Gravity compensation device and manipulator

Abstract

This gravity compensation device comprises: a plurality of links; a plurality of joints that rotatably connect the plurality of links; a plurality of pulleys that are provided to the plurality of joints; a plurality of wires that are fixed to the plurality of links and wound around the plurality of pulleys; a plurality of springs that expand and contract in conjunction with the traction of the plurality of wires; and one or more bases to which the plurality of springs are fixed.

Description

Gravity compensation device and manipulator

[0001] This application claims priority to Japanese Patent Application No. 2024-146862, filed on August 28, 2024, the contents of which are incorporated herein by reference.

[0002] Patent Document 1 below discloses a gravity compensation device that compensates for at least a part of gravity acting on a basic mass. This gravity compensation device includes a balancing system using wires, pulleys, and springs.

[0003] Japan Special Table No. 2008-501595

[0004] Passive gravity compensation can be classified into gravity compensation using a counterweight and gravity compensation using a spring. Gravity compensation using a spring is widely used in robot systems because springs are lightweight. Passive gravity compensation has the advantage of being able to achieve the same performance as active gravity compensation with a smaller actuator and of being able to keep the robot system stationary even if power is lost, resulting in high safety. However, the passive gravity compensation device disclosed in Patent Document 1 is only applicable to link mechanisms with one link and one degree of freedom, and therefore has a problem of limited versatility.

[0005] The present invention has been made in view of the above problems, and has as its object to provide a gravity compensation device with high versatility.

[0006] A gravity compensation device according to one aspect of the present invention comprises a plurality of links, a plurality of joints rotatably connecting the plurality of links, a plurality of pulleys provided at the plurality of joints, a plurality of wires fixed to the plurality of links and wound around the plurality of pulleys, a plurality of springs that expand and contract in conjunction with the pulling of the plurality of wires, and one or more bases to which the plurality of springs are fixed.

[0007] A manipulator according to one aspect of the present invention includes the gravity compensation device described above and a plurality of motors that rotate the plurality of links.

[0008] According to the above aspect of the present invention, a highly versatile gravity compensation device can be provided.

[0009] 9 is a diagram illustrating a configuration of a gravity compensator according to a first embodiment. FIG. 10 is a wiring diagram of a gravity compensator according to the first embodiment. FIG. 10 is a diagram illustrating a configuration of a gravity compensator according to a second embodiment. FIG. 10 is a wiring diagram of a gravity compensator according to the second embodiment. FIG. 11 is a perspective view of a gravity compensator according to a third embodiment. FIG. 12 is a perspective view of the gravity compensator shown in FIG. 5 , seen from the rear and bottom side. FIG. 13 is a perspective view of a gravity compensator according to a first modified example of the third embodiment. FIG. 14 is a perspective view of a gravity compensator according to a second modified example of the third embodiment. FIG. 15 is a perspective view of a manipulator according to a fourth embodiment. FIG. 16 is a perspective view of the manipulator shown in FIG. 9 , seen from the rear and bottom side. FIG. 17 is a front view of a spring element attaching / detaching mechanism according to a fourth embodiment. FIG. 18 is a wiring diagram of a gravity compensator according to a fourth embodiment. FIG. 19 is a graph illustrating experimental results of power consumption of a manipulator according to a fourth embodiment. FIG. 19 is a graph illustrating experimental results of accuracy evaluation of a manipulator according to a fourth embodiment.

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0011] (First embodiment) Fig. 1 is a configuration diagram of a gravity compensator 1 according to a first embodiment. Fig. 2 is a wiring diagram of the gravity compensator 1 according to the first embodiment. The gravity compensator 1 of the first embodiment includes a link mechanism including a plurality of links 10 as shown in Fig. 1, and a passive compensation mechanism that compensates for at least a portion of gravity acting on the link mechanism as shown in Fig. 2.

[0012] As shown in Fig. 1, the link mechanism includes a plurality of links 10, a plurality of joints 20, and a base 30. The plurality of joints 20 are configured as pitch joints that can rotate in a pitch direction. When n (n is an integer) plurality of links 10 are provided, n plurality of joints 20 are provided. Note that although there is one base 30, it may be separated into two or more bases.

[0013] The first link 10-1, which is the first link counting from the base 30, is rotatable around the pitch axis relative to the base 30 by the first joint 20-1, which is the first link counting from the base 30. The second link 10-2, which is the second link counting from the base 30, is rotatable around the pitch axis relative to the first link 10-1 by the second joint 20-2, which is the second link counting from the base 30.

[0014] The passive gravity compensation mechanism compensates for gravity in an n-link-1 degree-of-freedom link mechanism in which each of n links 10 pitch-rotates. To this end, as shown in Fig. 2, the passive gravity compensation mechanism includes a plurality of pulleys 40 provided at the plurality of joints 20, a plurality of wires 50 fixed to the plurality of links 10 and wound around the plurality of pulleys 40, and a plurality of springs 70 that expand and contract in conjunction with the pulling of the plurality of wires 50.

[0015] 2, when n joints 20 are provided, n wires 50 are provided. Also, n springs 70 are provided corresponding to the wires 50. Meanwhile, n-(i-1) pulleys 40 are provided at the ith joint 20-i, which is located at the ith position (i is an integer) counting from the base 30.

[0016] Specifically, n first pulleys 40-1 are attached to the first joint 20-1, which is located first counting from the base 30, so that they can rotate independently. Also, n-1 second pulleys 40-2 are attached to the second joint 20-2, which is located second counting from the base 30, so that they can rotate independently.

[0017] The passive gravity compensation mechanism includes a plurality of arms 60 that rotate in conjunction with the pulling of a plurality of wires 50. As shown in FIG. 2 , when n wires 50 are provided, n arms 60 are also provided. The arms 60 are fixed to a plurality of arm pulleys 61. The arm pulleys 61 are fixed to the wires 50.

