Control method and system of knee joint power-assisted exoskeleton

Abstract

The invention discloses a control method and system of a knee joint power-assisted exoskeleton, and belongs to the technical field of exoskeletons. The control method comprises an uphill mode and a downhill mode. In the uphill mode, thigh angular velocity, joint angle and joint angular velocity data are detected in real time, whether the current single-leg gait is converted into a supporting phase from a swinging phase or not is judged according to the detected data, and a control end angle and a control torque coefficient on a conversion node are recorded; calculating a motor output torque based on the current joint angle and the minimum value of the output torque; in the downhill mode, joint angle and joint angular velocity data are detected in real time, whether the knee joint of the current single leg is bent in an accelerated mode or not is judged according to the detected data, and if yes, the motor output torque is determined according to the joint angular velocity and a preset damping coefficient. Self-adaptive assistance can be achieved only through thigh angular velocity and joint angle data, assistance output is smooth, response is timely, and the self-adaptive assistance device can adapt to gait characteristics and uphill and downhill working condition changes of different wearers.

Description

Technical Field

[0001] This invention relates to the field of exoskeleton technology, specifically to a control method and system for a knee-joint assisted exoskeleton. Background Technology

[0002] With the increasing aging population and growing demand for sports injury rehabilitation, knee assist devices have been widely used in medical rehabilitation and daily life assistance. Existing knee assist technologies are typically designed for single working conditions, while daily activities involve various movement states such as walking on flat ground, going uphill, and going downhill. Current knee assist technologies are poorly adapted to these situations, as wearers have drastically different torque requirements on their knee joints under different conditions. When going uphill, they need to overcome gravity to lift their bodies, and when going downhill, they need to control their descent speed to maintain stability. Traditional control methods either rely on complex multi-dimensional force sensors, which are costly, or use only fixed PID parameters, failing to adapt to different gait habits and body characteristics of wearers, easily resulting in jerky assistance or insufficient assistance. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a control method and system for a knee joint-assisted exoskeleton.

[0004] The technical solution adopted in this invention is as follows: A method for controlling a knee-assisted exoskeleton, including an uphill mode and a downhill mode; In the uphill mode, the thigh angular velocity, joint angle, and joint angular velocity data are detected in real time. Based on the detected data, it is determined whether the current single-leg gait has changed from the swing phase to the support phase. The control end angle and control torque coefficient at the transition node are recorded. During the support phase, the motor output torque is calculated based on the current joint angle and the minimum output torque. In the downhill mode, joint angle and joint angular velocity data are detected in real time, and it is determined whether the knee joint of the current single leg is accelerating its bending based on the detected data. If so, the motor output torque is determined based on the joint angular velocity and the preset damping coefficient.

[0005] This solution distinguishes between uphill and downhill modes for separate control, eliminating the need for complex multi-dimensional force sensors. It achieves adaptive assistance solely through an inertial measurement unit and an angle sensor, and can adjust the output torque in real time according to changes in the wearer's gait characteristics. This solves the problems of poor adaptability, jerky assistance, or insufficient assistance in existing technologies under different working conditions.

[0006] Preferably, the uphill mode includes three consecutive control states; in the first state, the thigh angular velocity is monitored, and when the thigh angular velocity exceeds a preset first threshold, the system switches to the second state; in the second state, the joint angle is monitored. When the joint angle exceeds a preset second threshold and the joint angular velocity exceeds a preset third threshold, the control termination angle at the current moment is recorded. and control torque coefficient Then switch to the third state; in the third state, monitor the joint angle. When the joint angle Greater than the control end angle Motor output torque The preset minimum output torque is determined when the joint angle... Not greater than the control end angle Motor output torque The state switching logic is designed based on the natural gait characteristics of the human body when going uphill. This ensures that the assist outputs a constant basic assist only in the early stage of the support phase, and decreases linearly with joint extension in the middle and late stages of the support phase. This achieves synchronization between the assist and the rhythm of human movement, avoiding the feeling of assistance abruptness.

[0007] Preferably, the control end angle Where k is a preset proportionality coefficient, This refers to the joint angle at the moment of switching to the third state. The control end angle is calculated based on the actual joint angle at the moment of switching, so that the end point of the assist can adapt to the wearer's current gait amplitude. The proportional coefficient k can be pre-adjusted to adapt to different body characteristics and gait habits, thus improving the personalization of control.

