Rigid-flexible coupling three-dimensional motion device for ankle rehabilitation and control method thereof

Abstract

The present application relates to a rigid-flexible coupling three-dimensional motion device for ankle rehabilitation and a control method thereof, the device comprising a six-degree-of-freedom parallel mechanism, a pneumatic flexible actuator and a control system; the six-degree-of-freedom parallel mechanism comprises a base, an intermediate moving platform and six SPS branch chains, for realizing the plantar flexion / dorsal flexion and inversion / eversion motion of the ankle joint; the pneumatic flexible actuator comprises a lower plate mounted on the intermediate moving platform, the lower plate is rotatably provided with an upper plate, two air bag assemblies are symmetrically arranged between the upper plate and the lower plate, and the unilateral air bag is inflated alternately to push the upper plate to flexibly rotate around the central axis, thereby realizing the adduction / abduction motion of the ankle joint; the control system is used for sending instructions and driving the six-degree-of-freedom parallel mechanism and the pneumatic flexible actuator to move according to a preset trajectory. The present application combines the rigid large-load parallel mechanism with the flexible pneumatic mechanism, completely covers the three-dimensional rehabilitation motion of the ankle, and has the advantages of compact structure, high safety, smooth human-computer interaction and the like.

Description

Technical Field

[0001] This invention relates to the field of medical device technology, and in particular to a rigid-flexible coupled three-dimensional motion device for ankle joint rehabilitation and its control method. Background Technology

[0002] The ankle joint, as a vital weight-bearing and movement hub, bears the load and adjusts posture during walking, running, and jumping. It also performs multi-dimensional complex movements such as dorsiflexion, plantarflexion, inversion, and eversion, playing an irreplaceable role in daily activities. Ankle injuries often result in stiffness and decreased stability. Therefore, scientific and effective rehabilitation treatment is crucial for restoring ankle function and preventing chronic injuries.

[0003] Parallel mechanisms, with their advantages of high rigidity, high positioning accuracy, and strong load-bearing capacity, are widely used in ankle joint rehabilitation training equipment. However, to achieve full-dimensional ankle joint rehabilitation training, existing multi-degree-of-freedom ankle joint rehabilitation robots generally adopt all-metal parallel structures or spherical structures. This not only leads to complex structures and high manufacturing costs, but also results in excessively high equivalent stiffness and poor human-machine interaction compliance. In addition, existing ankle joint rehabilitation robots generally use rigid drive mechanisms, and the mechanism body does not have inherent physical compliance characteristics. Therefore, ankle joint rehabilitation robots are prone to outputting uncontrollable interactive forces during operation. Especially when performing yaw rehabilitation movements such as ankle adduction and abduction, if the preset movement trajectory of the mechanism deviates from the actual bone movement trajectory of the human ankle joint, it is very easy to apply a large rigid shear force to the ankle joint. This not only causes discomfort to patients during rehabilitation training, but also poses a safety hazard of causing soft tissue strain and secondary injury.

[0004] To address the safety issues associated with rigid actuation, researchers have recently proposed several ankle rehabilitation devices incorporating flexible actuation. For example, patent document CN108245372A discloses a three-degree-of-freedom ankle rehabilitation robot driven by a combination of pneumatic muscles and flexible cables. This robot utilizes pneumatic muscle actuation, combining flexible cables and pulley mechanisms to change the direction of the pneumatic muscle's auxiliary output, effectively expanding the robot's range of motion and improving the mechanism's safety and compliance while ensuring auxiliary output. Patent document CN105105970A discloses a parallel ankle rehabilitation robot and its control method, using pneumatic muscles or linear motors as actuators to directly pull the lower platform. Patent document CN113332678A discloses a parallel ankle rehabilitation system and its control method with flexible pneumatic muscle actuation. This system uses multiple sets of pneumatic muscles to construct parallel drive units to drive the footrest module, leveraging the compressibility of the pneumatic muscles to give the mechanism physical compliance.

[0005] While the aforementioned devices improve the physical compliance of the system to some extent by introducing purely flexible components such as pneumatic muscles and flexible cables, they also expose new technical shortcomings: purely flexible drive systems (such as all-pneumatic muscles or flexible cable traction) often suffer from insufficient overall structural support stiffness, limited load-bearing capacity, and strong system nonlinearity. Particularly for primary motion dimensions such as plantar flexion / dorsiflexion, which require large support torques, purely flexible mechanisms are prone to motion hysteresis and trajectory deformation, making it difficult to achieve high-precision trajectory interpolation and dynamic control under multi-axis linkage. Therefore, there is an urgent need to develop a three-dimensional rehabilitation training device that can guarantee high-precision, high-load-bearing active motion trajectories while also considering the compliant interaction capabilities in specific dimensions. Summary of the Invention

