Variable-stiffness robot joint

Abstract

The invention discloses a variable stiffness robot joint. The variable-stiffness robot joint comprises a joint unit and an adjusting unit. The joint unit comprises an input disc and an output disc; the adjusting unit comprises a plurality of rigidity changing mechanisms and a plurality of driving mechanisms which are arranged in the accommodating cavity; the rigidity changing mechanism comprises a rigidity changing sliding block, a reset spring and a leaf spring, one end of the rigidity changing sliding block is connected with the input disc through the reset spring, and the other end of the rigidity changing sliding block is connected with the output disc through the leaf spring; the driving mechanism comprises a pneumatic tendon, and the pneumatic tendon is connected with the rigidity-variable sliding block. The variable-rigidity mechanism is driven by the driving mechanism to adjust the rigidity change of the joint unit. By adopting the pneumatic muscle actuator, the light weight and high power weight ratio of the structure can be realized, and the flexible layout of the pneumatic muscle actuator in a limited space is allowed. The inflation and deflation process of the pneumatic tendon can achieve quick response, the energy transmission efficiency is high, heat dissipation can be achieved through convection of compressed air, and equipment is further simplified.

Description

Technical Field

[0001] The invention relates to the technical field of robots, and in particular to a variable-rigidity robot joint. Background Art

[0002] With the rapid development of robotics technology, its applications in industrial manufacturing, medical care, home services and other fields are becoming increasingly extensive, and the complexity and safety requirements of human-machine collaboration scenarios have increased significantly.

[0003] Traditional robot safety strategies mostly rely on rigid materials and high-energy drive systems. Although they can ensure basic stability, they have the following technical bottlenecks: Existing solutions often use high-power motors and redundant structures to achieve high load-bearing capacity, resulting in high system energy consumption, heavy weight, and difficult to control manufacturing costs. For example, industrial robot joints mostly rely on rigid transmission. Although they can maintain accuracy, they consume a lot of energy after long-term operation, and their lightweight design is limited. Although rigid structures can improve load capacity, they lack flexible buffering mechanisms and are prone to mechanical damage due to sudden impacts. In addition, they have a low degree of modularity and require overall disassembly for maintenance, which is inefficient. Existing control algorithms are not capable of fusing multi-sensor data, making it difficult to achieve high-precision dynamic adjustment, especially under variable load conditions, where trajectory deviations are prone to occur.

[0004] In summary, existing robotics technology has technical problems such as high energy consumption, high cost, complex structure and low practicality. Summary of the invention

[0005] The purpose of this application is to overcome the above-mentioned technical deficiencies and propose a variable stiffness robot joint to solve the technical problems of high energy consumption, high cost, complex structure and low practicality in the prior art.

[0006] In order to achieve the above technical objectives, this application adopts the following technical solutions: The present application provides a variable stiffness robot joint, comprising a joint unit and an adjustment unit.

[0007] The joint unit comprises an input disk and an output disk, wherein the input disk and the output disk are arranged opposite to each other to form a receiving cavity; An adjusting unit, comprising a plurality of rigidity-changing mechanisms and a plurality of driving mechanisms disposed in the accommodating cavity; The rigidity changing mechanism comprises a rigidity changing slider, a return spring and a leaf spring, one end of the rigidity changing slider is connected to the input disk through the return spring, and the other end of the rigidity changing slider is connected to the output disk through the leaf spring; The driving mechanism includes a pneumatic muscle, which is connected to the variable-rigidity slider and is used to drive the variable-rigidity slider to slide linearly to change the length of the return spring and the leaf spring.

[0008] In some embodiments of the present application, at least three return springs are distributed along the circumference of the input disk, each return spring extends radially along the input disk, the two sides of each variable-rigidity slider are respectively connected to the two pneumatic tendons, and the two ends of each pneumatic tendon are connected to the two variable-rigidity sliders.

