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

Abstract

The invention discloses a knee-ankle power-assisted exoskeleton based on a metamorphic principle and a control method of the knee-ankle power-assisted exoskeleton. The knee-ankle power-assisted 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 plantar pressure sensing device. The waist transmission mechanism is a metamorphic mechanism and is in transmission connection with the input end of the waist input knee joint transmission mechanism and the input end of the waist input ankle joint transmission mechanism through two Bowden rope sets. And the metamorphic mechanism outputs power according to three preset configuration circulation modes. Automatic switching of different power assisting modes is achieved; and the output end of the waist input knee joint transmission mechanism is also provided with a knee joint variable stiffness mechanism. The metamorphic mechanism is adopted, the knee joint and the ankle joint are driven through a single motor, the overall weight of the exoskeleton is obviously reduced, and the power assisting efficiency is improved; intelligent switching of the exoskeleton in different gait stages can be achieved, and the power assisting mode can be dynamically adjusted.

Description

Technical Field

[0001] The present invention belongs to the technical field of exoskeleton robots, and particularly relates to a knee-ankle assistive exoskeleton based on the metamorphic cell principle and a control method thereof. Background Art

[0002] At present, with the aggravation of population aging and the rapid development of industrial automation, the rehabilitation needs of the disabled and the workload of manual laborers have become increasingly prominent. For the elderly, postoperative rehabilitation patients, and those with insufficient muscle strength, how to provide effective assistance to improve their walking ability and quality of life has become an important research direction in the field of rehabilitation medicine. At the same time, in industrial production and military operations, workers are engaged in high-intensity work for a long time, which is likely to cause muscle fatigue and even occupational injuries. Therefore, it is of great significance to study assistive equipment that can effectively reduce labor intensity and improve work efficiency. In this context, lower limb assistive exoskeletons, as a new type of mechatronic device, have received extensive attention and shown great application potential in rehabilitation medicine, assisted walking, and physical enhancement.

[0003] The core goal of lower limb assistive exoskeletons is to provide external assistance to help users complete lower limb movements such as walking and standing, and reduce muscle burden. Currently, lower limb assistive exoskeletons are mainly divided into two categories: single-joint drive exoskeletons and multi-joint independent drive exoskeletons. Single-joint drive exoskeletons usually use a single motor to drive a single joint. Although the structure is relatively simple, there are obvious limitations: they cannot achieve multi-joint collaborative assistance, resulting in unnatural gait assistance; the assistance efficiency is low, making it difficult to meet complex movement requirements. The other type is multi-joint independent drive exoskeletons. Although these exoskeletons can provide better assistance effects, they also have significant defects: they require multiple motors to drive different joints respectively, resulting in a large system weight and seriously affecting wearing comfort; the control systems of each joint are independent, with poor coordination and high energy consumption; the variable stiffness mechanism requires an additional drive unit, further increasing the system complexity. In addition, existing lower limb exoskeletons have deficiencies in adaptability: traditional transmission mechanisms cannot dynamically adjust the driving target joints according to the gait phase, resulting in inaccurate assistance timing; the stiffness adjustment mechanism has a slow response speed and is difficult to match the changing requirements of human joint stiffness in real time; the sensing system is single, and the gait recognition accuracy is limited, affecting the assistance effect. The metamorphic cell mechanism has broad application prospects in exoskeletons, but still faces challenges in actual engineering implementation, such as the complexity of mechanism design, control strategy optimization, and improvement of the overall system performance. Summary of the Invention

[0004] In view of the above technical problems in the prior art, the present invention provides a knee-ankle power-assisted exoskeleton based on the metamorphosis principle and its control method. Based on the characteristics of the metamorphosis mechanism, it is possible to use only one drive motor to drive the knee joint and ankle joint at the same time, effectively reducing the weight of the exoskeleton system and improving the power-assisted efficiency. In addition, the present invention combines intelligent control technologies such as gait recognition and sensor feedback to achieve intelligent switching of the exoskeleton in different gait stages, enabling it to dynamically adjust the power-assisted mode to adapt to different environments and user needs.

[0005] In order to solve the above technical problems, a technical solution adopted by the present invention is:

[0006] A knee-ankle power-assisted exoskeleton based on the metamorphosis principle, comprising a control system, a waist driving mechanism, a waist transmission mechanism connected to the waist driving mechanism, a waist input knee joint transmission mechanism located below the waist transmission mechanism, a waist input ankle joint transmission mechanism rotatably connected to the lower end of the waist input knee joint transmission mechanism, and a plantar pressure sensor fixedly arranged on the output end of the waist input ankle joint transmission mechanism;

[0007] The waist transmission mechanism comprises a waist output knee joint transmission assembly and a waist output ankle joint transmission assembly arranged in parallel, the output end of the waist output knee joint transmission assembly is connected to the input end of the waist input knee joint transmission mechanism via a first Bowden rope group, and the output end of the waist output ankle joint transmission assembly is connected to the input end of the waist input ankle joint transmission mechanism via 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 the three configuration cycle modes of "0-0→1-0→0-1→0-0...", where 0 indicates that the corresponding output end is in a non-power output state, and 1 indicates that the corresponding output end is in a power output state;

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

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

[0011] Furthermore, the lumbar output knee joint transmission assembly includes a knee joint rack movably cooperated with the knee joint disc cam, a knee joint gear rotatably mounted on the lumbar plate and meshing with the knee joint rack, and a knee joint input wire wheel rotatably mounted on the lumbar plate, and one side shaft end of the knee joint input wire wheel and one side shaft end of the knee joint gear are connected through a knee joint electromagnetic clutch.

[0012] Further, the waist input knee joint transmission mechanism includes a thigh rod, a knee joint output wire wheel rotatably installed at the bottom end of the thigh rod, a calf rod fixedly connected to the shaft end on one side of the knee joint output wire wheel, and the bottom end of the first Bowden cable group is fixedly connected to the knee joint output wire wheel.

[0013] Further, the knee joint variable stiffness mechanism includes a variable stiffness turntable coaxially arranged with the knee joint output wire wheel, 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 installed on the thigh rod and directly above the top end of the second variable stiffness connecting rod. The variable stiffness cam is a conical frustum structure with a horizontal axis, and a first shape memory alloy spring and a second shape memory alloy spring are respectively fixedly connected to its two side end faces. A ball that can slidably contact the surface of the variable stiffness cam is embedded at the top end of the second variable stiffness connecting rod.

[0014] Further, the waist output ankle joint transmission assembly includes an ankle joint rack that movably cooperates with the ankle joint disk cam, an ankle joint gear rotatably installed on the waist plate and meshing with the ankle joint rack, and an ankle joint input wire wheel rotatably installed on the waist plate. The shaft end on one side of the ankle joint input wire wheel and the shaft end on one side of the ankle joint gear are connected by an ankle joint electromagnetic clutch.

