Arm device

Abstract

This arm device comprises a link mechanism in which a plurality of links are connected by a plurality of flexible joints, and has a remote center of motion set therefor. The stiffness of the link mechanism is anisotropic due to the stiffness of at least one flexible joint among the plurality of flexible joints being different from the stiffness of the other flexible joints.

Description

Arm device

[0001] The present disclosure relates to an arm device.

[0002] An arm device is known in which a plurality of links are connected by a plurality of joints and the tip can be moved to various positions. For example, an operation of inserting an instrument mounted at the tip into a hole or the like is performed by the arm device.

[0003] At this time, when there is a deviation between the position of the hole and the position of the instrument, or when there is a deviation between the angle of the hole and the angle of the instrument, the hole and the instrument may interfere with each other and the instrument may not be smoothly inserted into the hole.

[0004] Patent Document 1 discloses an arm device that detects interference between a hole and an instrument based on a force sensor, and eliminates the interference and smoothly inserts the instrument into the hole by changing the angle of the joint or the like according to the detection result.

[0005] Japanese Unexamined Patent Application Publication No. 2020-142324

[0006] However, in the arm device disclosed in Patent Document 1, since the interference between the hole and the instrument is detected by the force sensor and then the angle of the joint is changed, a time lag occurs from when a load is applied to the instrument until the load is reduced. For example, an instantaneous load below the sampling time of the force sensor cannot be detected, or an instantaneous load exceeding the time constant of the motor cannot be handled when the operation of the instrument is motor-controlled. In addition, since it is necessary to provide a force sensor around the instrument to detect interference, the visibility in the vicinity of the instrument from the operator operating the arm device may be reduced.

[0007] Therefore, the present disclosure proposes an arm device that can reduce the time lag from when a load is applied to the instrument in a direction different from the insertion direction until the load is eliminated while ensuring visibility.

[0008] To solve the above problems, one embodiment of the arm device according to the present disclosure is an arm device in which a remote center of motion is set, comprising a link mechanism in which a plurality of links are connected by a plurality of flexible joints, wherein the rigidity of at least one of the plurality of flexible joints is different from the rigidity of the other flexible joints, thereby providing anisotropy in the rigidity of the link mechanism.

[0009] This figure schematically shows an example of the general configuration of the arm device according to the first embodiment. This is a perspective view showing an example of applying the arm device according to the first embodiment to an origami robot. This figure shows the joint portion of the link mechanism of the arm device shown in Figure 2, viewed along the X-axis. This figure schematically shows the emergency retraction mechanism of the arm device. This figure schematically shows the emergency retraction mechanism of the arm device.

[0010] The following describes the configuration for implementing this technology. The explanation will proceed in the following order: 1. Outline configuration of the arm device 2. Link mechanism 2-1. First parallel link mechanism 2-2. Second parallel link mechanism 2-3. Third parallel link mechanism 2-4. Other links and joints 3. Application of the arm device to an origami robot 4. Operation of the arm device 5. Rigidity of the link mechanism 6. Emergency retraction mechanism 7. Notes

[0011] <<1. Schematic Configuration of the Arm Device>> Figure 1 is a schematic diagram showing an example of the schematic configuration of an arm device according to the first embodiment. The arm device 1 includes a link mechanism 2 in which a plurality of links L1 to L16 are connected by a plurality of joints Q1 to Q17. The angles of the links can be made different at the joints. An instrument 3 can be attached to and detached from the link mechanism 2. In the arm device 1, the instrument 3 attached to the link mechanism 2 can be moved by changing the angle of the joints. The instrument 3 is, for example, a surgical instrument used in surgery. Examples of surgical instruments used in surgery include microneedles and endoscopes. In Figure 1, an example is shown in which a microneedle is attached as the instrument 3.

[0012] The arm device 1 is equipped with a Remote Center of Motion (RCM). For example, if the instrument 3 attached to the link mechanism 2 is a surgical instrument, the instrument 3 may be moved by the arm device 1 and inserted into the body. Since the instrument 3 passes through the Remote Center of Motion regardless of its position, even if the inserted instrument 3 is moved, the human body will not be injured at the Remote Center of Motion. For example, if the Remote Center of Motion is aligned with the instrument insertion point on the body surface, the body surface will not be injured even if the instrument 3 is moved.

