Gait simulation test platform and control method for lower extremity prostheses and assistive devices

Abstract

The application provides a gait simulation test platform and control method for lower limb prostheses and assistive devices, which is used to solve the problem that the existing test standard adopts fixed posture simplified single-axis loading, and cannot effectively reproduce the continuous rolling characteristics, kinematics and dynamics characteristics of human body support phase. The platform comprises a main support frame, a connecting rod actuator, a prosthesis fixing mechanism and a vertical force loading mechanism. The connecting rod actuator is used to reproduce the continuous motion trajectory and posture change in the human gait support phase. The vertical force loading mechanism is used to accurately realize dynamic ground reaction force loading and automatic mechanism reset. The control system synchronously controls the trajectory tracking of the main drive motor and the dynamic torque loading of the lifting motor. The application effectively balances the kinematic accuracy, structural rigidity and control simplicity through the connecting rod mechanism, and can more truly and efficiently evaluate the dynamic response and dynamic behavior of the prosthetic foot and assistive device under natural gait.

Description

Technical Field

[0001] This invention relates to the fields of rehabilitation engineering and biomechanical testing equipment. Specifically, it relates to a kinematics and dynamics reproduction testing platform for lower limb prostheses and its control method, which is particularly suitable for fatigue durability assessment, dynamic load characteristic analysis and gait-related performance verification of prosthetic feet and assistive devices. Background Technology

[0002] Bionic prosthetic feet (BPFs) help amputees regain a natural gait and improve their quality of life by mimicking the energy storage and release mechanisms of biological feet. However, prosthetic feet are subjected to approximately 1 to 3 million gait cycles per year during daily use. This long-term, complex alternating load can easily lead to structural fatigue failure, resulting in product recalls and even the risk of secondary injury to users. Furthermore, the development and design of prostheses require obtaining their dynamic and kinematic characteristics during actual movement for iterative development and functional verification. Traditional clinical patient testing is time-consuming and costly; however, dedicated testing platforms can significantly accelerate this iterative process. Therefore, efficient and accurate prosthetic foot performance testing is crucial for prosthetic design and testing, ensuring clinical safety.

[0003] Currently, ISO 10328, published by the International Organization for Standardization, is the main standard for testing lower limb prostheses. This standard requires prostheses to undergo up to 3 million cyclic loading cycles to certify their durability. However, the ISO 10328 testing protocol has significant limitations: Firstly, the simplified loading mode means that current national standard testing institutions only apply uniaxial static or cyclic loads at two fixed positions representing "heel strike" and "end of stance." Such a test setting lacks simulation of the continuous rolling of the foot during human walking, cannot reproduce the continuous migration process of the center of pressure (CoP) of the foot during the gait support phase, and cannot simulate the dynamic kinematic characteristics of strain and stress changes of the prosthetic footplate over time. Multiple studies have shown that prosthetic feet that pass ISO 10328 testing may still experience early failure or structural degradation in actual clinical use. This is because fixed-point loading fails to truly reflect the dynamic migration of stress distribution during walking, especially for composite material prosthetic feet, where fatigue damage accumulation is closely related to the actual rolling contact process.

[0004] To overcome these limitations, researchers have developed several alternative testing platforms. First, there are multi-dimensional loading rigs, such as the one developed by Marineli et al. While capable of multi-dimensional loading, these rigs still struggle to fully replicate the continuous migration trajectory of the CoP (Cohort of Foot) during natural walking. Meanwhile, Insam et al. proposed a hardware-in-the-loop (HiL) system combining a physical prosthetic foot with a virtual model. Although it can reproduce the center of mass motion and ground reaction force in real time, its core actuators often utilize the Stewart parallel platform. While the Stewart platform offers many degrees of freedom, it suffers from high actuator costs, complex control algorithms, large space requirements, and high energy consumption, making it unsuitable for large-scale, long-term routine fatigue testing. Some studies have also used serial robotic arms to simulate gait, but their cantilever structures lack stiffness under heavy loads, are prone to elastic deformation, have low energy efficiency, and incur high hardware and control costs.

[0005] In summary, the existing technology lacks a dedicated testing platform that can accurately reproduce continuous rolling kinematics and time-varying dynamics while also being compact, easy to control, inexpensive, and highly rigid. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention aims to provide a gait simulation testing platform and control method for lower limb prostheses and assistive devices. Through biomechanical data-driven trajectory optimization and force-position heterogeneous collaborative control, it achieves an engineering balance of compact structure, simplified control, high rigidity, and low cost while ensuring accurate reproduction of gait trajectories. This provides a more optimized testing environment for the research and development verification, dynamic load study, and fatigue durability assessment of prosthetic feet and assistive devices.

