Robot system

Abstract

To facilitate control for drawing a workpiece.SOLUTION: A robot system 1000 includes: a hand 2; a robot arm 10 with which the hand 2 is connected; and a control device 100 which controls the hand 2 and the robot arm 10. The hand 2 has a hand body 3 and a plurality of fingers 4 which are provided at the hand body 3 and operated to open or close. Each of the fingers 4 has an endless belt 5 which is wound around at least a tip of the finger 4 and is rotationally driven to contact with a workpiece W. The control device 100 causes the hand 2 and the robot arm 10 to perform search operation, in which a relative position of the tips of the fingers 4 and the workpiece W is changed in a state that the fingers 4 are opened at predetermined intervals and the endless belts 5 are rotated, when the tips of the fingers 4 are placed in contact with the workpiece W to draw the workpiece W into a space between the fingers 4 by the endless belts 5.SELECTED DRAWING: Figure 18

Description

[Technical field]

[0001] The technology disclosed herein relates to a robot system. [Background technology]

[0002] Conventionally, there has been known a robot system that grasps a workpiece with the fingers of a hand by drawing the workpiece between the fingers. For example, the hand of a robot system described in Patent Document 1 has fingers with a rotationally driven belt. This robot system moves the hand to a position where the workpiece is pinched between two fingers, and draws the workpiece between the two fingers with the belt. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-24143 A Summary of the Invention [Problem to be solved by the invention]

[0004] When a workpiece is pulled between multiple fingers by a belt, the workpiece is pulled in by fitting 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 in between the multiple fingers. By improving the positional accuracy of the multiple fingers, the workpiece can be pulled in appropriately. However, increasing the positional accuracy of the multiple fingers increases the difficulty of control and slows down the control operation.

[0005] The technology disclosed herein has been made in consideration of the above points, and its purpose is to facilitate control for drawing in a workpiece. [Means for solving the problem]

[0006] The robot system disclosed herein comprises a hand, a robot arm to which the hand is connected, and a control device that controls the hand and the robot arm, the hand having a hand body and a plurality of fingers that are provided on the hand body and 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 rotated, and comes into contact with a workpiece, and the control device causes the hand and the robot arm to execute a search operation that changes the relative position of the tips of the plurality of fingers and the workpiece with a predetermined interval opened and the endless belt rotated when the tips of the plurality of fingers are brought into contact with a workpiece and the workpiece is pulled between the plurality of fingers by the endless belt. Effect of the Invention

[0007] The robot system can facilitate control for pulling in the workpiece. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a robot system. [Diagram 2] FIG. 2 is a front view of the hand. [Diagram 3] FIG. 3 is a bottom view of the hand. [Figure 4] FIG. 4 is a cross-sectional view of the hand taken along line IV-IV in FIG. [Diagram 5] FIG. 5 is a cross-sectional view of the hand taken along line VV in FIG. [Figure 6] FIG. 6 is a cross-sectional view of the hand taken along line VI-VI in FIG. [Figure 7] FIG. 7 is a perspective view of a finger. [Figure 8] FIG. 8 is a side view of a finger. [Figure 9] FIG. 9 is a cross-sectional view of the finger taken along line IX-IX in FIG. [Figure 10] FIG. 10 is a front view of the finger body and the support. [Figure 11]FIG. 11 is a cross-sectional view of the finger taken along line XI-XI in FIG. [Figure 12] FIG. 12 is a perspective view of a finger from a different angle than that of FIG. [Figure 13] FIG. 13 is a front view of a finger. [Figure 14] FIG. 14 is a front view of the finger in a state where the finger body is displaced toward the retreating side in the second direction. [Figure 15] FIG. 15 is a diagram illustrating a schematic hardware configuration of the control device. [Figure 16] FIG. 16 is a block diagram showing the configuration of a control system of the processor. [Figure 17] FIG. 17 is a flow chart of the pick and place process. [Figure 18] FIG. 18 is a schematic diagram for explaining an example of a search operation of the hand. [Figure 19] FIG. 19 is a schematic diagram showing a case where the workpiece is successfully drawn in. [Figure 20] FIG. 20 is a schematic diagram for explaining the state of the fingers when the workpiece is pulled in. [Figure 21] FIG. 21 is a schematic diagram for explaining another example of a search operation of the hand. [Figure 22] FIG. 22 is a schematic diagram for explaining another example of a search operation of the hand. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, exemplary embodiments will be described in detail with reference to the drawings. Fig. 1 is a schematic diagram showing a configuration of a robot system 1000. In the present disclosure, parallel, orthogonal, the same, coincident, simultaneous, or center includes not only strict parallel, orthogonal, the same, coincident, simultaneous, or center, but also substantially parallel, orthogonal, the 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 including 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 randomly piled up in a container 19. However, the robot system 1000 may 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 an operation including translation with at least three degrees of freedom. In this example, the robot arm 10 is a vertical articulated robot arm. The robot arm 10 is supported by a base 13. The robot arm 10 has a plurality of links, a plurality of joints that connect the plurality of links, and a servo motor that rotates and drives 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 can rotate around 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 can rotate around 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 can rotate around 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 can rotate around 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 can rotate around an axis perpendicular to the axis of the fourth link 11d.

