Joint structure of the robot

Abstract

A joint structure that connects a first component and a second component of a robot has a Stewart platform capable of controlling the relative position and / or angle of the second component with respect to the first component. The Stewart platform has: a first member joined to the first component; a second member joined to the second component; a plurality of legs connecting the first member and the second member; a drive mechanism that changes the effective length of each leg in order to change the relative position and / or angle of the second member with respect to the first member; and a flexible mechanism that elastically changes the effective length of the legs when an external force acts on the second member and restores the effective length of the legs when the external force is removed.

Description

Technical Field

[0001] The present invention relates to a joint structure of a robot, and particularly to a joint structure preferably for a manipulator of a soft robot (flexible robot). Background Art

[0002] Industrial robots usually consist of a manipulator made of a highly rigid mechanism, and while measuring the state through sensors, they control the three-dimensional position of the end effector. However, a robot composed only of a highly rigid mechanism is, for example, difficult to perform actions such as actions following contact with an object and actions requiring higher precision than the measurement error of sensors. As a method for solving such technical problems, a method of a so-called soft robot (flexible robot) has been proposed. For example, a flexible mechanism that is displaced or deformed by an external force is provided in a part of the robot to automatically follow the shape of an object, etc. The flexible mechanisms described in Patent Documents 1 and 2 are also an example of this.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Laid-Open No. 5-192892

[0006] Patent Document 2: Japanese Patent Laid-Open No. 8-118281 Summary of the Invention

[0007] Technical Problem to be Solved by the Invention

[0008] However, the conventional flexible mechanisms as proposed in Patent Documents 1 and 2 have a very small movable range and can only perform limited activities (to the extent of being able to perform minute displacements in a horizontal plane), and thus the applicable scenarios and uses are limited.

[0009] The present invention has been completed in view of the above actual situation, and an object thereof is to provide a joint structure of a robot that can perform active multi-degree-of-freedom control and also has flexibility.

[0010] Solution for Solving the Technical Problem

[0011] The present disclosure includes a joint structure that connects a first component and a second component of a robotic manipulator. The joint structure is characterized by having a Stewart platform capable of controlling the relative position and / or angle of the second component with respect to the first component. The Stewart platform includes: a first member joined to the first component; a second member joined to the second component; a plurality of legs connecting the first member and the second member; a drive mechanism that changes the effective length of each leg to change the relative position and / or angle of the second member with respect to the first member; and a flexible mechanism that elastically changes the effective length of the legs when an external force acts on the second member and restores the effective length of the legs when the external force is removed.

[0012] Here, the first component may be a link between joints of the manipulator, and the second component may be a link closer to the end effector side than the first component or the end effector. According to this structure, by changing the effective length of each leg of the Stewart platform through the drive mechanism, active multi-degree-of-freedom control of the relative position and / or angle between the first component and the second component can be achieved. In addition, when an external force acts on the robot, the effective length of the legs elastically changes, and the relative position and / or angle between the first component and the second component changes passively following the external force. Therefore, active multi-degree-of-freedom control and flexibility can be achieved simultaneously.

[0013] The "effective length of the leg" can be considered as the distance from the connection point of the first member and the leg to the connection point of the second member and the leg. The same can be considered in the case where the leg is a structure formed by connecting multiple rods or is composed of a bent member.

[0014] Alternatively, the leg may have a rod that is supported by a support body so as to be slidable, and the effective length of the leg is changed by sliding. The drive mechanism includes: a linear member installed on the rod and having flexibility; and an elastic member that elastically deforms when the linear member is stretched to slide the rod, generating an elastic restoring force against the tensile force of the linear member. According to this structure, when a tensile force is applied to the linear member, the rod slides and the elastic member gradually elastically deforms. Then, at the position where the tensile force and the elastic restoring force are balanced, the sliding of the rod stops. According to such a structure, by adjusting the tensile force of the linear member, the sliding state of the rod can be simply and accurately controlled. The effective length of one leg may be determined only by the sliding state of the rod of that leg or by comprehensively considering the sliding states of the rods of all legs depending on the specific structure of the Stewart platform. In any case, the effective length of each leg can be accurately controlled by accurately controlling the sliding state of each rod.

