Rigid-flexible coupling knee joint structure and control method based on gait phase switching rule

Abstract

The application discloses a rigid-flexible coupling knee joint structure based on gait phase switching rules and a control method thereof; the rigid-flexible coupling knee joint structure is driven by a pneumatic muscle as a source power driving mechanism, and is combined with multiple elastic members and a rod as a supporting and connecting mechanism; when in a gait supporting phase, three triple fastening effects of a convex embedding into a groove, double muscle pulling up and a rubber fastening block fastening effect are provided to provide sufficient friction torque to resist joint rotation, ensure overall joint stability and provide necessary supporting effect; when in a gait swing phase, the three triple fastening effects are released, the excellent effect of the compliance of the elastic member is released, and the mechanical knee joint can realize passive rotation and translation in any direction; through collection of data in the gait process, a function model is constructed by using a least square method to calculate a gait phase value, and a PD control algorithm based on a joint total recovery torque model is applied to output an auxiliary torque value, so that the antagonistic tension of the pneumatic muscle is dynamically adjusted, and high compliance collaborative control of the rigid-flexible coupling knee joint and human gait is realized.

Description

Technical Field

[0001] This invention relates to the field of medical rehabilitation devices, specifically to a rigid-flexible coupled knee joint structure based on gait phase switching laws and its control method. Background Technology

[0002] In recent years, with the increasing aging of the world's population, the number of stroke patients and work-related illnesses has been rising, leading to a growing global demand for exoskeleton rehabilitation. For these patients, after acute clinical procedures such as surgery, rehabilitation training is the primary treatment to help them regain lower limb motor function. However, due to limited rehabilitation resources, only a small number of patients can receive systematic rehabilitation treatment. Using rehabilitation robots to assist patients in motor training can alleviate the shortage of rehabilitation resources to some extent, while also offering high efficiency, low cost, and a combination of active and passive training strategies.

[0003] Current lower limb exoskeleton designs largely focus on rigid structures, with insufficient research on flexible structures and the fit of human lower limb movement phase changes. Taking the knee joint as an example, existing designs mostly focus on sagittal plane rotation control, while excluding the small degrees of freedom of movement in other directions. This results in a lack of compliance when the machine joint moves in tandem with the human biological joint. At the same time, the design of flexible structures still largely follows the interpretation and execution of rigid structures, thus limiting the multi-directional flexible movement characteristics of flexible mechanisms and making it difficult to achieve compliant control of flexible structures.

[0004] In addition, existing lower limb exoskeleton control methods mostly rely on thigh posture angles or electromyographic signals to determine gait phase. The angle signals are easily affected by noise, and the electromyographic signals are more sensitive to individual differences and non-periodic changes in gait, which can easily lead to inaccurate judgment of assistance timing, thereby affecting its compliance and human-machine coordination during phase switching. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a rigid-flexible coupled knee joint structure and its control method based on gait phase switching patterns. The aim is to improve the compatibility between mechanical and biological joints and enhance the compliance of mechanical components with motion planning during human movement phase switching. The rigid-flexible coupled mechanical knee joint employs a rigid-flexible coupling mechanism similar to the motion characteristics of the human knee joint. When the human movement phase is in the gait support phase, the rigid mechanism is automatically triggered. When transitioning from the support phase to the swing phase, the rigid mechanism automatically fails under gravity, instead triggering a flexible mechanism that conforms to the motion characteristics of the human swing phase. Furthermore, this invention provides… A rigid-flexible coupled knee joint control method based on plantar pressure signals and artificial pneumatic muscle actuation is proposed. This method introduces a gait phase estimation module and a PD control module. The gait phase value is calculated by using a function model fitted by the least squares method to achieve continuous monitoring of the gait cycle. At the same time, combined with a PD control strategy based on a dynamic model, the output force of the artificial pneumatic muscle is precisely adjusted by introducing a constant reference tension antagonistic distribution method. This enables the rigid-flexible coupled knee joint structure to achieve rigid-flexible coordinated movement similar to that of the human knee joint under different gait phases, thereby improving the compliance between the structure's motion planning and the human gait phase.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a rigid-flexible coupled knee joint structure based on gait phase switching law, comprising: an exoskeleton assembly 1, a swing assembly 2, and a support and locking assembly 3; wherein, the exoskeleton assembly 1 includes a thigh bar 11 and a calf bar 12 respectively fixed to the patient's thigh and calf, and a pneumatic muscle 13 and a pneumatic muscle connector 14 for connecting the thigh bar 11 and the calf bar 12, as well as a power supply 15 and a controller 16 placed on the thigh bar 11; the swing assembly 2 includes a hemispherical shell 21 connected to the bottom end of the thigh bar 11, and a ball suspended inside the hemispherical shell 21 The spherical inner shell 22 and a plurality of elastic elements 23 for connecting the hemispherical outer shell 21 and the spherical inner shell 22 also include an angle sensor 24; the hemispherical outer shell 21 has a concave arc-shaped groove 211 at the top; the spherical inner shell 22 has a concave receiving groove 221 and an outwardly convex arc-shaped protrusion 222 at the top; the support locking assembly 3 includes a top plate 31 fixed to the top of the lower leg rod 12, a plurality of transmission rods 32 rotatably connected to the spherical inner shell 22 and the top plate 31, and a rubber fastening block 33 fixed to the end of the transmission rod 32 for clamping the lower leg rod 12.

