Ankle Hybrid Exoskeleton System Integrated with Functional Electrical Stimulation and Assistive Torque Distribution Method

Abstract

The present invention discloses an ankle hybrid exoskeleton system integrating functional electrical stimulation, which includes a leg bracket for fixing on the calf, a foot fixing plate hinged to the bottom of the leg bracket, a driving mechanism arranged on the leg bracket for driving the foot fixing plate to swing, and a system module supporting the driving mechanism. The present invention also provides a method for distributing assistive torque. The system provided by the present invention can effectively assist patients in maintaining the correct position of the feet during walking, thereby effectively preventing foot drop and improving the safety and efficiency of walking.

Description

Technical Field

[0001] The present invention belongs to the technical field of rehabilitation training equipment, and particularly relates to an ankle hybrid exoskeleton system integrating functional electrical stimulation and an assistance torque distribution method. Background Art

[0002] As people age, their physical functions degenerate, and it becomes increasingly difficult for muscles and bones to support their daily walking and movement needs, seriously affecting the healthy life of the elderly. In terms of bones, from the age of 40 to 80, people experience severe bone mass loss, fewer pores in the bone, an increasing incidence of osteoporosis, and an increased risk of fractures. Among them, the probability of the elderly having ankle problems is relatively high. The ankle joint is a very important joint in the body, responsible for supporting the body weight, maintaining balance, and controlling movement. Sports injuries, such as sprains, ligament strains, or fractures, as well as chronic diseases, may lead to the loss or impairment of ankle joint function, affecting an individual's walking ability and quality of life. During human activities, ankle injuries caused by various reasons are very common, and the demand for ankle exoskeletons is increasing.

[0003] Lower limb wearable exoskeletons are intelligent mechanical devices that can provide assistance torque to the wearer by referring to the movement form of human joints. In the medical field, lower limb exoskeletons can be used as medical rehabilitation treatment equipment to assist patients in carrying out rehabilitation training and gradually develop into the current medical mechanical exoskeletons. Medical mechanical exoskeletons are an advanced technology integrating engineering, medicine, and biomechanics. This technology is designed to improve human physical performance and provide support for individuals with movement disorders, rehabilitation needs, or disabilities. Ankle exoskeletons are a type of mechanical assistance device specifically designed to support and enhance the function of the ankle joint. For patients with ankle injuries or movement function disorders, on the one hand, they are used as medical rehabilitation treatment equipment to assist them in carrying out rehabilitation training, and on the other hand, they assist the elderly who are unable to carry out daily activities due to ankle problems to walk, meet their living needs, and reduce the resources invested in treating ankle-related symptoms in hospitals. Therefore, the research on ankle exoskeletons is becoming increasingly important.

[0004] Patent document CN103655122A discloses a knee exoskeleton system integrating functional electrical stimulation. In the field of lower limb rehabilitation, especially knee joint rehabilitation, traditional rehabilitation training methods often rely on the manual operation of physical therapists. This method is inefficient and difficult to achieve personalized treatment. To improve the rehabilitation efficiency and effect, the prior art has proposed a knee exoskeleton system integrating functional electrical stimulation. This system is connected to the knee exoskeleton through a DC servo motor driver. The controller simultaneously controls the motor driver and a multi-channel functional electrical stimulator to achieve the coordinated operation of the knee exoskeleton and functional electrical stimulation. This system can exert the patient's own muscle strength, and at the same time the rehabilitation robot provides an auxiliary function, acting together on paralyzed patients to provide optimal knee joint rehabilitation training. However, the prior art mainly focuses on the rehabilitation of the knee joint and pays insufficient attention to the rehabilitation training of other lower limb joints such as the ankle joint, which limits the comprehensiveness and effect of the rehabilitation training.

