Knee-ankle assistive exoskeleton based on metamorphic principle and control method thereof

Abstract

The application discloses a knee-ankle assisting exoskeleton based on a metamorphic principle and a control method thereof. The knee-ankle assisting exoskeleton comprises a control system, a waist driving mechanism, a waist transmission mechanism, a waist input knee joint transmission mechanism, a waist input ankle joint transmission mechanism and a foot bottom pressure sensing device. The waist transmission mechanism adopts a metamorphic mechanism and is in transmission connection with the input ends of the waist input knee joint transmission mechanism and the waist input ankle joint transmission mechanism through two groups of Bowden cables. The metamorphic mechanism performs power output according to a preset three-configuration cyclic mode. Automatic switching of different assisting modes is realized. A knee joint variable stiffness mechanism is further arranged on the output end of the waist input knee joint transmission mechanism. The application drives the knee and ankle joints through a single motor by adopting the metamorphic mechanism, thereby significantly reducing the overall weight of the exoskeleton and improving the assisting efficiency. The application can realize intelligent switching of the exoskeleton in different gait stages, so that the exoskeleton can dynamically adjust the assisting mode.

Description

Technical Field

[0001] This invention belongs to the field of exoskeleton robot technology, specifically a knee and ankle assistive exoskeleton based on the principle of variable cell structure and its control method. Background Technology

[0002] Currently, with the increasing aging population and rapid industrial automation, the rehabilitation needs of people with mobility impairments and the workload of manual laborers are becoming increasingly prominent. For the elderly, post-operative rehabilitation patients, and those with muscle weakness, providing effective assistive support to improve their walking ability and quality of life has become an important research direction in the field of rehabilitation medicine. Meanwhile, in industrial production and military operations, workers often engage in high-intensity work for extended periods, easily leading to muscle fatigue and even occupational injuries. Therefore, researching assistive equipment that can effectively reduce labor intensity and improve work efficiency is of great significance. Against this backdrop, lower limb assistive exoskeletons, as a novel mechatronic device, have received widespread attention and have shown great application potential in rehabilitation medicine, assisted walking, and physical strength enhancement.

[0003] The core objective of lower limb assistive exoskeletons is to provide external assistance to help users complete lower limb movements such as walking and standing, and to reduce muscle burden. Currently, lower limb assistive exoskeletons are mainly divided into two categories: single-joint driven exoskeletons and multi-joint independently driven exoskeletons. Single-joint driven exoskeletons typically use a single motor to drive a single joint. Although the structure is relatively simple, it has significant limitations: it cannot achieve multi-joint coordinated assistance, resulting in unnatural gait assistance; and its assistance efficiency is low, making it difficult to meet the needs of complex movements. The other type is multi-joint independently driven exoskeletons. While these exoskeletons provide better assistance, they also have significant drawbacks: they require multiple motors to drive different joints, resulting in a large system weight and severely impacting wearing comfort; each joint's control system is independent, leading to poor coordination and high energy consumption; and the variable stiffness mechanism requires an additional drive unit, further increasing system complexity. Furthermore, existing lower limb exoskeletons have shortcomings in adaptability: traditional transmission mechanisms cannot dynamically adjust the target joints according to gait stages, resulting in inaccurate assistance timing; stiffness adjustment mechanisms have slow response speeds, making it difficult to match the real-time changes in joint stiffness; and the sensing system is limited in accuracy, affecting the assistance effect. Variable-cell mechanisms have broad application prospects in exoskeletons, but they still face challenges in practical engineering implementation, such as the complexity of mechanism design, optimization of control strategies, and improvement of overall system performance. Summary of the Invention

[0004] To address the aforementioned technical problems in existing technologies, this invention provides a knee-ankle assistive exoskeleton based on the variable-cell principle and its control method. Leveraging the characteristics of the variable-cell mechanism, it enables the simultaneous driving of both the knee and ankle joints using only a single drive motor, effectively reducing the weight of the exoskeleton system and improving assistive efficiency. Furthermore, this invention incorporates intelligent control technologies such as gait recognition and sensor feedback to achieve intelligent switching of the exoskeleton at different gait stages, allowing it to dynamically adjust its assistive mode to adapt to different environments and user needs.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A knee and ankle assistive exoskeleton based on the principle of variable cell structure includes a control system, a lumbar drive mechanism, a lumbar transmission mechanism connected to the lumbar drive mechanism, a lumbar input knee joint transmission mechanism located below the lumbar transmission mechanism, a lumbar input ankle joint transmission mechanism rotatably connected to the lower end of the lumbar input knee joint transmission mechanism, and a foot pressure sensing device fixedly installed on the output end of the lumbar input ankle joint transmission mechanism.

[0007] The waist transmission mechanism includes a waist output knee joint transmission component and a waist output ankle joint transmission component arranged in parallel. The output end of the waist output knee joint transmission component is connected to the input end of the waist input knee joint transmission mechanism through a first Bowden rope group, and the output end of the waist output ankle joint transmission component is connected to the input end of the waist input ankle joint transmission mechanism through a second Bowden rope group.

[0008] The two output ends of the waist-output knee joint transmission component and the waist-output ankle joint transmission component output power according to three configuration cycle modes: “0-0→1-0→0-1→0-0…”, where 0 indicates that the corresponding output end is in a state of no power output and 1 indicates that the corresponding output end is in a state of power output.

[0009] The output end of the waist input knee joint transmission mechanism is also equipped with a knee joint variable stiffness mechanism.

[0010] Furthermore, the waist drive mechanism includes a waist plate, a drive motor fixedly mounted on the waist plate, and a camshaft rotatably mounted on the waist plate and connected to the output end of the drive motor. A knee joint disc cam and an ankle joint disc cam are fixedly connected to the camshaft.

[0011] Furthermore, the waist-mounted output knee joint transmission assembly includes a knee joint rack that movably engages with a knee joint disc cam, a knee joint gear rotatably mounted on the waist plate and meshing with the knee joint rack, and a knee joint input line wheel rotatably mounted on the waist plate. One side of the shaft end of the knee joint input line wheel and one side of the shaft end of the knee joint gear are connected by a knee joint electromagnetic clutch.

[0012] Furthermore, the waist input knee joint transmission mechanism includes a thigh rod, a knee joint output line wheel rotatably mounted at the bottom of the thigh rod, a calf rod fixedly connected to the shaft end of one side of the knee joint output line wheel, and the bottom end of the first Bowden rope assembly is fixedly connected to the knee joint output line wheel.

[0013] Furthermore, the knee joint variable stiffness mechanism includes a variable stiffness turntable coaxially arranged with the knee joint output pulley, a first variable stiffness connecting rod eccentrically hinged to the end face of the variable stiffness turntable, a second variable stiffness connecting rod hinged to the other end of the first variable stiffness connecting rod and vertically slidably connected to the thigh rod, and a variable stiffness cam rotatably mounted on the thigh rod and located directly above the top of the second variable stiffness connecting rod. The variable stiffness cam is a frustum-shaped cone structure with its axis horizontally arranged, and a first shape memory alloy spring and a second shape memory alloy spring are fixedly connected to its two end faces respectively. The top of the second variable stiffness connecting rod is embedded with a ball that can slide in contact with the surface of the variable stiffness cam.

