Bc of the fingers 40A and 40B, as shown in FIG. 2B. Then, in step 126, almost in parallel with step 124, an attractive force F2 is applied to the workpiece 48 by the magnetic bodies 42A and 42B. Furthermore, in step 128, the hand control unit 13A obtains the distance d between the fingers 40A and 40B from the detection result of the distance detection unit 13B, and calculates the attractive force F2 by the magnetic bodies 42A and 42B from the distance d and a function stored in the memory unit 13F. Furthermore, the hand control unit 13A adds the suction force F2 to the gripping force F1 of the fingers 40A, 40B determined by the finger gripping force detection unit 13D to determine the total value F3 of the gripping forces applied to the workpiece 48.

[0031] Then, in step 130, the hand control unit 13A determines whether the total gripping force F3 is within a predetermined tolerance range, for example, for the workpiece 48. If the total gripping force F3 is within the tolerance range, the process proceeds to step 134, where the robot arms 18A-18C are driven to move the two-fingered gripper 6 (robot hand) to a transfer position for the workpiece 48. Then, in step 136, the fingers 40A, 40B are opened to release the fingers 40A, 40B from the workpiece 48. On the other hand, if the total gripping force F3 for the workpiece 48 is not within the tolerance range in step 130, the process proceeds to step 132, where the gripping force F1 of the fingers 40A, 40B, generated by the motor 34, is controlled (increased or decreased) so that the total gripping force F3 is within the tolerance range. Note that the operations from steps 124 to 132 are actually performed in a fairly short time. Then, the process proceeds to step 134.

[0032] According to this gripping method, the attractive force F2 of the fingers 40A, 40B is calculated according to the distance d between the fingers 40A, 40B, and the total gripping force F3 applied to the workpiece 48 is calculated, and this total value F3 is kept within an allowable range. Therefore, the workpiece 48 can be gripped with a gripping force that is greater than the gripping force obtained by the motor 34 and that is appropriate for the workpiece 48. Note that when multiple workpieces 48 are continuously moved from one location to another, the total gripping force F3 calculated in step 128 for the first workpiece 48 may be used, and the gripping force by the motor 34 set in step 130 or step 132 may be used as the gripping force by the motor 34 for the second and subsequent workpieces 48.

[0033] As described above, the two-fingered gripper 6 of this embodiment is a robot hand device connectable to the robot arms 18A to 18C, etc., and includes fingers 40A, 40B capable of gripping a workpiece 48 (object), a motor 34 (drive unit) that drives driven portions 40Aa, 40Ba of the fingers 40A, 40B to grip the workpiece 48 with the fingers 40A, 40B, and magnetic bodies 42A, 42B (force booster units) that apply an attractive force F2 to the fingers 40A, 40B to increase the gripping force on the workpiece 48. The robot device 2 of this embodiment also includes the two-fingered gripper 6 (robot hand), robot arms 18A to 18C, etc. (arm units) that drive the two-fingered gripper 6, and a control device 10 that controls the robot arms 18A to 18C, etc.

[0034] The gripping method of this embodiment also includes step 124 of driving driven portions 40Aa, 40Ba of fingers 40A, 40B using motor 34 (drive unit) to cause fingers 40A, 40B to grip workpiece 48, and step 126 of applying attractive force F2 to fingers 40A, 40B using magnetized bodies 42A, 42B (force-increasing units) to increase the gripping force on workpiece 48. According to this embodiment, the gripping force is applied to fingers 40A, 40B using magnetized bodies 42A, 42B embedded in fingers 40A, 40B. Therefore, the gripping force of two-fingered gripper 6 on workpiece 48 can be increased without increasing the size of motor 34, i.e., without increasing the size of two-fingered gripper 6 (robot hand) or making two-fingered gripper 6 too complex.

[0035] Next, the above-described embodiment can be modified as follows. Note that in FIGS. 5A to 6D, which will be referred to below, parts corresponding to those in FIGS. 1 and 2A to 2D are designated by the same or similar reference numerals, and detailed descriptions thereof will be omitted. First, in the above-described embodiment, two fingers 40A and 40B are provided with magnetic bodies 42A and 42B, respectively. As an alternative configuration, for example, finger 40A may be fixed, and only the other finger 40B may be driven by the motor 34. A spring mechanism (a force amplifier) ​​that biases finger 40B toward finger 40A may be provided between the fixed portion provided on the side of the actuation unit 32 and finger 40B. Alternatively, the robot hand may be provided with three or more fingers, at least one of which may be driven by a motor, and a gripping force (attraction force or repulsion force) may be applied to at least one of the three or more fingers from the force amplifier.