[0007] Furthermore, the number of pneumatic muscles 13 is two, and each of them is connected to the pneumatic muscle connecting seat 14 at both ends; The pneumatic muscle connector 14 is hinged to the thigh bar 11 and the calf bar 12 respectively.

[0008] Furthermore, based on the different gait cycles of human walking, the expansion and contraction of the pneumatic muscles 13 located on both sides are controlled to realize the relative movement of the thigh bar 11 and the lower leg bar 12, thereby matching the human walking gait; wherein, the gait cycle includes a support phase and a swing phase.

[0009] Furthermore, when the gait cycle is in the support phase, the two pneumatic muscles 13 are inflated, undergoing radial expansion and axial contraction deformation, and simultaneously generating the same symmetrical tension, increasing the pressure of the spherical inner shell 22 on the hemispherical outer shell 21; at the same time, the lower leg rod 12 drives the top plate 31 to move through the transmission rod 32; the rubber fastening block 33 at the end of the transmission rod 32 moves in the radial direction of the lower leg rod 12 and clamps the lower leg rod 12.

[0010] Furthermore, when the gait cycle is in the swing phase, one pneumatic muscle 13 is deflated, which undergoes radial contraction and axial elongation deformation, while generating a small tension F1; another pneumatic muscle 13 is inflated, which undergoes radial expansion and axial contraction deformation, while generating a larger tension F2; F1 and F2 antagonistically form a driving torque, causing the lower leg rod 12 to rotate, completing the flexion movement.

[0011] Furthermore, the arcuate protrusion 222 at the top of the spherical inner shell 22 has the same curvature as the arcuate groove 211 of the hemispherical outer shell 21. When the gait cycle is in the support phase, the arcuate protrusion 222 abuts against the arcuate groove 211, limiting the relative displacement of the two to provide rigid support.

[0012] Secondly, the present invention provides a control system based on the rigid-flexible coupling knee joint structure, the control system including a gait phase estimation module, a PD control module, a sensor module, an air source module, and an execution module; The sensor module is used to collect pressure data and joint angle data of the forefoot and hindfoot areas of the sole, and send the collected data to the gait phase estimation module. The gait phase estimation module is used to calculate the continuous gait phase value corresponding to the current moment based on the pressure data and joint angle data collected by the sensor module, using the least squares method to fit the constructed function model, and send the gait phase value to the PD control module. The PD control module calculates the desired tension of the pneumatic muscle 13 based on the current gait phase value and the joint total recovery torque model, and calculates the corresponding air pressure control command through the proportional-derivative control law based on the error between the desired tension and the actual tension. The air source module is used to provide air pressure for the pneumatic muscle 13; The execution module is used to control the inflation and deflation of the pneumatic muscle 13 according to the air pressure control command output by the PD control module, thereby adjusting the output tension of the pneumatic muscle 13 to achieve auxiliary drive for the rigid-flexible coupled knee joint.

[0013] Thirdly, the present invention also provides a control method based on a rigid-flexible coupling knee joint structure control system, comprising the following steps: S1 collects human gait data: The sensor module synchronously collects pressure data and joint angle data of the forefoot and hindfoot areas as initial data. The initial data is then processed by a filtering algorithm to remove noise, and feature parameters reflecting gait temporal changes are then extracted. S2 performs gait phase estimation: The feature parameters are fitted using the least squares method to establish a functional mapping relationship between the feature parameters and the gait phase; wherein, the functional mapping relationship is used to calculate the continuous gait phase value corresponding to the current moment in real time based on the feature parameters; S3 establishes a model of the total restoring moment of the joint: Based on the continuous gait phase values, a dynamic analysis of the desired joint rotation angle is performed to establish a relationship model between the restoring torque of the elastic element and the joint rotation angle, i.e., the total restoring torque model of the joint. S4 calculates the expected tension of a pneumatic muscle: The joint input torque is the product of the difference in the expected tension of the two pneumatic muscles and the equivalent force arm length. Based on the joint total restoring torque model, the joint input torque and the joint total restoring torque generated by the elastic element satisfy the torque balance relationship, so the relationship between the expected tension difference and the expected joint rotation angle can be obtained, and thus the expected tension of the two pneumatic muscles can be obtained. S5 performs PD closed-loop control: The actual output tension of the pneumatic muscle is obtained, and the difference between the expected tension and the actual output tension of the pneumatic muscle is used as the control error; the corresponding air pressure control command is calculated using a proportional-derivative control law; wherein, the air pressure control command is used to adjust the inflation pressure or deflation rate of the pneumatic muscle by the execution module. S6 outputs control signals and enables walking assistance: The air pressure control command is output to the execution module to control the inflation and deflation of the pneumatic muscles, thereby driving the joint to output the corresponding auxiliary torque; thus, the next stage is when the patient's left leg begins to land and the right leg is about to leave the ground, a flexion movement is performed; repeating this cycle, the two sets of this mechanism installed on the patient's left and right legs can conform to the human gait cycle and provide walking assistance to the human body.

