Robot hand and control device of the same

Abstract

To provide a robot hand and a control device of the same which can prevent, when gripping a gripping object, a slip between a gripping part and the gripping object from occurring.SOLUTION: A robot hand includes a first finger part 3 and a second finger part 4 arranged facing the first finger part 3 to grip a gripping object O through narrowing the interval between the first finger part 3 and the second finger part 4. The robot hand is given including: the first finger part 3 that is constituted by a first support shaft and a first roller 6 rotatably supported by the first support shaft to contact with the gripping object O; and the second finger part 4 that is constituted by a second support shaft and a second roller 8 rotatably supported by the second support shaft to contact with the gripping object O. The robot hand narrows the interval between the first finger part 3 and the second finger part 4 to grip the gripping object O. A surface of the second roller 8 facing the first roller 6 includes portions whose distances from a rotation center axis of the second roller 8 are different to be capable of contacting with the gripping object O.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a robot hand configured to grasp an object to be grasped with at least two fingers, and a control device for the robot hand. [Background technology]

[0002] Patent Document 1 describes a robot hand configured to grasp an object to be grasped using a pair of gripping pieces that face each other and can approach each other. The gripping pieces are formed as rectangular parallelepipeds with flat gripping surfaces facing the object to be grasped, and the gripping pieces are connected to conforming portions made of elastic members that allow rotation around an axis extending from a base and rotation in the opening and closing directions of the gripping pieces. In other words, when grasping an object to be grasped, the elastic members are deformed by the load received by the gripping pieces from the object to allow the gripping surfaces to conform to the shape of the object to be grasped. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-66368 Summary of the Invention [Problem to be solved by the invention]

[0004] When a gripping object is gripped by a pair of gripping pieces as described in Patent Document 1, a load acts on the gripping object in a direction intersecting the direction of movement of the pair of gripping pieces, depending on the surface shape (inclination angle) of the gripping object where the pair of gripping pieces contact and the position of the center of gravity of the gripping object. As a result, the contact position of the gripping pieces on the gripping object may change during the process of gripping the gripping object with the pair of gripping pieces. For example, with the pair of gripping pieces described in Patent Document 1, depending on the shape and other characteristics of the gripping object, slippage may occur between at least one of the gripping pieces and the gripping object during the process of clamping the gripping object and increasing the gripping force. When such slippage occurs, the frictional force between the gripping object and the gripping pieces may suddenly change, causing a temporary instability, which may prevent the gripping object from being gripped stably.

[0005] This invention was devised with an eye on the above-mentioned technical problems, and aims to provide a robot hand and a control device thereof that can prevent slippage between the gripping part and the object to be grasped during the process of grasping the object. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides a robot hand comprising a first finger portion and a second finger portion provided opposite the first finger portion, and configured to grasp an object to be grasped by narrowing the gap between the first finger portion and the second finger portion, wherein the first finger portion is configured with a first support shaft and a first gripping portion supported by the first support shaft so as to be rotatable on its own axis and to come into contact with the object to be grasped, and the second finger portion is configured with a second support shaft and a second gripping portion supported by the second support shaft so as to be rotatable on its own axis and to come into contact with the object to be grasped, and the surface of the second gripping portion facing the first gripping portion has a portion that can come into contact with the object to be grasped, the portion being at a different distance from the central axis of rotation of the second gripping portion.

[0007] In the present invention, the surface of the second gripping portion facing the first gripping portion may be formed so that the distance from the rotation center axis of the second gripping portion gradually changes.

[0008] The second finger portion in the present invention may further include a return mechanism that returns the rotation angle of the second grip portion relative to the second support shaft to a predetermined initial rotation angle.

[0009] The present invention may include a locking mechanism that maintains the rotation angle of the first gripping portion.

[0010] The first holding portion in this invention may include a rotating shaft rotatably held on the first support shaft, and a plurality of rotating bodies rotatably supported on the rotating shaft, and the rotational center axes of the plurality of rotating bodies may be arranged side by side so that they are at different distances from the rotational center axis of the rotating shaft.

[0011] The robot hand of the present invention may further include another pair of finger portions different from the pair of finger portions including the first finger portion and the second finger portion and configured to grasp a portion of the object to be grasped different from that of the pair of finger portions, wherein the other pair of finger portions includes a third finger portion and a fourth finger portion opposed to the third finger portion and configured to move toward and away from the third finger portion, wherein the third finger portion is configured by a third support shaft and a third gripping portion supported by the third support shaft so as to be rotatable on its own axis and to come into contact with the object to be grasped, and the fourth finger portion is configured by a fourth support shaft and a fourth gripping portion supported by the fourth support shaft so as to be rotatable on its own axis and to come into contact with the object to be grasped.

