Dynamic lower limb prosthesis knee joint with variable rigidity

Abstract

The invention relates to a rigidity-variable dynamic lower limb prosthesis knee joint which comprises a knee joint connecting piece, a knee joint driving part, a rigidity-variable mechanism part, a fixing plate and a rope driving system. The knee joint connecting piece comprises a knee joint standard connecting piece upper part, a knee joint upper connecting piece left part, a knee joint standard connecting piece lower part and a knee joint upper connecting piece right part; the fixing plate comprises a knee joint fixing plate left part and a knee joint fixing plate right part; the knee joint driving part comprises a knee joint large motor, a knee joint small motor, a synchronous belt, a transmission shaft, a knee joint large belt wheel and a knee joint small belt wheel, the variable stiffness mechanism part comprises a rectangular spring, two sliding blocks, a pulley, a guide rail and a spring baffle, and the rope driving system part comprises a spring upward-pressing driving rope, a spring downward-pressing driving rope and a variable stiffness swing rod; according to the invention, double motors are adopted for driving, a lower reduction ratio is adopted, and a synchronous belt is adopted for transmission. The device has the advantages of compact structure, good reverse driving performance, low driving noise and the like.

Description

Technical Field

[0001] The invention relates to a powered lower limb prosthetic knee joint with variable stiffness. Background Art

[0002] According to 2012 statistics from the China Disabled Persons' Federation, there are currently approximately 24.72 million people with limb disabilities in China, 11.4% of whom require prosthetic limbs, and 80% of whom are lower limb amputees. Limb loss creates significant inconvenience in the lives and work of these individuals, severely impacting their quality of life. With advances in science and technology, prosthetic knee joints for lower limb amputees are gradually evolving from passive to active joints. These powered prosthetic knee joints can provide power for walking, improving amputees' walking comfort and adapting to a wider range of walking scenarios.

[0003] At present, there are still some deficiencies in the design and function of powered lower limb prosthetic knee joints, and it is difficult to strike a balance between sufficient power, light weight, and comfortable wearing. Because the human body requires different joint torques when walking in different scenarios. In order to meet the daily walking needs of amputees, existing powered knee prostheses usually use a single high-torque motor so that its peak torque meets the torque required for going up and down stairs. This results in a larger joint size and poor anti-drive performance of the overall joint. At the same time, the use of a larger reduction ratio will not only bring about greater motion noise, but also increase the overall complexity and quality of the mechanism, reducing the wearing comfort of the prosthesis wearer. Summary of the Invention

[0004] The purpose of the present invention is to provide a powered lower limb prosthetic knee joint with variable stiffness to compensate for the existing powered lower limb prosthetic knee joint. Due to the need to meet the daily walking needs of amputees, a single high-torque motor is usually used to meet the scenarios with high joint torque requirements such as going up and down stairs. The related powered lower limb prosthetic knee joints are usually large in size, have a high deceleration ratio, poor backdrive performance, and high overall joint quality.

[0005] The purpose of the present invention is to provide a powered lower limb prosthetic knee joint with variable stiffness. The powered lower limb prosthetic knee joint adopts a modular design and can be customized for patients with prosthetic limbs. The powered lower limb prosthetic knee joint can provide sufficient power for human walking at the knee joint. At the same time, the powered lower limb prosthetic knee joint is driven by two motors, one large and one small. Different power outputs are performed for different walking scenarios. The use of a lower reduction ratio and a speed reduction belt transmission effectively improves the anti-drive performance of the joint and reduces its movement noise. At the same time, it has a compact structure, light weight, small size, long battery life, and low power consumption.