[0005] Patent document CN111408042A discloses a method, device, storage medium and system for intelligent distribution of functional electrical stimulation and lower limb exoskeleton. It obtains the bone dynamic characteristic parameters of the user and the motion parameters of the lower limb joints, and inputs them into the inverse dynamics model of the exoskeleton robot to determine the torque relationship of each joint. This method is applicable to the field of rehabilitation training and improves the intelligent level of rehabilitation training. Nevertheless, there are still certain limitations in the prior art in the intelligent distribution method, especially in real-time monitoring and dynamic adjustment, lacking a more accurate and personalized control strategy to adapt to the specific needs and rehabilitation progress of different patients. Summary of the Invention

[0006] The purpose of the present invention is to provide an ankle hybrid exoskeleton system integrating functional electrical stimulation and a method for assisting torque distribution. This system can effectively assist patients in maintaining the correct position of the feet during walking, thereby effectively preventing foot drop and improving the safety and efficiency of walking.

[0007] To achieve the first object of the present invention, the following technical solution is provided: An ankle hybrid exoskeleton system integrating functional electrical stimulation, including a leg bracket for fixing on the calf, a foot fixing plate hinged to the bottom of the leg bracket, a driving mechanism provided on the leg bracket for driving the foot fixing plate to swing, and a system module supporting the driving mechanism;

[0008] The system module includes FES electrode patches for stimulating leg muscles, pressure sensors provided on the foot fixing plate for collecting gait information, ankle encoders provided at the hinge joint between the leg bracket and the foot fixing plate for collecting rotation angles, and a controller for generating control commands based on the gait information and rotation angles. The controller sends the control commands to the driving mechanism to complete the auxiliary walking task. The gait information includes heel strike and toe off.

[0009] The system provided by the present invention adjusts the driving force of the exoskeleton on the patient's leg by collecting the gait information of the patient in real time, and at the same time cooperates with the FES electrode patches to electrically stimulate the leg muscles during walking, so as to correct the abnormal gait of the patient and promote the rehabilitation process.

[0010] Specifically, the FES electrode patches are arranged on the tibialis anterior muscle and soleus muscle of the human body, and during the rehabilitation process, they simultaneously play the role of active muscle-driven rehabilitation with physiological electrical stimulation and passive rehabilitation with the physical interaction force stimulation of the exoskeleton, accelerating the rehabilitation process and reducing the dependence on traditional single physical therapy.

[0011] Specifically, the leg bracket includes support rods arranged on both sides of the calf and a first fixing ring located below the knee for connecting the support rods on both sides.

[0012] Specifically, the foot fixing plate includes a foot bracket and a second fixing ring hinged to the bottom of the leg bracket, and a rear foot sole support and a front foot sole support arranged on the foot bracket. Pressure sensors are provided on both the rear foot sole support and the front foot sole support, so as to obtain more accurate gait information.

[0013] In order to achieve the second object of the present invention, the following technical solution is provided: a method for distributing assistive torque, which is realized by the above-mentioned ankle hybrid exoskeleton system integrating functional electrical stimulation, and includes the following steps:

[0014] Collect the swing angle change of the foot fixing plate under a preset number of steps through an ankle encoder, and generate corresponding angle feedback according to multiple groups of swing angle changes;

[0015] Based on the angle feedback and the preset normal ankle angle change data, and using the method of piecewise calculation to obtain the gait deviation matrix;

[0016] Construct a corresponding cost function according to the gait deviation matrix and the preset weight parameters, and optimize the assistive torque parameters based on the cost function to output a corresponding assistive parameter matrix;

[0017] Estimate the gait phase for each gait cycle according to the gait information collected by the pressure sensor, and construct a corresponding parameterized assistive torque based on the estimated gait phase and the assistive parameter matrix;

[0018] Generate the swing angle change caused by calf muscle fatigue according to the angle feedback, and compare and calculate based on the swing angle change and the normal ankle angle to construct a corresponding muscle fatigue trajectory deviation index, and the calf muscles include the gastrocnemius muscle and the tibialis anterior muscle;

[0019] Based on the parameterized assistive torque and the muscle fatigue trajectory deviation index, and generate the corresponding control instructions for the drive mechanism through the torque coordination control strategy.

[0020] The method provided by the present invention introduces a torque coordination control strategy based on an over-fatigue protection mechanism during the optimization of the conventional parameterized assistive force, thereby avoiding the risk of secondary injury to patients caused by excessive muscle fatigue during long-term rehabilitation training.