[0013] <<2. Link Mechanism>> Link mechanism 2 includes a parallel link mechanism. In the parallel link mechanism, four links are connected by joints so that they form a square shape. Also, the lengths of opposing links are equal. In the parallel link mechanism, even if the shape of the parallel link mechanism is changed by changing the angle of the joints, the state in which opposing links are parallel is maintained.

[0014] In the example shown in the first embodiment, three parallel link mechanisms are included in the link mechanism 2. Specifically, the link mechanism 2 comprises a first parallel link mechanism 21, a second parallel link mechanism 22, and a third parallel link mechanism 23.

[0015] <<2-1. First Parallel Link Mechanism>> The first parallel link mechanism 21 comprises links L1 to L4 and joints Q1 to Q4. Link L1 and link L2 are connected by joint Q1. Link L1 and link L3 are connected by joint Q2. Link L2 and link L4 are connected by joint Q3. Link L3 and link L4 are connected by joint Q4. Links L1 and L4 face each other and are formed to be the same length. Links L2 and L3 face each other and are formed to be the same length.

[0016] The link mechanism 2 includes a base 24 that extends in the same direction as the link L1. The relative positional relationship between the link L1 and the base 24 is constant. The operation of each part of the link mechanism 2 originates from the link L1 and the base 24. This can also be rephrased as the link L1 and the base 24 being connected to the mechanical ground. Alternatively, it can be rephrased as the link L1 being included as part of the base 24.

[0017] Here, we define the X-axis, which extends parallel to link L1. We also define the Y-axis, which is parallel to the rotation axis of joint Q1, etc. The Y-axis extends in the depth direction in the plane of the paper in Figure 1 and is perpendicular to the X-axis. We also define the Z-axis, which is perpendicular to the X-axis and Y-axis. In the following explanation, the positive direction along the X-axis will also be referred to as forward, and the negative direction along the X-axis will also be referred to as backward. The direction along the Y-axis will also be referred to as left-right. The positive direction along the Z-axis will also be referred to as upward, and the negative direction along the Z-axis will also be referred to as downward.

[0018] <<2-2. Second Parallel Link Mechanism>> The second parallel link mechanism 22 comprises links L4 to L7 and joints Q3 to Q6. The second parallel link mechanism 22 is connected above the first parallel link mechanism 21. The second parallel link mechanism 22 shares link L4 with the first parallel link mechanism 21.

[0019] Link L4 and link L5 are connected by joint Q3. Link L4 and link L6 are connected by joint Q4. Link L5 and link L7 are connected by joint Q5. Link L6 and link L7 are connected by joint Q6. Link L4 and link L7 face each other and are formed to be the same length. Link L5 and link L6 face each other and are formed to be the same length.

[0020] <<2-3. Third Parallel Link Mechanism>> The third parallel link mechanism 23 comprises links L8 to L11 and joints Q7 to Q10. The third parallel link mechanism 23 is located in front of the second parallel link mechanism 22.

[0021] Link L8 and link L9 are connected by joint Q7. Link L8 and link L10 are connected by joint Q8. Link L9 and link L11 are connected by joint Q9. Link L10 and link L11 are connected by joint Q10. Link L8 and link L11 face each other and are formed to be the same length. Link L9 and link L10 face each other and are formed to be the same length.

[0022] The second parallel link mechanism 22 and the third parallel link mechanism 23 are connected via link 12. Specifically, link L12 is connected to link L7 of the second parallel link mechanism 22 by joint Q6. Link L12 is also connected to link L9 of the third parallel link mechanism 23 by joint Q7. Link L11 is provided with a detachable section 6 to which the device 3 can be attached and detached. In other words, the detachable section 6 is provided on a parallel link mechanism (third parallel link mechanism 23) that is different from the first parallel link mechanism 21, which includes link L1 included in part of the base 24. The device 3 is attached to the detachable section 6.

[0023] <<2-4. Other Links and Joints>> The link mechanism 2 includes links L13 and L14 connected to link L1 of the first parallel link mechanism 21 and link L7 of the second parallel link mechanism 22. More specifically, link L13 is connected to link L1 by joint Q11. Link L14 is connected to link L7 by joint Q12. Links L13 and L14 are connected by joint Q13.