[0014] Furthermore, the waist-mounted output ankle joint transmission assembly includes an ankle joint rack that movably engages with an ankle joint disc cam, an ankle joint gear that is rotatably mounted on the waist plate and meshes with the ankle joint rack, and an ankle joint input line wheel that is rotatably mounted on the waist plate. One side of the shaft end of the ankle joint input line wheel and one side of the shaft end of the ankle joint gear are connected by an ankle joint electromagnetic clutch.

[0015] Furthermore, the waist input ankle joint transmission mechanism includes an ankle joint output line wheel rotatably mounted on the bottom end of the calf bar, an ankle plate rotatably sleeved on the shaft end of the ankle joint output line wheel, the bottom end of the second Bowden rope group being fixedly connected to the ankle joint output line wheel, and the foot pressure sensing device being fixedly connected to the ankle plate.

[0016] Furthermore, a knee potentiometer is provided at the hinge joint between the bottom end of the thigh bar and the top end of the calf bar, and an ankle potentiometer is provided at the hinge joint between the bottom end of the calf bar and the ankle plate.

[0017] A control method for a knee-ankle assistive exoskeleton based on the principle of variable cell structure is also provided, including the following steps:

[0018] Step 1: The subject wears the knee and ankle assistive exoskeleton based on the principle of cell variation. The system is powered on and initialized, and all functional components enter standby mode.

[0019] Step 2: The control system reads plantar pressure data, knee joint rotation data, and ankle joint rotation data in real time to determine the current stage of the leg within the gait cycle;

[0020] Step 3: Based on the stage state of the leg, the control system adjusts the transmission configuration of the lumbar output knee joint transmission component and the lumbar output ankle joint transmission component to achieve automatic switching between knee joint assist mode, ankle joint assist mode and non-assist mode. The control system also adjusts the variable stiffness state of the knee joint variable stiffness mechanism to achieve dynamic adjustment of the knee joint support torque.

[0021] Step 4: According to the gait cycle, the control system cyclically switches the transmission configuration of the lumbar output knee joint transmission component and the lumbar output ankle joint transmission component, as well as the stiffness state of the knee joint variable stiffness mechanism, in real time until the subject stops walking or an emergency stop signal is triggered.

[0022] Step 5: Shut down the system, remove the exoskeleton from the subject, and the system automatically saves the gait data to the PC for subsequent analysis.

[0023] Furthermore, the gait cycle is divided into a standing flexion phase, a standing extension phase, a pre-swing phase, and a swing phase.

[0024] During the standing flexion phase, the control system energizes the heating wire of the shape memory alloy spring in the knee joint variable stiffness mechanism. By adjusting the current, the stiffness of the shape memory alloy spring is changed, thereby driving the variable stiffness cam to move and dynamically adjusting the knee joint support torque.

[0025] During the standing extension phase, the lumbar drive mechanism drives the lumbar input knee joint transmission mechanism to rotate through the lumbar output knee joint transmission assembly and the first Bowden rope assembly, providing knee extension assistance.

[0026] During the pre-swing phase, the lumbar drive mechanism drives the lumbar input ankle drive mechanism to rotate through the lumbar output ankle joint drive assembly and the second Bowden rope assembly, providing ankle dorsiflexion assistance.

[0027] During the swing phase, neither the waist drive mechanism nor the waist transmission mechanism is engaged, and the ankle joint transmission mechanism is in a free state.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. The lower limb assistive exoskeleton designed in this invention adopts a variable cell mechanism, which drives the knee and ankle joints through a single motor, significantly reducing the overall weight of the exoskeleton and improving the comfort and portability of the wearer. It is suitable for medical rehabilitation and industrial assistive scenarios.

[0030] 2. By dynamically switching the transmission path (knee / ankle joint) through an electromagnetic clutch, the configuration of the variable-cell mechanism is reconfigured, allowing a single motor to drive the knee and ankle joints at different gait stages. This reduces system complexity and energy consumption while ensuring the accuracy and coordination of the assist.

[0031] 3. The variable stiffness mechanism using shape memory alloy springs can automatically increase the stiffness of the knee joint to support body weight during the standing phase and reduce the stiffness during the swinging phase to reduce movement resistance, effectively reducing the wearer's energy consumption and improving the naturalness of walking.

[0032] 4. Based on the disc cam-based assist design, the cam profile is optimized by fitting the angle-torque curves of the knee and ankle joints to ensure that the assist torque is highly matched with the human gait requirements, avoid movement interference, and improve assist efficiency.

[0033] 5. The drive and transmission mechanisms (motor, reducer, cam, etc.) are centrally located in the waist area, and the legs adopt a lightweight carbon fiber structure, which not only ensures the stability of power transmission, but also reduces the impact of leg inertia on gait, making the gait after wearing the exoskeleton closer to the natural walking state. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the overall structure of the knee and ankle assistive exoskeleton based on the principle of variable cell in this invention.

[0035] Figure 2 This is a schematic diagram of the waist drive mechanism;

[0036] Figure 3 This is a schematic diagram of the structure of the waist-output knee joint transmission assembly;

[0037] Figure 4 A schematic diagram of the lumbar input knee joint transmission mechanism;

[0038] Figure 5 An exploded view of the structure of the waist input knee joint transmission mechanism;

[0039] Figure 6 This is a schematic diagram of the knee joint variable stiffness mechanism.

[0040] Figure 7 This is an exploded view of the knee joint variable stiffness mechanism.

[0041] Figure 8 A schematic diagram of the waist-output ankle joint transmission assembly;

[0042] Figure 9 A schematic diagram of the waist-input ankle joint transmission mechanism;

[0043] Figure 10 An exploded view of the structure of the waist-input ankle joint transmission mechanism;

[0044] Figure 11 This is a block diagram of the hardware structure of the knee and ankle assistive exoskeleton based on the principle of variable cell in this invention;

[0045] Figure 12 This is a flowchart of the knee and ankle assistive exoskeleton control based on the principle of variable cell in this invention. Detailed Implementation

[0046] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0047] It should be noted that when a component is said to be "installed on" another component, it can be directly on the other component or it may be in a component that is centered on it. When a component is said to be "set on" another component, it can be directly set on the other component or it may also be in a component that is centered on it. When a component is said to be "fixed to" another component, it can be directly fixed to the other component or it may also be in a component that is centered on it.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0049] See appendix Figure 1 A knee-ankle assistive exoskeleton based on the principle of variable cell structure includes a control system, a lumbar drive mechanism 10, a lumbar transmission mechanism 20 connected to the lumbar drive mechanism 10, a lumbar input knee joint transmission mechanism 50 located below the lumbar transmission mechanism 20, a lumbar input ankle joint transmission mechanism 60 rotatably connected to the lower end of the lumbar input knee joint transmission mechanism 50, and a foot pressure sensor fixedly mounted on the output end of the lumbar input ankle joint transmission mechanism 60. The lumbar transmission mechanism 20 includes a lumbar output knee joint transmission component and a lumbar output ankle joint transmission component arranged in parallel. The output end of the lumbar output knee joint transmission component is connected to the input end of the lumbar input knee joint transmission mechanism 50 via a first Bowden rope group, and the output end of the lumbar output ankle joint transmission component is connected to the input end of the lumbar input ankle joint transmission mechanism 60 via a second Bowden rope group. The two output ends of the lumbar output knee joint transmission component and the lumbar output ankle joint transmission component output power according to three configuration cycle modes: "0-0→1-0→0-1→0-0…", where 0 indicates that the corresponding output end is in a no-power output state, and 1 indicates that the corresponding output end is in a power output state. The output end of the lumbar input knee joint transmission mechanism 50 is also equipped with a knee joint variable stiffness mechanism 40.