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

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

[0017] The robot system 1000 may include a camera 15 that captures 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 captures an image including a plurality of workpieces W in 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, 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 multiple fingers 4 that are provided on the hand body 3 and can open and close. In this example, the hand 2 has two fingers 4. A predetermined reference axis P is set for the hand 2. The fingers 4 extend from the hand body 3 in the direction of the reference axis P, as shown in FIG. 2. The multiple fingers 4 open and close in an opening / closing direction A that is perpendicular to the reference axis P. The reference axis P is located at the center of the multiple fingers 4 in the opening / closing direction A. In other words, when the multiple fingers 4 are in a fully closed state, the multiple 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 contacts the workpiece W. The endless belt 5 is wound 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 referred to as the "opening side", and the side on which the multiple fingers 4 close is referred to as 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 an opening / closing direction A. The multiple fingers 4 approach or move 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 an 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. The hand 2 rotates the endless belt 5 of each finger 4 to pull the workpiece W between the multiple fingers 4 or to feed the workpiece W from between the multiple 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 multiple fingers 4 into contact with the workpiece W and draws the workpiece W between the multiple fingers 4 by the endless belt 5. In another way, the hand 2 grips the workpiece W by opening and closing the multiple fingers 4 in the opening and closing direction A. The hand 2 further has a sensor 210 that detects the drawing of the workpiece W between the multiple fingers 4, as shown in FIG. 3.

[0025] =Finger flexibility= As shown in FIG. 2, the fingers 4 can be elastically displaced in a first direction X in which the fingers 4 open and close. Furthermore, the fingers 4 can be elastically displaced in a second direction Y in which the fingers 4 advance and retreat with respect 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 elastically displaced in the first direction X independently. 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 to the hand body 3 is simply referred to as the "retreating side". In this example, the multiple fingers 4 are elastically displaced in the second direction Y independently.

[0026] FIG. 7 is a perspective view of the finger 4. In FIG. 7, the endless belt 5 is omitted. 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 elastically displaceable 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 around 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 is displaced in the first direction X by swinging around the swing axis B. That is, the first direction X is a circumferential direction centered on the swing axis B.

[0027] The finger body 42 has an elongated shape as shown in Fig. 7. One end of the finger body 42 in the longitudinal direction is referred to as a first end 42a, and the other end of the finger body 42 in the longitudinal direction is referred to as a second end 42b. The first end 42a is the end 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 by 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 in Fig. 8.

[0029] 9, the support 43 supports the support shaft 44 via a bearing so as to be rotatable around 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 around the oscillation axis B. That is, the support 43 supports the finger body 42 via the support shaft 44 so as to be oscillating around 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 be suspended. The longitudinal direction of the finger body 42 suspended from the support 43 coincides with the second direction Y. The finger body 42 swings from this state in the first direction X about the swing axis B. As a result, the finger body 42 is displaced so as to approach or move away from another finger body 42, that is, 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 is in the shape of a long, thin plate. As shown by the two-dot chain line in Fig. 10, when the finger body 42 is displaced 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 oscillation 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 43a and the second stopper 43b 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 roughly coincides with the opening / closing direction A.

[0034] Fig. 11 is a cross-sectional view of the finger 4 taken along line XI-XI in Fig. 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 positioned 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 in the finger body 42. The finger body 42 has a support shaft 42c that supports a coil 45a of the torsion spring 45, and a contact shaft 42d with which a 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 a direction that moves 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 first end 42a of the finger body 42 with respect to the oscillation axis B. The contact shaft 42d is located on the closing side of the finger 4 relative to 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] In a state where no external force is acting on the finger body 42 (i.e., in a 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. That is, the finger body 42 in the normal state can be elastically displaced toward the opening side of the fingers 4.

[0037] Fig. 12 is a perspective view of the finger 4 from a different angle than that of Fig. 7. In Fig. 12, the endless belt 5 is omitted. 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 a direction that moves them away from each other. That is, 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 is displaced toward the retreating side in the second direction Y. In FIG. 14, the spring 47 is illustrated as being partially broken. The finger body 42 can be displaced toward the retreating side in the second direction Y to a position where the pin 41a and the pin 43c come into contact with each other. In other words, the pin 41a and the pin 43c function as stoppers that limit the movement of the finger body 42 in the second direction Y.

[0042] In addition, 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. Also, 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] =Belted Fingers= 11, the finger 4 includes a first pulley 51 that is rotatably driven, a second pulley 52 disposed at the tip of the finger 4, and a third pulley 53 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 parallel to each other. Specifically, the first pulley 51 is rotatably supported by the finger body 42 via a support shaft 44 as shown in FIG. 9. The first pulley 51 is not rotatable with respect 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 a shaft.

[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 in the opening / closing direction A relative to the second pulley 52. ​​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, the finger 4 further includes a fourth pulley 54 and a fifth pulley 55, as shown in FIG. 11. 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 the first pulley 51, the second pulley 52, the third pulley 53, the fourth pulley 54, and the 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 part of the endless belt 5 between the first pulley 51 and the second pulley 52 passing through the third pulley 53 and the fourth pulley 54 is the inner surface 4a of the finger 4. In the normal state, that is, in the finger body 42 in a state where no external force is acting in the first direction X, the part of the endless belt 5 corresponding to the inner surface 4a extends in the second direction Y and faces the closing side in the opening and closing direction A. That is, the part of the endless belt 5 of one finger 4 corresponding to the inner surface 4a and the part 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 part of the endless belt 5 of one finger 4 corresponding to the inner surface 4a and the part of the endless belt 5 of the other finger 4 corresponding to the inner surface 4a are inclined so that the distance between them becomes narrower toward the tip.