[0024] The link mechanism 2 includes a first slide drive unit 24a provided on the base 24 and capable of sliding back and forth. The link mechanism 2 includes a link L15 connecting link L13 and the first slide drive unit 24a. More specifically, link L15 is connected to link L13 by joint Q14. Link 15 is connected to the first slide drive unit 24a by joint Q15.

[0025] The link mechanism 2 includes a second slide drive unit 24b provided on the base 24 and capable of sliding back and forth. The link mechanism 2 includes a link L16 connecting link L2 and the second slide drive unit 24b. More specifically, link L16 is connected to link L2 by joint Q16. Link L16 is connected to the second slide drive unit 24b by joint Q17.

[0026] The link mechanism 2 includes a linear motion link mechanism 25 that connects the third parallel link mechanism 23 and the base 24. More specifically, the linear motion link mechanism 25 is connected to the third parallel link mechanism 23 by joint Q8. The linear motion link mechanism 25 is connected to the base 24 by joint Q18. A detailed explanation of the configuration is omitted, but the linear motion link mechanism 25 deforms in conjunction with the deformation of the first parallel link mechanism 21 and the second parallel link mechanism 22, thereby making the movement path of joint Q8 linear.

[0027] <<3. Application of the Arm Device to an Origami Robot>> Figure 2 is a perspective view showing an example of applying the arm device according to the first embodiment to an origami robot. As shown in Figure 2, it is also possible to construct the arm device 1 using an origami robot.

[0028] Figure 3 is a view along the X-axis of the joint portion of the link mechanism of the arm device shown in Figure 2. In Figure 3 and the following description, links L1 to L16 may be referred to simply as links L, and joints Q1 to Q17 may be referred to simply as joints Q. Each link L comprises two opposing plate members 4 and an elastic member 5 sandwiched between the two plate members 4. The elastic members 5 of adjacent links L are integrally connected. A gap is provided between adjacent links L, and in this gap, the elastic member 5 is exposed from the plate members 4. The elastic member 5 exposed from the plate members 4 functions as joint Q.

[0029] The joint Q configured in this way functions as a flexible joint that can deform in response to load. In joint Q, it is possible to design the joints Q to have different rigidities by varying the distance between adjacent links L and the thickness of the elastic members 5.

[0030] Examples of materials for the plate member 4 include glass-reinforced fiber plastic, carbon, and metal. Examples of materials for the elastic member 5 include polyimide and polyester. Furthermore, the flexible joint is not limited to being composed of the elastic member 5, but may also be a flexible joint whose flexibility is controlled. For example, by detecting the torque applied to joint Q and deforming joint Q in the direction of the detected torque, it is possible to control the flexibility of joint Q.

[0031] <<4. Operation of the Arm Device>> Returning to Figure 1, in the arm device 1, the second parallel link mechanism 22 deforms as the first slide drive unit 24a moves. Also, the first parallel link mechanism 21 deforms as the second slide drive unit 24b moves. Due to the movement of the first slide drive unit 24a and the second slide drive unit 24b, the attachment / detachment unit 6 and the device 3 move in the direction indicated by arrow P and rotate as indicated by arrow α.

[0032] Here, by adjusting the distance D between the rotation center of joint Q6 and the rotation center of joint Q12, when the first slide drive unit 24a is moved, the attachment / detachment unit 6 and the device 3 can be moved in the direction indicated by arrow P with almost no rotational movement as indicated by arrow α.

[0033] In the link mechanism 2, two input shafts, a first slide drive unit 24a and a second slide drive unit 24b, are provided as input shafts for moving links L1 to L16. Furthermore, the movement of the attachment / detachment unit 6 and the device 3 is performed with two degrees of freedom: movement in the direction indicated by arrow P and rotational movement indicated by arrow α. In the arm device 1 according to the first embodiment, the distance D is set such that the movement of the attachment / detachment unit 6 and the device 3 is hardly performed by the movement of the first slide drive unit 24a, which is one of the two input shafts, and only movement in the direction indicated by arrow P, which is one degree of freedom, is performed. In this case, the first slide drive unit 24a becomes the insertion / removal input shaft that is moved when the device 3 is inserted or removed.

