Hand

Abstract

A hand 2 comprises: a hand body 3; and a plurality of fingers 4 which are provided to the hand body 3 and which perform opening and closing motions. Each of the plurality of fingers 4 has an endless belt 5 which is wound on at least a tip of the finger 4, rotationally driven, and brought in contact with a workpiece W. The finger 4 can be elastically displaced in a first direction X in which the plurality of fingers 4 are opened and closed, and can be elastically displaced in a second direction Y in which the plurality of fingers 4 advance and retract relative to the hand body 3.

Description

hand

[0001] The technology disclosed herein relates to a hand.

[0002] Hands with fingers having rotationally driven belts are known. For example, a hand described in Patent Document 1 has two fingers. Each finger has a rotationally driven belt. This hand pulls a workpiece between the two fingers by rotating the belt.

[0003] JP 2014-24143 A

[0004] When a workpiece is pulled between multiple fingers using a belt, the workpiece is pulled in by fitting the workpiece appropriately between the tips of the multiple fingers. If the positional accuracy of the tips of the multiple fingers relative to the workpiece is low, there is a risk that the workpiece cannot be pulled between the multiple fingers. Furthermore, if the spacing between the multiple fingers is not set appropriately relative to the workpiece, there is a risk that the workpiece cannot be pulled between the multiple fingers. By improving the accuracy of the position and spacing of the multiple fingers, the workpiece can be pulled in appropriately. However, increasing the accuracy of the position and spacing of the multiple fingers increases the difficulty of control and slows down the control operation.

[0005] The technology disclosed herein has been made in view of the above points, and its purpose is to provide a hand that can facilitate control for pulling in a workpiece.

[0006] The hand of the present disclosure comprises a hand body and a plurality of fingers provided on the hand body that open and close, each of the plurality of fingers having an endless belt that is wrapped around at least the tip of the finger, is driven to rotate, and comes into contact with the workpiece, and the fingers are elastically displaceable in a first direction in which the plurality of fingers open and close, and are elastically displaceable in a second direction in which they move toward and away from the hand body.

[0007] The hand can facilitate control for pulling in the workpiece.

[0008] FIG. 1 is a schematic diagram showing the configuration of a robot system. FIG. 2 is a front view of a hand. FIG. 3 is a bottom view of the hand. FIG. 4 is a cross-sectional view of the hand taken along line IV-IV in FIG. 3. FIG. 5 is a cross-sectional view of the hand taken along line V-V in FIG. 3. FIG. 6 is a cross-sectional view of the hand taken along line VI-VI in FIG. 4. FIG. 7 is a perspective view of a finger. FIG. 8 is a side view of a finger. FIG. 9 is a cross-sectional view of the finger taken along line IX-IX in FIG. 8. FIG. 10 is a front view of a finger body and a support. FIG. 11 is a cross-sectional view of the finger taken along line XI-XI in FIG. 8. FIG. 12 is a perspective view of a finger taken from a different angle than in FIG. 7. FIG. 13 is a front view of a finger. FIG. 14 is a front view of a finger with the finger body displaced toward the retreating side in the second direction. FIG. 15 is a diagram showing a schematic hardware configuration of a control device. FIG. 16 is a block diagram showing the configuration of a control system for a processor. FIG. 17 is a flowchart of a pick-and-place process. Fig. 18 is a schematic diagram for explaining an example of a search operation of the hand. Fig. 19 is a schematic diagram for explaining a case where the retraction of the workpiece is successful. Fig. 20 is a schematic diagram for explaining the state of the fingers when the workpiece is retracted. Fig. 21 is a schematic diagram for explaining another example of a search operation of the hand. Fig. 22 is a schematic diagram for explaining another example of a search operation of the hand.

[0009] Exemplary embodiments will be described in detail below with reference to the accompanying drawings. Fig. 1 is a schematic diagram showing the configuration of a robot system 1000. In this disclosure, "parallel," "orthogonal," "same," "coincident," "simultaneous," or "center" includes not only "strictly parallel," "orthogonal," "same," "coincident," "simultaneous," or "center," but also "substantially parallel," "orthogonal," "same," "coincident," "simultaneous," or "center."

[0010] The robot system 1000 includes a hand 2, a robot arm 10 to which the hand 2 is connected, and a control device 100 that controls the hand 2 and the robot arm 10. The hand 2 and the robot arm 10 are included in a robot 1. That is, the robot system 1000 includes a robot 1 that includes the hand 2 and the robot arm 10. The robot system 1000 picks up a workpiece W using the hand 2. In this example, the robot system 1000 picks up one workpiece W from among a plurality of workpieces W stacked in a container 19. However, the robot system 1000 may also pick up one specific workpiece W that is placed independently.

[0011] The robot 1 is, for example, an industrial robot. The robot 1 operates a hand 2 by a robot arm 10. The hand 2 is one of so-called end effectors. The hand 2 grips a workpiece W.

[0012] The robot arm 10 is configured to operate three-dimensionally. Specifically, the robot arm 10 is configured to perform operations including translation with at least three degrees of freedom. In this example, the robot arm 10 is a vertically articulated robot arm. The robot arm 10 is supported on a base 13. The robot arm 10 has a plurality of links, a plurality of joints connecting the plurality of links, and servo motors that rotate the plurality of joints.

[0013] In detail, the robot arm 10 has a first link 11a connected to the base 13, a second link 11b connected to the first link 11a, a third link 11c connected to the second link 11b, a fourth link 11d connected to the third link 11c, and a fifth link 11e connected to the fourth link 11d.

[0014] Specifically, the base 13 and the first link 11a are connected to each other via a first joint 12a that is rotatable about an axis extending in the vertical direction. The first link 11a and the second link 11b are connected to each other via a second joint 12b that is rotatable about an axis extending in the horizontal direction. The second link 11b and the third link 11c are connected to each other via a third joint 12c that is rotatable about an axis extending in the horizontal direction. The third link 11c and the fourth link 11d are connected to each other via a fourth joint 12d that is rotatable about the axis of the fourth link 11d (i.e., the direction in which the fourth link 11d extends). The fourth link 11d and the fifth link 11e are connected to each other via a fifth joint 12e that is rotatable about an axis perpendicular to the axis of the fourth link 11d.

[0015] The robot arm 10 has a servo motor that rotates each joint, and each servo motor has an encoder.

[0016] The robot arm 10 configured in this manner is configured to perform translational movements in the directions of the three orthogonal axes and rotational movements around the three orthogonal axes.

[0017] The robot system 1000 may include a camera 15 that acquires an image of the workpieces W. The camera 15 is fixedly disposed above the container 19. The camera 15 captures an image of the inside of the container 19 from above. The camera 15 acquires an image including a plurality of workpieces W inside the container 19.

[0018] Here, the image is a two-dimensional image or a three-dimensional image. The three-dimensional image may be point cloud data, an RGB-D image, an RGB image, a depth image, a voxel image, or the like. That is, the camera 15 may be a three-dimensional camera, i.e., an RGB-D camera that outputs an RGB-D image, a stereo camera that acquires an RGB image, or a three-dimensional vision sensor that acquires point cloud data.

[0019] Fig. 2 is a front view of the hand 2. Fig. 3 is a bottom view of the hand 2. Fig. 4 is a cross-sectional view of the hand 2 taken along line IV-IV in Fig. 3. Fig. 5 is a cross-sectional view of the hand 2 taken along line VV in Fig. 3. Fig. 6 is a cross-sectional view of the hand 2 taken along line VI-VI in Fig. 4. Note that the front wall of the hand main body 3 is omitted in Fig. 2.

[0020] The hand 2 has a hand body 3 and a plurality of fingers 4 that are provided on the hand body 3 and that open and close. In this example, the hand 2 has two fingers 4. A predetermined reference axis P is set for the hand 2. As shown in FIG. 2 , the fingers 4 extend from the hand body 3 in the direction of the reference axis P. The plurality of fingers 4 open and close in an opening and closing direction A that is perpendicular to the reference axis P. The reference axis P is located at the center of the plurality of fingers 4 in the opening and closing direction A. In other words, when the plurality of fingers 4 are in a fully closed state, the plurality of fingers 4 come into contact with each other on the reference axis P.

[0021] Each of the multiple fingers 4 has an endless belt 5 that comes into contact with the workpiece W. The endless belt 5 is wrapped around at least the tip of the finger 4 and is driven to rotate. Each finger 4 has an inner surface 4a that faces the other fingers 4. The inner surface 4a is formed by the endless belt 5. The portion of the endless belt 5 that corresponds to the inner surface 4a extends along the longitudinal direction of the finger 4. A portion of the endless belt 5 of one finger 4 and a portion of the endless belt 5 of the other finger 4 face each other in the opening / closing direction A. In the opening / closing direction A, the side on which the multiple fingers 4 open is called the "opening side," and the side on which the multiple fingers 4 close is called the "closing side."

[0022] As shown in Fig. 5, the hand 2 has an opening / closing actuator 7 that opens and closes the multiple fingers 4 in the opening / closing direction A. The multiple fingers 4 move toward and away from each other in the opening / closing direction A by the opening / closing actuator 7. This causes the multiple fingers 4 to grip the workpiece W or release their grip on the workpiece W. In this example, the opening / closing actuator 7 operates two fingers 4. In other words, the hand 2 has the opening / closing actuator 7 that is common to the two fingers 4.

[0023] As shown in Fig. 6, the hand 2 has a rotary actuator 8 that rotates the endless belt 5. The endless belt 5 is rotationally driven by the rotary actuator 8. At this time, the portion of the endless belt 5 that corresponds to the inner surface 4a moves in the longitudinal direction of the fingers 4. By rotating the endless belt 5 of each finger 4, the hand 2 pulls the workpiece W into or pulls out the workpiece W from between the fingers 4.

[0024] The hand 2 grips the workpiece W in a number of ways. In one way, the hand 2 brings the tips of the fingers 4 into contact with the workpiece W and draws the workpiece W between the fingers 4 using the endless belt 5. In another way, the hand 2 grips the workpiece W by opening and closing the fingers 4 in an opening and closing direction A. As shown in FIG. 3 , the hand 2 further has a sensor 210 that detects the drawing of the workpiece W between the fingers 4.

[0025] =Finger Flexibility= As shown in FIG. 2 , the fingers 4 are elastically displaceable in a first direction X in which the multiple fingers 4 open and close. Furthermore, the fingers 4 are elastically displaceable in a second direction Y in which the fingers 4 move forward and backward relative to the hand body 3. The first direction X is generally the same as the opening and closing direction A. In this example, the multiple fingers 4 are each elastically displaceable independently in the first direction X. The second direction Y is the same as the direction of the reference axis P, in other words, the same as the extension direction in which the fingers 4 extend from the hand body 3. The second direction Y is a direction intersecting with the opening and closing direction A, and more specifically, is perpendicular to the opening and closing direction A. In the second direction Y, the side from which the fingers 4 advance from the hand body 3 is simply referred to as the "advancing side," and the side from which the fingers 4 retreat toward the hand body 3 is simply referred to as the "retreating side." In this example, the multiple fingers 4 are each elastically displaceable independently in the second direction Y.

[0026] FIG. 7 is a perspective view of the finger 4. The endless belt 5 is omitted from FIG. 7 . The finger 4 includes a base 41 supported by the hand body 3 and a finger body 42 supported relative to the base 41 so as to be elastically displaceable in the first direction X and in the second direction Y. The base 41 is supported by the hand body 3 so as to be movable in the opening / closing direction A (see FIGS. 2 and 5 ). Specifically, the base 41 is supported by the hand body 3 via a feed screw 72 of the opening / closing actuator 7 (described later). The finger body 42 is supported by the base 41 so as to be swingable about a predetermined swing axis B. The swing axis B is perpendicular to both the opening / closing direction A and the second direction Y. The finger body 42 swings about the swing axis B to displace in the first direction X. That is, the first direction X is a circumferential direction centered on the swing axis B.