[0012] The present invention also provides a control device for a robot hand that includes a first finger portion and a second finger portion provided opposite the first finger portion, and that grasps an object to be grasped by narrowing the gap between the first finger portion and the second finger portion, wherein the first finger portion is composed of a first support shaft and a first gripping portion supported by the first support shaft so as to be rotatable and come into contact with the object to be grasped, and the second finger portion is composed of a second support shaft and a second gripping portion supported by the second support shaft so as to be rotatable and come into contact with the object to be grasped. The second gripping unit has a surface facing the first gripping unit that has a different distance from the rotation center axis of the second gripping unit and has a portion that can come into contact with the object to be gripped, and the second gripping unit further includes an actuator that drives at least one of the first finger portion and the second finger portion so as to narrow the gap between the first gripping unit and the second gripping unit, and is configured to determine that the object to be gripped has been gripped when the rate of change of the gap between the first finger portion and the second finger portion is equal to or less than a predetermined rate of change.

[0013] The control device of the robot hand according to the present invention may further include a locking mechanism that maintains the rotation angle of the first gripping unit when the first finger unit and the second finger unit grasp the object to be grasped, and when a rate of change in the distance between the first finger unit and the second finger unit is equal to or less than a predetermined rate of change and it is determined that the object to be grasped has been grasped, the locking mechanism may maintain the rotation angle of the first gripping unit. [Effects of the Invention]

[0014] The robot hand of the present invention is configured to grasp an object to be grasped with first and second finger portions, the first finger portion including a first support shaft and a first gripping portion supported by the first support shaft so as to be rotatable and in contact with the object to be grasped, and the second finger portion including a second support shaft and a second gripping portion supported by the second support shaft so as to be rotatable and in contact with the object to be grasped. Therefore, when a load in a rotational direction acts on the first and second gripping portions during the process of grasping the object to be grasped with the first and second finger portions, the first and second gripping portions rotate, changing their contact position with the object to be grasped and narrowing the distance between the first and second finger portions to grasp the object to be grasped. In other words, the first and second finger portions change their contact position with the object to be grasped while making rolling contact with the object to be grasped. Therefore, during the process of grasping the object to be grasped, slippage between the object to be grasped and the first and second grasping portions can be prevented, and as a result, temporary instability caused by a sudden change in the frictional force between the object to be grasped and the first and second grasping portions can be prevented.

[0015] Furthermore, the surface of the second gripping unit facing the first gripping unit has portions that can come into contact with the object to be gripped, at different distances from the rotation axis of the second gripping unit. Therefore, if the surface of the object to be gripped that contacts the second gripping unit is inclined, for example, when a portion of the surface of the second gripping unit facing the first gripping unit that is farther from the rotation axis of the second gripping unit comes into contact with the object to be gripped, a load acts on the second gripping unit in the rotation direction, causing the second gripping unit to rotate. As a result, a portion of the surface of the second gripping unit facing the first gripping unit that is closer from the rotation axis of the second gripping unit comes into contact with the object to be gripped. In such a case, the distance between the rotation axis of the second gripping unit and the position where the second gripping unit comes into contact with the object to be gripped is shorter than the distance between the rotation axis of the second gripping unit and the portion of the surface of the second gripping unit facing the first gripping unit that is farther from the rotation axis of the second gripping unit. Therefore, unless the distance between the first finger portion and the second finger portion is increased, the rotation of the second gripping portion is restricted. In other words, the second gripping portion rotates on its axis or the first finger portion and the second finger portion approach each other while changing the posture of the object to be gripped until the rotation of the second gripping portion is restricted. As a result, by bringing the first finger portion and the second finger portion closer to each other until the rotation of the second gripping portion is restricted, the object to be gripped can be gripped stably.

[0016] The control device for a robot hand of the present invention also includes an actuator that drives at least one of the first and second finger portions to narrow the gap between the first and second finger portions, and is configured to determine that the object to be grasped has been grasped when the rate of change in the gap between the first and second finger portions is equal to or less than a predetermined rate of change. That is, when the contact position between the second gripping portion and the object to be grasped changes to a position where the first and second gripping portions can stably grasp the object to be grasped during the process of the first and second finger portions approaching each other to grasp the object to be grasped, the gap between the first and second finger portions becomes less likely to change any further, and it is determined that the object to be grasped has been grasped at that point. This eliminates the need for a separate sensor or the like to determine that the object to be grasped has been stably grasped, allowing for the miniaturization of the robot hand. [Brief explanation of the drawings]