[0021] Specifically, the assistive torque parameters include the start time, peak time, torque magnitude, and stop time of the motor plantar flexion torque curve, as well as the start time, peak time, torque magnitude, and stop time of the motor dorsiflexion torque curve.

[0022] Specifically, the expression of the parameterized assistive torque is as follows: ; ; where represents the assistive torque output by the exoskeleton, represents the plantar flexion assistive torque, represents the dorsiflexion assistive torque, , represents the normalized gait phase, where , , and correspond to the start time, peak time, torque magnitude, and stop time of the motor plantar flexion torque curve respectively; , , and correspond to the start time, peak time, torque magnitude, and stop time of the motor dorsiflexion torque curve respectively.

[0023] Specifically, the calculation formula of the muscle fatigue trajectory deviation index is as follows: ; where and are the normal angle and the actual angle when stimulating the gastrocnemius muscle respectively, and are the normal angle and the actual angle when stimulating the tibialis anterior muscle respectively, represents the number of walking steps.

[0024] Specifically, the torque coordination control strategy adjusts the distribution coefficient of the parameterized assistive torque according to the muscle fatigue trajectory deviation index to generate the corresponding control instructions, and the process is as follows: ; ; where and are the fatigue indices of the gastrocnemius muscle and the tibialis anterior muscle respectively, function represents the sign function, represents the correspondingi Muscle fatigue trajectory deviation index of the gastrocnemius muscle at +1 step indicating the muscle fatigue trajectory deviation index of the tibialis anterior muscle corresponding to the i step; the expression of the distribution coefficient is as follows: ; where and correspond to the distribution coefficients of the gastrocnemius muscle and the tibialis anterior muscle respectively; the expression of the control instruction is as follows: ; ; where represents the torque generated by electrical muscle stimulation, represents the motor assistance torque, and correspond to the torques generated by electrical stimulation of the gastrocnemius muscle and the tibialis anterior muscle respectively, represents the plantar flexion assistance torque, represents the dorsiflexion assistance torque.

[0025] Specifically, the estimation process of the gait phase is as follows: by detecting the heel strike and toe off events, the gait cycle is divided into multiple sub-intervals;

[0026] Within each sub-interval, a linear interpolation method is used to estimate the gait phase, and its linear interpolation expression is as follows: ; where represents the current time, and represent the start and end times of the sub-interval respectively.

[0027] Compared with the prior art, the beneficial effects of the present invention:

[0028] The structure of the human ankle joint is designed to enable the cooperation of electrical stimulation and exoskeleton assistance, correct abnormal gait, prevent foot drop, and promote neuromuscular rehabilitation;

[0029] At the same time, based on the muscle fatigue mechanism, an algorithm for detecting muscle fatigue and adjusting the electrical stimulation intensity is provided, which helps to provide an efficient and safe rehabilitation effect for patients. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic design diagram of the ankle hybrid exoskeleton system incorporating functional electrical stimulation provided in this embodiment;

[0031] Figure 2 is a schematic diagram of the mechanical mechanism part in the ankle hybrid exoskeleton system provided in this embodiment;

[0032] Figure 3 is a schematic diagram of the bending change at the front end of the foot fixing plate provided in this embodiment;

[0033] Figure 4 Schematic diagram of the assistive torque distribution method provided in this embodiment;

[0034] Figure 5 Schematic diagram of the gait deviation evaluation process provided in this embodiment;

[0035] Figure 6 Schematic diagram of the conversion of gait phase estimation provided in this embodiment;

[0036] Figure 7 Schematic diagram of the use of the subject provided in this embodiment;

[0037] Figure 8 Schematic diagram of the ankle joint angle of the subject during use provided in this embodiment;

[0038] In the figure, 101 is the controller; 102 is the battery; 103 is the bandage; 104 is the FES electrode patch; 105 is the pressure sensor; 2 is the mechanical part; 201 is the crank; 202 is the crank housing; 203 is the crank connecting rod; 204 is the ankle joint encoder; 205 is the foot fixing plate; 206 is the second fixing ring; 207 is the heel parallel rod; 208 is the rear sole footrest; 209 is the motor; 210 is the front sole footrest; 211 is the first fixing ring; 212 is the support rod. Detailed implementation manners

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0040] As Figure 1 and Figure 2 shown, a kind of ankle joint hybrid exoskeleton system integrating functional electrical stimulation provided in this embodiment, the mechanical part 2 includes a leg bracket for fixing on the calf, a foot fixing plate hinged to the bottom of the leg bracket, and other parts include a driving mechanism arranged on the leg bracket for driving the foot fixing plate to swing and a system module supporting the driving mechanism.