[0009] In some embodiments of the present application, the joint unit further includes a fixed shaft and a sleeve, the fixed shaft is connected to a surface of the input disk facing the output disk, and the sleeve is sleeved on the outside of the fixed shaft and connected to the return spring.

[0010] In some embodiments of the present application, the joint unit also includes an encoder, which includes a magnetic head and a magnetic disk. The magnetic head is arranged around the sleeve and connected to the input disk, and the magnetic disk is connected to the output disk for detecting the deflection angle between the input disk and the output disk.

[0011] In some embodiments of the present application, the driving mechanism further includes a boosting device and a one-way valve, the boosting device is connected to the pneumatic muscle through the one-way valve, and the one-way valve is connected to the shaft sleeve.

[0012] In some embodiments of the present application, an air inlet and an air outlet are respectively provided at both ends of the pneumatic tendon, and the air inlet is respectively connected to the air outlet and the boosting device.

[0013] In some embodiments of the present application, the driving mechanism further includes a pneumatic muscle connector, which is respectively sleeved on the outer side of the end of the pneumatic muscle and fixedly connected to the variable rigidity slider.

[0014] In some embodiments of the present application, the joint unit further includes a cross roller bearing, and the cross roller bearing is respectively connected to the input disk and the output disk.

[0015] In some embodiments of the present application, the variable rigidity mechanism further includes a linear guide rail assembly, which is respectively fixedly connected to the input disk and slidably connected to the variable rigidity slider, and the extension direction of each linear guide rail assembly is parallel to the extension direction of one of the return springs.

[0016] In some embodiments of the present application, the variable stiffness mechanism further includes a linear sensor, and the linear sensor is connected to the variable stiffness slider.

[0017] Compared with the prior art, the technical solution provided by this application has the following beneficial technical effects: The present application designs a variable stiffness mechanism and a driving mechanism between the input disk and the output disk, and the driving mechanism drives the variable stiffness mechanism to adjust the stiffness change of the joint unit. Among them, the use of pneumatic tendons as driving mechanisms can achieve lightweight structures and high power-to-weight ratios, allowing them to be flexibly arranged in limited spaces. By using air pressure as the driving force, the inflation and deflation process of the pneumatic tendons can achieve rapid response, high energy transmission efficiency, and can dissipate heat through compressed air convection, further simplifying the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solution in this application, the following is a brief introduction to the drawings required for use in the embodiments: Figure 1 is a structural schematic diagram of a variable stiffness robot joint provided in an embodiment of the present application; Figure 2 is a structural schematic diagram of a joint unit provided in an embodiment of the present application; Figure 3 is a structural schematic diagram of an adjustment unit provided in an embodiment of the present application; Figure 4 It is a partial schematic diagram of an adjustment unit provided in an embodiment of the present application.

[0019] Reference numerals: Joint unit 1, adjustment unit 2; Input disc 11, output disc 12, cross roller bearing 13, bushing 14, encoder 15; Variable rigidity mechanism 21, variable rigidity slider 211, return spring 212, leaf spring 213, check valve 214, linear guide assembly 215, linear sensor 216; Driving mechanism 22 , pneumatic muscle 221 , and pneumatic muscle connector 222 . DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0021] Those skilled in the art will appreciate that in this specification, the wording "including" is an open-ended expression, which means that the described features exist but does not exclude other features. The directional words "up", "down", "left", "right", etc. are exemplary directions based on the drawings. Features defined as "first" and "second" implicitly include one or more of the features. Singular expressions can also be used in the plural. "Multiple" means two or more. The terms "installed", "connected", and "connected" can be fixed connections, detachable connections, or integrated connections; they can be directly connected, or indirectly connected through an intermediate medium, or they can be internal connections between two elements. In addition, "connected" can include wireless connections.

[0022] The purpose of this application is to overcome the above-mentioned technical deficiencies and propose a variable stiffness robot joint to solve the technical problems of high energy consumption, high cost, complex structure and low practicality in the prior art.