[0036] In the above-described embodiment, the distance between the fingers 40A and 40B is determined from the detection result of the encoder 36. As an alternative configuration, for example, mark members on which predetermined identification marks are formed may be attached to parts of the fingers 40A and 40B, and the identification marks may be captured by the imaging device 22, for example, and the captured image may be processed to determine the distance between the identification marks, and ultimately the distance between the fingers 40A and 40B. This may allow the distance to be determined more accurately.

[0037] Next, in the above-described embodiment, the fingers 40A, 40B are provided with magnetic bodies 42A, 42B. Alternatively, as shown in FIG. 5A , a first modified example of a two-finger gripper 6A may be provided with a magnetic body 44 (e.g., iron, nickel, cobalt, ferrite, etc.) on one finger 40A and a magnetic body 42 (e.g., a permanent magnet) on the other finger 40B. The magnetic body may be a ferromagnetic body. In this configuration, an attractive force is generated between the magnetic body 42 and the magnetic body 44, thereby increasing the gripping force on the workpiece 48, as in the above-described embodiment. In this case, the fingers 40A, 40B may be formed from a non-magnetic body. Furthermore, for example, the magnetic body 44 may be omitted, and one finger 40A may be formed from a magnetic body. In this case, the finger 40A is used instead of a magnetic body. Furthermore, the magnetic bodies 42 and 44 may be omitted, and one finger 40A may be formed from a magnetic body, and the other finger 40B may be formed from a magnetic body or a magnetic body.

[0038] 5B , a two-finger gripper 6B according to a second modification may be configured such that one finger 40A is provided with a magnetic body 44, the other finger 40B is provided with an electromagnet 46 having a magnetic body 46a and a coil 46b wound around it, and a current control unit 13G for controlling the current supplied to the coil 46b is provided in the actuation unit 32 (or in the control device 12 shown in FIG. 3 ). Note that the finger 40A may be provided with a magnetized body (e.g., a permanent magnet) or an electromagnet instead of the magnetic body 44. In this two-finger gripper 6B, supplying a predetermined current to the electromagnet 46 generates an attractive force between the electromagnet 46 and the magnetic body 44, thereby increasing the gripping force on a workpiece 48 gripped by the fingers 40A, 40B, as in the above-described embodiment.

[0039] Furthermore, in this modification, by controlling the current supplied to the electromagnet 46 from the current control unit 13G, the attractive force generated between the electromagnet 46 and the magnetic body 44 can be controlled within a range from 0 to a predetermined maximum value. Therefore, when gripping the workpiece 48 with the fingers 40A, 40B, the current supplied to the electromagnet 46 can be increased to set the total gripping force on the workpiece 48 to any value equal to or greater than twice the gripping force applied to the fingers 40A, 40B by the drive units of the fingers 40A, 40B. When releasing the fingers 40A, 40B from the workpiece 48, the current supplied to the electromagnet 46 can be reduced or set to zero, allowing the fingers 40A, 40B to easily open. Furthermore, in this modification, by controlling the current supplied to the electromagnet 46, the gripping force applied to the workpiece 48 can be easily controlled within a wide range depending on the workpiece 48.

[0040] 5C, gripping portions 40Ac, 40Bc of fingers 40A, 40B that grip a workpiece 48 may be provided with anti-slip portions 40Ad, 40Bd with a high coefficient of friction. The anti-slip portions 40Ad, 40Bd may be, for example, a thin layer of a material with a high coefficient of friction such as rubber, a tape with a high coefficient of friction such as vinyl chloride tape, or a layer with minute irregularities on the surface formed by knurling or the like. Note that only one of the anti-slip portions 40Ad, 40Bd may be provided.

[0041] In the embodiment shown in FIG. 2A, the attractive force F2 of the magnetic bodies 42A and 42B is detected using the drive current of the motor 34 that drives the fingers 40A and 40B. In contrast, as shown in FIG. 5D, a two-finger gripper 6D of a fourth modified example, a load sensor 52 may be provided on one of the gripping portions 40Ac (or the other gripping portion 40Bc) of the fingers 40A and 40B. The load sensor 52 may be, for example, a load cell, a force gauge, or a pressure sensor. With the two-finger gripper 6D, the load sensor 52 can directly detect the total gripping force applied to the workpiece 48 by the fingers 40A and 40B. Then, for example, the attractive force of the magnetic bodies 42A and 42B can be accurately determined by subtracting the gripping force applied to the fingers 40A and 40B by the motor 34 shown in FIG. 2A from the total gripping force.