[0007] A gait simulation testing platform for lower limb prostheses and assistive devices, characterized in that it includes: The support frame provides a rigid mounting reference and overall support; A linkage actuator includes a multi-link mechanism, one link of which is a prosthesis clamping link. A prosthesis fixing mechanism is installed on the prosthesis clamping link for clamping and installing the lower limb prosthesis or assistive device to be tested. The linkage actuator drives the lower limb prosthesis or assistive device to be tested to move and simulate the continuous kinematics and dynamic parameters of the human lower limb during the movement process. A vertical force loading mechanism is used to apply a dynamic vertical ground reaction force to the sole of the foot of the lower limb prosthesis or assistive device of the human being under test during the gait cycle. The main control system is used to synchronously control the linkage actuator and the vertical force loading mechanism, and to synchronously coordinate gait trajectory reproduction and load loading.

[0008] Furthermore, the linkage actuator is selected from any one or more combinations of the following, driven by one or more drive motors to reproduce the dynamics and kinematic parameters during continuous lower limb joint movements: Single-degree-of-freedom four-bar linkage; Two-degree-of-freedom five-bar linkage; Complex linkage mechanisms with six or more degrees of freedom; Parallel linkage mechanism; Alternatively, it can be a hybrid drive mechanism consisting of the aforementioned linkage mechanism, linear guide rail, and rotary joint.

[0009] When the linkage actuator is a closed-chain linkage mechanism, a single-degree-of-freedom four-bar linkage is the preferred option. The links are connected by revolute joints; rolling bearings are installed at the hinge positions to reduce friction and improve transmission accuracy; one end of the link is hinged to the support frame, and the other end is connected to the prosthesis fixation mechanism.

[0010] The bearings include, but are not limited to, crossed roller bearings and other bearings used for transmitting driving force or distributing the overall force of the linkage mechanism, and are installed between linkage mechanisms or between the linkage mechanism and the mounting frame.

[0011] Furthermore, the linkage actuator also includes a drive linkage, a support linkage, and a frame. The frame is fixedly connected to the support frame. Both ends of the drive linkage are hinged to the frame and the prosthesis clamping linkage, respectively. The other end of the prosthesis clamping linkage is hinged to the support linkage, and the other end of the support linkage is hinged to the frame. The drive linkage, the prosthesis clamping linkage, the support linkage, and the frame form a four-bar linkage structure. A prosthesis fixing mechanism is installed on the prosthesis clamping linkage for clamping and installing the lower limb prosthesis or assistive device to be tested, thereby simulating the continuous kinematics and dynamic parameters of the human lower limb prosthesis or assistive device during movement. A linkage drive motor is provided, with its base mounted on the support frame. The motor output shaft of the linkage drive motor is fixedly connected to the drive linkage, and is used to drive the drive linkage to achieve rotational movement.

[0012] Furthermore, the lengths of the drive link, support link, prosthesis clamping link, and frame, as well as the installation position of the prosthesis fixing mechanism on the prosthesis clamping link, need to be optimized to simulate the continuous kinematics and dynamic parameters of the human lower limb prosthesis during movement. The optimization of the link geometry parameters is achieved through a trajectory synthesis algorithm, and the specific steps include: Construct a weighted objective function that includes lower limb position error and attitude angle error. ; Define constraints, which include at least the following: The effective range constraint of the transmission angle (constrains the angle of the drive link and the prosthesis clamping link to be within 40-140 degrees throughout the entire motion range; if it exceeds this range, the transmission is marked as abnormal and the calculation result is discarded), the branch defect avoidance constraint (in the process of fitting the mechanism, the trajectory point of a target may correspond to multiple solutions, so the motion of the mechanism must be smooth and there should be no abrupt changes in angle to prevent the failure of the optimization algorithm due to multiple solutions), and the link length compactness constraint (discards the calculation results of the link length exceeding the manually set target limit to prevent the situation where some trajectory fitting accuracy is good but the length is too long). An optimization algorithm is used to solve for the linkage frame coordinates (i.e., the installation position of the prosthesis fixation mechanism in the prosthesis clamping link), the length of each link, and the installation angle, thereby minimizing the objective function and obtaining the optimal link geometry parameters. The installation angle is a specific tilt angle between the lower leg direction of the prosthesis and the prosthesis clamping link.