[0015] In this structure, the elastic member can also serve as the flexible mechanism. For example, when an external force is applied in the same direction as the tensile force of the linear member, the resultant force of the tensile force and the external force causes the elastic member to deform further, the sliding state of the rod changes, and thus the effective length of the foot changes. Then, when the external force disappears, the sliding state of the rod returns to the position balanced with the tensile force. In this way, by using the same member to form the drive mechanism and the flexible mechanism, the number of components can be reduced, and thus cost reduction and miniaturization of the device can be achieved.

[0016] It is also possible that the elastic member includes a non-linear spring member, and the deformation amount of the elastic member is changed by the tensile amount of the linear member, and the rigidity of the flexible mechanism is variable. Thus, the hardness (flexibility) of the joint structure can also be controlled.

[0017] The support can also be a bearing provided on the first member. This configuration has the advantage of being able to simplify the structure of the foot itself.

[0018] The support can also be a cylinder member provided on the foot and into which the rod is slidably inserted. This configuration has the advantage of being able to simplify the structures of the first member and the second member.

[0019] It is also possible that the end of the linear member is pulled out to the outside of the joint structure and connected to a drive source provided separately from the joint structure. In this way, by making the drive source of the linear member separate from the joint structure and arranging it outside the joint structure, the joint structure itself can be made compact and lightweight.

[0020] It is also possible that the foot has a rod whose effective length changes by moving in the length direction, and the drive mechanism is an actuator that moves the rod in its length direction by a compressible fluid. According to such a structure, by controlling the supply / discharge of the compressible fluid, the movement amount of the rod can be simply and accurately controlled.

[0021] The compressible fluid of the actuator can also serve as the flexible mechanism. For example, when an external force is applied in the direction of pressing the rod, the compressible fluid inside the actuator is elastically compressed or elastically expanded, and the movement amount of the rod changes. Then, when the external force disappears, the compressed or expanded compressible fluid returns to its original state, and the movement amount of the rod returns to its original state. In this way, by using the same member to form the drive mechanism and the flexible mechanism, the number of components can be reduced, and thus cost reduction and miniaturization of the device can be achieved.

[0022] The actuator can also be a cylinder.

[0023] Alternatively, the tube for supplying / discharging the compressible fluid to / from the actuator may be pulled out to the outside of the joint structure and connected to a drive source provided separately from the joint structure. In this way, by separating the drive source of the actuator from the joint structure and disposing it outside the joint structure, the joint structure itself can be made compact and lightweight.

[0024] Alternatively, it may further include a locking mechanism that switches between a free state and a locked state. The free state is a state in which the second component is independent of the first component and is freely movable, and the locked state is a state in which the second component is fixed to the first component. In the locked state, the first component and the second component operate as a single rigid body. Thus, since it is possible to switch between a highly rigid robot (locked state) and a flexible robot (free state), for example, by appropriately differentiating the use in combination with the actions and scenarios of the robot, an expansion of the application range of the robot and effective actions can be expected.

[0025] The present invention can be regarded as a joint structure of a robot having at least a part of the above configuration, or can be regarded as an actuator that controls the position / angle of a component of a robot's manipulator. In addition, it can also be regarded as a manipulator or a robot of a robot having such a joint structure or actuator. Further, the present invention can also be regarded as a control method or a drive method for controlling the position / angle of a component of a robot's manipulator by the joint structure of the above configuration. In addition, each of the above configurations can be combined with each other as much as possible to form the present invention.

[0026] Advantages of the Invention

[0027] According to the present invention, it is possible to provide a joint structure of a robot that can perform active multi-degree-of-freedom control and also has flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A and Figure 1 B are schematic views of a joint structure having a Stewart platform.

[0029] Figure 2 are diagrams showing the movement when an external force acts.

[0030] Figure 3 are schematic views showing the overall configuration of the robot.

[0031] Figure 4 is a perspective view of the joint structure.