[0041] Among them, the leg bracket includes support rods 212 arranged on both sides of the calf, and a first fixing ring 211 located below the knee for connecting the support rods on both sides.

[0042] The foot fixing plate includes a foot bracket 205 and a second fixing ring 206 hinged to the bottom of the leg bracket, and a rear foot sole support 208 and a front foot sole support 207 arranged on the foot bracket. Pressure sensors 105 are provided on both the rear foot sole support 208 and the front foot sole support 210.

[0043] The system module includes FES electrode patches 104 for stimulating leg muscles, pressure sensors 105 provided on the foot fixing plate for collecting gait information, an ankle encoder 204 provided at the hinge joint between the leg bracket and the foot fixing plate for collecting the rotation angle, and a controller 1 for generating control instructions based on the gait information and the rotation angle. The controller 1 sends the control instructions to the drive mechanism to complete the assisted walking task. The gait information includes heel strike and toe off. In this example, the controller 1 and the battery 102 used in combination are fixed to the patient's waist, and at the same time, its data cable is fixed to the position below the patient's knee through a strap 103.

[0044] In this embodiment, the drive mechanism includes a motor 209 fixed on the support rod 212. The output end of the motor 209 is connected to a crank 201, and the other end of the crank 201 is connected to a crank connecting rod 203. The crank connecting rod 203 is connected to the heel parallel rod 207 at the rear end of the foot bracket 205 to drive the foot bracket 205 to swing. A crank housing 202 is sleeved outside the motor 209.

[0045] In addition, as Figure 3 shown, in this embodiment, the material of the foot bracket 205 at the front foot sole support 210 is selected to be relatively thin and have a certain toughness, so as to effectively clamp the front sole of the wearer's shoe by bending through tightening the strap, thereby realizing the adaptation to individuals of different sizes. Among them Figure 3 Figure (a) shows the state where the front foot sole support is not clamped, Figure 3 Figure (b) shows the state where the front foot sole support is clamped.

[0046] This embodiment also provides a method for distributing the assisting torque, which is realized by the ankle hybrid exoskeleton system provided in the above embodiment. As Figure 4 shown, it includes the following steps:

[0047] Collect the swing angle change of the foot fixing plate under a preset number of steps through the ankle encoder, and generate corresponding angle feedback according to multiple groups of swing angle changes;

[0048] Based on the angle feedback and the preset normal ankle angle change data, and using the method of segmented calculation to obtain the gait deviation matrix;

[0049] Construct a corresponding cost function based on the gait deviation matrix and preset weight parameters, and optimize the assistive torque parameters based on the cost function to output a corresponding assistive parameter matrix;

[0050] Estimate the gait phase for each gait cycle according to the gait information collected by the pressure sensor, and construct a corresponding parameterized assistive torque based on the estimated gait phase and the assistive parameter matrix;

[0051] Generate the change in the swing angle caused by calf muscle fatigue according to the angle feedback, and compare and calculate based on the change in the swing angle and the normal ankle joint angle to construct a corresponding muscle fatigue trajectory deviation index, where the calf muscles include the gastrocnemius and the tibialis anterior;

[0052] Based on the parameterized assistive torque and the muscle fatigue trajectory deviation index, generate a corresponding control command for the drive mechanism through a torque coordination control strategy.

[0053] Among them, Figure 4 in (a) is a schematic diagram of the ankle joint hybrid exoskeleton system.