[0017] [Figure 1] 1A and 1B are a plan view and a front view for explaining an example of a robot hand according to an embodiment of the present invention. [Figure 2] 2(a) is a cross-sectional view taken along line II in FIG. 1; FIG. 2(b) is a cross-sectional view taken along line II-II in FIG. 2(a) showing a state in which the locking mechanism has been released; and FIG. 2(c) is a cross-sectional view taken along line II-II in FIG. 2(a) showing a state in which the locking mechanism has been locked. [Figure 3] 3(a) is a cross-sectional view taken along line III-III in FIG. 1, and FIG. 3(b) is a cross-sectional view taken along line IV-IV in FIG. 3(a). [Figure 4] 1 is a diagram for explaining the behavior of a robot hand in the process of grasping an object to be grasped. [Figure 5] 10A and 10B are diagrams showing other configurations of the first finger portion. [Figure 6] 6(a) is a front view illustrating a configuration in which a plurality of rollers are provided on a first finger portion, FIG. 6(b) is a side view thereof, and FIG. 6(c) is a cross-sectional view taken along line VV in FIG. 6(b). [Figure 7] FIG. 10 is a diagram showing an example in which a plurality of rollers are arranged in an arc shape. [Figure 8] FIG. 1 is a front view showing an example of a robot hand equipped with two pairs of fingers. DETAILED DESCRIPTION OF THE INVENTION

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following embodiments of the present invention will be described with reference to the accompanying drawings. Note that the following embodiments are merely examples of specific embodiments of the present invention and are not intended to limit the scope of the present invention.

[0019] An example of a robot hand according to an embodiment of the present invention is shown schematically in Figure 1. The robot hand 1 shown in Figure 1 can be connected to the robot arm of a general robot, and includes a base 2, and first and second fingers 3 and 4 arranged opposite each other.

[0020] The base 2 is for supporting each of the fingers 3 and 4, and one end is connected to, for example, a robot arm (not shown) so as to be rotatable around its central axis, and the other end is connected to each of the fingers 3 and 4.

[0021] The first finger 3 shown in FIG. 1 includes a first support shaft 5 connected to the base 2 and moving linearly to approach the second finger 4, and a cylindrical first roller 6 rotatably held on the first support shaft 5. The first support shaft 5 is formed in a cylindrical shape with a bottom that opens on the end face opposite the base 2. The end of the first roller 6 on the first support shaft 5 side is formed with an outer diameter smaller than the inner diameter of the hollow portion of the first support shaft 5. The end of the first roller 6 is inserted into the hollow portion of the first support shaft 5 and is rotatably held by a bearing or the like. The first roller 6 corresponds to the "first gripping portion" in this embodiment of the present invention. The first roller 6 may be rotatably held at a position different from the central axis of the hollow portion of the first support shaft 5.

[0022] Similarly, the second finger 4 is connected to the base 2 and includes a second support shaft 7 that moves linearly to approach the first finger 3, and a second roller 8 that is rotatably held by the second support shaft 7 and is formed of a solid shaft with an elliptical cross section. The second support shaft 7 has a recess that opens to the end face opposite the base 2.

[0023] The end of the second roller 8 on the second support shaft 7 side is formed in a cylindrical shape with an outer diameter smaller than the inner diameter of the recess in the second support shaft 7, and the end of the second roller 8 is inserted into the recess in the second support shaft 7 and is held rotatably (spinning) by a bearing or the like. In other words, the second roller 8 is held so as to rotate about the central axis of the recess in the second support shaft 7. This second roller 8 corresponds to the "second gripping portion" in this embodiment of the present invention. Note that the second roller 8 may be held rotatably at a position different from the central axis of the hollow portion of the second support shaft 7.

[0024] As described above, the second roller 8 is formed to have an elliptical cross section and rotates around the central axis of the shaft inserted into the second support shaft 7. That is, the outer surface of the second roller 8 is configured so that the distance from the central axis of rotation of the second roller 8 gradually changes. Note that the second roller 8 may be formed to have a circular cross section, for example, and the second roller 8 may be rotatably held on the second support shaft 7 so that the central axis of rotation is located at a position radially displaced from the central axis of the second roller 8. Furthermore, the second roller 8 is not limited to having a contact surface whose distance from the central axis of rotation of the second roller 8 changes continuously (gradually), as in the case of an elliptical cross section, and may have any shape as long as it has a portion (a portion that comes into contact with the object to be grasped, described later) whose distance from the central axis of rotation of the second roller 8 varies.

[0025] The first support shaft 5 and the second support shaft 7 can be configured to move linearly by a horizontal movement mechanism driven by an actuator (not shown), such as a linear rail or a ball screw nut (not shown). The first support shaft 5 and the second support shaft 7 can be configured to move independently by independent horizontal movement mechanisms, or a single horizontal movement mechanism can be used to move the first support shaft 5 and the second support shaft 7 linearly. One of the first support shaft 5 and the second support shaft 7 (5) can be configured to be movable, while the other support shaft 7 (5) can be fixed to the base 2. Furthermore, the first support shaft 5 and the second support shaft 7 need not necessarily move linearly, but may be rotatable relative to the base 2, as long as the gap between the first roller 6 and the second roller 8 can be narrowed to grip the object to be gripped.