[0032] Figure 5 A is a side view (in-situ) of the joint structure, Figure 5 B is a side view (z translation) of the joint structure, Figure 5C is a side view (x translation) of the joint structure. Figure 5 D is a side view (rotation) of the joint structure.

[0033] Figure 6 is a diagram showing the characteristics of the non-linear spring used in Modification 1.

[0034] Figure 7 is a diagram showing Modification 2.

[0035] Figure 8 is a diagram showing Modification 3.

[0036] Figure 9 is a diagram showing Modification 4. Detailed Description

[0037] <Application Example>

[0038] Refer to Figure 1 A and Figure 1 B to describe one application example of the present invention. Figure 1 A and Figure 1 B are schematic diagrams of the joint structure of a robot having a Stewart platform. Figure 1 A is Figure 1 a sectional view taken along the line A-A of B, Figure 1 B is a side view (viewed from the arrow B of Figure 1 A).

[0039] The joint structure 1 is a device that connects between the first member 11 and the second member 12 of the robot arm RM that constitutes the robot. The robot arm RM is a multi-joint robot arm. The first member 11 is a member located on the proximal side of the robot arm RM, and the second member 12 is a member located on the more distal side than the first member 11.

[0040] The joint structure 1 has a Stewart platform 10 that can control the relative position and / or angle of the second member 12 with respect to the first member 11. The Stewart platform has a structure in which a plurality of legs support one member, and is a mechanism that imparts six degrees of freedom of motion in the x direction, y direction, and z direction and rotation about the x axis, y axis, and z axis to the member by changing the effective length of each leg (by changing the combination of the effective lengths of each leg). The Stewart platform is also referred to as a motion base, a six-axis platform, or a six-degree-of-freedom platform.

[0041] The Stewart platform 10 generally includes: a first member 110, joined to the first member 11; a second member 120, joined to the second member 12; a plurality of legs 130, connecting the first member 110 and the second member 120; and a drive mechanism 140, changing the effective length of each leg 130. The number of legs 130 is typically six, but a configuration other than six may also be employed.

[0042] In Figure 1 In the example of B, each leg 130 has a structure formed by bendably connecting two rods 131 and 132. The rod 131 is supported by a bearing 111 of the first member 110, and the rod 132 is connected to the second member 120 via a universal joint 121.

[0043] A flexible linear member 150 is mounted on the upper end of the rod 131. The linear member 150 is pulled out to the outside of the joint structure 1 and connected to a drive source M. In addition, an elastic member 160 is provided concentrically with the rod 131. In Figure 1 this configuration example, a drive mechanism 140 of the leg 130 is constituted by the linear member 150 and the elastic member 160.

[0044] The operation of the drive mechanism 140 will be described. When a tensile force F1 is applied to the linear member 150 by the drive source M, the rod 131 slides upward in the direction of Figure 1 B, and the elastic member 160 is gradually elastically deformed (compressed). Then, at the position where the tensile force F1 and the elastic restoring force F2 of the elastic member 160 are balanced, the sliding of the rod 131 stops, and the effective length of the leg 130 becomes stable. According to this structure, the effective length of the leg 130 can be simply and accurately controlled by adjusting the tensile force applied to the linear member 150 from the drive source M. When the robot is operating, the controller (not shown) controls the drive source M to individually adjust the effective length of each leg 130, so that the attitude (position / angle) of the second member 120 can be arbitrarily controlled. In Figure 1 the example of B, since the tensile force F1 applied to the left leg 130 is greater than the tensile force F1 applied to the right leg 130, the left leg 130 is shorter than the right leg 130, and the second member 120 rotates about the y-axis.

[0045] The elastic member 160 also functions as a "soft mechanism" that elastically changes the effective length of the leg 130 when an external force is applied to the second member 120 (second part 12), and restores the effective length of the leg 130 when the external force is removed. For example, as shown on the right side of Figure 2 , it is assumed that a force F3 is applied in the direction of pushing up the right leg 130 by applying an external force to the second member 120. In this case, the elastic member 160 is further compressed by the resultant force of the tensile force F1 and the external force F3, and the effective length of the right leg 130 becomes shorter. As a result, the relative position and / or angle of the first part 11 and the second part 12 change passively following the external force. Then, when the external force F3 disappears, as shown on the left side of Figure 2 , the effective length of the leg 130 returns to the position balanced with the tensile force F1.