[0054] More specifically, as Figure 4 in (b) is the gait evaluation process provided in this embodiment, where the calculation process of the gait deviation matrix E requires the controller to obtain angle feedback through the ankle joint encoder , and evaluate the current gait and the target ankle joint angle through this gait data The error is as follows: Each iteration corresponds to walking steps, where . The average ankle joint encoder angle data for multiple steps is as follows: ; By calculating the root mean square error between the ankle joint encoder data and the preset normal ankle joint angle data, E is obtained. When calculating the root mean square error of the ankle joint angle, a segmented calculation method is adopted to obtain six elements of the error matrix E. The basis for segmentation comes from the experience summarized during the previous user preference tests. These experiences also act on the parameter space of the optimization parameters. Specifically, as shown in the following formula: ; ; ; ; As shown in (c) of Figure 4 , it is the process of optimizing the parameterized assistive torque, which includes calculating the cost function and selecting the optimization algorithm of the assistive torque.

[0055] The cost function is calculated based on the error between the plantar flexion / dorsiflexion angle collected by the exoskeleton ankle joint encoder and the normal ankle joint angle data of normal people and a series of weights. The input is the gait deviation matrix E, the cost function cost is calculated: by artificially setting the weight matrix W , the final cost function cost is calculated. The formula is: ; The purpose of setting the weight matrix is to hope that the error of plantar flexion / dorsiflexion will be more concerned during the iterative optimization process, and the iteration will be accelerated.

[0056] In this embodiment, the controller uses a black-box optimization algorithm to optimize the assist torque parameters. The input is the cost function cost, and the output is the assist parameter matrix M . The parameters of the assist torque include 8 parameters, which respectively correspond to the torque magnitudes, start times, peak times, and stop times of the positive and negative peaks. Its assist parameter matrix M is expressed as follows: ; where , , and respectively correspond to the start time, peak time, torque magnitude, and stop time of the motor plantar flexion torque curve; , , and respectively correspond to the start time, peak time, torque magnitude, and stop time of the motor dorsiflexion torque curve.

[0057] When selecting an optimization algorithm, any one of the assist parameter matrices M will have an impact on the overall evaluation index. Therefore, global optimization ability is required; it is inclined to regard the human-exoskeleton system as a black box; the cost function has no way to calculate the gradient, and the calculation takes a certain amount of time. Therefore, the black-box optimization algorithm described in this embodiment specifically uses Bayesian optimization.

[0058] As Figure 4 in (f), it is the generation process of the exoskeleton assist torque, and its formula is as follows:

[0059] The expression of the parameterized assist torque is as follows: ; ; where represents the assist torque output by the exoskeleton, represents the plantar flexion assist torque, represents the dorsiflexion assist torque, , represents the normalized gait phase, where , , and respectively correspond to the start time, peak time, torque magnitude, and stop time of the motor plantar flexion torque curve; , , and Correspond to the starting time, peak time, torque magnitude, and stopping time of the motor dorsiflexion torque curve respectively.

[0060] As Figure 4 shown in (d) of, the over-fatigue protection mechanism provided in this embodiment has the principle that, under the same electrical stimulation intensity and motor assistance intensity, the degree of deviation of the actual trajectory from the ideal trajectory is defined as the "Muscle Fatigue Trajectory Deviation Index" (MFTDI). MFTDI is used to measure the degree of deviation between the actual movement trajectory and the expected ideal trajectory due to muscle fatigue under fixed electrical stimulation and motor assistance conditions. MFTDI takes into account the influence of muscle fatigue on movement control and evaluates the fatigue state of muscles by analyzing the deviation between the actual trajectory and the ideal trajectory. Since the objects of FES are the gastrocnemius muscle and the tibialis anterior muscle, they need to be calculated separately.

[0061] Therefore, the MFTDI of this study is set as the vector , and the calculation formula of the muscle fatigue trajectory deviation index is as follows: ; where and are the normal angle and the actual angle when stimulating the gastrocnemius muscle respectively, and are the normal angle and the actual angle when stimulating the tibialis anterior muscle respectively, represents the number of walking steps.