[0006] The present invention proposes a variable stiffness powered prosthetic knee joint for lower limbs, comprising a knee joint connector, a knee joint drive portion, a variable stiffness mechanism portion, a fixing plate, and a rope drive system; wherein: The knee joint connector includes an upper standard knee joint connector, a left upper knee joint connector, a lower standard knee joint connector, and a right upper knee joint connector. The left upper knee joint connector and the right upper knee joint connector are connected by a bearing. The tops of the left upper knee joint connector and the right upper knee joint connector are respectively fixedly connected to the upper standard knee joint connector by bolts. The lower standard knee joint connector is fixed to the right bottom of the knee joint fixation plate of the fixation plate. The fixation plate includes a left knee joint fixation plate and a right knee joint fixation plate; the left knee joint fixation plate and the right knee joint fixation plate respectively pass through bearings connected to the left knee joint upper connector and the right knee joint upper connector; The knee joint driving part includes a large knee joint motor, a small knee joint motor, a synchronous belt, a transmission shaft, a large knee joint pulley and a small knee joint pulley, the large knee joint pulley passes through the bearings of the left and right upper knee joint connecting parts, and the large knee joint pulley can rotate relative to the left and right upper knee joint connecting parts; the left and right knee joint fixing plates are located on both sides of the large knee joint pulley, and the large knee joint pulleys are fixedly connected to the left and right knee joint fixing plates respectively, so that the large knee joint pulley can drive the left and right knee joint fixing plates to rotate; the large knee joint motor is fixed to the upper right knee joint fixing plate by bolts, the small knee joint motor is fixed to the upper left knee joint fixing plate by bolts, the transmission shaft is fixedly connected to the rotating shaft of the large knee joint motor, the small knee joint pulley is sleeved on the transmission shaft and fixedly connected to the transmission shaft. When the rotating shaft of the large knee joint motor rotates, it can drive the small knee joint pulley to rotate; the small knee joint pulley and the large knee joint pulley are connected by a synchronous belt for power transmission; The variable stiffness mechanism includes a rectangular spring, a slider, a pulley, a guide rail, and a spring baffle. There are two sliders. The rectangular spring is sleeved outside the guide rail, with its top fixedly connected to the spring baffle and its bottom fixedly connected to the bottom of the spring baffle. The upper and lower parts of the spring baffle are respectively fixedly connected to the corresponding sliders. Both sliders are placed on the guide rail so that they can move linearly on the guide rail, and the spring baffle can only move downward. The guide rail is fixed to the upper right side of the knee joint fixation plate by bolts. The rope drive system includes a spring-loaded driving rope, a spring-loaded driving rope and a variable-stiffness pendulum; one end of the variable-stiffness pendulum is fixed to the upper right side of the knee joint fixation plate through a rotating shaft, one end of the spring-loaded driving rope is fixedly connected to the large pulley of the knee joint, the spring-loaded driving rope is wound around the pulley of the variable-stiffness pendulum, and the other end is fixedly connected to the bottom of the spring baffle; one end of the spring-loaded driving rope is fixedly connected to the coil disk and wound around the coil disk, and the other end of the spring-loaded driving rope passes through the pulley and is fixedly connected to the spring baffle. When the coil disk rotates counterclockwise, the spring baffle is driven to move downward along the guide rail through the spring-loaded driving rope; the small motor of the knee joint is located inside the coil disk, and the rotating shaft of the small motor of the knee joint is fixedly connected to the coil disk; When the spring baffle moves downward, power will be transmitted through the spring upward pressure drive rope, and the variable stiffness pendulum will quickly swing to the extreme position. The angle range of the variable stiffness pendulum satisfies the downward movement of the spring baffle to the extreme position; when the variable stiffness pendulum swings to the maximum angle, the large motor of the knee joint continues to complete the flexion action, and it will drive the spring baffle down through the spring upward pressure drive rope, and move the slider up along the guide rail to compress the rectangular spring; at the same time, the small motor of the knee joint continues to rotate counterclockwise, and continues to drive the spring baffle to move downward along the guide rail through the slider through the spring downward pressure drive rope, thereby compressing the rectangular spring; energy storage is achieved through the joint compression of the rectangular spring on and under the spring baffle, and then extension is performed.

[0007] In the present invention, in order to achieve customization according to individual differences of amputees and different purposes of use, the powered lower limb prosthetic knee joint is connected with a prosthetic standard joint to facilitate customized replacement.