[0046] The drive source M can be a linear motor or a rotary motor. The drive source M can be driven electrically or by fluid pressure. The drive source M can also drive the linear member 150 in a manner that determines the retraction length of the linear member 150 instead of applying a tensile force F1 to the linear member 150. In this case, the rod 131 is stationary at a position corresponding to the retraction length of the linear member 150, and is applied with an elastic restoring force F2 by the elastic member 160. When an external force exceeding the elastic restoring force F2 at this time is applied to the rod 131 and the elastic member 160 is compressed, the rod 131 moves until the elastic restoring force F2 that increases as the elastic member 160 is compressed balances with the external force. In the drive source M, a deflection corresponding to the movement of the rod 131 occurs in the linear member 150 that has been positioned in the longitudinal direction. This deflection mainly occurs in a portion of the linear member 150 that does not pass through the tube described later.

[0047] According to the joint structure 1 described above, active multi-degree-of-freedom control and flexibility can be achieved simultaneously.

[0048] <Embodiment>

[0049] Refer to Figure 3 The robot and its joint structure according to the embodiment of the present invention will be described. Figure 3 It is a schematic diagram showing the overall configuration of the robot.

[0050] In the present embodiment, an example is shown in which the end effector E2 is attached to the manipulator RM of the vertical multi-joint robot R via the above-described joint structure 1 having the Stewart platform. However, this is merely an example, and the configuration / types of the robot R are not limited to Figure 3 this example. Specifically, the robot R can be any robot as long as it is a robot having at least one or more manipulators, and can be applied to various types of robots such as industrial robots, humanoid robots, nursing robots, transfer robots, household robots, and surgical assistance robots. Among them, the industrial robot is one of the robots to which the joint structure 1 can be preferably applied. In addition to the vertical multi-joint robot, the industrial robot also includes a horizontal multi-joint robot (SCARA Robot), a parallel link robot, an orthogonal robot, etc. In addition, the application position of the joint structure 1 is not limited to the connection part of the end effector E2, and can also be applied to the connection part between the links.

[0051] The robot R of the present embodiment mainly includes a manipulator RM, a controller RC, and a drive source M. The manipulator RM has a plurality of links and joints (joints) that connect the links to each other, and is a multi-joint manipulator driven by a servo motor. The controller RC is a control device that controls the servo motor of the manipulator RM and the drive source M.

[0052] The link E1 at the front end of the robotic arm RM is connected to the end effector E2 via the joint structure 1. In this example, the link E1 corresponds to Figure 1 the first component 11 of B, and the end effector E2 corresponds to Figure 1 the second component 12 of B. The drive source M is a device for driving the drive mechanism 140 of the Stewart platform for driving the joint structure 1. The drive source M can be of any type / structure as long as it can perform the actions of stretching the linear member 150 and feeding it out, but it needs to have a tensile force that can change the effective length of the leg 130 against the elastic restoring force of the elastic member 160, and a stroke that can fully ensure the movable range of the Stewart platform and the end effector E2. For example, a motor, a hydraulic actuator, a pneumatic actuator, etc. can also be used as the drive source M. In addition, an independent drive source M can be provided for each leg 130.

[0053] In Figure 4 and Figure 5 A~ Figure 5 D shows the details of the joint structure 1. Figure 4 is a perspective view of the joint structure 1, Figure 5 A is a side view (in-situ) of the joint structure 1, Figure 5 B is a side view (z translation) of the joint structure 1, Figure 5 C is a side view (x translation) of the joint structure 1, Figure 5 D is a side view (rotation) of the joint structure 1. In the following description, the xyz coordinate system of the joint structure 1 is formed such that the normal line of the first member 110 (i.e., the axial direction of the link E1) becomes the z-axis.