[0050] The following provides a detailed explanation of the specific structural composition and working principle of each functional part of the knee and ankle assistive exoskeleton based on the principle of cellular variation.

[0051] like Figure 2 As shown, the lumbar drive mechanism 10 includes a lumbar plate 101, a drive motor 102 fixedly mounted on the lumbar plate 101, and a camshaft 107 rotatably mounted on the lumbar plate 101 and connected to the output end of the drive motor 102. A knee joint disc cam 109 and an ankle joint disc cam 110 are fixedly connected to the camshaft 107. Specifically, the lumbar plate 101 is a rigid thin plate, its width corresponding to the waist width of a typical adult. It has strap fixing openings at both ends, allowing the lumbar plate 101 to be fixed to the waist of the rehabilitation trainee via straps. A planetary reducer 103 is fixedly connected to the output shaft of the drive motor 102. The planetary reducer 103 is fixedly mounted on the top side of the lumbar plate 101 via a drive motor support 104, with its output shaft vertically downwards and a first bevel gear 105 fixedly connected to its output shaft end via a key. The camshaft 107 is horizontally positioned below the first bevel gear 105, and a second bevel gear 106 meshing with the first bevel gear 105 is fixedly connected to its shaft end via a key. The camshaft 107 is rotatably mounted on the camshaft support 108 via bearings, and the camshaft support 108 is fixedly connected to the side of the waist plate 101 by bolts. The knee joint disc cam 109 and the ankle joint disc cam 110 are located on both sides of the camshaft support 108 and are fixedly mounted on the camshaft 107 by keys.

[0052] Thus, after the drive motor 102 starts working, it drives the first bevel gear 105 to rotate via the planetary gear reducer 103. The first bevel gear 105 drives the second bevel gear 106 to rotate through meshing transmission, thereby transmitting the motion to the camshaft 107, thereby driving the knee joint disc cam 109 and the ankle joint disc cam 110 to rotate synchronously and in the same direction.

[0053] like Figure 3 As shown, the lumbar output knee joint transmission assembly includes a knee joint rack 202 that is movably engaged with a knee joint disc cam 109, a knee joint gear 207 that is rotatably mounted on the lumbar plate 101 and meshes with the knee joint rack 202, and a knee joint input cable pulley 212 that is rotatably mounted on the lumbar plate 101. One side of the shaft end of the knee joint input cable pulley 212 and one side of the shaft end of the knee joint gear 207 are connected by a knee joint electromagnetic clutch 209.

[0054] Specifically, a cam guide groove is formed in the left end face of the knee joint disc cam 109, and a knee joint disc cam roller 201 is set in the cam guide groove. A smooth bolt is slidably sleeved in the knee joint disc cam roller 201, and the end of the smooth bolt is threaded to the right top of the knee joint rack 202. In this way, the knee joint rack 202 and the knee joint disc cam 109 form a cam push rod transmission mechanism. A knee joint slide rail support 206 is fixedly connected to the side of the waist plate 101 by bolts. A vertically arranged knee joint slide rail 205 is fixedly connected to the side of the knee joint slide rail support 206 by bolts. A knee joint slider 204 is slidably connected to the knee joint slide rail 205. A knee joint rack slider connector 203 is fixedly connected to the side of the knee joint slider 204 by bolts. The side of the knee joint rack 202 and the side of the knee joint rack slider connector 203 are attached to each other and fixedly connected by bolts. This ensures that the knee joint rack 202 is vertically positioned and can only move vertically.

[0055] Knee joint gear shaft support 210 and knee joint thread wheel shaft support 213 are bolted to the side of the waist plate 101. Knee joint gear 207 is keyed to knee joint gear shaft 208, and the right end of knee joint gear shaft 208 is rotatably mounted on knee joint gear shaft support 210 via a bearing. Knee joint input thread wheel 212 is keyed to knee joint thread wheel shaft 211, and the left end of knee joint thread wheel shaft 211 is rotatably mounted on knee joint thread wheel shaft support 213 via a bearing. Knee joint electromagnetic clutch 209 is located between knee joint gear 207 and knee joint input thread wheel 212, with its right end keyed to the left end of knee joint gear shaft 208 and its left end keyed to the right end of knee joint thread wheel shaft 211. Thus, when the knee joint electromagnetic clutch 209 is energized, the knee joint gear shaft 208 and the knee joint threaded wheel shaft 211 are connected for transmission. The rotational power input from the knee joint gear 207 can be output synchronously by the knee joint input threaded wheel 212, which corresponds to state "1" above. When the knee joint electromagnetic clutch 209 is de-energized, the knee joint gear shaft 208 and the knee joint threaded wheel shaft 211 are in a non-connected state. The knee joint gear 207 rotates freely, and the knee joint input threaded wheel 212 has no power input or output, which corresponds to state "0" above.

[0056] Meanwhile, a Bowden rope guide device 214 for the input end knee joint, located directly below the knee joint input line wheel 212, is fixedly connected to the side of the waist plate 101 by bolts. The first Bowden rope group consists of a first Bowden rope 31 and a second Bowden rope 32. The two Bowden ropes pass through two positioning holes on the input end knee joint Bowden rope guide device 214, so that the two Bowden lines are located on both sides of the axis of the knee joint input line wheel 212. The top ends of the two Bowden lines are fixedly connected to the two ends of the diameter line of the knee joint input line wheel 212, and the bottom ends are fixedly connected to the two ends of the diameter line of the knee joint output line wheel 505 at the input end of the waist input knee joint transmission mechanism 50.

[0057] Thus, when the knee joint disc cam 109 rotates forward / reverse, it drives the knee joint rack 202 to move linearly up / down via cam transmission. The knee joint rack 202 drives the knee joint gear 207 to rotate forward / reverse, which in turn drives the knee joint gear shaft 208 to rotate synchronously in the same direction. Then, through the knee joint electromagnetic clutch 209, it drives the knee joint thread wheel shaft 211 to rotate, which in turn drives the knee joint input thread wheel 212 to rotate synchronously in the same direction. When the knee joint input thread wheel 212 rotates forward, the first Bowden rope 31 pulls the knee joint output thread wheel 505 to rotate synchronously in the forward direction. When the knee joint input thread wheel 212 rotates in the reverse direction, the second Bowden rope 32 pulls the knee joint output thread wheel 505 to rotate synchronously in the reverse direction, thereby achieving flexible connection and power transmission in both forward and reverse directions.