[0014] Furthermore, in step S2, the function mapping relationship is specifically used to calibrate the gait phase based on the following rules: The moment when the pressure in the hindfoot area changes abruptly from zero and continues to rise is defined as the starting point of the gait cycle, corresponding to the early stage of the support phase; the interval when the overall plantar pressure reaches its peak and remains high is mapped to the middle stage of the support phase; the moment when the pressure in the hindfoot area decreases to near zero while the pressure in the forefoot area remains at its output is mapped to the push-off phase, corresponding to the late stage of the support phase; the interval when the pressure in all areas of the plantar area is below a set threshold is mapped to the swing phase, and the specific phase value of the swing phase is defined based on joint angle data.

[0015] Furthermore, in step S3, the total restoring torque model of the joint is obtained specifically through the following method: axial tension With axial deformation The relationship between them is linear, and the restoring torque generated by a single elastic element about the axis of rotation is... The distance from the point of action of the elastic element to the joint axis of rotation. With the axial tensile force The product of , then The total restoring torque generated by the elastic element That is Restoring torque generated by the elastic element The sum of these is the model of the total restoring torque of the joint. Wherein, the axial deformation Specifically, it refers to the distance of the joint's rotation axis. With joint angle The product of.

[0016] Compared with the prior art, the beneficial effects of the present invention are reflected in: (1) The present invention adopts a rigid-flexible coupling joint structure composed of a hemispherical outer shell, a spherical inner shell and multiple elastic elements, which enables the knee joint mechanism to have a certain range of passive motion capability during the swing phase, thereby improving the adaptability of the exoskeleton mechanism to the natural gait of the human body.

[0017] (2) The present invention forms a stable support structure during the human gait support phase by using the combination of arc-shaped protrusions and arc-shaped grooves, the locking of rubber fasteners, and the tightening effect of pneumatic muscles on both sides, thereby improving the support stability between the thigh bar and the calf bar.

[0018] (3) In the process of human gait support phase and swing phase, the matching state of the arc-shaped protrusion and the arc-shaped groove, the locking state of the rubber fastener and the tension state of the pneumatic muscle are automatically changed with the change of gait mechanics environment, realizing the switching of the joint from the support state to the compliant movement state, so that the exoskeleton joint can adapt to the cyclical changes of human gait.

[0019] (4) The present invention adopts a bilateral artificial pneumatic muscle antagonistic drive mode. By controlling the inflation and deflation of the artificial pneumatic muscles, the auxiliary torque of the knee joint is output. At the same time, by introducing a reference tension and adopting an antagonistic distribution mode, the artificial pneumatic muscles are always in the effective stretching working range, thereby avoiding control failure or system instability due to insufficient tension on one side.

[0020] (5) The present invention further combines a gait phase estimation method based on plantar pressure data and joint angle data, and constructs a PD closed-loop control strategy based on the joint total restoring torque model, thereby improving the stability and control accuracy of the artificial pneumatic muscle drive system. Attached Figure Description

[0021] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the overall structure of this mechanism under gait support phase; Figure 2 This is a schematic diagram of the overall structure of the mechanism during the gait swing phase; Figure 3 This is a schematic diagram of the mechanism of the suspension multi-directional swing module and the natural locking module of this device; Figure 4 This is a schematic diagram of the gait phase estimation process of our organization; Figure 5 This is a schematic diagram of the control process of this organization; Figure 6 This is a schematic diagram of the PD control method of our organization; Reference numerals: Exoskeleton component 1, thigh bar 11, calf bar 12, pneumatic muscle 13, pneumatic muscle connector 14, power supply 15, controller 16; Swing component 2, hemispherical outer shell 21, spherical inner shell 22, elastic element 23, angle sensor 24, arc-shaped groove 211, receiving groove 221, arc-shaped protrusion 222; Support and locking component 3, top plate 31, transmission rod 32, rubber fastening block 33. Detailed Implementation