[0027] 7, the finger body 42 has an elongated shape. One longitudinal end of the finger body 42 is referred to as a first end 42a, and the other longitudinal end of the finger body 42 is referred to as a second end 42b. The first end 42a is the end that is farther away from the hand body 3 and is the tip of the finger body 42.

[0028] More specifically, the finger 4 has a support 43 that supports the finger body 42 relative to the base 41. That is, the finger body 42 is supported on the base 41 via the support 43. Fig. 8 is a side view of the finger 4. Fig. 9 is a cross-sectional view of the finger 4 taken along line IX-IX in Fig. 8. Fig. 10 is a front view of the finger body 42 and the support 43. Note that the endless belt 5 is omitted from Fig. 8.

[0029] As shown in Fig. 9 , the support 43 supports the support shaft 44 via a bearing so as to be rotatable about the axis of the support shaft 44. The axis of the support shaft 44 is the oscillation axis B. The support shaft 44 supports the finger body 42 via a bearing so as to be rotatable about the oscillation axis B. In other words, the support 43 supports the finger body 42 via the support shaft 44 so as to be oscillating about the oscillation axis B. The support shaft 44 supports the second end 42b of the finger body 42.

[0030] 10 , the support 43 supports the finger body 42 so as to hang down. The longitudinal direction of the finger body 42 hanging from the support 43 coincides with the second direction Y. From this state, the finger body 42 swings in the first direction X around the swing axis B. As a result, the finger body 42 moves toward or away from another finger body 42, i.e., moves in a direction in which the finger 4 opens or closes.

[0031] As shown in Fig. 10 , the support 43 has a first stopper 43a and a second stopper 43b that limit the swing of the finger body 42. The first stopper 43a is disposed on the opening side of the finger 4 with respect to the finger body 42. The first stopper 43a has a long, thin plate shape. As shown by the two-dot chain line in Fig. 10 , when the finger body 42 moves toward the opening side of the finger 4, the finger body 42 comes into contact with the first stopper 43a, thereby limiting the displacement of the finger body 42 toward the opening side of the finger 4.

[0032] The second stopper 43b is disposed on the closing side of the finger 4 with respect to the finger body 42. The second stopper 43b is a shaft extending parallel to the swing axis B (see FIG. 7). When the finger body 42 is displaced toward the closing side of the finger 4, the finger body 42 comes into contact with the second stopper 43b, thereby restricting the displacement of the finger body 42 toward the closing side of the finger 4.

[0033] The first stopper 43 a and the second stopper 43 b limit the swing range of the finger body 42. Since the finger body 42 swings only a relatively small range from the state in which it extends in the second direction Y, the first direction X generally coincides with the opening / closing direction A.

[0034] Figure 11 is a cross-sectional view of the finger 4 taken along line XI-XI in Figure 8. The hand 2 further includes a torsion spring 45 that biases the finger body 42 in the first direction X toward the closing side of the finger 4. The axis of the torsion spring 45 is located eccentrically from the oscillation axis B. The torsion spring 45 has a coil 45a, a first arm 45b, and a second arm 45c.

[0035] The torsion spring 45 is disposed on the finger body 42. The finger body 42 has a support shaft 42c that supports the coil 45a of the torsion spring 45 and a contact shaft 42d with which the first arm 45b of the torsion spring 45 contacts. The support shaft 42c and the contact shaft 42d are disposed near the second stopper 43b and extend parallel to the oscillation axis B. The support shaft 42c is inserted into the coil 45a of the torsion spring 45. The second arm 45c of the torsion spring 45 contacts the second stopper 43b. The torsion spring 45 biases the contact shaft 42d and the second stopper 43b in directions that move them away from each other. More specifically, the support shaft 42c, the contact shaft 42d, and the second stopper 43b are disposed on the opposite side of the oscillation axis B from the first end 42a of the finger body 42. The contact shaft 42d is located closer to the closing side of the finger 4 than the second stopper 43b in the circumferential direction about the oscillation axis B. That is, in the circumferential direction about the oscillation axis B, the direction in which the contact shaft 42d moves away from the second stopper 43b is the direction in which the finger body 42 swings toward the closing side of the finger 4. As a result, a moment toward the closing side of the finger 4 acts on the finger body 42 about the oscillation axis B due to the biasing force of the torsion spring 45.

[0036] When no external force is acting on the finger body 42 (i.e., in the normal state), the finger body 42 is moved away from the first stopper 43a and in contact with the second stopper 43b by the biasing force of the torsion spring 45. In other words, in the normal state, the finger body 42 can be elastically displaced toward the opening side of the fingers 4.

[0037] 12 is a perspective view of the finger 4 from a different angle than that of FIG. 7. The endless belt 5 is omitted from FIG. 12. The support 43 is connected to the base 41 so as to be displaceable in the second direction Y. The support 43 is connected to the base 41 via a pair of linear guides 46. The linear guides 46 guide the support 43 in the second direction Y.

[0038] 9, each linear guide 46 has a first rail 46a, a second rail 46b, and a plurality of balls or rollers provided between the first rail 46a and the second rail 46b. The first rail 46a and the second rail 46b are relatively movable in the second direction Y. The first rail 46a is attached to the base 41, and the second rail 46b is attached to the support 43. More specifically, the second rail 46b is attached to a first stopper 43a.

[0039] As the support 43 moves in the second direction Y relative to the base 41 via the linear guide 46 , the finger body 42 supported by the support 43 also moves in the second direction Y relative to the base 41 .

[0040] FIG. 13 is a front view of the finger 4. As shown in FIG. 13 , the support 43 is biased toward the advancing side in the second direction Y by a spring 47. For example, the spring 47 is a coil spring. The support 43 has a pin 43c that protrudes toward the retreating side in the second direction Y. Meanwhile, the base 41 has a pin 41a that protrudes toward the advancing side in the second direction Y at a position corresponding to the pin 43c. One end of the spring 47 is attached to the pin 41a, and the other end of the spring 47 is attached to the pin 43c. At this time, the spring 47 is compressed. The elastic force of the spring 47 is directed in the second direction Y. The spring 47 biases the pins 41a and 43c in directions that move them away from each other. In other words, the spring 47 biases the support 43 toward the advancing side in the second direction Y relative to the base 41.

[0041] As a result, the finger body 42 is biased by the spring 47 toward the advancing side in the second direction Y relative to the base 41. The finger body 42 can be displaced toward the retreating side in the second direction Y against the elastic force of the spring 47. FIG. 14 is a front view of the finger 4 in a state in which the finger body 42 has been displaced toward the retreating side in the second direction Y. In FIG. 14, the spring 47 is illustrated as being partially broken away. The finger body 42 can be displaced toward the retreating side in the second direction Y to a position where the pin 41 a and the pin 43 c come into contact with each other. In other words, the pins 41 a and 43 c function as stoppers that limit the movement of the finger body 42 in the second direction Y.

[0042] As will be described in more detail later, the movement of the finger body 42 toward the advancing side in the second direction Y is restricted by the hand body 3 as a link mechanism 9 (described later) arranged on the finger 4 comes into contact with the hand body 3.

[0043] In this way, the support 43 is supported by the base 41 so as to be elastically displaceable in the second direction Y. As a result, the finger body 42 is supported by the base 41 via the support 43 so as to be elastically displaceable in the second direction Y. Furthermore, the finger body 42 is supported by the support 43 so as to be elastically displaceable in the first direction X. In other words, the finger body 42 is supported by the base 41 via the support 43 so as to be elastically displaceable in the first direction X. In this example, when the support 43 moves in the second direction Y, the oscillation axis B also moves in the second direction Y.

[0044] 11, the finger 4 includes a first pulley 51 that is driven to rotate, a second pulley 52 that is disposed at the tip of the finger 4, and a third pulley 53 that is disposed between the first pulley 51 and the second pulley 52. ​​The endless belt 5 is wound around the first pulley 51, the second pulley 52, and the third pulley 53. The first pulley 51 is a driving pulley, and the second pulley 52 and the third pulley 53 are driven pulleys.

[0045] The finger body 42 supports the first pulley 51, the second pulley 52, and the third pulley 53 so that they can rotate around rotation axes that are parallel to each other. Specifically, as shown in FIG. 9 , the first pulley 51 is rotatably supported by the finger body 42 via a support shaft 44. The first pulley 51 is non-rotatable relative to the support shaft 44. The support shaft 44 supports the finger body 42 so that it can rotate around its axis, i.e., the oscillation axis B. As a result, the first pulley 51 can rotate around the oscillation axis B relative to the finger body 42. The second pulley 52 and the third pulley 53 are also rotatably supported by the finger body 42 via shafts.

[0046] 11, the third pulley 53 is disposed near the tip of the finger 4, i.e., near the second pulley 52. ​​The third pulley 53 is disposed on the closing side of the second pulley 52 in the opening / closing direction A. In other words, as shown in FIG. 4, the distance between the third pulleys 53 of the multiple fingers 4 is narrower than the distance between the second pulleys 52 of the multiple fingers 4.

[0047] In this example, as shown in FIG. 11 , the finger 4 further includes a fourth pulley 54 and a fifth pulley 55. The finger body 42 rotatably supports the fourth pulley 54 and the fifth pulley 55. The fourth pulley 54 and the fifth pulley 55 are driven pulleys. The rotation axes of the fourth pulley 54 and the fifth pulley 55 are parallel to the rotation axes of the first pulley 51 and the like. The fourth pulley 54 is disposed between the first pulley 51 and the third pulley 53. The fourth pulley 54 is disposed closer to the first pulley 51 than the third pulley 53. The fifth pulley 55 is disposed between the first pulley 51 and the second pulley 52. ​​However, the fifth pulley 55 is disposed closer to the opening side in the opening / closing direction A than the first pulley 51 and the second pulley 52.

[0048] The endless belt 5 is disposed on the finger body 42. The endless belt 5 is wound around a first pulley 51, a second pulley 52, a third pulley 53, a fourth pulley 54, and a fifth pulley 55 from the outside. That is, the first pulley 51, the second pulley 52, the third pulley 53, the fourth pulley 54, and the fifth pulley 55 are disposed inside the endless belt 5. The endless belt 5 is a toothed belt, i.e., a timing belt. The first pulley 51 and the second pulley 52 are toothed pulleys, i.e., timing pulleys. The third pulley 53, the fourth pulley 54, and the fifth pulley 55 are toothed pulleys and function as toothed idlers. The teeth of the endless belt 5 mesh with the teeth of the first pulley 51, etc.

[0049] The portion of the endless belt 5 between the first pulley 51 and the second pulley 52, which passes through the third pulley 53 and the fourth pulley 54, corresponds to the inner surface 4a of the finger 4. In a normal state, i.e., when no external force is acting in the first direction X, the portion of the endless belt 5 corresponding to the inner surface 4a extends in the second direction Y and faces the closing side of the opening / closing direction A. In other words, the portion of the endless belt 5 of one finger 4 corresponding to the inner surface 4a and the portion of the endless belt 5 of the other finger 4 corresponding to the inner surface 4a face each other, as shown in FIG. 4 . Strictly speaking, the portion of the endless belt 5 of one finger 4 corresponding to the inner surface 4a and the portion of the endless belt 5 of the other finger 4 corresponding to the inner surface 4a are inclined so that the distance between them narrows toward the tip.

[0050] The portion of the endless belt 5 between the second pulley 52 and the third pulley 53 is inclined with respect to the portion of the endless belt 5 between the third pulley 53 and the fourth pulley 54. Specifically, the portion of the endless belt 5 between the second pulley 52 and the third pulley 53 is inclined so as to be positioned on the opening side in the opening direction A as it approaches the tip of the finger 4. In other words, the tip portions of the inner surfaces 4a of the fingers 4 are inclined so as to open toward the opening side in the opening direction A. As a result, the spacing between the multiple fingers 4 at the tip portions of the fingers 4 widens toward the tip of the fingers 4.

