A variable stiffness robot joint

Abstract

The application 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 variable stiffness mechanisms and a plurality of driving mechanisms arranged in a containing cavity; the variable stiffness mechanism comprises a variable stiffness slider, a reset spring and a leaf spring, one end of the variable stiffness slider is connected with the input disc through the reset spring, and the other end of the variable stiffness slider 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 variable stiffness slider. The application drives the variable stiffness mechanism through the driving mechanism to adjust the stiffness change of the joint unit. The pneumatic tendon can realize lightweight structure and high power-to-weight ratio, and allows flexible layout in limited space. The inflation and deflation process of the pneumatic tendon can realize rapid response, the energy transmission efficiency is relatively high, the pneumatic tendon can dissipate heat through compressed air convection, and the equipment is further simplified.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of robots, and in particular to a variable stiffness robot joint. BACKGROUND

[0002] With the rapid development of robot technology, its application in the fields of industrial manufacturing, medical care, home service, etc. is increasingly widespread, and the complexity and safety requirements of human-machine collaborative scenarios have significantly improved.

[0003] Traditional robot safety strategies rely on rigid materials and high-energy consumption drive systems, which can guarantee basic stability but have the following technical bottlenecks: existing solutions often use high-power motors and redundant structures to achieve high bearing capacity, resulting in high system energy consumption, heavy weight, and difficult to control manufacturing costs. For example, industrial robot joints rely on rigid transmission, which can maintain accuracy but results in a sharp increase in energy consumption over time, limiting lightweight design. Although rigid structures can improve load capacity, they lack flexible buffering mechanisms and are prone to mechanical damage due to sudden impacts. Moreover, the degree of modularity is low, and maintenance requires the entire unit to be disassembled, resulting in low efficiency. Existing control algorithms lack the ability to integrate multi-sensor data, making it difficult to achieve high-precision dynamic adjustment, especially under variable load conditions, which can easily result in trajectory deviation.

[0004] In summary, existing robot technology has the technical problems of high energy consumption, high cost, complex structure, and low practicality. SUMMARY

[0005] The present application aims to overcome the above technical deficiencies and proposes a variable stiffness robot joint to solve the technical problems of high energy consumption, high cost, complex structure, and low practicality in existing technology.

[0006] To achieve the above technical purposes, the present application adopts the following technical solutions:

[0007] The present application provides a variable stiffness robot joint, comprising a joint unit and an adjustment unit.

[0008] The joint unit comprises an input disc and an output disc, which are arranged opposite to each other to form a containing cavity;

[0009] The adjustment unit comprises a plurality of variable stiffness mechanisms and a plurality of drive mechanisms arranged in the containing cavity;

[0010] The variable stiffness mechanism comprises a variable stiffness slider, a return spring, and a leaf spring, one end of the variable stiffness slider is connected to the input disc through the return spring, and the other end of the variable stiffness slider is connected to the output disc through the leaf spring;

[0011] The driving mechanism comprises pneumatic muscles connected with the variable stiffness sliders for driving the variable stiffness sliders to slide linearly to change the length of the reset springs and the leaf springs.

[0012] In some embodiments of the present application, at least three reset springs are distributed along the circumference of the input disc, each of the reset springs extends along the radial direction of the input disc, and two pneumatic muscles are connected with two sides of each variable stiffness slider respectively, and two variable stiffness sliders are connected with two ends of each pneumatic muscle.

[0013] In some embodiments of the present application, the joint unit further comprises a fixed shaft and a shaft sleeve, the fixed shaft is connected with the side surface of the input disc facing the output disc, and the shaft sleeve is sleeved outside the fixed shaft and connected with the reset spring.

[0014] In some embodiments of the present application, the joint unit further comprises an encoder, the encoder comprises a magnetic head and a magnetic disc, the magnetic head is arranged around the shaft sleeve and connected with the input disc, and the magnetic disc is connected with the output disc for detecting the deflection angle between the input disc and the output disc.