[0050] A portion of the endless belt 5 between the second pulley 52 and the third pulley 53 is inclined with respect to a 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 toward the opening side in the opening / closing direction A as it approaches the tip of the finger 4. In other words, the tip of the inner surface 4a of the finger 4 is inclined so as to open toward the opening side in the opening / closing direction A. As a result, the spacing between the multiple fingers 4 at the tip of the fingers 4 widens toward the tip of the finger 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 parallel to each other. 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. More specifically, each roller 56 has a gap between itself 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, the rotation in which the portion corresponding to the inner surface 4a moves toward the first end 42a is referred to as "rotation toward the payout side," and the rotation in which the portion corresponding to the inner surface 4a moves toward the second end 42b is referred to as "rotation toward the retraction side."

[0053] =Opening and closing actuator= 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 a driver of the first motor 71. The first motor 71 is attached to the hand body 3 so that an output shaft 71a 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 by the hand 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 coaxially aligned.

[0056] Each nut 74 is screwed onto the screw 73. One nut 74 is connected to each finger 4. The nut 74 is fixed to the base 41 of the finger 4. The nuts 74 are screwed onto the screw 73, so that the base 41 is supported by the feed screw 72 so as to be movable in the opening / closing direction A. One nut 74 is screwed onto the right-hand thread portion of the screw 73, and the other nut 74 is screwed 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 is formed with a slit 32 extending in the opening / closing direction A. The base 41 fits 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. Since the base 41 fits 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 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. Since 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. The nut 74 and the base 41 move toward the axial direction of the screw 73 as the screw 73 rotates, and as a result, the finger 4 moves in the opening / closing direction A.

[0060] The nut 74 of one finger 4 is screwed into the right-hand thread portion of the screw 73, and the nut 74 of the other finger 4 is screwed into the left-hand thread portion 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 in the opening / closing direction A (i.e., open). Whether the two fingers 4 close or open is switched depending on the rotation direction of the screw 73, i.e., the rotation direction of the first motor 71.

[0061] =Rotation Actuator= 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 83a, a second pulley 83b, a timing belt 83c wound around the first pulley 83a and the second pulley 83b, and a spline shaft 83d to which the second pulley 83b is connected. The first pulley 83a and the second pulley 83b are toothed pulleys, i.e., timing pulleys. The timing belt 83c is a toothed belt. The first transmitter 83 transmits the rotational driving force of the second motor 81 to the spline shaft 83d.

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

[0065] As shown in Fig. 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 wound around the first transmission pulley 86 and the second transmission pulley 87 (see Fig. 8), 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 each of the base 41 and the finger body 42 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 meshing with the first gear 85a. The first gear 85a is supported by the base 41 of the finger 4 so as to be rotatable around an axis C and immovable in the direction of the axis C. More specifically, the first gear 85a is connected to the spline shaft 83d so as to be rotatable around the axis C and movable in the direction of the axis C. The second gear 85b is supported by the base 41 so as to be rotatable around an axis D. The axis D is disposed in a twisted position with respect to the axis C. The axis D is parallel to the rotation axis of the first pulley 51, that is, the oscillation axis B. More 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 by the shaft 85c so as not to be rotatable around the axis D. That is, the second gear 85b is supported by the base 41 via the shaft 85c so as to be rotatable around the 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 by the base 41 so as to be rotatable about the axis D. Specifically, the first transmission pulley 86 is supported by 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 integrally with the second gear 85b about the axis D.

[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. That is, 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 a link mechanism 9 so as to be rotatable about 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 rotatably 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 rotatably around the axis of the second transmission pulley 87, i.e., swing axis B. The third link 93 rotatably supports the second idle pulley 89 and is connected to the finger body 42 rotatably around the axis of the second transmission pulley 87, i.e., swing axis B. The fourth link 94 rotatably supports the second idle pulley 89 and is connected to the base 41 rotatably 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 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 as each other.

[0075] The power transmission belt 810 is an endless belt. The power transmission belt 810 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 disposed on the inside of the power 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 idle pulley 88 and the second idle 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 according 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 according to 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. Since 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 if 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 thus configured, as shown in FIG. 6, when the second motor 81 operates, the rotational driving force of the second motor 81 is transmitted from the first pulley 83a to the second pulley 83b via the timing belt 83c, and the spline shaft 83d rotates around the axis C. When the spline shaft 83d rotates, the first gear 85a of the screw gear 85 rotates integrally with the spline shaft 83d. In response to this, as shown in FIG. 12, the second gear 85b rotates, and the first transmission pulley 86 also rotates integrally with the second gear 85b. 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, and the first pulley 51 rotates 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 according to 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 together with the finger 4 in the opening / closing direction A. More specifically, the first gear 85a is movable in the direction of axis C relative to the spline shaft 83d. Since the 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 if 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 rotate around the axis C. In other words, regardless of the position of the finger 4 in the opening / closing direction A, the rotational driving force of the second motor 81 is transmitted to the first gear 85a via the spline shaft 83d.

[0081] Furthermore, the finger body 42 of the finger 4 is displaced in the first direction X as described above. At this time, the finger body 42 is swung around the swing 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 is swung around the swing axis B, the first pulley 51 and the second transmission pulley 87 are not displaced. 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, the finger body 42 of the finger 4 is displaced in the second direction Y as described above. 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 according 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 according to the link mechanism 9, thereby continuing to apply 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, and the displacement of the finger body 42 in the second direction Y, the endless belt 5 is rotationally driven by the second motor 81.