[0022] Preferred embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. Any person may implement the present disclosure in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0023] Based on the spatial changes in the biological structure of the human knee joint during phase transitions and the coordinated motion characteristics of the surrounding soft tissues, combined with its biological and mechanical properties, this invention provides a rigid-flexible coupled joint mechanism with human-like motion characteristics and biomimetic gait, and optimizes its constraints and configuration features. By analyzing the changes in rigidity and flexibility during the transition from the knee joint's support phase to the swing phase, a joint mechanism that can change its stiffness according to the gait phase is designed, and a drive structure is developed using flexible artificial pneumatic muscles as actuators. This invention uses the knee joint as a typical example for biomimetic design, providing a demonstration case and methodological reference for the flexible biomimetic control of rehabilitation robots, and helping to promote the solution of major problems such as poor compliance and fuzzy control.

[0024] Based on the aforementioned rigid-flexible coupled knee joint structure, this invention further constructs a corresponding control method to achieve reasonable drive and stable control of the joint under different gait phases. This control method uses plantar pressure signals and joint angle signals as the main sensing information to monitor the wearer's current gait state in real time. Gait phase discrimination is achieved through analysis of plantar pressure change characteristics. Based on the gait phase discrimination results, combined with the mapping model between the desired joint rotation angle and the desired tension of the artificial pneumatic muscle, the required auxiliary torque for each gait phase is determined. A proportional-derivative (PD) control algorithm is then used to perform closed-loop adjustment of the output of the artificial pneumatic muscle, ensuring that its actual output torque follows the desired torque change, thereby achieving compliant movement and stable assistance of the knee joint during phase switching.

[0025] In a first aspect, the present invention provides a rigid-flexible coupled knee joint structure based on gait phase switching laws, such as... Figure 1 and Figure 2 As shown, the mechanism includes an exoskeleton assembly 1, a swing assembly 2, and a support and locking assembly 3.

[0026] The exoskeleton component 1 is the main component, primarily serving a supporting and driving function. It includes a thigh rod 11, a lower leg rod 12, pneumatic muscles 13, a pneumatic muscle connector 14, a power supply 15, and a controller 16. The thigh rod 11 and lower leg rod 12 primarily provide support; the thigh rod 11 is fixed to the patient's thigh, and the lower leg rod 12 is fixed to the patient's lower leg. The thigh rod 11 and lower leg rod 12 are connected via the pneumatic muscles 13 and the pneumatic muscle connector 14, providing a driving function. Inflating and deflating the pneumatic muscles 13 causes them to expand or contract, thus causing relative movement of the lower leg rod 12 relative to the thigh rod 11. There are two pneumatic muscles 13, with their ends hinged to the thigh rod 11 and lower leg rod 12 respectively via the pneumatic muscle connector 14. Taking the walking direction as the forward direction, the pneumatic muscle 13 located in front of the knee joint is defined as the anterior pneumatic muscle, and the pneumatic muscle 13 located behind the knee joint is defined as the posterior pneumatic muscle.

[0027] like Figure 3 and Figure 4 As shown, the swing assembly 2 includes a hemispherical outer shell 21, a spherical inner shell 22, elastic elements 23, and an angle sensor 24. The hemispherical outer shell 21 is connected to the bottom end of the thigh bar 11. The spherical inner shell 22 is suspended within the hemispherical outer shell 21 by multiple elastic elements 23, allowing the spherical inner shell 22 to rotate freely within a certain range of motion within the hemispherical outer shell 21. Several elastic elements 23 are provided, each connected to the inner surface of the hemispherical outer shell 21 and the outer surface of the spherical inner shell 22. The design of the elastic elements 23 limits the range of motion of the spherical inner shell 22 within the hemispherical outer shell 21 and provides appropriate elastic support, thereby enabling the knee joint mechanism to possess multi-directional passive rotation capabilities that conform to the human walking gait.

[0028] In addition, the hemispherical outer shell 21 has a concave arc-shaped groove 211 at the top; the spherical inner shell 22 has a concave receiving groove 221, and its top is also provided with an outward arc-shaped protrusion 222; the arc-shaped groove 211 and the arc-shaped protrusion 222 have the same curvature and can fit together perfectly.

[0029] The support and locking assembly 3 includes a top plate 31, a transmission rod 32, and a rubber fastening block 33; the support and locking assembly 3 is installed in the receiving groove 221. The top plate 31 is fixedly installed on the top end of the lower leg rod 12, the transmission rod 32 connects the spherical inner shell 22 and the top plate 31, and the rubber fastening block 33 is fixed to the end of the transmission rod 32 for clamping the lower leg rod 12.

[0030] Therefore, patients should have two sets of the aforementioned rigid-flexible coupling knee joint mechanism when using it, and install the two sets of the mechanism on the left and right legs respectively.