[0015] In some embodiments of the present application, the driving mechanism further comprises a pressure booster and a one-way valve, the pressure booster communicates with the pneumatic muscles through the one-way valve, and the one-way valve is connected with the shaft sleeve.

[0016] In some embodiments of the present application, the pneumatic muscles are respectively provided with an air inlet and an air outlet at two ends, and the air inlets communicate with the air outlets and the pressure booster respectively.

[0017] In some embodiments of the present application, the driving mechanism further comprises pneumatic muscle connectors, the pneumatic muscle connectors are respectively sleeved outside the end portions of the pneumatic muscles and fixedly connected with the variable stiffness sliders.

[0018] In some embodiments of the present application, the joint unit further comprises cross roller bearings, the cross roller bearings are respectively connected with the input disc and the output disc.

[0019] In some embodiments of the present application, the variable stiffness mechanism further comprises linear guide rail assemblies, the linear guide rail assemblies are respectively fixedly connected with the input disc and slidably connected with the variable stiffness sliders, and the extension directions of the linear guide rail assemblies are parallel to the extension directions of the reset springs.

[0020] In some embodiments of the present application, the variable stiffness mechanism further comprises a linear sensor, and the linear sensor is connected with the variable stiffness slider.

[0021] Compared with the prior art, the technical scheme provided by the application has the beneficial technical effects of:

[0022] The application adjusts the stiffness change of the joint unit by designing a variable stiffness mechanism and a driving mechanism between the input disc and the output disc, and the driving mechanism drives the variable stiffness mechanism to adjust the stiffness change of the joint unit. The pneumatic tendon is used as the driving mechanism, which can realize lightweight structure and high power-to-weight ratio, and allows flexible layout in limited space. The inflation and deflation process of the pneumatic tendon can realize fast response, and the energy transmission efficiency is high. The pneumatic tendon can dissipate heat through air convection, and further simplify the equipment. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical scheme in the application, the drawings needed in the embodiments will be briefly introduced as follows:

[0024] Figure 1 is a structural schematic diagram of a variable stiffness robot joint provided by the embodiment of the application;

[0025] Figure 2 is a structural schematic diagram of a joint unit provided by the embodiment of the application;

[0026] Figure 3 is a structural schematic diagram of an adjusting unit provided by the embodiment of the application;

[0027] Figure 4 is a partial schematic diagram of an adjusting unit provided by the embodiment of the application.

[0028] Reference signs:

[0029] Joint unit 1, adjusting unit 2;

[0030] Input disc 11, output disc 12, crossed roller bearing 13, shaft sleeve 14, encoder 15;

[0031] Variable stiffness mechanism 21, variable stiffness slider 211, return spring 212, leaf spring 213, one-way valve 214, linear guide rail assembly 215, linear sensor 216;

[0032] Driving mechanism 22, pneumatic tendon 221, pneumatic tendon connecting piece 222. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the application more clear and obvious, the application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application, and are not used to limit the application.

[0034] Those skilled in the art can understand that, in the specification, the word "comprising" is an open term, which means that the features described exist, but other features are not excluded. The terms "upper", "lower", "left", "right" and the like are based on the example directions shown in the drawings. The features limited by "first" and "second" implicitly include one or more of the features. The singular form is also used for the plural form. The meaning of "a plurality of" is two or more. The terms "mounting", "connecting", "connecting" can be fixed connection, detachable connection or integral connection; can be directly connected, or indirectly connected through an intermediate medium, or the communication between two elements. In addition, "connection" can include wireless connection.

[0035] The purpose of the present application is to overcome the above technical deficiencies, and to provide a variable stiffness robot joint, which solves the technical problems of high energy consumption, high cost, complex structure and low practicality in the prior art.

[0036] To achieve the above technical purpose, the present application adopts the following technical scheme:

[0037] As shown in Figure 1 and Figure 2 The present application provides a variable stiffness robot joint, which comprises a joint unit 1 and an adjusting unit 2.

