Adjustable torsional stiffness joint based on linear guide and bidirectional screw and testing device

Abstract

The present application relates to a torsional stiffness adjustable joint based on linear guide and bidirectional screw and a test device, the joint comprising a joint driving assembly, a stiffness adjusting assembly and a torque output assembly connected in sequence; the stiffness adjusting assembly drives the rectangular spring dynamic support point to slide on the linear guide through the bidirectional screw, changes the distance between the rectangular spring dynamic support point and the rectangular spring static support point, thereby changes the effective working length of the rectangular spring, and achieves the purpose of adjusting the maximum output torque of the joint. The test device adopts a vertical test method, which can reduce or eliminate the influence of the radial bearing friction torque caused by the weight of the joint on the accurate measurement of the joint driving torque. The present application is used for the prototype development, torsional stiffness test and calibration of the torsional stiffness adjustable joint of the space manipulator, which can realize the real-time adjustment of the output torque within the set range of the torsional stiffness, and can also realize the unloading protection when the working torque exceeds the maximum value of the set torsional torque, so as to improve the joint flexibility under the condition that the load torque of the manipulator is unknown, reduce the impact force on the manipulator under the condition of sudden change of the joint torque, and ensure the operation safety and working reliability of the space manipulator.

Description

Technical Field

[0001] This invention belongs to the field of robotics technology, specifically relating to a torsional stiffness adjustable joint and testing device based on a linear guide rail and a bidirectional lead screw. Background Technology

[0002] To ensure high efficiency, reliability, and accuracy in operations, traditional robotic arms require high rigidity and high response speed in their joints, thereby guaranteeing high positional accuracy at the end effector. Traditional rigid joints achieve target tasks through precise positioning, but the rapid response and high torque output of joint movements during operation can raise safety concerns during human-machine interaction. Furthermore, specific types and specifications of robotic arms struggle to meet the requirements of different external loads / torques for various operational targets (especially when the joint load torque exceeds its rated torque). Currently, the main solutions for joint misalignment caused by positioning and assembly errors in precise spatial operations are either compliant control of the robotic arm or requiring the joints to have varying stiffness.

[0003] For complex working scenarios such as confined spaces and unknown target loads, elastic elements or flexible mechanisms are added to the joints of traditional robotic arms to alter the structural stiffness of the moving parts inside the joints. This allows the torque output of the joint to vary with the load. On one hand, when the joint comes into contact with an object and collides, the load torque changes abruptly. The adjustable stiffness joint can mitigate the impact and absorb collision energy, ensuring operational safety. On the other hand, when the load torque of the joint exceeds the rated maximum output torque, the maximum output torque of the joint can be increased by adjusting the elastic structure inside the joint to improve the torsional stiffness, thereby meeting the workload requirements.

[0004] Traditionally, horizontal testing methods are used to test the performance of robotic arm joints. The joint under test is placed horizontally on a test bench, and a transmission chain is formed by an external motor (load torque generator), reducer, torque sensor, electromagnetic clutch, photoelectric encoder, etc. to load the output end of the joint. After the joint under test is powered on, it is driven by its own motor to load the joint and maintain the rotation position or movement speed. This method can measure indicators such as the maximum output torque, angular displacement, angular velocity, and stall current of the joint. However, due to the weight of the joint, a certain torsional friction torque is generated at the radial bearing, which will significantly affect the accurate measurement of the joint driving torque. A vertical testing method is needed to reduce or eliminate this effect.