[0031] Before the patient begins walking, both legs are in the gait support phase. At this time, the four pneumatic muscles 13 controlling the two mechanisms are inflated, causing the four pneumatic muscles 13 to simultaneously undergo radial expansion and axial contraction deformation, generating two pairs of identical symmetrical tensions. These two pairs of symmetrical tensions increase the pressure of the spherical inner shell 22 on the hemispherical outer shell 21. At the same time, the perfect fit between the arc-shaped protrusion 222 at the top of the spherical inner shell 22 and the arc-shaped groove 211 at the top of the hemispherical outer shell 21 provides better support and makes it less likely for the spherical inner shell 22 and the hemispherical outer shell (21) to slide relative to each other.

[0032] When the patient begins to walk, the right leg flexes first, while the left leg remains in the gait support phase. At this time, the pneumatic muscle 13 at the front end of the mechanism on the right leg is deflated, undergoing radial contraction and axial elongation, generating a small tension F1; the pneumatic muscle 13 at the rear end is inflated, undergoing radial expansion and axial contraction, generating a larger tension F2. F1 and F2 antagonistically form a driving torque, causing the lower leg bar 12 to deflect backward relative to the thigh bar 11, thus conforming to the flexion movement of the knee joint.

[0033] As the patient's right leg begins to land, the patient's left leg is about to leave the ground and begin flexion. At this time, the pneumatic muscle 13 at the front end of the mechanism on the right leg is inflated, undergoing radial expansion and axial contraction deformation, generating a large tension F1; the pneumatic muscle 13 at the rear end is slowly deflated, undergoing radial contraction and axial elongation deformation, generating a smaller tension F2. F1 and F2 antagonistically form a driving torque, causing the lower leg bar 12 to slowly return to its upright position, bringing the mechanism towards the support phase. At this time, the pneumatic muscle 13 at the front end of the mechanism on the left leg is deflated, undergoing radial contraction and axial elongation deformation, generating a smaller tension F1; the pneumatic muscle 13 at the rear end is still inflated, undergoing radial expansion and axial contraction deformation, generating a larger tension F2. F1 and F2 antagonistically form a driving torque, causing the lower leg bar 12 to deflect backward relative to the thigh bar 11, thus conforming to the flexion movement of the human knee joint. Therefore, the patient's right leg is in the gait support phase, and the left leg is in the gait swing phase.

[0034] Secondly, to achieve stable output and control of artificial pneumatic muscle-driven joints in human assistance scenarios, this invention proposes a control method for a rigid-flexible coupled knee joint structure based on gait phase switching laws, specifically a PD control method based on the joint total restoring torque model. This method starts from the equivalent restoring torque generated by the elastic element, gradually establishing a mapping relationship between the desired joint torque and the artificial pneumatic muscle tension, and constructs a PD control strategy based on this relationship.

[0035] like Figure 5 As shown, the control system of the present invention includes a gait phase estimation module, a PD control module, a sensor module, a gas source module, and an execution module.

[0036] The sensor module is used to collect pressure data and joint angle data of the forefoot and hindfoot areas of the foot, and send the collected data to the gait phase estimation module.

[0037] The gait phase estimation module is used to calculate the continuous gait phase value corresponding to the current moment based on the pressure data and joint angle data collected by the sensor module, using the least squares method to fit the constructed function model, and then send the gait phase value to the PD control module.

[0038] The PD control module calculates the desired tension of the artificial pneumatic muscle based on the current gait phase value and the joint total restoring torque model, and calculates the corresponding air pressure control command through the proportional-derivative control law based on the error between the desired tension and the actual tension.

[0039] The air source module is used to provide air pressure for the pneumatic muscle 13.

[0040] The execution module is used to control the inflation and deflation of the pneumatic muscle 13 according to the air pressure control command output by the PD control module, thereby adjusting the output tension of the pneumatic muscle 13 to achieve auxiliary drive for the rigid-flexible coupled knee joint.

[0041] The control method includes the following steps: S1. Collect human gait data: In the signal preprocessing stage, the sensor module synchronously collects pressure data and joint angle data of the forefoot and hindfoot areas as initial data. The initial data is then processed by a filtering algorithm to remove noise, and feature parameters reflecting gait temporal changes are then extracted. Specifically, the sensor module is a thin-film pressure sensor, made by curing nano-force-sensitive materials onto a flexible thin-film substrate. It can be attached to the surface of the insole and placed inside the shoe without affecting normal gait. The thin-film pressure sensor employs a distributed array design of 6 rows by 4 columns. When subjected to pressure, each sensing unit can be considered a piezoresistive resistor; the resistance decreases as the pressure increases, exhibiting a piezoresistive characteristic where conductivity and pressure show an approximately linear relationship. The sensor has a single-point range of 0-70 kg, a thickness of less than 0.3 mm, a conductivity-pressure linearity of ±3%, and an operating temperature range of -50℃ to 50℃, demonstrating high accuracy and good flexibility.