[0023] In order to achieve the above technical objectives, this application adopts the following technical solutions: like Figure 1 and Figure 2 As shown, the present application provides a variable stiffness robot joint, including a joint unit 1 and an adjustment unit 2.

[0024] The joint unit 1 includes an input disk 11 and an output disk 12, wherein the input disk 11 and the output disk 12 are arranged opposite to each other to form a receiving cavity; the joint unit 1 is the basic structural part of the robot joint, and is responsible for transmitting motion and force.

[0025] The adjusting unit 2 includes a plurality of rigidity changing mechanisms 21 and a plurality of driving mechanisms 22 arranged in the accommodating cavity; The rigidity changing mechanism 21 comprises a rigidity changing slider 211, a return spring 212 and a leaf spring 213. One end of the rigidity changing slider 211 is connected to the input disk 11 through the return spring 212, and the other end of the rigidity changing slider 211 is connected to the output disk 12 through the leaf spring 213. The driving mechanism 22 includes a pneumatic muscle 221 , which is connected to the variable rigidity slider 211 and is used to drive the variable rigidity slider 211 to slide linearly to change the length of the return spring 212 and the leaf spring 213 .

[0026] When the driving air pressure of the pneumatic muscle 221 is changed, the length of the pneumatic muscle 221 changes, driving the variable rigidity slider 211 to move, changing the length of the return spring 212 and the leaf spring 213, thereby adjusting the stiffness of the joint unit 1. The bending degree of the leaf spring 213 and the compression amount of the return spring 212 determine the stiffness of the joint.

[0027] The present application designs a variable stiffness mechanism 21 and a driving mechanism 22 between the input disk 11 and the output disk 12, and the driving mechanism 22 drives the variable stiffness mechanism 21 to adjust the stiffness change of the joint unit 1. Among them, the use of pneumatic tendon 221 as the driving mechanism 22 can achieve lightweight structure and high power-to-weight ratio, allowing it to be flexibly arranged in a limited space. By using air pressure as the driving force, the inflation and deflation process of the pneumatic tendon 221 can achieve rapid response, high energy transmission efficiency, and can dissipate heat through compressed air convection, further simplifying the equipment.

[0028] Compared with the traditional solution that uses motors as driving power, the present application uses pneumatic tendons 221 as driving components. While ensuring the advantage of high driving power response frequency, it avoids the technical problem of large equipment weight and size caused by motors as driving power sources.

[0029] like Figure 3 As shown, in some embodiments of the present application, at least three return springs 212 are distributed along the circumference of the input disk 11, each return spring 212 extends radially along the input disk 11, the two sides of each variable-rigidity slider 211 are respectively connected to the two pneumatic tendons 221, and the two ends of each pneumatic tendon 221 are connected to the two variable-rigidity sliders 211.

[0030] In this embodiment, three return springs 212 and three pneumatic muscles 221 are taken as an example. In fact, in other embodiments, the number of return springs 212 and pneumatic muscles 221 can also be four or more.

[0031] The three return springs 212 are all connected to the center of the input disk 11 and extend outward. Any two adjacent return springs 212 form an equal angle. Such a layout can ensure that the stiffness change of the joint in all directions during the rotation process is uniform.

[0032] The three pneumatic muscles 221 are fixedly installed in the accommodating cavity in a triangular shape and are fixedly connected to the variable rigidity slider 211, thereby indirectly connected to the reset spring 212. This connection method forms a stable network structure, which can improve the stability of the structure and ensure uniform transmission of force.

[0033] When the joint stiffness needs to be increased, the pneumatic muscle 221 is contracted by changing the air pressure, thereby pushing the variable-stiffness slider 211 to move toward the center of the input disk 11, compressing the length of the return spring 212 and increasing the bending degree of the leaf spring 213, thereby reducing the joint stiffness and increasing the flexibility.