[0062] As Figure 4 shown in (e) of, the torque collaborative control strategy based on the motor and FES proposed in this embodiment is as follows: The controller adjusts the torque distribution coefficient of FES and the motor according to the fatigue index output by the over-fatigue protection mechanism.

[0063] The torque distribution coefficient output by the over-fatigue protection mechanism decreases correspondingly when the fatigue index increases, preventing muscle over-fatigue caused by continuous high-intensity FES. The over-fatigue protection mechanism is shown in the following formula: ; ; where and are the fatigue indices of the gastrocnemius muscle and the tibialis anterior muscle respectively, with a range of -1 to 1, the function represents the sign function, represents the muscle fatigue trajectory deviation index of the gastrocnemius muscle corresponding to the i +1 step, represents the muscle fatigue trajectory deviation index of the gastrocnemius muscle corresponding to the i step, represents corresponding to thei Muscle fatigue trajectory deviation index of tibialis anterior muscle at +1 step, indicating the muscle fatigue trajectory deviation index of tibialis anterior muscle corresponding to the i step.

[0064] Wherein, when all , takes 1, indicating that the MFTDI continues to decrease at this time and muscle fatigue is recovering.

[0065] When all , takes -1, indicating that the MFTDI continues to increase at this time and muscle fatigue becomes more severe.

[0066] The expression of the distribution coefficient is as follows: ; wherein, and correspond to the distribution coefficients of gastrocnemius muscle and tibialis anterior muscle respectively.

[0067] As shown in (g) of Figure 4 , the expression of its control instruction is as follows: ; ; wherein, represents the torque generated by electrical stimulation of the muscle, represents the motor assistance torque, and correspond to the torques generated by electrical stimulation of gastrocnemius muscle and tibialis anterior muscle respectively, represents the plantar flexion assistance torque, represents the dorsiflexion assistance torque.

[0068] As shown in Figure 5 , during the gait assessment process, the deviation matrix E and the muscle fatigue trajectory deviation index required for the optimization of assistance parameters and the over-fatigue protection mechanism are output simultaneously in one iteration. For the optimization of assistance parameters and the over-fatigue protection mechanism, the data input for both is essentially the error between the real-time data of the ankle joint encoder and the normal gait. The input muscle fatigue trajectory deviation index of the over-fatigue protection mechanism is meaningful only under the same electrical stimulation intensity and motor assistance intensity. Each iteration of the optimization of assistance parameters corresponds to the walking data of steps of wearing and walking under the same electrical stimulation intensity and motor assistance intensity. Therefore, the corresponding can be calculated and recorded at each step of this process. At the end of the iteration process, the corresponding to each step is output to the fatigue protection mechanism, and the torque distribution coefficient is adjusted. At the same time, the deviation matrix E of the multi-step average angle during the iteration process is output to the mixed exoskeleton assistance parameter optimization process to calculate the cost of the optimization of assistance parameters.

[0069] As Figure 6 shown in (a) of Figure 6 , in this embodiment, gait information detection is achieved by identifying key events in the gait cycle, including Heel Strike (HS) and Toe Off (TO). These events can be detected by the pressure change of the FSR. The FSR sensors are respectively placed at the heel and toe positions to detect the pressure change.

[0070] Continuous gait phase estimation estimates the gait phase by real-time monitoring of gait events. The gait phase is usually represented as a value between 0 and 100%, where 0 represents the HS event and 100% represents the next HS event.

[0071] Time-based gait phase Estimation method: within each gait cycle, the gait phase is estimated by time interpolation, and the process is as follows: The specific steps are as follows:

[0072] Gait cycle division: By detecting the HS and TO events, the gait cycle is divided into multiple sub-intervals.

[0073] Gait phase interpolation: within each sub-interval, the linear interpolation method is used to estimate the gait phase. The linear interpolation formula is as follows: ; where represents the current time, and respectively represent the start and end times of the sub-interval.

[0074] According to the results of gait event detection and time-based gait phase estimation (linear interpolation), a continuous and stable gait phase can be obtained, and the obtained gait phase is shown in (b) of Figure 6.