[0042] S2. Perform gait phase estimation: Based on the feature parameters obtained in step S1, the corresponding data of the feature parameters are regressed and fitted using the least squares method to establish a functional mapping relationship between the feature parameters and the gait phase.

[0043] Specifically, the function mapping relationship is used to calculate the continuous gait phase value corresponding to the current moment in real time based on the feature parameters.

[0044] Specifically, when constructing the function mapping relationship, the gait phase is calibrated based on the following rules: The moment when the pressure in the hindfoot area changes abruptly from zero and continues to rise is defined as the starting point of the gait cycle, corresponding to the early stage of the support phase; the interval when the overall plantar pressure reaches its peak and remains high is mapped to the middle stage of the support phase; the moment when the pressure in the hindfoot area decreases to near zero while the pressure in the forefoot area remains at its output is mapped to the push-off phase, corresponding to the late stage of the support phase; the interval when the pressure in all areas of the plantar area is below a set threshold is mapped to the swing phase, and the specific phase value of the swing phase is defined based on joint angle data.

[0045] S3. Establish the joint total restoring moment model: Based on the continuous gait phase value corresponding to the current moment obtained in step S2, a dynamic analysis is performed on the expected joint rotation angle to establish a relationship model between the restoring torque of the elastic element and the joint rotation angle.

[0046] First, the mechanical properties of a single elastic element are modeled and analyzed: the single elastic element is equivalent to a linear elastic element, which approximately conforms to Hooke's Law under small deformation and normal temperature.

[0047] According to Hooke's Law, its axial tensile force With axial deformation The linear relationship between them can be expressed as: in, This refers to the equivalent elastic coefficient of a single elastic element. It represents the axial elongation of the elastic element in the direction of the applied force.

[0048] Furthermore, the elastic elements are uniformly arranged along the outer periphery of the hemispherical shell at the bottom of the joint. Each elastic element has the same length, and the distance from its point of action to the joint axis of rotation is equal. This distance is taken as the equivalent force arm length of the torque generated by the elastic element on the joint, denoted as . When a joint undergoes joint rotation... When the elastic element elongates, the axial elongation can be expressed as: Substituting equation (2) into equation (1), we obtain the axial tensile force. With joint angle The relationship between them.

[0049] Therefore, the restoring torque generated by a single elastic element about the axis of rotation As shown below: As can be seen from equation (3), under small-angle working conditions, the restoring torque generated by a single elastic element is linearly related to the joint rotation angle.

[0050] Furthermore, in this invention, the joint structure is provided with multiple elastic elements, all of which are identical in structural parameters and generate restoring torques in the same direction. Let the number of elastic elements be... Under these structural conditions, the total restoring torque generated by the joint is: Define the equivalent rotational stiffness of the joint as Therefore, the total restoring torque of the joint can be expressed as: Equation (4) or (5) is the model of the total restoring torque of the joint.

[0051] S4. Calculate the expected tension of the pneumatic muscle: In this invention, the pneumatic muscle 13 applies an input torque to the joint via a connecting rod. Based on the joint total restoring torque model established in step S3, the desired tensile forces output by the two antagonistically arranged pneumatic muscles are defined as follows: and The equivalent force arm length of the pneumatic muscle tension applied to the joint axis is... Therefore, the joint input torque generated by the pneumatic muscles at the joint axis of rotation... It can be represented as: Under steady-state or quasi-steady-state control conditions, the joint input torque The total restoring torque of the joint generated by the elastic element The torque balance relationship is satisfied, that is: Substituting equations (5) and (6) into equation (7), we get: in, Let be the desired rotation angle of the joint.

[0052] This yields the desired tension difference and the desired joint rotation angle. The relationship between them is: To ensure that the pneumatic muscle remains within its effective stretching range and to prevent control failure or decreased system stability due to insufficient tension, this invention introduces a constant reference tension when calculating the desired tension. The desired tension of the two pneumatic muscles is distributed using an antagonistic distribution method.

[0053] Furthermore, based on equation (9), the desired tension of the pneumatic muscles on both the front and rear sides can be expressed as follows: S5. Perform PD closed-loop control: The actual output tension of the pneumatic muscle is obtained, and the difference between the expected tension and the actual output tension of the pneumatic muscle obtained in step S4 is used as the control error. The corresponding air pressure control command is calculated using a proportional-derivative control law, and the air pressure control command is output to the execution module to realize the closed-loop regulation of the pneumatic muscle tension. The air pressure control command is used to adjust the inflation pressure or deflation rate of the pneumatic muscle by the execution module.

[0054] like Figure 6 As shown, in the engineering practice of this invention, the control input air pressure value of the pneumatic muscle is assumed to be... The pneumatic muscle outputs tensile force The relationship between air pressure and air pressure is approximately linear: in, The force output by the pneumatic muscle is k, which is the force-pressure conversion coefficient of the pneumatic muscle.