[0054] This joint structure 1 can actively control the six-degree-of-freedom movement (translation in the x, y, and z directions and rotation about the x, y, and z axes) of the end effector E2 using the Stewart platform 10.

[0055] The Stewart platform 10 has a structure in which a substantially disk-shaped first member 110 and a substantially disk-shaped second member 120 are connected by six legs 130. The structures of the six legs 130 are common. Each leg 130 is composed of two rods 131 and 132, and the rods 131 and 132 are bendably connected by a pin joint 133. The proximal rod 131 is supported by a sliding bearing 111 in a through-hole provided in the first member 110 such that sliding in the z direction and rotation about the z axis are free. On the other hand, the distal rod 132 is connected to the second member 120 via a universal joint 121 and is rotatable in any direction with respect to the second member 120. In addition, a ball joint can also be used for the connection between the rod 132 and the second member 120.

[0056] A flexible linear member 150 is attached to the end on the proximal end side of the rod 131. In the present embodiment, a metal wire is used as the linear member 150. However, as the linear member 150, a cable (rope) made of chemical fiber or natural fiber may also be used. The linear member 150 is pulled out to the outside of the joint structure 1 and connected to the drive source M. The linear member 150 in the path between the joint structure 1 and the drive source M, at least the part that becomes curved, passes through a non-elastic tube (not shown) whose both ends are fixed. In a state where tension is applied to the linear member 150, according to the displacement of the linear member 150 in the drive source M, the linear member 150 in the joint structure 1 is displaced.

[0057] In addition, an elastic member 160 is provided concentrically with the rod 131 between the flange 134 formed at the lower end of the rod 131 (the end on the side of the pin joint 133) and the first member 110. In the present embodiment, a helical spring (compression spring) is used as the elastic member 160.

[0058] The controller RC calculates the effective lengths that the six legs 130 should take and the control amounts (tensile force, tensile amount, etc.) corresponding to the effective lengths according to the target attitude of the second member 120 (relative position and angle with respect to the first member 110). Then, when the controller RC controls the drive source M to individually adjust the effective lengths of the six legs 130, the second member 120 takes the target attitude (position / angle).

[0059] Here, the effective lengths of the six legs 130 are set as LL1 to LL6, the maximum effective length is denoted as LLmax, and the minimum effective length is denoted as LLmin. In Figure 5 A, it is a state where LL1 = LL2 = LL3 = LL4 = LL5 = LL6 = LLmax, that is, a state where all six legs 130 are set to the maximum effective length LLmax. In this case, the displacement of the second member 120 in the xy plane is 0 [mm] (that is, the xy coordinates of the center of the second member 120 are (0, 0)), and the rotation of the second member 120 is 0 [deg]. This is the standard state (in-situ). As Figure 5 shown in B, when the linear members 150 of the six legs 130 are stretched by the same amount while maintaining the state of LL1 = LL2 = LL3 = LL4 = LL5 = LL6, the second member 120 translates in the z direction while maintaining parallelism with the xy plane. In addition, when the effective lengths of LL1 to LL6 are individually adjusted, it is also possible to make the second member 120 translate in the x direction or the y direction as shown in Figure 5 C, or rotate the second member 120 as shown in Figure 5 D. It is also possible to combine Figure 5 A to Figure 5The states of D are combined, whereby active six-degree-of-freedom control can be achieved.

[0060] In addition to the above-described active control, the joint structure 1 of the present embodiment can also perform passive activities following an external force. For example, Figure 5 In the state of A, it is assumed that a force in the z direction (the upward direction in the figure) acts on the second member 120. In this case, while maintaining the state where LL1 = LL2 = LL3 = LL4 = LL5 = LL6, the six legs 130 are lifted, and the second member 120 can be displaced in the z direction as in Figure 5 the state of B. Or, Figure 5 In the state of B, when a force in the x direction (the leftward direction in the figure) acts on the second member 120, the effective lengths of the respective legs 130 change following this force, and the second member 120 can be displaced in the x direction as in Figure 5 the state of C. Or, Figure 5 In the state of B, when a torque acts on the second member 120, the second member 120 can rotate as in Figure 5 the state of D. Then, when the external force is removed, the effective lengths of the respective legs 130 are restored to their original states by the restoring force of the elastic member 160, and the attitude (position / angle) of the second member 120 is also restored to its original state ("the original state" is the effective length or attitude determined by the active control of the drive mechanism 140). Through such a flexible mechanism, the end effector E2 can move freely independent of the link E1, and a so-called "flexible robot" can be realized.