[0015] Further, the waist input ankle joint transmission mechanism includes an ankle joint output wire wheel rotatably installed at the bottom end of the calf rod, an ankle plate rotatably sleeved on the shaft end of the ankle joint output wire wheel, the bottom end of the second Bowden cable group is fixedly connected to the ankle joint output wire wheel, and the plantar pressure sensing device is fixedly connected to the ankle plate.

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

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

[0018] Step 1: The subject wears the knee-ankle assistive exoskeleton based on the metamorphic cell principle, the system is powered on and initialized, and each functional component enters the standby state;

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

[0020] Step 3: According to the stage state of the leg, the control system correspondingly adjusts the transmission configurations of the knee joint drive assembly output by the waist and the ankle joint drive assembly output by the waist to achieve automatic switching between the knee joint assistance mode, the ankle joint assistance mode, and the non-assistance mode. Moreover, the control system correspondingly 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 and real-time switches the transmission configurations of the knee joint drive assembly output by the waist and the ankle joint drive assembly output by the waist, as well as the variable stiffness state of the knee joint variable stiffness mechanism, until the subject stops walking or triggers an emergency stop signal;

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

[0023] Furthermore, the gait cycle is sequentially divided into a stance flexion phase, a stance extension phase, a pre-swing phase, and a swing phase;

[0024] In the stance flexion phase, the control system energizes the shape memory alloy spring heating wire in the knee joint variable stiffness mechanism, adjusts the stiffness of the shape memory alloy spring by regulating the current, and then drives the variable stiffness cam to move, dynamically adjusting the knee joint support torque;

[0025] In the stance extension phase, the waist drive mechanism drives the knee joint drive mechanism input by the waist to rotate through the knee joint drive assembly output by the waist and the first Bowden cable group, providing knee joint extension assistance;

[0026] In the pre-swing phase, the waist drive mechanism drives the ankle joint drive mechanism input by the waist to rotate through the ankle joint drive assembly output by the waist and the second Bowden cable group, providing ankle joint dorsiflexion assistance;

[0027] In the swing phase, neither the waist drive mechanism nor the waist transmission mechanism works, and the ankle joint drive 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 assistance exoskeleton designed by the present invention adopts a metamorphic mechanism, and drives the knee and ankle joints by a single motor, significantly reducing the overall weight of the exoskeleton, improving the comfort and portability of the wearer, and being applicable to medical rehabilitation and industrial assistance scenarios.

[0030] 2. By dynamically switching the transmission path (knee / ankle joint) through an electromagnetic clutch, the configuration reconstruction of the metamorphic mechanism is realized, enabling a single motor to drive the knee joint and the ankle joint respectively in different gait phases, reducing the system complexity and energy consumption, and at the same time ensuring the accuracy and coordination of assistance.

[0031] 3. The variable stiffness mechanism using a shape memory alloy spring can automatically enhance the knee joint stiffness during the stance phase to support the body weight and reduce the stiffness during the swing phase to reduce the movement resistance, effectively reducing the energy consumption of the wearer and improving the naturalness of walking.

[0032] 4. The assistive design based on a disk cam optimizes the cam profile by fitting the angle-torque curves of the knee joint and the ankle joint, ensuring a high match between the assistive torque and the human gait requirements, avoiding movement interference, and improving the assistive efficiency.

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

[0034] Figure 1 It is a schematic diagram of the overall structure of the knee-ankle assistive exoskeleton based on the metamorphic cell principle of the present invention;

[0035] Figure 2 It is a schematic diagram of the structure of the waist driving mechanism;

[0036] Figure 3 It is a schematic diagram of the structure of the waist output knee joint transmission component;

[0037] Figure 4 It is a schematic diagram of the structure of the waist input knee joint transmission mechanism;

[0038] Figure 5 It is an exploded schematic diagram of the structure of the waist input knee joint transmission mechanism;

[0039] Figure 6 It is a schematic diagram of the structure of the knee joint variable stiffness mechanism;

[0040] Figure 7 It is an exploded schematic diagram of the structure of the knee joint variable stiffness mechanism;

[0041] Figure 8 It is a schematic diagram of the structure of the waist output ankle joint transmission component;

[0042] Figure 9 It is a schematic diagram of the structure of the waist input ankle joint transmission mechanism;

[0043] Figure 10 It is an exploded schematic diagram of the structure of the waist input ankle joint transmission mechanism;

[0044] Figure 11 It is a hardware structure block diagram of the knee-ankle assistive exoskeleton based on the metamorphic cell principle of the present invention;

[0045] Figure 12 This is a control flow chart of the knee-ankle assisted exoskeleton based on the metamorphosis principle of the present invention. DETAILED DESCRIPTION

[0046] The preferred embodiments of the present invention are described in detail below in conjunction with 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 making a clearer and more definite definition of the protection scope of the present invention.

[0047] It should be noted that when a component is referred to as being "mounted on" another component, it may be directly on the other component or there may be a central component. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be a central component at the same time. When a component is considered to be "fixed to" another component, it may be directly fixed on the other component or there may be a central component at the same time.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "or / and" used herein includes any and all combinations of one or more of the related listed items.

[0049] See attached Figure 1 A knee-ankle power-assisted exoskeleton based on the metamorphosis principle includes a control system, a waist driving mechanism 10, a waist transmission mechanism 20 connected to the waist driving mechanism 10, a waist input knee joint transmission mechanism 50 located below the waist transmission mechanism 20, a waist input ankle joint transmission mechanism 60 rotatably connected to the lower end of the waist input knee joint transmission mechanism 50, and a plantar pressure sensor fixedly arranged on the output end of the waist input ankle joint transmission mechanism 60. The waist transmission mechanism 20 includes a waist output knee joint transmission assembly and a waist output ankle joint transmission assembly arranged in parallel, the output end of the waist output knee joint transmission assembly is connected to the input end of the waist input knee joint transmission mechanism 50 through a first Bowden rope group, and the output end of the waist output ankle joint transmission assembly is connected to the input end of the waist input ankle joint transmission mechanism 60 through a second Bowden rope group. The two output ends of the waist output knee joint transmission assembly and the waist output ankle joint transmission assembly output power according to the three configuration cycle modes of "0-0→1-0→0-1→0-0...", where 0 indicates that the corresponding output end is in a non-power output state, and 1 indicates that the corresponding output end is in a power output state. A knee joint variable stiffness mechanism 40 is also provided on the output end of the waist input knee joint transmission mechanism 50.