[0005] For adjustable stiffness robotic arm joints, various types of torsional stiffness-adjustable flexible joints have been developed both domestically and internationally. For example, CN103624797B discloses a rotary adjustable stiffness series elastic robot joint, which mainly uses multiple series elastic bodies to adapt to different degrees of buffering and change the system stiffness. However, it cannot actively change the torsional stiffness of the joint through the stiffness adjustment motor according to changes in load torque. CN104985608B discloses a stiffness-adjustable flexible joint actuator mechanism, which mainly adopts a variable stiffness system with a curved inclined plane-wheel cooperation structure. However, the coaxial layout of the adjustment end motor and the drive end motor increases the axial length of the entire joint, making it unsuitable for... For applications with limited installation space, CN105599004B discloses a stiffness-adjustable robot elastic joint, which mainly achieves stiffness adjustment through a radially arranged stiffness adjustment motor and elastic force transmission components. However, the radially arranged motor results in a large outer diameter of the joint envelope, making it unsuitable for installation in confined spaces. CN106142132B discloses a continuously adjustable stiffness robot flexible joint, which mainly achieves joint adjustment by changing the pre-compression of the elastic element through the movement of the stiffness adjustment structure toward the buffer mechanism. However, the stiffness adjustment motor and joint... The coaxial layout of the drive motor also increases the overall axial length of the joint, making it unsuitable for installation in confined spaces. CN111237280B discloses a stiffness-adjustable angle self-servo valve-controlled hydraulic joint, which mainly controls the pressure in the high-pressure chamber to unload the pressure in the low-pressure chamber by controlling the on / off state of the floating valve core, thereby changing the joint stiffness. However, stiffness-adjustable joints based on the hydraulic unloading principle are difficult to apply to space robotic arm operations in a vacuum environment. CN111360870B discloses a multi-stage adjustable robot variable stiffness joint with buffering function, which mainly uses multi-stage linear gears. The stiffness adjustment is achieved by components such as wheels and parallel elastic telescopic rods, which are relatively complex in structure and have large axial and radial dimensions, making them unsuitable for use in compact space operation environments. CN115556137A discloses a flexible joint for a spatial robotic arm with a left-right helical screw-leaf spring mechanism, which mainly achieves stiffness adjustment through the deformation of the drive motor and the leaf spring mechanism installed on the left-right helical screw and slide rod. However, the friction on the slide rod is large, which can easily cause the two fulcrums to jam during the sliding process when the leaf spring mechanism bends and deforms. Furthermore, no effective testing device and method for the performance index of the flexible joint are proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a torsional stiffness adjustable joint based on a linear guide and a bidirectional lead screw. The maximum output torque of the joint can vary with the load torque and can mitigate impact and absorb collision energy when the load torque changes abruptly. The purpose of this invention is also to provide a joint performance testing device that uses a vertical testing method to reduce or eliminate the influence of the radial bearing friction torque caused by the weight of the joint on the accurate measurement of the joint driving torque.

[0007] To achieve the above objectives, the present invention provides a torsional stiffness adjustable joint based on a linear guide rail and a bidirectional lead screw, comprising a joint drive assembly, a stiffness adjustment assembly, and a torque output assembly connected in sequence; the stiffness adjustment assembly drives the movable fulcrum of a rectangular spring to slide on the linear guide rail via the bidirectional lead screw, changing the distance between the movable fulcrum and the stationary fulcrum of the rectangular spring, thereby changing the effective working length of the rectangular spring and achieving the purpose of adjusting the maximum output torque of the joint.

[0008] The aforementioned torsional stiffness adjustable joint based on a linear guide and a bidirectional lead screw comprises a stiffness adjustment assembly including a linear guide, a bidirectional lead screw, a rectangular spring moving fulcrum, a rectangular spring stationary fulcrum, a stiffness adjustment motor, a rectangular spring, a bevel gear transmission assembly, a housing, a rectangular spring fixing bracket, and a lead screw carriage. The bidirectional lead screw is mounted on the lead screw carriage; the linear guide is mounted on the lead screw carriage; the rectangular spring moving fulcrum is connected to the bidirectional lead screw via a ball nut and to the linear guide via the slide rail; the stiffness adjustment motor and the bevel gear transmission assembly are both mounted at one end of the lead screw carriage, and the stiffness adjustment motor is connected to the bidirectional lead screw via the bevel gear transmission assembly; one end of the rectangular spring is fixedly connected to the rectangular spring fixing bracket, and the rectangular spring... The spring fixing bracket is fixedly connected to the inner wall of the outer shell, and the other end of the rectangular spring is in a cantilever state, making the rectangular spring a flexible body with one cantilever end; the fixed support point of the rectangular spring is fixedly connected to the torque output component; the lead screw carriage is placed on the output end of the joint drive component; the outer shell covers the lead screw carriage, and the lower end face of the outer shell is rigidly fixed to the output end of the joint drive component, fastening the lead screw carriage to the output end of the joint drive component; the linear guide, the bidirectional lead screw, the moving support point of the rectangular spring, and the fixed support point of the rectangular spring are all located inside the outer shell, while the stiffness adjustment motor and the bevel gear transmission group are all located outside the outer shell; the rectangular spring passes through the moving support point of the rectangular spring, and the cantilever end of the rectangular spring passes through the fixed support point of the rectangular spring.

[0009] The aforementioned torsional stiffness adjustable joint based on linear guides and bidirectional lead screws includes two linear guides, arranged on both sides of the bidirectional lead screw; two rectangular spring moving fulcrums 123, which are connected to the two linear guides via slide rails; two rectangular springs, two rectangular spring fixing brackets, and two rectangular spring stationary fulcrums, with the two rectangular springs passing through the two rectangular spring moving fulcrums respectively, and the cantilever ends of the two rectangular springs passing through the two rectangular spring stationary fulcrums respectively; the planes containing the two rectangular springs are parallel to each other, and the two rectangular spring fixing brackets are located on opposite sides of the outer casing.