[0034] When the joint stiffness needs to be reduced, the pneumatic muscle 221 is relaxed by the reverse change of air pressure, and the variable-stiffness slider 211 returns to the initial position under the action of the return spring 212, the bending degree of the leaf spring 213 is reduced, and the stiffness of the joint is restored.

[0035] Through the cooperation of multiple return springs 212 and pneumatic tendons 221, a wide range of stiffness adjustment can be achieved to adapt to different application scenarios. The layout of the pneumatic tendons 221 facilitates air circulation and dissipates heat through compressed air convection, which helps keep the joints cool.

[0036] In some embodiments of the present application, the joint unit 1 further includes a fixed shaft and a sleeve 14 , wherein the fixed shaft is connected to a surface of the input disk 11 on one side facing the output disk 12 , and the sleeve 14 is sleeved on the outer side of the fixed shaft and connected to the return spring 212 .

[0037] The fixed shaft is connected to one side surface of the input disc 11, usually fixed by bolts, welding or other mechanical connection methods. The main function of the fixed shaft is to serve as the rotation center of the input disc 11. The sleeve 14 is sleeved on the outside of the fixed shaft. The sleeve 14 is connected to the return spring 212, usually by fixing one end of the return spring 212 on the sleeve 14 and the other end on the variable rigidity slider 211.

[0038] The arrangement of the fixed shaft and the shaft sleeve 14 provides additional support and guidance, which helps to maintain the stability and rotation accuracy of the joint. The shaft sleeve 14 can reduce the direct contact between the fixed shaft and the variable rigidity slider 211, reduce wear, and extend the service life of the joint.

[0039] In some embodiments of the present application, the joint unit 1 also includes an encoder 15, which includes a magnetic head and a magnetic disk. The magnetic head is arranged around the sleeve 14 and is connected to the input disk 11, and the magnetic disk is connected to the output disk 12, for detecting the deflection angle between the input disk 11 and the output disk 12.

[0040] When the input disk 11 rotates relative to the output disk 12, the magnetic head (usually a Hall sensor or other magnetic detection element) detects changes on the disk (a disk with magnetic marks). These changes are converted into electrical signals, so that the relative deflection angle between the input disk 11 and the output disk 12 can be calculated. The encoder 15 can accurately measure the deflection angle displacement of the joint by detecting the magnetic marks on the disk. This measurement is continuous and can monitor the movement state of the joint in real time.

[0041] The magnetic head of the encoder 15 is fixed to the input disk 11 through a bracket, and the magnetic disk is fixed to the inner surface of the output disk 12. The mounting opening reserved on the surface of the output disk 12 facilitates the installation and maintenance of the encoder 15.

[0042] The built-in high-precision absolute encoder 15 can provide accurate angular displacement measurement, which is essential for precise control and feedback of robot joints. The encoder 15 can monitor the deflection angle of the joint in real time and provide instant feedback to the control system, thereby improving the dynamic performance and accuracy of the robot. The absolute encoder 15 can provide position information immediately after the joint is restarted, without returning to the reference point, which improves the reliability of the system.

[0043] In some embodiments of the present application, the driving mechanism 22 further includes a booster and a one-way valve 214 , the booster is connected to the pneumatic muscle 221 via the one-way valve 214 , and the one-way valve 214 is connected to the shaft sleeve 14 .

[0044] The booster is connected to the pneumatic muscle 221 through the one-way valve 214, and is used to increase the air pressure in the pneumatic muscle 221. The one-way valve 214 ensures that the air pressure can only flow in one direction, that is, from the booster to the pneumatic muscle 221. The compressed air booster uses the compressed air in the factory for secondary boosting, and sends the boosted air into the pneumatic muscle 221 through the air supply valve (solenoid valve), while the pressure relief valve (solenoid valve) is used to control the pressure release in the pneumatic muscle 221 to ensure safety.