[0013] Furthermore, the trajectory synthesis algorithm performs global optimization by minimizing the weighted sum of position and orientation errors: , In this formula, and The weights manually applied in this function are manually adjusted to balance trajectory accuracy and angle accuracy; the desired trajectory can be represented by triples ( , , This is represented by data obtained through physical measurements in the laboratory, and then each point on the mechanism's motion trajectory is calculated separately. , , Geometric distance from the desired point and the absolute error value of the angle The overall error is described by combining the above weights. The weighted errors of each point are summed to obtain the final overall error. The overall error is then optimized to reach its minimum value, which serves as the objective of the optimization algorithm.

[0014] Furthermore, the linkage drive motor is a power module capable of rotational motion, used to drive the linkage mechanism to output the desired posture, and reproduce the kinematic and dynamic parameters of the lower limb joints for driving the linkage mechanism.

[0015] Furthermore, the linkage drive motor is a motion module that can provide sufficient torque and response speed. It outputs torque through a reduction mechanism or direct drive to drive the linkage actuator to complete a preset gait trajectory.

[0016] Furthermore, the vertical force loading mechanism is arranged below the prosthetic foot to apply a dynamic ground reaction force to the prosthetic foot during the gait cycle.

[0017] Furthermore, the direction of motion of the vertical force loading mechanism is coaxial or coplanar with the main force direction of the prosthetic foot during the support phase; the vertical force loading mechanism is in contact with the bottom of the prosthetic foot; and a load in the vertical or equivalent force direction is applied to the prosthesis through linear motion.

[0018] The vertical force loading mechanism mainly includes a Z-axis linear motion module, a loading platform, a force sensor, an elastic mechanism, and a drive assembly. In addition to performing dynamic load loading, the vertical force loading mechanism can also assist the linkage actuator in achieving unloaded reset and return to its original position during the unloaded phase of the test cycle.

[0019] The vertical force loading mechanism is arranged vertically and configured to apply dynamic ground reaction force (GRF) to the prosthetic foot during the gait cycle or to provide mechanism reset assistance during the non-loaded stroke.

[0020] The force sensor is positioned between the loading platform and the transmission assembly, or below the contact area between the loading platform and the sole of the prosthesis under test, to detect the vertical reaction force applied by the loading platform to the sole of the prosthesis under test in real time. The main control system adjusts the output torque of the rotary motor or linear motor based on the error between the force sensor feedback value and the target ground reaction force curve, thereby achieving dynamic load closed-loop control.

[0021] The elastic mechanism is connected in series between the drive assembly and the loading platform. The elastic mechanism can be a compression spring, an elastic sheet, an elastic rubber component, or other elastic elements with measurable elastic deformation. By detecting the deformation of the elastic mechanism or the feedback signal from the force sensor, the compliance during vertical force loading can be improved, rigid impacts reduced, and the accuracy of dynamic force control enhanced.

[0022] The drive components include, but are not limited to, high-response servo motors and large-lead precision ball screw mechanisms, or directly using high-thrust linear motors, or hydraulic actuators and other modules capable of outputting linear motion.

[0023] Furthermore, the main control system includes a microprocessor unit, and the main control system synchronously controls the linkage drive motor and the vertical force loading mechanism within a set control cycle through an industrial communication network or fieldbus system.

[0024] Furthermore, the prosthesis fixation mechanism has a multi-axis spatially adjustable installation interface, which can adaptively adapt to different models of lower limb prostheses or assistive devices. During physical calibration, it ensures that the clamping calibration center is highly aligned with the instantaneous rotation center of the output end of the linkage actuator, so as to minimize the parasitic additional bending moment caused by installation eccentricity.

[0025] Furthermore, the control system is communicatively connected to the drive unit of the linkage actuator and the vertical force loading mechanism, respectively, and is used to perform biomechanical trajectory mapping, mechanism parameter optimization solution and multi-axis force-position cooperative control.

[0026] Furthermore, the main control system controls the linkage drive motor to operate in a position or speed closed-loop tracking mode (such as cyclic synchronous position mode CSP), and controls the vertical force loading mechanism to operate in a torque or force feedback control mode (such as cyclic synchronous torque mode TM). The main control system achieves dynamic force loading through position-speed-torque cascaded closed-loop control strategy or impedance control strategy, so as to balance trajectory following accuracy and mechanical compliance.

[0027] The main control system is a microprocessor unit, including but not limited to a microcontroller unit (MCU), a digital signal processor (DSP), a field-programmable gate array (FPGA), or an industrial control computer. The main control system synchronously controls the linkage drive motor and the auxiliary lifting system drive components within a set control cycle through an industrial communication network or fieldbus system (such as CAN bus, EtherCAT, PROFINET, etc.).