[0058] like Figure 4 and Figure 5 As shown, the lumbar input knee joint transmission mechanism 50 includes a thigh bar 506, a knee joint output cable reel 505 rotatably mounted at the bottom of the thigh bar 506, and a lower leg bar 507 fixedly connected to one side of the shaft end of the knee joint output cable reel 505. The bottom end of the first Bowden rope assembly is fixedly connected to the knee joint output cable reel 505. Specifically, the thigh bar 506 is a rigid long strip plate made of lightweight carbon fiber material. An arc-shaped thigh fixation member 508 is provided on one side of its top end. Adhesive straps are bound to both ends of the thigh fixation member 508. The thigh bar 506 and the thigh fixation member 508 can be fixed to the thigh of the rehabilitation trainee through the straps. The thigh fixation component 508 has a positioning block fixedly installed in the middle, and the upper part of the thigh rod 506 has several rows of positioning holes. The bolt passes through the positioning holes and is threadedly connected to the positioning block, thereby fixing the positioning block to the thigh rod 506. By adjusting the positioning holes matched by the bolts, the fixing position of the positioning block and the thigh fixation component 508 on the thigh rod 506 can be adjusted, thereby adjusting the distance from the thigh fixation component 508 to the rotational connection position (knee joint) of the thigh rod 506 and the lower leg rod 507 to meet the binding needs of different people with different leg lengths.

[0059] The knee joint output cable reel 505 is fixed to the knee shaft 502 by a key, and the right end of the knee shaft 502 is rolled onto the bottom end of the thigh rod 506 via a bearing. The calf rod 507 is also a rigid long strip plate made of lightweight carbon fiber material, and its top end is fixed to the right end of the knee shaft 502 by bolts, so that the calf rod 507 and the thigh rod 506 can rotate relative to each other, corresponding to the knee joint of the leg. The bottom end of the thigh rod 506 is fixed to the output end knee joint Bowden rope guide device 501 located directly above the knee joint output cable reel 505 by bolts. The bottom ends of the first Bowden rope 31 and the second Bowden rope 32 pass through two positioning holes on the output end knee joint Bowden rope guide device 501, so that the two Bowden lines are located on both sides of the axis of the knee joint input cable reel 212, and their bottom ends are fixed to the two ends of the diameter line of the knee joint output cable reel 505, thereby providing tension for the forward / reverse rotation of the knee joint output cable reel 505.

[0060] To detect the rotation information at the knee joint in real time and obtain the relative positional relationship between the lower leg rod 507 and the thigh rod 506, preferably, a knee joint potentiometer 503 is installed at the knee joint, specifically at the hinge point between the bottom end of the thigh rod 506 and the top end of the lower leg rod 507. Specifically, a knee joint potentiometer bracket 504 is fixedly connected to the left side of the top end of the lower leg rod 507, and the left side folding plate of the knee joint potentiometer bracket 504 is sleeved on the outer side of the left end of the knee shaft 502. The fixed end of the knee joint potentiometer 503 is fixedly connected to the side of the output end knee joint Bowden rope guide device 501 by bolts, and the rotating shaft end of the knee joint potentiometer 503 is inserted into the left end face of the knee shaft 502.

[0061] Thus, the first Bowden rope 31 / second Bowden rope 32 passing through the Bowden rope guide device 501 at the output end of the knee joint drives the output pulley 505 to rotate forward / reverse. The output pulley 505 drives the knee shaft 502 to rotate, thereby driving the lower leg rod 507 to rotate, thus realizing the rotation of the knee joint. The fixed end of the knee potentiometer 503 is relatively fixed to the thigh rod 506 through the Bowden rope guide device 501 at the output end of the knee joint, while the rotating shaft end of the knee potentiometer 503 is relatively fixed to the lower leg rod 507 through the knee shaft 502. Therefore, the knee potentiometer 503 can detect the relative rotation angle between the lower leg rod 507 and the thigh rod 506 in real time.

[0062] like Figure 6 and Figure 7As shown, the knee joint variable stiffness mechanism 40 includes a variable stiffness turntable 401 coaxially arranged with the knee joint output pulley 505, a first variable stiffness connecting rod 402 eccentrically hinged to the end face of the variable stiffness turntable 401, a second variable stiffness connecting rod 403 hinged to the other end of the first variable stiffness connecting rod 402 and vertically slidably connected to the thigh rod 506, and a variable stiffness cam 406 rotatably mounted on the thigh rod 506 and located directly above the top of the second variable stiffness connecting rod 403. The variable stiffness cam 406 is a frustum-shaped cone structure with its axis horizontally arranged. A first shape memory alloy spring 407 and a second shape memory alloy spring 408 are fixedly connected to its two end faces respectively. A ball bearing 405 that can slide in contact with the surface of the variable stiffness cam 406 is embedded in the top of the second variable stiffness connecting rod 403.

[0063] Specifically, the variable stiffness turntable 401 is fixed to the knee shaft 502 by a key. A smooth rod bolt is threaded onto one edge of the end face of the variable stiffness turntable 401. The bottom end of the first variable stiffness connecting rod 402 is movably sleeved on the smooth rod bolt. The top end of the first variable stiffness connecting rod 402 and the bottom end of the second variable stiffness connecting rod 403 are rotatably connected by a bolt pair. A variable stiffness guide support 404 located above the variable stiffness cam 406 is fixedly connected to the side of the thigh rod 506 by bolts. A guide hole is vertically arranged at the left end of the variable stiffness guide support 404 and matches the cross-sectional shape of the second variable stiffness connecting rod 403. The upper part of the second variable stiffness connecting rod 403 is movably inserted into the guide hole. The variable stiffness turntable 401, the first variable stiffness connecting rod 402, and the second variable stiffness connecting rod 403 constitute an eccentric connecting rod transmission mechanism. The ball bearing 405 is embedded in a hole at one end of the second variable stiffness connecting rod 403 near the variable stiffness cam 406 (i.e., the top end of the second variable stiffness connecting rod 403). The left and right sides of the middle of the side of the thigh rod 506 are respectively bolted to a first variable stiffness support 410 and a second variable stiffness support 411. A horizontally arranged variable stiffness camshaft 409 is bolted between the ends of the first variable stiffness support 410 and the second variable stiffness support 411. The variable stiffness cam 406 is movably sleeved on the variable stiffness camshaft 409 and can move horizontally on the variable stiffness camshaft 409. A first shape memory alloy spring 407 and a second shape memory alloy spring 408 are respectively sleeved on the variable stiffness camshaft 409 and located on the left and right sides of the variable stiffness cam 406.

[0064] Thus, when the knee shaft 502 rotates in the forward direction, it drives the variable stiffness turntable 401 to rotate synchronously in the same direction. The variable stiffness turntable 401 drives the second variable stiffness connecting rod 403 to move vertically upward through the first variable stiffness connecting rod 402. The ball 405 on the second variable stiffness connecting rod 403 moves vertically synchronously. After the ball 405 contacts the conical surface of the variable stiffness cam 406, the horizontal component of the contact force pushes the variable stiffness cam 406 to move horizontally on the variable stiffness camshaft 409 (moving towards the large radius end face of the truncated cone, i.e., as shown in the image). Figure 6 and Figure 7 (as shown in the diagram, the left side moves), which causes the first shape memory alloy spring 407 located on the left side to be deformed by the compression of the variable stiffness cam 406, thereby achieving automatic adjustment of the variable stiffness.