[0084] The link mechanism 9 is disposed in the hand body 3 as shown in FIG. 2. The fourth link 94 is disposed near the bottom plate 31 of the hand body 3. The finger body 42 is biased toward the advancing side in the second direction Y relative to the base 41 by the spring 47. When the finger body 42 moves toward the advancing side in the second direction Y, the fourth link 94 moves toward the advancing side together with the finger body 42 in the second direction Y. Finally, the second link 92 and the third link 93 come into contact with the bottom plate 31. That is, 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 each other.

[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) type 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 response to 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 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 programs and various data 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 servo motors of the robot arm 10 and the like. 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 unit 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 storage unit 102 stores various programs and various data executed by the processor 101. The storage unit 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 execute a retraction operation in which the tips of the multiple fingers 4 are brought into contact with the workpiece W and the workpiece W is retracted between the multiple fingers 4 by the endless belt 5. During the retraction operation, the processor 101 causes the hand 2 and the robot arm 10 to execute 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 of 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 causes the image from the camera 15 to be stored 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. It is not necessary for the detector 105 to detect the exact position and orientation of the workpiece W. In this example, since the target is loosely piled workpieces W, the detector 105 may detect the approximate position of the collection of loosely piled 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 motor based on the command, so that the robot arm 10 and the hand 2 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 controls the first motor 71 to open and close the fingers 4. The motion controller 106 controls the first motor 71 to adjust the spacing between the multiple fingers 4 to a predetermined value. The motion controller 106 controls the second motor 81 to rotate the endless belt 5. More specifically, the motion controller 106 switches between drawing 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 multiple fingers 4 based on the detection result of the sensor 210. When the distance from the sensor 210 to the workpiece W becomes equal to or less than a predetermined threshold, the determiner 107 determines that the drawing of the workpiece W between the multiple fingers 4 has been completed.

[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 larger than the threshold for determining the retraction of the workpiece W.

[0104] =Robot movement= 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 of pulling the workpiece W between the multiple fingers 4 by the endless belt 5. When performing such a pull-in grip, the control device 100 causes the hand 2 and the robot arm 10 to perform a search operation. Specifically, the operation controller 106 causes the tips of the multiple fingers 4 to contact the workpiece W while rotating the endless belt 5 toward the pull-in side, and further changes the relative positions of the tips of the multiple fingers 4 and the workpiece W. The change in the relative position does not only monotonically decrease or increase the relative distance between the tips of the multiple fingers 4 and the workpiece W, but also includes both a decrease and an increase in the relative distance. In this example, the control device 100 causes the tips of the multiple fingers 4 to approach and move away from a collection of multiple randomly piled workpieces W in the search operation, and causes the tips of the multiple fingers 4 to contact any of the multiple workpieces W. Since the endless belt 5 rotates in the retracting side, when the workpiece W is properly fitted between 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 captures an image of the inside of the container 19. More specifically, the photography controller 104 causes the camera 15 to capture an image of the inside of the container 19.

[0107] In step S102, the detector 105 detects the position of the workpieces W from within the image of the inside of the container 19. For example, the detector 105 detects the approximate position of a collection of the 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 the control device 100 can adjust is a spacing that can be controlled by the first motor 71, and is determined by the spacing between the multiple bases 41. Since each finger 4 is displaceable 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 fingers 4 to be smaller than the size of the workpiece W to be drawn in by a predetermined amount. For example, the size of the target workpiece W is the size of a portion of the target workpiece W that is easy to grasp with the 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 thread. 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 fingers 4 that is enlarged by the elastic displacement of the fingers 4 in the first direction X. In other words, the spacing between the fingers 4 is adjusted to a spacing that allows the workpiece W to be drawn in to fit between the fingers 4 when the fingers 4 are elastically displaced in the first direction X.

[0111] The change in the relative position between the tips of the multiple fingers 4 and the workpiece W may include a change in the relative position in any direction, so long as the positional relationship between the tips of the multiple fingers 4 and the workpiece W changes. For example, the motion controller 106 reciprocates the hand 2 as a search motion 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 may be any direction.

[0112] FIG. 18 is a schematic diagram for explaining an example of a 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 reciprocates the hand 2 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. That is, 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 randomly piled workpieces W are known by the detector 105, the operation controller 106 moves the fingers 4 toward the workpiece W in the direction of the reference axis P until the tips of the fingers 4 reach the workpiece W. At this time, the operation controller 106 moves the fingers 4 toward the workpiece W further than the position of the workpiece W detected by the detector 105. Since the multiple fingers 4 can be elastically displaced in the second direction Y, even if the fingers 4 contact the workpiece 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, the fingers 4 are elastically pressed against the workpiece W by the elastic deformation of the fingers 4 in the second direction Y. In other words, the fingers 4 are pressed against the workpiece W with an appropriate force. The operation controller 106 may move the fingers 4 toward the workpiece W until the determiner 107 determines that the tips of the multiple fingers 4 have reached the workpiece W based on the detection result of the sensor 210.

[0114] Since the endless belt 5 rotates in the retracting side, when the tips of the fingers 4 come into contact with any of the workpieces W and the workpiece W fits 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. When 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 be elastically deformed. When the workpiece W is pulled between the fingers 4, the endless belt 5 can be elastically deformed 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 be deformed until it comes into contact with the roller 56. In other words, the roller 56 limits large elastic deformation of the endless belt 5.