[0061] In the joint structure 1 of the present embodiment, when all the linear members 150 are stretched upward with a force sufficiently larger than the elastic restoring force of the elastic member 160, the elastic member 160 completely fails, and the position of the rod 131 is fixed. At this time, LL1 = LL2 = LL3 = LL4 = LL5 = LL6 = LLmin, that is, all six legs 130 become the minimum effective length LLmin. In this state, even if an external force acts on the second member 120, the second member 120 is not easily movable. That is, the above-described flexible mechanism is invalidated, and the link E1 and the end effector E2 work as a single rigid body. Through such a locking mechanism, it is possible to switch between a free state where the end effector E2 is freely movable independent of the link E1 and a locked state where the end effector E2 is fixed to the link E1.

[0062] According to this structure, by changing the effective lengths of the legs 130 of the Stewart platform 10 through the drive mechanism 140, active multi-degree-of-freedom control of the relative position / angle between the link E1 (the first component) and the end effector E2 (the second component) can be achieved. In addition, when an external force acts on the robot R, the effective lengths of the legs 130 change elastically, and the relative position and / or angle between the link E1 and the end effector E2 change passively following the external force. Therefore, active multi-degree-of-freedom control and flexibility can be achieved simultaneously.

[0063] In addition, according to the drive mechanism 140 of the present embodiment, at the position where the tensile force of the linear member 150 and the elastic restoring force of the elastic member 160 are balanced, the sliding of the rod 131 stops, and the effective length of the leg 130 is stabilized. According to such a structure, by adjusting the tensile force of the linear member 150, the effective length of the leg 130 can be simply and accurately controlled.

[0064] In addition, in the present embodiment, since the drive source M of the linear member 150 is not integrated with the joint structure 1 and is arranged outside the joint structure 1, the joint structure 1 itself can be made compact and lightweight.

[0065] In addition, since the joint structure 1 of the present embodiment has a locking mechanism, a robot with high rigidity (locked state) and a flexible robot (free state) can be switched. For example, by appropriately distinguishing and using them in combination with the actions and scenarios of the robot, an expansion of the application range of the robot and effective actions can be expected.

[0066] In addition, in the joint structure 1 of the present embodiment, the drive mechanism 140, the flexible mechanism, and the locking mechanism are constituted by the same components. Thereby, a reduction in the number of components can be achieved, and further cost reduction and miniaturization of the device can be realized.

[0067] <Modification Example>

[0068] The above-described embodiment is merely an illustrative example of the configuration example of the present invention. The present invention is not limited to the above specific embodiments, and various modifications can be made within the scope of its technical idea.

[0069] In Modification Example 1, a non-linear spring member is used as the elastic member 160. Figure 6 It is a graph showing the difference in characteristics between a linear spring and a non-linear spring. The horizontal axis shows displacement (flexure), and the vertical axis shows load. The load of the linear spring is in a proportional relationship with the displacement, and the rigidity (spring constant) is constant regardless of the displacement. In contrast, the non-linear spring exhibits the characteristic that the rigidity (spring constant) increases as the displacement increases. Such non-linear characteristics can be achieved, for example, by making the coil diameter of the helical spring uneven, making the pitch of the helical spring unevenly spaced, making the wire diameter of the helical spring uneven, and other methods.