[0026] Fig. 2(a) shows a cross-sectional view taken along line II in Fig. 1, and Fig. 2(b) and Fig. 2(c) show cross-sectional views taken along line II-II in Fig. 2(a). As described above, a hollow portion 9 is formed in the first support shaft 5, and the end of the first roller 6 is inserted into this hollow portion 9 to be rotatably held. In the example shown in Fig. 2, two bearings 10 and 11 are fitted into the hollow portion 9, and the end of the first roller 6 is held by these bearings 10 and 11.

[0027] A locking mechanism 12 that restricts the rotation of the first roller 6 is provided on the first support shaft 5 alongside the hollow portion 9. This locking mechanism 12 is made up of a cam mechanism and includes a rod 13 that engages with the first roller 6, a disk-shaped rotating part 14 that moves the rod 13 toward and away from the first roller 6, and a motor 15 that drives the rotating part 14. In addition, engagement teeth 16 that engage with the rod 13 are formed on the outer peripheral surface of the part of the first roller 6 that is inserted into the first support shaft 5.

[0028] 2(a), rod 13 is inserted into through-hole 17 formed in the wall surface of hollow portion 9, and is arranged so as to restrict movement in the rotation direction of first roller 6, and has teeth (meshing teeth) 18 formed on its tip surface that mesh with engaging teeth 16 formed on first roller 6. In addition, a cam groove 19 is formed on the upper surface of rotating portion 14, and a cam follower 20 that engages with this cam groove 19 is provided integrally with the end of rod 13.

[0029] The cam mechanism is configured to move cam follower 20 back and forth in the axial direction when rotated by motor 15. In other words, the distance from the center of rotation of rotating part 14 to the point in cam groove 19 where cam follower 20 engages gradually changes according to the rotation angle of rotating part 14.

[0030] 2(b), by rotating motor 15 in the clockwise direction, the distance between the radial position of rotating part 14 where cam follower 20 engages and the center of rotation of rotating part 14 becomes shorter, and meshing teeth 18 formed on the tip of rod 13 become separated from engagement teeth 16 formed on first roller 6, allowing first roller 6 to rotate. Also, by rotating motor 15 in the counterclockwise direction, as shown in FIG. 2(c), the distance between the radial position of rotating part 14 where cam follower 20 engages and the center of rotation of rotating part 14 becomes longer, and meshing teeth 18 formed on the tip of rod 13 engage with engagement teeth 16 formed on first roller 6, restricting rotation of first roller 6. The second support shaft 7 may also be provided with a locking mechanism similar to that of the first support shaft 5.

[0031] A return mechanism 21 is also provided to return the rotation angle (phase) of the second roller 8 to the initial phase when the robot hand 1 is not gripping an object to be grasped. A cross-sectional view taken along line III-III in FIG. 1 is shown in FIG. 3(a) to explain the configuration of the return mechanism 21, and a cross-sectional view taken along line IV-IV in FIG. 3(a) is shown in FIG. 3(b). As shown in FIG. 3, a hollow portion 22 is formed at the end of the second roller 8, and a leaf spring 24 is fixed to the end face (the upper surface in FIG. 3) of the hollow portion 22 and to the bottom surface of a recess 23 formed in the second support shaft 7. Therefore, when the second roller 8 rotates relative to the second support shaft 7, the leaf spring 24 twists, and the elastic force (restoring force) of the leaf spring 24 acts on the second roller 8 so as to reduce the rotation angle (phase) of the second roller 8 relative to the second support shaft 7. Therefore, in the initial state where no load (torque) in the rotational direction is acting on the second roller 8, the rotation angle of the second roller 8 relative to the base 2 or the second support shaft 7 is configured to be maintained at a predetermined specified rotation angle.

[0032] In the example shown here, the initial rotation angle of the second roller 8 is maintained by the leaf spring 24 so that the position on the outer surface of the second roller 8 that is closest to the central axis of the second roller 8 is located on a line passing through the central axes of rotation of the first roller 6 and the second roller 8. The member for maintaining the rotation angle of the second roller 8 at a predetermined rotation angle is not limited to the leaf spring 24, and may be configured by, for example, a torsion coil spring or the like.