[0117] In addition, since the multiple fingers 4 are elastically displaced in the second direction Y independently of each other, the workpiece W is 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 4a. In detail, 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 of advancing further in the second direction Y than the other fingers 4. The portion of the endless belt 5 of the finger 4 that has advanced in the second direction Y that corresponds to the inner surface 4a is 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 operation 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 operation controller 106 repeats the approach and separation of the finger 4 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 with the retraction direction of the fingers 4, i.e., a plane intersecting with 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 with 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 multiple fingers 4 move within a plane intersecting the retraction direction of the workpiece W, with the tips of the multiple fingers 4 in contact with or close to the workpiece W. In this search operation, the relative positions of the multiple 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 multiple fingers 4 placed within a 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 may fit between the tips of the fingers 4 and be pulled between the fingers 4.

[0122] In particular, for randomly piled workpieces W, the workpieces 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 of the workpieces W will get stuck between the fingers 4.

[0123] More specifically, the motion controller 106 moves the fingers 4 two-dimensionally in a plane intersecting with the retraction direction of the fingers 4. The movement of the fingers 4 in a plane intersecting with the retraction direction, i.e., the 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, rotating, or reciprocating manner in a plane intersecting with the retraction direction of the fingers 4. FIG. 22 is a schematic diagram for explaining another example of the search operation of the hand 2. For example, the motion controller 106 may move the hand 2 as the search operation so that the fingers 4 rotate around a predetermined rotation axis in a plane intersecting with the retraction direction of the fingers 4. 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. 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 multiple fingers 4 perform a composite movement that combines movement in the retracting direction of the multiple fingers 4 and movement in a direction intersecting the retracting direction of the multiple fingers 4. For example, the motion controller 106 may change the positions of the multiple fingers 4 in a direction intersecting the retracting direction of the multiple fingers 4, or change the angular positions of the multiple fingers 4 around the reference axis P (i.e., rotate) when the multiple fingers 4 approach or move away from the workpiece W.

[0126] When the search operation is started, the determiner 107 determines in step S104 whether or not the workpiece W has been drawn between the fingers 4. Since the endless belt 5 is rotating toward the drawing-in side, when the workpiece W fits between the tips of the fingers 4, the workpiece W is drawn between the fingers 4 by the endless belt 5, as shown in FIG. 19. The determiner 107 determines the drawing status of the workpiece W between the fingers 4 based on the detection result of the sensor 210. For example, a predetermined position in the drawing-in 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 result of the sensor 210, and determines the completion of drawing of the workpiece W 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 manner, 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 the workpiece W is drawn in 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 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 position of the workpiece W and the positions of the fingers 4 can eventually match through the search operation. This simplifies the 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, in the case of randomly piled workpieces W, multiple workpieces W may move due to the contact of the fingers 4 with the workpieces W, and when retracting a workpiece W, there is a possibility that the hand 2 may attempt to retract a different workpiece W from the previous one. In other words, the hand 2 attempts to retract various workpieces W. This increases the possibility of successfully retracting the workpiece W.

[0132] In addition, 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 manner, the control device 100 ends the search operation when the sensor 210 detects the drawing of the workpiece W.

[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 such a pick-and-place process, the control device 100 changes the relative positions of the tips of the fingers 4 and the workpiece W by the search operation, and repeats the attempt to draw the workpiece W between the fingers 4. The control device 100 draws the workpiece W between the fingers 4 by continuing the search operation. The control device 100 does not open or close the fingers 4 by the first motor 71 during the search operation. In other words, the control device 100 keeps the interval between the fingers 4 constant during the search operation. By repeating the search operation, the fingers 4 grip the workpiece W drawn between the fingers 4 as a result. The control device 100 can draw the workpiece W between the fingers 4 without performing highly accurate position control of the fingers 4. Since 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 such 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] Since the hand 2 has a sensor 210 that detects the drawing of the workpiece W between the fingers 4, 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 pull-in gripping operation on a collection of multiple randomly piled workpieces W. The control device 100 allows the fingers 4 to access the multiple workpieces W, without specifying one workpiece W, and thereby allows any one of the multiple workpieces W to be pulled in between the fingers 4 as the situation progresses.

[0140] Furthermore, since the fingers 4 have flexibility in both the first direction X and the second direction Y, the retraction gripping as described above can be easily realized. In other words, the flexibility of the fingers 4 increases the tolerance of the positional accuracy of the fingers 4 in the control, and as a result, the control of the hand 2 can be simplified and accelerated. For example, by moving the hand 2 in the second direction Y when the fingers 4 approach the workpiece W, even if the fingers 4 interfere with other objects such as the workpiece W, the fingers 4 can be elastically displaced in the second direction Y. Therefore, the tolerance of the positional error of the hand 2 when the fingers 4 approach the workpiece W or the like increases. Alternatively, even if the opening degree of the fingers 4 does not strictly match the size of the workpiece W when the fingers 4 grip the workpiece W, the fingers 4 are displaced in the first direction X according to the size of the workpiece W, so that the workpiece W can be appropriately gripped by the fingers 4. Therefore, the tolerance of the positional error in the opening and closing direction of the fingers 4 when gripping the workpiece W by the fingers 4 increases. In this way, there is increased tolerance for both the positional accuracy of the fingers 4 when approaching 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 that correspond to the tips of the fingers 4 are inclined so that the spacing between the fingers 4 widens toward the tips of the fingers 4. This inclined portion of the endless belt 5 functions as a guide that draws the workpiece W between the fingers 4. By performing a search operation using the fingers 4 with the tips spaced apart in this manner, it becomes easy to draw the workpiece W randomly between the fingers 4.