[0045] The micro one-way valve 214 is built into the joint sleeve 14 to ensure that the air pressure can only flow from the booster to the pneumatic tendon 221 to prevent the air pressure from flowing back. The joint interface only reserves a standard industrial compressed air interface, which allows the joint to be easily connected to the existing industrial compressed air system.

[0046] The specially made high-pressure resistant pneumatic muscle 221 and the booster device can provide higher output force and are suitable for applications requiring greater force. Through the booster device, even if the input pressure is low, sufficient output force can be obtained, which improves the adaptability and flexibility of the joint. The design of the one-way valve 214 and the pressure relief valve ensures the safety of the system and prevents the occurrence of air pressure backflow and overpressure. The booster device can efficiently utilize compressed air, improve energy utilization efficiency, and reduce energy consumption.

[0047] In some embodiments of the present application, an air inlet and an air outlet are respectively provided at both ends of the pneumatic tendon 221, and the air inlet is respectively connected to the air outlet and the boosting device.

[0048] The pneumatic muscle 221 has an air inlet and an air outlet at both ends. These holes allow the pneumatic muscle 221 to be connected end to end to form a closed air pressure circulation system. The air outlet of the pneumatic muscle 221 is connected to the air inlet through an air pipe. This connection is made at the central hole of the input disk 11, so that the air pressure can circulate in the pneumatic muscle 221.

[0049] An external stiffness adjustment mechanism, one end of which is connected to the power output end (such as an air pump) of the pneumatic muscle 221, and the other end is fixedly mounted on the side of the output disk 12 facing the input disk 11. The stiffness adjustment mechanism drives the pneumatic muscle 221 by controlling the air pressure, thereby adjusting the stiffness of the joint unit 1.

[0050] When the air pump inflates the pneumatic muscle 221, the pneumatic muscle 221 contracts, pushing the variable rigidity slider 211 to move, thereby changing the compression state of the return spring 212 to adjust the joint stiffness. Conversely, when the pneumatic muscle 221 is deflated, the return spring 212 pushes the variable rigidity slider 211 back to restore the joint stiffness.

[0051] The design of opening holes at both ends of the axial direction and connecting the air pipe end to end simplifies the air pressure circulation system, reduces the number of connecting parts, and reduces the complexity of the system. The external stiffness adjustment mechanism can respond quickly, realize real-time adjustment of the joint stiffness, and improve the dynamic performance of the robot. Fixing the stiffness adjustment mechanism on the side of the output disk 12 helps to maintain the compactness of the joint structure and is suitable for use in limited space.

[0052] In some embodiments of the present application, the variable rigidity mechanism 21 also includes a linear guide rail assembly 215, which is fixedly connected to the input disk 11 and slidably connected to the variable rigidity slider 211, and the extension direction of each linear guide rail assembly 215 is parallel to the extension direction of one of the return springs 212.

[0053] The input disk 11 is provided with a plurality of linear guide rail fixing grooves, and the linear guide rail assembly 215 is fixed to the input disk 11 through these fixing grooves, so as to ensure the stability of the guide rail and the accuracy of the joint.

[0054] The variable rigidity slider 211 can slide on the guide rail, ensuring that the variable rigidity slider 211 can accurately move along the linear track between the input disk 11 and the output disk 12. This helps to ensure that the movement of the variable rigidity slider 211 is uniform and stable during the rigidity adjustment process.

[0055] The linear guide assembly 215 provides precise guidance, ensuring the linear motion of the variable rigidity slider 211 when adjusting the rigidity, and improving the accuracy of the joint. The use of the linear guide reduces the shaking of the variable rigidity slider 211 during the movement, and increases the stability of the joint. Due to the parallel layout of the linear guide assembly 215 and the return spring 212, the rigidity adjustment is more uniform, which helps to improve the performance of the robot.

[0056] like Figure 4 As shown, in some embodiments of the present application, the variable rigidity mechanism 21 further includes a linear sensor 216 , and the linear sensor 216 is connected to the variable rigidity slider 211 .