[0065] Variable stiffness principle: At the start of gait, power is supplied to the heating wire wound on the second shape memory alloy spring 408, keeping it at its non-extendable natural length. Meanwhile, the first shape memory alloy spring 407 remains stretched. At this time, the variable stiffness cam 406 is in its rightmost position, and the ball bearing 405 is directly below the lowest end (leftmost end) of the lowest side generatrix of the conical surface of the variable stiffness cam 406. During the first phase of gait with both feet supporting the body, when the knee joint angle increases to 8°, the ball bearing 405 rises vertically through the eccentric linkage mechanism until it contacts the lowest end of the lowest side generatrix of the conical surface of the variable stiffness cam 406. The heating wire wound on the second shape memory alloy spring 408 is de-energized, and the second shape memory alloy spring 408 returns to its extendable length. As the knee joint angle continues to increase, the ball bearing 405 continues to compress the conical surface of the variable stiffness cam 406, causing the variable stiffness cam 406 to continue moving to the left. When the knee joint angle increases to 15°, the variable stiffness cam 406 moves horizontally to its leftmost position. The ball 405 contacts the critical point of the edge of the lowest side generatrix (rightmost end of the conical surface) of the variable stiffness cam 406. At this time, the length of the first shape memory alloy spring 407 returns to its non-stretched natural state. Power is supplied to the heating wire wound on the first shape memory alloy spring 407, keeping it in its non-stretched natural length state, while the second shape memory alloy spring 408 is in a stretched state. When the knee joint angle continues to increase, the ball 405 continues to move vertically upward and disengages from the conical surface, no longer contacting the variable stiffness cam 406. During the swaying phase of the gait cycle, the variable stiffness turntable 401 rotates in the opposite direction, and the corresponding knee joint angle gradually decreases. Through the transmission of the eccentric linkage mechanism, the ball 405 descends vertically to reset, while the variable stiffness cam 406 remains in its leftmost position. When the joint angle is below 8°, the heating wire wound on the first shape memory alloy spring 407 is de-energized, and the first shape memory alloy spring 407 returns to its length-extendable state. The power supply provides power to the heating wire wound on the second shape memory alloy spring 408, causing it to retract to its natural length and simultaneously drive the variable stiffness cam 406 to move to the right and reset. During the movement, it will not contact the ball bearing 405, thus preparing for the start of the next gait cycle.

[0066] like Figure 8 As shown, the waist output ankle joint transmission assembly includes an ankle joint rack 216 that is movably engaged with the ankle joint disc cam 110, an ankle joint gear 221 that is rotatably mounted on the waist plate 101 and meshes with the ankle joint rack 216, and an ankle joint input line pulley 226 that is rotatably mounted on the waist plate 101. One side of the shaft end of the ankle joint input line pulley 226 and one side of the shaft end of the ankle joint gear 216 are connected by an ankle joint electromagnetic clutch 223.

[0067] Specifically, a cam guide groove is provided on the right end face of the ankle joint disc cam 110, and an ankle joint disc cam roller 215 is provided in the cam guide groove. A smooth bolt is slidably sleeved in the ankle joint disc cam roller 215, and the end of the smooth bolt is threaded to the left side of the top of the ankle joint rack 216. In this way, the ankle joint rack 216 and the ankle joint disc cam 110 form a cam push rod transmission mechanism. An ankle joint slide rail support 220 is fixedly connected to the side of the waist plate 101 by bolts. A vertically arranged ankle joint slide rail 219 is fixedly connected to the side of the ankle joint slide rail support 220 by bolts. An ankle joint slider 218 is slidably connected to the ankle joint slide rail 219. An ankle joint rack slider connector 217 is fixedly connected to the side of the ankle joint slider 218 by bolts. The side of the ankle joint rack 216 and the side of the ankle joint rack slider connector 217 are attached to each other and fixedly connected by bolts. This allows the ankle joint rack 216 to be vertically positioned and to move only vertically.

[0068] Ankle joint gear shaft support 224 and ankle joint thread wheel shaft support 227 are bolted to the side of the waist plate 101. Ankle joint gear 216 is keyed to ankle joint gear shaft 222, and the left end of ankle joint gear shaft 222 is rotatably mounted on ankle joint gear shaft support 224 via bearing. Ankle joint input thread wheel 226 is keyed to ankle joint thread wheel shaft 225, and the right end of ankle joint thread wheel shaft 225 is rotatably mounted on ankle joint thread wheel shaft support 227 via bearing. Ankle joint electromagnetic clutch 223 is located between ankle joint gear 216 and ankle joint input thread wheel 226, with its left end keyed to the right end of ankle joint gear shaft 222 and its right end keyed to the left end of ankle joint thread wheel shaft 225. Thus, when the ankle joint electromagnetic clutch 223 is energized, the ankle joint gear shaft 222 and the ankle joint wheel shaft 225 are connected for transmission. The rotational power input from the ankle joint gear 216 can be output synchronously by the ankle joint input wheel 226, which corresponds to state "1" above. When the ankle joint electromagnetic clutch 223 is de-energized, the ankle joint gear shaft 222 and the ankle joint wheel shaft 225 are in a non-connected state. The ankle joint gear 216 rotates freely, and the ankle joint wheel shaft 225 has no power input or output, which corresponds to state "0" above.

[0069] Meanwhile, an input-end ankle joint Bowden rope guide device 228, located directly below the ankle joint input line wheel 226, is bolted to the side of the waist plate 101. The second Bowden rope group consists of a third Bowden rope 33 and a fourth Bowden rope 34. The two Bowden ropes pass through two positioning holes on the input-end ankle joint Bowden rope guide device 228, so that the two Bowden lines are located on both sides of the axis of the ankle joint input line wheel 226. The top ends of the two Bowden lines are fixedly connected to the two ends of the diameter line of the ankle joint input line wheel 226, and the bottom ends are fixedly connected to the two ends of the diameter line of the ankle joint output line wheel 604 at the input end of the waist input ankle joint transmission mechanism 60.

[0070] Thus, when the ankle joint disc cam 110 rotates forward / reverse, it drives the ankle joint rack 216 to move linearly up / down via cam transmission. The ankle joint rack 216 drives the ankle joint gear 216 to rotate forward / reverse, which in turn drives the ankle joint gear shaft 222 to rotate synchronously in the same direction. Then, through the ankle joint electromagnetic clutch 223, it drives the ankle joint thread wheel shaft 225 to rotate, which in turn drives the ankle joint input thread wheel 226 to rotate synchronously in the same direction. When the ankle joint input thread wheel 226 rotates forward, the third Bowden rope 33 pulls the ankle joint output thread wheel 604 to rotate synchronously in the forward direction. When the ankle joint input thread wheel 226 rotates in the reverse direction, the fourth Bowden rope 34 pulls the ankle joint output thread wheel 604 to rotate synchronously in the reverse direction, thereby achieving flexible connection and power transmission in both forward and reverse directions.