[0006] This invention provides a rigid-flexible coupled three-dimensional motion device and its control method for ankle joint rehabilitation, solving the problems existing in the prior art. This application combines a rigid, high-load-bearing mechanism with a flexible pneumatic mechanism, and uses an interpolation algorithm for precise linkage control. This not only comprehensively covers the three dimensions of ankle rehabilitation movements, but also has advantages such as compact structure, high safety, and smooth human-computer interaction, significantly improving patient comfort and safety during rehabilitation training.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a rigid-flexible coupled three-dimensional motion device for ankle joint rehabilitation, comprising a six-degree-of-freedom parallel mechanism, a pneumatic flexible actuator, and a control system; the six-degree-of-freedom parallel mechanism includes a base and an intermediate moving platform, wherein six SPS branches distributed in a Stewart configuration are provided between the base and the intermediate moving platform, wherein the P pair is a driving pair; the pneumatic flexible actuator includes a lower plate fixedly mounted on the intermediate moving platform, an upper plate rotatably mounted on the lower plate, and two airbag assemblies symmetrically arranged between the lower plate and the upper plate, wherein the upper plate is driven to rotate smoothly by inflating and deflating the airbags in the airbag assemblies; the control system drives the six-degree-of-freedom parallel mechanism and the pneumatic flexible actuator to move, wherein the six-degree-of-freedom parallel mechanism is used to perform plantar flexion or dorsiflexion and inversion or eversion movements of the ankle joint, and the pneumatic flexible actuator is used to perform adduction or abduction movements of the ankle joint.

[0009] Furthermore, the SPS branch includes a lower ball joint, an L-shaped connector, an electric push rod, a sleeve connector, and an upper ball joint. The lower ball joint is located at the upper end of the base, and the upper ball joint is located at the lower end of the intermediate moving platform. The lower end of the electric push rod is connected to the lower ball joint through the L-shaped connector, and the upper end is connected to the upper ball joint through the sleeve connector.

[0010] Furthermore, the airbag assembly includes a lower baffle disposed at the upper end of the lower plate and an upper baffle disposed at the lower end of the upper plate, with an arc-shaped airbag between the lower baffle and the upper baffle, and an air hole communicating with the interior of the airbag on the lower baffle.

[0011] Furthermore, the upper plate is connected to the lower plate via a rotary support assembly, the rotary support assembly including a central shaft disposed at the center of the lower plate, the central shaft being provided with a bearing and a retaining ring, and the lower end center of the upper plate being provided with a bearing seat for mounting the bearing.

[0012] Furthermore, the control system includes a host computer and an attitude detection module. The host computer is connected to slave computer A and slave computer B respectively. Each electric push rod is equipped with a motor driver, which is connected to slave computer A. Slave computer A controls the extension and retraction of the six electric push rods through pulse signals and direction signals. The airbag is connected to a solenoid valve and a miniature brushless diaphragm air pump in sequence through an air path. Slave computer B is connected to the miniature brushless diaphragm air pump and a multi-channel relay module respectively. The multi-channel relay module is connected to the solenoid valve. The attitude detection module includes a dual-axis tilt sensor connected to slave computer A and a rotation angle sensor connected to slave computer B. The dual-axis tilt sensor is set at the center of the lower end of the intermediate moving platform and is used to detect the actual rotation angle of the intermediate moving platform around the X-axis and Y-axis in three-dimensional space in real time, and serves as the closed-loop feedback input for inverse kinematics and dynamic compensation. A rotation angle sensor is provided between the rotating support assembly and the upper plate to measure the actual rotation angle of the upper plate when it moves inward / outward around the Z-axis in real time.

[0013] Furthermore, the lower-level machine A uses an STM32 microcontroller, and the lower-level machine B uses a Mega2560 microcontroller.

[0014] Secondly, based on the rigid-flexible coupled three-dimensional motion device for ankle joint rehabilitation provided in the first aspect, the present invention provides a control method, the control method comprising the following steps:

[0015] The host computer generates the desired motion trajectory based on the rehabilitation mode; it determines the motion dimension to which the target action belongs, including the angular rotation dimension around the X-axis or Y-axis and the yaw rotation dimension around the Z-axis; when the target action belongs to the angular rotation dimension, the lower computer A drives multiple electric push rods to extend and retract to drive the intermediate moving platform and its pneumatic flexible actuators to rotate around the X-axis or Y-axis, and the actual rotation angles of the X-axis and Y-axis are collected in real time by dual-axis tilt sensors; when the target action belongs to the yaw rotation dimension, the lower computer B controls the airway to drive the airbag to inflate to drive the upper plate to rotate around the Z-axis, and the actual yaw angle of the Z-axis is collected in real time by rotation angle sensors; the collected actual angle is compared with the expected angle corresponding to the desired motion trajectory to determine whether the actual posture is within the predetermined error band. If it is not within the predetermined error band, the actuators of the corresponding dimension are driven to adjust until the actual posture is within the predetermined error band.