[0042] In the above-described embodiment, the fingers 40A, 40B are provided with force boosting units (such as magnetized bodies 42A, 42B). Alternatively, force boosting mechanisms 54A, 54B may be provided that push the fingers 40A, 40B toward the workpiece 48 from the outside, as shown in a two-finger gripper 6E of a fifth modified example in FIG. 6A . The force boosting mechanisms 54A, 54B, for example, include fixed units 54Ab, 54Bb provided on the side surfaces of the actuator 32 in the opening / closing direction (here, the Y direction), and cylinder units 54Aa, 54Ba that push the finger units 40A, 40B toward the workpiece 48 relative to the fixed units 54Ab, 54Bb. The cylinder units 54Aa, 54Ba apply pressure toward the workpiece 48 to the fingers 40A, 40B, for example, by compressed air or vacuum. The pressure that the cylinder portions 54Aa, 54Ba apply to the fingers 40A, 40B may be a constant value or may be variable.

[0043] According to the two-finger gripper 6E, when the fingers 40A, 40B grip the workpiece 48, the force-increasing mechanisms 54A, 54B apply pressure to the fingers 40A, 40B toward the workpiece 48, thereby increasing the gripping force on the workpiece 48. Furthermore, if the pressure of the cylinder portions 54Aa, 54Ba is constant and is smaller than the gripping force acting on the fingers 40A, 40B by the motor 34, the fingers 40A, 40B can be opened against the pressure by driving the motor 34 in the opposite direction. On the other hand, if the pressure of the cylinder portions 54Aa, 54Ba is variable, when the fingers 40A, 40B grip the workpiece 48, the pressure of the cylinder portions 54Aa, 54Ba can be made larger than the gripping force of the fingers 40A, 40B exerted by the motor 34. When the fingers 40A, 40B are to be removed from the workpiece 48, the pressure of the cylinder portions 54Aa, 54Ba is reduced, so that the fingers 40A, 40B can be easily opened.

[0044] In this modified example, instead of the cylinder portions 54Aa, 54Ba, a mechanism using a compression coil spring to press the finger portions 40A, 40B toward the workpiece 48 relative to the fixed portions 54Ab, 54Bb, or a mechanism using two magnetic bodies with repelling polarities to press the finger portions 40A, 40B toward the workpiece 48 relative to the fixed portions 54Ab, 54Bb, can be used. Furthermore, one of the force-increasing mechanisms 54A, 54B can be omitted. Also, instead of the cylinder portions 54Aa, 54Ba, a cylinder portion that retracts the fingers 40B, 40A toward the fixed portions 54Ab, 54Bb can be used.

[0045] In the above-described embodiment, the fingers 40A, 40B are provided with suction portions 40Ab, 40Bb having steps to narrow the gap between the magnetic bodies 42A, 42B. Alternatively, as shown in a two-finger gripper 6F of a sixth modified example in FIG. 6B , the actuating unit 32 may open and close two elongated, rectangular-prism-shaped fingers 40C, 40D. In this case, as an example, the magnetic bodies 42A, 42B are provided in the longitudinal center of the fingers 40C, 40D. Even in this modified example, when the fingers 40C, 40D are closed to grip the workpiece 48, the magnetic bodies 42A, 42B exert an attractive force on the workpiece 48, thereby enabling a large gripping force on the workpiece 48 with a simple configuration. On the other hand, when the fingers 40C, 40D are released from the workpiece 48, the attractive force of the magnetic bodies 42A, 42B is weaker than in the example of FIG. 2B , for example, and therefore the fingers 40C, 40D can be easily opened.