[0038] The joint unit 1 comprises an input disc 11 and an output disc 12, and the input disc 11 and the output disc 12 are arranged oppositely to form a containing cavity; the joint unit 1 is a basic structural part of the robot joint, responsible for transmitting motion and force.

[0039] The adjusting unit 2 comprises a plurality of variable stiffness mechanisms 21 and a plurality of driving mechanisms 22 arranged in the containing cavity;

[0040] The variable stiffness mechanism 21 comprises a variable stiffness slider 211, a reset spring 212 and a leaf spring 213, one end of the variable stiffness slider 211 is connected with the input disc 11 through the reset spring 212, and the other end of the variable stiffness slider 211 is connected with the output disc 12 through the leaf spring 213;

[0041] The driving mechanism 22 comprises a pneumatic tendon 221, the pneumatic tendon 221 is connected with the variable stiffness slider 211, and is used for driving the variable stiffness slider 211 to slide linearly to change the length of the reset spring 212 and the leaf spring 213.

[0042] When the driving air pressure of the pneumatic tendon 221 is changed, the length of the pneumatic tendon 221 changes, driving the variable stiffness slider 211 to move, changing the length of the reset spring 212 and the leaf spring 213, so as to adjust the stiffness of the joint unit 1. The bending degree of the leaf spring 213 and the compression amount of the reset spring 212 determine the stiffness of the joint.

[0043] The application adjusts the stiffness change of the joint unit 1 by designing the stiffness changing mechanism 21 and the driving mechanism 22 between the input disc 11 and the output disc 12, and the driving mechanism 22 drives the stiffness changing mechanism 21 to adjust the stiffness change of the joint unit 1. The pneumatic tendon 221 is used as the driving mechanism 22, which can realize lightweight structure and high power-to-weight ratio, and allows flexible layout in limited space. The inflation and deflation process of the pneumatic tendon 221 can realize fast response by using air pressure as driving force, and the energy transmission efficiency is high, and the device can be further simplified by using compressed air convection cooling.

[0044] Compared with the traditional scheme using a motor as the driving power, the application uses the pneumatic tendon 221 as the driving component, which not only ensures the high response frequency of the driving power, but also avoids the technical problem of large weight and size of the device caused by using the motor as the driving power source.

[0045] As shown in Figure 3 In some embodiments of the application, at least three reset springs 212 are distributed along the circumference of the input disc 11, each reset spring 212 extends along the radial direction of the input disc 11, and each variable stiffness slider 211 is connected to two pneumatic tendons 221 on both sides, and both ends of each pneumatic tendon 221 are connected to two variable stiffness sliders 211.

[0046] In this embodiment, three reset springs 212 and three pneumatic tendons 221 are taken as an example, and in fact, the number of reset springs 212 and pneumatic tendons 221 can be four or more in other embodiments.

[0047] The three reset springs 212 are connected to the center of the input disc 11 and extend outward. An equal included angle is formed between any two adjacent reset springs 212. Such a layout can ensure that the stiffness change in each direction during rotation of the joint is uniform.

[0048] The three pneumatic tendons 221 are fixedly installed in the accommodating cavity in a triangular shape and are fixedly connected to the variable stiffness sliders 211, thereby being indirectly connected to the reset springs 212. This connection mode forms a stable network structure, which can improve the stability of the structure and ensure uniform transmission of force.

[0049] When it is necessary to increase the stiffness of the joint, the pneumatic tendon 221 is contracted by changing the air pressure, thereby pushing the variable stiffness slider 211 to move towards the center of the input disc 11, compressing the length of the reset spring 212, and increasing the bending degree of the leaf spring 213, the joint stiffness is reduced, and the flexibility is increased.

[0050] When it is necessary to reduce the joint stiffness, the pneumatic tendon 221 is relaxed by reversing the air pressure, the rigid slider 211 returns to the initial position under the action of the reset spring 212, the bending degree of the leaf spring 213 is reduced, and the joint stiffness is restored.