[0016] Furthermore, the lower-level machine A receives the target lengths of each electric actuator obtained by the upper-level machine or a calculation tool called by the upper-level machine. Before driving the electric actuators, a dynamic mass compensation correction term is first introduced to offset the gravitational bias caused by the change in the mass distribution of the electric actuators during spatial flipping. Subsequently, the lower-level machine A performs digital differential analysis (DDA) interpolation on the target length increments of each electric actuator, decomposing the length increments into a continuous high-frequency pulse output sequence, and outputting pulse signals and direction signals to drive the six electric actuators to extend and retract at a predetermined rhythm. During the movement of the electric actuators, the dual-axis tilt sensor installed on the intermediate moving platform measures the actual flip angles of the X-axis and Y-axis in real time and feeds the measurement results back to the closed-loop judgment link.

[0017] Furthermore, the lower-level machine B receives the instructions from the upper-level machine and parses the target yaw angle. The lower-level machine B controls the relay of the corresponding air path to close, opens the solenoid valve and air pump, and simultaneously outputs a PWM signal to control the output power of the air pump, causing the airbags in the corresponding air path to expand under pressure. By driving the expansion of different airbags, rotation in opposite directions around the Z-axis is achieved. The thrust generated by the expansion of the airbags overcomes the motion resistance of the upper plate, driving the upper plate to rotate smoothly around the central axis. The duty cycle of the PWM signal can be adjusted in real time according to the difference between the target yaw angle and the actual yaw angle to control the expansion speed and thrust of the airbags. During the rotation, the rotation angle sensor measures the actual yaw angle of the Z-axis in real time and feeds the measurement result back to the closed-loop judgment link.

[0018] The beneficial effects achieved by one or more of the above technical solutions are as follows:

[0019] (1) This invention innovatively decomposes the complex three-dimensional movement of the ankle joint and uses the powerful thrust of the six-degree-of-freedom parallel mechanism to complete the plantar flexion / dorsiflexion and inversion / eversion rotation of the knee joint. At the same time, it uses the pneumatic flexible actuator at the top to complete the adduction / abduction movement. It not only fully covers the movements required for rehabilitation, but also avoids the interference and strange positions caused by multi-dimensional movements in a pure rigid mechanism.

[0020] (2) High-precision linkage based on DDA interpolation and dynamic mass compensation collaborative control: The control system uses MATLAB and other host computers to send commands and establishes a connection with the slave computer through a high-speed communication module; the slave computer innovatively combines the DDA (Digital Differential Analysis) interpolation algorithm with the dynamic mass compensation model to construct a collaborative control strategy. While using the DDA algorithm to calculate the multi-axis linkage trajectory and output pulse commands, the system simultaneously introduces a push rod mass correction term of about 0.1 kg to offset the self-gravity bias of the electric push rod during the spatial flipping process in real time. This deep collaboration between kinematic interpolation and dynamic compensation not only effectively eliminates the inherent dynamic force deviation in the multi-degree-of-freedom mechanism, making the motion commands more realistically reflected on the physical mechanism, but also realizes high-precision linkage control of the six electric push rods, ensuring the high fidelity and smoothness of the rehabilitation flipping trajectory without jamming.

[0021] (3) The kinematic settings of the rigid-flexible coupling three-dimensional motion device of the present invention are strictly based on the actual biomechanical limitations of the human body to prevent strain caused by excessive exercise. The rotation is driven by the inflation and expansion of the airbag, and the compressibility of gas naturally provides mechanical compliance at the physical level, which greatly improves the comfort and safety of patients in rehabilitation training. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0023] Figure 1 This is a schematic diagram of the rigid-flexible coupling three-dimensional motion device of the present invention;

[0024] Figure 2 This is a schematic diagram of the six-degree-of-freedom parallel mechanism of the present invention;

[0025] Figure 3 This is a schematic diagram of the SPS branch structure of the present invention;

[0026] Figure 4 This is an exploded view of the pneumatic flexible actuator of the present invention;

[0027] Figure 5 These are schematic diagrams of the pneumatic flexible actuator of the present invention under different rotational states;

[0028] Figure 6 This is a schematic diagram of the six-degree-of-freedom parallel mechanism of the present invention rotating around the X-axis;

[0029] Figure 7 This is a schematic diagram of the six-degree-of-freedom parallel mechanism of the present invention rotating around the Y-axis;

[0030] Figure 8 This is a schematic diagram of the wave-like flipping of the six-degree-of-freedom parallel mechanism of the present invention;

[0031] Figure 9 This is a hardware architecture diagram of the control system of the rigid-flexible coupling three-dimensional motion device of the present invention;

[0032] Figure 10 This is a flowchart of the collaborative control logic of the rigid-flexible coupling three-dimensional motion device of the present invention;

[0033] In the diagram, 1. Six-degree-of-freedom parallel mechanism; 101. Base; 102. Intermediate moving platform; 103. SPS branch; 1031. Lower ball hinge; 1032. L-shaped connector; 1033. Electric push rod; 1034. Sleeve connector; 1035. Upper ball hinge; 2. Pneumatic flexible actuator; 201. Lower plate; 202. Upper plate; 203. Airbag assembly; 2031. Lower baffle; 2032. Upper baffle; 2033. Airbag; 2034. Air hole; 204. Rotary support assembly; 2041. Central shaft; 2042. Bearing; 2043. Snap ring; 2044. Bearing seat. Detailed Implementation

[0034] The present disclosure will be further described below with reference to the accompanying drawings and embodiments.