[0028] In addition, the present invention also proposes a control method for the above-mentioned gait simulation test platform, which is characterized by including the following steps: Acquire trajectory data of the human gait support phase and ground reaction force data; Map the trajectory data to the test platform coordinate system; The control linkage actuator reproduces the trajectory; The vertical force loading mechanism is synchronously controlled to apply the corresponding dynamic load.

[0029] Furthermore, when reproducing the trajectory, an advanced gravity and friction compensation algorithm is used to correct the output torque by identifying the static load and nonlinear friction of the vertical force loading mechanism.

[0030] Compared with the prior art, the present invention has the following significant advantages: 1. Accurate gait trajectory reproduction compensates for deficiencies in standard testing. Through a data-driven trajectory synthesis algorithm, the continuous rolling characteristics of real human gait are encoded into the link geometry parameters. Experimental verification shows that the optimized mechanism can completely reproduce the rolling process during the support phase, with a root mean square error (RMSE) as low as 3.337 mm and a Pearson correlation coefficient of 0.9992. This effectively overcomes the limitation of ISO 10328 fixed-point loading in failing to reflect dynamic stress transfer, and more realistically elicits the fatigue damage mechanism of composite material prosthetic feet, or can be applied to the dynamic response measurement of prostheses.

[0031] 2. Balancing high rigidity with engineering compactness: Compared to Stewart platforms or serial robotic arms, the linkage actuator used in this invention is a closed-chain structure, inherently possessing high bending stiffness and low elastic deformation characteristics. The preferred single-degree-of-freedom four-bar solution reduces peak torque requirements and control complexity while sacrificing minor trajectory errors, significantly reducing hardware costs, system size, and long-term operating energy consumption, making it more suitable for fatigue testing scenarios involving millions of cycles.

[0032] 3. Force-position heterogeneous collaborative control improves dynamic loading accuracy. It innovatively adopts a heterogeneous architecture for force-position collaborative control using dual motors, combined with a high-speed synchronous bus for high-speed control cycle synchronization, decoupling the control conflicts between trajectory tracking and force loading. This architecture avoids the rigidity of single-position mode force control or trajectory drift of single-torque mode. It also allows for the introduction of gravity compensation, nonlinear friction compensation, and high-order impedance control, achieving efficient testing and system dynamic response.

[0033] 4. Standardized testing processes and accelerated R&D iterations: A controllable laboratory testing platform enhances testing frequency and efficiency during prosthetic development. This platform replaces time-consuming and costly clinical field testing, providing a repeatable and quantifiable standardized experimental environment for design optimization, dynamic characteristic comparison, and durability certification of prosthetic feet and assistive devices. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the spatial structure layout of the test platform according to an embodiment of the present invention, showing the positional relationship of the support frame, linkage actuator, prosthesis fixation mechanism and vertical force loading mechanism; Figure 2 This is a schematic diagram of the prosthesis clamping linkage structure in the linkage actuator of an embodiment of the present invention; Figure 3 This is a schematic diagram of the supporting link structure in the linkage actuator according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the drive rod structure in the linkage actuator of an embodiment of the present invention; Figure 5 This is a schematic diagram of the rack of the test platform according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the vertical force loading mechanism structure of the test platform in an embodiment of the present invention; Figure 7 This is a schematic diagram illustrating the trajectory fitting principle of the five-bar and four-bar linkages involved in the embodiments of the present invention; Figure 8 A schematic diagram of the ankle trajectory and lower leg angle during the support phase of the human gait; Figure 9 This is a simplified kinematic geometric model of the four-bar linkage topology system in an embodiment of the present invention; Figure 10 This is a motion error analysis and force state diagram of the four-bar linkage after algorithm optimization in an embodiment of the present invention; Figure 11 This is a simplified kinematic geometric model of the five-bar linkage topology system in an embodiment of the present invention; Figure 12 This is a motion error analysis and force state diagram of the five-bar linkage after algorithm optimization in an embodiment of the present invention; Figure 13 This is a diagram showing the hardware topology and communication network structure of the test platform control system of this invention; Figure 14 The image shows experimental data on trajectory fit obtained from physical prototype testing in this embodiment. Figure 15 This is a graph showing experimental data on angle tracking error obtained from testing the physical prototype in this embodiment. Figure 16 The graph shows experimental data of motor output torque obtained from physical prototype testing in this embodiment. As shown in the figure: 1. Supporting framework 2. Linkage actuator, 2-1a. Bearing mounting position, 2-1b. Prosthesis mounting position, 2-1c. Ankle joint origin of the tested prosthesis, 2-1d. Bearing mounting position, 2-2a. Bearing mounting position, 2-2b. Bearing mounting position, 2-3a. Bearing mounting position, 2-3b. Bearing mounting position, 21. Drive linkage, 22. Prosthesis clamping linkage, 23. Support linkage, 24. Frame, 3. Prosthetic fixation mechanism, 4. Frame, 4a. Bearing mounting position, 4b. Base fixing position, 4c. Bearing mounting position 5. Vertical force loading mechanism, 5a. Lifting loading plane, 5b. Force sensor, 5c. Spring, 5d. Ball screw, 5e. Linear guide, 5f. Support arm; 6. Drive motor. Detailed Implementation