[0070] For example, by controlling the drive source M, the elongation amounts of the linear member 150 in the free state, such as s1 [mm], s2 [mm], s3 [mm] (s1 < s2 < s3), can be switched in multiple stages, thereby changing the displacement of the elastic member 160. Thereby, the hardness (flexibility) of the joint structure 1 in the free state can be controlled. For example, by adjusting according to the movement and situation of the robot to achieve an appropriate hardness (flexibility), it is expected to expand the application range of the robot and enable effective movement.

[0071] In Figure 7 a modification example 2 is shown. The configurations of the legs, drive mechanisms, and softening mechanisms in modification example 2 are different from those in the above-described embodiment. As Figure 7 shown, each leg 130 includes a rod 50, a cylinder member 51 into which the rod 50 is slidably inserted, a piston 52 provided at an end of the rod 50, and an elastic member 53 disposed in a space formed by the piston 52 and the cylinder member 51. The legs 130 are respectively connected to the first member 110 and the second member 120 through a universal joint or a ball joint. The linear member 150 for driving the rod 50 is mounted on the piston 52 and is pulled out to the outside of the joint structure 1 through the inside of the cylinder member 51 and the through hole of the first member 110.

[0072] In this configuration, when a tensile force is applied to the linear member 150 by the drive source M, the rod 50 is pulled back into the cylinder member 51, and the elastic member 53 gradually undergoes elastic deformation (compressive deformation). Then, at the position where the tensile force and the elastic restoring force of the elastic member 53 are balanced, the sliding of the rod 50 stops, and the effective length of the leg 130 becomes stable. According to this structure, the effective length of the leg 130 can also be simply and accurately controlled by adjusting the tensile force applied to the linear member 150 from the drive source M. In this configuration, the drive source M may drive the linear member 150 in such a manner as to determine the retraction length of the linear member 150.

[0073] In addition, the elastic member 53 also functions as a softening mechanism. For example, when an external force acts in the same direction as the tensile force of the linear member 150, the elastic member 53 is further compressed and deformed by the resultant force of the tensile force and the external force, and the effective length of the leg 130 changes. Then, when the external force disappears, the effective length of the leg 130 returns to the position where it is balanced with the tensile force or the position corresponding to the determined retraction length of the linear member 150.

[0074] In Figure 8 a modification example 3 is shown. The configurations of the legs, drive mechanisms, and softening mechanisms in modification example 3 are different from those in the above-described embodiment. As Figure 8As shown, each leg 130 is composed of a rod 60 and a pneumatic actuator (also known as a cylinder) 61 that moves the rod 60 in the effective length direction of the leg 130. The leg 130 is connected to the first member 110 and the second member 120 respectively through universal joints.

[0075] Two tubes 62 for supplying / discharging a compressible fluid (such as air) to / from the pneumatic actuator 61 are provided in the pneumatic actuator 61. These tubes 62 can also be pulled out to the outside of the joint structure 1 and connected to a drive source M provided separately from the joint structure 1. In this way, by making the drive source M of the actuator separate from the joint structure 1 and arranging it outside the joint structure 1, the joint structure 1 itself can be made compact and lightweight.

[0076] In this configuration, when a fluid is introduced into the first chamber 611 of the pneumatic actuator 61 through the drive source M (such as a compressor, a pump, etc.), the differential pressure between the first chamber 611 and the second chamber 612 causes the rod 60 to move toward the second chamber 612 side. Conversely, when the fluid is introduced into the second chamber 612, the rod 60 can be moved toward the first chamber 611 side. Thus, the effective length of the leg 130 can be controlled simply and with good accuracy.

[0077] In this configuration, the compressible fluid inside the pneumatic actuator 61 also functions as a soft mechanism. For example, when an external force acts in the direction of pressing in the rod 60, the compressible fluid inside the pneumatic actuator 61 is elastically compressed or elastically expanded, and the effective length of the leg 130 changes. Then, when the external force disappears, the compressed or expanded compressible fluid returns to its original state, and the effective length of the leg 130 returns to its original state.

[0078] In Figure 9 Deformation example 4 is shown. Deformation example 4 is a deformation example of the locking mechanism. The locking mechanism is generally composed of a first locking piece 70 provided on the first member 110 and a second locking piece 71 provided on the second member 120. It has the following structure: The fixation between the first member 110 and the second member 120 is achieved by shortening the effective length of the leg 130 and engaging the first locking piece 70 with the second locking piece 71.