[0018] The multiple springs 70 include connection parts 71 that are connected to the arm 60 and rotate, and fixed parts 72 that do not rotate together with the connection parts 71. The connection parts 71 are, for example, one end (movable end) of the springs 70 and are connected to the arm 60. The fixed parts 72 are, for example, the other end (fixed end) of the springs 70 and are connected to the base 30. In other words, when the arm 60 rotates due to the pulling of the wire 50, the connection parts 71 rotate relative to the fixed parts 72, and as a result, the springs 70 expand and contract.

[0019] The multiple wires 50 are fixed to the multiple links 10 and wound around the multiple pulleys 40. Specifically, the first wire 50-1 is fixed to the first link 10-1 that is arranged first counting from the base 30 and wound around the first pulley 40-1 that rotates together with the first link 10-1. The first wire 50-1 is also wound around the first arm pulley 61-1.

[0020] The first wire 50-1 has a first fixed point 51 that rotates together with the first pulley 40-1 and a second fixed point 52 that rotates together with the first arm pulley 61-1. Although the first wire 50-1 is fixed to the first link 10-1 that is disposed first counting from the base 30, the first fixed point 51 may be set on the first pulley 40-1 as shown in Fig. 2 if its movement is equivalent to that of the first link 10-1. The same applies to the second fixed point 52.

[0021] The second second wire 50-2 is fixed to the second link 10-2 located second from the base 30, and is wound around a second pulley 40-2 that rotates together with the second link 10-2. More specifically, the second wire 50-2 is wound around a first pulley 40-1 different from the first pulley 40-1 around which the first wire 50-1 is wound, and a second pulley 40-2.

[0022] In other words, the second wire 50-2 can be pulled independently of the first wire 50-1. Although the second wire 50-2 is not fixed to the first pulley 40-1, it is preferable that slippage does not occur between the second wire 50-2 and the first pulley 40-1. For this reason, a guide pulley (not shown) that guides the wire 50, a tension pulley (not shown) that applies tension to the wire 50, and the like may be provided. The second wire 50-2 is further fixed to the second arm pulley 61-2 to which the second wire 50-2 is connected.

[0023] Similarly, the nth wire 50-n is fixed to the nth link 10-n, which is arranged nth from the base 30, and is wound around the nth pulley 40-n that rotates together with the nth link 10-n. More specifically, the nth wire 50-n is wound around each of the pulleys 40, from the first pulley 40-1, which is the first from the base 30, to the nth pulley 40-n. The nth wire 50-n is also fixed to the nth pulley 40-n and the nth arm pulley 61-n, and can be pulled independently of the other wires 50.

[0024] That is, of the multiple wires 50, the nth wire 50-n wound around the nth pulley 40-n of the nth joint 20-n, which is the nth (n is an integer of 2 or more) counting from the base 30, is wound around each pulley 40 of each of the (n-1)th joints 20 counting from the base 30, and is pulled in conjunction with the rotation angles of each of the (n-1)th joints 20 counting from the base 30. In addition, the nth wire 50-n is fixed to the nth link 10-n, which is the nth link counting from the base 30, of the multiple links 10.

[0025] For example, the third wire 50-3 wound around the third pulley 40-3 of the third joint 20-3, which is the third from the base 30, is fixed to the third link 10-3, which is the third from the base 30, among the multiple links 10. The third wire 50-3 is wound around the first pulley 40-1, which is the first from the base 30, and the second pulley 40-2, which is the second, and is fixed to the third pulley 40-3 of the first joint 20-1, which is the first from the base 30, by the rotation angle θ ｐ１and the rotation angle θ of the second joint 20-2. ｐ２ That is, the third wire 50-3 is pulled in conjunction with the rotation angle θ of the first joint 20-1. ｐ１ The rotation angle θ of the second joint 20-2 is ｐ２ , and the rotation angle θ of the third joint 20-3 is ｐ３ It is pulled in conjunction with the

[0026] Next, the principle of the gravity compensation device 1 having the above configuration will be described.

[0027] According to the above configuration, when the joint (joint 20) rotates, the rotation is transmitted to the spring 70 via the wire 50 and the pulley 40, and when the spring 70 expands and contracts and balances with gravity, the joint does not rotate any further. Here, when the joint is at a different rotation angle, the total potential energy of the gravity compensation device 1 remains constant (total potential energy V Ｔ = Gravitational potential energy V ｇ + Potential energy V due to the elastic force of the spring ｋ = const), the gravity of the robot system is fully compensated.

[0028] In the n-link-1 degree of freedom link mechanism shown in FIG. 1, gravity is compensated for by n springs 70 and n wires 50 shown in FIG. 2. In other words, the i-th wire 50-i (i=1, 2, ..., n) is connected to each joint (pitch joint) from the first joint 20-1 to the i-th joint 20-i, and the rotation of these joints is transmitted to the i-th spring 70-i. Then, the rotation angle (q １ ~q ｎ ) and the rotation angle of each joint (θ ｐ１ ~θ ｐｎ The relationship between these two is expressed by equation (1).

[0029]

[0030] Therefore, the gravitational potential energy V ｇIn equation (2), the gravitational acceleration is g, the number of joints 20 is n (n is an integer), and the mass of the i-th link 10-i is M ｉ and the length of the i-th link 10-i is L ｉ Let the length from the i-th joint 20-i to the center of gravity of the i-th link 10-i be l ｉ and the rotation angle of the i-th spring 70-i is q ｉ The same applies to the following equations.

[0031]

[0032] In addition, the potential energy V due to the elastic force of the spring ｋ In equation (3), the distance from the rotation center of the i-th arm 60-i to the fixed point 72 of the i-th spring 70-i is a ｉ The distance from the rotation center of the i-th arm 60-i to the connection part 71 of the i-th spring 70-i is b ｉ and the spring constant of the i-th spring 70-i is k ｉ The same applies to the following equations.

[0033]

[0034] Then, the total potential energy V Ｔ is expressed as in equation (4).