[0008] When an amputee wears the prosthesis of the present invention and walks, the normal working process of the prosthesis is as follows: First, the powered lower-limb prosthetic knee joint is primarily used to achieve joint flexion and extension. Counterclockwise rotation of the large knee motor 8 achieves flexion, and clockwise rotation achieves extension. Its range of motion is 0-120 degrees, with a maximum flexion angle of 120 degrees. Furthermore, the powered lower-limb prosthetic knee joint often requires greater torque during the extension phase to support standing and walking. The following details the workflow of the powered lower-limb prosthetic knee joint in different scenarios, primarily categorized as low-torque demand and high-torque demand.

[0009] When the knee joint is bent, the transmission shaft 13 fixed on the large motor 8 of the knee joint drives the small pulley 14 of the knee joint to rotate in the same direction. At this time, the large pulley 9 of the knee joint connected to the small pulley 14 of the knee joint through the synchronous belt 12 also rotates in the same direction. The large pulley 9 of the knee joint can generate relative rotation with the left and right connectors 2 and 6 of the knee joint. Therefore, the rotation of the transmission shaft 13 on the large motor 8 of the knee joint will eventually drive the left and right knee joint fixation plates 3 and 7 to rotate around the central axis of the left and right connectors 2 and 6 of the knee joint. The rotation of the large pulley 9 of the knee joint will drive the movement of the spring-pressed drive rope 10. When the knee joint gradually bends, the spring The spring-loaded drive rope 10 will first drive the variable stiffness pendulum 28 to swing upward, increasing its angle with the horizontal axis; in the process of the variable stiffness pendulum 23 swinging upward, the rectangular spring 21 will not be compressed. Therefore, when the variable stiffness pendulum 23 has not reached the maximum swing angle, the overall stiffness of the knee joint can be considered to be zero; at the same time, the maximum swing angle of the variable stiffness pendulum 23 meets the maximum angle of the knee joint during daily walking on flat ground; that is, when walking on flat ground, the power is mainly provided by the large motor 8 of the knee joint, and the rectangular spring is almost not compressed; when the knee joint is extended, that is, the large motor 8 of the knee joint moves clockwise, the variable stiffness pendulum 23 will swing downward under power transmission until the minimum angle, that is, the knee joint angle is 0 degrees; the variable stiffness pendulum 23 swings downward mainly according to the torsion spring installed inside. The variable stiffness pendulum 23 swings upward and twists the torsion spring. When the large motor 8 of the knee joint moves clockwise, the variable stiffness pendulum 23 is released, and the torsion spring drives the variable stiffness pendulum 23 to swing downward.

[0010] For scenarios where the joint torque requirement is large, such as going up and down stairs. At this time, the large knee joint motor 8 and the small knee joint motor 4 are required to work together; when the large knee joint pulley 9 rotates counterclockwise, the spring-loaded drive rope 10 fixed to the large knee joint pulley 9 will drive the variable stiffness rocker 23 to swing upward; at the same time, a large torque is required to achieve knee joint extension for going up stairs, and the required joint torque is greater than the peak torque of the knee joint motor 8. At this time, the small knee joint motor 4 will start working; the small knee joint motor 4 and the large knee joint motor 8 rotate counterclockwise together to achieve knee joint flexion, and complete energy storage through the compression of the rectangular spring 21; and the energy release of the rectangular spring 21 is realized in the extension stage to make up for the gap between the torque required for joint extension and the peak torque of the joint motor.