[0055] Based on the above relationship, this invention uses the output force of pneumatic muscles as the intermediate control variable and air pressure as the final execution variable to construct a PD control system based on force feedback. The force errors of the two pneumatic muscles are defined as follows: in, and These represent the tension error of the two pneumatic muscles, respectively. and These represent the actual output tension of the two pneumatic muscles.

[0056] The pressure control input calculated using the PD control law can be expressed as: in, and These are the air pressure control inputs corresponding to the two pneumatic muscles. This is the proportional control coefficient. Differential control coefficient Or, in matrix form, it can be simplified as follows: Furthermore, by analyzing the dynamic response characteristics of pneumatic muscles and the periodic characteristics of human gait, and combining the experimental test results, the PD control parameters selected by this invention in the actual control process are as follows: By using the above parameter settings, the force output oscillation can be effectively suppressed while ensuring the system response speed, thereby improving the stability and control accuracy of the pneumatic muscle drive system.

[0057] S6, Output control signal and implement walking assistance: The air pressure control command calculated in step S5 is output to the execution module to control the inflation and deflation of the pneumatic muscles, thereby driving the joint to output the corresponding auxiliary torque. Thus, the next stage involves the patient's left leg beginning to land and the right leg about to leave the ground, at which point a flexion movement is performed. This movement is repeated cyclically, and the two sets of this mechanism installed on the patient's left and right legs can adapt to the human gait cycle and provide walking assistance.

[0058] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0059] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0060] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A rigid-flexible coupled knee joint structure based on gait phase switching law, characterized in that, include: The exoskeleton assembly (1), the swing assembly (2), and the support locking assembly (3) are respectively fixed to the patient's thigh and calf. The exoskeleton assembly (1) includes a thigh rod (11) and a calf rod (12) fixed to the patient's thigh and calf respectively, and pneumatic muscles (13) and pneumatic muscle connectors (14) for connecting the thigh rod (11) and the calf rod (12), as well as a power supply (15) and a controller (16) placed on the thigh rod (11). The swing assembly (2) includes a hemispherical shell (21) connected to the bottom end of the thigh rod (11), a spherical inner shell (22) suspended within the hemispherical shell (21), and a support locking assembly (3) for connecting the hemispherical shell (21). 1) and multiple elastic elements (23) of the spherical inner shell (22), including an angle sensor (24); the top of the hemispherical outer shell (21) is provided with a concave arc-shaped groove (211); the spherical inner shell (22) is provided with a concave receiving groove (221) and an outwardly convex arc-shaped protrusion (222) at the top end; the support locking assembly (3) includes a top plate (31) fixed to the top end of the lower leg rod (12), multiple transmission rods (32) rotatably connected to the spherical inner shell (22) and the top plate (31), and a rubber fastening block (33) fixed to the end of the transmission rod (32) for clamping the lower leg rod (12).

2. The rigid-flexible coupling knee joint structure according to claim 1, characterized in that, The number of pneumatic muscles (13) is two, and each of them is connected to the pneumatic muscle connecting seat (14) at both ends; the pneumatic muscle connecting seat (14) is hinged to the thigh rod (11) and the calf rod (12) respectively.

3. The rigid-flexible coupling knee joint structure according to claim 1 or 2, characterized in that, According to the different gait cycles of human walking, the expansion and contraction of the pneumatic muscles (13) located on both sides are controlled to realize the relative movement of the thigh bar (11) and the lower leg bar (12), thereby matching the human walking gait; wherein, the gait cycle includes a support phase and a swing phase.

4. The rigid-flexible coupled knee joint structure according to claim 3, characterized in that, When the gait cycle is in the support phase, the two pneumatic muscles (13) are inflated, and they undergo radial expansion and axial contraction deformation, while generating the same symmetrical tension, increasing the pressure of the spherical inner shell (22) on the hemispherical outer shell (21); at the same time, the lower leg rod (12) drives the top plate (31) to move through the transmission rod (32); the rubber fastening block (33) at the end of the transmission rod (32) moves in the radial direction of the lower leg rod (12) and clamps the lower leg rod (12).

5. The rigid-flexible coupling knee joint structure according to claim 3, characterized in that, When the gait cycle is in the swing phase, one pneumatic muscle (13) is deflated, which undergoes radial contraction and axial elongation deformation, and at the same time generates a small tension F1; another pneumatic muscle (13) is inflated, which undergoes radial expansion and axial contraction deformation, and at the same time generates a large tension F2; F1 and F2 antagonistically form a driving torque, causing the lower leg rod (12) to rotate and complete the flexion movement.