[0142] In order to realize the flexibility of 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 in the second direction Y. Even in this configuration, the rotational driving force of the second motor 81 is appropriately transmitted to the endless belt 5 by the transmission device 82. In detail, the endless belt 5 is wound around the first pulley 51 and the second pulley 52 arranged on the finger body 42. When the finger body 42 is displaced relative to the base 41, the endless belt 5, the first pulley 51, and the second pulley 52 are also displaced relative to the base 41. Even if the finger body 42 is displaced, the rotational driving force is transmitted to the first pulley 51 by the transmission device 82. As a result, even in a configuration in which the driving source of the endless belt 5 is not arranged on the finger body 42, the endless belt 5 arranged on the finger body 42, which is displaced relative to the base 41, can be rotated. Since the driving source is not arranged 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. That is, the transmitter 82 includes a belt transmission mechanism. The second transmission pulley 87 is displaced relative to the first transmission pulley 86 in conjunction with 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 transmits the rotational driving force from the base 41 to the finger body 42 in a flexible manner in response to the relative displacement of 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 if 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 oscillation axis B of the finger body 42 and the axis of the second transmission pulley 87. In other words, even if 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, so there is no effect on the transmission belt 810.

[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 finger 4 to have a compact configuration.

[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 tension of the transmission belt 810 is appropriately maintained by the first idle pulley 88 and the second idle pulley 89. Therefore, even if the finger body 42 is displaced in various directions relative to the base 41, the rotational driving force is appropriately 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. Since 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 response to the relative displacement of the finger body 42, and the tension of the transmission belt 810 is maintained.

[0149] 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 of two adjacent pulleys acts in a direction connecting the axial centers 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 axial center 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, so the position of the finger body 42 is stable.

[0151] In such a finger 4, the torsion spring 45 that biases the finger body 42 toward the closing side of the finger 4 in the first direction X is arranged so that its axis is located at a position eccentric from the axis of the first pulley 51. When the finger body 42 supported by the base 41 to be able to swing is biased in the swing direction by the torsion spring, the axis of the torsion spring tends to be arranged concentrically 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 arranging the axis of the torsion spring 45 at a position eccentric from the axis of the first pulley 51, the number of members arranged in the direction of the axis of the first pulley 51 can be reduced. This allows the size of the finger 4 to be reduced in the direction of the axis of the first pulley 51.

[0152] <Modification> 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, in 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 the 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 performing 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 causes the hand 2 and the robot arm 10 to execute the search operation. In this case, the control device 100 does not need to grasp the exact position of the workpiece W, and therefore does not detect the workpiece W. Therefore, the robot system 100 does not include the camera 15. The processor 101 of the control device 100 does not have the imaging controller 104 and the 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, so there is no need to detect the workpiece W. Furthermore, the positional accuracy of the hand 2 and the robot arm 10 is 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 executes 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] 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 10 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 is constant and does not change. Therefore, the control device 100 does not perform path planning every time the workpiece W is picked up. 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, at the time of the first picking, the control device 100 may perform path planning based on the approximate position of the workpiece W. In subsequent picking, the control device 100 moves the hand 2 and the robot arm 10 along the already set target path.

[0157] Since the hand 2 can grasp the workpiece W by moving to the approximate position of the workpiece W and performing the above-mentioned search operation, there is no need to plan a path for each workpiece W. As a result, the control for drawing in the workpiece W can be simplified.

[0158] As another modified example, 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 search operation can be performed to pull the workpiece W into the fingers 4. Since complex processing such as image recognition is not required, the control for pulling in the workpiece W can be simplified.

[0160] Other Embodiments As described above, the above embodiment has been described as an example of the technology disclosed in this application. However, the technology in this disclosure is not limited to this, and can be applied to embodiments in which modifications, replacements, additions, omissions, etc. are appropriately performed. In addition, it is also possible to combine the components described in the above embodiment to form a new embodiment. In addition, among the components described in the attached drawings and detailed description, 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 may be included. Therefore, the fact that these non-essential components are described in the attached drawings and detailed description should not immediately be taken to mean 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 above-mentioned configuration. The configuration in which the finger 4 can be elastically displaced in the second direction Y is not limited to the above-mentioned configuration. As long as the finger 4 is elastically displaced in the first direction X and the second direction Y, the hand 2 may adopt any configuration. For example, with respect to the first direction X, the finger body 42 may be elastically displaceable in the opening / closing direction A, not 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 slidably 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 above-mentioned example, 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, unlike the 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. In particular, 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 in the opening / closing direction A relative to the base 41, with regard to the second direction Y, the finger body 42 may be supported so as to be elastically displaceable in the second direction Y relative to the base 41, 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-mentioned configuration. The transmitter 75 and the transmitter 82 may be changed depending on the configuration of the finger 4. For example, the transmitter 82 may adopt 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 that 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 with respect 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. 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 friction 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 a 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 the torque sensor. The control device 100 can determine that the workpiece W has been drawn 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 that the workpiece W has come into contact 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 work W as the target work W instead of multiple workpieces W, and may bring the tips of the multiple fingers 4 into contact with the target work W. For example, individual workpieces W may be distributed and 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 naturally moves to the bottom of the container 19 after the fingers 4 move away from the workpiece W. In other words, even if the search operation is repeated, the workpiece W returns to a 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, that is, a direction intersecting the reference axis P.