[0050] The following is a detailed description of the specific structural composition and working principle of each functional part of the knee-ankle assisted exoskeleton based on the metamorphosis principle.

[0051] like Figure 2 As shown, the waist driving mechanism 10 includes a waist plate 101, a driving motor 102 fixedly mounted on the waist plate 101, and a camshaft 107 rotatably mounted on the waist plate 101 and transmission-connected to the output end of the driving motor 102, and the camshaft 107 is respectively fixedly connected with a knee joint disc cam 109 and an ankle joint disc cam 110. Specifically, the waist plate 101 is a hard thin plate, and its width refers to the waist width of an average adult. Both ends are provided with strap fixing openings, and the waist plate 101 is fixed to the waist of the rehabilitation trainee by the strap. The output shaft end of the driving motor 102 is fixedly connected with a planetary reducer 103, and the planetary reducer 103 is fixedly set on the top of the side of the waist plate 101 through a driving motor support 104, so that its output shaft is set vertically downward and the output shaft end is fixedly connected to the first bevel gear 105 through a key. The camshaft 107 is horizontally arranged below the first bevel gear 105, and its shaft end is fixedly connected to the second bevel gear 106 meshing with the first bevel gear 105 through a key. The camshaft 107 is rotatably mounted on the camshaft support 108 through a bearing, and the camshaft support 108 is fixedly connected to the side of the waist plate 101 through bolts. The knee joint disc cam 109 and the ankle joint disc cam 110 are respectively located on both sides of the camshaft support 108 and are respectively fixedly mounted on the camshaft 107 through keys.

[0052] In this way, after the driving motor 102 starts working, it drives the first bevel gear 105 to rotate through the planetary gear reducer 103, and the first bevel gear 105 drives the second bevel gear 106 to rotate through meshing transmission, and then transmits 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 movably matched with the knee joint disc cam 109, a knee joint gear 207 rotatably mounted on the lumbar plate 101 and meshing with the knee joint rack 202, and a knee joint input pulley 212 rotatably mounted on the lumbar plate 101, and one side shaft end of the knee joint input pulley 212 and one side shaft end of the knee joint gear 207 are connected via 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. A knee joint disc cam roller 201 is arranged in the cam guide groove. A smooth rod bolt is slidably sleeved in the knee joint disc cam roller 201, and the end of the smooth rod bolt is threadedly connected to the top right side of the knee joint rack 202. In this way, a cam push rod transmission mechanism is formed between the knee joint rack 202 and the knee joint disc cam 109. A knee joint slide rail support 206 is fixedly connected to the side surface of the waist plate 101 by bolts. A vertically arranged knee joint slide rail 205 is fixedly connected to the side surface of the knee joint slide rail support 206 by bolts. A knee joint slide block 204 is slidably connected to the knee joint slide rail 205. A knee joint rack slide block connecting member 203 is fixedly connected to the side surface of the knee joint slide block 204 by bolts. The side surface of the knee joint rack 202 is attached to the side surface of the knee joint rack slide block connecting member 203 and fixedly connected by bolts. In this way, the knee joint rack 202 is vertically arranged and can only move vertically.

[0055] Knee joint gear shaft supports 210 and knee joint wire wheel shaft supports 213 are respectively fixedly connected to the side surface of the waist plate 101 by bolts. The knee joint gear 207 is fixedly connected to the knee joint gear shaft 208 by a key. The right end of the knee joint gear shaft 208 is rotatably installed on the knee joint gear shaft support 210 through a bearing. The knee joint input wire wheel 212 is fixedly connected to the knee joint wire wheel shaft 211 by a key. The left end of the knee joint wire wheel shaft 211 is rotatably installed on the knee joint wire wheel shaft support 213 through a bearing. The knee joint electromagnetic clutch 209 is located between the knee joint gear 207 and the knee joint input wire wheel 212. The end of the right side part of it is fixedly connected to the left end of the knee joint gear shaft 208 by a key, and the end of the left side part of it is fixedly connected to the right end of the knee joint wire wheel shaft 211 by a key. In this way, after the knee joint electromagnetic clutch 209 is powered on, the knee joint gear shaft 208 and the knee joint wire wheel shaft 211 are in transmission connection, and the rotational power input from the knee joint gear 207 can be synchronously rotated and output by the knee joint input wire wheel 212, that is, corresponding to the above state "1"; after the knee joint electromagnetic clutch 209 is powered off, the knee joint gear shaft 208 and the knee joint wire wheel shaft 211 are in a non-connected state, the knee joint gear 207 idles, and the knee joint input wire wheel 212 has no power input and output, that is, corresponding to the above state "0".

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

[0057] In this way, when the knee joint disc cam 109 rotates forward / backward, the linear lifting / lowering movement of the knee joint rack 202 is driven through cam transmission. The knee joint rack 202 drives the knee joint gear 207 to rotate forward / backward, and then drives the knee joint gear shaft 208 to rotate synchronously in the same direction. Then, the knee joint wire wheel shaft 211 is driven to rotate through the knee joint electromagnetic clutch 209, and the knee joint wire wheel shaft 211 drives the knee joint input wire wheel 212 to rotate synchronously in the same direction. When the knee joint input wire wheel 212 rotates forward, the first Bowden cable 31 pulls the knee joint output wire wheel 505 to rotate synchronously forward. When the knee joint input wire wheel 212 rotates backward, the second Bowden cable 32 pulls the knee joint output wire wheel 505 to rotate synchronously backward, thereby realizing flexible connection and power transmission in both forward and reverse directions.

[0058] As Figure 4 and Figure 5 shown, the lumbar input knee joint transmission mechanism 50 includes a thigh rod 506, a knee joint output wire wheel 505 rotatably installed at the bottom end of the thigh rod 506, and a calf rod 507 fixedly connected to one side shaft end of the knee joint output wire wheel 505. The bottom end of the first Bowden cable group is fixedly connected to the knee joint output wire wheel 505. Specifically, the thigh rod 506 is a rigid long strip plate member made of lightweight carbon fiber material. An arc-shaped thigh fixing member 508 is provided on one side of its top end. Adhesive straps are bound to both ends of the thigh fixing member 508. The thigh rod 506 and the thigh fixing member 508 can be fixed to the thigh part of the rehabilitation trainer through the straps. A positioning block is fixedly provided in the middle of the thigh fixing member 508, and a number of rows of positioning holes are opened in the upper part of the thigh rod 506. Bolts pass through the positioning holes and are threadedly connected to the positioning block, thereby fixing the positioning block on the thigh rod 506. By adjusting the positioning holes matched with the bolts, the fixing position of the positioning block and the thigh fixing member 508 on the thigh rod 506 can be adjusted, so as to adjust the distance from the thigh fixing member 508 to the rotation connection position (knee joint) of the thigh rod 506 and the calf rod 507 to meet the binding needs of different leg lengths of different people.