6. The rigid-flexible coupled knee joint structure according to claim 1, characterized in that, The arc-shaped protrusion (222) at the top of the spherical inner shell (22) has the same curvature as the arc-shaped groove (211) of the hemispherical outer shell (21). When the gait cycle is in the support phase, the arc-shaped protrusion (222) abuts against the arc-shaped groove (211) to limit the relative displacement of the two to provide rigid support.

7. A rigid-flexible coupling knee joint structure control system based on any one of claims 1 to 6, characterized in that, The control system includes a gait phase estimation module, a PD control module, a sensor module, a gas source module, and an execution module; The sensor module is used to collect pressure data and joint angle data of the forefoot and hindfoot areas of the sole, and send the collected data to the gait phase estimation module. The gait phase estimation module is used to calculate the continuous gait phase value corresponding to the current moment based on the pressure data and joint angle data collected by the sensor module, using the least squares method to fit the constructed function model, and send the gait phase value to the PD control module. The PD control module calculates the desired tension of the pneumatic muscle (13) based on the current gait phase value and the joint total recovery torque model, and calculates the corresponding air pressure control command by means of the proportional-derivative control law based on the error between the desired tension and the actual tension. The air source module is used to provide air pressure for the pneumatic muscle (13); The execution module is used to control the inflation and deflation of the pneumatic muscle (13) according to the air pressure control command output by the PD control module, thereby adjusting the output tension of the pneumatic muscle (13) to achieve auxiliary drive for the rigid-flexible coupled knee joint.

8. A control method for a rigid-flexible coupling knee joint structure control system based on claim 7, characterized in that, Includes the following steps: S1 collects human gait data: The sensor module synchronously collects pressure data and joint angle data of the forefoot and hindfoot areas as initial data. The initial data is then processed by a filtering algorithm to remove noise, and feature parameters reflecting gait temporal changes are then extracted. S2 performs gait phase estimation: The feature parameters are fitted using the least squares method to establish a functional mapping relationship between the feature parameters and the gait phase; wherein, the functional mapping relationship is used to calculate the continuous gait phase value corresponding to the current moment in real time based on the feature parameters; S3 establishes a model of the total restoring moment of the joint: Based on the continuous gait phase values, a dynamic analysis of the desired joint rotation angle is performed to establish a relationship model between the elastic restoring torque and the joint rotation angle, i.e., the total joint restoring torque model. S4 calculates the expected tension of a pneumatic muscle: The joint input torque is the product of the difference in the expected tension of the two pneumatic muscles and the equivalent force arm length. Based on the joint total restoring torque model, the joint input torque and the joint total restoring torque generated by the elastic element satisfy the torque balance relationship, so the relationship between the expected tension difference and the expected joint rotation angle can be obtained, and thus the expected tension of the two pneumatic muscles can be obtained. S5 performs PD closed-loop control: The actual output tension of the pneumatic muscle is obtained, and the difference between the expected tension and the actual output tension of the pneumatic muscle is used as the control error; the corresponding air pressure control command is calculated using a proportional-derivative control law; wherein, the air pressure control command is used to adjust the inflation pressure or deflation rate of the pneumatic muscle by the execution module. S6 outputs control signals and enables walking assistance: The air pressure control command is output to the execution module to control the inflation and deflation of the pneumatic muscles, thereby driving the joint to output the corresponding auxiliary torque; thus, the next stage is when the patient's left leg begins to land and the right leg is about to leave the ground, a flexion movement is performed; repeating this cycle, the two sets of this mechanism installed on the patient's left and right legs can conform to the human gait cycle and provide walking assistance to the human body.

9. The method according to claim 8, characterized in that, In step S2, the function mapping relationship is specifically used to calibrate the gait phase based on the following rules: The moment when the pressure in the hindfoot area changes abruptly from zero and continues to rise is defined as the starting point of the gait cycle, corresponding to the early stage of the support phase; the interval when the overall plantar pressure reaches its peak and remains high is mapped to the middle stage of the support phase; the moment when the pressure in the hindfoot area decreases to near zero while the pressure in the forefoot area remains at its output is mapped to the push-off phase, corresponding to the late stage of the support phase; the interval when the pressure in all areas of the plantar area is below a set threshold is mapped to the swing phase, and the specific phase value of the swing phase is defined based on joint angle data.

10. The method according to claim 8, characterized in that, In step S3, the total restoring moment model of the joint is obtained specifically through the following method: axial tension With axial deformation The relationship between them is linear, and the restoring torque generated by a single elastic element about the axis of rotation is... The distance from the point of action of the elastic element to the joint axis of rotation. With the axial tensile force The product of , then The total restoring torque generated by the elastic element That is Restoring torque generated by the elastic element The sum of these is the model of the total restoring torque of the joint. Wherein, the axial deformation Specifically, it refers to the distance of the joint's rotation axis. With joint angle The product of.

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