[0034] In the arm device 1, the remote center of motion (RCM) is set at the point where the base 24 is extended forward. The device 3 passes through the remote center of motion (RCM) when it moves in the direction indicated by arrow P. Also, the center of rotational motion indicated by arrow α is the remote center of motion (RCM). Therefore, as explained in "1. Outline Configuration of the Arm Device" above, even when the device 3, which is a microneedle, is inserted into the body and the device 3 is moved, the device 3 does not move at the remote center of motion (RCM). This prevents the human body from being injured by the device 3 at the remote center of motion (RCM).

[0035] <<5. Rigidity of the Link Mechanism>> When the instrument 3 attached to the link mechanism 2 is a surgical instrument inserted into the body, the rigidity of the link mechanism 2 needs to be high in the direction indicated by arrow P, which is the insertion direction. On the other hand, if the rigidity of the link mechanism 2 is high in a direction other than the insertion direction, when a load is applied to the instrument 3 inserted into the body from the human body, the instrument 3 may not move, and the human body may be injured. For this reason, it is preferable to have low rigidity in a direction other than the insertion direction, because when a load is applied, the instrument 3 will move, relieving the load and reducing the risk of injury to the human body.

[0036] In the arm device 1 according to the first embodiment, the multiple joints Q of the link mechanism 2, which is equipped with a parallel link mechanism, are flexible joints. In this case, by making the stiffness of at least one of the multiple joints Q different from the stiffness of the other joints Q, it is possible to reduce the stiffness in a direction other than the insertion direction (direction indicated by arrow P) without reducing the stiffness in the insertion direction. By providing anisotropy to the stiffness of the link mechanism 2 in this way, safety is improved when the device 3 is a surgical instrument. In addition to the multiple joints Q, multiple links L may also be flexible, or multiple links L may be flexible instead of multiple joints Q.

[0037] The rigidity at the remote rotation center (RCM) also exhibits anisotropy. This means that, for example, when inserting instrument 3 into the body, the position of the tip of instrument 3 may be shifted due to the shape and strength of the insertion site, resulting in an insertion point that is not aligned with the remote rotation center (RCM). Even in such cases, even if the relative positions of the remote rotation center (RCM) and the insertion point are misaligned, the flexibility of the arm device reduces the load applied to the insertion point, preventing overloading. On the other hand, rigidity in the P direction is maintained, so it does not affect the puncture task.

[0038] Furthermore, it is conceivable to prevent unnecessary load from being applied to the insertion point by detecting a load in a direction different from the insertion direction with a force sensor and deforming the link mechanism 2 based on the detection result. However, a time lag occurs between the detection of the load and the deformation of the link mechanism to reduce the load. For example, instantaneous loads shorter than the sampling time of the force sensor may not be detected, or if the operation of the device is motor-controlled, it may not be able to respond to instantaneous loads exceeding the motor's time constant. On the other hand, in the arm device 1 according to the first embodiment, the load applied in a direction different from the insertion direction directly becomes the force that deforms the link mechanism 2, thus reducing the time lag.

[0039] Furthermore, in a configuration where the load is reduced through control, it is necessary to install force sensors or the like around the device 3 to detect the load. This may lead to a decrease in visibility around the device 3 for the operator operating the arm device 1. On the other hand, in the arm device 1 according to the first embodiment, the load can be reduced by deforming the link mechanism 2 in response to a load in a direction different from the insertion direction without installing force sensors or the like, thus preventing a decrease in visibility.

[0040] Furthermore, there is a concern that the force sensor may malfunction due to overload if an unintended, sudden, large load is applied. Also, changes in ambient temperature can negatively affect the error in the load detection value. In addition, changes in the posture of the arm device affect the load detection value due to the weight of the arm device itself. Moreover, force sensors that can detect minute loads inherently have a small allowable load, raising concerns about their strength. On the other hand, in the arm device 1 according to the first embodiment, the load can be reduced by deforming the link mechanism 2 in response to a load in a direction different from the insertion direction, without providing a force sensor, etc., thus resolving the above-mentioned concerns.

[0041] Furthermore, linkage mechanisms equipped with parallel linkages can also be applied to exoskeleton robots. In this case, the linkage mechanism is attached to the human body so that the remote control center (RCM) aligns with the joints of the human body. If there is a misalignment between the RCM and the joints of the human body, there is a risk of malfunctions such as excessive load being placed on the joints of the human body. However, by giving the linkage mechanism anisotropic rigidity, even if the relative positions of the RCM and the joints of the human body are misaligned due to deformation of the linkage mechanism, the load will be reduced during operation due to the flexibility of the joints or links.