[0059] The knee joint output wire wheel 505 is fixed on the knee axis 502 by a key. The right end of the knee axis 502 is rotatably installed at the bottom end of the thigh rod 506 through a bearing. The calf rod 507 is also a rigid long strip plate member made of lightweight carbon fiber material. Its top end is fixedly connected to the right end of the knee axis 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 fixedly connected by bolts with an output end knee joint Bowden cable guiding device 501 directly above the knee joint output wire wheel 505. The bottom ends of the first Bowden cable 31 and the second Bowden cable 32 respectively pass through two positioning holes on the output end knee joint Bowden cable guiding device 501, so that the two Bowden cables are respectively located on both sides of the axis of the knee joint input wire wheel 212, and the bottom ends are respectively fixedly connected to both ends of the diameter line of the knee joint output wire wheel 505, thus providing pulling force for the forward / backward rotation of the knee joint output wire wheel 505 respectively.

[0060] To detect the angular information at the knee joint in real time to obtain the relative position relationship between the calf rod 507 and the thigh rod 506, preferably, a knee joint potentiometer 503 is provided at the hinge joint between the bottom end of the thigh rod 506 and the top end of the calf rod 507 at the knee joint. Specifically, a knee joint potentiometer bracket 504 is fixedly connected to the left side of the top end of the calf rod 507, and the left folding plate of the knee joint potentiometer bracket 504 is sleeved outside the left end of the knee axis 502. The fixed end of the knee joint potentiometer 503 is fixedly connected to the side surface of the output end knee joint Bowden cable guiding 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 axis 502.

[0061] In this way, the first Bowden cable 31 / second Bowden cable 32 passing through the output end knee joint Bowden cable guiding device 501 drives the knee joint output wire wheel 505 to rotate forward / backward. The knee joint output wire wheel 505 drives the knee axis 502 to rotate, thereby driving the calf rod 507 to rotate to realize the rotation of the knee joint. The fixed end of the knee joint potentiometer 503 is relatively fixed to the thigh rod 506 through the output end knee joint Bowden cable guiding device 501, and the rotating shaft end of the knee joint potentiometer 503 is relatively fixed to the calf rod 507 through the knee axis 502. Therefore, the knee joint potentiometer 503 can detect the relative rotation angle between the calf rod 507 and the thigh rod 506 in real time.

[0062] Such as Figure 6 and Figure 7As shown in the figure, the knee joint variable stiffness mechanism 40 includes a variable stiffness turntable 401 coaxially arranged with the knee joint output wire wheel 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 directly above the top end of the second variable stiffness connecting rod 403. The variable stiffness cam 406 is a frustum of a cone structure with a horizontal axis. A first shape memory alloy spring 407 and a second shape memory alloy spring 408 are respectively fixedly connected to its two side end faces. A ball 405 that can slidably contact the surface of the variable stiffness cam 406 is embedded at the top end of the second variable stiffness connecting rod 403.

[0063] Specifically, the variable stiffness turntable 401 is fixed on the knee shaft 502 by a key. A polished rod bolt is threadedly connected to the edge of one side 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 polished 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 surface of the thigh rod 506 by a bolt. A vertically arranged guide hole matching the cross-sectional shape of the second variable stiffness connecting rod 403 is opened in the left end of the variable stiffness guide support 404. 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 form an eccentric connecting rod transmission mechanism. The ball 405 is embedded in a socket provided at one end of the second variable stiffness connecting rod 403 close to the variable stiffness cam 406 (i.e., the top end of the second variable stiffness connecting rod 403). A first variable stiffness support 410 and a second variable stiffness support 411 are respectively fixedly connected to the left and right sides of the middle part of the side surface of the thigh rod 506 by bolts. A horizontally arranged variable stiffness camshaft 409 is fixedly connected between the ends of the first variable stiffness support 410 and the second variable stiffness support 411 by bolts. The variable stiffness cam 406 is movably sleeved on the variable stiffness camshaft 409 and can horizontally move on the variable stiffness camshaft 409. The first shape memory alloy spring 407 and the second shape memory alloy spring 408 are respectively sleeved on the variable stiffness camshaft 409 and are respectively located on the left and right sides of the variable stiffness cam 406.

[0064] Thus, when the knee axis 502 rotates forward, it drives the variable stiffness turntable 401 to rotate synchronously and in the same direction. The variable stiffness turntable 401 drives the first variable stiffness connecting rod 402 to push the second variable stiffness connecting rod 403 to move vertically upward. 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 mutual contact force pushes the variable stiffness cam 406 to move horizontally on the variable stiffness camshaft 409 (move toward the large radius end face of the frustum, that is, move to the left as shown in Figure 6 and Figure 7 ), resulting in the deformation of the first shape memory alloy spring 407 on the left side due to being squeezed by the variable stiffness cam 406, thereby realizing the automatic adjustment of variable stiffness.

[0065] Variable stiffness principle: At the beginning of the gait, the power supply supplies power to the heating wire wound around the second shape memory alloy spring 408 to keep it in an inextensible natural length state. Then the first shape memory alloy spring 407 is in a stretched state. At this time, the variable stiffness cam 406 is at the rightmost position, and the ball 405 is directly below the lowest end of the lowest side generatrix of the conical surface of the variable stiffness cam 406 (the leftmost end of the conical surface). During the first double-support phase of the gait, when the joint angle of the knee joint increases to 8°, through the transmission of the eccentric link transmission mechanism, the ball 405 vertically rises to contact the lowest end of the lowest side generatrix of the conical surface of the variable stiffness cam 406, and the heating wire wound around the second shape memory alloy spring 408 is powered off, and the second shape memory alloy spring 408 returns to a length extensible state. At this time, the joint angle of the knee joint continues to increase, and the ball 405 continues to squeeze the conical surface of the variable stiffness cam 406, causing the variable stiffness cam 406 to continue to move to the left. When the joint angle of the knee joint increases to 15°, the variable stiffness cam 406 horizontally moves to the leftmost side, and the ball 405 contacts the edge critical point position of the highest end of the lowest side generatrix of the conical surface of the variable stiffness cam 406 (the rightmost end of the conical surface). At this time, the length of the first shape memory alloy spring 407 returns to the inextensible natural state, and the power supply supplies power to the heating wire wound around the first shape memory alloy spring 407 to keep it in an inextensible natural length state, while the second shape memory alloy spring 408 is in a stretched state. When the joint angle of the knee joint continues to increase, the ball 405 continues to move vertically upward and disengages from the conical surface and does not contact the variable stiffness cam 406. During the swing phase of the gait cycle, the variable stiffness turntable 401 rotates in the reverse direction, and the corresponding joint angle of the knee joint gradually decreases. Through the transmission of the eccentric link transmission mechanism, the ball 405 vertically descends and resets, and at this time the variable stiffness cam 406 remains at the leftmost position. When the joint angle is less than 8°, the heating wire wound around the first shape memory alloy spring 407 is powered off, and the first shape memory alloy spring 407 returns to a length extensible state. The power supply supplies power to the heating wire wound around the second shape memory alloy spring 408 to make it contract to the natural length state and at the same time drive the variable stiffness cam 406 to move to the right and reset. During the movement, it will not contact the ball 405, preparing for the start of the next gait cycle.