[0011] Specifically, during the extension phase, the rotating shaft of the knee joint small motor 4 drives the coil disk 15 fixed to it to rotate counterclockwise. The counterclockwise rotation of the coil disk 15 will drive the spring baffle 22 to move downward along the guide rail 17 through the spring downward pressure drive rope 16. The spring baffle 22 is fixedly connected to a slider 19, allowing it to move linearly on the guide rail 17, while the spring baffle 22 can only move downward. The downward movement of the spring baffle 22 will drive the rectangular spring 21 downward. The top of the rectangular spring 21 is fixedly connected to the spring baffle 22, and the bottom of the rectangular spring 21 is fixedly connected to the spring baffle 20. Therefore, the downward movement of the spring baffle 22 will bring the rectangular spring 21 and the spring baffle 20 downward together. At the same time, the end of the spring upward pressure drive rope 10 is fixedly connected to the spring baffle 20. The downward movement of the lower spring baffle 20 also transmits power through the spring upward pressure drive rope 10, quickly swinging the variable stiffness swing rod 23 to its limit position. The angle range 11 of the variable stiffness swing rod 23 satisfies the downward movement of the lower spring baffle 20 to its limit position. When the variable stiffness swing rod 23 swings to its maximum angle, the large knee joint motor 8 continues to complete the flexion movement, which drives the lower spring baffle 20 to move upward along the guide rail 17 through the spring upward pressure drive rope 10 to compress the rectangular spring 21. At the same time, the small knee joint motor 4 continues to rotate counterclockwise, and the spring downward pressure drive rope 16 continues to drive the upper spring baffle 22 to move downward along the guide rail 17, resulting in compression of the rectangular spring 21. Energy storage is achieved through the joint compression of the rectangular spring 21 by the spring baffle 22 and the lower spring baffle 20. Then, the extension movement is performed, and the energy of the rectangular spring 21 is released, causing the lower spring baffle 20 to move downward, thereby driving the spring downward pressure drive rope 16 fixed to the lower spring baffle 20 to move downward, thereby driving the large knee joint pulley 9 fixed to the spring downward pressure drive rope 16 to rotate clockwise, assisting the knee joint in achieving extension movement. It should be emphasized here that when the variable stiffness mechanism movement range 24 is greater than the variable stiffness swing rod 23 swinging to the maximum angle, the rectangular spring moves to the lowest position when uncompressed. This means that within the knee joint flexion joint angle range, it can compress the rectangular spring 21 at any angle, and at the same time, the knee joint small motor 15 can compress the rectangular spring 21, thereby adjusting the overall stiffness of the knee joint. This achieves variable stiffness of the entire joint. At the same time, based on the variable stiffness, the torque of the knee joint small motor 15 can be transmitted to the large knee joint pulley through the rectangular spring 21, thereby achieving flexion and extension of the knee joint together with the large knee joint motor 8.

[0012] The beneficial effects of the present invention are: (1) The powered lower limb prosthetic knee joint of the present invention is driven by a motor, which can provide sufficient driving force for normal walking in the powered lower limb prosthetic knee joint, thereby reducing the energy consumed by the patient walking on level ground and the output torque of the hip joint on the side where the prosthesis is installed. Therefore, amputees wearing the powered ankle joint of the present invention can achieve a normal walking gait, making it possible to walk normally for long periods of time or complete basic daily movements such as climbing and descending stairs and squatting and standing up.

[0013] (2) The powered lower limb prosthetic knee joint is driven by dual motors, adopts a low reduction ratio, and uses a synchronous belt drive. It has the advantages of compact structure, good reverse drive performance, and low drive noise.

[0014] (3) The powered lower limb prosthetic knee joint is designed with an elastic energy storage system of parallel springs. At the same time, the small motor of the knee joint can not only adjust the stiffness of the parallel spring, but also realize the coordinated drive with the large motor of the knee joint through the parallel spring. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The present invention is a general view of the knee joint, wherein: (A) is a triaxial view of the knee joint, and (B) is a front view of the knee joint.

[0016] Figure 2 It is an internal front view of the knee joint of the present invention.

[0017] Figure 3 Diagram of the key power transmission parts of the knee joint of the present invention.