[0071] like Figure 9 and Figure 10 As shown, the waist-input ankle joint transmission mechanism 60 includes an ankle joint output thread pulley 604 rotatably mounted on the bottom end of the calf rod 507, an ankle plate 607 rotatably sleeved on the shaft end of the ankle joint output thread pulley 604, and the bottom end of the second Bowden rope assembly is fixedly connected to the ankle joint output thread pulley 604. Specifically, the calf rod 507 is a rigid long strip plate, with a first calf fixation member 609 and a second calf fixation member 610 arranged vertically and in an arc shape on its middle side. Adhesive straps are bound to the two ends of the first calf fixation member 609 and the second calf fixation member 610, which can be used to fix the calf rod 507 and the two calf fixation members to the calf of the rehabilitation trainer. Each of the two lower leg fixation components has a positioning block fixedly installed in the middle. The lower leg rod 507 has several rows of positioning holes in the middle. Bolts pass through the positioning holes and are threadedly connected to the positioning blocks, thereby fixing the two positioning blocks to the lower leg rod 507. By adjusting the positioning holes matched by the bolts, the fixed positions of the positioning blocks and the two lower leg fixation components on the lower leg rod 507 can be adjusted, thereby adjusting the relative positions between the two lower leg fixation components and the distance from the lower second lower leg fixation component 610 to the rotational connection position (ankle joint) of the lower leg rod 507 and the ankle plate 607, so as to meet the binding needs of different people with different lower leg lengths.

[0072] Ankle joint output pulley 604 is fixed to ankle shaft 605 by a key. The middle part of ankle shaft 605 is rolled on the bottom end of calf rod 507 by a bearing. Ankle plate connector 606 is fixedly sleeved on the outer side of the right end of ankle shaft 605 by a key. A connecting plate perpendicular to the ankle plate 607 is fixedly provided on the side. The connecting plate is fixedly connected to the right side of ankle plate connector 606 by bolts, so that ankle plate 607 and calf rod 507 can rotate relative to each other, corresponding to the ankle joint of the leg. The bottom end of the lower leg bar 507 is fixedly connected to the output ankle joint Bowden rope guide device 601 located directly above the ankle joint output rope wheel 604 by bolts. The bottom ends of the third Bowden rope 33 and the fourth Bowden rope 34 pass through two positioning holes on the output ankle joint Bowden rope guide device 601, so that the two Bowden ropes are located on both sides of the axis of the ankle joint output rope wheel 604, and the bottom ends are fixedly connected to the two ends of the diameter line of the ankle joint output rope wheel 604, thereby providing tension for the forward / reverse rotation of the ankle joint output rope wheel 604.

[0073] The main body of the plantar pressure sensor 608 is an L-shaped plate. Its top vertical section is fixedly connected to the ankle plate 607 by bolts. Several rows of bolt connection holes are provided on the side of the top vertical section. Several rows of positioning holes are provided on the side of the ankle plate 607. By adjusting the matching position of the bolt connection holes and the positioning holes, the horizontal and vertical relative positions of the plantar pressure sensor 608 on the ankle plate 607 can be adjusted to meet the needs of trainees with different ankle sizes.

[0074] To detect the ankle joint's rotation information in real time and obtain the relative positional relationship between the ankle plate 607 and the lower leg bar 507, preferably, an ankle potentiometer 602 is installed at the ankle joint, specifically at the hinge point between the bottom end of the lower leg bar 507 and the ankle plate 607. Specifically, an ankle potentiometer bracket 603 is bolted to the side of the ankle plate 607, and the left folding plate of the ankle potentiometer bracket 603 is fitted onto the outer side of the left end of the ankle shaft 605. The fixed end of the knee potentiometer 503 is bolted to the side of the output ankle joint Bowden rope guide device 601, and the rotating shaft end of the ankle potentiometer 602 is inserted into the left end face of the ankle shaft 605.

[0075] Thus, the third Bowden rope 33 / fourth Bowden rope 34 passing through the Bowden rope guide device 601 at the output end of the ankle joint drives the ankle joint output pulley 604 to rotate forward / reverse. The ankle joint output pulley 604 drives the ankle shaft 605 to rotate, thereby driving the ankle plate 607 to rotate and realize the rotation of the ankle joint. The fixed end of the ankle potentiometer 602 is relatively fixed to the lower leg bar 507 through the Bowden rope guide device 601 at the output end of the ankle joint, and the rotating shaft end of the ankle potentiometer 602 is relatively fixed to the ankle plate 607 through the ankle shaft 605. Therefore, the ankle potentiometer 602 can detect the relative rotation angle between the ankle plate 607 and the lower leg bar 507 in real time.

[0076] The variable cell principle in the lumbar transmission mechanism 20: In the exoskeleton, there are a total of 8 components constituting the variable cell mechanism, namely, knee joint gear shaft 208, knee joint thread wheel shaft 211, knee joint input thread wheel 212, knee joint electromagnetic clutch 209, ankle joint gear shaft 222, ankle joint thread wheel shaft 225, ankle joint input thread wheel 226, and ankle joint electromagnetic clutch 223. Configuration 1 is that both knee joint electromagnetic clutch 209 and ankle joint electromagnetic clutch 223 are not energized, corresponding to the aforementioned "0-0" mode state; Configuration 2 is that knee joint electromagnetic clutch 209 is energized and ankle joint electromagnetic clutch 223 is not energized, corresponding to the aforementioned "1-0" mode state; Configuration 3 is that knee joint electromagnetic clutch 209 is not energized and ankle joint electromagnetic clutch 223 is energized, corresponding to the aforementioned "0-1" mode state.

[0077] When the variable-cell mechanism is in configuration 1, the rotation of the knee joint gear shaft 208 and the ankle joint gear shaft 222 cannot be transmitted to the knee joint wheel shaft 211 and the ankle joint wheel shaft 225 through the knee joint electromagnetic clutch 209 and the ankle joint electromagnetic clutch 223, resulting in the inability to transmit motion. At the instant the variable-cell mechanism changes from configuration 1 to configuration 2, the knee joint gear shaft 208 and the knee joint thread wheel shaft 211 are fixed together through the knee joint electromagnetic clutch 209 to form a new component I, and a rotational pair constraint is formed between them and the knee joint rack 202 and the knee joint input thread wheel 212, respectively. At the instant the variable-cell mechanism changes from configuration 2 to configuration 3, the newly formed component I is separated and restored to the knee joint gear shaft 208 and the knee joint thread wheel shaft 211 through the knee joint electromagnetic clutch 209. At the same time, the ankle joint gear shaft 222 and the ankle joint thread wheel shaft 225 are fixed together through the ankle joint electromagnetic clutch 223 to form a new component II, and a rotational pair constraint is formed between them and the ankle joint rack 216 and the ankle joint thread wheel, respectively. At the instant the variable-cell mechanism changes from configuration 3 to configuration 1, the newly formed component II is separated and restored to the ankle joint gear shaft 222 and the ankle joint thread wheel shaft 225 through the ankle joint electromagnetic clutch 223.

[0078] The gait cycle is divided into four phases: stance flexion, stance extension, pre-swing, and swing. During the 0%–20% phase of the gait cycle (stance flexion), the exoskeleton provides no assistance, and the variable cellular mechanism is in configuration 1. During the 20%–40% phase (stance extension), the exoskeleton provides assistance to the knee joint, and the variable cellular mechanism is in configuration 2. During the 40%–60% phase (pre-swing), the exoskeleton provides assistance to the ankle joint, and the variable cellular mechanism is in configuration 3. During the 60%–100% phase (swing), the exoskeleton provides no assistance, and the variable cellular mechanism is in configuration 1.