[0051] As shown in FIG. 11 , the finger 4 further has a plurality of rollers 56. The finger body 42 supports each of the rollers 56 rotatably around a rotation axis that is parallel to one another. The rotation axis of the roller 56 is parallel to the rotation axis of the first pulley 51, etc. The rollers 56 are arranged inside the endless belt 5. The rollers 56 are arranged along a portion of the endless belt 5 between the third pulley 53 and the fourth pulley 54. Each roller 56 is close to the endless belt 5. Specifically, there is a gap between each roller 56 and the endless belt 5.

[0052] The endless belt 5 rotates as the first pulley 51 is driven to rotate. When the endless belt 5 rotates, the portion of the endless belt 5 corresponding to the inner surface 4a moves in the second direction Y. At this time, whether the portion of the endless belt 5 corresponding to the inner surface 4a moves toward the first end 42a or the second end 42b of the finger body 42 in the second direction Y depends on the direction of rotation of the first pulley 51. Hereinafter, rotation in which the portion corresponding to the inner surface 4a moves toward the first end 42a will be referred to as "rotation toward the payout side," and rotation in which the portion corresponding to the inner surface 4a moves toward the second end 42b will be referred to as "rotation toward the retraction side."

[0053] 5 , the opening / closing actuator 7 has a first motor 71, a feed screw 72 to which the finger 4 is connected, and a transmitter 75 that transmits the rotational driving force of the first motor 71 to the feed screw 72. The opening / closing actuator 7 is disposed in the hand body 3.

[0054] The first motor 71 is, for example, a servo motor. A current sensor is provided in the driver of the first motor 71. The first motor 71 is attached to the hand body 3 so that the output shaft 71 a is parallel to the opening / closing direction A.

[0055] The lead screw 72 includes a screw 73 and a nut 74. In this example, the lead screw 72 includes two nuts 74. The screw 73 extends in the opening / closing direction A. The screw 73 is supported on the hand main body 3 via a bearing so as to be rotatable around an axis extending in the opening / closing direction A. The screw 73 is a so-called left-right screw. The screw 73 includes a right-hand thread portion and a left-hand thread portion that are aligned on the same axis.

[0056] Each nut 74 is threaded onto the screw 73. One nut 74 is connected to each finger 4. The nuts 74 are fixed to the base 41 of the finger 4. By threading the nuts 74 onto the screws 73, the base 41 is supported by the feed screw 72 so as to be movable in the opening and closing direction A. One nut 74 is threaded onto the right-hand thread portion of the screw 73, and the other nut 74 is threaded onto the left-hand thread portion of the screw 73.

[0057] In addition, the base 41 is prevented from rotating around the axis of the screw 73 by the hand body 3. More specifically, when the base 41 is supported by the feed screw 72, the base 41 is located near the bottom plate 31 of the hand body 3, as shown in FIG. 5. The bottom plate 31 has a slit 32 extending in the opening / closing direction A. The base 41 is fitted into the slit 32. As shown in FIG. 8, a stopper 41b is attached to the base 41 to prevent the base 41 from coming out of the slit 32. As shown in FIG. 3, the stopper 41b is exposed to the outside of the hand body 3. Because the base 41 is fitted into the slit 32, it cannot rotate around the axis of the screw 73.

[0058] As shown in FIG. 5 , the transmitter 75 includes a first pulley 75a attached to the output shaft 71a of the first motor 71, a second pulley 75b attached to the screw 73, and a timing belt 75c wound around the first pulley 75a and the second pulley 75b. The first pulley 75a and the second pulley 75b are toothed pulleys, i.e., timing pulleys. The timing belt 75c is also a toothed belt. The first pulley 75a is non-rotatably attached to the output shaft 71a of the first motor 71. The second pulley 75b is non-rotatably attached to the screw 73. The rotational driving force of the first motor 71 is transmitted from the first pulley 75a to the second pulley 75b via the timing belt 75c.

[0059] When the first motor 71 is operated, the screw 73 rotates integrally with the second pulley 75b. Because the base 41 fixed to the nut 74 is fitted into the slit 32 of the hand body 3, the nut 74 and the base 41 do not rotate even when the screw 73 rotates. As the screw 73 rotates, the nut 74 and the base 41 move toward the axis of the screw 73, and as a result, the fingers 4 move in the opening / closing direction A.

[0060] The nut 74 of one finger 4 is threaded onto the right-hand thread of the screw 73, and the nut 74 of the other finger 4 is threaded onto the left-hand thread of the screw 73. Therefore, when the screw 73 rotates, the two fingers 4 move either toward each other in the opening / closing direction A (i.e., close), or away from each other (i.e., open) in the opening / closing direction A. Whether the two fingers 4 close or open is switched depending on the direction of rotation of the screw 73, i.e., the direction of rotation of the first motor 71.

[0061] 6, the rotary actuator 8 has a second motor 81 that outputs a rotational driving force for the endless belt 5, and a transmitter 82 that transmits the rotational driving force of the second motor 81 to the first pulley 51. The second motor 81 is, for example, a servo motor. A current sensor is provided in the driver of the second motor 81. The second motor 81 is attached to the hand body 3 so that the output shaft 81a is parallel to the opening / closing direction A.

[0062] The transmitter 82 includes a first transmitter 83 arranged on the hand body 3 and a second transmitter 84 arranged on the finger 4 .

[0063] The first transmitter 83 includes a first pulley 83 a, a second pulley 83 b, a timing belt 83 c wound around the first pulley 83 a and the second pulley 83 b, and a spline shaft 83 d to which the second pulley 83 b is connected. The first pulley 83 a and the second pulley 83 b are toothed pulleys, i.e., timing pulleys. The timing belt 83 c is a toothed belt. The first transmitter 83 transmits the rotational driving force of the second motor 81 to the spline shaft 83 d.

[0064] The first pulley 83a is non-rotatably connected to the output shaft 81a. The spline shaft 83d has an axis C that extends parallel to the opening / closing direction A. The spline shaft 83d is supported by the hand body 3 so as to be rotatable around the axis C. The second pulley 83b is non-rotatably connected to the spline shaft 83d around the axis C.

[0065] 12, the second transmitter 84 includes a screw gear 85 provided on the base 41, a first transmission pulley 86 provided on the base 41, a second transmission pulley 87 provided on the finger body 42 (see FIG. 7), a transmission belt 810 (see FIG. 8) wound around the first transmission pulley 86 and the second transmission pulley 87, a first idle pulley 88 that applies tension to the transmission belt 810, a second idle pulley 89 that applies tension to the transmission belt 810, and a link mechanism 9 that is connected to the base 41 and the finger body 42, respectively, and supports the first idle pulley 88 and the second idle pulley 89. The second transmitter 84 transmits the rotation of the spline shaft 83d to the first pulley 51 of the finger 4.

[0066] As shown in FIG. 11 , the screw gear 85 includes a first gear 85a and a second gear 85b that meshes with the first gear 85a. The first gear 85a is supported on the base 41 of the finger 4 so as to be rotatable around axis C but immovable in the direction of axis C. Specifically, the first gear 85a is connected to the spline shaft 83d so as to be rotatable around axis C but immovable in the direction of axis C. The second gear 85b is supported on the base 41 so as to be rotatable around axis D. The axis D is disposed in a twisted position with respect to axis C. The axis D is parallel to the rotation axis of the first pulley 51, i.e., the oscillation axis B. Specifically, the base 41 supports the shaft 85c so as to be rotatable around the axis D of the shaft 85c as the rotation axis. The second gear 85b is supported on the shaft 85c so as not to be rotatable around axis D. In other words, the second gear 85b is supported on the base 41 via the shaft 85c so as to be rotatable around axis D.

[0067] When the spline shaft 83d rotates around the axis C, the first gear 85a rotates integrally with the spline shaft 83d around the axis C. At this time, the base 41 does not rotate around the axis C. When the first gear 85a rotates, the second gear 85b rotates around the axis D.

[0068] 12, the first transmission pulley 86 is supported on the base 41 so as to be rotatable about the axis D. Specifically, the first transmission pulley 86 is supported on the shaft 85c so as not to be rotatable about the axis D. The first transmission pulley 86 is disposed coaxially with the second gear 85b, and rotates about the axis D integrally with the second gear 85b.

[0069] As shown in Fig. 9, the second transmission pulley 87 is supported by the support shaft 44 so as not to rotate around its axis. As described above, the support shaft 44 supports the first pulley 51 so as not to rotate around its axis, and supports the finger body 42 so as to be rotatable around its axis. In other words, the second transmission pulley 87 is supported by the finger body 42 via the support shaft 44 so as to be rotatable around the axis of the support shaft 44, i.e., the oscillation axis B. The second transmission pulley 87 is disposed coaxially with the first pulley 51 and rotates integrally with the first pulley 51 around the oscillation axis B. The rotation axis of the second transmission pulley 87 is parallel to the rotation axis of the first transmission pulley 86.

[0070] As shown in FIG. 12, the first idle pulley 88 and the second idle pulley 89 are each supported by the link mechanism 9 so as to be rotatable around a rotation axis parallel to the rotation axis of the first transmission pulley 86 and the second transmission pulley 87.

[0071] As shown in FIG. 13 , the link mechanism 9 includes a first link 91, a second link 92, a third link 93, and a fourth link 94. The first link 91 rotatably supports the first idle pulley 88 and is connected to the base 41 so as to be rotatable around the axis of the first transmission pulley 86, i.e., axis D. The second link 92 rotatably supports the first idle pulley 88 and is connected to the finger body 42 so as to be rotatable around the axis of the second transmission pulley 87, i.e., oscillation axis B. The third link 93 rotatably supports the second idle pulley 89 and is connected to the finger body 42 so as to be rotatable around the axis of the second transmission pulley 87, i.e., oscillation axis B. The fourth link 94 rotatably supports the second idle pulley 89 and is connected to the base 41 so as to be rotatable around the axis of the first transmission pulley 86, i.e., axis D. That is, the first idle pulley 88 is supported by the first link 91 and the second link 92. The second idle pulley 89 is supported by the third link 93 and the fourth link 94. In other words, the first link 91 connects the first transmission pulley 86 and the first idle pulley 88. The second link 92 connects the first idle pulley 88 and the second transmission pulley 87. The third link 93 connects the second transmission pulley 87 and the second idle pulley 89. The fourth link 94 connects the second idle pulley 89 and the first transmission pulley 86.

[0072] The first link 91 and the third link 93 are parallel to each other. The second link 92 and the fourth link 94 are parallel to each other. In other words, the link mechanism 9 is a parallel link mechanism. In the parallelogram formed by the link mechanism 9, the first transmission pulley 86 and the second transmission pulley 87 are disposed at one diagonal position. The first idle pulley 88 and the second idle pulley 89 are disposed at the other diagonal position.

[0073] The first link 91, the second link 92, the third link 93, and the fourth link 94 are equilateral links, that is, the first link 91, the second link 92, the third link 93, and the fourth link 94 have the same length.

[0074] The first transmission pulley 86, the second transmission pulley 87, the first idle pulley 88, and the second idle pulley 89 have the same pitch circle diameter.

[0075] The transmission belt 810 is an endless belt and is wound around the first transmission pulley 86, the second transmission pulley 87, the first idle pulley 88, and the second idle pulley 89 from the outside. In other words, the first transmission pulley 86, the second transmission pulley 87, the first idle pulley 88, and the second idle pulley 89 are arranged inside the transmission belt 810.

[0076] The transmission belt 810 is a toothed belt. The first transmission pulley 86 and the second transmission pulley 87 are toothed pulleys, i.e., timing pulleys. The first idler pulley 88 and the second idler pulley 89 are toothed pulleys and function as toothed idlers. The teeth of the transmission belt 810 mesh with the teeth of the first transmission pulley 86, etc.