[0051] Through the cooperation of multiple reset 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 tendon 221 helps air circulation, and the convection heat dissipation by compressed air helps to maintain the cooling of the joint.

[0052] In some embodiments of the present application, the joint unit 1 further comprises a fixed shaft and a shaft sleeve 14, the fixed shaft is connected to one side surface of the input disc 11 towards the output disc 12, and the shaft sleeve 14 is sleeved on the outside of the fixed shaft and connected with the reset spring 212.

[0053] 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 shaft sleeve 14 is sleeved on the outside of the fixed shaft. The shaft sleeve 14 is connected with the reset spring 212, usually by fixing one end of the reset spring 212 on the shaft sleeve 14 and the other end on the rigid slider 211.

[0054] The fixed shaft and the shaft sleeve 14 provide 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 rigid slider 211, reduce wear and tear, and prolong the service life of the joint.

[0055] In some embodiments of the present application, the joint unit 1 further comprises an encoder 15, the encoder 15 comprises a magnetic head and a magnetic disc, the magnetic head is arranged around the shaft sleeve 14 and connected with the input disc 11, and the magnetic disc is connected with the output disc 12 for detecting the deflection angle between the input disc 11 and the output disc 12.

[0056] When the input disc 11 rotates relative to the output disc 12, the magnetic head (usually a Hall sensor or other magnetic detection element) detects the changes on the magnetic disc (a disc with magnetic markers). These changes are converted into electrical signals, so that the relative deflection angle between the input disc 11 and the output disc 12 can be calculated. The encoder 15 can accurately measure the deflection angle displacement of the joint by detecting the magnetic markers on the magnetic disc. This measurement is continuous and can monitor the motion state of the joint in real time.

[0057] The magnetic head of the encoder 15 is fixed to the input disc 11 by a bracket, and the magnetic disc is fixed to the inner surface of the output disc 12. The mounting port reserved on the surface of the output disc 12 facilitates the installation and maintenance of the encoder 15.

[0058] The built-in high-precision absolute value encoder 15 can provide accurate angular displacement measurement, which is crucial for the precise control and feedback of the robot joint. The encoder 15 can monitor the deflection angle of the joint in real time, providing instant feedback to the control system, thereby improving the dynamic performance and precision of the robot. The absolute value 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.

[0059] In some embodiments of the present application, the driving mechanism 22 further comprises a booster device and a one-way valve 214, the booster device being in communication with the pneumatic tendon 221 through the one-way valve 214, and the one-way valve 214 being connected with the shaft sleeve 14.

[0060] The booster device is in communication with the pneumatic tendon 221 through the one-way valve 214, which is used to increase the air pressure in the pneumatic tendon 221. The one-way valve 214 ensures that the air pressure can only flow in one direction, i.e. from the booster device to the pneumatic tendon 221. The compressed air booster uses the compressed air in the factory for secondary boosting, and the boosted air is sent into the pneumatic tendon 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 tendon 221 to ensure safety.

[0061] The miniature one-way valve 214 is built into the joint shaft sleeve 14, which ensures that the air pressure can only flow from the booster device to the pneumatic tendon 221, preventing backflow of air pressure. The joint interface only reserves a standard industrial compressed air interface, which makes the joint can be easily connected to the existing industrial compressed air system.

[0062] The specially designed high-pressure-resistant pneumatic tendon 221 and booster device can provide higher output force, which is suitable for applications that require larger force. Through the booster device, sufficient output force can be obtained even if the input pressure is low, 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, preventing backflow of air pressure and overpressure. The booster device can efficiently utilize compressed air, improving energy utilization efficiency and reducing energy consumption.

[0063] In some embodiments of the present application, the pneumatic tendon 221 has an air inlet and an air outlet at both ends, respectively, and the air inlet is in communication with the air outlet and the booster device, respectively.