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

[0067] Specifically, a cam guide groove is formed in the right end face of the ankle joint disc cam 110. An ankle joint disc cam roller 215 is arranged in the cam guide groove. A polished rod bolt is slidably sleeved in the ankle joint disc cam roller 215. The end of the polished rod bolt is threadedly connected to the top left side of the ankle joint rack 216. In this way, a cam ejector rod transmission mechanism is formed between the ankle joint rack 216 and the ankle joint disc cam 110. An ankle joint slide rail support 220 is fixedly connected to the side surface of the lumbar plate 101 by bolts. A vertically arranged ankle joint slide rail 219 is fixedly connected to the side surface 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 connecting member 217 is fixedly connected to the side surface of the ankle joint slider 218 by bolts. The side surface of the ankle joint rack 216 is attached to the side surface of the ankle joint rack slider connecting member 217 and fixedly connected by bolts. In this way, the ankle joint rack 216 is vertically arranged and can only move vertically.

[0068] An ankle joint gear shaft support 224 and an ankle joint wire wheel shaft support 227 are respectively fixedly connected to the side surface of the lumbar plate 101 by bolts. The ankle joint gear 216 is fixedly connected to the ankle joint gear shaft 222 by a key. The left end of the ankle joint gear shaft 222 is rotatably installed on the ankle joint gear shaft support 224 through a bearing. The ankle joint input wire wheel 226 is fixedly connected to the ankle joint wire wheel shaft 225 by a key. The right end of the ankle joint wire wheel shaft 225 is rotatably installed on the ankle joint wire wheel shaft support 227 through a bearing. The ankle joint electromagnetic clutch 223 is located between the ankle joint gear 216 and the ankle joint input wire wheel 226. The end of the left side part of it is fixedly connected to the right end of the ankle joint gear shaft 222 by a key, and the end of the right side part of it is fixedly connected to the left end of the ankle joint wire wheel shaft 225 by a key. In this way, after the ankle joint electromagnetic clutch 223 is powered on, the ankle joint gear shaft 222 and the ankle joint wire wheel shaft 225 are in transmission connection, and the rotational power input from the ankle joint gear 216 can be synchronously rotated and output by the ankle joint input wire wheel 226, that is, corresponding to the above state "1"; after the ankle joint electromagnetic clutch 223 is powered off, the ankle joint gear shaft 222 and the ankle joint wire wheel shaft 225 are in a non-connected state, the ankle joint gear 216 idles, and there is no power input and output for the ankle joint wire wheel shaft 225, that is, corresponding to the above state "0".

[0069] Meanwhile, a input end ankle Bowden cable guiding device 228, which is located directly below the ankle joint input wire wheel 226, is fixedly connected to the side surface of the lumbar plate 101 by bolts. The second Bowden cable group consists of a third Bowden cable 33 and a fourth Bowden cable 34. The two Bowden cables respectively pass through two positioning holes on the input end ankle Bowden cable guiding device 228, so that the two Bowden wires are respectively located on both sides of the axis of the ankle joint input wire wheel 226. The top ends of the two Bowden wires are respectively fixedly connected to both ends of the diameter line of the ankle joint input wire wheel 226, and the bottom ends are respectively fixedly connected to both ends of the diameter line of the ankle joint output wire wheel 604 at the input end of the lumbar input ankle transmission mechanism 60.

[0070] In this way, when the ankle joint disc cam 110 rotates forward / backward, the linear up / down movement of the ankle joint rack 216 is driven through cam transmission. The ankle joint rack 216 drives the ankle joint gear 216 to rotate forward / backward, and then drives the ankle joint gear shaft 222 to rotate synchronously in the same direction. Then, the ankle joint wire wheel shaft 225 is driven to rotate through the ankle joint electromagnetic clutch 223, and the ankle joint wire wheel shaft 225 drives the ankle joint input wire wheel 226 to rotate synchronously in the same direction. When the ankle joint input wire wheel 226 rotates forward, the third Bowden cable 33 pulls the ankle joint output wire wheel 604 to rotate synchronously forward. When the ankle joint input wire wheel 226 rotates backward, the fourth Bowden cable 34 pulls the ankle joint output wire wheel 604 to rotate synchronously backward, so as to realize the flexible connection and power transmission in both forward and reverse directions.

[0071] As Figure 9 and Figure 10 shown, the lumbar input ankle transmission mechanism 60 includes an ankle joint output wire wheel 604 rotatably installed at the bottom end of the calf rod 507, and an ankle plate 607 rotatably sleeved on the shaft end of the ankle joint output wire wheel 604. The bottom end of the second Bowden cable group is fixedly connected to the ankle joint output wire wheel 604. Specifically, the calf rod 507 is a rigid long strip plate member, and arc-shaped first calf fixing members 609 and second calf fixing members 610, which are distributed up and down, are respectively arranged at the middle side position of the calf rod 507. Adhesive straps are bound to both ends of the first calf fixing member 609 and the second calf fixing member 610. The calf rod 507 and the two calf fixing members can be fixed to the calf part of the rehabilitation trainer through the straps. Positioning blocks are fixedly arranged in the middle of the two calf fixing members, and a plurality of rows of positioning holes are opened in the middle of the calf rod 507. Bolts pass through the positioning holes and are threadedly connected to the positioning blocks, so as to fix the two positioning blocks on the calf rod 507. By adjusting the positioning holes matched with the bolts, the fixing positions of the positioning blocks and the two calf fixing members on the calf rod 507 can be adjusted, so as to adjust the relative positions between the two calf fixing members and the distance from the lower second calf fixing member 610 to the rotation connection position (ankle joint) of the calf rod 507 and the ankle plate 607, so as to meet the binding needs of different people with different calf lengths.