[0042] <<6. Emergency Evacuation Mechanism>> The arm device 1 may be equipped with an emergency evacuation mechanism that moves the device 3 in the pulling direction in an emergency. Figures 4 and 5 are schematic diagrams showing the emergency evacuation mechanism provided by the arm device.

[0043] The emergency evacuation mechanism 7 includes a biasing portion 9, a movable body 10, and an electric locking mechanism 8. The biasing portion 9 is constituted by, for example, a tension spring. One end 9a of the biasing portion 9 is fixed in the system of the emergency evacuation mechanism 7 (mechanical GND). The other end 9b of the biasing portion 9 is connected to the movable body 10. The biasing portion 9 biases the movable body 10 connected to the other end 9b in a direction approaching the one end 9a. One end 10a of the movable body 10 is connected to a first slide driving portion 24a provided in the link mechanism 2 (see also FIGS. 1 and 2). The movable body 10 is capable of reciprocating in a direction approaching the one end 9a of the biasing portion 9 and a direction once moving away from the 9a. When the movable body 10 moves in the direction approaching the one end 9a by the biasing force of the biasing portion 9, the first slide driving portion 24a moves rearward. When the first slide driving portion 24a moves rearward, the instrument 3 moves in the direction of being pulled out. Note that the biasing portion 9 is not limited to a metal spring such as a coil spring or a leaf spring, and may be, for example, a rubber spring, an air spring, a liquid spring, or the like. In addition, various elastic bodies such as diaphragms may be used for the biasing portion 9.

[0044] As an example of the electric locking mechanism 8, a solenoid as shown in FIGS. 4 and 5 is illustrated. The electric locking mechanism 8 has a fixed portion 81 and a movable portion 82. The fixed portion 81 is fixed in the system of the emergency evacuation mechanism 7 (mechanical GND). It is fixed so that the relative positional relationship with the base 24 of the link mechanism 2 does not change. The fixed portion 81 is constituted by, for example, a permanent magnet.

[0045] The movable portion 82 is provided so as to be movable between a position in contact with the fixed portion 81 and a position away from the fixed portion 81. The movable portion 82 is constituted by an electromagnet having a coil. As shown in FIG. 4, when the movable portion 82 is energized to the coil, it is attracted to the fixed portion 81 by the generated magnetic force and moves to a position in contact with the fixed portion 81. The other end 10b of the movable body 10 is connected to the movable portion 82. That is, the movable portion 82 of the electric locking mechanism 8 and the first slide driving portion 24a of the link mechanism 2 are connected via the movable body 10. When the movable portion 82 moves to a position in contact with the fixed portion 81 when the coil is energized, the first slide driving portion 24a is moved forward against the biasing force of the biasing portion 9.

[0046] On the other hand, when the energization of the coil of the movable part 82 is cut off, the magnetic force disappears, and as shown in FIG. 5, the movable part 82 moves to a position away from the fixed part 81 by the biasing force of the biasing part 9. At this time, the first slide driving part 24a also moves backward by the biasing force of the biasing part 9. When the first slide driving part 24a moves backward, the instrument 3 moves in the direction of being pulled out.

[0047] Since the emergency evacuation mechanism 7 is provided in the arm device 1, when it is necessary to urgently pull out the instrument 3, by cutting off the energization of the coil of the electric locking mechanism 8, the first slide driving part 24a can be moved backward, and the instrument 3 can be immediately pulled out. For example, it can be configured such that the energization of the coil is cut off by pressing a button for operation during emergency evacuation (not shown). Also, when the power supply is cut off due to a power failure, the energization of the coil is cut off, so the instrument 3 is immediately pulled out.

[0048] Therefore, when the instrument 3 is a surgical instrument to be inserted into the body, the safety of the surgery can be improved. Also, since the emergency evacuation mechanism 7 can be arranged near the base 24 away from the instrument 3, it is possible to prevent the visibility around the instrument 3 from being reduced by the emergency evacuation mechanism 7. Also, since there is no need to provide an extra heavy object for emergency evacuation around the instrument 3, the operation speed of the instrument 3 can be increased. Note that the electric locking mechanism 8 is not limited to a solenoid. For example, a linear actuator or an electromagnetic brake is exemplified for the electric locking mechanism 8.