[0064] The pneumatic tendon 221 has an air inlet and an air outlet at both ends, respectively, and these holes make the pneumatic tendon 221 can be connected end to end, forming a closed air pressure circulation system. The air outlet of the pneumatic tendon 221 is connected to the air inlet through an air pipe, and this connection is made at the center hole of the input disc 11, so that the air pressure can circulate in the pneumatic tendon 221.

[0065] The external stiffness adjusting mechanism is connected to the power output end (e.g. air pump) of the pneumatic muscle 221 at one end and fixedly installed on the side of the output disc 12 facing the input disc 11 at the other end. The stiffness adjusting mechanism drives the pneumatic muscle 221 by controlling air pressure, thereby adjusting the stiffness of the joint unit 1.

[0066] When the air pump inflates the pneumatic muscle 221, the pneumatic muscle 221 contracts and pushes the stiffness-changing slider 211 to move, thereby changing the compression state of the return spring 212 and achieving adjustment of the joint stiffness. Conversely, when the pneumatic muscle 221 deflates, the return spring 212 pushes the stiffness-changing slider 211 back to restore the joint stiffness.

[0067] Through the design of axial holes at both ends and the connection of the air pipes end to end, the air pressure circulation system is simplified, the number of connecting components is reduced, and the complexity of the system is reduced. The external stiffness adjusting mechanism can quickly respond to achieve real-time adjustment of the joint stiffness, thereby improving the dynamic performance of the robot. Fixing the stiffness adjusting mechanism on the side of the output disc 12 helps to maintain the compactness of the joint structure and is suitable for use in limited space.

[0068] In some embodiments of the present application, the stiffness-changing mechanism 21 further comprises linear guide rail assemblies 215, which are respectively fixedly connected to the input disc 11 and slidingly connected to the stiffness-changing slider 211. The extension direction of each linear guide rail assembly 215 is parallel to the extension direction of one return spring 212.

[0069] The input disc 11 is provided with a plurality of linear guide rail fixing grooves, and the linear guide rail assemblies 215 are fixed on the input disc 11 through the fixing grooves, thereby ensuring the stability of the guide rails and the accuracy of the joint.

[0070] The stiffness-changing slider 211 can slide on the guide rails, ensuring that the stiffness-changing slider 211 can move accurately along the linear track between the input disc 11 and the output disc 12. This helps to ensure that the movement of the stiffness-changing slider 211 is uniform and stable during stiffness adjustment.

[0071] The linear guide rail assemblies 215 provide precise guidance, ensuring the linear movement of the stiffness-changing slider 211 during stiffness adjustment and improving the accuracy of the joint. The use of linear guide rails reduces the shaking of the stiffness-changing slider 211 during movement, increasing the stability of the joint. Due to the parallel layout of the linear guide rail assemblies 215 and the return springs 212, stiffness adjustment is more uniform, which helps to improve the performance of the robot.

[0072] As shown in FIG. 1, Figure 4 In some embodiments of the present application, the stiffness-changing mechanism 21 further comprises a linear sensor 216 connected to the stiffness-changing slider 211.

[0073] 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 by changing the relative position of the magnet and the sensor.

[0074] 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.

[0075] The output signal of the linear sensor 216 is fed into the control system, forming 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 based on the sensor feedback, thereby precisely controlling the displacement of the variable-rigidity slider 211 and the stiffness of the joint.

[0076] Closed-loop control enables precise adjustment of variable-stiffness robot joints, improving the robot's motion accuracy and performance. Linear sensor 216 provides real-time displacement feedback, enabling faster and more accurate joint stiffness adjustment. The closed-loop control system automatically compensates for errors caused by various factors (such as temperature fluctuations and material fatigue), improving system reliability. Precisely controlling the expansion and contraction of pneumatic muscle 221 optimizes energy usage and reduces unnecessary energy consumption.