[0035] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this disclosure. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0036] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0037] Example 1

[0038] like Figure 1-8 As shown, the purpose of this embodiment is to provide a rigid-flexible coupling three-dimensional motion device for ankle joint rehabilitation, including a six-degree-of-freedom parallel mechanism 1, a pneumatic flexible actuator 2, and a control system; the pneumatic flexible actuator 2 is mounted on the moving platform of the six-degree-of-freedom parallel mechanism 1, and the two cooperate to perform ankle joint rehabilitation movements; the ankle joint rehabilitation movements include plantar flexion / dorsiflexion, inversion / eversion, and adduction / abduction movements;

[0039] like Figure 2 and 3 As shown, the six-degree-of-freedom parallel mechanism 1 includes a base 101 (i.e., the static platform of the parallel mechanism) and an intermediate moving platform 102 (i.e., the moving platform of the parallel mechanism). Six SPS branches 103 arranged in a Stewart configuration are provided between the base 101 and the intermediate moving platform 102, specifically in a 2-2-2 layout (e.g., ...). Figure 1 As shown), the 6 hinge points of the intermediate moving platform are divided into 3 pairs, with 2 hinge points in each pair installed close to each other. The three pairs are evenly distributed at 120° on the circumference. The base also has 3 pairs of hinge points, with 2 hinge points in each pair arranged close to each other. The three pairs of hinge points are rotated and staggered with the three pairs of hinge points of the intermediate moving platform to make the branches intersect. S represents ball joint (ball hinge), P represents sliding joint, and P joint is the driving joint.

[0040] like Figure 4 As shown, the pneumatic flexible actuator 2 includes a lower plate 201 fixedly mounted on the intermediate moving platform 102. The lower plate 201 is installed directly above the intermediate moving platform 102 via threaded connections (bolts, mounting holes, etc.). An upper plate 202 is rotatably mounted on the lower plate 201. Two airbag assemblies 203 are symmetrically arranged between the lower plate 201 and the upper plate 202. The upper plate 202 is driven to rotate smoothly by inflating and deflating the airbags 2033 in the airbag assemblies 203. One airbag assembly 203 is used to achieve clockwise rotation, and the other airbag assembly 203 is used to achieve counterclockwise rotation. The control system is used to send commands and drive the six-degree-of-freedom parallel mechanism 1 and the pneumatic flexible actuator 2 to move according to a preset trajectory. The six-degree-of-freedom parallel mechanism 1 is used to perform plantar flexion or dorsiflexion and inversion or eversion movements of the ankle joint, and the pneumatic flexible actuator 2 is used to perform adduction or abduction movements of the ankle joint. This invention innovatively deconstructs the complex three-dimensional movements of the ankle joint, utilizing the powerful thrust of a six-degree-of-freedom parallel mechanism 1 to complete plantar flexion / dorsiflexion and inversion / eversion rotation, while simultaneously employing a top-mounted pneumatic flexible actuator 2 to complete adduction / abduction movements. This not only comprehensively covers the movements required for rehabilitation but also avoids interference and unusual positions that arise from multi-dimensional movements in purely rigid mechanisms. Furthermore, the invention utilizes the inflation and expansion of an air bladder to drive rotation, leveraging the compressibility of gas to naturally provide physical mechanical compliance, greatly enhancing patient comfort and safety during rehabilitation training.

[0041] As a further implementation, the SPS branch 103 includes a lower ball joint 1031, an L-shaped connector 1302, an electric actuator 1033, a sleeve connector 1034, and an upper ball joint 1035. The lower ball joint 1031 is located at the upper end of the base 101, and the upper ball joint 1035 is located at the lower end of the intermediate moving platform 102. The lower end of the electric actuator 1033 is connected to the lower ball joint 1031 through the L-shaped connector 1032, and the upper end is connected to the upper ball joint 1035 through the sleeve connector 1034. A specific implementation of the SPS branch 103 is given. Since the application field of this application is ankle joint rehabilitation exercise, there is no situation with extremely large loads. Therefore, this invention introduces the electric actuator 1033 as a P-pair, which not only has the kinematic intuitiveness of motion drive, but also can fully utilize the advantages of high precision, high cleanliness, and high integration of electric servo drive.

[0042] As a further implementation, the airbag assembly 203 includes a lower baffle 2031 disposed on the upper end of the lower plate 201 and an upper baffle 2032 disposed on the lower end of the upper plate 202. An arc-shaped airbag 2033 is provided between the lower baffle 2031 and the upper baffle 2032. Specifically, the ends of the airbag 2033 are fixedly connected to the respective lower baffle 2031 and upper baffle 2032 by adhesive. The lower baffle 2031 is provided with an air hole 2034 communicating with the interior of the airbag 2033. The air hole 2034 is connected to a solenoid valve and a brushless diaphragm air pump through an air passage.