[0033] As shown in FIG. 2( a), the robot hand 1 is further provided with an electronic control device (hereinafter referred to as the controller) 25 for controlling the motor 15. The controller 25 is mainly composed of a microcomputer and is configured to control the motor 15 based on input signals and pre-stored arithmetic expressions. Specifically, the controller 25 receives signals from sensors (not shown) that detect the amount of movement of the first support shaft 5 and the second support shaft 7, and determines whether the rate of change in the signal input from the sensor during the process of gripping the object to be gripped (i.e., the rate of change in the distance between the first support shaft 5 and the second support shaft 7) is equal to or less than a predetermined rate of change. If the rate of change in the input signal is equal to or less than the predetermined rate of change, it is considered that the object to be gripped is being stably gripped by the first support shaft 5 and the second support shaft 7. Therefore, if the rate of change in the input signal is equal to or less than the predetermined rate of change, the motor 15 is controlled so that the rod 13 engages with the first roller 6.

[0034] 4 shows a top view for explaining the behavior of the process in which an object to be grasped O placed on the ground or the like is grasped from a horizontal direction by the robot hand 1. The object to be grasped O shown here has a trapezoidal cross section, with one side surface inclined relative to the other side surface that contacts the rollers 6 and 8 of the robot hand 1, and shows an example in which the object to be grasped O is pinched and grasped by the fingers 3 and 4 from both sides in the horizontal direction.

[0035] When grasping this grasp target O, first, as shown in FIG. 4(a), the robot hand 1 is moved to the center of the grasp target O in the front-to-back direction (the up-and-down direction in the figure). Then, the distance between the first roller 6 and the second roller 8 is narrowed to grasp the grasp target O. Note that in the example shown in FIG. 4(b), the first roller 6 contacts the grasp target O before the second roller 8, but the second roller 8 may contact the grasp target O before the first roller 6.

[0036] By further narrowing the gap between the first roller 6 and the second roller 8, the second roller 8 comes into contact with the object to be grasped O, as shown in FIG. 4(c). As described above, the second roller 8 has an elliptical cross section and is longer in the front-to-rear direction than the first roller 6. In addition, the side surface of the object to be grasped O is inclined. Therefore, in FIG. 4(c), the outer peripheral surface of the lower end of the second roller 8 comes into contact with the side surface of the object to be grasped O.

[0037] When the horizontal movement mechanism is controlled to further narrow the distance between the first roller 6 and the second roller 8 from the state shown in Fig. 4(c), a load is applied from the first roller 6 to the object to be grasped O in a direction toward the second roller 8, and a load is applied from the second roller 8 to the object to be grasped O in a direction toward the first roller 6. As shown in Fig. 4(c), the second roller 8 abuts against the inclined surface of the object to be grasped O.

[0038] Therefore, a clockwise moment based on the load applied by the first roller 6 and a clockwise moment based on the load applied by the second roller 8 act on the object to be grasped O. As a result, the object to be grasped O starts to rotate in the clockwise direction as shown in Fig. 4(d). Note that as the object to be grasped O rotates, the moment based on the load applied by the first roller 6 starts to act on the first roller 6 in the counterclockwise direction.

[0039] As a result, the position at which the first roller 6 contacts the object to be grasped O moves relatively toward the front side of the object to be grasped O (toward the bottom in FIG. 4) as the object to be grasped O rotates. As described above, the first roller 6 is held rotatably. Therefore, when the position at which the first roller 6 contacts the object to be grasped O changes relatively, the first roller 6 rotates counterclockwise due to torque based on the frictional force acting on the outer circumferential surface of the first roller 6. In other words, the first roller 6 moves relatively toward the front side of the object to be grasped O (toward the bottom in FIG. 4) as shown in FIG. 4(d) while rolling and contacting the side surface of the object to be grasped O.

[0040] Furthermore, as the object to be grasped O rotates, the position at which the second roller 8 contacts the object to be grasped O moves relatively toward the rear side of the object to be grasped O (upper side in FIG. 4). As described above, the second roller 8 is held rotatably. Therefore, when the position at which the second roller 8 contacts the object to be grasped O changes relatively, a moment based on the reaction force from the object to be grasped O and a moment based on the frictional force acting on the outer peripheral surface of the second roller 8 act on the second roller 8, with the central axis of rotation of the second roller 8 as a fulcrum. As a result, a counterclockwise torque acts on the second roller 8, and the torque causes the second roller 8 to rotate in the counterclockwise direction. That is, the second roller 8 moves relatively toward the rear side of the object to be grasped O (upper side in FIG. 4) as shown in FIG. 4(d) while rolling and contacting the side surface of the object to be grasped O.