[0077] As described above, the finger body 42 is displaced relative to the base 41. For example, as shown in FIG. 14 , the finger body 42 is displaced in the second direction Y relative to the base 41. The first transmission pulley 86 is disposed on the base 41, and the second transmission pulley 87 is disposed on the finger body 42. The relative positional relationship between the first transmission pulley 86 and the second transmission pulley 87 changes in response to the displacement of the finger body 42 in the second direction Y. When the relative positional relationship between the first transmission pulley 86 and the second transmission pulley 87 changes, the link mechanism 9 is deformed, and the first idle pulley 88 and the second idle pulley 89 supported by the link mechanism 9 are displaced. Even if the first idle pulley 88 and the second idle pulley 89 are displaced, the perimeter of the rectangle formed by the link mechanism 9 does not change. In other words, the first idle pulley 88 and the second idle pulley 89 continue to apply an appropriate tension to the transmission belt 810 by displacing in accordance with the link mechanism 9. As a result, the transmission belt 810 appropriately transmits the rotation of the first transmission pulley 86 to the second transmission pulley 87 .

[0078] The finger body 42 also displaces in the first direction X relative to the base 41. At this time, the finger body 42 oscillates around the oscillation axis B, i.e., the axis of the support shaft 44. Because the first pulley 51 and the second transmission pulley 87 are supported by the support shaft 44, the first pulley 51 and the second transmission pulley 87 do not displace even when the finger body 42 oscillates around the oscillation axis B. As a result, the relative positional relationship between the first transmission pulley 86 and the second transmission pulley 87 does not change, and the link mechanism 9 does not deform. Therefore, the transmission belt 810 appropriately transmits the rotation of the first transmission pulley 86 to the second transmission pulley 87.

[0079] In the rotary actuator 8 configured as described above, as shown in FIG. 6 , when the second motor 81 is operated, the rotational drive force of the second motor 81 is transmitted from the first pulley 83 a to the second pulley 83 b via the timing belt 83 c, causing the spline shaft 83 d to rotate about the axis C. When the spline shaft 83 d rotates, the first gear 85 a of the screw gear 85 rotates integrally with the spline shaft 83 d. In response to this, as shown in FIG. 12 , the second gear 85 b rotates, and the first transmission pulley 86 also rotates integrally with the second gear 85 b. As shown in FIG. 9 , the rotation of the first transmission pulley 86 is transmitted to the second transmission pulley 87 via the transmission belt 810, causing the first pulley 51 to rotate integrally with the second transmission pulley 87. In this way, the first pulley 51 is rotationally driven by the second motor 81, and as a result, the endless belt 5 rotates. The rotation direction of the endless belt 5 is switched depending on the rotation direction of the second motor 81 .

[0080] Here, when the finger 4 moves in the opening / closing direction A, the second transmitter 84 moves integrally with the finger 4 in the opening / closing direction A. Specifically, the first gear 85a is movable in the direction of axis C relative to the spline shaft 83d. Because axis C is parallel to the opening / closing direction A, the first gear 85a supported by the base 41 moves along the spline shaft 83d in response to the movement of the finger 4 in the opening / closing direction A. Even when the finger 4 moves in the opening / closing direction A, the first gear 85a remains supported by the spline shaft 83d so as not to be rotatable around axis C. In other words, regardless of the position of the finger 4 in the opening / closing direction A, the rotational drive force of the second motor 81 is transmitted to the first gear 85a via the spline shaft 83d.

[0081] Furthermore, as described above, the finger body 42 of the finger 4 is displaced in the first direction X. At this time, the finger body 42 oscillates around the oscillation axis B, i.e., the axis of the support shaft 44. The first pulley 51 and the second transmission pulley 87 are supported by the support shaft 44. Therefore, even if the finger body 42 oscillates around the oscillation axis B, the first pulley 51 and the second transmission pulley 87 do not displace. As a result, even if the finger body 42 is displaced in the first direction X, the rotational driving force of the second motor 81 is transmitted to the second transmission pulley 87 via the transmission belt 810.

[0082] Furthermore, as described above, the finger body 42 of the finger 4 is displaced in the second direction Y. At this time, the finger body 42 is displaced in the second direction Y relative to the base 41. The first transmission pulley 86 is disposed on the base 41, and the second transmission pulley 87 is disposed on the finger body 42. Therefore, the relative positional relationship between the first transmission pulley 86 and the second transmission pulley 87 changes in response to the displacement of the finger body 42 in the second direction Y. When the relative positional relationship between the first transmission pulley 86 and the second transmission pulley 87 changes, the first idle pulley 88 and the second idle pulley 89 supported by the link mechanism 9 are displaced. The first idle pulley 88 and the second idle pulley 89 are displaced in accordance with the link mechanism 9, thereby continuously applying an appropriate tension to the transmission belt 810. As a result, the transmission belt 810 appropriately transmits the rotation of the first transmission pulley 86 to the second transmission pulley 87.

[0083] In short, regardless of the movement of the finger 4 in the opening / closing direction A, the displacement of the finger body 42 in the first direction X, or the displacement of the finger body 42 in the second direction Y, the endless belt 5 is driven to rotate by the second motor 81.

[0084] As shown in FIG. 2 , the link mechanism 9 is disposed within the hand body 3. The fourth link 94 is disposed near the bottom plate 31 of the hand body 3. The finger body 42 is biased by the spring 47 toward the advancing side in the second direction Y relative to the base 41. When the finger body 42 moves toward the advancing side in the second direction Y, the fourth link 94 moves toward the advancing side in the second direction Y together with the finger body 42. Eventually, the second link 92 and the third link 93 come into contact with the bottom plate 31. In other words, the movement of the finger body 42 toward the advancing side in the second direction Y is limited by the contact of the second link 92 and the third link 93 with the bottom plate 31. Alternatively, the movement of the finger body 42 toward the advancing side in the second direction Y can also be limited by the contact of the second link 92 and the fourth link 94 with the bottom plate 31.

[0085] =Sensor= The sensor 210 detects the drawing of the workpiece W between the multiple fingers 4. For example, the sensor 210 is provided on the hand body 3 and positioned between the multiple fingers 4 as shown in FIG. 2. More specifically, the sensor 210 is positioned at the center of the multiple fingers 4 in the opening / closing direction A as shown in FIG. 3. The sensor 210 is a distance sensor. More specifically, the sensor 210 detects the distance to an object present between the multiple fingers 4. The sensor 210 detects the drawing of the workpiece W between the multiple fingers 4. For example, the sensor 210 may be a TOF (Time Of Flight) distance sensor.

[0086] =Control Device= Fig. 15 is a diagram showing a schematic hardware configuration of the control device 100. The control device 100 controls the hand 2 and the robot arm 10 to cause the hand 2 to perform various tasks, such as picking. The robot system 1000 further includes a robot control device 120. The control device 100 transmits and receives signals, information, and the like to and from the robot control device 120. The control device 100 controls the hand 2 and the robot arm 10 via the robot control device 120. The control device 100 outputs commands to the robot control device 120. The control device 100 transmits and receives signals, information, and the like to and from the camera 15. The robot control device 120 controls servo motors, etc. of the robot arm 10 and the hand 2 in accordance with commands from the control device 100.

[0087] An image from the camera 15 is input to the control device 100. The control device 100 detects the workpiece W based on the image. In addition, the control device 100 generates a target path for the robot 1 based on the detected workpiece W, and outputs a command corresponding to the generated target path to the robot control device 120.

[0088] The robot control device 120 includes a processor 121 , a storage device 122 , and a memory 123 .

[0089] The processor 121 controls the entire robot control device 120. The processor 121 performs various types of arithmetic processing. For example, the processor 121 is formed of a processor such as a CPU (Central Processing Unit). The processor 121 may also be formed of an MCU (Micro Controller Unit), an MPU (Micro Processor Unit), an FPGA (Field Programmable Gate Array), a PLC (Programmable Logic Controller), a system LSI, or the like.

[0090] The storage unit 122 stores various data and programs executed by the processor 121. The storage unit 122 is formed of a non-volatile memory, a hard disk drive (HDD), a solid state drive (SSD), etc. The memory 123 temporarily stores data, etc. For example, the memory 123 is formed of a volatile memory.

[0091] The processor 121 controls the hand 2 and the robot arm 10 based on commands from the control device 100. Specifically, the processor 121 controls the servo motors of the robot arm 10, etc. At this time, the processor 121 performs feedback control or feedforward control of the servo motors.

[0092] The control device 100 includes a processor 101 , a storage device 102 , and a memory 103 .

[0093] The processor 101 controls the entire control device 100. The processor 101 performs various types of arithmetic processing. For example, the processor 101 is formed of a processor such as a CPU (Central Processing Unit). The processor 101 may be formed of an MCU (Micro Controller Unit), an MPU (Micro Processor Unit), an FPGA (Field Programmable Gate Array), a PLC (Programmable Logic Controller), a system LSI, or the like.

[0094] The memory 102 stores various programs and various data to be executed by the processor 101. The memory 102 is formed of a non-volatile memory, a hard disk drive (HDD), a solid state drive (SSD), etc. The various programs cause the control device 100 to realize various functions.

[0095] The memory 103 temporarily stores data, etc. For example, the memory 103 is formed of a volatile memory. The memory 103 stores images from the camera 15.

[0096] The processor 101 causes the hand 2 and the robot arm 10 to perform a retraction operation in which the tips of the multiple fingers 4 are brought into contact with the workpiece W and the endless belt 5 is used to retract the workpiece W between the multiple fingers 4. During the retraction operation, the processor 101 causes the hand 2 and the robot arm 10 to perform a search operation. The search operation is an operation in which the relative positions of the tips of the multiple fingers 4 and the workpiece W are changed while the multiple fingers 4 are spread apart at a predetermined interval and the endless belt 5 is rotated. The change in the relative positions of the tips of the multiple fingers 4 and the workpiece W can include a change in the relative positions in any direction, as long as the positional relationship between the tips of the multiple fingers 4 and the workpiece W changes.

[0097] 16 is a block diagram showing the configuration of a control system for the processor 101. The processor 101 realizes various functions by reading a program from the storage device 102 into the memory 103 and expanding the program. In detail, the processor 101 functions as an imaging controller 104 that causes the camera 15 to acquire an image, a detector 105 that detects the workpiece W, an operation controller 106 that operates the hand 2 and the robot arm 10, and a determiner 107.

[0098] The photography controller 104 controls the camera 15 to capture an image. The camera 15 captures an image of the inside of the container 19. The photography controller 104 stores the image from the camera 15 in the memory 103.

[0099] The detector 105 detects the position of the workpiece W from the image. The image may include multiple workpieces W. The detector 105 detects the position of the workpiece W from the image by any image processing. The detector 105 detects at least the approximate position of the workpiece W. Note that the detector 105 does not need to detect the exact position or orientation of the workpiece W. In this example, since the target is loosely stacked workpieces W, the detector 105 may detect the approximate position of the collection of loosely stacked workpieces W.

[0100] The motion controller 106 controls the robot arm 10 to move the hand 2 to a target position. Specifically, the motion controller 106 generates a target path for the robot arm 10 based on the detected position of the workpiece W. The motion controller 106 outputs a command according to the target path to the robot control device 120. As described above, the robot control device 120 controls the servo motors based on the command, causing the robot arm 10 and the hand 2 to move along the target path. During a retraction operation, the motion controller 106 moves the hand 2 to a position where the tips of the multiple fingers 4 come into contact with the workpiece W. During a search operation, the motion controller 106 controls the robot arm 10 so that the relative positions of the tips of the multiple fingers 4 and the workpiece W change.

[0101] With regard to the control of the hand 2, the motion controller 106 controls the opening and closing of the multiple fingers 4 and the rotation of the endless belt 5. Specifically, the motion controller 106 controls the first motor 71 and the second motor 81 via the robot control device 120. The motion controller 106 opens and closes the fingers 4 by controlling the first motor 71. The motion controller 106 adjusts the spacing between the multiple fingers 4 to a predetermined value by controlling the first motor 71. The motion controller 106 rotates the endless belt 5 by controlling the second motor 81. More specifically, the motion controller 106 switches between pulling in and feeding out the workpiece W by switching the direction of rotation of the second motor 81.