[0010] The aforementioned torsional stiffness adjustable joint based on linear guide rails and bidirectional lead screws includes a joint drive assembly comprising a joint drive motor, a harmonic reducer, and a first-stage torque output end connected in sequence; the outer shell of the stiffness adjustment assembly is rigidly connected to the first-stage torque output end; the joint drive motor, stiffness adjustment motor, and bevel gear transmission assembly are arranged in parallel along the joint axis, while the linear guide rail, bidirectional lead screw, rectangular spring moving fulcrum, rectangular spring stationary fulcrum, and rectangular spring are arranged in the joint radial direction.

[0011] The aforementioned adjustable torsional stiffness joint based on linear guide rails and bidirectional lead screws includes a rectangular spring fixing bracket that uses a dovetail groove in the axial direction of the joint and a locating pin in the radial direction of the joint to position and fix one end of the rectangular spring.

[0012] The aforementioned adjustable torsional stiffness joint based on linear guide rails and bidirectional lead screws includes a U-shaped groove on the moving fulcrum of a rectangular spring through which the rectangular spring passes; and a rectangular through hole on the stationary fulcrum of the rectangular spring through which the suspended end of the rectangular spring passes, the width of which is greater than the thickness of the rectangular spring.

[0013] The aforementioned torsional stiffness adjustable joint based on linear guide rails and bidirectional lead screws involves the following: When the stiffness adjustment motor drives the bidirectional lead screw to rotate forward and backward via a bevel gear transmission group, the two rectangular spring moving fulcrums simultaneously slide towards or away from each other along the linear guide rail. The rectangular springs, as flexible bodies with one cantilever, change the distance between their two fulcrums when the moving fulcrum moves to the set target position, thus altering the effective working length of the rectangular spring. Consequently, the joint's torsional stiffness also changes, thereby adjusting the joint's maximum torsional output torque. The bidirectional lead screw has self-locking properties, maintaining the working stability of the joint's output torque when the torsional stiffness changes and reaches the set value. When the torsional torque on the rectangular spring exceeds the maximum torque corresponding to the torsional stiffness at the set target position, its cantilevered end moves within the rectangular through-hole in the middle of the rectangular spring's stationary fulcrum. This disturbance deformation of one end of the rectangular spring achieves passive compliance and overload protection for the joint, suppressing joint impact and vibration under sudden changes in load torque.

[0014] The aforementioned torsional stiffness adjustable joint based on linear guides and bidirectional lead screws includes a torque output assembly comprising a torque output disc bracket, a torque output disc, bearings, and bearing retaining flanges. The torque output disc bracket is rigidly connected to the outer shell of the stiffness adjustment assembly via four bolts in an "X" shaped direction. The torque output disc is connected to the torque output disc bracket via bearings and bearing retaining flanges, and the torque of the torsional stiffness adjustable joint is output through the torque output disc. The top of the rectangular spring static support is fixed to the torque output disc with screws.

[0015] The present invention also provides a testing device for the aforementioned torsional stiffness adjustable joint, comprising a worktable, a mounting frame, a torque generator, a two-stage gear reducer, a torque sensor, an electromagnetic clutch, a torque transmission disk, an angle counter, and an angle amplifier; the torque generator, the two-stage gear reducer, the torque sensor, the electromagnetic clutch, and the torque transmission disk are connected in sequence and supported by the worktable; the large gear end of the angle amplifier is fixedly connected to the torque transmission disk, the large and small gears of the angle amplifier mesh with each other, the small gear end of the angle amplifier is fixedly connected to the angle counter, and the angle counter outputs the amplified deflection angle of the torque output disk of the torsional stiffness adjustable joint under test; the mounting frame is disposed on the worktable for mounting and supporting the torsional stiffness adjustable joint under test, and the torque output component of the torsional stiffness adjustable joint under test is connected to the torque transmission disk; the axis of the torsional stiffness adjustable joint under test is coaxial with the axis of the torque transmission disk and perpendicular to the horizontal platform surface of the worktable.

[0016] The aforementioned testing device for an adjustable torsional stiffness joint outputs a gradually increasing driving torque to simulate an external load torque, causing the stiffness adjustment component of the tested adjustable torsional stiffness joint to passively undergo flexible deformation. By measuring the flexible rotation angle of the tested adjustable torsional stiffness joint and the linear displacement of the working length of the deformed rectangular spring relative to the original set working length, a curve showing the relationship between the load torque and the joint angular displacement is plotted, which is used to calibrate and display the adjustable torsional stiffness of the joint.

[0017] Compared with the prior art, the beneficial technical effects of the present invention are:

[0018] This invention relates to a torsional stiffness adjustable joint based on linear guides and bidirectional lead screws. By adding an elastic mechanism to a traditional robotic arm joint, the structural stiffness of the internal moving parts of the joint is altered, allowing the torque output of the torsional stiffness adjustable joint to vary with the load torque. On one hand, when the joint comes into contact with an object and collides, the sudden change in load torque allows the torsional stiffness adjustable joint to mitigate the impact and absorb the energy of the collision, ensuring operational safety. On the other hand, when the load torque of the torsional stiffness adjustable joint exceeds the rated maximum output torque, the maximum output torque of the torsional stiffness adjustable joint can be increased by adjusting the internal elastic structure of the joint to improve the torsional stiffness, thereby meeting the workload requirements. The testing device for the torsional stiffness adjustable joint of this invention uses a vertical method to measure the maximum output torque, angular displacement, angular velocity, stall current, and other indicators of the torsional stiffness adjustable joint, which can reduce or eliminate the influence of the radial bearing friction torque caused by the weight of the torsional stiffness adjustable joint on the accurate measurement of the joint driving torque.