[0018] Markings in the figure: 1. Upper standard connector of knee joint, 2. Left upper connector of knee joint, 3. Left fixation plate of knee joint, 4. Small motor of knee joint, 5. Lower standard connector of knee joint, 6. Right upper connector of knee joint, 7. Right fixation plate of knee joint, 8. Large motor of knee joint, 9. Large pulley of knee joint, 10. Spring pressure drive rope, 11. Angle range of variable stiffness rocker arm, 12. Synchronous belt, 13. Drive shaft, 14. Small pulley of knee joint, 15. Coil disk, 16. Spring pressure drive rope, 17. Guide rail, 18. Pulley, 19. Slider, 20. Lower spring baffle, 21. Rectangular spring, 22. On spring baffle, 23. Variable stiffness rocker arm, 24. Moving range of variable stiffness mechanism. DETAILED DESCRIPTION

[0019] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0020] Example 1: The powered lower limb prosthetic knee joint of the present invention comprises a knee joint connector, a knee joint drive portion, a variable stiffness mechanism portion, a fixing plate, and a rope drive system. The knee joint connector portion comprises two upper and lower standard connectors, which are respectively used to connect to the receiving cavity and ankle joint of the residual limb. The knee joint drive portion comprises a large motor, a small motor, a synchronous belt, a large knee joint pulley, and a small knee joint pulley. The variable stiffness mechanism portion comprises a rectangular spring, a slider, a guide rail, and a spring baffle. The rope drive system portion comprises a spring-loaded drive rope, a spring-loaded drive rope, and a variable stiffness rocker.

[0021] like Figure 1 The power prosthetic knee joint shown in the figure comprises a knee joint connector, a knee joint drive, a variable stiffness mechanism, a fixation plate, and a rope drive mechanism. The knee joint connector comprises a standard upper knee joint connector 1, a standard lower knee joint connector 5, a left upper knee joint connector 2, and a right upper knee joint connector 6. The knee joint drive comprises a large knee joint motor 8, a small knee joint motor 4, a large knee joint pulley 9, a small knee joint pulley 14, a timing belt 12, and a drive shaft 13. The variable stiffness mechanism comprises a variable stiffness rocker 23, a lower spring stop 20, an upper spring stop 22, a rectangular spring 21, a slider 18, and a guide rail 17. The fixation plate comprises a left knee joint fixation plate 3 and a right knee joint fixation plate 7. The rope drive mechanism comprises a spring-loaded drive rope 10, a coil 15, a spring-loaded drive rope 16, and a variable stiffness rocker 23. The power of the large knee joint motor 8 is 330W, and the power of the small knee joint motor is 33W.

[0022] Figure 2This is a front view of the interior of the knee joint of the present invention. It includes the upper standard knee joint connector 1, the left upper knee joint connector 2, the lower standard knee joint connector 5, the right knee joint fixation plate 7, the large knee joint motor 8, the large knee joint pulley 9, the spring-loaded drive rope 10, the variable stiffness swing arm angle range 11, the synchronous belt 12, the drive shaft 13, the small knee joint pulley 14, the coil disk 15, the spring-loaded drive rope 16, the guide rail 17, the pulley 18, the slider 19, the lower spring baffle 20, the rectangular spring 21, the upper spring baffle 22, and the variable stiffness swing arm 23. The left upper knee joint connector 2 and the right upper knee joint connector 6 are fixedly connected to the upper standard knee joint connector 1 by bolts. The large knee joint pulley 9 is fixedly connected to the upper bearings of the left upper knee joint connector 2 and the right upper knee joint connector 6, allowing the large knee joint pulley 9 to rotate relative to the left upper knee joint connector 2 and the right upper knee joint connector 6. The large knee pulley 9 is fixedly connected to the left knee plate 3 and the right knee plate 7, so that when the large knee pulley 9 rotates, it can drive the left knee plate 3 and the right knee plate 7 to rotate. At the same time, the large knee motor 8 and the small knee motor 4 are respectively fixed to the right knee plate 7 and the left knee plate 3 by bolts. The transmission shaft 13 is fixedly connected to the rotating shaft of the large knee motor 8, and the small knee pulley 14 is sleeved on the transmission shaft 13 and fixedly connected thereto, so that the rotating shaft of the large knee motor 8 rotates, driving the rotation of the small knee pulley 14. The small knee pulley 14 and the large knee pulley 9 transmit power through the synchronous belt 12. Therefore, the rotation of the rotating shaft of the large knee motor 8 can ultimately drive the rotation of the large knee pulley 9. At the same time, a spring-loaded drive rope 10 is wound around one side of the large knee pulley 9. One end of the spring-loaded drive rope 10 is fixedly connected to the large knee pulley 9, while the other end of the spring-loaded drive rope 10 is fixedly connected to the lower spring baffle 20. Furthermore, the spring-loaded drive rope 10 is wound around the pulley of the variable-stiffness rocker 23. The coil disk 15 is internally fixedly connected to the rotating shaft of the small knee motor 4 and has a cylindrical exterior. A spring-loaded drive rope 16 is wound around the coil disk 15 and fixedly connected to it. The other end of the spring-loaded drive rope 16 is fixedly connected to the spring baffle 22, thereby rotating the rotating shaft of the small knee motor 4 and driving the movement of the spring baffle 22. Both the spring baffle 22 and the lower spring baffle 19 are fixedly connected to corresponding sliders 19 on the guide rail 17, enabling linear motion along the guide rail 17. The guide rail 17 is bolted to the right knee joint fixation plate 7.