[0102] The determiner 107 determines whether the workpiece W has been drawn between the plurality of fingers 4 based on the detection result of the sensor 210. The determiner 107 determines that the drawing of the workpiece W between the plurality of fingers 4 has been completed when the distance from the sensor 210 to the workpiece W is equal to or less than a predetermined threshold.

[0103] Furthermore, the determiner 107 may determine the approach of the finger 4 to the workpiece W based on the detection result of the sensor 210. For example, the determiner 107 determines that the finger 4 has come into contact with the workpiece W when the distance from the sensor 210 to the workpiece W reaches a predetermined threshold. The threshold for determining the contact of the finger 4 is greater than the threshold for determining the retraction of the workpiece W.

[0104] =Robot Operation= Next, the operation of the robot 1 will be described in detail. The robot 1 performs a pull-in grip, which grips the workpiece W by a pull-in operation that pulls the workpiece W between the multiple fingers 4 using the endless belt 5. The control device 100 causes the hand 2 and the robot arm 10 to perform a search operation when performing such a pull-in grip. Specifically, the motion controller 106 rotates the endless belt 5 toward the pull-in side, brings the tips of the multiple fingers 4 into contact with the workpiece W, and further changes the relative positions of the tips of the multiple fingers 4 and the workpiece W. Changing the relative positions does not only involve monotonically decreasing or increasing the relative distance between the tips of the multiple fingers 4 and the workpiece W, but also includes both decreasing and increasing the relative distance. In this example, the control device 100 moves the tips of the multiple fingers 4 toward and away from a collection of multiple randomly piled workpieces W during the search operation, bringing the tips of the multiple fingers 4 into contact with any of the multiple workpieces W. Since the endless belt 5 rotates toward the retraction side, when the workpiece W is properly fitted between the fingers 4 at the tips of the fingers 4, the workpiece W is retracted between the fingers 4 by the endless belt 5.

[0105] The retraction and gripping of the robot 1 will be described in detail with reference to Fig. 17. Fig. 17 is a flowchart of the pick-and-place process.

[0106] First, in step S101, the photography controller 104 acquires an image of the inside of the container 19. More specifically, the photography controller 104 causes the camera 15 to acquire an image of the inside of the container 19.

[0107] In step S102, the detector 105 detects the position of the workpieces W from the image of the inside of the container 19. For example, the detector 105 detects the approximate position of a collection of workpieces W piled up in bulk.

[0108] Then, in step S103, the motion controller 106 starts a search operation. Specifically, the motion controller 106 adjusts the opening degree of the multiple fingers 4 and rotates the endless belt 5. In this state, the motion controller 106 changes the relative positions of the tips of the multiple fingers 4 and the workpiece W.

[0109] The control device 100 adjusts the spacing between the multiple fingers 4 to be smaller than the size of the workpiece W to be pulled in. Here, the spacing between the multiple fingers 4 that can be adjusted by the control device 100 is a spacing that can be controlled by the first motor 71 and is determined by the spacing between the multiple bases 41. Because each finger 4 can be displaced in the first direction X, the spacing between the multiple fingers 4 can be wider than the controlled spacing.

[0110] The control device 100 adjusts the spacing between the multiple fingers 4 to be smaller by a predetermined amount than the size of the workpiece W to be drawn in. For example, the size of the target workpiece W is the size of a portion of the target workpiece W that can be easily grasped by the multiple fingers 4. If the target workpiece W is a bolt, for example, the size of the target workpiece W is the outer diameter of the bolt's threads. If the target workpiece W is a nut, for example, the size of the target workpiece W is the thickness of the nut. The predetermined amount is smaller than the maximum increase in the spacing between the multiple fingers 4 that is expanded by the elastic displacement of the fingers 4 in the first direction X. In other words, the spacing between the multiple fingers 4 is adjusted to a spacing that allows the workpiece W to be drawn in to fit between the multiple fingers 4 when the multiple fingers 4 are elastically displaced in the first direction X.

[0111] The change in the relative positions between the tips of the multiple fingers 4 and the workpiece W can include a change in the relative positions in any direction, as long as the positional relationship between the tips of the multiple fingers 4 and the workpiece W changes. For example, as a search operation, the motion controller 106 causes the hand 2 to reciprocate so that the tips of the multiple fingers 4 repeatedly approach and move away from the workpiece W. For example, the motion controller 106 periodically repeats the approach and movement of the multiple fingers 4 toward and away from the workpiece W. The direction of the reciprocating motion of the hand 2 can be any direction.

[0112] FIG. 18 is a schematic diagram for explaining an example of the search operation of the hand 2. FIG. 19 is a schematic diagram when the retraction of the workpiece W is successful. FIG. 20 is a schematic diagram for explaining the state of the fingers 4 when the workpiece W is retracted. For example, as shown in FIG. 18, the operation controller 106 moves the hand 2 back and forth in the direction of the reference axis P with the reference axis P facing the workpiece W. Since the fingers 4 extend in the direction of the reference axis P, the hand 2 moves in the extension direction of the fingers 4. In other words, in this search operation, the relative positions of the multiple fingers 4 and the workpiece W in the direction of the reference axis P are changed.

[0113] Since the approximate positions of the stacked workpieces W are known by the detector 105, the motion controller 106 moves the fingers 4 toward the workpieces W in the direction of the reference axis P until the tips of the fingers 4 reach the workpieces W. At this time, the motion controller 106 moves the fingers 4 further toward the workpieces W than the position of the workpieces W detected by the detector 105. Because the multiple fingers 4 are elastically displaceable in the second direction Y, even if the fingers 4 contact the workpieces W, the impact on the fingers 4 is absorbed by the elastic displacement of the fingers 4 in the second direction Y. In this way, the tips of the fingers 4 contact one of the workpieces W. Furthermore, due to the elastic deformation of the fingers 4 in the second direction Y, the fingers 4 are elastically pressed against the workpieces W. In other words, the fingers 4 are pressed against the workpieces W with an appropriate force. The motion controller 106 may move the fingers 4 toward the workpieces W until the determiner 107 determines that the tips of the multiple fingers 4 have reached the workpieces W based on the detection result of the sensor 210.

[0114] Since the endless belt 5 is rotating in the retraction direction, when the tips of the fingers 4 come into contact with any of the workpieces W and the workpiece W gets caught between the tips of the fingers 4, the workpiece W is retracted between the fingers 4 by the endless belt 5, as shown in Fig. 19. As the workpiece W is retracted between the fingers 4, each finger 4 is elastically displaced in the first direction X, and the spacing between the fingers 4 is automatically adjusted according to the workpiece W.

[0115] In this example, when the workpiece W is not being pulled in, the portion of the endless belt 5 of one finger 4 that corresponds to the inner surface 4a and the portion of the endless belt 5 of the other finger 4 that corresponds to the inner surface 4a are inclined so that the distance between them narrows toward the tip. As the multiple fingers 4 pull in the workpiece W and each finger 4 is elastically displaced in the first direction X, the portion of the endless belt 5 of one finger 4 that corresponds to the inner surface 4a and the portion of the endless belt 5 of the other finger 4 that corresponds to the inner surface 4a can become parallel or inclined so that the distance between them widens toward the tip.

[0116] In addition to the displacement of the fingers 4 in the first direction X, the endless belt 5 can also elastically deform. When the workpiece W is pulled between the fingers 4, the endless belt 5 can elastically deform toward the opening side of the fingers 4. The elastic deformation of the endless belt 5 also automatically adjusts the spacing between the fingers 4 according to the workpiece W. The endless belt 5 can deform until it comes into contact with the roller 56. In other words, large elastic deformation of the endless belt 5 is limited by the roller 56.

[0117] In addition, since the multiple fingers 4 elastically displace in the second direction Y independently of one another, the workpiece W is more likely to come into contact with the portion of the endless belt 5 of any of the fingers 4 that corresponds to the inner surface 4 a. Specifically, as shown in FIG. 20 , depending on the state of contact between the multiple fingers 4 and the workpiece W, the amount of elastic displacement in the second direction Y may differ among the multiple fingers 4. In other words, one finger 4 (the left finger 4 in FIG. 20 ) is in a state where it advances further in the second direction Y than the other fingers 4. The portion of the endless belt 5 of the finger 4 that advances in the second direction Y that corresponds to the inner surface 4 a is more likely to come into contact with the workpiece W. As a result, the drawing of the workpiece W between the multiple fingers 4 is promoted.

[0118] As a search operation, the motion controller 106 moves the finger 4 to a predetermined position toward the workpiece W, and then moves the tip of the finger 4 away from the workpiece W in the direction of the reference axis P. The motion controller 106 repeatedly moves the finger 4 toward and away from the workpiece W.

[0119] As a search operation, the motion controller 106 may move the hand 2 so that the tips of the fingers 4 move within a plane intersecting the retraction direction of the fingers 4, i.e., a plane intersecting the reference axis P. FIG. 21 is a schematic diagram for explaining another example of a search operation of the hand 2. For example, as shown in FIG. 21 , the motion controller 106 moves the hand 2 so that the tips of the fingers 4 move within a plane perpendicular to the retraction direction of the fingers 4 (i.e., the reference axis P). Note that the plane intersecting the retraction direction of the fingers 4 is not limited to a flat surface, and may also be a curved surface.

[0120] At this time, the motion controller 106 moves the hand 2 so that the tips of the fingers 4 move within a plane intersecting the retraction direction of the workpiece W, with the tips of the fingers 4 in contact with or close to the workpiece W. In this search operation, the relative positions of the fingers 4 and the workpiece W in the direction intersecting the retraction direction of the workpiece W are changed. Preferably, the motion controller 106 moves the hand 2 with the tips of the fingers 4 placed within the collection of workpieces W.

[0121] If the workpiece W fits between the tips of the fingers 4 while the fingers 4 are moving, the workpiece W is pulled between the fingers 4 by the endless belt 5. Even if the workpiece W does not fit between the tips of the fingers 4, the position or posture of the workpiece W changes when the tips of the fingers 4 come into contact with the workpiece W. If the position or posture of the workpiece W changes, the workpiece W can fit between the tips of the fingers 4 and be pulled between the fingers 4.

[0122] In particular, with randomly piled workpieces W, the workpiece W to be pulled in may change depending on the movement of the fingers 4 in a plane intersecting the pulling direction of the fingers 4. In other words, the hand 2 attempts to pull in various workpieces W. This increases the probability that any workpiece W will get stuck between the fingers 4.

[0123] More specifically, the motion controller 106 moves the fingers 4 two-dimensionally within a plane intersecting the retraction direction of the fingers 4. Movement of the fingers 4 within a plane intersecting the retraction direction, i.e., two-dimensional movement when viewed in the retraction direction, includes linear movement and curved movement. For example, the motion controller 106 may move the fingers 4 in a zigzag, rotational, or reciprocating manner within a plane intersecting the retraction direction of the fingers 4. FIG. 22 is a schematic diagram illustrating another example of a search motion of the hand 2. For example, as a search motion, the motion controller 106 may move the hand 2 within a plane intersecting the retraction direction of the fingers 4 so that the fingers 4 rotate around a predetermined rotation axis. The rotation axis may be an axis parallel to the reference axis P or an axis non-parallel to the reference axis P. In the example of FIG. 22 , the rotation axis coincides with the reference axis P. Note that the rotation axis may be an axis eccentric from the reference axis P. That is, rotation includes orbiting, and orbiting includes orbiting on various orbits such as a circular orbit, a spiral orbit, or a polygonal orbit.