[0075] To better illustrate the technical effects of the system and the assistive torque distribution method provided in this embodiment, patients in a certain rehabilitation hospital were solicited for wearing experience tests, as Figure 7 shown.

[0076] As Figure 7 shown in (a) of Figure 7 , wearing experience tests were conducted on patients in a certain rehabilitation hospital, and the wearing experience was good. The experimental subjects were three hemiplegic patients, and the experimental walking distance was 30 m. To ensure safety in the experiment, the peak value of the assistive curve was adjusted to 18 Nm. As Figure 7As shown in (b), three hemiplegic patients underwent independent walking without wearing the exoskeleton and a 30 m walking test with the assistance of the exoskeleton, and the walking speeds of independent walking and assisted walking were compared. Among them, "P1 N" represents the independent walking of patient 1, and "P1 A" represents the assisted walking of patient 1. Compared with independent walking, the walking speeds of two patients decreased during assisted walking, while the speed of one patient increased. The results of the decreased walking speeds of the two patients may be caused by various factors, such as too small exoskeleton assistance intensity or the patient's failure to adapt to the assistance after wearing the exoskeleton, etc.

[0077] As Figure 8 shown, the results of the active leg force under the action of FES are demonstrated by the ankle joint movement angle. A total of 3 subjects without walking disabilities participated in this experiment, corresponding to (a) in Figure 8, Figure 8 (b) in Figure 8 and (c) in

[0078] It can be seen that the flexion angles of the ankle joints of the 3 subjects under the action of FES are all greater than those of the non-stimulated group, and the increasing trends of the flexion angles are similar, indicating that the FES unit has good consistency in the stimulation output for different individuals. Compared with the other two subjects, subject 1 showed a greater muscle response, with a maximum difference of more than 15°, and at the same time, the ankle joint angle range was -15° to 10° in the non-stimulated state, and the simulated foot drop in the experiment was in line with the actual patient situation.

[0079] In addition, the terms "upper", "lower", "inner", "outer", "front", and "back" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. Unless otherwise specifically stated, the relative steps, numerical expressions, and values of the components and steps described in these embodiments do not limit the scope of the present invention.

[0080] Of course, the above are only specific embodiments of the present invention and do not limit the scope of the implementation of the present invention. Any equivalent changes or modifications made according to the structure, features, and principles described in the scope of the patent application of the present invention should be included in the scope of the patent application of the present invention.

[0081] Finally, it should be noted that the above-described embodiments are only specific embodiments of the present invention, used to illustrate the technical solutions of the present invention, rather than limiting it. The protection scope of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that any technician familiar with the technical field of the present invention can still modify the technical solutions described in the foregoing embodiments, or can easily think of changes, or perform equivalent replacements on some of the technical features; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. An ankle hybrid exoskeleton system integrating functional electrical stimulation, characterized in that, It includes a leg brace for fixing on the calf, a foot fixing plate hinged to the bottom of the leg brace, a driving mechanism provided on the leg brace for driving the foot fixing plate to swing, and a system module supporting the driving mechanism; The system module includes FES electrode patches for stimulating leg muscles, pressure sensors provided on the foot fixing plate for collecting gait information, ankle joint encoders provided at the hinge joint between the leg brace and the foot fixing plate for collecting rotation angles, and a controller for generating control commands based on the gait information and the rotation angles. The controller sends the control commands to the driving mechanism to complete the assisted walking task. The gait information includes heel strike and toe off; The ankle hybrid exoskeleton system integrating functional electrical stimulation further includes a method for distributing assistive torque, comprising the following steps: Collect the swing angle changes of the foot fixing plate under a preset number of steps through the ankle joint encoder, and generate corresponding angle feedback based on multiple groups of swing angle changes; Based on the angle feedback and the preset normal ankle joint angle change data, and using a piecewise calculation method to obtain a gait deviation matrix; Construct a corresponding cost function according to the gait deviation matrix and the preset weight parameters, and optimize the assistive torque parameters based on the cost function to output a corresponding assistive parameter matrix; Estimate the gait phase for each gait cycle according to the gait information collected by the pressure sensor, and construct a corresponding parameterized assistive torque based on the estimated gait phase and the assistive parameter matrix; Generate swing angle changes caused by calf muscle fatigue according to the angle feedback, and compare and calculate based on the swing angle changes and the normal ankle joint angles to construct a corresponding muscle fatigue trajectory deviation index. The calf muscles include the gastrocnemius muscle and the tibialis anterior muscle; Based on the parameterized assistive torque and the muscle fatigue trajectory deviation index, generate corresponding control commands for the driving mechanism through a torque co-control strategy.