[0023] Combine Figure 3 The diagram of the key power transmission parts of the knee joint can make it easier to understand the overall motion transmission and the coordination relationship between them. 24 represents the range of motion under the spring baffle.

[0024] The left side of the large pulley 9 of the knee joint is connected to the synchronous belt 12, and the right side is provided with a spherical groove for fixing the position of the spring-loaded drive rope 10. A small hole is provided on the spherical groove so that the end of the spring-loaded drive rope 10 can pass through and then be tied at the end. Driven by the synchronous belt 12, the large pulley 9 of the knee joint rotates counterclockwise, causing the line segment of the spring-loaded drive rope 10 wrapped around the large pulley 9 of the knee joint to increase. The middle section of the spring-loaded drive rope 10 is wound around the pulleys on both sides of the variable stiffness rocker 23, and the center axis of the left pulley is collinear with the rotation axis of the variable stiffness rocker 23. The spring-loaded drive rope 10 runs downward along the surface of the pulley on the left side of the variable stiffness rocker 23, passes through the spring baffle 22, and is fixed to the lower part 20 of the spring baffle. A large hole is provided on the left side of the spring baffle 22 so that the spring-loaded drive rope 10 can pass through without contacting the spring baffle 22. A small hole is provided on the right side of the spring baffle 22 to allow the spring downward drive rope 16 to pass through. It is then tied near the variable-stiffness rocker 23, forming a secure connection to the spring baffle 22. A small hole is provided on the left side of the spring baffle 20 to allow the lower end of the spring upward drive rope 10 to pass through. It is then tied outside the hole to form a secure connection. A large hole is provided on the right side of the spring baffle 20 to allow the spring downward drive rope 16 to pass through without contacting the spring baffle 20. The lower end of the spring downward drive rope 16 passes over the pulley 18 and is wound around the coil disk 15. The coil disk 15 has a spherical groove with a small hole in the groove to secure the lower end of the spring downward drive rope 16. The lengths of the spring downward drive rope 16 and the spring upward drive rope 10 are fixed, ensuring that the range of motion of the spring baffle 20 meets but does not exceed the set range of motion 24. Counterclockwise rotation of the coil disk 15 drives the upper end of the spring downward drive rope 16 downward, thereby driving the spring baffle 22 downward along the guide rail 17. The large pulley 9 of the knee joint moves counterclockwise, which first drives the variable stiffness swing rod 23 to swing counterclockwise around the rotation axis. When the variable stiffness swing rod 23 is driven to move to the extreme position, the large pulley 9 of the knee joint continues to rotate counterclockwise, which causes the spring baffle 20, which is fixed to the lower end of the spring-pressed drive rope, to move upward along the guide rail 17. The spring baffle 20 is fixed to the bottom of the rectangular spring 21, and the spring baffle 22 is fixed to the top of the rectangular spring 21. The movement of the spring baffle 20 and the spring baffle 22 towards each other will squeeze the spring. If the spring baffle 22 moves downward and the spring baffle 20 is not subjected to the upward force, the spring baffle 22 will move downward with the rectangular spring 21 and the spring baffle 20, and no spring squeezing action will occur. At the same time, the spring baffle 22 will not move upward beyond the initial set position, but will only move downward along the guide rail 17 and then return to its initial position.