[0035]

[0036] Here, in order for the gravity compensation device 1 to achieve complete static equilibrium, the total potential energy V Ｔ must be independent of the rotation angle of the joint. The relationship is as shown in equation (5).

[0037]

[0038] That is, the spring constant k of all the springs 70 ｉ can be calculated from equation (6).

[0039]

[0040] As described above, the gravity compensation device 1 according to this embodiment includes a plurality of links 10, a plurality of joints 20 rotatably connecting the plurality of links 10, a plurality of pulleys 40 provided at the plurality of joints 20, a plurality of wires 50 fixed to the plurality of links 10 and wound around the plurality of pulleys 40, a plurality of springs 70 that expand and contract in conjunction with the pulling of the plurality of wires 50, and one or a plurality of bases 30 to which the plurality of springs 70 are fixed. With this configuration, each wire 50 is connected to a respective joint (joint 20) and the rotation of these joints can be transmitted to each spring 70, thereby achieving gravity compensation for a link mechanism other than one link with one degree of freedom. This increases the versatility of the gravity compensation device 1.

[0041] In this embodiment, when the joints 20 are composed of pitch joints that can rotate in a pitch direction and n pitch joints (n is an integer) are provided, n wires 50 are provided and n springs 70 are provided. This configuration makes it possible to realize gravity compensation for an n-link-1 degree-of-freedom link mechanism as shown in FIG.

[0042] In this embodiment, the robot includes a plurality of arms 60 that rotate in conjunction with the pulling of the plurality of wires 50, a plurality of springs 70 that include connection portions 71 that are connected to the plurality of arms 60 and rotate, and fixed points 72 that do not rotate together with the connection portions 71, a plurality of links 10 that include an ith link 10-i that is disposed ith (i is an integer) counting from the base 30, a plurality of joints 20 that include an ith joint 20-i that rotates the ith link 10-i, and a plurality of pulleys 40 that include an ith pulley provided in the ith joint 20-i. The plurality of wires 50 are fixed to the i-th link 10-i and comprise an i-th wire 50-i wound around pulleys 40 from the first pulley 40-1, which is the first pulley counting from the base 30, to the i-th pulley 40-i; the plurality of arms 60 comprise an i-th arm 60-i that rotates in conjunction with the pulling of the i-th wire 50-i; the plurality of springs 70 comprise an i-th spring 70-i connected to the i-th arm 60-i; the gravitational acceleration is g, the number of the plurality of joints 20 is n (n is an integer), and the mass of the i-th link 10-i is M ｉand the length of the i-th link 10-i is L ｉ Let the length from the i-th joint 20-i to the center of gravity of the i-th link 10-i be l ｉ and the distance from the rotation center of the i-th arm 60-i to the fixed point 72 of the i-th spring 70-i is a ｉ The distance from the rotation center of the i-th arm 60-i to the connection part 71 of the i-th spring 70-i is b ｉ and the spring constant of the i-th spring 70-i is k ｉ When the above equation (6) is satisfied, this configuration allows the gravity compensation device 1 to achieve perfect static equilibrium.

[0043] Second Embodiment Next, a second embodiment of the present invention will be described. In the following description, the same or equivalent components as those in the above-described embodiment will be denoted by the same reference numerals, and the description thereof will be simplified or omitted.

[0044] Fig. 3 is a configuration diagram of the gravity compensator 1 according to the second embodiment. Fig. 4 is a wiring diagram of the gravity compensator 1 according to the second embodiment. As shown in Fig. 3, the gravity compensator 1 of the second embodiment includes a link mechanism including a plurality of links 10 capable of pitch rotation and roll rotation, and a passive compensation mechanism that compensates for at least a portion of the gravity acting on the link mechanism.

[0045] As shown in Fig. 3, the link mechanism includes a plurality of links 10, a plurality of joints 20, and a base 30. The plurality of joints 20 are composed of pitch joints that can rotate in pitch direction and roll joints that can rotate in roll direction. The pitch joints and roll joints are arranged alternately. When n (n is an integer) plurality of links 10 are provided, n pitch joints and n roll joints are provided.

[0046] Specifically, the first link 10-1, which is the first link counting from the base 30, is rotatable about the pitch axis relative to the base 30 by a first joint 20-1 (pitch joint), which is the first link counting from the base 30, and is rotatable about the roll axis relative to the base 30 by a second joint 20-2 (roll joint), which is the second link counting from the base 30. The second link 10-2, which is the second link counting from the base 30, is rotatable about the pitch axis relative to the first link 10-1 by a third joint 20-3 (pitch joint), which is the third link counting from the base 30, and is rotatable about the roll axis relative to the first link 10-1 by a fourth joint 20-4 (roll joint), which is the fourth link counting from the base 30.

[0047] The passive gravity compensation mechanism compensates for gravity in an n-link, two-degree-of-freedom link mechanism in which each of n links 10 rotates in pitch and roll. To this end, the passive gravity compensation mechanism includes, as shown in Fig. 4, a plurality of pulleys 40 provided at the plurality of joints 20, a plurality of wires 50 fixed to the plurality of links 10 and wound around the plurality of pulleys 40, and a plurality of springs 70 that expand and contract in conjunction with the pulling of the plurality of wires 50.

[0048] 4, when n pitch joints and n roll joints are provided, 2×n wires 50 are provided. Also, 2×n springs 70 are provided corresponding to the wires 50. Meanwhile, 2×n-2(i-1) pulleys 40 are provided for each joint 20 (pitch joints and roll joints) that rotates the ith link 10-i (i is an integer) located at the ith position counting from the base 30.

[0049] Specifically, 2×n first pulleys 40-1 are attached to a first joint 20-1 (pitch joint) that pitch rotates the first link 10-1, which is located first counting from the base 30. Also, 2×n second pulleys 40-2 are attached to a second joint 20-2 (roll joint) that rolls the first link 10-1, so that they can rotate independently.