[0035] To make the technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the specific embodiments described herein and the specific models and parameters listed are only for explaining the present invention and are not intended to limit the scope of protection of the present invention. Any equivalent substitutions or equivalent extensions made by those skilled in the art based on the teachings of the present invention shall fall within the scope of protection claimed by the present invention.

[0036] Example A gait simulation testing platform for lower limb prostheses and assistive devices, such as Figure 1As shown, it includes a support frame 1, a linkage actuator 2, a prosthesis fixation mechanism 3, a frame 4, a vertical force loading mechanism 5, a drive motor 6, and a main control system.

[0037] See Figure 2 The linkage actuator 2 includes a drive link 21, a prosthesis clamping link 22, a support link 23, and a frame 24. The frame 24 is fixed to the support frame 1 by bolts. The drive link 21, the prosthesis clamping link 22, the support link 23, and the frame 24 are connected by bearings. The support frame 1 is made of high-strength aluminum profile to ensure good deformation resistance under high load cyclic conditions. The linkage actuator 2 is mounted on the support frame 1 via the frame 4 and is used to reproduce the continuous rolling motion trajectory of the prosthesis foot during the gait support phase. The prosthesis clamping link 22, the drive link 21, and the support link 23 are as follows: Figure 2 , 3 As shown in Figure 4, they are fixed to each other and transmit load through bearing mounting positions.

[0038] Specifically, bearing mounting positions 2-3a and 2-1d are connected by bearings, bearing mounting positions 2-2a and 2-1a are connected by bearings, and bearing mounting positions 2-2b and 4a are connected by bearings. For example... Figure 2 As shown, the prosthesis clamping link 22 includes a link body with a triangular structure. Bearing mounting positions 2-1a and 2-1d, prosthesis mounting position 2-1b, and ankle joint origin 2-1c are located at the three corners of the triangular structure, respectively. The bearing mounting positions 2-1a and 2-1d are connected to the drive link 21 and the support link 23 through bearings, respectively. The prosthesis mounting position 2-1b realizes the clamping and adjustment of the prosthesis by installing the prosthesis fixing mechanism 3. The ankle joint origin 2-1c is a reserved mark and serves as a trajectory output point. During installation, it achieves a precise trajectory by aligning with the prosthesis ankle joint.

[0039] like Figure 3 As shown, the support link 23 includes a link body, and bearing mounting positions 2-2a and 2-2b are located at both ends of the link body. The support link is connected to other links and mounting frames by mounting bearings at its bearing mounting positions 2-2a and 2-2b to realize the transmission of force.

[0040] like Figure 4 As shown, the drive link 21 includes a link body, and bearing mounting positions 2-3a and 2-3b are located at both ends of the link body. The support link is equipped with bearings at its bearing mounting positions 2-3a and 2-3b and connected to other links and drive motors to realize the drive of the entire link system.

[0041] The linkage drive motor is used to drive the drive link 21 to output the desired posture, and reproduces the kinematic and dynamic parameters of the lower limb joints to drive the linkage mechanism. The linkage drive motor can be a motion module that can provide sufficient torque and response speed, such as a joint motor, brushless motor, or servo motor. It outputs torque through a reduction mechanism or direct drive to drive the linkage actuator to complete the preset gait trajectory movement.

[0042] like Figure 5 As shown, the frame 4 is provided with bearing mounting positions 4a and 4c and base fixing position 4b. The frame 4 is fixed to the support frame 1 through the base fixing position 4b, providing space for the entire test system. At the same time, the motor and bearings are installed at the bearing mounting positions 4a and 4c to fix and drive the entire electrical connection system.