Claims

1. A powered lower limb prosthetic knee joint with variable stiffness, comprising a knee joint connector, a knee joint drive portion, a variable stiffness mechanism portion, a fixing plate, and a rope drive system; characterized in that: The knee joint connector includes an upper standard knee joint connector, a left upper knee joint connector, a lower standard knee joint connector, and a right upper knee joint connector. The left upper knee joint connector and the right upper knee joint connector are connected by a bearing. The tops of the left upper knee joint connector and the right upper knee joint connector are respectively fixedly connected to the upper standard knee joint connector by bolts. The lower standard knee joint connector is fixed to the right bottom of the knee joint fixation plate of the fixation plate. The fixation plate includes a left knee joint fixation plate and a right knee joint fixation plate; the left knee joint fixation plate and the right knee joint fixation plate respectively pass through bearings connected to the left knee joint upper connector and the right knee joint upper connector; The knee joint driving part includes a large knee joint motor, a small knee joint motor, a synchronous belt, a transmission shaft, a large knee joint pulley and a small knee joint pulley, the large knee joint pulley passes through the bearings of the left and right upper knee joint connecting parts, and the large knee joint pulley can rotate relative to the left and right upper knee joint connecting parts; the left and right knee joint fixing plates are located on both sides of the large knee joint pulley, and the large knee joint pulleys are fixedly connected to the left and right knee joint fixing plates respectively, so that the large knee joint pulley can drive the left and right knee joint fixing plates to rotate; the large knee joint motor is fixed to the upper right knee joint fixing plate by bolts, the small knee joint motor is fixed to the upper left knee joint fixing plate by bolts, the transmission shaft is fixedly connected to the rotating shaft of the large knee joint motor, the small knee joint pulley is sleeved on the transmission shaft and fixedly connected to the transmission shaft. When the rotating shaft of the large knee joint motor rotates, it can drive the small knee joint pulley to rotate; the small knee joint pulley and the large knee joint pulley are connected by a synchronous belt for power transmission; The variable stiffness mechanism includes a rectangular spring, a slider, a pulley, a guide rail, and a spring baffle. There are two sliders. The rectangular spring is sleeved outside the guide rail, with its top fixedly connected to the spring baffle and its bottom fixedly connected to the bottom of the spring baffle. The upper and lower parts of the spring baffle are respectively fixedly connected to the corresponding sliders. Both sliders are placed on the guide rail so that they can move linearly on the guide rail, and the spring baffle can only move downward. The guide rail is fixed to the upper right side of the knee joint fixation plate by bolts. The rope drive system includes a spring-loaded driving rope, a spring-loaded driving rope and a variable-stiffness pendulum; one end of the variable-stiffness pendulum is fixed to the upper right side of the knee joint fixation plate through a rotating shaft, one end of the spring-loaded driving rope is fixedly connected to the large pulley of the knee joint, the spring-loaded driving rope is wound around the pulley of the variable-stiffness pendulum, and the other end is fixedly connected to the bottom of the spring baffle; one end of the spring-loaded driving rope is fixedly connected to the coil disk and wound around the coil disk, and the other end of the spring-loaded driving rope passes through the pulley and is fixedly connected to the spring baffle. When the coil disk rotates counterclockwise, the spring baffle is driven to move downward along the guide rail through the spring-loaded driving rope; the small motor of the knee joint is located inside the coil disk, and the rotating shaft of the small motor of the knee joint is fixedly connected to the coil disk; When the spring baffle moves downward, power will be transmitted through the spring upward pressure drive rope, and the variable stiffness pendulum will quickly swing to the extreme position. The angle range of the variable stiffness pendulum satisfies the downward movement of the spring baffle to the extreme position; when the variable stiffness pendulum swings to the maximum angle, the large motor of the knee joint continues to complete the flexion action, and it will drive the spring baffle down through the spring upward pressure drive rope, and move the slider up along the guide rail to compress the rectangular spring; at the same time, the small motor of the knee joint continues to rotate counterclockwise, and continues to drive the spring baffle to move downward along the guide rail through the slider through the spring downward pressure drive rope, thereby compressing the rectangular spring; energy storage is achieved through the joint compression of the rectangular spring on and under the spring baffle, and then extension is performed.