[0072] The ankle joint output wire wheel 604 is fixed on the ankle axis 605 by a key. The middle part of the ankle axis 605 is rotatably installed at the bottom end of the calf rod 507 through a bearing. An ankle plate connecting piece 606 is sleeved on the outer side of the right end of the ankle axis 605 by a key. A connecting plate perpendicular to it is fixedly arranged on the side surface of the ankle plate 607. The connecting plate is fixedly connected to the right side surface of the ankle plate connecting piece 606 by bolts, so that the ankle plate 607 and the calf rod 507 can rotate relative to each other, corresponding to the leg ankle joint. The bottom end of the calf rod 507 is fixedly connected by bolts with an output end ankle Bowden cable guiding device 601 located directly above the ankle joint output wire wheel 604. The bottom ends of the third Bowden cable 33 and the fourth Bowden cable 34 respectively pass through two positioning holes on the output end ankle Bowden cable guiding device 601, so that the two Bowden wires are respectively located on both sides of the axis of the ankle joint output wire wheel 604, and the bottom ends are respectively fixedly connected to both ends of the diameter line of the ankle joint output wire wheel 604, thereby respectively providing pulling force for the forward / backward rotation of the ankle joint output wire wheel 604.

[0073] The main body part of the plantar pressure sensing device 608 is an L-shaped plate member. Its top vertical section is fixedly connected to the ankle plate 607 by bolts, and a number of rows of bolt connection holes are arranged vertically on the side surface of its top vertical section. A number of columns of positioning holes are arranged on the side surface of the ankle plate 607. By adjusting the pairing positions of the bolt connection holes and the positioning holes, the horizontal and vertical relative positions of the plantar pressure sensing device 608 on the ankle plate 607 can be adjusted to meet the usage requirements of trainers with different ankle sizes.

[0074] To detect the angular information at the ankle joint in real time to obtain the relative position relationship between the ankle plate 607 and the calf rod 507, preferably, an ankle joint potentiometer 602 is provided at the ankle joint, that is, at the hinge joint between the bottom end of the calf rod 507 and the ankle plate 607. Specifically, an ankle joint potentiometer bracket 603 is fixedly connected to the side surface of the ankle plate 607 by bolts. The left folding plate of the ankle joint potentiometer bracket 603 is sleeved on the outer side of the left end of the ankle axis 605. The fixed end of the knee joint potentiometer 503 is fixedly connected to the side surface of the output end ankle Bowden cable guiding device 601 by bolts. The rotating shaft end of the ankle joint potentiometer 602 is inserted into the left end face of the ankle axis 605.

[0075] In this way, the third Bowden cable 33 / fourth Bowden cable 34 passing through the output end ankle Bowden cable guiding device 601 drives the ankle joint output wire wheel 604 to rotate forward / backward. The ankle joint output wire wheel 604 drives the ankle axis 605 to rotate, thereby driving the ankle plate 607 to rotate to realize the rotation of the ankle joint. The fixed end of the ankle joint potentiometer 602 is relatively fixed to the calf rod 507 through the output end ankle Bowden cable guiding device 601, and the rotating shaft end of the ankle joint potentiometer 602 is relatively fixed to the ankle plate 607 through the ankle axis 605. Therefore, the ankle joint potentiometer 602 can detect the relative rotation angle between the ankle plate 607 and the calf rod 507 in real time.

[0076] Metamorphosis principle in waist transmission mechanism 20: In the exoskeleton, there are 8 components constituting the metamorphosis mechanism, namely, knee joint gear shaft 208, knee joint wire pulley shaft 211, knee joint input wire pulley 212, knee joint electromagnetic clutch 209, ankle joint gear shaft 222, ankle joint wire pulley shaft 225, ankle joint input wire pulley 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 powered, corresponding to the aforementioned "0-0" mode state; configuration 2 is that knee joint electromagnetic clutch 209 is powered, and ankle joint electromagnetic clutch 223 is not powered, corresponding to the aforementioned "1-0" mode state; configuration 3 is that knee joint electromagnetic clutch 209 is not powered, and ankle joint electromagnetic clutch 223 is powered, corresponding to the aforementioned "0-1" mode state.

[0077] When the metamorphosis 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 line wheel shaft 211 and the ankle joint line wheel shaft 225 through the knee joint electromagnetic clutch 209 and the ankle joint electromagnetic clutch 223, resulting in the inability to transmit the movement. At the moment when the metamorphic mechanism changes from configuration 1 to configuration 2, the knee joint gear shaft 208 and the knee joint line wheel shaft 211 are consolidated to form a new component I through the knee joint electromagnetic clutch 209, and form a rotational pair constraint with the knee joint rack 202 and the knee joint input line wheel 212 respectively; at the moment when the metamorphic mechanism changes from configuration 2 to configuration 3, the consolidated new component I is separated and restored to the knee joint gear shaft 208 and the knee joint line wheel shaft 211 through the knee joint electromagnetic clutch 209, and at the same time, the ankle joint gear shaft 222 and the ankle joint line wheel shaft 225 are consolidated to form a new component II through the ankle joint electromagnetic clutch 223, and form a rotational pair constraint with the ankle joint rack 216 and the ankle joint line wheel respectively; at the moment when the metamorphic mechanism changes from configuration 3 to configuration 1, the consolidated new component II is separated and restored to the ankle joint gear shaft 222 and the ankle joint line wheel shaft 225 through the ankle joint electromagnetic clutch 223.

[0078] The gait cycle is divided into the stance flexion phase, stance extension phase, pre-swing phase and swing phase. In the 0% to 20% phase of the gait cycle, i.e. the stance flexion phase, the exoskeleton does not provide assistance, and the metamorphosis mechanism is in configuration 1; in the 20% to 40% phase of the gait cycle, i.e. the stance extension phase, the exoskeleton provides assistance to the knee joint, and the metamorphosis mechanism is in configuration 2; in the 40% to 60% phase of the gait cycle, i.e. the pre-swing phase, the exoskeleton provides assistance to the ankle joint, and the metamorphosis mechanism is in configuration 3; in the 60% to 100% phase of the gait cycle, i.e. the swing phase, the exoskeleton does not provide assistance, and the metamorphosis mechanism is in configuration 1.