[0019] This invention is used for the prototype development, torsional stiffness testing and calibration of adjustable joints for space robotic arms. It can realize real-time adjustment of output torque within the set range of torsional stiffness, and can also realize unloading protection when the working torque exceeds the set maximum value of torsional torque. This improves the joint compliance of the robotic arm under unknown load torque conditions, reduces the impact force on the robotic arm under sudden changes in joint torque, and ensures the operational safety and reliability of the space robotic arm. Attached Figure Description

[0020] The torsional stiffness adjustable joint and testing device based on linear guide rail and bidirectional lead screw of the present invention are given by the following embodiments and figures.

[0021] Figure 1 This is a schematic diagram of an adjustable torsional stiffness joint based on a linear guide and a bidirectional lead screw, according to an embodiment of the present invention.

[0022] Figure 2 This is a schematic diagram showing the connection relationship between the rectangular spring and the outer shell in an embodiment of the present invention.

[0023] Figure 3 This is a schematic diagram showing the connection relationship between the linear guide, the bidirectional lead screw, and the moving fulcrum of the rectangular spring in an embodiment of the present invention.

[0024] Figure 4 This is a schematic diagram showing the connection relationship between the stiffness adjustment component and the torque output component in an embodiment of the present invention.

[0025] Figure 5 This is a schematic diagram of the torque output component in an embodiment of the present invention.

[0026] Figure 6 This is a schematic diagram illustrating the application of the torsional stiffness adjustable joint based on linear guide rails and bidirectional lead screws in a multi-degree-of-freedom robotic arm according to an embodiment of the present invention.

[0027] Figure 7 This is a schematic diagram of the torsional stiffness adjustable joint testing device according to an embodiment of the present invention. Detailed Implementation

[0028] The following will combine Figures 1 to 7 The present invention provides a further detailed description of the torsional stiffness adjustable joint and testing device based on linear guide rails and bidirectional lead screws.

[0029] Figure 1 The diagram shown is a schematic diagram of a torsional stiffness adjustable joint based on a linear guide and a bidirectional lead screw according to an embodiment of the present invention.

[0030] See Figure 1 The torsional stiffness adjustable joint 1 based on linear guide rail and bidirectional lead screw in this embodiment includes a joint drive assembly 11, a stiffness adjustment assembly 12 and a torque output assembly 13 connected in sequence.

[0031] The joint drive assembly 11 is a general-purpose robotic arm joint drive assembly that outputs a fixed rated working torque. The joint drive assembly 11 includes a joint drive motor 111, a harmonic reducer 112, and a first-stage torque output terminal 113 connected in sequence.

[0032] The stiffness adjustment component 12 drives the movable fulcrum of the rectangular spring to slide on the linear guide rail through a bidirectional lead screw, thereby changing the distance between the movable fulcrum and the stationary fulcrum of the rectangular spring, thus changing the effective working length of the rectangular spring and achieving the purpose of adjusting the maximum output torque of the joint. It has the advantages of low friction during the movement process and that the two fulcrums of the rectangular spring are not easy to jam during the bending elastic deformation process.

[0033] Figure 2 The diagram shown illustrates the connection between the rectangular spring and the outer shell in an embodiment of the present invention. Figure 3 The diagram shown illustrates the connection relationship between the linear guide, the bidirectional lead screw, and the rectangular spring's moving fulcrum in an embodiment of the present invention. Figure 4 The diagram shown illustrates the connection relationship between the stiffness adjustment component and the torque output component in an embodiment of the present invention.

[0034] See Figures 1 to 4 The stiffness adjustment component 12 is the core functional component of the torsional stiffness adjustable joint 1, including a linear guide rail 121, a two-way lead screw 122, a rectangular spring moving fulcrum 123, a rectangular spring stationary fulcrum 124, a stiffness adjustment motor 125, a rectangular spring 126, a bevel gear transmission group 127, a housing 128, a rectangular spring fixing bracket 129, and a lead screw slide 1210.

[0035] The bidirectional lead screw 122 is mounted on the lead screw carriage 1210;

[0036] There are two linear guide rails 121, both of which are mounted on the lead screw carriage 1210 and are respectively arranged on both sides of the bidirectional lead screw 122;

[0037] There are two rectangular spring moving fulcrums 123. Both rectangular spring moving fulcrums 123 are connected to the bidirectional lead screw 122 through ball nuts. The two rectangular spring moving fulcrums 123 are connected to two linear guide rails 121 respectively through slide rails.