[0046] Furthermore, as shown in a two-finger gripper 6G of a seventh modified example in FIG. 6C, the tips of the fingers 40C, 40D in FIG. 6B may be provided with counter-action portions 56A, 56B that reverse the opening and closing directions of the fingers 40C, 40D. One end of the counter-action portions 56A, 56B is fixed to the outer surfaces of the fingers 40C, 40D by a bolt B1, and the tips 56Aa, 56Ba of the counter-action portions 56A, 56B are located on the finger 40D side and the finger 40C side, respectively, with respect to a line passing through the centers of the fingers 40C, 40D. In this configuration, when the fingers 40C, 40D are closed in the Y direction, the tips 56Aa, 56Ba of the counter-action portions 56A, 56B open. Therefore, when the tip portions 56Aa, 56Ba are inserted into the inner surface 58a of, for example, a cylindrical workpiece 58 and the fingers 40C, 40D are closed, the tip portions 56Aa, 56Ba open, and the tip portions 56Aa, 56Ba can grip the workpiece 58 from the inside, as shown in Figure 6 (D).

[0047] Furthermore, magnetic bodies 42C, 42D of repulsive polarities are fixed between a fixed portion 54Ab on the side surface of the operating portion 32 and one end of the counter-action portion 56A, and magnetic bodies 42E, 42F of repulsive polarities are fixed between a fixed portion 54Bb on the side surface of the operating portion 32 and one end of the counter-action portion 56B. In this modification, as shown in FIG. 6(D), when the fingers 40C, 40D close with a gripping force F1, an inward repulsive force F2 is applied to the counter-action portions 56A, 56B by the magnetic bodies 42C, 42D, etc. As a result, an outward gripping force F3 is generated at the tip portions 56Aa, 56Ba that grip the workpiece 58 from the inside, and the gripping force F3 increases to (F1 + F2). Thereafter, in order to separate the tip portions 56Aa, 56Ba from the workpiece 58, the fingers 40C, 40D are opened and the tip portions 56Aa, 56Ba are closed. Because the maximum value of the repulsive force F2 is smaller than the maximum value of the gripping force F1, the fingers 40C, 40D can be opened against the repulsive force F2.

[0048] In this modification, a mechanism using electromagnets, a cylinder, or the like can be used instead of the magnetic bodies 42C, 42D and 42E, 42F. Next, a two-finger gripper 6H of an eighth modification shown in FIG. 7A has the same fingers 40C, 40D as the example shown in FIG. 6B. Magnetic bodies 42C, 42D, each having a polarity repelling each other, are fixed between the outer surface of the finger 40C and a fixed portion 54Cb provided on one side of the actuating portion 32, and magnetic bodies 42E, 42F, each having a polarity repelling each other, are fixed between the finger 40D and a fixed portion 54Db provided on the other side of the actuating portion 32. In this modification, when the fingers 40C, 40D are closed by a gripping force F1 generated by the motor 34 (see FIG. 2A), an inward repulsive force (hereinafter also referred to as a repulsive force) F2 is applied by the magnetic bodies 42C, 42D, etc. As a result, the gripping force F3 with which the fingers 40C, 40D grip the workpiece 48 increases to (F1 + F2). After this, the fingers 40C, 40D can be opened to release the fingers 40C, 40D from the workpiece 48. Whether the force applied by the force amplifier is a repulsive force or an attractive force, what is important is that the applied force contains a component that increases the gripping force, and the force generation method, structure, and type of force of the force amplifier are arbitrary.

[0049] Furthermore, as shown in a two-fingered gripper 6I of a ninth modification in FIG. 7B, elastic members 60A and 60B each made of, for example, a compression coil spring and having a repulsive force may be used instead of the magnetic bodies 42C, 42D and 42E, 42F in FIG. 7A. In this modification, the repulsive force F2 from the elastic members 60A and 60B is added to the gripping force F1 from the motor 34 (see FIG. 2A). This increases the gripping force on the workpiece 48 without making the two-fingered gripper 6I too complex. Note that a cylinder device or the like may also be used in place of the elastic members 60A and 60B. Next, the two-fingered grippers 6, 6A, etc. (robot hands) of the above-described embodiment can be attached to the robot arms of any robot device configuration, such as a horizontally articulated (SCARA) type, a parallel link type, or an orthogonal type, in addition to the vertically articulated robot device 2. Furthermore, the robot hand is not limited to the robot device described above, but can also be applied to various robot devices (for example, assembly robots, human-collaborative robots, etc.) that have a joint structure like other robot arms.