[0043] Specifically, taking the rehabilitation of the right foot as an example, when the pneumatic flexible actuator 2 performs an abduction movement: the program controls the relay corresponding to the left air path to close, at which time the corresponding solenoid valve is energized and opened, and the brushless diaphragm air pump delivers gas through the left air hole 2034 into the left air bladder 2033. The left air bladder 2033 is continuously inflated and deforms and expands. The inflated left air bladder 2033 pushes against the left upper baffle 2032, thereby pushing the upper plate 202 to rotate clockwise, causing the human foot to perform an abduction movement to reach the predetermined angle; after inflation is completed, the corresponding relay is disconnected, the connected solenoid valve is de-energized, the inflation air path is interrupted, and the brushless diaphragm air pump stops delivering airflow; because the internal air pressure of the left air bladder 2033 is greater than the external atmospheric pressure, and is affected by the rebound of the right air bladder 2033 and the human foot Due to the natural pressure of the body, the gas in the airbag 2033 can be discharged into the atmosphere through the exhaust end of the solenoid valve, thus restoring the upper plate 202 to its initial state. Subsequently, during the adduction movement: the program controls the relay corresponding to the right-side air path to close, at which point another solenoid valve is energized and opened. Gas enters the right-side airbag 2033 through the right-side air hole 2034. The right-side airbag 2033 continuously inflates and deforms, pushing against the right-side upper baffle 2032, causing the upper plate 202 to rotate counterclockwise, leading to an adduction movement of the human foot to a predetermined angle. After inflation is complete, the corresponding relay disconnects, the air path is interrupted, and the gas inside the right-side airbag 2033 is discharged into the atmosphere under atmospheric pressure difference and physical compression. The system then repeats the inflation and deflation steps sequentially according to the set movement frequency. Because the gas in the airbag 2033 is compressible during inflation and deflation, it provides natural damping cushioning for the patient's ankle during the pushing process, achieving smooth and safe human-machine interaction. (See reference...) Figure 5 As shown in the figure, from top to bottom, the states are: 30° left rotation, initial state, and 30° right rotation.

[0044] As a further implementation, the upper plate 202 is connected to the lower plate 201 via a rotary support assembly 204. The rotary support assembly 204 includes a central shaft 2041 disposed at the center of the lower plate 201, and a bearing 2042 and a retaining ring 2043 are provided on the central shaft 2041. A bearing seat 2044 for mounting the bearing 2042 is provided at the center of the lower end of the upper plate 202. This enables the upper plate 202 to be rotatably connected relative to the lower plate 201.

[0045] As a further implementation method, such as Figure 9As shown, the control system adopts a dual-master distributed architecture, including a host computer (PC), slave computer A (STM32 microcontroller), slave computer B (Mega2560 microcontroller), a 24V power supply, a motor driver, a brushless diaphragm air pump, two solenoid valves, a relay module, and an attitude detection module. The host computer is connected to slave computer A (also called slave computer one) and slave computer B (also called slave computer two). Each electric push rod 1033 is equipped with a motor driver, which is connected to slave computer A. The slave computer A controls the extension and retraction of the six electric push rods 1033 through pulse signals and direction signals. The airbag 2033 is connected to the solenoid valve and the miniature brushless diaphragm through an air passage. The lower-level machine B is connected to a micro brushless diaphragm air pump and a multi-channel relay module, which is connected to a solenoid valve. The attitude detection module includes a dual-axis tilt sensor connected to the lower-level machine A and a rotation angle sensor connected to the lower-level machine B. The dual-axis tilt sensor is located at the center of the lower end of the intermediate moving platform 102 and is used to detect the actual rotation angle of the intermediate moving platform 102 around the X and Y axes in three-dimensional space in real time, serving as the closed-loop feedback input for inverse kinematics and dynamic compensation. A rotation angle sensor is provided between the rotating support assembly 204 and the upper plate 202 to measure the actual rotation angle of the upper plate 202 when it performs inward / outward movements around the Z axis in real time. This application collects the actual angles in two dimensions using the dual-axis tilt sensor and the rotation angle sensor respectively, and integrates them into a predetermined error band to form a closed loop, which is beneficial for achieving coordinated control of the two dimensions and improving the posture control accuracy during multi-dimensional motion.