[0079] like Figure 11As shown in the figure, it is a block diagram of the hardware structure of the knee-ankle assistive exoskeleton based on the metamorphic cell principle of the present invention. The control system of the exoskeleton mainly includes: a PC, a DC power supply, a portable mobile power supply, a heating wire, a potentiometer, a sole pressure sensor, a single-chip microcomputer (including: serial communication, I2C communication, CAN communication, WIFI and other modules), a motor controller and an encoder. In this system, the PC acts as the host control unit, responsible for collecting and processing the relevant data of the walking gait, and sending the corresponding driving signals to the exoskeleton according to the analysis results; the single-chip microcomputer acts as the middleware, responsible for connecting the hardware control module with the PC to realize the data communication and instruction interaction between the exoskeleton system and the host computer, and its working voltage is 3.3V. The DC power supply supplies power to the motor, electromagnetic clutch and heating wire of the shape memory alloy spring through a relay, and the single-chip microcomputer and the electromyogram signal collector (pasted at multiple muscle positions on the leg) are powered by the portable mobile power supply. The potentiometer is used to measure the movement angles of the knee joint and the ankle joint. The selected potentiometer is a conductive plastic hollow potentiometer, and the two potentiometers are respectively fixed at the ends of the knee axis and the ankle axis and rotate synchronously with the axis. The sole pressure sensor is embedded in the sole pressure sensing device 608 and is arranged at the heel, toe, inner and outer sides of the sole respectively. The gait is recognized by the output signals of the pressure sensors at different positions. The motor encoder can measure the motor angle and the motor angular velocity, and the heating wire is used to heat the two shape memory alloy springs.

[0080] The above-mentioned electrical functional components and their circuit connections, function controls, methods for collecting and processing sensor signals, etc. are all prior arts and will not be elaborated in detail here.

[0081] Please refer to Figure 12 , the present invention also provides a control method for a knee-ankle assistive exoskeleton based on the metamorphic cell principle, including the following steps:

[0082] Step 1: The subject wears the knee-ankle assistive exoskeleton based on the metamorphic cell principle, turns on the power switch, and the control system starts to initialize; the PC establishes a communication connection with the single-chip microcomputer, and drives the motor, electromagnetic clutch, and shape memory alloy (SMA) spring heating wire to enter the standby state.

[0083] Step 2: The controller divides the gait cycle (0% - 100%) in real time by reading the data of the sole pressure thin film sensor (heel, toe, inner / outer side of the sole) and the potentiometer signals of the knee joint / ankle joint, and judges whether it is in the standing phase or the swing phase.

[0084] Step 3: According to the stage state of the legs, the control system adjusts the transmission configuration of the waist output knee joint transmission component and the waist output ankle joint transmission component accordingly to achieve automatic switching between the knee joint assistance mode, ankle joint assistance mode and non-assistance mode, and the control system adjusts the variable stiffness state of the knee joint variable stiffness mechanism accordingly to achieve dynamic adjustment of the knee joint support torque.

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

[0086] If the gait cycle is at 40% to 60% (pre-swing stage): the controller switches to the ankle joint assistance 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-wire pulley transmission, driving the ankle joint output wire pulley 604 to provide ankle joint dorsiflexion assistance.

[0087] If the gait cycle is between 0% and 20% (stance flexion stage): the controller reads the angle signal of the knee joint potentiometer 503, and combines the knee joint angle-torque curve to control the DC power supply to energize the heating wires of the shape memory alloy springs on both sides in a preset order; the stiffness state of the shape memory alloy spring is changed by adjusting the current state, thereby cooperating with the eccentric connecting rod mechanism to drive the horizontal movement of the variable stiffness cam 406, and 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 stage): the controller disconnects all electromagnetic clutches, the drive motor 102 stops outputting torque, and the knee and ankle joints move freely; the unilateral SMA spring is reset (heated and contracted), so that the variable stiffness cam 406 is out of contact with the eccentric connecting rod mechanism, thereby reducing joint resistance.

[0089] Step 4: According to the gait cycle, the controller cyclically switches the transmission configuration of the waist output knee joint transmission component and the waist output ankle joint transmission component in real time, that is, switches the variable cell mechanism configuration (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, shut down the system, and the subject takes off the exoskeleton. The system automatically saves the gait data (joint angles, muscle activity) to the PC for subsequent analysis.

[0091] The present invention proposes a lower limb assistive exoskeleton system based on a metamorphic mechanism, innovatively adopting a cooperative assistive design of a single motor driving the knee and ankle joints, and realizing the intelligent switching of the driving paths of the knee and ankle joints in different gait phases through an electromagnetic clutch, significantly reducing the overall weight of the exoskeleton; designing a variable stiffness knee joint mechanism, using a shape memory alloy spring as a stiffness adjustment element, and based on the human knee joint angle-torque biomechanical curve, converting the knee joint torque change into the deformation control of the shape memory alloy spring through a variable stiffness cam to achieve the adaptive switching between high stiffness during the stance phase and low stiffness during the swing phase; developing a dual-cam cooperative driving mechanism, respectively designing the disc cam contour curves of the knee joint and the ankle joint based on gait analysis data, and realizing the sequential assistance of a single motor to the two joints by accurately fitting the joint angle change requirements; proposing a waist centralized power layout scheme, integrating the driving motor, reducer and transmission mechanism on the waist bracket, and transmitting the power to the distal joints through Bowden cables, which not only ensures the power transmission efficiency, but also effectively reduces the leg moment of inertia, improving the wearing comfort while ensuring the assistance effect; designing a multi-modal gait recognition control method, accurately dividing the gait cycle phase through the data fusion of the plantar pressure sensor array, joint potentiometer and motor encoder, and realizing the precise matching of the assistance timing and the human motion intention.

[0092] The exoskeleton system of the present invention realizes the sequential drive of a single motor to the knee and ankle joints through a metamorphic mechanism, adopts a shape memory alloy spring to realize the adaptive adjustment of the joint stiffness, and realizes the accurate gait phase recognition based on multi-sensor fusion, finally achieving the technical effects of light weight, high energy efficiency and comfortable wearing, and can be widely applied to the fields of rehabilitation training and industrial assistance. Compared with the traditional scheme, the present invention has the following advantages: reducing the system weight and improving the wearing comfort, realizing the drive of multiple joints by a single motor through the motion conversion ability of the metamorphic mechanism, thereby reducing the number of motors, reducing the overall mass of the exoskeleton, and improving the comfort of the wearer; optimizing the energy consumption and improving the endurance, the single motor drive scheme consumes less energy than the multi-motor system, thereby extending the battery life of the device and making it more suitable for long-term rehabilitation training or industrial operations; simplifying the control strategy and improving the system reliability, using the motion characteristics of the metamorphic mechanism, enabling the motion of the knee and ankle joints to be coordinately controlled by a single drive source, reducing the control complexity of the system and improving the operation stability.

[0093] The exoskeleton design based on the metamorphic principle provides a new technical idea for the research and development of future lower limb assistive exoskeletons, which not only has broad application prospects in the field of rehabilitation medicine, but also has important research value in the fields of industrial production, military assistance, etc. The proposal of the present invention helps to promote the development of exoskeleton technology and provides a new solution for improving the human-computer interaction ability and assistance efficiency.