[0008] Preferably, the control torque coefficient ,in To achieve the minimum output torque, To control the final angle, this coefficient establishes a linear relationship between the joint angle and the output torque, enabling a smooth transition of assistance in the later stages of the support phase, ensuring the continuity of assistance changes, and improving wearing comfort.

[0009] Preferably, in the downhill mode, when a joint angle greater than zero and a joint angular velocity greater than zero are detected, it is determined that the knee joint is accelerating its bending. This determination condition can accurately identify the critical stage where damping is required during downhill driving.

[0010] Preferably, in the downhill mode, the formula for calculating the motor output torque based on the joint angular velocity and the preset damping coefficient is as follows: ,in The preset damping coefficient, The damping coefficient is the joint angular velocity. This design provides a damping force proportional to the bending speed through the linear relationship between the damping coefficient and the angular velocity, which can effectively control the knee joint's descent speed when going downhill and enhance the wearer's sense of stability.

[0011] Preferably, if the motor output torque Less than the minimum output torque Then the motor outputs the target torque Limited to the minimum output torque This ensures that the motor can provide basic assistance under any circumstances, avoiding a lack of assistance output due to insufficient calculated torque, and guaranteeing basic safety when going downhill.

[0012] Preferably, the motor output torque calculated in the uphill or downhill mode is output after smoothing and limiting. Smoothing eliminates abrupt changes in torque command, making the assist output smoother and more natural; limiting restricts the output torque within a safe range, preventing injury to the wearer due to excessive torque caused by system malfunctions, thus improving the system's safety and comfort.

[0013] Preferably, the uphill mode and downhill mode are switched manually or automatically based on sensor data, and the combination of the two methods meets the usage needs in different scenarios.

[0014] The present invention also discloses a knee joint assistive exoskeleton control system for implementing the above control method.

[0015] Compared to existing technologies, this invention reduces the number of sensors and lowers system costs by controlling uphill and downhill modes separately. The uphill mode employs a three-stage state switching, providing assistance linearly related to the joint angle only in the support phase, resulting in smooth assistance output that adapts to gait changes. The downhill mode uses damping coefficient control to provide damping force proportional to the bending speed, effectively maintaining walking stability. The entire control method has clear logic and adjustable parameters, adapting to the gait characteristics of different wearers, achieving intelligent and personalized knee joint assistance control, and improving the wearer's experience and exercise safety. Attached Figure Description

[0016] Figure 1 This is a flowchart of the uphill mode control logic of the present invention; Figure 2 This is a flowchart of the downhill mode control logic of the present invention. Detailed Implementation

[0017] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0018] This invention relates to a control method and system for a knee-assisted exoskeleton, which can control the knee-assisted exoskeleton to provide adaptive assistance according to the different gait characteristics of the human body when going uphill or downhill.

[0019] First, the hardware environment upon which the method of this invention is based will be described. This knee-assisted exoskeleton is worn on the user's lower limbs. It primarily provides auxiliary torque for leg swinging via a motor located at the knee joint, thereby conserving energy, enhancing motor function, or assisting in rehabilitation training. Each leg of the exoskeleton includes a thigh link, a lower leg link, and a knee joint drive module connecting the two. The knee joint drive module includes a motor for driving the relative rotation of the thigh and lower leg links, an angle sensor for detecting the joint angle, etc. The thigh link is equipped with an inertial measurement unit (IMU) to sense changes in the angular velocity of the thigh during swinging. The knee joint angle is defined as the mechanical zero point when the wearer is in a standard standing posture, i.e., when the leg is fully extended, denoted as . When the knee joint flexes, that is, when the lower leg swings backward relative to the thigh, the knee joint angle value increases positively from zero.

[0020] The core of this invention lies in the design of two control logics for uphill and downhill movement modes. The movement mode can be switched manually by the wearer, or automatically identified and switched to the corresponding mode based on sensor data by a built-in gait recognition algorithm. The control logic for each mode is described in detail below.

[0021] (a) Control logic of uphill mode like Figure 1 As shown, in uphill mode, the system uses a state machine algorithm, which includes the following three main states.

[0022] First state: This is the initial state of the system in uphill mode. In this state, the system continuously monitors the thigh angular velocity data output by the inertial measurement unit, and this angular velocity is denoted as... When the angular velocity of the wearer's thigh swinging forward and upward exceeds a preset first threshold... At that time, that is The system determines that the single-leg gait on that side has entered the early swing phase, and then switches from the initial first state to the second state.