[0124] In the search operation, the motion controller 106 may move the hand 2 so that the multiple fingers 4 scan within a predetermined range on a plane intersecting the retraction direction of the multiple fingers 4. For example, the motion controller 106 sets a scanning range including a set of workpieces W based on the multiple workpieces W detected by the detector 105. The motion controller 106 moves the hand 2 so that the multiple fingers 4 move regularly or irregularly within the scanning range.

[0125] Alternatively, the motion controller 106 may move the hand 2 so that the fingers 4 perform a composite movement that combines movement in the retraction direction of the fingers 4 and movement in a direction intersecting the retraction direction of the fingers 4. For example, when the fingers 4 approach or move away from the workpiece W, the motion controller 106 may change the positions of the fingers 4 in a direction intersecting the retraction direction of the fingers 4, or change the angular positions of the fingers 4 around the reference axis P (i.e., rotate).

[0126] When the search operation is started, the determiner 107 determines in step S104 whether or not the workpiece W has been completely drawn between the fingers 4. Because the endless belt 5 is rotating in the drawing-in direction, when the workpiece W fits between the tips of the fingers 4, the endless belt 5 draws the workpiece W between the fingers 4, as shown in FIG. 19 . The determiner 107 determines the drawing status of the workpiece W between the fingers 4 based on the detection results of the sensor 210. For example, a predetermined position in the drawing direction between the fingers 4 is set as the drawing-in completion position of the workpiece W. The determiner 107 detects that the workpiece W has reached the drawing-in completion position based on the detection results of the sensor 210, and determines that the drawing of the workpiece W is complete when the workpiece W reaches the drawing-in completion position.

[0127] If none of the workpieces W is drawn between the fingers 4, the operation controller 106 returns to step S103 and continues the search operation.

[0128] In this way, the operation controller 106 attempts to draw in the workpiece W by bringing the tips of the multiple fingers 4 into contact with the workpiece W. By repeatedly changing the relative positions of the tips of the multiple fingers 4 and the workpiece W, attempts are made repeatedly to draw in the workpiece W into the multiple fingers 4. Even if drawing in the workpiece W fails, the position or posture of the workpiece W changes due to the fingers 4 contacting the workpiece W. Therefore, when drawing in the workpiece W again, there is a possibility that the workpiece W will get stuck between the tips of the multiple fingers 4. Therefore, by repeating the search operation, the operation controller 106 may eventually draw in the workpiece W between the multiple fingers 4.

[0129] In the case of a search operation in which the hand 2 moves so that the tips of the fingers 4 move within a plane intersecting the retraction direction of the fingers 4, the positions of the fingers 4 relative to the workpiece W within the plane intersecting the retraction direction are changed. Even if the accuracy of the positions of the fingers 4 relative to the workpiece W within the plane intersecting the retraction direction is low, the search operation can eventually cause the position of the workpiece W to match the positions of the fingers 4. This simplifies position control of the hand 2.

[0130] In the case of a search operation in which the hand 2 moves so that the multiple fingers 4 rotate around an axis parallel to the retraction direction, the orientation of the multiple fingers 4 with respect to the workpiece W is changed. Eventually, the orientation of the multiple fingers 4 with respect to the workpiece W can be changed so that the workpiece W fits onto the tips of the multiple fingers 4.

[0131] In particular, when the workpieces W are piled up randomly, multiple workpieces W may move when the fingers 4 come into contact with the workpieces W, and when the hand 2 tries to pull in a workpiece W again, it may try to pull in a different workpiece W than the previous time. In other words, the hand 2 tries to pull in various workpieces W. This increases the possibility of successfully pulling in the workpiece W.

[0132] Note that, when the determiner 107 determines that the workpiece W has started to be pulled between the fingers 4 based on the detection result of the sensor 210, the operation controller 106 may temporarily stop the search operation. In other words, the operation controller 106 may maintain only the rotation of the endless belt 5 and temporarily stop the movement of the hand 2.

[0133] When the drawing of the workpiece W is completed, the motion controller 106 ends the search operation in step S105. Specifically, the motion controller 106 stops the rotation of the endless belt 5. In this way, the control device 100 ends the search operation when the sensor 210 detects that the workpiece W has been drawn in.

[0134] Thereafter, in step S106, the motion controller 106 causes the hand 2 and the robot arm 10 to transfer the workpiece W to a predetermined place position. When the pick-and-place process for one workpiece W is completed, the imaging controller 104 executes the process of step S101 again.

[0135] In this pick-and-place process, the control device 100 changes the relative positions of the tips of the fingers 4 and the workpiece W through a search operation, and repeatedly attempts to draw the workpiece W between the fingers 4. The control device 100 continues the search operation to draw the workpiece W between the fingers 4. The control device 100 does not open or close the fingers 4 using the first motor 71 during the search operation. In other words, the control device 100 controls the spacing between the fingers 4 to be constant during the search operation. By repeating the search operation, the fingers 4 naturally grasp the workpiece W that has been drawn between them. The control device 100 can draw the workpiece W between the fingers 4 without highly accurate position control of the fingers 4. Because highly accurate position control of the fingers 4 is not required, high resolution of the camera 15 and high detection performance of the detector 105 are not required.

[0136] More specifically, as a search operation, the hand 2 reciprocates so that the tips of the fingers 4 repeatedly approach and move away from the workpiece W. Even if the workpiece W does not fit between the tips of the fingers 4, the repeated approach and movement of the fingers 4 toward and away from the workpiece W changes the relative position and posture of the workpiece W with respect to the fingers 4. As a result, the workpiece W may eventually fit between the tips of the fingers 4.

[0137] In the search operation, the hand 2 may move so that the tips of the fingers 4 move within a plane intersecting the retraction direction of the fingers 4. In other words, in the search operation, the manner of movement of the hand 2 may be arbitrary as long as the relative positions of the tips of the fingers 4 and the workpiece W change.

[0138] The hand 2 has a sensor 210 that detects the drawing of the workpiece W between the fingers 4, and therefore the control device 100 can easily determine whether the workpiece W has been drawn between the fingers 4. In other words, the control device 100 can determine whether to continue or end the search operation based on the detection result of the sensor 210.

[0139] The hand 2 performs such a retraction grip on a collection of multiple randomly stacked workpieces W. The control device 100 allows the fingers 4 to access the multiple workpieces W, so that any one of the multiple workpieces W can be retracted between the fingers 4 as the situation unfolds, without having to specify a single workpiece W.

[0140] Furthermore, because the fingers 4 are flexible in both the first direction X and the second direction Y, the aforementioned retraction grip can be easily achieved. In other words, the flexibility of the fingers 4 increases the tolerance for the positional accuracy of the fingers 4 during control, resulting in easier and faster control of the hand 2. For example, by moving the hand 2 in the second direction Y when bringing the fingers 4 closer to the workpiece W, even if the fingers 4 interfere with another object, such as the workpiece W, the fingers 4 can elastically displace in the second direction Y. This increases the tolerance for positional errors when bringing the fingers 4 closer to the workpiece W. Alternatively, even if the opening angle of the fingers 4 does not strictly match the size of the workpiece W when gripping the workpiece W with the fingers 4, the fingers 4 can displace in the first direction X according to the size of the workpiece W, allowing the workpiece W to be properly gripped with the fingers 4. This increases the tolerance for positional errors in the opening and closing directions of the fingers 4 when gripping the workpiece W with the fingers 4. In this way, there is increased tolerance for both the positional accuracy of the fingers 4 when the fingers 4 approach other objects including the workpiece W and the positional accuracy of the fingers 4 in the opening and closing directions when gripping the workpiece W. Since the required accuracy for the position of the fingers 4 can be reduced, control of the hand 2 can be simplified, and ultimately, control can be speeded up.

[0141] Furthermore, the portions of the endless belt 5 corresponding to the tips of the fingers 4 are inclined so that the spacing between the multiple fingers 4 widens toward the tips of the fingers 4. This inclined portion of the endless belt 5 functions as a guide for drawing the workpiece W between the multiple fingers 4. By performing a search operation using multiple fingers 4 with tips spaced apart in this manner, it becomes easier to randomly draw the workpiece W between the multiple fingers 4.

[0142] To achieve flexibility in the finger 4, the finger body 42 is supported on the base 41 so as to be elastically displaceable in the first direction X and the second direction Y. Even with this configuration, the rotational driving force of the second motor 81 is appropriately transmitted to the endless belt 5 by the transmitter 82. Specifically, the endless belt 5 is wound around a first pulley 51 and a second pulley 52 disposed on the finger body 42. When the finger body 42 displaces relative to the base 41, the endless belt 5, the first pulley 51, and the second pulley 52 also displace relative to the base 41. Even when the finger body 42 displaces, the rotational driving force is transmitted to the first pulley 51 by the transmitter 82. As a result, even if the driving source for the endless belt 5 is not disposed on the finger body 42, the endless belt 5 disposed on the finger body 42, which displaces relative to the base 41, can be rotated. Because the driving source is not disposed on the finger body 42, the configuration of the finger body 42 can be simplified and the finger body 42 can be made lighter.

[0143] More specifically, the transmitter 82 includes a first transmission pulley 86 provided on the base 41, a second transmission pulley 87 provided on the finger body 42, and a transmission belt 810 wound around the first transmission pulley 86 and the second transmission pulley 87. In other words, the transmitter 82 includes a belt transmission mechanism. The second transmission pulley 87 is displaced relative to the first transmission pulley 86 in response to the relative displacement of the finger body 42 with respect to the base 41, and the transmission belt 810 transmits the rotational driving force from the first transmission pulley 86 to the second transmission pulley 87. In this way, the transmission belt 810 flexibly responds to the relative displacement of the finger body 42 and transmits the rotational driving force from the base 41 to the finger body 42.

[0144] In particular, the pivot axis B of the finger body 42 relative to the base 41 coincides with the axis of the second transmission pulley 87. Therefore, even if the finger body 42 pivots, the relative position of the second transmission pulley 87 relative to the base 41, i.e., the relative position of the second transmission pulley 87 relative to the first transmission pulley 86, does not change. The transmission belt 810 can transmit the rotation of the first transmission pulley 86 to the second transmission pulley 87 without being affected by the pivoting of the finger body 42, i.e., the displacement of the finger body 42 in the first direction X.

[0145] Furthermore, the finger body 42 is supported by the base 41 so as to be swingable around the axis of the first pulley 51. Even when the finger body 42 swings, the axis of the first pulley 51 does not displace. The axis of the first pulley 51 also coincides with the swing axis B of the finger body 42 and the axis of the second transmission pulley 87. In other words, even when the finger body 42 is displaced in the first direction X, the axis of the first pulley 51 and the axis of the second transmission pulley 87 do not displace, and therefore the transmission belt 810 is not affected.

[0146] The support shaft 44 rotatably supports the first pulley 51 and swingably supports the finger body 42. In other words, a common shaft is used to rotatably support the first pulley 51 and to swingably support the finger body 42. This allows the configuration of the finger 4 to be compact.

[0147] In addition, the transmitter 82 includes a first idle pulley 88 and a second idle pulley 89 that apply tension to the transmission belt 810. Even if the second transmission pulley 87 is displaced relative to the first transmission pulley 86, the first idle pulley 88 and the second idle pulley 89 properly maintain the tension of the transmission belt 810. Therefore, even if the finger body 42 is displaced in various directions relative to the base 41, the rotational driving force is properly transmitted to the finger body 42 by the transmission belt 810.

[0148] Furthermore, the first idle pulley 88 and the second idle pulley 89 are supported by a link mechanism 9 connected to each of the base 41 and the finger body 42. Because the first idle pulley 88 and the second idle pulley 89 are supported by the link mechanism 9, the first idle pulley 88 and the second idle pulley 89 are also displaced in accordance with the relative displacement of the finger body 42, and the tension of the transmission belt 810 is maintained.