[0043] like Figure 6 As shown, the vertical force loading mechanism 5 includes a lifting loading plane 5a, a force sensor 5b, a spring 5c, a ball screw 5d, a linear guide rail 5e, and a support arm 5f. The drive motor 6 and the ball screw 5d of the vertical force loading mechanism 5 are both mounted in a fixed base. The linear guide rail 5e is distributed on both sides of the ball screw 5d, and the slider moves along the linear guide rail 5e. The two sliders are connected by a connecting plate. The spring 5c ​​is positioned between the nut pair mating with the ball screw 5d and the connecting plate, and is sleeved on the ball screw 5d. A force sensor 5b is also provided between the spring 5c ​​and the connecting plate. The spring 5c ​​and the nut pair form a series elastic actuator, improving the control accuracy of the applied vertical reaction force from the ground. The support arm 5f and the lifting loading plane 5a are fixed on the slider. The support arm 5f supports the lifting loading plane 5a, realizing the conversion between motor torque and plane loading torque. The lifting loading plane 5a is used to contact the sole of the foot of the prosthesis or human assistive device under test, and to apply dynamic ground vertical reaction force to the sole of the foot of the prosthesis or human assistive device under test during the gait cycle.

[0044] In a preferred embodiment of the present invention, the linkage mechanism may be a five-bar linkage.

[0045] Specifically, the five-bar linkage is controlled by two motors to drive the five-bar linkage to reproduce the gait trajectory, resulting in better trajectory accuracy.

[0046] like Figure 7 As shown, the right side displays a schematic diagram of the trajectory fitting principle for a four-bar linkage, while the left side displays a schematic diagram of the trajectory fitting principle when the linkage actuator uses a five-bar linkage.

[0047] like Figure 8 The diagram shown illustrates the trajectory of the ankle and the angle of the lower leg during the support phase of the human gait as described in this invention.

[0048] like Figure 9 The diagram shown is a simplified representation of the trajectory fitting mechanism of the four-bar linkage of the present invention, including the lengths of the driving link 21, the prosthesis clamping link 22, and the support link 23, the coordinates of the frame 24, and a schematic diagram of the trajectory of the linkage mechanism. The optimized prosthesis lower leg direction and the installation angle Φ of the prosthesis clamping link are -178.11°.

[0049] like Figure 10 As shown, the trajectory error and force analysis of the four-bar linkage of the present invention are obtained by trajectory fitting. The fitted four-bar linkage reproduces the maximum torque of the motor in the entire support phase of 107.2 Nm, and the entire system can be driven by a single motor.

[0050] like Figure 11 The diagram shown is a simplified diagram of the linkage actuator of the present invention using a five-bar linkage trajectory fitting method.

[0051] like Figure 12 As shown, the trajectory error and force analysis of the linkage actuator of the present invention are obtained by fitting the trajectory of a five-bar linkage. The fitted five-bar linkage needs to be driven by two motors, with corresponding maximum torques of 89.1 nm and 81.4 nm, respectively.

[0052] like Figure 13 The diagram shown is a control logic block diagram of the present invention. The host computer control board communicates synchronously with the motor through the CANopen protocol to realize the driving of the linkage and the loading of the vertical force loading mechanism.

[0053] like Figure 14 The figure shows the measured trajectory and the expected trajectory of the present invention under the optical motion capture system in the laboratory.

[0054] like Figure 15 The figure shows the measured angle and expected angle of the present invention in the laboratory optical motion capture system.

[0055] like Figure 16 The figure shows the actual output torque measurement results of the motor in the laboratory. It can be seen that the mechanism completely reproduces the angle and trajectory changes of the entire support phase process. The root mean square error of the expected trajectory and the loaded trajectory is only 3.337 mm. During the test, by increasing the stiffness of the support frame, adding local reinforcement structures, or using a high-strength integral frame, the structural deformation during the loading process can be further reduced, thereby improving the angle tracking accuracy and load reproduction stability.

[0056] In a preferred embodiment of the present invention, the power source of the vertical force loading mechanism can be a linear motor.

[0057] Specifically, the linear motor replaces the ball screw and drive motor 6, avoiding the redundant weight of the ball screw and the hysteresis response and backlash caused by the screw, thus achieving high dynamic response and precise force loading.

[0058] In a preferred embodiment of the present invention, the prosthesis fixation mechanism has a multi-axis adjustment structure; the prosthesis can be fixed via bolt connection, clamping structure, or quick-installation interface. The prosthesis fixation mechanism can adjust the installation position to ensure that the calibration center of the prosthesis foot is aligned with the motion center of the connecting rod output end, thereby reducing the additional bending moment caused by installation eccentricity.