[0038] The stiffness adjustment motor 125 and the bevel gear transmission group 127 are both installed at one end of the lead screw slide 1210. The stiffness adjustment motor 125 is connected to the bidirectional lead screw 122 through the bevel gear transmission group 127.

[0039] One end of the rectangular spring 126 is fixedly connected to the rectangular spring fixing bracket 129, and the rectangular spring fixing bracket 129 is fixedly connected to the inner wall of the outer shell 128. The other end of the rectangular spring 126 is in a cantilever state, making the rectangular spring 126 a flexible body with one end cantilevered. There are two rectangular springs 126, and correspondingly two rectangular spring fixing brackets 129. The planes on which the two rectangular springs 126 are located are parallel to each other, and the two rectangular spring fixing brackets 129 are located on opposite sides of the outer shell 128 (that is, the fixing ends of the two rectangular springs 126 are not on the same side).

[0040] There are two rectangular spring static support points 124, and both rectangular spring static support points 124 are fixedly connected to the torque output component 13.

[0041] The lead screw slide 1210 is placed on the first-stage torque output end 113 of the joint drive assembly 11. The outer shell 128 covers the lead screw slide 1210. The lower end face of the outer shell 128 is rigidly connected to the first-stage torque output end 113, thus fastening the lead screw slide 1210 to the first-stage torque output end 113.

[0042] Two linear guide rails 121, a bidirectional lead screw 122, two rectangular spring moving fulcrums 123 and two rectangular spring stationary fulcrums 124 are all located inside the housing 128, while the stiffness adjustment motor 125 and the bevel gear transmission assembly 127 are all located outside the housing 128; two rectangular springs 126 pass through the two rectangular spring moving fulcrums 123 respectively, and the cantilever ends of the two rectangular springs 126 pass through the two rectangular spring stationary fulcrums 124 respectively.

[0043] like Figure 1 In this embodiment, the joint drive motor 111 and the stiffness adjustment motor 125 and their transmission chain (i.e., bevel gear transmission group 127) are arranged in parallel along the joint axis. The components of the adjustment mechanism of the stiffness adjustment assembly 12 (linear guide rail 121, bidirectional lead screw 122, rectangular spring moving fulcrum 123, rectangular spring stationary fulcrum 124, and rectangular spring 126) are arranged in the joint radial direction. The overall structure is simple and compact, and it is suitable for space robotic arms under the constraint of narrow installation space.

[0044] Better, such as Figure 2 The rectangular spring fixing bracket 129 uses a dovetail groove in the joint axis and a positioning pin in the joint radial direction to position and fix one end of the rectangular spring 126.

[0045] Better, such as Figure 3 A U-shaped groove is provided on the movable fulcrum 123 of the rectangular spring, and the rectangular spring 126 passes through the U-shaped groove of the movable fulcrum 123 of the rectangular spring.

[0046] Better, such as Figure 4A rectangular through hole is provided on the fixed support point 124 of the rectangular spring, and the suspended end of the rectangular spring 126 passes through the rectangular through hole. The width of the rectangular through hole is greater than the thickness of the rectangular spring 126. The top end of the fixed support point 124 of the rectangular spring is fixed to the torque output assembly 13 by a screw.

[0047] Figure 5 The figure shown is a schematic diagram of the torque output component in an embodiment of the present invention.

[0048] The torque output component 13 is installed at the output end of the stiffness adjustment component 12 and is used for torque output of the torsional stiffness adjustable joint.

[0049] See Figure 5 The torque output assembly 13 includes a torque output disc bracket 134, a torque output disc 133, a bearing 132, and a bearing retaining flange 131. The torque output disc bracket 134 is rigidly connected to the outer shell 128 of the stiffness adjustment assembly 12 by four bolts in an "X" direction. The torque output disc 133 is connected to the torque output disc bracket 134 through the bearing 132 and the bearing retaining flange 131, and the torque of the torsional stiffness adjustable joint is output through the torque output disc 133.

[0050] The top of the rectangular spring static support 124 is fixed to the torque output disk 133 by a screw.

[0051] The working principle of the torsional stiffness adjustable joint based on linear guide rail and bidirectional lead screw in this invention embodiment is as follows:

[0052] When the stiffness adjustment motor 125 drives the bidirectional lead screw 122 to rotate forward and in reverse through the bevel gear transmission group 127, the two rectangular spring moving fulcrums 123 can slide simultaneously towards or in opposite directions along the linear guide rail 121. As a flexible body with one cantilever, when the rectangular spring moving fulcrum 123 moves to the set target position, the distance between the two fulcrums of the rectangular spring 126 (i.e., the distance between the rectangular spring moving fulcrum 123 and the rectangular spring stationary fulcrum 124) changes, which changes the effective working length of the rectangular spring 126. Therefore, the joint torsional stiffness will also change, thereby adjusting the maximum torsional output torque of the joint. The bidirectional lead screw 122 has self-locking properties, and when the torsional stiffness changes and reaches the set value, the working stability of the joint output torque is maintained.