[0023] Second state: After entering the second state, the system reads the joint angle value output by the angle sensor in real time. The joint angular velocity value is then calculated by differentiating from this angle value. The system determines the current joint angle value. Does it exceed the preset second threshold? and the current joint angular velocity value Does it exceed the preset third threshold? .when and When both conditions are met, it is determined that the gait of that single leg has transitioned into the support phase, and the third state is triggered. At this moment, the control termination angle is calculated and recorded. and control torque coefficient Two parameters. One controls the ending angle. The formula used to define different stages of assist output is as follows: ,in , This is the proportionality coefficient. It can be pre-adjusted according to the wearer's body shape and natural gait habits. Control torque coefficient. The formula used to establish a linear proportional relationship between output torque and joint angle during stages where the joint angle is less than or equal to the control end angle is as follows: ,in This is the preset minimum output torque value, which refers to the minimum torque value at which the wearer can perceive the assistance.

[0024] Third state: In this state, the system continuously compares the current real-time joint angle value with the previously recorded control end angle. If the current joint angle value Greater than the control end angle If the gait of that single leg is still in the early support phase requiring assistance, the motor outputs a constant torque value, i.e., the minimum output torque value. If the current joint angle value Not greater than the control end angle If this is the case, it is determined that the single-leg gait on that side has entered the mid-to-late support phase or the swing phase, at which point the motor output torque value... This causes the assist effect to decrease linearly as the knee extension angle decreases.

[0025] (ii) Control logic of downhill mode like Figure 2 As shown, in downhill mode, the system collects the joint angle values ​​output by the angle sensor in real time. And calculate the joint angular velocity value When the joint angle value is detected And the joint angular velocity value When the knee joint is bent and is bending further, the system determines that the wearer's leg on that side is in the middle or late support phase of a downhill descent, requiring damping force to control the descent speed. At this time, the motor outputs the target torque. ,in This is a preset torque damping coefficient, which can be adjusted by the wearer according to their desired control of the descent speed. The calculated target output torque of the motor is then compared with the minimum output torque. Compare, if Then the motor outputs the target torque Limited to the minimum output torque This ensures that basic assistance is provided under any circumstances, avoiding situations where there is no assistance output due to insufficient torque.

[0026] To ensure wearer comfort and system stability, the motor output torque value obtained after the above uphill or downhill mode control logic processing is... It also needs to undergo torque output smoothing and limiting processing. After the control logic enters the uphill or downhill mode, the torque output is smoothed and limited, and the final motor output torque is executed by the motor, which is regarded as one control cycle. The control cycle is executed cyclically.

[0027] Smoothing typically involves processing the torque command sequence using a preset smoothing algorithm to eliminate the motor's output torque value. The sudden changes and steps make the output smoother. The smoothing algorithm in this embodiment is as follows: Preset cycle increase torque maximum value and the periodic decrease in maximum torque ; Calculate the rate of change of output torque ,in This represents the final motor output torque in the previous cycle. To control the cycle duration; compare the rate of change of output torque. With the preset maximum value of the periodic increase torque and the periodic decrease in maximum torque ,like This indicates that the torque is increasing too rapidly, so the motor output torque value is calculated and updated according to the maximum allowable growth rate. ,like This indicates that the torque is decreasing too quickly, so the motor output torque value is calculated and updated based on the maximum permissible deceleration. .

[0028] The smoothed motor output torque value still needs to be limited within the system's preset safe torque range. The limiting process, based on the motor's mechanical properties and system safety requirements, limits the motor output torque value... The torque is limited to a preset range to prevent injury to the wearer due to excessive output torque caused by system malfunctions. The final motor output torque is obtained after smoothing and limiting. The signals are sent to the motor driver of the knee-assist exoskeleton, where the motor executes the output. The entire control method operates continuously, thus completing the closed-loop control of the knee-assist exoskeleton and providing intelligent knee assistance to the wearer. Example 2

[0029] This application also provides a knee joint assist control system for implementing the control method in Embodiment 1 above. The system mainly includes: The signal acquisition module is used to collect inertial measurement unit (IMU) data from the wearer's thigh, current knee angle data, and joint angular velocity data. This module includes at least one IMU sensor and one angle sensor.

[0030] The mode switching module is used to select or identify the current motion mode. It can be a manual switch or an automatic identification unit based on sensor data.