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

[0095] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. All equivalent structural or equivalent process transformations made by using the content of the specification and drawings of the present invention, or directly or indirectly applied to other related technical fields, are equally included in the patent protection scope of the present invention.

Claims

1. A knee-ankle power-assisted exoskeleton based on the metamorphosis principle, characterized in that: It includes a control system, a waist driving mechanism, a waist transmission mechanism connected to the waist driving mechanism, a waist input knee joint transmission mechanism located below the waist transmission mechanism, a waist input ankle joint transmission mechanism rotatably connected to the lower end of the waist input knee joint transmission mechanism, and a plantar pressure sensor fixedly arranged on the output end of the waist input ankle joint transmission mechanism; The waist transmission mechanism comprises a waist output knee joint transmission assembly and a waist output ankle joint transmission assembly arranged in parallel, the output end of the waist output knee joint transmission assembly is connected to the input end of the waist input knee joint transmission mechanism via a first Bowden rope group, and the output end of the waist output ankle joint transmission assembly is connected to the input end of the waist input ankle joint transmission mechanism via 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 the three configuration cycle modes of "0-0→1-0→0-1→0-0...", where 0 indicates that the corresponding output end is in a non-power output state, and 1 indicates that the corresponding output end is in a power output state; The output end of the waist input knee joint transmission mechanism is also provided with a knee joint stiffness variable mechanism.

2. The knee-ankle assist exoskeleton based on the metamorphosis principle according to claim 1, characterized in that: The waist driving mechanism includes a waist plate, a driving motor fixedly mounted on the waist plate, and a camshaft rotatably mounted on the waist plate and transmission-connected to the output end of the driving motor, and a knee joint disc cam and an ankle joint disc cam are fixedly connected to the camshaft respectively.

3. The knee-ankle assist exoskeleton based on the metamorphosis principle according to claim 2, characterized in that: The lumbar output knee joint transmission assembly includes a knee joint rack movably matched with the knee joint disc cam, a knee joint gear rotatably mounted on the lumbar plate and meshing with the knee joint rack, and a knee joint input wire wheel rotatably mounted on the lumbar plate. One side shaft end of the knee joint input wire wheel and one side shaft end of the knee joint gear are connected through a knee joint electromagnetic clutch.

4. The knee-ankle assist exoskeleton based on the metamorphosis principle according to claim 3 is characterized by: The waist input knee joint transmission mechanism includes a thigh rod, a knee joint output wire wheel rotatably installed at the bottom end of the thigh rod, and a calf rod fixedly connected to the shaft end on one side of the knee joint output wire wheel. The bottom end of the first Bowden rope group is fixedly connected to the knee joint output wire wheel.

5. The knee-ankle assist exoskeleton based on the metamorphosis principle according to claim 4 is characterized in that: 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 on the end surface of the variable stiffness turntable, a second variable stiffness connecting rod hinged on the other end of the first variable stiffness connecting rod and vertically slidably connected to the thigh rod, and a variable stiffness cam rotatably installed on the thigh rod and located directly above the top end of the second variable stiffness connecting rod. The variable stiffness cam is a truncated cone structure with a horizontal axis, and the end surfaces on both sides of the cam are respectively fixedly connected to the first shape memory alloy spring and the second shape memory alloy spring, and the top end 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.

6. The knee-ankle assist exoskeleton based on the metamorphosis principle according to claim 4 is characterized in that: The waist output ankle joint transmission assembly includes an ankle joint rack movably matched with the ankle joint disc cam, an ankle joint gear rotatably mounted on the waist plate and meshing with the ankle joint rack, and an ankle joint input pulley rotatably mounted on the waist plate, and one side shaft end of the ankle joint input pulley and one side shaft end of the ankle joint gear are connected through an ankle joint electromagnetic clutch.

7. The knee-ankle assist exoskeleton based on the metamorphosis principle according to claim 6 is characterized by: The waist input ankle joint transmission mechanism includes an ankle joint output pulley rotatably mounted on the bottom end of the calf rod, an ankle plate rotatably sleeved on the shaft end of the ankle joint output pulley, the bottom end of the second Bowden rope group is fixedly connected to the ankle joint output pulley, and the plantar pressure sensor device is fixedly connected to the ankle plate.

8. The knee-ankle assist exoskeleton based on the metamorphosis principle according to claim 7 is characterized in that: A knee joint potentiometer is arranged at a hinged position between the bottom end of the thigh rod and the top end of the shank rod, and an ankle joint potentiometer is arranged at a hinged position between the bottom end of the shank rod and the ankle plate.

9. A control method for a knee-ankle powered exoskeleton based on the metamorphosis principle, characterized in that: The following steps are involved: Step 1: The subject wears the metamorphosis-based knee-ankle assisted exoskeleton, the system is powered on and initialized, and each functional component enters a standby state; Step 2: The control system reads the plantar pressure data, knee joint rotation angle data and ankle joint rotation angle data in real time to determine the current stage state of the leg in the gait cycle; Step 3: According to the stage state of the leg, the control system correspondingly adjusts the transmission configuration of the waist output knee joint transmission component and the waist output ankle joint transmission component to realize automatic switching between the knee joint power-assisting mode, the ankle joint power-assisting mode and the non-power-assisting mode, and the control system correspondingly adjusts the variable stiffness state of the knee joint variable stiffness mechanism to realize dynamic adjustment of the knee joint support torque; Step 4: According to the gait cycle, the control system cyclically switches the transmission configurations of the waist output knee joint transmission component and the waist output ankle joint transmission component 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; Step 5: Turn off the system, the subject takes off the exoskeleton, and the system automatically saves the gait data to the PC for subsequent analysis.

10. The control method of the knee-ankle powered exoskeleton based on the metamorphosis principle according to claim 9, characterized in that: The gait cycle is divided into a stance flexion phase, a stance extension phase, a pre-swing phase and a swing phase in sequence; In the standing flexion stage, the control system energizes the shape memory alloy spring heating wire in the variable stiffness mechanism of the knee joint, changes the stiffness of the shape memory alloy spring by adjusting the current, and then drives the variable stiffness cam to move, dynamically adjusting the knee joint support torque; In the standing extension phase, the waist driving mechanism drives the waist input knee joint transmission mechanism to rotate through the waist output knee joint transmission assembly and the first Bowden rope group to provide knee joint extension assistance; In the pre-swing stage, the waist drive mechanism drives the waist input ankle joint transmission mechanism to rotate through the waist output ankle joint transmission assembly and the second Bowden rope group to provide ankle joint dorsiflexion assistance; During the swinging stage, the waist driving mechanism and the waist transmission mechanism are not working, and the ankle transmission mechanism is in a free state.

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