[0059] In a preferred embodiment of the present invention, the multi-axis adjustment mechanism is connected at one end to the prosthesis clamping link. The operation of the prosthesis fixation mechanism relative to the prosthesis clamping link allows for tilt adjustment in two directions. It includes a first adjustment component and a second adjustment component arranged in different directions. The first adjustment component includes a first adjustment screw and a first adjustment nut that cooperates with it. The first adjustment nut is used to change the support position of the prosthesis fixation mechanism in the direction parallel to the prosthesis clamping link, thereby adjusting the tilt angle of the connecting rod in that direction. The second adjustment component includes a second adjustment screw and a second adjustment nut that cooperates with it. The second adjustment nut is used to change the support position of the prosthesis fixation mechanism in the direction perpendicular to the prosthesis clamping link, thereby adjusting the tilt angle of the connecting rod in that direction. By adjusting the first and second adjustment components respectively, the posture adjustment of the connecting rod in different directions can be achieved to compensate for tilt angle deviations caused by force deformation during prosthesis testing, or to actively apply a preset unbalanced tilt angle.

[0060] In a preferred embodiment of the present invention, the bearing is a crossed roller bearing. The crossed roller bearing is easy to install and can withstand radial, axial forces and moment loads.

[0061] In a preferred embodiment of the present invention, the drive motor may be a common articulated motor or a combination of a regular motor and a reducer.

[0062] Specifically, the motor can be a stepper motor, servo motor, torque motor, direct drive motor, or quasi-direct drive motor, etc.

[0063] As a preferred embodiment of the present invention, the support frame is not limited to the conventional industrial aluminum profile bolted structure. It can be constructed by using an integrally formed high-strength cast iron frame assembly, adding steel structure welded reinforcing ribs to local stress nodes, or selecting load-bearing materials with a larger cross-sectional modulus, etc., to build a high-rigidity, deformation-resistant base platform.

[0064] In a preferred embodiment of the present invention, the main control system is communicatively connected to the linkage drive motor and drive motor 6, respectively, for synchronously coordinating gait trajectory reproduction and load loading. The main control system is centered on an industrial-grade control motherboard or motion controller. This controller incorporates a high-performance microprocessor unit (e.g., but not limited to MCUs, DSPs, FPGAs, or industrial control computers with floating-point capabilities), possessing high-speed computing power to handle complex pose inverse kinematics and dynamic matrices. The controller uses a highly deterministic industrial fieldbus (such as CANopen, EtherCAT, PROFINET, etc.) as the communication layer, acting as the master station to send synchronization commands to each drive slave station, ensuring extremely low command latency for multi-axis coordination.

[0065] In a preferred embodiment of the present invention, the linkage drive motor (e.g., a direct-drive or geared servo motor with sufficient torque margin) is configured to operate in a position or speed tracking closed-loop mode (such as the Cyclic Synchronous Position Mode (CSP) in the CiA 402 standard). In this mode, the underlying driver performs high-frequency closed-loop adjustments according to the position commands issued by the host computer, overcoming external nonlinear load resistance and achieving high-response spatial trajectory tracking.

[0066] As a preferred embodiment of the present invention, the underlying system control layer may incorporate a gravity and hybrid friction compensation algorithm based on parameter identification.

[0067] Specifically, due to the static load gravity of the vertical force loading mechanism and the nonlinear frictional forces generated by the guide rail / screw assembly (including Coulomb friction during static startup and viscous friction varying with speed), the main controller extracts the current speed and acceleration characteristics of the motor through an observer during operation and establishes a friction damping prediction model. The calculated compensation torque is then superimposed on the positive command flow. This adaptive compensation strategy effectively eliminates the interference of mechanical hysteresis on the force feedback system, ensuring that the output thrust accurately reflects the real ground interaction force characteristics.

[0068] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A gait simulation testing platform for lower limb prostheses and assistive devices, characterized in that, include: The support frame provides a rigid mounting reference and overall support; A linkage actuator includes a multi-link mechanism, one link of which is a prosthesis clamping link. A prosthesis fixing mechanism is installed on the prosthesis clamping link for clamping and installing the lower limb prosthesis or assistive device to be tested. The linkage actuator drives the lower limb prosthesis or assistive device to be tested to move and simulate the continuous kinematics and dynamic parameters of the human lower limb during the movement process. A vertical force loading mechanism is used to apply a dynamic vertical ground reaction force to the sole of the foot of the lower limb prosthesis or assistive device of the human being under test during the gait cycle. The main control system is used to synchronously control the linkage actuator and the vertical force loading mechanism, and to synchronously coordinate gait trajectory reproduction and load loading.

2. The gait simulation testing platform according to claim 1, characterized in that: The linkage actuator is selected from any one or more combinations of the following, and is driven by one or more drive motors to reproduce the dynamics and kinematic parameters of continuous lower limb joint movements: Single-degree-of-freedom four-bar linkage; Two-degree-of-freedom five-bar linkage; Complex linkage mechanisms with six or more degrees of freedom; Parallel linkage mechanism; Alternatively, it can be a hybrid drive mechanism consisting of the aforementioned linkage mechanism, linear guide rail, and rotary joint.