[0079] like Figure 11The diagram shows the hardware structure of the knee and ankle assistive exoskeleton based on the principle of variable cell structure. The exoskeleton's control system mainly includes: a PC, a DC power supply, a portable power supply, heating wires, potentiometers, a foot pressure sensor, a microcontroller (including modules for serial communication, I2C communication, CAN communication, and WIFI), a motor controller, and an encoder. In this system, the PC acts as the host computer, responsible for collecting and processing relevant gait data and sending corresponding drive signals to the exoskeleton based on the analysis results. The microcontroller acts as middleware, connecting the hardware control modules to the PC to achieve data communication and command interaction between the exoskeleton system and the host computer; its operating voltage is 3.3V. The DC power supply powers the motor, electromagnetic clutch, and heating wires of the shape memory alloy springs via relays. The microcontroller and electromyography (EMG) signal acquisition device (attached to multiple muscle locations on the leg) are powered by the portable power supply. The potentiometers are used to measure the movement angles of the knee and ankle joints. The selected potentiometers are conductive plastic hollow potentiometers, with two potentiometers fixed to the ends of the knee and ankle axes respectively, rotating synchronously with the axes. Foot pressure sensors are embedded in the foot pressure sensing device 608, and are respectively located on the heel, toes, and inner and outer sides of the sole. Gait recognition is performed by the output signals of the pressure sensors at different locations. The motor encoder can measure the motor angle and motor angular velocity, and the heating wire is used to heat the two shape memory alloy springs.

[0080] The electrical functional components, their circuit connections, functional control, and sensor signal acquisition and processing methods mentioned above are all existing technologies and will not be described in detail here.

[0081] Please see Figure 12 The present invention also provides a control method for a knee-ankle assistive exoskeleton based on the principle of variable cell structure, comprising the following steps:

[0082] Step 1: The subject wears the knee and ankle assistive exoskeleton based on the principle of variable cell, turns on the power switch, and the control system begins initialization; the PC establishes a communication connection with the microcontroller, and the drive motor, electromagnetic clutch, and shape memory alloy (SMA) spring heating wire enter standby mode.

[0083] Step 2: The controller reads data from plantar pressure membrane sensors (heel, toes, inner / outer side of the foot) and knee / ankle potentiometer signals to divide the gait cycle (0% to 100%) in real time and determine whether the current stage is the standing or swinging stage.

[0084] Step 3: Based on the stage state of the leg, the control system adjusts the transmission configuration of the lumbar output knee joint transmission component and the lumbar output ankle joint transmission component to achieve automatic switching between knee joint assist mode, ankle joint assist mode and non-assist mode. The control system also adjusts the variable stiffness state of the knee joint variable stiffness mechanism to achieve dynamic adjustment of the knee joint support torque.

[0085] Specifically, if the gait cycle is between 20% and 40% (standing extension phase): the controller activates the knee joint assist mode, closes the knee joint electromagnetic clutch 209, and drives the drive motor 102 to rotate the camshaft 107 through the bevel gear pair; the knee joint disc cam 109 rotates, which in turn pulls the first Bowden rope group through the gear rack-pulley transmission, driving the knee joint output pulley 505 to rotate, providing knee joint extension assistance.

[0086] If the gait cycle is at 40%–60% (pre-swing phase): the controller switches to ankle joint assist mode, disconnects the knee joint electromagnetic clutch 209, and closes the ankle joint electromagnetic clutch 223; the drive motor 102 drives the camshaft 107 to rotate through the bevel gear pair; the ankle joint disc cam 110 rotates, and then pulls the second Bowden rope group through the gear rack-pulley transmission, driving the ankle joint output pulley 604 to provide ankle joint dorsiflexion assistance.

[0087] If the gait cycle is between 0% and 20% (standing flexion phase): The controller reads the angle signal from the knee potentiometer 503, combines it with the knee angle-torque curve, and controls the DC power supply to energize the heating wires of the shape memory alloy springs on both sides in a preset sequence; by adjusting the current state, the stiffness state of the shape memory alloy springs is changed, thereby cooperating with the eccentric linkage mechanism to drive the horizontal movement of the variable stiffness cam 406, dynamically adjusting the knee joint support torque to match the training intensity requirements of the human body.

[0088] If the gait cycle is between 60% and 100% (swing phase): the controller disconnects all electromagnetic clutches, the drive motor 102 stops outputting torque, and the knee and ankle joints move freely; the SMA spring on one side resets (heated and contracted), causing the variable stiffness cam 406 to disengage from the eccentric linkage mechanism, thereby reducing joint resistance.

[0089] Step 4: According to the gait cycle, the controller cyclically switches the transmission configuration of the lumbar output knee joint transmission component and the lumbar output ankle joint transmission component in real time, that is, it switches the configuration of the variable cell mechanism (knee / ankle assist mode) and the variable stiffness state of the knee joint variable stiffness mechanism in real time until the subject stops walking or triggers an emergency stop signal.

[0090] Step 5: Turn off the power switch and shut down the system. The subject removes the exoskeleton, and the system automatically saves the gait data (joint angles, muscle activity) to the PC for subsequent analysis.

[0091] This invention proposes a lower limb assistive exoskeleton system based on a variable-cell mechanism. It innovatively employs a single-motor driven collaborative assist design for both the knee and ankle joints, and uses an electromagnetic clutch to intelligently switch the driving paths of the knee and ankle joints at different gait stages, significantly reducing the overall weight of the exoskeleton. A variable-stiffness knee joint mechanism is designed, using a shape memory alloy spring as the stiffness adjustment element. Based on the human knee joint angle-torque biomechanical curve, a variable-stiffness cam converts knee joint torque changes into deformation control of the shape memory alloy spring, achieving adaptive switching between high stiffness during the standing phase and low stiffness during the swinging phase. A dual-cam collaborative drive mechanism is developed, designed based on gait analysis data. The profile curves of disc cams for the knee and ankle joints were designed, and by accurately fitting the joint angle change requirements, a single motor provided sequential assistance to the two joints. A centralized power layout scheme for the waist was proposed, which integrates the drive motor, reducer and transmission mechanism into the waist support, and transmits power to the distal joints through Bowden ropes. This not only ensures power transmission efficiency, but also effectively reduces the leg movement inertia, improving wearing comfort while ensuring the assistance effect. A multimodal gait recognition and control method was designed, which accurately divides the gait cycle phase by fusing data from the plantar pressure sensor array, joint potentiometer and motor encoder, and achieves precise matching of assistance timing with human movement intention.

[0092] The exoskeleton system of this invention achieves sequential driving of the knee and ankle joints by a single motor through a variable-cell mechanism, uses shape memory alloy springs to achieve adaptive adjustment of joint stiffness, and achieves precise gait phase recognition based on multi-sensor fusion. Ultimately, it achieves lightweight, high-energy-efficiency, and comfortable wear, making it widely applicable in rehabilitation training and industrial assistive technology. Compared with traditional solutions, this invention has the following advantages: reduced system weight and improved wearability; the motion conversion capability of the variable-cell mechanism enables a single motor to drive multiple joints, thereby reducing the number of motors, lowering the overall mass of the exoskeleton, and improving wearer comfort; optimized energy consumption and improved battery life; the single-motor drive scheme consumes less energy than multi-motor systems, thus extending the device's battery life and making it more suitable for long-term rehabilitation training or industrial work; simplified control strategy and improved system reliability; utilizing the motion characteristics of the variable-cell mechanism, the movement of the knee and ankle joints can be coordinated and controlled through a single drive source, reducing system control complexity and improving operational stability.