[0050] Furthermore, 2×n−2 third pulleys 40-3 are attached to a third joint 20-3 (pitch joint) that pitch rotates the second link 10-2, which is disposed second from the base 30. Furthermore, 2×n−2 fourth pulleys 40-4 are attached to a fourth joint 20-4 (roll joint) that rolls the second link 10-2, and each of them is attached to a fourth joint 20-4 (roll joint) that rolls the second link 10-2.

[0051] The passive gravity compensation mechanism includes a plurality of arms 60 that rotate in conjunction with the pulling of a plurality of wires 50. As shown in Fig. 4, when 2 x n wires 50 are provided, 2 x n arms 60 are also provided. The 2 x n arms 60 are connected to 2 x n springs 70 and fixed to 2 x n arm pulleys 61.

[0052] The 2×n wires 50 include 2×i−1 odd-numbered wires (parallel wires) wound in parallel around the pulleys 40, and 2×i even-numbered wires (cross wires) wound alternately across the pulleys 40. Specifically, the first first wire 50-1 (odd-numbered wire) is wound in parallel around the first pulley 40-1 and the second pulley 40-2, counting from the base 30. Here, "wound in parallel" means that the pulleys 40 rotate in the same direction when the wire 50 is pulled.

[0053] The second second wire 50-2 (even-numbered wire) is wound around the first pulley 40-1, which is located first, and the second pulley 40-2, which is located second, counting from the base 30. In other words, an intersection 53 where the second wire 50-2 crosses is formed between the first pulley 40-1 and the second pulley 40-2. Here, "wound around crossing" means that when the wire 50 is pulled, the pulleys 40 located on both sides of the intersection 53 rotate in opposite directions.

[0054] In the second embodiment, the nth wire 50-n, which is wound around the nth pulley 40-n of the nth joint 20-n (n is an integer of 2 or more) of the multiple wires 50 counting from the base 30, is wound around each pulley 40 of each of the (n-1)th joints 20 counting from the base 30, and is pulled in conjunction with the rotation angles of the (n-1)th joints 20 counting from the base 30. The nth wire 50-n is fixed to the nth link 10-n, which is the nth link of the multiple links 10 counting from the base 30.

[0055] Next, the principle of the gravity compensation device 1 having the above configuration will be described.

[0056] In the n-link-2-degree-of-freedom link mechanism shown in FIG. 3, gravity is compensated for by 2×n springs 70 and 2×n wires 50 shown in FIG. 4. In other words, the 2×i-1th (i=1, 2, ..., n) odd-numbered wire and the 2×ith even-numbered wire are connected to the joints (pitch joints and roll joints) of the first link 10-1 to the joints (pitch joints and roll joints) of the i-th link 10-i, respectively, and the rotation of these joints is transmitted to the 2×i-1th spring 70 and the 2×ith spring 70. However, the 2×i-1th wires 50 (odd-numbered wires) are all connected in parallel, and the 2×ith wires 50 (even-numbered wires) are all connected crosswise. Therefore, the rotation angle (q １ ~q ２ｎ ) and the rotation angle of each joint (θ ｐ１ ~θ ｐｎ , θ ｒ１ ~θ ｒｎ ) is expressed as in equation (7).

[0057]

[0058] Therefore, the gravitational potential energy V ｇ is expressed as in equation (8).

[0059]

[0060] In addition, the potential energy V due to the elastic force of the spring ｋ is expressed as in equation (9).

[0061]

[0062] Then, the total potential energy V Ｔ is expressed as in equation (10).

[0063]

[0064] Here, in order for the gravity compensation device 1 to achieve complete static equilibrium, the total potential energy V Ｔ must be independent of the rotation angle of the joint. The relationship is as shown in equation (11).

[0065]

[0066] That is, the spring constant k of all the springs 70 ｉ can be calculated from equation (12). Note that equation (12) is the same as equation (6) in the first embodiment described above.

[0067]

[0068] As described above, in the gravity compensation device 1 according to the second embodiment, when the multiple joints 20 are composed of pitch joints capable of pitch rotation and roll joints capable of roll rotation, and when n pitch joints and n roll joints (n is an integer) are provided, 2×n wires 50 and 2×n springs 70 are provided. With this configuration, gravity compensation can be achieved for an n-link, 2-degree-of-freedom link mechanism as shown in FIG.

[0069] In the second embodiment, the 2×n wires 50 include 2×i−1 (i is an integer) odd-numbered wires wound in parallel around the pulleys 40, and 2×i even-numbered wires wound in an alternating cross pattern around the pulleys 40. By using such a fixed wire wiring pattern, gravity compensation for both pitch rotation and roll rotation can be achieved.

[0070] In this embodiment, the robot includes a plurality of arms 60 that rotate in conjunction with the pulling of the plurality of wires 50, a plurality of springs 70 that include connection portions 71 that are connected to the plurality of arms 60 and rotate, and fixed points 72 that do not rotate together with the connection portions 71, a plurality of links 10 that include an ith link 10-i that is disposed ith (i is an integer) counting from the base 30, a plurality of joints 20 that include an ith joint 20-i that rotates the ith link 10-i, and a plurality of pulleys 40 that include an ith pulley provided in the ith joint 20-i. The plurality of wires 50 are fixed to the i-th link 10-i and comprise an i-th wire 50-i wound around pulleys 40 from the first pulley 40-1, which is the first pulley counting from the base 30, to the i-th pulley 40-i; the plurality of arms 60 comprise an i-th arm 60-i that rotates in conjunction with the pulling of the i-th wire 50-i; the plurality of springs 70 comprise an i-th spring 70-i connected to the i-th arm 60-i; the gravitational acceleration is g, the number of the plurality of joints 20 is n (n is an integer), and the mass of the i-th link 10-i is M ｉ and the length of the i-th link 10-i is L ｉ Let the length from the i-th joint 20-i to the center of gravity of the i-th link 10-i be l ｉ and the distance from the rotation center of the i-th arm 60-i to the fixed point 72 of the i-th spring 70-i is a ｉ The distance from the rotation center of the i-th arm 60-i to the connection part 71 of the i-th spring 70-i is b ｉ and the spring constant of the i-th spring 70-i is k ｉ When the above equation (12) is satisfied, this configuration allows the gravity compensation device 1 to achieve complete static equilibrium.