[0053] like Figure 4 When the torsional torque on the rectangular spring 126 exceeds the maximum torque corresponding to the torsional stiffness at the set target position, its suspended end can move within the rectangular through hole in the middle of the static support point 124 of the rectangular spring. By perturbing and deforming one end of the rectangular spring 126, the joint can achieve passive compliance and overload protection, which can suppress the impact and vibration of the joint under sudden changes in applied torque (load torque).

[0054] In this embodiment, as Figure 1 and Figure 4 The torsional stiffness adjustable joint 1 is divided into two types: large joint and small joint. The large joint has a maximum output torque ≥120Nm, an adjustable torsional stiffness range of 500Nm / rad-1400Nm / rad, and an adjustable effective working length range of 50mm-85mm for the rectangular spring 126. The small joint has a maximum output torque of not less than 40Nm, an adjustable torsional stiffness range of 150Nm / rad-500Nm / rad, and an adjustable effective working length range of 30mm-55mm for the rectangular spring 126. The stiffness adjustment motor 125 can adjust the joint torsional stiffness by automatically starting and stopping as needed, so that the maximum output torque of the joint is maintained at the set value, and the output torque accuracy is better than 1Nm.

[0055] The torsional stiffness adjustable joint 1 can be applied to multi-degree-of-freedom robotic arm systems. For example... Figure 6 In (a), in the four-degree-of-freedom spatial robotic arm, large joints 3-1, 3-2, 3-3, and small joints 4-1 all adopt the torsional stiffness adjustable joint 1 of this embodiment, and an end effector 5-1 can be installed at the end of the robotic arm; as shown in Figure (a), the large joints 3-1, 3-2, 3-3, and 4-1 all adopt the torsional stiffness adjustable joint 1 of this embodiment, and an end effector 5-1 can be installed at the end of the robotic arm; Figure 6 In (b), the large joints 3-4 and small joints 4-2 in the planar two-degree-of-freedom robotic arm both adopt the torsional stiffness adjustable joint 1 of this embodiment. At the same time, the end effector mechanism 5-2 can be installed at the end of the robotic arm for grasping, twisting and other operations on the target object in a spatial environment.

[0056] Figure 7 The diagram shown is a schematic diagram of the torsional stiffness adjustable joint testing device according to an embodiment of the present invention.

[0057] The torsional stiffness adjustable joint testing device of this embodiment can be used to test and calibrate the torsional stiffness of torsional stiffness adjustable joints of different sizes and different maximum output torques.

[0058] like Figure 7 As shown, the torsional stiffness adjustable joint testing device of this embodiment adopts a vertical layout during operation. The torsional stiffness adjustable joint testing device of this embodiment includes a worktable 29, a mounting frame 28, a torque generator 21, a two-stage gear reducer 22, a torque sensor 23, an electromagnetic clutch 24, a torque transmission disk 25, an angle counter 26, and an angle amplifier 27 (including large and small gears). During joint testing, the torque transmission disk 25 is fixedly connected to the torque output disk 133 of the torsional stiffness adjustable joint 1. The large gear end of the angle amplifier 27 is fixedly connected to the torque transmission disk 25, and the large and small gears of the angle amplifier 27 mesh with each other. The small gear end of the angle amplifier 27 is fixedly connected to the angle counter 26, and the angle counter 26 outputs the amplified deflection angle of the torque output disk 133.

[0059] The torque generator 21, the two-stage gear reducer 22, the torque sensor 23, the electromagnetic clutch 24 and the torque transmission disc 25 are connected in sequence, and the two-stage gear reducer 22, the torque sensor 23, the electromagnetic clutch 24 and the torque transmission disc 25 constitute the transmission chain motion of the torque generator 21.

[0060] The worktable 29 is used to support the torque generator 21, the two-stage gear reducer 22, the torque sensor 23, the electromagnetic clutch 24, and the torque transmission disc 25;

[0061] Mounting bracket 28 is set on workbench 29 for mounting and supporting the adjustable torsional stiffness joint 1 to be measured. The torque output component 13 of the adjustable torsional stiffness joint 1 to be measured is connected to torque transmission disk 25.

[0062] The axis of the adjustable torsional stiffness joint 1 is coaxial with the axis of the torque transmission disk 25 and perpendicular to the horizontal platform surface of the worktable 29.

[0063] The torque generator 21 applies the generated external torque to the torsional stiffness adjustable joint 1 under test through a transmission chain consisting of a two-stage gear reducer 22, a torque sensor 23, an electromagnetic clutch 24, and a torque transmission disc 25. Unlike traditional horizontal testing methods, the vertical layout can eliminate the influence of the radial bearing friction torque generated by the joint weight on the joint torsional torque test.