2. A variable stiffness powered lower limb prosthetic knee joint according to claim 1, characterized in that In order to achieve customization based on individual differences and different purposes of use of amputee patients, the powered lower limb prosthetic knee joint adopts a standard prosthetic joint connection to facilitate customized replacement.

3. The variable stiffness powered prosthetic knee joint of claim 1, characterized in that When an amputee wears the prosthesis of the present invention and walks, the normal working process of the prosthesis is as follows: First, the powered lower-limb prosthetic knee joint is primarily used to achieve joint flexion and extension. Counterclockwise rotation of the large knee motor 8 achieves flexion, and clockwise rotation achieves extension. Its range of motion is 0-120 degrees, with a maximum flexion angle of 120 degrees. Furthermore, the powered lower-limb prosthetic knee joint often requires greater torque during the extension phase to support standing and walking. The following details the workflow of the powered lower-limb prosthetic knee joint in different scenarios, primarily categorized as low-torque demand and high-torque demand.

4. The variable stiffness powered prosthetic knee joint of claim 1, characterized in that When the knee joint is bent, the spring pulley is rotated to move the small pulley and the small pulley is moved to rotate with the spring. The spring-loaded drive rope will first drive the variable stiffness pendulum to swing upward, increasing its angle with the horizontal axis; in the process of the variable stiffness pendulum swinging upward, the rectangular spring will not be compressed, so when the variable stiffness pendulum has not reached the maximum swing angle, the overall stiffness of the knee joint can be considered to be zero; at the same time, the maximum swing angle of the variable stiffness pendulum meets the maximum angle of the knee joint during daily walking on flat ground; that is, when walking on flat ground, the power is mainly provided by the large motor of the knee joint, and the rectangular spring is almost not compressed; when the knee joint is extended, that is, the large motor of the knee joint moves clockwise, the variable stiffness pendulum will swing downward under power transmission until the minimum angle, that is, the knee joint angle is 0 degrees; the variable stiffness pendulum swings downward mainly according to the torsion spring installed inside, the variable stiffness pendulum swings upward and the torsion spring is twisted, and when the large motor of the knee joint moves clockwise, the variable stiffness pendulum is released, and the torsion spring drives the variable stiffness pendulum to swing downward.

5. The variable stiffness powered prosthetic knee joint of claim 1, characterized in that For scenarios where the joint torque demand is large, such as going up and down stairs, the large knee motor and the small knee motor need to work together. When the large pulley of the knee joint rotates counterclockwise, the spring-pressed drive rope fixed to the large pulley of the knee joint will drive the variable stiffness rocker to swing upward. At the same time, a large torque is required to achieve knee joint extension for going up stairs, and the required joint torque is greater than the peak torque of the knee joint motor. At this time, the small knee joint motor will start working. The small knee joint motor and the large knee joint motor rotate counterclockwise together to achieve knee joint flexion, and complete energy storage through the compression of the rectangular spring. The rectangular spring energy is released during the extension phase to make up for the gap between the torque required for joint extension and the peak torque of the joint motor.

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