[0071] Third Embodiment Next, a third embodiment of the present invention will be described. In the following description, the same or equivalent components as those in the above-described embodiment will be denoted by the same reference numerals, and the description thereof will be simplified or omitted.

[0072] Fig. 5 is a perspective view of a gravity compensator 1 according to a third embodiment. Fig. 6 is a perspective view of the gravity compensator 1 shown in Fig. 5, seen from the rear and bottom. The gravity compensator 1 of the third embodiment includes a one-link, two-degree-of-freedom link mechanism and a passive compensation mechanism that compensates for at least a portion of gravity acting on the link mechanism.

[0073] The one-link, two-degree-of-freedom link mechanism is provided with one pitch joint and one roll joint (not shown). In this case, two wires 50 are provided. Two springs 70 are provided corresponding to the two wires 50. Two arms 60 are also provided. The two arms 60 are connected to the two springs 70 and fixed to two arm pulleys 61.

[0074] One end of the spring 70 is fixed to the arm 60 via a connecting wire, and the other end of the spring 70 is directly fixed to the base 30. The connecting wire is pinched by the pinch pulley 31. In this case, the connection part 71 is the end of the connecting wire that is connected to the arm 60 and rotates. The fixed point part 72 is the clamped part of the connecting wire that is pinched by the pinch pulley 31.

[0075] There are two first pulleys 40-1 located first from the base 30. The two first pulleys 40-1 are provided as a pair at a pitch joint (not shown) and are rotatable independently of each other. There are also two second pulleys 40-2 located second from the base 30. The two second pulleys 40-2 are provided as a pair at a roll joint (not shown) and are rotatable independently of each other.

[0076] The rotation axes (common axes) of the two first pulleys 40-1 and the rotation axes (common axes) of the two second pulleys 40-2 are perpendicular to each other. The first link 10-1 is fixed to each of the two second pulleys 40-2. As shown in FIG. 4, the first wire 50-1 (odd-numbered wire) is wound in parallel around the first pulley 40-1 (one of a pair of first pulleys) located first and the second pulley 40-2 (one of a pair of second pulleys) located second, counting from the base 30.

[0077] 5, the second wire 50-2 (even-numbered wire) is wound around and crosses the first pulley 40-1 (the other of the pair of first pulleys) located first and the second pulley 40-2 (the other of the pair of second pulleys) located second, counting from the base 30. In other words, an intersection 53 of the second wire 50-2 is formed between the first pulley 40-1 and the second pulley 40-2.

[0078] The operating principle of the gravity compensator 1 of the third embodiment configured as described above is the same as that of the second embodiment described above. Therefore, the gravity compensator 1 of the third embodiment can achieve gravity compensation for a one-link, two-degree-of-freedom link mechanism, just like the second embodiment described above.

[0079] The gravity compensation device 1 of the third embodiment can employ the following modified examples.

[0080] FIG. 7 is a perspective view of a gravity compensation device 1 according to a first modified example of the third embodiment. In the first modified example shown in FIG. 7, at least one of the multiple arms 60 is provided integrally with the multiple pulleys 40. Specifically, the first arm 60-1 is provided integrally with one of the pair of first pulleys 40-1. In other words, the first modified example does not include a first arm pulley 61-1. Note that the base 30 is provided with a shaft 30a for adjusting the fixed position of the first spring 70-1.

[0081] Figure 8 is a perspective view of a gravity compensation device 1 according to a second modified example of the third embodiment. In the second modified example shown in Figure 8, at least one of the multiple arms 60 is provided integrally with the multiple pulleys 40. Specifically, a first arm 60-1 is provided integrally with one of the pair of first pulleys 40-1, and a second arm 60-2 is provided integrally with the other of the pair of first pulleys 40-1. In other words, the second modified example does not include an arm pulley 61.

[0082] As in these modified examples, by providing at least one of the multiple arms 60 integrally with the multiple pulleys 40, it is possible to reduce the number of parts in the gravity compensation device 1 and make the entire device more compact. Note that, although the two springs 70 are fixed to the lower side (the base 30 side) in the third embodiment, the first modified example, and the second modified example, at least one of the two springs 70 may be fixed to the upper side (the link 10 side).

[0083] Fourth Embodiment Next, a fourth embodiment of the present invention will be described. In the following description, the same or equivalent components as those in the above-described embodiments will be denoted by the same reference numerals, and the description thereof will be simplified or omitted.

[0084] Fig. 9 is a perspective view of a manipulator 100 according to a fourth embodiment. Fig. 10 is a perspective view of the manipulator 100 shown in Fig. 9 as seen from the rear and bottom side. The manipulator 100 of the fourth embodiment includes a one-link, two-degree-of-freedom gravity compensation device 1 and a plurality of motors 110, 120, and 130. This manipulator 100 functions as, for example, a waist joint of a robot.

[0085] As shown in Figure 10, a motor 110 is housed in the bottom housing 101 of the manipulator 100. The motor 110 (first motor) yaws the entire gravity compensation device 1. The motor 120 (second motor) pitches the pitch joint (first pulley 40-1) of the first link 10-1. The motor 130 (third motor) pitches the roll joint (second pulley 40-2) of the first link 10-1.

[0086] In the fourth embodiment, each of the plurality of springs 70 includes a plurality of spring elements 70a, and the base 30 includes a spring element attachment / detachment mechanism 80 that can increase or decrease the number of the plurality of spring elements 70a. Below, the spring element attachment / detachment mechanism 80 of the first spring 70-1 will be described, but a similar spring element attachment / detachment mechanism 80 is also provided for the second spring 70-2.