[0041] As described above, by bringing the first roller 6 and the second roller 8 closer to each other, the object to be grasped O rotates while maintaining contact between the first roller 6 and the second roller 8, and the contact position of the first roller 6 moves relatively to the front side of the object to be grasped O (lower side in FIG. 4), and further, the contact position of the second roller 8 moves relatively to the rear side of the object to be grasped O (upper side in FIG. 4). Then, as shown in FIG. 4(e), the moment based on the pressing force of the first roller 6 and the moment based on the pressing force of the second roller 8 balance, and the object to be grasped O enters a stable state where it does not rotate.

[0042] Furthermore, the second roller 8 is formed with an elliptical cross section, and the distance between the rotational axis of the second roller 8 and its outer surface gradually changes. Therefore, when the second roller 8 is in contact with the object to be grasped O at a position where the distance from the rotational axis of the second roller 8 is large, the second roller 8 can be moved closer to the first roller 6 while rotating. That is, the second roller 8 moves toward the first roller 6 while rotating toward a position on the outer surface of the second roller 8 where the distance from the rotational axis of the second roller 8 is small. As a result, when the object to be grasped O is grasped in the above-described stable state, the position on the outer surface of the second roller 8 that contacts the object to be grasped O is a position where the distance from the rotational axis of the second roller 8 is small. That is, unless the gap between the first roller 6 and the second roller 8 is widened, the second roller 8 cannot rotate, and the object to be grasped O can be stably grasped.

[0043] Therefore, when the object to be grasped O can be stably grasped, the rate of change of the signal input to the controller 25 from the sensor that detects the amount of movement of the first support shaft 5 and the second support shaft 7 becomes equal to or less than a predetermined rate of change, and the locking mechanism 12 provided on the first support shaft 5 suppresses the rotation of the first roller 6. As a result, the object to be grasped O is maintained in a stably grasped state by the first finger portion 3 and the second finger portion 4.

[0044] Then, after the object to be grasped O is moved and placed at another location, the locking mechanism 12 is released from preventing the first roller 6 from rotating, and then the horizontal movement mechanism is used to separate the first roller 6 and the second roller 8, thereby separating the rollers 6, 8 from the object to be grasped O. By separating the rollers 6, 8 from the object to be grasped O in this manner, the elastic force of the leaf spring 24 causes the second roller 8 to return to its initial rotation angle (phase).

[0045] The robot hand 1 described above is configured to grasp an object to be grasped O with a first finger portion 3 and a second finger portion 4. The first finger portion 3 has a first roller 6 rotatably supported on a first support shaft 5 and in contact with the object to be grasped O. Similarly, the second finger portion 4 has a second roller 8 rotatably supported on a second support shaft 7 and in contact with the object to be grasped O. Therefore, when a load in the rotational direction acts on the first roller 6 and the second roller 8 during the process of grasping the object to be grasped O with the first finger portion 3 and the second finger portion 4, the first roller 6 and the second roller 8 rotate, changing the contact position with the object to be grasped O and narrowing the distance between the first finger portion 3 and the second finger portion 4 to grasp the object to be grasped O. In other words, the first finger portion 3 and the second finger portion 4 change the contact position with the object to be grasped O while making rolling contact with the object to be grasped O. Therefore, in the process of gripping the object to be gripped O, it is possible to prevent the occurrence of a temporary unstable state due to a sudden change in the frictional force between the object to be gripped O and the first roller 6 and the second roller 8.

[0046] Furthermore, the surface of the second roller 8 facing the first roller 6 is formed such that the distance from the center of rotation of the second roller 8 gradually changes. Therefore, if the surface of the object to be grasped O that contacts the second roller 8 is inclined, for example, when a portion of the surface of the second roller 8 facing the first roller 6 that is far from the central axis of rotation of the second roller 8 comes into contact with the object to be grasped O, a load acts on the second roller 8 in the rotational direction, causing the second roller 8 to rotate as shown in FIG. 4. As a result, a portion of the surface of the second roller 8 facing the first roller 6 that is far from the central axis of rotation of the second roller 8 comes into contact with the object to be grasped O. In such a case, the distance between the central axis of rotation of the second roller 8 and the position where the second roller 8 contacts the object to be grasped O is shorter than the distance between the central axis of rotation of the second roller 8 and the portion of the surface of the second roller 8 facing the first roller 6 that is far from the central axis of rotation of the second roller 8.

[0047] Therefore, unless the distance between the first finger 3 and the second finger 4 is increased, the rotation of the second roller 8 is restricted. In other words, the second roller 8 rotates on its axis, or the first finger 3 and the second finger 4 approach each other while the posture of the object to be grasped O changes, until the rotation of the second roller 8 is restricted. As a result, by bringing the first finger 3 and the second finger 4 closer to each other until the rotation of the second roller 8 is restricted, the object to be grasped O can be stably grasped. In other words, because the contact position of the second roller 8 changes while rotating until the object to be grasped O is stably grasped, there is no need to precisely determine the grasping position, and position control of the robot arm can be simplified.