[0031] The control calculation module, as the core processing unit of the system, receives data from the signal acquisition module and the mode switching module. This module has pre-set algorithm logic for uphill and downhill modes. In uphill mode, it executes state machine judgments, parameter calculations and recording, and finally outputs the torque value; in downhill mode, it calculates the damping torque value based on threshold conditions for joint angles and angular velocities.

[0032] The torque output module receives the raw torque command output by the control calculation module, performs smoothing filtering and amplitude limiting processing on it, and generates a corresponding drive signal to drive the knee joint assist motor to output the final assist torque.

[0033] As a further optimization of the above solution, the mode switching module can be a human-computer interaction button or a gait recognition algorithm integrated into the controller. This algorithm analyzes the data characteristics of the inertial measurement unit and angle sensor to automatically identify whether the wearer is currently going uphill or downhill and automatically switches to the corresponding control mode. Furthermore, the proportional coefficient k and the minimum output torque... Damping coefficient All adjustable parameters are stored in the system's internal memory and can be personalized by the wearer or professionals.

[0034] The aforementioned system structure enables the reliable execution of the control methods described above, providing wearers with a personalized assistance experience that adapts to different road conditions.

[0035] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any brief modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for controlling a knee-joint-assisted exoskeleton, characterized in that, Includes uphill and downhill modes; In the uphill mode, the thigh angular velocity, joint angle, and joint angular velocity data are detected in real time. Based on the detected data, it is determined whether the current single-leg gait has changed from the swing phase to the support phase. The control end angle and control torque coefficient at the transition node are recorded. During the support phase, the motor output torque is calculated based on the current joint angle and the minimum output torque. In the downhill mode, joint angle and joint angular velocity data are detected in real time, and it is determined whether the knee joint of the current single leg is accelerating its bending based on the detected data. If so, the motor output torque is determined based on the joint angular velocity and the preset damping coefficient.

2. The control method for the knee joint-assisted exoskeleton according to claim 1, characterized in that, The uphill mode includes three consecutive control states; In the first state, the thigh angular velocity is monitored, and when the thigh angular velocity exceeds a preset first threshold, the system switches to the second state. In the second state, monitor joint angles. When the joint angle exceeds a preset second threshold and the joint angular velocity exceeds a preset third threshold, the control termination angle at the current moment is recorded. and control torque coefficient And switch to the third state; In the third state, joint angles are monitored. When the joint angle Greater than the control end angle Motor output torque The preset minimum output torque is determined when the joint angle... Not greater than the control end angle Motor output torque .

3. The control method for the knee joint-assisted exoskeleton according to claim 2, characterized in that, The control end angle Where k is a preset proportionality coefficient, The joint angle at the moment of switching to the third state.

4. The control method for the knee joint-assisted exoskeleton according to claim 2, characterized in that, The control torque coefficient ,in To achieve the minimum output torque, To control the ending angle.

5. The control method for the knee joint-assisted exoskeleton according to claim 1, characterized in that, In the downhill mode, when a joint angle greater than zero and a joint angular velocity greater than zero are detected, it is determined that the knee joint is accelerating its bending.

6. The control method for the knee joint-assisted exoskeleton according to claim 1, characterized in that, In the downhill mode, the formula for determining the motor output torque based on the joint angular velocity and the preset damping coefficient is as follows: ,in The preset damping coefficient, This represents the joint angular velocity.

7. The control method for the knee joint-assisted exoskeleton according to claim 6, characterized in that, If the motor output torque Less than the minimum output torque Then the motor outputs the target torque Limited to the minimum output torque .

8. The control method for the knee joint-assisted exoskeleton according to claim 1, characterized in that, The motor output torque calculated in the uphill or downhill mode is output after smoothing and limiting.

9. The control method for the knee joint-assisted exoskeleton according to claim 1, characterized in that, The uphill and downhill modes can be switched manually or automatically based on sensor data.

10. A knee-assisted exoskeleton control system for implementing the control method according to any one of claims 1 to 9, characterized in that, include: The signal acquisition module is used to collect thigh angular velocity data, knee joint angle data, and joint angular velocity data. The mode switching module is used to determine whether the current mode is uphill or downhill. The control calculation module is used to receive data from the signal acquisition module and the mode switching module, and to calculate the motor output torque. The torque output module is used to process the output torque of the motor and then drive the motor of the exoskeleton to output the corresponding torque.

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