[0174] The determination of the retraction of the workpiece W may be synchronized or not synchronized with the timing of the approach and separation of the fingers 4 from the workpiece W. For example, the control device 100 may execute the determination of the retraction of the workpiece W after the approach of the fingers 4 to the workpiece W is completed, 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 cause the fingers 4 to repeatedly approach and separate from the workpiece W, and execute the determination of 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 be changed, and serial processing may be performed in parallel. For example, when 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 CPU (a Central Processing Unit), conventional circuits, and / or combinations thereof, programmed to perform the functions described. Processors include transistors and other circuits and are considered to be circuits or processing circuitry. A processor may 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 in this specification 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 the hardware and software used to configure the hardware and / or processor.

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

[0180] (Mode 1) A 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 has a hand body 3 and a plurality of fingers 4 that are provided on the hand body 3 and that open and close, and each of the plurality of fingers 4 has an endless belt 5 that is wrapped around at least the tip of the finger 4, is rotated, and comes into contact with a workpiece W. The control device 100 causes the hand 2 and the robot arm 10 to execute a search operation that changes the relative positions of the tips of the plurality of fingers 4 and the workpiece W while opening the plurality of fingers 4 to a predetermined interval and rotating the endless belt 5 when the tips of the plurality of fingers 4 are brought into contact with the workpiece W and the workpiece W is drawn between the plurality of fingers 4 by the endless belt 5.

[0181] According to this configuration, the search operation can change the manner of contact between the tips of the fingers 4 and the workpiece W. As a result, when the workpiece W fits properly between the tips of the fingers 4, the endless belt 5 pulls the workpiece W between the fingers 4. In this way, the search operation can increase the possibility that the workpiece W fits properly between the tips of the fingers 4. By performing the search operation, the workpiece W can be grasped by roughly controlling the position of the hand 2. Since the positional accuracy of the hand 2 is not required, high-precision detection of the workpiece W is also not required. In other words, the control of the hand 2 and the robot arm 10 for grasping the workpiece W can be facilitated.

[0182] (Aspect 2) In the robot system 1000 according to aspect 1, the control device 100 reciprocates the hand 2 so that the tips of the multiple fingers 4 repeatedly approach and move away from the workpiece W as the search operation.

[0183] According to this configuration, even if the workpiece W does not get caught between the tips of the fingers 4 in one contact with the workpiece W, the relative position and posture of the workpiece W with respect to the fingers 4 change as the fingers 4 repeatedly approach and move away from the workpiece W. As a result, the possibility that the workpiece W gets caught between the tips of the fingers 4 increases.

[0184] (Aspect 3) In the robot system 1000 described in aspect 1 or aspect 2, the control device 100 moves the hand 2 as the search operation so that the tips of the multiple fingers 4 move within a plane intersecting a pull-in direction in which the workpiece W is pulled between the multiple fingers 4.

[0185] According to this configuration, the positions of the tips of the multiple fingers 4 relative to the workpiece W are changed in a plane intersecting with the retraction direction. Even if the positions of the multiple fingers 4 are misaligned with respect to the workpiece W in a plane intersecting with the retraction direction, the position of the workpiece W and the positions of the multiple fingers 4 can eventually match by the search operation.

[0186] (Aspect 4) In the robot system 1000 according to any one of aspects 1 to 3, the control device 100 moves the hand as the search operation so that the multiple fingers rotate around an axis parallel to the retraction direction within a plane intersecting the retraction direction.

[0187] According to this configuration, the posture of the multiple fingers 4 with respect to the workpiece W is changed. As a result, the posture of the multiple fingers 4 with respect to the workpiece W can be changed so that the workpiece W will eventually fit onto the tips of the multiple fingers 4.

[0188] (Aspect 5) In the robot system 1000 described in any one of aspects 1 to 4, the control device 100 moves the hand 2 and the robot arm 10 to a predetermined position and executes the search operation without detecting the workpiece W.

[0189] According to this configuration, it is not necessary to detect the workpiece W, which facilitates control for drawing in the workpiece W. The control device 100 can grasp the workpiece W by moving the hand 2 to the approximate position of the workpiece W and executing a search operation.

[0190] (Aspect 6) In the robot system 1000 described in any one of aspects 1 to 5, the control device 100 executes the 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.

[0191] This configuration eliminates the need for path planning, which can facilitate control for drawing in the workpiece W. The control device 100 can grasp the workpiece W by moving the hand 2 along a predetermined target path to the approximate position of the workpiece W and executing a search operation.

[0192] (Aspect 7) In the robot system 1000 described in any one of aspects 1 to 6, the hand 2 further has a sensor 210 that detects the retraction of the workpiece W between the multiple fingers 4, and the control device 100 terminates the search operation when the retraction of the workpiece W is detected by the sensor 210.

[0193] According to this configuration, the completion of the drawing of the workpiece W can be detected by the sensor 210. The drawing of the workpiece W between the multiple fingers 4 will be successful as the situation progresses. By providing the sensor 210, the drawing of the workpiece W between the multiple fingers 4 can be accurately determined, so that the end of the search operation can be determined.

[0194] (Eighth embodiment) In the robot system 1000 according to any one of the first to seventh embodiments, the fingers 4 are elastically displaceable in a first direction X in which the multiple fingers 4 open and close.

[0195] According to this configuration, when the workpiece W is pulled 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. This increases the tolerance for the accuracy of the spacing between the fingers 4. As a result, the control of the hand 2 can be simplified or accelerated.