[0048] Furthermore, as described above, the lock mechanism 12 that prevents the first roller 6 from rotating on its own axis is provided, so that the object to be grasped O can be maintained in a stable grasped state.

[0049] Furthermore, by bringing the rollers 6, 8 closer to each other, the object to be grasped O can be stably grasped, and the support shafts 5, 7 cannot approach each other in a state where the object to be grasped O can be stably grasped. Therefore, by detecting the rate of change in the distance between the support shafts 5, 7, it can be estimated that the object to be grasped O is being stably grasped, and there is no need to provide a separate sensor or the like for estimating that the object to be grasped O is being stably grasped, allowing the robot hand 1 to be made smaller.

[0050] Furthermore, when the rate of change of the distance between the support shafts 5, 7 becomes equal to or less than a predetermined rate of change as described above, it is estimated that the object to be grasped O is being stably grasped, and at this time, the rotation of the first roller 6 is suppressed by the locking mechanism 12. Therefore, it is possible to suppress an unintended change from a state in which the object to be grasped O is stably grasped to an unstable state due to, for example, the rotation of the first roller 6.

[0051] Furthermore, by providing a leaf spring 24 to reduce the rotation angle of the second roller 8 when it rotates relative to the second support shaft 7, the rotation angle of the second roller 8 is always constant when it is not gripping the object to be grasped O or when the second roller 8 is not in contact with the object to be grasped O, making it easier to plan operations such as avoiding obstacles when moving the robot hand 1 to a position to grasp the object to be grasped O, and simplifying the control of the robot hand 1.

[0052] Note that the first roller 6 described above only needs to be able to maintain contact with the object to be grasped O by changing the angle between the central axis of rotation of the first roller 6 and the contact position of the object to be grasped O when the posture of the object to be grasped O changes, and may have, for example, an elliptical cross section or a polygonal cross section as shown in Fig. 5, as long as it does not impede the rotation of the first roller 6. When the first roller 6 is configured in this way, when the posture of the object to be grasped O changes and the angle between the central axis of rotation of the first roller 6 and the contact position of the object to be grasped O (contact angle) changes, the first roller 6 rotates, thereby suppressing slippage that accompanies the change in contact angle.

[0053] Furthermore, the first gripping portion in the embodiment of the present invention may be configured with only one roller, or may be configured with a rotating shaft 26 rotatably held on the first support shaft 5, a holding portion 27 extending from the outer circumferential surface of the rotating shaft 26 in the axial direction of the first support shaft 5, and a plurality of rollers 28 arranged linearly on the holding portion 27, as shown in Fig. 6. That is, the rollers 28 are arranged side by side such that the distances between their respective central rotation axes and the central rotation axis of the rotating shaft 26 are different. Note that each roller 28 corresponds to a "rotating body" in the embodiment of the present invention.

[0054] By arranging multiple rollers 28 side by side in this manner, one of the rollers 28 can maintain contact even if the posture of the object to be grasped O changes. In other words, the outer diameter of each roller 28 can be reduced, and the amount of protrusion on the opposite side from the second roller 8 can be reduced, as shown in FIG. 6. As a result, the tip of the first finger portion 3 can be made thinner, and even if there is little gap around the object to be grasped O, the object to be grasped O can be grasped by inserting the tip of the first finger portion 3 into the gap.

[0055] Note that instead of the plurality of rollers 28, a plurality of spheres may be rotatably held in the holding unit 27. The plurality of rollers 28 is not limited to being arranged in a line, but may be arranged in an arc as shown in FIG. 7 or in an elliptical shape. In this way, when the first gripping unit is provided with a plurality of rollers 28 and these rollers 28 are arranged in a line or an arc, it is preferable to provide a return mechanism similar to the example shown in FIG. 3 in order to return the rotation angle of the rotation shaft 26 with respect to the first support shaft 5 to the initial phase in the initial state when the gripping object O is not being gripped.

[0056] Furthermore, the second roller 8 is not limited to one formed with an elliptical cross section, but may be one with a flat contact surface, such as one with a rectangular cross section.

[0057] Furthermore, since the surface of the object to be grasped O may have small irregularities, an elastic material that conforms to the irregularities may be provided on the surfaces of the first roller 6 and the second roller 8. By providing an elastic material on the surfaces of the first roller 6 and the second roller 8 in this way, the elastic material engages (gets caught on) the small irregularities of the object to be grasped O, making it possible to resist a large force in the direction of gravity acting on the object to be grasped O, thereby improving the robustness of the grasp.