[0057] The linear sensor 216 (a linear Hall sensor in this example) is connected to the variable rigidity slider 211 and generally detects the displacement of the slider through the relative position change between the magnet and the sensor.

[0058] When the variable rigidity slider 211 moves on the linear guide rail, the linear Hall sensor detects the displacement of the slider in real time.

[0059] The output signal of the linear sensor 216 is sent to the control system to form a closed-loop control with the expansion and contraction of the pneumatic muscle 221. The control system adjusts the air pressure of the pneumatic muscle 221 according to the feedback of the sensor, thereby accurately controlling the displacement of the variable rigidity slider 211 and the stiffness of the joint.

[0060] Through closed-loop control, precise adjustment of the variable stiffness robot joints can be achieved, improving the robot's motion accuracy and performance. The linear sensor 216 provides real-time displacement feedback, making the joint stiffness adjustment more rapid and accurate. The closed-loop control system can automatically compensate for errors caused by various factors (such as temperature changes, material fatigue, etc.), improving the reliability of the system. By accurately controlling the expansion and contraction of the pneumatic tendon 221, energy use can be optimized and unnecessary energy consumption can be reduced.

[0061] In some embodiments of the present application, the driving mechanism 22 further includes a pneumatic muscle connector 222 , and the pneumatic muscle connector 222 is respectively sleeved on the outer side of the end of the pneumatic muscle 221 and fixedly connected to the variable rigidity slider 211 .

[0062] The pneumatic muscle connector 222 is sleeved on the outer side of the end of the pneumatic muscle 221 and fixedly connected to the variable rigidity slider 211. This design is used to transmit the movement of the pneumatic muscle 221 to the variable rigidity slider 211.

[0063] The side of the variable rigidity slider 211 facing the output disk 12 is connected to the leaf spring 213, and moves in coordination through a plurality of rolling bearings. The leaf spring 213 is fixed to the leaf spring 213 fixing groove, and the leaf spring 213 fixing groove is fixedly connected to the inner wall of the joint housing. Such a structural design helps to maintain stable force transmission when the variable rigidity slider 211 moves.

[0064] The return spring 212 is fixedly mounted on the side of the input disk 11 facing the output disk 12, one end of which is connected to the side of the variable rigidity slider 211 facing the input disk 11, and the other end of which is connected to the shaft sleeve 14 of the input disk 11. The function of the return spring 212 is to provide a restoring force when the variable rigidity slider 211 moves to maintain the stability of the joint.

[0065] In some embodiments of the present application, the joint unit 1 further includes a cross roller bearing 13 , and the cross roller bearing 13 is connected to the input disk 11 and the output disk 12 respectively.

[0066] The cross roller bearing 13 is connected to the input disc 11 and the output disc 12, respectively, and is usually fixed to the input disc 11 and the output disc 12 by bolts. The cross roller bearing 13 acts as a transmission member, allowing high-precision and high-rigidity rotational movement between the input disc 11 and the output disc 12. The design of the cross roller bearing 13 allows the rollers to be arranged in a cross pattern, which can withstand loads from multiple directions while reducing friction and energy loss during rotation.

[0067] The cross roller bearing 13 has a compact structure and is suitable for applications that require high-precision transmission in a limited space. Using the cross roller bearing 13 as a transmission element not only reduces the energy loss of transmission, but also ensures high rigidity and high precision in a compact structure.

[0068] The power output end (air pump) provides energy to control the contraction and relaxation of the pneumatic muscle 221 through changes in air pressure.

[0069] The pneumatic muscle 221 is fixed on the variable rigidity slider 211 . When the air pressure increases, the pneumatic muscle 221 contracts, thereby pulling the variable rigidity slider 211 to overcome the resistance of the return spring 212 and move along the linear guide assembly 215 .