[0064] like Figure 7 In (a), the joint drive assembly 11 of the torsional stiffness adjustable joint 1 under test is removed (i.e., only the stiffness adjustment assembly 12 and the torque output assembly 13 are present). At this point, the performance of the torsional stiffness adjustable joint 1 under test is demonstrated only when an external load torque is present. Figure 7 In (b), the torsional stiffness adjustable joint 1 under test includes a joint drive component 11, a stiffness adjustment component 12 and a torque output component 13. At this time, the performance of the torsional stiffness adjustable joint 1 under test is tested when the external load torque and the drive torque of the joint drive component 11 are present at the same time.

[0065] like Figure 3 and Figure 7The torsional stiffness adjustable joint testing device introduces a torque generator 21 and its transmission chain, and connects a torque transmission disk 25 to the output end (i.e., torque output component 13) of the torsional stiffness adjustable joint 1 under test. The torque generator 21 and its transmission chain output a gradually increasing driving torque (simulating external load torque), which causes the internal elastic mechanism of the torsional stiffness adjustable joint 1 under test to passively undergo flexible deformation. By measuring the flexible rotation angle of the torsional stiffness adjustable joint 1 under test and the linear displacement of the working length of the rectangular spring 126 after deformation relative to the original set working length, a curve showing the relationship between the load torque and the joint angular displacement is plotted, which can be used to calibrate and display the adjustable torsional stiffness of the joint. In this embodiment, the torque range output by the torque generator 21 to the torsional stiffness adjustable joint 1 under test through its transmission chain is 0-180 Nm, the linear displacement measurement accuracy of the working length of the rectangular spring 126 is better than 1 mm, and the angular displacement measurement accuracy of the torsional stiffness adjustable joint 1 under test is better than 0.5°.

[0066] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

[0067] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A testing device for a torsional stiffness adjustable joint based on a linear guide and a bidirectional lead screw, characterized in that, The torsional stiffness adjustable joint based on linear guide rail and bidirectional lead screw includes a joint drive assembly, a stiffness adjustment assembly and a torque output assembly connected in sequence. The stiffness adjustment assembly drives the movable fulcrum of the rectangular spring to slide on the linear guide rail through the bidirectional lead screw, changing the distance between the movable fulcrum and the stationary fulcrum of the rectangular spring, thereby changing the effective working length of the rectangular spring and achieving the purpose of adjusting the maximum output torque of the joint. The testing device includes a workbench, a mounting frame, a torque generator, a two-stage gear reducer, a torque sensor, an electromagnetic clutch, a torque transmission disc, an angle counter, and an angle amplifier. A torque generator, a two-stage gear reducer, a torque sensor, an electromagnetic clutch, and a torque transmission disk are connected in sequence and supported by a worktable. The large gear end of the angle amplifier is fixedly connected to the torque transmission disk. The large and small gears of the angle amplifier mesh with each other. The small gear end of the angle amplifier is fixedly connected to the angle counter. The angle counter outputs the amplified deflection angle of the torque output disk of the adjustable torsional stiffness joint under test. A mounting bracket is set on the worktable for mounting and supporting the adjustable torsional stiffness joint under test. The torque output component of the adjustable torsional stiffness joint under test is connected to the torque transmission disk. The axis of the adjustable torsional stiffness joint under test is coaxial with the axis of the torque transmission disk and perpendicular to the horizontal platform surface of the worktable. The testing device outputs a gradually increasing driving torque to simulate an external load torque, causing the stiffness adjustment component of the tested adjustable torsional stiffness joint to passively deform flexibly. By measuring the flexible rotation angle of the tested adjustable torsional stiffness joint and the linear displacement of the working length of the deformed rectangular spring relative to the original set working length, a curve showing the relationship between the load torque and the joint angular displacement is plotted, which is used to calibrate and display the adjustable torsional stiffness of the joint.