[0077] In some embodiments of the present application, the driving mechanism 22 further includes a pneumatic tendon connector 222 , which is respectively sleeved on the outer side of the end of the pneumatic tendon 221 and fixedly connected to the variable-rigidity slider 211 .

[0078] 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.

[0079] The side of the variable-rigidity slider 211 facing the output disk 12 is connected to a leaf spring 213, which moves in conjunction with the blade spring 213 via multiple rolling bearings. The leaf spring 213 is secured to a retaining groove in the leaf spring 213, which in turn is fixedly connected to the inner wall of the joint housing. This structural design helps maintain stable force transmission as the variable-rigidity slider 211 moves.

[0080] A return spring 212 is fixedly mounted on the side of the input disc 11 facing the output disc 12. One end is connected to the side of the variable rigidity slider 211 facing the input disc 11, and the other end is connected to the sleeve 14 of the input disc 11. The function of the return spring 212 is to provide a restoring force when the variable rigidity slider 211 moves, thereby maintaining the stability of the joint.

[0081] 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.

[0082] The cross roller bearing 13 is connected to the input disc 11 and the output disc 12, usually by bolts. The cross roller bearing 13 acts as a transmission element, allowing high precision and high stiffness rotational movement between the input disc 11 and the output disc 12. The cross roller bearing 13 is designed so that the rollers are arranged in a cross pattern, allowing load to be taken from multiple directions while reducing friction and energy loss during rotation.

[0083] The cross roller bearing 13 is compact in structure, suitable for applications requiring high precision transmission in a limited space. Using the cross roller bearing 13 as a transmission element reduces energy loss during transmission, while ensuring high stiffness and precision in a compact structure.

[0084] The power output (air pump) provides energy to control the contraction and relaxation of the pneumatic tendon 221 through changes in air pressure.

[0085] The pneumatic tendon 221 is fixed to the variable stiffness slider 211. When the air pressure increases, the pneumatic tendon 221 contracts, pulling the variable stiffness slider 211 to overcome the resistance of the return spring 212 and move along the linear guide assembly 215.

[0086] The variable stiffness slider 211 is connected to the leaf spring 213 and its fixed slot. The input torque of the input disc 11 is transmitted to the output disc 12 through the contact between the arc surface of the leaf spring 213 fixed slot and the leaf spring 213.

[0087] The sliding stroke of the variable stiffness slider 211 changes the effective length of the leaf spring 213. The leaf spring 213 is similar to a cantilever beam structure, and when the free end is subjected to force, it will bend and deform, causing the input disc 11 and the output disc 12 to produce a torsional angle, making the joint flexible. When the effective length of the leaf spring 213 changes, the amount of bending and deformation also changes, thereby changing the torsional angle between the input disc 11 and the output disc 12, achieving adjustment of the joint stiffness.

[0088] After stopping the pressurization, the atmospheric pressure expels the excess gas through the connected air outlet hole, and the pneumatic tendon 221 is fully shortened under the tension of the return spring 212, returning the variable stiffness slider 211 to the initial position, and the joint returns to the initial stiffness state.

[0089] By controlling the length change of the pneumatic tendon 221 through air pressure, the position change of the variable stiffness slider 211 on the leaf spring 213 is achieved, thereby actively adjusting the effective length and stiffness of the leaf spring 213, allowing the joint to actively adjust the stiffness according to different working requirements.

[0090] The embodiment changes the position of the variable stiffness slider 211 on the leaf spring 213 by controlling the air pressure of the pneumatic tendon 221 to drive the length change of the pneumatic tendon 221, thereby changing the effective length of the leaf spring 213, and further changing the stiffness of the leaf spring 213, to realize active variable stiffness of the variable stiffness joint. Based on the axial double-opening design of the pneumatic tendon 221, the overall driving mechanism 22 is uniformly stressed, which can improve the smoothness and flexibility of the variable stiffness joint movement, ensure the safety of personnel in human-machine cooperation, and compared with a motor, the ordinary industrial compressed air can drive the air pump as the power source for stiffness adjustment, and the air pump is maintained by the one-way valve 214 without the need for continuous energy supply. Low energy consumption, light weight, reduce the damage of equipment, reduce the expenditure.