[0049] <<7. Addendum>> The technology can also be configured as follows: (1) An arm device having a link mechanism in which a plurality of links are connected by a plurality of flexible joints, wherein the rigidity of at least one of the plurality of flexible joints is different from that of the other flexible joints, thereby providing anisotropy in the rigidity of the link mechanism. (2) The arm device according to (1), wherein the link mechanism includes a plurality of parallel link mechanisms. (3) The arm device according to (1) or (2), wherein each of the links has two opposing plate members and an elastic member sandwiched between the plate members, the elastic members of adjacent links are integrally connected to each other, and the elastic members between adjacent links that are not sandwiched between the plate members function as the flexible joint. (4) The arm device according to (2), further comprising a detachable part on which an instrument can be attached and detached, having a plurality of input shafts for moving the links included in the parallel link mechanism, the detachable part moves with a plurality of degrees of freedom in response to input to the plurality of input shafts, the detachable part moves with a single degree of freedom upon input to one of the plurality of input shafts, which is an insertion / removal input shaft, and the direction of movement of the detachable part due to input to the insertion / removal input shaft is in a direction that causes the distance between the instrument attached to the detachable part and the remote center of motion to be different. (5) The arm device according to (4), further comprising a biasing part that biases the insertion / removal input shaft in a direction away from the remote center of motion, and an electrical locking mechanism that biases the insertion / removal input shaft in a direction toward the remote center of motion against the biasing force from the biasing part, the biasing force by the electrical locking mechanism is exerted when the electrical locking mechanism is energized. (6) The arm device according to any one of (1) to (5) above, wherein the instrument is a surgical instrument whose tip is inserted into the body. (7) The arm device according to (6) above, wherein the rigidity of the link mechanism is lower in a direction other than the insertion direction of the instrument than the rigidity in the insertion direction of the instrument at the remote center of motion.

[0050] 1 Arm device 2 Link mechanism 21 First parallel link mechanism 22 Second parallel link mechanism 23 Third parallel link mechanism 24 Base 24a First slide drive unit 24b Second slide drive unit 25 Linear link mechanism 3 Fixture 4 Plate member 5 Elastic member 6 Detachable part 7 Emergency retraction mechanism 8 Electrical lock mechanism 81 Fixed part 82 Movable part 9 Biasing part 9a One end 9b Other end 10 Movable body 10a One end 10b Other end

Claims

1. An arm device having a link mechanism in which multiple links are connected by multiple flexible joints, wherein the rigidity of at least one of the multiple flexible joints differs from that of the other flexible joints, thereby providing anisotropy in the rigidity of the link mechanism.

2. The arm device according to claim 1, wherein the link mechanism includes a plurality of parallel link mechanisms.

3. The arm device according to claim 1, wherein each of the links has two opposing plate members and an elastic member sandwiched between the plate members, the elastic members of adjacent links are integrally connected to each other, and the elastic members between adjacent links that are not sandwiched between the plate members function as the flexible joint.

4. The arm device according to claim 2, further comprising a detachable part on which the device is detachable, having a plurality of input shafts for moving the link included in the parallel link mechanism, the detachable part moves with a plurality of degrees of freedom in response to input to the plurality of input shafts, the detachable part moves with a single degree of freedom in response to input to one of the plurality of input shafts, which is an insertion / removal input shaft, and the direction of movement of the detachable part due to input to the insertion / removal input shaft is in a direction that causes the distance between the device attached to the detachable part and the remote motion center to differ.

5. The arm device according to claim 4, further comprising: a biasing unit that biases the device away from the remote center of motion with respect to the insertion / removal input shaft; and an electrical locking mechanism that biases the device towards the remote center of motion against the biasing force from the biasing unit, wherein the biasing force from the electrical locking mechanism is exerted when the electrical locking mechanism is energized.

6. The arm device according to claim 5, wherein the instrument is a surgical instrument whose tip is inserted into the body.

7. The arm device according to claim 6, wherein the rigidity of the link mechanism is lower in a direction other than the insertion direction of the device than the rigidity in the insertion direction of the device at the remote motion center.

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