[0196] (Aspect 9) In the robot system 1000 according to any one of aspects 1 to 8, the predetermined interval between the fingers 4 in the search operation is smaller than the size of the workpiece W to be pulled in.

[0197] According to this configuration, when the workpiece W is drawn between the multiple fingers 4, the fingers 4 are elastically displaced in the first direction X, causing the spacing between the multiple fingers 4 to expand. An elastic force acts on the workpiece W between the multiple fingers 4 from the first direction X. As a result, the multiple fingers 4 can firmly grip the workpiece W.

[0198] (Embodiment 10) In the robot system 1000 according to any one of embodiments 1 to 9, the finger 4 is elastically displaceable in a second direction Y intersecting the opening and closing direction of the finger 4.

[0199] According to this configuration, since the multiple fingers 4 can be elastically displaced in the second direction Y, the positional accuracy of the fingers 4 in the second direction Y relative to the workpiece W can be relaxed. For example, even if the fingers 4 go too far with respect to the workpiece W when the tips of the fingers 4 are brought into contact with the workpiece W, the fingers 4 are elastically displaced in the second direction Y, thereby mitigating the mutual impact between the fingers 4 and the workpiece W. Since the tolerance of the positional accuracy when the fingers 4 approach the workpiece W is increased, the control of the hand 2 can be simplified or accelerated. In addition, even if the detection accuracy of the position of the workpiece W is low, the fingers 4 can grip the workpiece W. Alternatively, if the approximate position of the workpiece W is known, the fingers 4 can grip the workpiece W without strict detection of the position of the workpiece W. As a result, the control of the hand 2 can be facilitated.

[0200] (Mode 11) In the robot system 1000 described in any one of modes 1 to 10, the control device 100, during the search operation, brings the tips of the multiple fingers 4 close to a collection of multiple randomly piled workpieces W and brings the tips of the multiple fingers 4 into contact with any of the multiple workpieces W.

[0201] According to this configuration, the control device 100 can draw in any one of the multiple workpieces W between the multiple fingers 4 by bringing the fingers 4 close to the collection of multiple workpieces W, without having to determine which one is the target workpiece W. Therefore, it is not necessary to detect the position of the workpiece W precisely, and even when the position of the workpiece W is detected, the detection accuracy of the workpiece W can be relaxed. In particular, when the approximate position of the workpiece W is known, detection of the workpiece W is not necessary. Furthermore, since it is sufficient to bring the fingers 4 to the collection of workpieces W, the position accuracy of the hand 2 can be relaxed. [Explanation of symbols]

[0202] 1000 Robot System 100 Control device 2 Hands 210 Sensors 3 Hand body 4 fingers 41 Base 42 Finger body 45 Torsion Spring 5 Endless Belt 51 First pulley 52 No. 2 pulley 53 3rd pulley 82 Transmitter 86 First transmission pulley 87 Second transmission pulley 88 No. 1 idle pulley 89 Second idle pulley 810 Transmission belt 9 Link mechanism 91 First Link 92 Second Link 93 Third Link 94 4th Link Double work X 1st direction Y Second direction

Claims

1. Hand and a robot arm to which the hand is connected; and a control device for controlling the hand and the robot arm, The hand includes a hand body and a plurality of fingers that are provided on the hand body and can open and close; Each of the plurality of fingers has an endless belt that is wound around at least the tip of the finger, is rotated, and contacts the workpiece; The control device is a robot system that causes the hand and the robot arm to perform a search operation that changes the relative positions of the tips of the fingers and the workpiece while spreading the fingers to a predetermined distance and rotating the endless belt when the tips of the fingers come into contact with a workpiece and the workpiece is pulled between the fingers by the endless belt.

2. 2. The robot system according to claim 1, The control device is a robot system that causes the hand to reciprocate as the search operation so that the tips of the multiple fingers repeatedly approach and move away from the workpiece.

3. 2. The robot system according to claim 1, The control device is a robot system that moves the hand as the search operation so that the tips of the multiple fingers move within a plane that intersects with a pull-in direction in which a workpiece is pulled between the multiple fingers.

4. 4. The robot system according to claim 3, The control device is a robot system that moves the hand as the search operation so that the multiple fingers rotate around an axis parallel to the retraction direction within a plane intersecting the retraction direction.

5. 2. The robot system according to claim 1, The control device is a robot system that moves the hand and the robot arm to a predetermined position and executes the search operation without detecting the workpiece.

6. 2. The robot system according to claim 1, The control device executes the search operation by moving the hand and the robot arm along a predetermined target path, without performing path planning for the search operation.

7. 7. The robot system according to claim 1, Further comprising a sensor for detecting the drawing of a workpiece between the plurality of fingers, The control device of the robot system terminates the search operation when the sensor detects the retraction of the workpiece.

8. 7. The robot system according to claim 1, The robotic system, wherein the fingers are elastically displaceable in a first direction in which the fingers open and close.

9. The robot system according to claim 8, A robot system in which the predetermined interval between the multiple fingers during the search operation is smaller than the size of the workpiece to be pulled in.

10. 7. The robot system according to claim 1, The finger is elastically displaceable in a second direction intersecting the opening and closing direction of the finger.

11. 7. The robot system according to claim 1, The control device is a robot system that, during the search operation, brings the tips of multiple fingers close to a collection of multiple randomly stacked workpieces and brings the tips of the multiple fingers into contact with any of the multiple workpieces.

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