[0058] Furthermore, the robot hand according to the embodiment of the present invention is not limited to one that grasps a graspable object O with a pair of fingers 3, 4. For example, as shown in FIG. 8 , the robot hand may include a third finger 30 and a fourth finger 31 configured similarly to the first finger 3. That is, the robot hand may include a third finger 30 configured with a third support shaft (not shown) and a third gripping portion (roller) that is rotatable and contacts the graspable object, and a fourth finger 31 configured with a fourth support shaft (not shown) and a fourth gripping portion (roller) that is rotatable and contacts the graspable object and is further configured to be approachable to the third finger 30. The third finger 30 and the fourth finger 31 may be configured to grasp a portion of the graspable object O that is different from the portion grasped by the pair of fingers of the first finger 3 and the second finger 4. [Explanation of symbols]

[0059] 1. Robot Hand 3,4,30,31 Finger part 5,7 Support shaft 6,8,28 Laura 12 Locking mechanism 13 Rod 14 Rotating part 15 motor 16 engaging teeth 18 Interlocking teeth 19 Cam groove 20 Cam follower 21 Return mechanism 24 Leaf spring 25 Electronic control device (controller) 26 Rotation axis 27 Holding part O Grasped object

Claims

1. A robot hand comprising a first finger portion and a second finger portion provided opposite to the first finger portion, and configured to grasp an object to be grasped by narrowing a gap between the first finger portion and the second finger portion, the first finger portion is configured by a first support shaft and a first gripping portion supported by the first support shaft so as to be rotatable and to come into contact with the object to be gripped, the second finger portion is configured by a second support shaft and a second gripping portion supported by the second support shaft so as to be rotatable and to come into contact with the object to be gripped, The surface of the second gripping part facing the first gripping part has portions that are capable of coming into contact with the object to be gripped and that are at different distances from the rotation center axis of the second gripping part. A robotic hand characterized by:

2. The robot hand according to claim 1, The surface of the second gripping portion facing the first gripping portion is formed so that the distance from the rotation center axis of the second gripping portion gradually changes. A robotic hand characterized by:

3. The robot hand according to claim 1, The second finger portion further includes a return mechanism that returns the rotation angle of the second grip portion relative to the second support shaft to a predetermined initial rotation angle. A robotic hand characterized by:

4. The robot hand according to any one of claims 1 to 3, A locking mechanism is provided to maintain the rotation angle of the first gripping portion. A robotic hand characterized by:

5. The robot hand according to claim 1, the first gripping portion includes a rotating shaft rotatably held by the first support shaft, and a plurality of rotating bodies rotatably supported by the rotating shaft, The plurality of rotating bodies are arranged side by side such that the distances between the respective rotational central axes and the rotational central axis of the rotating shaft are different. A robotic hand characterized by:

6. The robot hand according to claim 1, Further provided is another pair of finger portions that is different from the pair of finger portions including the first finger portion and the second finger portion and that grasps a part of the grasp object that is different from the pair of finger portions, the other pair of fingers includes a third finger and a fourth finger that is provided opposite the third finger and moves toward and away from the third finger, the third finger portion is configured by a third support shaft and a third gripping portion supported by the third support shaft so as to be rotatable and to come into contact with the object to be gripped, The fourth finger portion is configured by a fourth support shaft and a fourth gripping portion supported by the fourth support shaft so as to be rotatable and to come into contact with the object to be gripped. A robotic hand characterized by:

7. A control device for a robot hand that includes a first finger portion and a second finger portion that is provided opposite the first finger portion, and that grasps an object to be grasped by narrowing a gap between the first finger portion and the second finger portion, the first finger portion is configured by a first support shaft and a first gripping portion supported by the first support shaft so as to be rotatable and to come into contact with the object to be gripped, the second finger portion is configured by a second support shaft and a second gripping portion supported by the second support shaft so as to be rotatable and to come into contact with the object to be gripped, a surface of the second gripping portion facing the first gripping portion has portions that are capable of coming into contact with the object to be gripped and that are at different distances from a rotation center axis of the second gripping portion; further comprising an actuator that drives at least one of the first finger portion and the second finger portion so as to narrow the gap between the first grip portion and the second grip portion; The apparatus is configured to determine that the object to be grasped has been grasped when a rate of change in the distance between the first finger portion and the second finger portion is equal to or less than a predetermined rate of change. A control device for a robot hand characterized by:

8. The control device for a robot hand according to claim 7, a locking mechanism that maintains a rotation angle of the first gripping portion when the gripping object is gripped by the first finger portion and the second finger portion, When it is determined that the rate of change in the distance between the first finger portion and the second finger portion is equal to or less than a predetermined rate of change and the object to be grasped is grasped, the locking mechanism maintains the rotation angle of the first gripping portion. A control device for a robot hand characterized by:

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