[0087] 11 is a front view of a spring element attaching / detaching mechanism 80 according to the fourth embodiment. As shown in Fig. 11, the spring element attaching / detaching mechanism 80 includes a plurality of fixed portions 81 fixed to the base 30 and to which one ends of the plurality of spring elements 70a are detachably attached, a slide bar 82 to which the other ends of the plurality of spring elements 70a are detachably attached, and a linear guide 83 that guides the slide bar 82 in directions toward and away from the plurality of fixed portions 81. The slide bar 82 is fixed to the wire 50.

[0088] The plurality of fixing portions 81 are provided in a row along the upper edge of the base 30. One ends of the plurality of spring elements 70a can be locked to the plurality of fixing portions 81. In FIG. 11 , one ends of four spring elements 70a are locked to eight fixing portions 81. The slide bar 82 extends parallel to the plurality of fixing portions 81. Similar to the plurality of fixing portions 81 (first fixing portions), the slide bar 82 is also provided with a plurality of fixing portions 82a (second fixing portions) to which the other ends of the plurality of spring elements 70a can be locked. In other words, the number of spring elements 70a can be increased or decreased from one to eight.

[0089] Two linear guides 83 are provided in parallel. The linear guide 83 includes a guide rail 83a fixed to the base 30 and a slider block 83b that is movable along the guide rail 83a. The slide bar 82 is fixed to the slider block 83b. This allows the slide bar 82 to move toward or away from the multiple fixed parts 81 in response to the pulling of the wire 50 and the expansion and contraction of the multiple spring elements 70a. With this configuration, the spring constant k of the spring 70 can be adjusted by increasing or decreasing the spring element 70a. ｉ can be easily adjusted to satisfy the relational expressions (6) to (12).

[0090] 12 is a wiring diagram of the gravity compensator 1 according to the fourth embodiment. As shown in Fig. 12, the gravity compensator 1 according to the fourth embodiment has a mechanism (one link, two degrees of freedom) equivalent to that of the second modified example of the third embodiment (see Fig. 8) described above, but is disposed upside down so that the spring 70 is located on the upper side.

[0091] FIG. 13 is a graph showing the results of a power consumption experiment for the manipulator 100 according to the fourth embodiment. The graph in FIG. 13 shows the relationship between current [A] and the rotation angle [°] of the pitch joint. Also, "Mortor1" refers to motor 110, "Mortor2" refers to motor 120, and "Mortor3" refers to motor 130. Also, "GCM" refers to gravity compensation device 1. As shown in FIG. 13, when gravity compensation device 1 was operating, the current for all three motors 110, 120, and 130 was kept within 1.0 A, and the gravity compensation rate of the entire waist joint equipped with this gravity compensation mechanism exceeded 80%.

[0092] FIG. 14 is a graph showing the results of an accuracy evaluation experiment on the manipulator 100 according to the fourth embodiment. The graph in FIG. 14 shows the trajectories of a control group and an experimental group, in which the load and the number of spring elements 70a were varied to verify the effectiveness of the gravity compensation device 1 in improving the accuracy of the entire hip joint. As shown in FIG. 14 , as the number of spring elements 70a increased, the similarity of the trajectories to the control group gradually increased. The average Euclidean distance between the trajectories of the control group and the experimental group decreased from 3.51 cm without the gravity compensation device 1 (10 kg load, 0 spring) to 1.48 cm with the gravity compensation device 1 (10 kg load, 8 spring), a reduction rate of 57.8%. This result demonstrates that the proposed gravity compensation device 1 significantly improves the operating accuracy of the manipulator 100.

[0093] The gravity compensation device 1 can also be applied to robot systems of a different type from that of the fourth embodiment. By implementing the proposed gravity compensation device 1, the following effects can be obtained: (1) Reduction in energy consumption of the robot system. (2) Reduction in the burden on the actuators that drive the robot. (3) Improvement in the operating accuracy of the robot. (4) Improvement in the safety of the robot. (5) Improvement in the durability of the robot.

[0094] Fifth Embodiment Next, a fifth embodiment of the present invention will be described. In the following description, the same or equivalent components as those in the above-described embodiments will be denoted by the same reference numerals, and the description thereof will be simplified or omitted.

[0095] FIG. 15 is a wiring diagram of gravity compensation devices 1A to 1C according to a fifth embodiment. The gravity compensation device 1A shown in FIG. 15 is applied to, for example, the joint mechanism (link mechanism) of the trunk (the entire torso excluding the head, arms, and legs) and compensates for at least a portion of the gravity acting on the joint mechanism of the trunk. The joint mechanism of the trunk is composed of, from bottom to top, a yaw joint, a roll joint, a first pitch joint, a second pitch joint, and a third pitch joint. In this case, the rotation of all joints except the yaw joint affects the gravitational potential energy of the entire system.

[0096] Considering only the joints that require gravity compensation, the joint mechanism of the trunk is composed of a combination of two link mechanisms: a one-link, two-degree-of-freedom (pitch-roll) link mechanism (i.e., a first pitch joint and a roll joint), and a three-link, one-degree-of-freedom (pitch) link mechanism (i.e., a first pitch joint, a second pitch joint, and a third pitch joint). For this reason, the gravity compensation device 1A of the fifth embodiment is configured to combine the gravity compensation device for the one-link, two-degree-of-freedom (pitch-roll) link mechanism of the second embodiment described above with the gravity compensation device for the three-link, one-degree-of-freedom (pitch) link mechanism of the first embodiment described above, and to simultaneously compensate for gravity at these joints.