[0070] The variable rigidity slider 211 is connected to the leaf spring 213 and its fixing groove. The input torque of the input disk 11 contacts the leaf spring 213 through the arc surface of the fixing groove of the leaf spring 213 and is transmitted to the output disk 12.

[0071] The sliding stroke of the variable rigidity slider 211 changes the effective length of the blade spring 213 under stress. The blade spring 213 is similar to a cantilever beam structure. When the suspended end is stressed, it bends and deforms, resulting in a torsion angle between the input disk 11 and the output disk 12, making the joint flexible. When the effective length of the blade spring 213 changes, its bending deformation also changes, thereby changing the torsion angle between the input disk 11 and the output disk 12, and adjusting the joint stiffness.

[0072] After the pressurization is stopped, the atmospheric pressure discharges the excess gas through the connected air outlet, the pneumatic tendon 221 is completely shortened and reset under the pulling force of the reset spring 212, the variable rigidity slider 211 returns to the initial position, and the joint returns to the initial stiffness state.

[0073] By controlling the length change of the pneumatic muscle 221 through air pressure, the position of the variable-rigidity slider 211 on the leaf spring 213 is changed, thereby actively adjusting the effective length and stiffness of the leaf spring 213, so that the joint can actively adjust the stiffness according to different working requirements.

[0074] This embodiment controls the pneumatic tendon 221 by air pressure to drive the length of the pneumatic tendon 221, thereby changing the position of the variable rigidity slider 211 on the leaf spring 213 to change the effective length of the leaf spring 213, and then changing the rigidity of the leaf spring 213 to achieve active variable rigidity of the variable rigidity joint. Based on the axial double-opening design of the pneumatic tendon 221, the driving mechanism 22 is uniformly stressed as a whole, which can improve the smoothness and flexibility of the variable rigidity joint movement and ensure the safety of personnel in human-machine collaboration. At the same time, compared with the motor, the air pump as the input source can be driven by ordinary industrial compressed air and maintained by the one-way valve 214 without continuous energy supply. Low energy consumption, lightweight, reduced equipment damage, and reduced expenses.

[0075] A pneumatic tendon 221 is used as the driving mechanism 22, and an external air pump is used as the power source for stiffness adjustment, so that the variable stiffness joint is reduced as a whole, and both the radial and axial dimensions can be reduced to tens of millimeters. It has a compact structure, small size, light weight, and strong practicality, and can be applied to scenarios such as robotic arms and robots.

[0076] A crossed roller bearing 13 is used as a transmission member. The crossed roller bearing 13 can withstand large axial, radial and overturning moments, and can achieve a larger load-bearing capacity and rotational accuracy in a smaller space. The input disk 11 and the output disk 12 are connected by a crossed roller bearing 13, which can effectively utilize the space. At the same time, compared with the traditional shaft connection method, the connection method has less energy loss, improves the mechanical efficiency of the system, has a strong load-bearing capacity, a compact and stable structure, is easy to maintain and replace, has a wide range of application scenarios, and can ensure that the robot maintains a stable posture during high-speed movement and load operation.

[0077] The deflection angle can be accurately measured by the angle detection mechanism. After determining the material and effective length of the leaf spring 213, the stiffness K of the variable stiffness joint can be obtained, and the torque can be further obtained by calculation, which is equivalent to adding a one-dimensional torque sensor. For the torque control of the variable stiffness joint, it is not necessary to establish an accurate dynamic model of the variable stiffness joint and adopt impedance control, but torque feedback can be used. Only simple admittance control can achieve a similar force control effect, realize joint compliance, constant torque, drag teaching, etc., which not only improves the torque control accuracy, but also simplifies the control algorithm and reduces the complexity of the control system. In addition, the pressure relief valve is combined with the air supply valve and the displacement sensor to complete the precise variable stiffness closed-loop control.