[0050] The following aspects of the invention are also described in this specification: 1) A robot hand device connectable to a robot arm, the robot hand device comprising: a plurality of finger portions capable of gripping an object; a drive unit that drives a driven unit of at least one of the plurality of finger portions to cause the plurality of finger portions to grip the object; and a force amplifier unit that applies force to at least one of the plurality of finger portions to increase the gripping force for the object. 2) The robot hand device described in 1, in which the force amplifier unit applies an attractive force between first and second finger portions of the plurality of finger portions. 3) The robot hand device described in 2, in which a maximum value of the attractive force is set to be smaller than a maximum value of the gripping force of the plurality of finger portions exerted by the drive unit. 4) The robot hand device described in 2 or 3, in which the force amplifier unit is provided on the first and second finger portions, and the distance between the portions of the first and second finger portions where the force amplifier units are provided is set to be narrower than the distance between the portions that grip the object. 5) The robot hand device according to any one of 2 to 4, wherein the force amplifying unit has a magnetized body provided in the first finger portion and a magnetized or magnetic body provided in the second finger portion. 6) The robot hand device according to any one of 2 to 4, wherein the force amplifying unit has an electromagnet provided in the first finger portion and a magnetic body provided in the second finger portion. 7) The robot hand device according to any one of 1 to 3, wherein the force amplifying unit has a cylinder portion that pushes or retracts at least one of the plurality of finger portions. 8) The robot hand device according to 1, further comprising a counter-action unit that converts the movement of the plurality of finger portions into an opposite direction, and the force amplifying unit applies a repulsive force or an attractive force between at least one of the plurality of finger portions and a fixed portion connected to the drive unit.9) The robot hand device according to any one of 1 to 8, further comprising: a control unit that controls a gripping force applied to the object by the plurality of finger units driven by the drive unit; and an encoder unit that detects arrangement information of the plurality of finger units, wherein the control unit determines the force to be applied by the force amplifier unit in accordance with the arrangement of the plurality of finger units using the detection result of the encoder unit and driving force information of the drive unit when the object is not being gripped by the plurality of finger units. 10) The robot hand device according to any one of 1 to 9, wherein the plurality of finger units is two, and the force amplifier unit applies force between the two finger units.

[0051] 11) A robot device comprising the robot hand device described in any one of 1 to 10 and an arm unit that drives the robot hand device. 12) A method for grasping an object using multiple finger units of a robot hand device, the method including: using a drive unit to drive a driven unit of at least one of the multiple finger units to cause the multiple finger units to grasp the object; and using a force amplifier unit to apply a force to at least one of the multiple finger units to increase a gripping force on the object. 13) The gripping method described in 12, in which applying a force to the at least one finger unit includes applying an attractive force between first and second finger units of the multiple finger units. 14) The gripping method described in 13, in which a maximum value of the attractive force is set to be smaller than a maximum value of gripping forces of the multiple finger units exerted by the drive unit. 15) The gripping method according to 13 or 14, wherein the force amplifier is provided on the first and second finger portions, and a distance between portions of the first and second finger portions where the force amplifier is provided is set narrower than a distance between portions that grip the object. 16) The gripping method according to any one of 13 to 15, wherein the force amplifier has a magnetized body provided on the first finger portion, and a magnetized body or a magnetic body provided on the second finger portion. 17) The gripping method according to any one of 13 to 16, wherein the force amplifier has an electromagnet provided on the first finger portion, and a magnetic body provided on the second finger portion. 18) The gripping method according to 12, wherein the force amplifier has a cylinder portion that pushes or retracts at least one of the plurality of finger portions. 19) The gripping method described in 12, which includes converting the movement of the multiple finger portions in an opposite direction, and the force multiplier unit applies a repulsive force or an attractive force between at least one finger portion of the multiple finger portions and a fixed portion connected to the drive unit.20) The grasping method according to any one of claims 12 to 19, comprising: detecting arrangement information of the plurality of finger portions; and determining a force to be applied by the force amplifier in accordance with the arrangement of the plurality of finger portions using the arrangement information of the plurality of finger portions and driving force information of the driver in a state where the object is not grasped by the plurality of finger portions. 21) The grasping method according to any one of claims 12 to 20, wherein the number of the plurality of finger portions is two, and the force amplifier applies a force between the two finger portions.