[0046] Specifically, the connection method is as follows: the 24V DC output of the switching power supply directly powers the motor driver connected to the six-degree-of-freedom parallel mechanism 1; by connecting the corresponding switching power supply, the output 24V and 12V DC power supplies the brushless diaphragm air pump, the two solenoid valves, the STM32 microcontroller, and the Mega2560 microcontroller, respectively; the signal output pins of the STM32 microcontroller are connected to the pulse and direction pins of each motor driver; the digital pins of the Mega2560 microcontroller are connected to the relay module, and the relay module controls the on / off state of the two solenoid valves and the air pump. The STM32 microcontroller contains low-level logic code that combines the DDA interpolation algorithm with a dynamic mass compensation model. When performing rigid angle flipping, the STM32 microcontroller uses inverse kinematics and introduces a mass correction term of about 0.1 kg. Then, it accurately distributes pulses through the DDA interpolation algorithm to precisely control the six-degree-of-freedom parallel mechanism 1 to complete the flipping motion from -20° to 20°. Specifically, when performing ankle plantar flexion / dorsiflexion and inversion / eversion movements: the host computer of the control system sends the theoretical motion trajectory command to the STM32 microcontroller through serial communication. The STM32 microcontroller uses the DDA interpolation algorithm to generate control signals and sends them to each motor driver. At the same time, it controls the extension and retraction of the six electric push rods 1033, which drives the intermediate moving platform 102 to produce multi-axis linkage spatial flipping, thereby guiding the human foot (the human foot is placed on the upper plate 202) to complete the corresponding rehabilitation movement.

[0047] Meanwhile, the Mega2560 microcontroller independently processes the flexible yaw command, achieving decoupled and coordinated control across all dimensions through PWM control of the pneumatic circuit. The pneumatic flexible actuator 2 of this invention not only achieves precise left and right rotational deformation (maximum rotation angle can be set to ±30°), but also possesses reliable power output capability. In this embodiment, the driving air source for the pneumatic system is a miniature vacuum pump, such as the Kamoe HLVP6-NB12 model. This pump, in conjunction with the Mega2560 microcontroller's PWM speed control signal (voltage range 0V-12V, control signal frequency 10KHz-30KHz, adjustable duty cycle 10%-100%), can precisely adjust the output airflow and operating time. The pump's airflow rate can reach 6L / min, and the maximum output pressure is approximately 80kPa, which fully meets the deformation requirements of the soft airbag drive. In this device, the rotational torque generated by the inflation of the airbag 2033 is mainly determined by the output pressure of the air pump, the effective working area of ​​the airbag, and the vertical distance (lever arm) from the force center of the airbag 2033 to the rotational support assembly 204. Its theoretical output rotational torque formula is:

[0048]

[0049] In the formula, For rotational torque, This refers to the internal pressure of the airbag. This refers to the effective contact area between the airbag and the baffle when the airbag inflates. It is the straight-line distance from the center of force of the airbag to the center of rotation.

[0050] Taking a practical rehabilitation application scenario as an example: The maximum output pressure of the air pump is set to 80 kPa (i.e., 80,000 kPa). The effective contact surface diameter between the airbag and the baffle on one side is 35 mm. The effective working area is approximately 0.00096 square meters; and the lever arm length from the center of force of the airbag to the center of the rotating shaft is 0.09 meters. When the corresponding solenoid valve is opened for inflation, the thrust generated by a single airbag is approximately 77. This translates to a theoretical maximum torque of approximately 6.9 Nm, which drives the upper plate 202 to rotate. .

[0051] In clinical ankle rehabilitation training, the physiological resistance of a normal human ankle joint during passive adduction / abduction movements is typically around 3. Up to 5 Between. This embodiment is approximately 6.9. The theoretical rotational torque can not only fully overcome the passive physiological resistance of the human ankle joint, but also effectively drive a physical load of 3kg to 5kg (covering the weight of most adult feet and the total weight of the fixed accessories worn), ensuring sufficient power redundancy and rehabilitation effectiveness while ensuring the smoothness of human-machine interaction.

[0052] Example 2

[0053] like Figure 10 As shown, in another typical embodiment of the present invention, a control method for a rigid-flexible coupled three-dimensional motion device is provided, the control method comprising the following steps:

[0054] The host computer generates the desired movement trajectory based on the rehabilitation mode; it determines the movement dimension to which the target movement belongs, including the angular rotation dimension around the X-axis or Y-axis (including plantar flexion / dorsiflexion and inversion / exversion) and the yaw rotation dimension around the Z-axis (including adduction / abduction); when the target movement belongs to the angular rotation dimension, the lower computer A drives multiple electric push rods 1033 to extend and retract to drive the intermediate moving platform 102 and its pneumatic flexible actuator 2 to rotate around the X-axis or Y-axis, and the actual rotation angle of the X-axis and Y-axis is collected in real time by the dual-axis tilt sensor; when the target movement belongs to the yaw rotation dimension, the lower computer B controls the airway to drive the airbag to inflate to drive the upper plate 202 to rotate around the Z-axis, and the actual yaw angle of the Z-axis is collected in real time by the rotation angle sensor; based on the comparison between the collected actual angle and the expected angle corresponding to the desired movement trajectory, it is determined whether the actual posture is within the predetermined error band. If it is not within the predetermined error band, the actuator of the corresponding dimension continues to be driven to adjust until the actual posture is within the predetermined error band. During the execution of the movement, the dual-axis tilt sensor and rotation angle sensor measure the flip angle of the bottom mechanism (six-DOF parallel mechanism 1) and the yaw angle of the top mechanism (pneumatic flexible actuator 2) in real time, respectively, and feed the data back to the lower-level computer. The system compares the actual posture with the expected posture. If the actual posture is within the expected error band, the task is considered complete, and the motor and solenoid valve stop working. If the error exceeds the threshold, the system automatically performs independent closed-loop adjustments in the STM32 microcontroller and Mega2560 microcontroller respectively until all postures meet the standards. This method distributes control commands to two independent lower-level control units according to the movement dimension. The X / Y axis flipping is driven by the electric actuator 1033, and the Z-axis rotation is driven by the airbag 2033. This not only covers the multi-dimensional movement needs of the ankle joint on the same rehabilitation platform, but also realizes independent drive and collaborative closed-loop control of the two dimensions on the same platform, improving the posture control accuracy of ankle joint rehabilitation training. In particular, the compliance of the airbag 2033 drive can significantly improve the comfort of Z-axis rotation training.