[0079] Here, it can also be configured as follows: A convex portion is provided on one of the first locking piece 70 and the second locking piece 71, and a concave portion is provided on the other, and the convex portion and the concave portion are engaged. Through such an engaging method, the fixing force in the locked state can be improved. In addition, the relative positioning between the first member 110 and the second member 120 in the locked state can also be achieved. In Figure 9 the example, a hemispherical convex portion and a conical concave portion are provided. According to this structure, since the convex portion and the concave portion can contact at any angle, the second member 120 can be locked in a posture inclined with respect to the first member 110.

[0080] <Supplementary Note 1>

[0081] (1) A joint structure, characterized in that it connects between a first component (11) and a second component (12) of a robot, and the joint structure has a Stewart platform (10), which can control the relative position and / or angle of the second component (12) with respect to the first component (11). The Stewart platform (10) has: a first member (110), joined to the first component (11); a second member (120), joined to the second component (12); a plurality of legs (130), connecting the first member (110) and the second member (120); a drive mechanism (140), for changing the relative position and / or angle of the second member (120) with respect to the first member (110) by changing the effective length of each leg (130); and a flexible mechanism (160), which elastically changes the effective length of the legs (130) when an external force acts on the second member (120), and restores the effective length of the legs (130) when the external force is removed.

[0082] Explanation of Reference Numerals

[0083] 1: Joint structure; 10: Stewart platform; 11: First component; 12: Second component; 50: Rod; 51: Cylinder member; 52: Piston; 53: Elastic member; 60: Rod; 61: Pneumatic actuator; 62: Pipe; 70: First locking piece; 71: Second locking piece; 110: First member; 111: Bearing; 120: Second member; 121: Universal joint; 130: Leg; 131: Rod; 132: Rod; 133: Pin joint; 134: Flange; 140: Drive mechanism; 150: Linear member; 160: Elastic member; E1: Link; E2: End effector; R: Robot; RM: Manipulator; RC: Controller; M: Drive source.

Claims

1. A joint structure, characterized in that, Connect the first component and the second component of the robot's manipulator. The joint structure has a Stewart platform, and the Stewart platform can control the relative position and / or angle of the second component with respect to the first component. The Stewart platform has: A first member, joined to the first component; A second member, joined to the second component; A plurality of legs, connecting the first member and the second member; A drive mechanism that changes the effective length of each leg in order to change the relative position and / or angle of the second member with respect to the first member; And A flexible mechanism that elastically changes the effective length of the leg when an external force acts on the second member and restores the effective length of the leg when the external force is removed. Each of the plurality of legs has a first rod and a second rod. The first rod is supported by a support body so as to be slidable, and the effective length of the leg is changed by sliding. The second rod is joined to the first rod so as to be bendable. The drive mechanism has: A linear member, mounted on the first rod and having flexibility; And An elastic member that elastically deforms when the linear member is stretched to slide the first rod, and generates an elastic restoring force that opposes the tensile force of the linear member.

2. The joint structure according to claim 1, wherein The elastic member also serves as the flexible mechanism.

3. The joint structure according to claim 2, wherein The elastic member includes a non-linear spring member, The amount of deformation of the elastic member is changed by the amount of stretch of the linear member, and the rigidity of the flexible mechanism is variable.

4. The joint structure according to claim 1, wherein The support body is a bearing provided on the first member.

5. The joint structure according to claim 1, wherein The support body is a cylinder member provided on the leg and into which the first rod is slidably inserted.

6. The joint structure according to claim 1, wherein The end of the linear member is pulled out to the outside of the joint structure and connected to a drive source provided separately from the joint structure.

7. The joint structure according to any one of claims 1 to 6, wherein The joint structure further has a locking mechanism that switches between a free state and a locked state. The free state is a state in which the second component is independent of the first component and is movable freely, and the locked state is a state in which the second component is fixed to the first component.

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