[0097] As shown in Fig. 15, this gravity compensation device 1A is composed of six sets of routes 200 routed by springs 70, wires 50, and pulleys 40. In Fig. 15, the wire routing format within region 2 is the same as that of the one-link, two-degree-of-freedom (pitch-roll) gravity compensation device (second embodiment). Specifically, the set of the first route 200-1 and the second route 200-2, the set of the third route 200-3 and the fourth route 200-4, and the set of the fifth route 200-5 and the sixth route 200-6 each constitute a one-link, two-degree-of-freedom (pitch-roll) gravity compensation device.

[0098] 15 , the wire routing format within region 3 is the same as that of the three-link, one-degree-of-freedom (pitch) gravity compensation device (first embodiment). Specifically, the set of the first route 200-1, the third route 200-3, and the fifth route 200-5, and the set of the second route 200-2, the fourth route 200-4, and the sixth route 200-6 each constitute a three-link, one-degree-of-freedom (pitch) gravity compensation device. Furthermore, the set of the first route 200-1 and the second route 200-2, the set of the third route 200-3 and the fourth route 200-4, and the set of the fifth route 200-5 and the sixth route 200-6 each have the same lengths of the fixed arm (fixed point portion 72 of the base 30) and the moment arm (connection portion 71 of the arm 60), and the same spring constant of the spring 70.

[0099] 15 is composed of six sets of springs 70, wires 50, and routes 200 of pulleys 40, and therefore has six wires 50 and 24 pulleys. To realize this gravity compensator 1A, the structure becomes very complicated and the total weight of the system increases, so it is necessary to simplify the model in a rational way.

[0100] Considering the matrix A of the wire routing in the angle relational expression of the gravity compensation device 1A shown in Fig. 15, when an element of the matrix A is 1, it means that the pulley 40 of the joint 20 at that position (hereinafter referred to as the joint pulley) has the same radius and rotation direction as the arm pulley 61 (hereinafter referred to as the spring-side pulley) of the same route 200. For example, the element a in the first row and second column of the matrix A is１２ = 1 is the S of the spring side pulley １ and the P of the joint pulley to which it is attached １ has the same radius and direction of rotation.

[0101] In other words, the spring-side pulleys can be replaced with joint pulleys having an element of 1 within the same route 200. As a result, the gravity compensator 1A can be simplified to a gravity compensator 1B in which the spring-side pulleys in all routes 200 are replaced with terminal joint pulleys. Therefore, the springs 70 are disposed at the terminal positions of the link mechanism. According to the gravity compensator 1B, there are six sets of routes 200 and six wires 50, but the number of pulleys 40 is reduced to 18.

[0102] When further simplification of gravity compensation device 1B is considered, it can be seen that the fifth route 200-5 actually includes the first route 200-1 and the third route 200-3, and the sixth route 200-6 includes the second route 200-2 and the fourth route 200-4. In other words, gravity compensation device 1B can be simplified into gravity compensation device 1C in which the first route 200-1 and the third route 200-3 are combined into the fifth route 200-5, and the second route 200-2 and the fourth route 200-4 are combined into the sixth route 200-6.

[0103] The fifth route 200-5, which is a combination of the first route 200-1 and the third route 200-3, is a P １ , P ２ , P ３ and the spring side pulley S １ , S ２ , S ３ , and the wire 50, which was originally fixed only to the end pulley, is fixed individually to each spring-side pulley, so that the spring 70 follows the spring-side pulley and changes to the corresponding position. Similarly, the sixth route 200-6, which combines the second route 200-2 and the fourth route 200-4, can also be simplified. As a result, in the gravity compensation device 1C, the number of wires 50 is reduced to two and the number of pulleys 40 is reduced to eight.

[0104] Figure 16 is a graph showing the results of an experiment to evaluate the performance of the gravity compensation device 1C according to the fifth embodiment. The specific experimental setup for Figure 16 is as follows: A 5 kg dumbbell was attached as a load to the end of the trunk link mechanism, and the rotation angle of the trunk link mechanism in the pitch direction was changed from 90° to 0°, and the rotation angle in the roll direction was changed from 25° to 0°. The performance of the gravity compensation device 1C was evaluated using the following patterns: A tension-compression testing machine (SVZ-200NB-100R3) was used as the measuring device to measure the torque applied to the trunk link mechanism.

[0105] To evaluate the performance of the gravity compensation device 1C, the maximum torque generated during operation of the trunk link mechanism was measured. The results are shown in FIG. 16 . FIG. 16( a ) shows the maximum torque at the pitch joint, and FIG. 16( b ) shows the maximum torque at the roll joint. As shown in FIG. 16( a ), the maximum torque at the pitch joint without gravity compensation was 63.75 Nm, while the maximum torque at the pitch joint with gravity compensation was 6.39 Nm. Also, as shown in FIG. 16( b ), the maximum torque at the roll joint without gravity compensation was 13.54 Nm, while the maximum torque at the roll joint with gravity compensation was 3.62 Nm. Next, the gravity compensation ratios of the pitch joint and the roll joint were calculated based on the maximum torques shown in FIGS. 16( a ) and 16 ( b ). As a result, the gravity compensation ratio of the pitch joint reached 90.0%, confirming that the effects of gravity were almost completely canceled out. Furthermore, the gravity compensation ratio of the roll joint was also able to reach 73.3%. This significantly reduced the load on the motor and improved motor efficiency.

[0106] While preferred embodiments and variations of the present invention have been described and illustrated, it should be understood that these are illustrative of the present invention and should not be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the scope of the present invention. Therefore, the present invention should not be deemed limited by the foregoing description, but rather by the scope of the claims.

[0107] For example, the gravity compensation device may be a combination of the gravity compensation device according to the first embodiment and the gravity compensation device according to the second embodiment. Furthermore, the gravity compensation device of the present invention may be incorporated into a portion of the gravity compensation device. For example, the gravity compensation device may be a combination of the gravity compensation device according to the first or second embodiment and another known gravity compensation device such as that described in Patent Document 1. Furthermore, the gravity compensation device of the present invention may be incorporated into only a portion of a link mechanism, in which case the link mechanism may include a joint that is not provided with a pulley.