[0149] More specifically, the link mechanism 9 is a so-called four-bar link mechanism. The first transmission pulley 86 and the second transmission pulley 87 are disposed at one diagonal position, and the first idle pulley 88 and the second idle pulley 89 are disposed at the other diagonal position. When the first transmission pulley 86 and the second transmission pulley 87 approach each other, the first idle pulley 88 and the second idle pulley 89 move away from each other. When the first transmission pulley 86 and the second transmission pulley 87 move away from each other, the first idle pulley 88 and the second idle pulley 89 move toward each other. This maintains the tension of the transmission belt 810.

[0150] Furthermore, the diameters of the pitch circles of the first transmission pulley 86, the second transmission pulley 87, the first idle pulley 88, and the second idle pulley 89 are the same. Therefore, the reaction force of the tension of the portion of the transmission belt 810 wound around each pair of adjacent pulleys acts in a direction connecting the axes of the two pulleys. In other words, the reaction force of the tension of the transmission belt 810 does not act as a moment around the axis of each pulley. As a result, the reaction force of the tension of the transmission belt 810 does not act as a force that displaces the finger body 42, and the position of the finger body 42 is stabilized.

[0151] In this finger 4, the torsion spring 45, which biases the finger body 42 toward the closing side of the finger 4 in the first direction X, is positioned so that its axis is eccentric from the axis of the first pulley 51. When the finger body 42, which is swingably supported on the base 41, is biased in the swing direction by the torsion spring, the axis of the torsion spring tends to be positioned concentric with the center of swing of the finger body 42. In this example, the center of swing of the finger body 42 is the axis of the first pulley 51. However, by positioning the axis of the torsion spring 45 eccentric from the axis of the first pulley 51, it is possible to reduce the number of components aligned in the direction of the axis of the first pulley 51. This allows the size of the finger 4 to be reduced in the direction of the axis of the first pulley 51.

[0152] Next, a description will be given of a modified example of the robot system 1000. In the robot system 1000 according to the modified example, the control device 100 moves the hand 2 and the robot arm 10 to a predetermined position and executes a search operation without detecting the workpiece W by image recognition.

[0153] Specifically, in the robot system 1000, the approximate position of the workpiece W is determined. For example, the workpiece W is placed within a predetermined range, specifically within the container 19. Therefore, the control device 100 moves the hand 2 and the robot arm 10 to a predetermined position corresponding to the workpiece W and executes a search operation. For example, the center of the container 19 in a plan view and a predetermined depth position within the container 19 is set as the start position for the search operation. The control device 100 moves the hand 2 and the robot arm 10 so that the hand 2 is located at the start position, and then executes the search operation. In this case, the control device 100 does not need to know the exact position of the workpiece W, and therefore does not detect the workpiece W. Therefore, the robot system 1000 does not include a camera 15. The processor 101 of the control device 100 does not include an imaging controller 104 or a detector 105.

[0154] By performing the above-described search operation, the workpiece W can be grasped even if the exact position of the workpiece W is not specified, eliminating the need to detect the workpiece W. Furthermore, the positional accuracy requirements for the hand 2 and the robot arm 10 are also relaxed. As a result, the control for pulling in the workpiece W can be simplified.

[0155] Furthermore, in the robot system 1000 according to the modified example, the control device 100 performs a search operation by moving the hand 2 and the robot arm 10 along a predetermined target path without performing path planning for the search operation.

[0156] More specifically, when the approximate position of the workpiece W is fixed, the target path of the robot arm 10 is set in advance. The target path is set so that the hand 2 and the robot 1 move to the approximate position of the workpiece W and perform a search operation. Since the approximate position of the workpiece W is fixed, the target path remains constant. Therefore, the control device 100 does not perform path planning each time a workpiece W is picked. The control device 100 moves the hand 2 and the robot arm 10 along a predetermined target path to perform a search operation. Note that, during the first picking, the control device 100 may perform path planning based on the approximate position of the workpiece W. During subsequent pickings, the control device 100 moves the hand 2 and the robot arm 10 along the already set target path.

[0157] The workpiece W can be grasped by moving the hand 2 to the approximate position of the workpiece W and performing the above-mentioned search operation, eliminating the need for path planning for each individual workpiece W. As a result, control for pulling in the workpiece W can be simplified.

[0158] As another modification, the robot system 1000 may detect the workpiece W by a method other than detection from an image. For example, the robot system 1000 may detect the position of the workpiece W by the sensor 210. That is, since the workpiece W is contained in the container 19, the approximate two-dimensional position of the workpiece W is known. The control device 100 detects the position of the workpiece W in the depth direction of the container 19 based on the detection result of the sensor 210. Specifically, the detector 105 of the control device 100 detects the approximate position of the workpiece W based on the detection result of the sensor 210. The motion controller 106 generates a target path for the robot arm 10 based on the detected position of the workpiece W.

[0159] Even if the sensor 210 roughly detects the workpiece W, the workpiece W can be pulled into the fingers 4 by performing a search operation. Since complex processing such as image recognition is not required, control for pulling in the workpiece W can be simplified.

[0160] Other Embodiments As described above, the above-described embodiments have been described as examples of the technology disclosed in the present application. However, the technology of the present disclosure is not limited to these embodiments and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate. Furthermore, the components described in the above-described embodiments can be combined to create new embodiments. Furthermore, the components described in the accompanying drawings and detailed description may include not only components essential for solving the problem, but also components that are not essential for solving the problem in order to exemplify the technology. Therefore, the fact that these non-essential components are described in the accompanying drawings or detailed description should not be interpreted as immediately determining that these non-essential components are essential.

[0161] For example, the number of fingers 4 included in the hand 2 may be three or more.

[0162] The configuration in which the finger 4 can be elastically displaced in the first direction X is not limited to the configuration described above. The configuration in which the finger 4 can be elastically displaced in the second direction Y is not limited to the configuration described above. The hand 2 may have any configuration as long as the finger 4 can be elastically displaced in the first direction X and the second direction Y. For example, with respect to the first direction X, the finger body 42 may be elastically displaceable in the opening / closing direction A, rather than in an arc-shaped direction centered on the swing axis B. For example, the base 41 of the finger 4 may support the finger body 42 so that it can slide in the opening / closing direction A, and the finger body 42 may be biased toward the closing side of the opening / closing direction A relative to the base 41 by an elastic member such as a spring. As in the example described above, the base 41 is supported by the hand body 3 so as to be movable in the opening / closing direction A, and is driven in the opening / closing direction A by the opening / closing actuator 7. The finger body 42 is elastically displaced in the opening / closing direction A relative to the base 41. In this case, the first direction X is a linear direction in the opening / closing direction A, rather than an arc-shaped direction around the swing axis B as described above.

[0163] With regard to the second direction Y, the hand body 3 may be supported so as to be elastically displaceable relative to the robot arm 10 in the second direction Y. Specifically, the hand 2 may have a guide that supports the hand body 3 so as to be slidable in the second direction Y relative to the robot arm 10, and an elastic member such as a spring that biases the hand body 3 toward the advancing side in the second direction relative to the robot arm 10.

[0164] In the hand 2 in which the finger body 42 is supported so as to be elastically displaceable linearly relative to the base 41 in the opening / closing direction A, with respect to the second direction Y, the finger body 42 may be supported so as to be elastically displaceable relative to the base 41 in the second direction Y, or the hand body 3 may be supported so as to be elastically displaceable in the second direction Y relative to the robot arm 10.

[0165] The transmitter 75 and the transmitter 82 are not limited to the above-described configurations. The transmitter 75 and the transmitter 82 may be modified depending on the configuration of the finger 4. For example, the transmitter 82 may have any configuration depending on the configuration of the finger 4 that is elastically displaceable in the first direction X and the second direction Y. As long as the transmitter 82 transmits the rotational driving force to the first pulley 51, the transmitter 82 may include a gear train instead of or in addition to the belt and pulley.

[0166] The control device 100 does not necessarily have to control the camera 15. For example, the control device 100 may receive an image of the inside of the container 19 from an external source, rather than from the camera 15. Alternatively, the camera 15 may be attached to the robot arm 10. In this case, when the control device 100 causes the camera 15 to acquire an image, the control device 100 controls the robot arm 10 to move the camera 15 to an appropriate shooting position.

[0167] The image used by the control device 100 to detect the workpiece W may be a two-dimensional image. When performing a search operation, the positional accuracy of the finger 4 relative to the workpiece W may be low, and therefore the detection accuracy of the workpiece W may also be low. Therefore, the detection of the workpiece W may be based on a two-dimensional image.

[0168] The robot control device 120 may not be separate from the control device 100, but may be configured integrally with the control device 100. In other words, the control device 100 may also have the functions of the robot control device 120.

[0169] The endless belt 5 does not have to be a timing belt, and the first pulley 51 and the second pulley 52 do not have to be timing pulleys. In other words, the endless belt 5, the first pulley 51, and the second pulley 52 may transmit rotation via frictional force.

[0170] The sensor 210 is not limited to a TOF distance sensor. For example, the sensor 210 may be a triangulation distance sensor. The sensor 210 is not limited to a distance sensor. For example, the sensor 210 may be a current sensor or torque sensor provided on the rotary actuator 8. The control device 100 can determine an increase in the rotational resistance of the endless belt 5 based on the detection result of the current sensor or torque sensor. The control device 100 can determine that the workpiece W has been pulled between the multiple fingers 4 based on the increase in the rotational resistance of the endless belt 5. Alternatively, the sensor 210 may be a sensor that detects contact of the workpiece W with a member such as a lever arranged between the multiple fingers 4.

[0171] In the search operation, the control device 100 may select a specific workpiece W as the target workpiece W rather than multiple workpieces W, and may bring the tips of the multiple fingers 4 into contact with the target workpiece W. For example, individual workpieces W may be dispersedly arranged within the container 19.

[0172] The bottom of the container 19 may not be flat, but may be a curved surface concave downward. In other words, the container 19 may be shaped like a mortar. In this case, even if the workpiece W moves due to contact with the fingers 4 during the search operation, the workpiece W will naturally move to the bottom of the container 19 after the fingers 4 separate from the workpiece W. In other words, even if the search operation is repeated, the workpiece W will return to its predetermined position in the container 19, so there is no need to significantly change the position of the fingers 4 during the search operation.

[0173] The direction of reciprocation of the hand 2 in the search operation may be a direction non-parallel to the reference axis P, i.e., a direction intersecting the reference axis P.

[0174] The determination of the retraction of the workpiece W may or may not be synchronized with the timing of the approach and separation of the fingers 4 to the workpiece W. For example, the control device 100 may determine the retraction of the workpiece W after the approach of the fingers 4 to the workpiece W is complete, and may cause the fingers 4 to separate from the workpiece W if the workpiece W is not retracted. Alternatively, the control device 100 may repeatedly cause the fingers 4 to approach and separate from the workpiece W, and may determine the retraction of the workpiece W regardless of the timing of the approach and separation.

[0175] The flowchart is merely an example. Steps in the flowchart may be changed, replaced, added, omitted, etc. as appropriate. The order of steps in the flowchart may also be changed, and serial processing may be performed in parallel. For example, if the position of the workpiece W is known, steps S101 and S102 may be omitted.

[0176] The functions performed by the components described herein may be implemented in circuitry or processing circuitry, including general-purpose processors, application-specific processors, integrated circuits, ASICs (Application Specific Integrated Circuits), a Central Processing Unit (CPU), conventional circuits, and / or combinations thereof, programmed to perform the described functions. A processor includes transistors and other circuits and is considered a circuit or processing circuit. A processor may also be a programmable processor that executes a program stored in a memory.

[0177] In this specification, a circuit, unit, or means is hardware that is programmed to realize or performs the described functions, which may be any hardware disclosed herein or any hardware known to be programmed to realize or perform the described functions.

[0178] If the hardware is a processor considered to be a type of circuitry, the circuit, means, or unit is a combination of hardware and software used to configure the hardware and / or processor.

[0179] [Aspects] The above-described embodiments are specific examples of the following aspects.