[0052] 2...Robot device, 6, 6A to 6G...Two-finger gripper (robot hand), 10...Control device of robot device, 12...Control device of robot hand, 16...Rotating unit, 18A to 18C...Robot arm, 22...Imaging device, 32...Actuating unit, 34...Motor, 38...Drive shaft, 40A, 40B...Fingers, 42, 42A, 42B...Magnetic body, 44...Magnetic body, 46...Electromagnet, 48...Work

Claims

1. A robot hand device connectable to a robot arm, comprising: a plurality of finger portions capable of grasping an object; a drive unit that drives a driven portion of at least one of the plurality of finger portions to cause the plurality of finger portions to grasp the object; and a force multiplier unit that applies force to at least one of the plurality of finger portions to increase the gripping force applied to the object.

2. The robot hand device according to claim 1, wherein the force multiplier applies an attractive force between a first and a second finger portion of the plurality of finger portions.

3. A robot hand device as described in claim 2, wherein the maximum value of the attractive force is set to be smaller than the maximum value of the gripping force of the multiple finger portions exerted by the drive unit.

4. A robot hand device as described in claim 2, wherein the force-intensifying portion is provided on the first and second finger portions, and the spacing between the portions of the first and second finger portions where the force-intensifying portion is provided is set narrower than the spacing between the portions that grasp the object.

5. A robot hand device as described in claim 2, wherein the force multiplier section has a magnetized body provided in the first finger section and a magnetized body or magnetic body provided in the second finger section.

6. A robot hand device according to claim 2, wherein the force multiplier comprises an electromagnet provided on the first finger portion and a magnetic body provided on the second finger portion.

7. The robot hand device according to claim 1, wherein the force multiplier has a cylinder portion that pushes or retracts at least one of the plurality of finger portions.

8. A robot hand device as described in claim 1, further comprising an inverse action unit that converts the movement of the plurality of finger portions into an opposite direction, and the force multiplier unit applies a repulsive force or an attractive force between at least one of the plurality of finger portions and a fixed unit connected to the drive unit.

9. A robot hand device as described in claim 1, comprising: a control unit that controls the gripping force applied to the object by the multiple finger sections driven by the drive unit; and an encoder unit that detects arrangement information of the multiple finger sections, wherein the control unit determines the force applied by the force amplifier unit in accordance with the arrangement of the multiple finger sections using the detection result of the encoder unit and driving force information of the drive unit when the object is not gripped by the multiple finger sections.

10. The robot hand device according to claim 1, wherein the number of said finger portions is two, and the force multiplier applies force between the two finger portions.

11. A robot device comprising: a robot hand device according to any one of claims 1 to 10; and an arm section that drives the robot hand device.

12. A method for grasping an object using multiple finger portions of a robot hand device, comprising: using a drive unit to drive a driven portion of at least one of the multiple finger portions in order to cause the multiple finger portions to grasp the object; and using a force multiplier unit to apply force to at least one of the multiple finger portions in order to increase the grasping force applied to the object.

13. The method of claim 12, wherein applying a force to the at least one finger portion comprises applying an attractive force between first and second finger portions of the plurality of finger portions.

14. The gripping method according to claim 13, wherein the maximum value of the attractive force is set to be smaller than the maximum value of the gripping forces of the plurality of finger portions exerted by the drive section.

15. The gripping method according to claim 13, wherein the force multiplier is provided on the first and second finger portions, and the spacing between the portions of the first and second finger portions where the force multiplier is provided is set narrower than the spacing between the portions that grip the object.

16. The gripping method according to claim 13, wherein the force multiplier portion has a magnetized body provided in the first finger portion and a magnetized or magnetic body provided in the second finger portion.

17. The gripping method according to claim 13, wherein the force multiplier comprises an electromagnet provided on the first finger portion and a magnetic body provided on the second finger portion.

18. The gripping method according to claim 12, wherein the force multiplier has a cylinder portion that pushes or retracts at least one of the plurality of finger portions.

19. The gripping method according to claim 12, further comprising converting the movement of the plurality of finger portions in an opposite direction, wherein the force multiplier applies a repulsive force or an attractive force between at least one of the plurality of finger portions and a fixed portion connected to the drive unit.

20. A gripping method as described in claim 12, comprising: detecting arrangement information of the plurality of finger portions; and, when the object is not gripped by the plurality of finger portions, using the arrangement information of the plurality of finger portions and driving force information of the driving portion, determining a force applied by the force multiplier portion in accordance with the arrangement of the plurality of finger portions.

21. A gripping method according to any one of claims 12 to 20, wherein the number of said finger portions is two, and the force multiplier applies force between the two finger portions.

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