[0093] The exoskeleton design based on the principle of variability provides a new technological approach for the future development of lower limb assistive exoskeletons. It not only has broad application prospects in the field of rehabilitation medicine, but also possesses significant research value in industrial production, military assistance, and other fields. This invention will help promote the development of exoskeleton technology and provide new solutions for improving human-computer interaction capabilities and assistive efficiency.

[0094] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0095] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A knee-ankle assistive exoskeleton based on the principle of variable cell structure, characterized in that: It includes a control system, a waist drive mechanism, a waist transmission mechanism that is connected to the waist drive mechanism, a waist input knee joint transmission mechanism located below the waist transmission mechanism, a waist input ankle joint transmission mechanism that is rotatably connected to the lower end of the waist input knee joint transmission mechanism, and a foot pressure sensing device that is fixedly installed on the output end of the waist input ankle joint transmission mechanism. The waist transmission mechanism includes a waist output knee joint transmission component and a waist output ankle joint transmission component arranged in parallel. The output end of the waist output knee joint transmission component is connected to the input end of the waist input knee joint transmission mechanism through a first Bowden rope group, and the output end of the waist output ankle joint transmission component is connected to the input end of the waist input ankle joint transmission mechanism through a second Bowden rope group. The two output ends of the waist output knee joint transmission component and the waist output ankle joint transmission component output power according to three configuration cycle modes: "0-0→1-0→0-1→0-0...", where 0 indicates that the corresponding output end is in a no-power output state and 1 indicates that the corresponding output end is in a power output state. It also includes a knee joint variable stiffness mechanism, which includes a variable stiffness turntable coaxially arranged with the output end of the lumbar input knee joint transmission mechanism, a first variable stiffness connecting rod eccentrically hinged to the end face of the variable stiffness turntable, a second variable stiffness connecting rod hinged to the other end of the first variable stiffness connecting rod and vertically slidably connected to the fixing part of the lumbar input knee joint transmission mechanism, and a variable stiffness cam rotatably mounted on the fixing part of the lumbar input knee joint transmission mechanism and located directly above the top of the second variable stiffness connecting rod. The variable stiffness cam is a truncated cone structure with its axis horizontally arranged, and a first shape memory alloy spring and a second shape memory alloy spring are fixedly connected to its two end faces respectively. The top of the second variable stiffness connecting rod is embedded with a ball that can slide in contact with the surface of the variable stiffness cam.

2. The knee and ankle assistive exoskeleton based on the principle of variable cell structure according to claim 1, characterized in that: The waist drive mechanism includes a waist plate, a drive motor fixedly mounted on the waist plate, and a camshaft rotatably mounted on the waist plate and connected to the output end of the drive motor. A knee joint disc cam and an ankle joint disc cam are fixedly connected to the camshaft.

3. The knee and ankle assistive exoskeleton based on the principle of variable cell structure according to claim 2, characterized in that: The waist-mounted output knee joint transmission assembly includes a knee joint rack that movably engages with a knee joint disc cam, a knee joint gear that is rotatably mounted on the waist plate and meshes with the knee joint rack, and a knee joint input cable wheel that is rotatably mounted on the waist plate. One side of the shaft end of the knee joint input cable wheel and one side of the shaft end of the knee joint gear are connected by a knee joint electromagnetic clutch.

4. The knee and ankle assistive exoskeleton based on the principle of variable cell structure according to claim 3, characterized in that: The waist-input knee joint transmission mechanism includes a thigh rod, a knee joint output line wheel rotatably mounted at the bottom of the thigh rod, a calf rod fixedly connected to the shaft end of one side of the knee joint output line wheel, and the bottom end of the first Bowden rope assembly is fixedly connected to the knee joint output line wheel.

5. The knee and ankle assistive exoskeleton based on the principle of variable cell structure according to claim 4, characterized in that: The waist-mounted ankle joint transmission assembly includes an ankle joint rack that engages with an ankle joint disc cam, an ankle joint gear that is rotatably mounted on the waist plate and meshes with the ankle joint rack, and an ankle joint input line wheel that is rotatably mounted on the waist plate. One side of the shaft end of the ankle joint input line wheel and one side of the shaft end of the ankle joint gear are connected by an ankle joint electromagnetic clutch.

6. The knee and ankle assistive exoskeleton based on the principle of variable cell structure according to claim 5, characterized in that: The waist-input ankle joint transmission mechanism includes an ankle joint output line wheel rotatably mounted on the bottom of the lower leg bar, an ankle plate rotatably sleeved on the shaft end of the ankle joint output line wheel, the bottom end of the second Bowden rope group being fixedly connected to the ankle joint output line wheel, and the plantar pressure sensing device being fixedly connected to the ankle plate.

7. The knee and ankle assistive exoskeleton based on the principle of variable cell structure according to claim 6, characterized in that: A knee potentiometer is installed at the hinge point between the bottom of the thigh bar and the top of the calf bar, and an ankle potentiometer is installed at the hinge point between the bottom of the calf bar and the ankle plate.

8. A control method for a knee-ankle assistive exoskeleton based on the principle of variable cell structure, applied to the knee-ankle assistive exoskeleton based on the principle of variable cell structure as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Step 1: The subject wears the knee and ankle assistive exoskeleton based on the principle of cell variation. The system is powered on and initialized, and all functional components enter standby mode. Step 2: The control system reads plantar pressure data, knee joint rotation data, and ankle joint rotation data in real time to determine the current stage of the leg within the gait cycle; Step 3: Based on the stage state of the leg, the control system adjusts the transmission configuration of the lumbar output knee joint transmission component and the lumbar output ankle joint transmission component to achieve automatic switching between knee joint assist mode, ankle joint assist mode and non-assist mode. The control system also adjusts the variable stiffness state of the knee joint variable stiffness mechanism to achieve dynamic adjustment of the knee joint support torque. Step 4: According to the gait cycle, the control system cyclically switches the transmission configuration of the lumbar output knee joint transmission component and the lumbar output ankle joint transmission component, as well as the stiffness state of the knee joint variable stiffness mechanism, in real time until the subject stops walking or an emergency stop signal is triggered. Step 5: Shut down the system, remove the exoskeleton from the subject, and the system automatically saves the gait data to the PC for subsequent analysis.

9. The control method for the knee-ankle assistive exoskeleton based on the principle of variable cell structure according to claim 8, characterized in that: The gait cycle is divided into the standing flexion phase, the standing extension phase, the pre-swing phase, and the swing phase in sequence. During the standing flexion phase, the control system energizes the heating wire of the shape memory alloy spring in the knee joint variable stiffness mechanism. By adjusting the current, the stiffness of the shape memory alloy spring is changed, thereby driving the variable stiffness cam to move and dynamically adjusting the knee joint support torque. During the standing extension phase, the lumbar drive mechanism drives the lumbar input knee joint transmission mechanism to rotate through the lumbar output knee joint transmission assembly and the first Bowden rope assembly, providing knee extension assistance. During the pre-swing phase, the lumbar drive mechanism drives the lumbar input ankle drive mechanism to rotate through the lumbar output ankle joint drive assembly and the second Bowden rope assembly, providing ankle dorsiflexion assistance. During the swing phase, neither the waist drive mechanism nor the waist transmission mechanism is engaged, and the ankle joint transmission mechanism is in a free state.

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