[0055] As a further implementation, the lower-level computer A receives the target lengths of each electric actuator 1033 obtained by the upper-level computer or a calculation tool called by the upper-level computer. Before driving the electric actuators 1033, a dynamic mass compensation correction term is first introduced to offset the gravitational bias caused by the change in the mass distribution of the electric actuators 1033 during spatial rotation. Subsequently, the lower-level computer A performs digital differential analysis (DDA) interpolation on the target length increments of each electric actuator 1033, decomposing the length increments into a continuous high-frequency pulse output sequence, and outputting pulse signals and direction signals to drive the six electric actuators 1033 to extend and retract at a predetermined rhythm. During the movement of the electric actuators 1033, a dual-axis tilt sensor installed on the intermediate moving platform 102 measures the actual rotation angles of the X and Y axes in real time and feeds the measurement results back to the closed-loop judgment stage. This application introduces a dynamic mass compensation correction term in the driving stage of the electric actuators 1033, which can offset the gravitational bias of the rehabilitation platform and load in the tilted state, and helps to reduce the influence of gravity on the positioning accuracy of the electric actuators 1033.

[0056] As a further implementation, the lower-level machine B receives the instructions issued by the upper-level machine and parses the target yaw angle. The lower-level machine B controls the relay of the corresponding air path to close, opens the solenoid valve and air pump, and simultaneously outputs a PWM signal to control the output power of the air pump, causing the airbag 2033 of the corresponding air path to expand under pressure. By driving the expansion of different airbags 2033, rotation in opposite directions around the Z-axis is achieved. The thrust generated by the expansion of the airbag 2033 overcomes the motion resistance of the upper plate 202, driving the upper plate 202 to achieve smooth rotation around the central axis 2041. The duty cycle of the PWM signal can be adjusted in real time according to the difference between the target yaw angle and the actual yaw angle to control the expansion speed and thrust of the airbag 2033. During the rotation, the rotation angle sensor measures the actual yaw angle of the Z-axis in real time and feeds the measurement result back to the closed-loop judgment link. In this application, the air pump output power is controlled by a PWM signal in the airbag 2033 drive stage, and the duty cycle is adjusted in real time according to the angle deviation. This allows for the adjustment of the airbag's expansion speed and thrust, which is beneficial to improving the controllability of the Z-axis yaw rotation.

[0057] The above specific embodiments should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, any alternative improvements or modifications made to the embodiments of the present invention shall fall within the scope of protection of the present invention.

[0058] Any aspects of this invention not described in detail are well-known to those skilled in the art.

Claims

1. A rigid-flexible coupled three-dimensional motion device for ankle joint rehabilitation, characterized in that, The system includes a six-degree-of-freedom parallel mechanism, a pneumatic flexible actuator, and a control system. The six-degree-of-freedom parallel mechanism includes a base and an intermediate moving platform. Six SPS branches in a Stewart configuration are provided between the base and the intermediate moving platform, where the P-joint is a driving joint. The pneumatic flexible actuator includes a lower plate fixedly mounted on the intermediate moving platform. An upper plate is rotatably mounted on the lower plate. Two airbag assemblies are symmetrically arranged between the lower and upper plates. The upper plate is driven to rotate smoothly by inflating and deflating the airbags in the airbag assemblies. The control system drives the six-degree-of-freedom parallel mechanism and the pneumatic flexible actuator. The six-degree-of-freedom parallel mechanism is used to perform plantar flexion or dorsiflexion and inversion or eversion movements of the ankle joint. The pneumatic flexible actuator is used to perform adduction or abduction movements of the ankle joint.

2. The rigid-flexible coupling three-dimensional motion device for ankle joint rehabilitation according to claim 1, characterized in that, The SPS branch chain includes a lower ball joint, an L-shaped connector, an electric push rod, a sleeve connector, and an upper ball joint. The lower ball joint is located at the upper end of the base, and the upper ball joint is located at the lower end of the intermediate moving platform. The lower end of the electric push rod is connected to the lower ball joint through the L-shaped connector, and the upper end is connected to the upper ball joint through the sleeve connector.