[0108] The gravity compensation device described above can be applied to gravity compensation for joints of robots and humans. Examples of applications include humanoid robots, manipulators, robot arms, life support robots, and rehabilitation equipment. For example, applying the gravity compensation device to a high-load portion of a humanoid robot, such as the trunk, can reduce the load on the robot due to gravity. Furthermore, because the gravity compensation device is easily retrofitted or externally mounted, it can be easily applied to manipulators and robot arms with two or more degrees of freedom, reducing power consumption and improving operational accuracy. Applying the gravity compensation device to a life support robot allows the robot to be configured with actuators with lower output torque. This reduces the force applied to a person when the life support robot comes into contact with the person, thereby improving the safety of the life support robot relative to the person. Thus, applying the gravity compensation device described above to a robot can reliably compensate for the robot's own weight and load. The gravity compensation device described above can also be applied to a person as rehabilitation equipment. For example, if a person lacks the voluntary muscle strength of their upper limbs and is unable to move their arms on their own, they can move or rehabilitate themselves by compensating for part of the gravity acting on their shoulder or elbow joints with the gravity compensation device described above. In this way, applying the gravity compensation device described above to a person can compensate for their body weight or the weight of an object they are holding.

[0109] Furthermore, within the scope of the spirit of the present invention, it is possible to replace the components in the above-described embodiments with well-known components as appropriate, and the above-described embodiments and variations may be combined as appropriate.

[0110] DESCRIPTION OF SYMBOLS 1, 1A to 1C Gravity compensation device 10 Link 20 Joint 30 Base 30a Shaft 31 Pinch pulley 40 Pulley 50 Wire 51 First fixed point 52 Second fixed point 53 Intersection 60 Arm 61 Arm pulley 70 Spring 70a Spring element 71 Connection part 72 Fixed point part 80 Spring element attachment / detachment mechanism 81 Fixed part 82 Slide bar 82a Fixed part 83 Linear guide 83a Guide rail 83b Slider block 100 Manipulator 101 Bottom housing 110 Motor 120 Motor 130 Motor 200 Route

Claims

1. A gravity compensation device comprising: a plurality of links; a plurality of joints rotatably connecting the plurality of links; a plurality of pulleys provided at the plurality of joints; a plurality of wires fixed to the plurality of links and wound around the plurality of pulleys; a plurality of springs that expand and contract in conjunction with the pulling of the plurality of wires; and one or a plurality of bases to which the plurality of springs are fixed.

2. A gravity compensation device as described in claim 1, wherein, of the plurality of wires, the wire wound around the pulley of the nth joint (n is an integer of 2 or more) counting from the base is wound around each pulley of each of the n-1th joints counting from the base, and is pulled in conjunction with the rotation angle of each of the n-1th joints counting from the base.

3. A gravity compensation device as described in claim 2, wherein, of the plurality of wires, a wire wound around the pulley of the nth joint (n is an integer of 2 or more) counting from the base is fixed to the nth link of the plurality of links counting from the base.

4. The gravity compensation device according to claim 1, wherein, when the plurality of joints are pitch joints that are rotatable in a pitch direction and there are n pitch joints (n is an integer), there are n wires, and there are n springs.

5. The gravity compensation device according to claim 1, wherein when the plurality of joints are composed of pitch joints capable of pitch rotation and roll joints capable of roll rotation, and when n pieces of the pitch joints and n pieces of the roll joints are provided (n is an integer), the number of the plurality of wires is 2 x n, and the number of the plurality of springs is 2 x n.

6. The gravity compensation device according to claim 5, wherein the 2×n wires include parallel wires wound in parallel around the plurality of pulleys, and cross wires wound in an alternating crossing pattern around the plurality of pulleys.

7. A robot comprising a plurality of arms that rotate in conjunction with the pulling of the plurality of wires, wherein the plurality of springs comprise: connection parts that are connected to the plurality of arms and rotate; and fixed parts that do not rotate together with the connection parts; the plurality of links comprise an i-th link that is arranged i-th (i is an integer) counting from the base; the plurality of joints comprise an i-th joint that rotates the i-th link; the plurality of pulleys comprise an i-th pulley provided at the i-th joint; the plurality of wires comprise an i-th wire that is fixed to the i-th link and wound around pulleys from a first pulley that is first counting from the base to the i-th pulley; the plurality of arms comprise an i-th arm that rotates in conjunction with the pulling of the i-th wire; the plurality of springs comprise an i-th spring connected to the i-th arm; ｉ The length of the i-th link is L ｉ The length from the i-th joint to the center of gravity of the i-th link is l ｉ The distance from the rotation center of the i-th arm to the fixed point of the i-th spring is a ｉ The distance from the rotation center of the i-th arm to the connection portion of the i-th spring is b ｉ The spring constant of the i-th spring is k ｉ Then, the following relation is satisfied: The gravity compensation device according to any one of claims 1 to 6.

8. A gravity compensation device according to any one of claims 1 to 6, comprising a plurality of arms that rotate in conjunction with the pulling of the plurality of wires, the plurality of springs being connected to the plurality of arms, and at least one of the plurality of arms being integral with the plurality of pulleys.

9. A gravity compensation device according to any one of claims 1 to 6, wherein each of the plurality of springs comprises a plurality of spring elements, and the base comprises a spring element attachment / detachment mechanism that can increase or decrease the number of the plurality of spring elements.

10. The gravity compensation device according to claim 9, wherein the spring element attachment / detachment mechanism comprises: a plurality of fixed parts fixed to the base and to which one ends of the plurality of spring elements are detachably attached; a slide bar to which the other ends of the plurality of spring elements are detachably attached; and a linear guide that guides the slide bar in a direction toward and away from the plurality of fixed parts.

11. A manipulator comprising: a gravity compensation device according to any one of claims 1 to 6; and a plurality of motors that rotate the plurality of links.

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