[0091] The pneumatic tendon 221 is used as the driving mechanism 22, and the air pump is externally connected as the power source for stiffness adjustment, so that the overall variable stiffness joint is reduced, and the radial size and the axial size can be reduced to tens of millimeters, the structure is compact, the volume is small, the weight is light, the practicality is strong, and the variable stiffness joint can be applied to scenes such as mechanical arms and robots.

[0092] The crossed roller bearing 13 is used as a transmission part, the crossed roller bearing 13 can bear a large axial force, a large radial force and a large overturning moment, can realize a large bearing capacity and a high rotation accuracy in a small space, and the input disc 11 and the output disc 12 are connected by the crossed roller bearing 13, so that the space can be effectively utilized. Compared with the traditional shaft connection mode, the connection mode has small energy loss, improves the mechanical efficiency of the system, has high bearing capacity, compact and stable structure, is convenient to maintain and replace, has wide application scenarios, and can ensure that the robot maintains a stable posture during high-speed movement and load operation.

[0093] The angle detection mechanism can accurately measure the deflection angle, the stiffness K of the variable stiffness joint can be obtained after the material and the effective length of the leaf spring 213 are determined, and the torque can be further calculated, which is equivalent to adding a one-dimensional torque sensor. For torque control of the variable stiffness joint, impedance control does not need to be established, but torque feedback can be used, and similar force control effects can be achieved by using only simple admittance control, to realize joint compliance, constant torque, drag teaching and the like, which not only improves the torque control precision, but also simplifies the control algorithm and reduces the complexity of the control system. In addition, the pressure relief valve, the air supply valve and the displacement sensor are cooperated to complete the precise variable stiffness closed-loop control.

[0094] Compared with the prior art, the technical scheme provided by the application has the beneficial technical effects including:

[0095] The application designs a rigidity changing mechanism 21 and a driving mechanism 22 between the input disc 11 and the output disc 12, and the driving mechanism 22 drives the rigidity changing mechanism 21 to adjust the rigidity change of the joint unit 1. The pneumatic tendon 221 is used as the driving mechanism 22, which can realize lightweight structure and high power-to-weight ratio, and allows flexible layout in limited space. Through air pressure as driving force, the inflation and deflation process of the pneumatic tendon 221 can realize fast response, high energy transmission efficiency, and further simplify the equipment through compressed air convection cooling.

[0096] Those skilled in the art can understand that the steps, measures and schemes in the various operations, methods and processes discussed in the application can be alternated, changed, rearranged, decomposed, combined or deleted.

[0097] The specific embodiments of the application described above do not constitute a limitation on the protection scope of the application. Any various other corresponding changes and modifications made according to the technical concept of the application should be included in the protection scope of the claims of the 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 variable rigidity mechanism includes a variable rigidity slider, a return spring and a leaf spring, one end of the variable rigidity slider is connected to the input disk via the return spring, and the other end of the variable rigidity slider is connected to the output disk via the leaf spring; The driving mechanism includes a pneumatic muscle connected to the variable-rigidity slider and 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 disc, each return spring extends radially along the input disc, both sides of each variable-rigidity slider are respectively connected to two pneumatic tendons, 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 includes a fixed shaft and a shaft sleeve. The fixed shaft is connected to a surface of the input disc facing the output disc. The shaft sleeve is sleeved on the outside 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 further 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.

5. The variable stiffness robot joint according to claim 3, characterized in that: 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.

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

7. The variable stiffness robot joint according to claim 1, characterized in that: The driving mechanism further includes a pneumatic tendon connector, which is respectively sleeved on the outer side of the end portion of the pneumatic tendon 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 connected to the input disk and the output disk respectively.

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

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

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