[0078] Compared with the prior art, the technical solution provided by this application has the following beneficial technical effects: The present application designs a variable stiffness mechanism 21 and a driving mechanism 22 between the input disk 11 and the output disk 12, and the driving mechanism 22 drives the variable stiffness mechanism 21 to adjust the stiffness change of the joint unit 1. Among them, the use of pneumatic tendon 221 as the driving mechanism 22 can achieve lightweight structure and high power-to-weight ratio, allowing it to be flexibly arranged in a limited space. By using air pressure as the driving force, the inflation and deflation process of the pneumatic tendon 221 can achieve rapid response, high energy transmission efficiency, and can dissipate heat through compressed air convection, further simplifying the equipment.

[0079] Those skilled in the art will appreciate that the various operations, methods, steps, measures, and schemes in the processes discussed in this application may be alternated, modified, rearranged, decomposed, combined, or deleted.

[0080] The specific implementation methods of the present application described above do not constitute a limitation on the protection scope of the present application. Any other corresponding changes and modifications made according to the technical concept of the present application should be included in the protection scope of the claims of the present application.

Claims

1. A variable stiffness robot joint, characterized in that: include: The joint unit comprises an input disk and an output disk, wherein the input disk and the output disk are arranged opposite to each other to form a receiving cavity; An adjusting unit, comprising a plurality of rigidity-changing mechanisms and a plurality of driving mechanisms disposed in the accommodating cavity; The rigidity changing mechanism comprises a rigidity changing slider, a return spring and a leaf spring, one end of the rigidity changing slider is connected to the input disk through the return spring, and the other end of the rigidity changing slider is connected to the output disk through the leaf spring; The driving mechanism includes a pneumatic muscle, which is connected to the variable-rigidity slider and is used to drive the variable-rigidity slider to slide linearly to change the length of the return spring and the leaf spring.

2. The variable stiffness robot joint according to claim 1, characterized in that: At least three return springs are distributed along the circumference of the input disk, each return spring extends radially along the input disk, both sides of each variable-rigidity slider are respectively connected to two pneumatic muscles, and both ends of each pneumatic tendon are connected to two variable-rigidity sliders.

3. The variable stiffness robot joint according to claim 2, characterized in that: The joint unit further comprises a fixed shaft and a shaft sleeve, wherein the fixed shaft is connected to a surface of one side of the input disc facing the output disc, and the shaft sleeve is sleeved on the outer side of the fixed shaft and connected to the return spring.

4. The variable stiffness robot joint according to claim 3, characterized in that: The joint unit also includes an encoder, which includes a magnetic head and a magnetic disk. The magnetic head is arranged around the sleeve and connected to the input disk, and the magnetic disk is connected to the output disk for detecting a deflection angle between the input disk and the output disk.

5. The variable stiffness robot joint according to claim 3, characterized in that: The driving mechanism also includes a booster and a one-way valve. The booster is connected to the pneumatic muscle through the one-way valve, and the one-way valve is connected to the shaft sleeve.

6. The variable stiffness robot joint according to claim 5, characterized in that: An air inlet and an air outlet are respectively provided at two ends of the pneumatic muscle, and the air inlet is respectively connected to the air outlet and the boosting device.

7. The variable stiffness robot joint according to claim 1, characterized in that: The driving mechanism further comprises a pneumatic muscle connector, which is respectively sleeved on the outer side of the end of the pneumatic muscle and fixedly connected to the variable rigidity slider.

8. The variable stiffness robot joint according to claim 1, characterized in that: The joint unit further includes a cross roller bearing, and the cross roller bearing is respectively connected to the input disk and the output disk.

9. The variable stiffness robot joint according to claim 1, characterized in that: The variable rigidity mechanism also includes a linear guide assembly, which is fixedly connected to the input disk and slidably connected to the variable rigidity slider, and the extension direction of each linear guide assembly is parallel to the extension direction of one of the reset springs.

10. The variable stiffness robot joint according to claim 9, characterized in that: The variable rigidity mechanism further comprises a linear sensor, and the linear sensor is connected to the variable rigidity slider.

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