3. The rigid-flexible coupling three-dimensional motion device for ankle joint rehabilitation according to claim 1 or 2, characterized in that, The airbag assembly includes a lower baffle plate disposed at the upper end of the lower plate and an upper baffle plate disposed at the lower end of the upper plate. An arc-shaped airbag is provided between the lower baffle plate and the upper baffle plate. An air hole communicating with the interior of the airbag is provided on the lower baffle plate.

4. The rigid-flexible coupling three-dimensional motion device for ankle joint rehabilitation according to claim 3, characterized in that, The upper plate is connected to the lower plate via a rotary support assembly. The rotary support assembly includes a central shaft located at the center of the lower plate, on which a bearing and a retaining ring are mounted. The lower end of the upper plate is provided with a bearing seat for mounting the bearing.

5. The rigid-flexible coupling three-dimensional motion device for ankle joint rehabilitation according to claim 4, characterized in that, The control system includes a host computer and an attitude detection module. The host computer is connected to slave computers A and B. Each electric push rod is equipped with a motor driver, which is connected to slave computer A. Slave computer A controls the extension and retraction of the six electric push rods through pulse signals and direction signals. The airbag is connected to a solenoid valve and a miniature brushless diaphragm air pump in sequence through an air path. Slave computer B is connected to the miniature brushless diaphragm air pump and a multi-channel relay module, which is connected to the solenoid valve. The attitude detection module includes a dual-axis tilt sensor connected to slave computer A and a rotation angle sensor connected to slave computer B. The dual-axis tilt sensor is located at the center of the lower end of the intermediate moving platform and is used to detect the actual rotation angle of the intermediate moving platform around the X and Y axes in three-dimensional space in real time, and serves as the closed-loop feedback input for inverse kinematics and dynamic compensation. A rotation angle sensor is provided between the rotating support assembly and the upper plate to measure the actual rotation angle of the upper plate when it moves inward / outward around the Z axis in real time.

6. The rigid-flexible coupling three-dimensional motion device for ankle joint rehabilitation according to claim 5, characterized in that, The lower-level machine A uses an STM32 microcontroller, and the lower-level machine B uses a Mega2560 microcontroller.

7. A control method for a rigid-flexible coupled three-dimensional motion device, characterized in that, Including the rigid-flexible coupled three-dimensional motion device for ankle joint rehabilitation as described in any one of claims 5-6, the control method includes the following steps: The host computer generates the desired motion trajectory based on the rehabilitation mode; it determines the motion dimension to which the target action belongs, including the angular rotation dimension around the X-axis or Y-axis and the yaw rotation dimension around the Z-axis; when the target action belongs to the angular rotation dimension, the lower computer A drives multiple electric push rods to extend and retract to drive the intermediate moving platform and its pneumatic flexible actuators to rotate around the X-axis or Y-axis, and the actual rotation angles of the X-axis and Y-axis are collected in real time by dual-axis tilt sensors; when the target action belongs to the yaw rotation dimension, the lower computer B controls the airway to drive the airbag to inflate to drive the upper plate to rotate around the Z-axis, and the actual yaw angle of the Z-axis is collected in real time by rotation angle sensors; the collected actual angle is compared with the expected angle corresponding to the desired motion trajectory to determine whether the actual posture is within the predetermined error band. If it is not within the predetermined error band, the actuators of the corresponding dimension are driven to adjust until the actual posture is within the predetermined error band.

8. The control method for the rigid-flexible coupled three-dimensional motion device according to claim 7, characterized in that, The lower-level computer A receives the target lengths of each electric actuator obtained by the upper-level computer or a calculation tool called by the upper-level computer. Before driving the electric actuators, a dynamic mass compensation correction term is first introduced to offset the gravitational bias caused by the change in the mass distribution of the electric actuators during spatial flipping. Then, the lower-level computer A performs digital differential analysis (DDA) interpolation on the target length increment of each electric actuator, decomposes the length increment into a continuous high-frequency pulse output sequence, and outputs pulse signals and direction signals to drive the six electric actuators to extend and retract at a predetermined rhythm. During the movement of the electric actuators, the dual-axis tilt sensor installed on the intermediate moving platform measures the actual flip angles of the X-axis and Y-axis in real time and feeds the measurement results back to the closed-loop judgment link.

9. The control method for the rigid-flexible coupled three-dimensional motion device according to claim 7 or 8, characterized in that, The lower-level machine B receives the command issued by the upper-level machine and parses the target yaw angle. The lower-level machine B controls the relay of the corresponding air path to close, opens the solenoid valve and air pump, and outputs a PWM signal to control the output power of the air pump, so that the airbags in the corresponding air path are inflated under pressure. By driving the inflation of different airbags, rotation in opposite directions around the Z-axis is achieved. The thrust generated by the inflation of the airbags overcomes the motion resistance of the upper plate, driving the upper plate to rotate smoothly around the central axis. The duty cycle of the PWM signal can be adjusted in real time according to the difference between the target yaw angle and the actual yaw angle to control the inflation speed and thrust of the airbags. During the rotation, the rotation angle sensor measures the actual yaw angle of the Z-axis in real time and feeds the measurement result back to the closed-loop judgment link.

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