[0180] (Mode 1) A hand 2 includes a hand body 3 and a plurality of fingers 4 provided on the hand body 3 and capable of opening and closing, each of the plurality of fingers 4 having an endless belt 5 wound around at least the tip of the finger 4, which is driven to rotate and comes into contact with a workpiece W, and the fingers 4 are elastically displaceable in a first direction X in which the plurality of fingers 4 open and close, and are elastically displaceable in a second direction Y in which the fingers 4 move toward and away from the hand body 3.

[0181] According to this configuration, by rotating the endless belt 5, the workpiece W can be drawn between the fingers 4 from their tips. Because the fingers 4 are elastically displaceable in the second direction Y, the positional accuracy of the fingers 4 relative to the workpiece W in the second direction Y can be relaxed. For example, even if the fingers 4 overshoot the workpiece W when contacting their tips with the workpiece W, the elastic displacement of the fingers 4 in the second direction Y reduces the mutual impact between the fingers 4 and the workpiece W. Furthermore, when drawing the workpiece W between the fingers 4, the spacing between the fingers 4 is adjusted according to the size of the workpiece W by the elastic displacement of the fingers 4 in the first direction X. In this way, the tolerance for the positional accuracy when the fingers 4 approach the workpiece W and the tolerance for the spacing accuracy of the fingers 4 are increased. In addition, the workpiece W can be grasped by the fingers 4 even if the detection accuracy of the position of the workpiece W is low. Alternatively, if the approximate position of the workpiece W is known, the fingers 4 can grasp the workpiece W without precisely detecting the position of the workpiece W. As a result, it is possible to easily control the hand 2. As a result, it is possible to simplify or speed up the control of the hand 2.

[0182] (Aspect 2) In the hand 2 described in aspect 1, the finger 4 has a base 41 supported by the hand body 3, and a finger body 42 supported on the base 41 so as to be elastically displaceable in the first direction X and supported on the base 41 so as to be elastically displaceable in the second direction Y, and the endless belt 5 is disposed on the finger body 42.

[0183] According to this configuration, the finger 4 has a divided structure including the base 41 and the finger body 42. The finger body 42 can be elastically displaced in the first direction X and the second direction Y relative to the base 41.

[0184] (Aspect 3) The hand 2 according to aspect 1 or 2 further includes a transmitter 82 that transmits a rotational driving force for the endless belt 5, the finger body 42 has a first pulley 51 and a second pulley 52 around which the endless belt 5 is wound, and the transmitter 82 transmits the rotational driving force to the first pulley 51.

[0185] According to this configuration, the endless belt 5, the first pulley 51, and the second pulley 52 are displaced together with the finger body 42 when the finger body 42 is displaced in the first direction X and the second direction Y. The transmitter 82 can transmit the rotational driving force even when the first pulley 51 is displaced together with the finger body 42.

[0186] (Aspect 4) In the hand 2 according to any one of Aspects 1 to 3, the transmitter 82 includes a first transmission pulley 86 provided on the base 41, a second transmission pulley 87 provided on the finger body 42, a transmission belt 810 wound around the first transmission pulley 86 and the second transmission pulley 87, a first idle pulley 88 that applies tension to the transmission belt 810, a second idle pulley 89 that applies tension to the transmission belt 810, and a link mechanism 9 that is connected to the base 41 and the finger body 42, respectively, and supports the first idle pulley 88 and the second idle pulley 89.

[0187] According to this configuration, when the finger body 42 is displaced in the first direction X and the second direction Y, the second transmission pulley 87 is displaced along with the finger body 42. Even in such a case, a rotational driving force is transmitted from the first transmission pulley 86 provided on the base 41 to the second transmission pulley 87 via the transmission belt 810. Tension is applied to this transmission belt 810 by the first idle pulley 88 and the second idle pulley 89. The first idle pulley 88 and the second idle pulley 89 are supported by a link mechanism 9 connected to the base 41 and the finger body 42, respectively. The link mechanism 9 deforms in response to the displacement of the finger body 42. As a result, the first idle pulley 88 and the second idle pulley 89 are maintained in a state in which they appropriately apply tension to the transmission belt 810.

[0188] (Aspect 5) In the hand 2 according to any one of Aspects 1 to 4, the link mechanism 9 includes: a first link 91 rotatably supporting the first idle pulley 88 and coupled to the base 41 rotatably about the axis of the first transmission pulley 86; a second link 92 rotatably supporting the first idle pulley 88 and coupled to the finger body 42 rotatably about the axis of the second transmission pulley 87; a third link 93 rotatably supporting the second idle pulley 89 and coupled to the finger body 42 rotatably about the axis of the second transmission pulley 87; and a fourth link 94 rotatably supporting the second idle pulley 89 and coupled to the base 41 rotatably about the axis of the first transmission pulley 86, and the first transmission pulley 86, the second transmission pulley 87, the first idle pulley 88, and the second idle pulley 89 have the same pitch circle diameter.

[0189] According to this configuration, the link mechanism 9 is a four-bar link. The first transmission pulley 86, the second transmission pulley 87, the first idle pulley 88, and the second idle pulley 89 are arranged at the joints, i.e., pairs, of the four-bar link. The pitch circle diameters of the first transmission pulley 86, the second transmission pulley 87, the first idle pulley 88, and the second idle pulley 89 are the same. Therefore, the reaction force of the tension of the transmission belt 810 acts on each link parallel to the line connecting the joints at both ends. In other words, the reaction force of the tension of the transmission belt 810 does not act as a moment around each joint. Because the reaction force of the tension of the transmission belt 810 does not act as a force that displaces the finger body 42, the position of the finger body 42 is stable.

[0190] (Aspect 6) In the hand 2 according to any one of Aspects 1 to 5, the link mechanism 9 includes: a first link 91 rotatably supporting the first idle pulley 88 and coupled to the base 41 rotatably about the axis of the first transmission pulley 86; a second link 92 rotatably supporting the first idle pulley 88 and coupled to the finger body 42 rotatably about the axis of the second transmission pulley 87; a third link 93 rotatably supporting the second idle pulley 89 and coupled to the finger body 42 rotatably about the axis of the second transmission pulley 87; and a fourth link 94 rotatably supporting the second idle pulley 89 and coupled to the base 41 rotatably about the axis of the first transmission pulley 86, and lengths of the first link 91, the second link 92, the third link 93, and the fourth link 94 are equal to one another.

[0191] According to this configuration, the link mechanism 9 is a four-bar link and an equilateral link in which the lengths of the multiple links are equal to one another, which allows the link mechanism 9 to be made compact.

[0192] (Aspect 7) In the hand 2 according to any one of Aspects 1 to 6, the finger body 42 is supported by the base 41 so as to be swingable around the axis of the first pulley 51, and is displaced in the first direction X by swinging around the axis of the first pulley 51.

[0193] According to this configuration, the oscillation axis B of the finger body 42 and the axis of the first pulley 51 are coaxial. Even when the finger body 42 oscillates relative to the base 41, the axis of the first pulley 51 does not shift. The oscillation of the finger body 42 does not affect the transmission of the rotational driving force to the first pulley 51. Therefore, the rotational driving force can be easily transmitted to the first pulley 51 disposed on the oscillating finger body 42.

[0194] (Aspect 8) The hand 2 according to any one of Aspects 1 to 7 further includes a torsion spring 45 that biases the finger body 42 in the first direction X toward the closing side of the finger 4, and the axis of the torsion spring 45 is located at a position eccentric to the axis of the first pulley 51.

[0195] According to this configuration, by disposing the axis of the torsion spring 45 at a position eccentric to the axis of the first pulley 51, it is possible to reduce the number of members lined up in the direction of the axis of the first pulley 51. This makes it possible to reduce the size of the finger 4 in the direction of the axis of the first pulley 51.

[0196] (Aspect 9) In the hand 2 described in any one of Aspects 1 to 8, the fingers 4 include a first pulley 51 that is driven to rotate, a second pulley 52 that is disposed at the tip of the finger 4, and a third pulley 53 that is disposed between the first pulley 51 and the second pulley 52, the endless belt 5 is wound around the first pulley 51, the second pulley 52, and the third pulley 53, and the spacing between the third pulleys 53 of the multiple fingers 4 is narrower than the spacing between the second pulleys 52 of the multiple fingers 4.

[0197] According to this configuration, the distance between the third pulleys 53 is narrower than the distance between the second pulleys 52, so the distance between the endless belts 5 of the multiple fingers 4 increases from the third pulleys 53 toward the tips of the fingers 4. This makes it easier for the workpiece W to be introduced between the multiple fingers 4 from the tips of the multiple fingers 4. In other words, the workpiece W is more easily drawn into the spaces between the multiple fingers 4.

Claims

1. A hand comprising: a hand body; and a plurality of fingers attached to the hand body that can open and close, each of the plurality of fingers having an endless belt that is wrapped around at least the tip of the finger and is driven to rotate and comes into contact with a workpiece, the fingers being elastically displaceable in a first direction in which the plurality of fingers open and close, and being elastically displaceable in a second direction in which the fingers move toward and away from the hand body.

2. A hand as described in claim 1, wherein the finger has a base supported by the hand body, and a finger body supported on the base so as to be elastically displaceable in the first direction and also supported on the base so as to be elastically displaceable in the second direction, and the endless belt is disposed on the finger body.

3. A hand as described in claim 2, further comprising a transmitter for transmitting a rotational driving force for the endless belt, the finger body having a first pulley and a second pulley around which the endless belt is wound, and the transmitter for transmitting the rotational driving force to the first pulley.

4. A hand as described in claim 3, wherein the transmitter comprises: a first transmission pulley provided on the base; a second transmission pulley provided on the finger body; a transmission belt wound around the first transmission pulley and the second transmission pulley; a first idle pulley that imparts tension to the transmission belt; a second idle pulley that imparts tension to the transmission belt; and a link mechanism that is connected to each of the base and the finger body and supports the first idle pulley and the second idle pulley.

5. A hand as described in claim 4, wherein the link mechanism includes a first link rotatably supporting the first idle pulley and connected to the base so as to be rotatable about the axis of the first transmission pulley, a second link rotatably supporting the first idle pulley and connected to the finger body so as to be rotatable about the axis of the second transmission pulley, a third link rotatably supporting the second idle pulley and connected to the finger body so as to be rotatable about the axis of the second transmission pulley, and a fourth link rotatably supporting the second idle pulley and connected to the base so as to be rotatable about the axis of the first transmission pulley, wherein the diameters of the pitch circles of the first transmission pulley, the second transmission pulley, the first idle pulley and the second idle pulley are the same as each other.

6. A hand as described in claim 4, wherein the link mechanism includes a first link rotatably supporting the first idle pulley and connected to the base so as to be rotatable about the axis of the first transmission pulley, a second link rotatably supporting the first idle pulley and connected to the finger body so as to be rotatable about the axis of the second transmission pulley, a third link rotatably supporting the second idle pulley and connected to the finger body so as to be rotatable about the axis of the second transmission pulley, and a fourth link rotatably supporting the second idle pulley and connected to the base so as to be rotatable about the axis of the first transmission pulley, wherein the first link, the second link, the third link and the fourth link are equal in length to one another.

7. A hand as described in claim 3, wherein the finger body is supported on the base so as to be swingable about the axis of the first pulley, and is displaced in the first direction by swinging about the axis of the first pulley.

8. A hand as described in claim 7, further comprising a torsion spring that biases the finger body in the first direction toward closing the fingers, the axis of the torsion spring being located at a position eccentric to the axis of the first pulley.

9. A hand as described in claim 1, wherein the fingers include a first pulley that is rotatably driven, a second pulley arranged at the tip of the finger, and a third pulley arranged between the first and second pulleys, the endless belt is wound around the first, second and third pulleys, and the distance between the third pulleys of the multiple fingers is narrower than the distance between the first pulleys of the multiple fingers.

Images