2. The testing device for a torsional stiffness adjustable joint based on a linear guide and a bidirectional lead screw as described in claim 1, characterized in that, The stiffness adjustment assembly includes a linear guide rail, a two-way lead screw, a rectangular spring moving fulcrum, a rectangular spring stationary fulcrum, a stiffness adjustment motor, a rectangular spring, a bevel gear transmission assembly, a housing, a rectangular spring fixing bracket, and a lead screw slide. The bidirectional lead screw is mounted on the lead screw carriage; Linear guide rails are mounted on the lead screw carriage; The rectangular spring's moving fulcrum is connected to a bidirectional lead screw via a ball nut, and to a linear guide via a slide rail; The stiffness adjustment motor and the bevel gear transmission assembly are both installed at one end of the lead screw slide. The stiffness adjustment motor is connected to the double-acting lead screw through the bevel gear transmission assembly. One end of the rectangular spring is fixedly connected to the rectangular spring fixing bracket, the rectangular spring fixing bracket is fixedly connected to the inner side wall of the outer shell, and the other end of the rectangular spring is in a cantilever state, making the rectangular spring a flexible body with one end cantilevered. The rectangular spring's static support point is fixedly connected to the torque output component; The lead screw carriage is placed on the output end of the joint drive assembly; the outer casing covers the lead screw carriage, and the lower end face of the outer casing is rigidly connected to the output end of the joint drive assembly, thus fastening the lead screw carriage to the output end of the joint drive assembly. The linear guide, the two-way lead screw, the moving fulcrum of the rectangular spring, and the stationary fulcrum of the rectangular spring are all located inside the housing, while the stiffness adjustment motor and the bevel gear transmission assembly are all located outside the housing; the rectangular spring passes through the moving fulcrum of the rectangular spring, and the cantilever end of the rectangular spring passes through the stationary fulcrum of the rectangular spring.

3. The testing device for a torsional stiffness adjustable joint based on a linear guide and a bidirectional lead screw as described in claim 2, characterized in that, There are two sets of linear guides, which are arranged on both sides of the bidirectional lead screw; there are two rectangular spring moving fulcrums, which are connected to the two sets of linear guides respectively through slide rails. There are two rectangular springs, two rectangular spring fixing brackets, and two rectangular spring static supports. The two rectangular springs pass through the two rectangular spring moving supports respectively, and the cantilever ends of the two rectangular springs pass through the two rectangular spring static supports respectively. The planes on which the two rectangular springs are located are parallel to each other, and the two rectangular spring fixing brackets are located on opposite sides of the outer shell.

4. The testing device for a torsional stiffness adjustable joint based on a linear guide and a bidirectional lead screw as described in claim 2, characterized in that, The joint drive assembly includes a joint drive motor, a harmonic reducer, and a first-stage torque output end connected in sequence; the outer shell of the stiffness adjustment assembly is rigidly connected to the first-stage torque output end; the joint drive motor, the stiffness adjustment motor, and the bevel gear transmission group are arranged in parallel along the joint axis, and the linear guide, the bidirectional lead screw, the rectangular spring moving fulcrum, the rectangular spring stationary fulcrum, and the rectangular spring are arranged in the joint radial direction.

5. The testing device for a torsional stiffness adjustable joint based on a linear guide and a bidirectional lead screw as described in claim 2, characterized in that, The rectangular spring fixing bracket uses a dovetail groove in the axial direction of the joint and a locating pin in the radial direction of the joint to position and fix one end of the rectangular spring.

6. The testing device for a torsional stiffness adjustable joint based on a linear guide and a bidirectional lead screw as described in claim 2, characterized in that, A U-shaped groove is made on the moving fulcrum of the rectangular spring, and the rectangular spring passes through the U-shaped groove of the moving fulcrum of the rectangular spring; a rectangular through hole is made on the stationary fulcrum of the rectangular spring, and the cantilever end of the rectangular spring passes through the rectangular through hole, the width of the rectangular through hole being greater than the thickness of the rectangular spring.

7. The testing device for a torsional stiffness adjustable joint based on a linear guide and a bidirectional lead screw as described in claim 3, characterized in that, When the stiffness adjustment motor drives the bidirectional lead screw to rotate forward and backward through the bevel gear transmission set, the two rectangular spring moving fulcrums slide simultaneously towards or away from each other along the linear guide rail. As a flexible body with one cantilever, when the rectangular spring moving fulcrum moves to the set target position, the distance between the rectangular spring moving fulcrum and the rectangular spring stationary fulcrum changes, which changes the effective working length of the rectangular spring. Therefore, the joint torsional stiffness will also change, thereby adjusting the maximum torsional output torque of the joint. The bidirectional lead screw has self-locking properties, so when the torsional stiffness changes and reaches the set value, the working stability of the joint output torque is maintained. When the torsional torque on the rectangular spring exceeds the maximum torque corresponding to the torsional stiffness at the set target position, its cantilever end moves within the rectangular through hole in the middle of the static support point of the rectangular spring. The passive compliance of the joint and overload protection are achieved by the disturbance deformation of one end of the rectangular spring.

8. The testing device for a torsional stiffness adjustable joint based on a linear guide and a bidirectional lead screw as described in claim 3, characterized in that, The torque output assembly includes a torque output disc bracket, a torque output disc, a bearing, and a bearing retaining flange; the torque output disc bracket and the outer housing of the stiffness adjustment assembly are rigidly connected by four bolts in an "X" direction; the torque output disc is connected to the torque output disc bracket through the bearing and the bearing retaining flange, and the torque of the torsional stiffness adjustable joint is output through the torque output disc; the top of the rectangular spring static support is fixed to the torque output disc by screws.

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