3. The gait simulation testing platform according to claim 1, characterized in that, The linkage actuator further includes a drive linkage, a support linkage, and a frame. The frame is fixedly connected to the support frame. Both ends of the drive linkage are hinged to the frame and the prosthesis clamping linkage, respectively. The other end of the prosthesis clamping linkage is hinged to the support linkage, and the other end of the support linkage is hinged to the frame. The drive linkage, the prosthesis clamping linkage, the support linkage, and the frame form a four-bar linkage structure. A prosthesis fixing mechanism is installed on the prosthesis clamping linkage for clamping and installing the lower limb prosthesis or assistive device to be tested, thereby simulating the continuous kinematics and dynamic parameters of the human lower limb prosthesis or assistive device during movement. A linkage drive motor is provided, with its base mounted on the support frame. The motor output shaft of the linkage drive motor is fixedly connected to the drive linkage, and is used to drive the drive linkage to achieve rotational movement.

4. The gait simulation testing platform according to claim 3, characterized in that, The lengths of the drive link, support link, prosthesis clamping link, and frame, as well as the installation position of the prosthesis fixing mechanism on the prosthesis clamping link, need to be optimized to simulate the continuous kinematics and dynamic parameters of the human lower limb prosthesis during movement. The optimization of the link geometry parameters is achieved through a trajectory synthesis algorithm, and the specific steps include: Construct a weighted objective function that includes lower limb position error and attitude angle error. ; Set constraints, which include at least: effective range of transmission angle constraint, branch defect avoidance constraint, and link length compactness constraint; The frame coordinates, lengths of each link, and installation angles are solved using an optimization algorithm to minimize the objective function, thereby obtaining the optimal link geometry parameters.

5. The gait simulation testing platform according to claim 3, characterized in that: The linkage drive motor is a power module capable of rotational motion, used to drive the linkage mechanism to output the desired posture, and reproduces the kinematic and dynamic parameters of the lower limb joints to drive the linkage mechanism. or, The aforementioned linkage drive motor is a motion module that can provide sufficient torque and response speed. It outputs torque through a reduction mechanism or direct drive to drive the linkage actuator to complete a preset gait trajectory.

6. The gait simulation testing platform according to claim 1, characterized in that: The vertical force loading mechanism includes a rotary motor and a ball screw mechanism. The rotation of the motor drives the ball screw mechanism to move up and down, thereby dynamically adjusting the vertical ground reaction force on the sole of the foot of the prosthesis or human assistive device under test. or, The vertical force loading mechanism includes a linear motor, which moves up and down to dynamically adjust the vertical ground reaction force on the sole of the foot of the prosthesis or human assistive device under test.

7. The gait simulation testing platform according to claim 6, characterized in that: A force sensor is installed inside the vertical force loading mechanism to dynamically detect the magnitude of the applied vertical reaction force on the ground.

8. The state simulation test platform according to claim 7, characterized in that: The vertical force loading mechanism is equipped with an elastic mechanism, which forms a series elastic actuator with the ball screw mechanism or linear motor to improve the control accuracy of the applied vertical reaction force on the ground.

9. The gait simulation testing platform according to claim 1, characterized in that: The prosthesis fixation mechanism has a multi-axis spatially adjustable installation interface, which can adaptively adapt to different models of lower limb prostheses or assistive devices. During physical calibration, it ensures that the clamping calibration center is highly aligned with the instantaneous rotation center of the output end of the linkage actuator to minimize parasitic additional bending moment caused by installation eccentricity.

10. The gait simulation testing platform according to claim 1, characterized in that: The main control system controls the linkage drive motor to operate in position or speed closed-loop tracking mode, and controls the vertical force loading mechanism to operate in torque or force feedback control mode. The main control system achieves dynamic force loading through position-speed-torque cascade closed-loop control strategy or impedance control strategy, so as to balance trajectory following accuracy and mechanical compliance.

11. The control method according to any one of claims 1-10, Its features are, Includes the following steps: Acquire trajectory data of the human gait support phase and ground reaction force data; Map the trajectory data to the test platform coordinate system; The control linkage actuator reproduces the trajectory; The vertical force loading mechanism is synchronously controlled to apply the corresponding dynamic load.

12. The control method according to claim 11, characterized in that: When reproducing the trajectory, an advanced gravity and friction compensation algorithm is used to correct the output torque by identifying the static load and nonlinear friction of the vertical force loading mechanism.

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