2. The ankle hybrid exoskeleton system integrating functional electrical stimulation according to claim 1, characterized in that, The FES electrode patches are provided on the tibialis anterior muscle and the soleus muscle of the human body.

3. The ankle hybrid exoskeleton system integrating functional electrical stimulation according to claim 1, characterized in that, The leg brace includes support rods arranged on both sides of the calf, and a first fixing ring located below the knee for connecting the support rods on both sides.

4. The ankle hybrid exoskeleton system integrating functional electrical stimulation according to claim 1, wherein The foot fixing plate includes a foot support and a second fixing ring hinged to the bottom of the leg brace, and a rear foot sole support and a front foot sole support provided on the foot support. Pressure sensors are provided on both the rear foot sole support and the front foot sole support.

5. The ankle hybrid exoskeleton system integrating functional electrical stimulation according to claim 1, characterized in that, The assistive torque parameters include the start time, peak time, torque magnitude, and stop time of the motor plantar flexion torque curve, and the start time, peak time, torque magnitude, and stop time of the motor dorsiflexion torque curve.

6. The ankle hybrid exoskeleton system integrating functional electrical stimulation according to claim 1, characterized in that, The expression of the parametric assist torque is as follows: ; ; where represents the assist torque output by the exoskeleton, represents the plantar flexion assist torque, represents the dorsiflexion assist torque, , represents the normalized gait phase, where , , and correspond to the start time, peak time, torque magnitude, and stop time of the motor plantar flexion torque curve respectively; , , and correspond to the start time, peak time, torque magnitude, and stop time of the motor dorsiflexion torque curve respectively.

7. The ankle hybrid exoskeleton system integrating functional electrical stimulation according to claim 1, characterized in that The calculation formula of the muscle fatigue trajectory deviation index is as follows: ; where and are the normal angle and the actual angle when the gastrocnemius muscle is stimulated respectively, represents the number of steps walked, RMES ( ) represents the root mean square error.

8. The ankle hybrid exoskeleton system integrating functional electrical stimulation according to claim 1, characterized in that, The torque collaborative control strategy adjusts the distribution coefficient of the parameterized assistive torque according to the muscle fatigue trajectory deviation index to generate corresponding control instructions. The process is as follows: ; ; where and are the fatigue indices of the gastrocnemius muscle and the tibialis anterior muscle respectively, the function represents the sign function, represents the muscle fatigue trajectory deviation index of the gastrocnemius muscle corresponding to the i +1 step, represents the muscle fatigue trajectory deviation index of the gastrocnemius muscle corresponding to the i step, represents the muscle fatigue trajectory deviation index of the tibialis anterior muscle corresponding to the i +1 step, represents the muscle fatigue trajectory deviation index of the tibialis anterior muscle corresponding to the i step; The expression of the distribution coefficient is as follows: ; where and correspond to the distribution coefficients of the gastrocnemius and tibialis anterior muscles respectively; the expression of the control instruction is as follows: ; ; where represents the torque generated by electrical muscle stimulation, represents the motor assistance torque, and correspond to the torques generated by electrical stimulation of the gastrocnemius and tibialis anterior muscles respectively, represents the plantar flexion assistance torque, represents the dorsiflexion assistance torque.

9. The ankle hybrid exoskeleton system integrating functional electrical stimulation according to claim 1, characterized in that, The estimation process of the gait phase is as follows: Divide the gait cycle into multiple sub-intervals by detecting heel strike and toe off events; In each sub-interval, the method of linear interpolation is used to estimate the gait phase, and its linear interpolation expression is as follows: ; where represents the current time, and represent the start and end times of the sub-interval respectively.

Images