Parameter Identification And Controller Design Of Lower Limb Exoskeleton Robot System

The exoskeleton is a kind of mechanical device that can be worn on the outside of the human body and assists the human body in walking.Therefore,it has important prac-tical significance and application value for the research of lower limb exoskeleton robot used in rehabilitation medicine.This article is to develop a set of lower exoskeleton robot system,which involves the design and implementation of robot platform,system param-eter identification,human-machine motion control,And use the robot platform to carry out relevant healthy people experiments,which laid a foundation for the research of key issues in the field of related rehabilitation engineering.Firstly,buildind a set of lower exoskeleton robot platform.The main work has the following points: 1.First of all,to improve the comfort of people with different lengths leg through the design of the stretchable concave link and the leg patch,the center of gravity of the man-machine is more centered,and the adjustable safety is designed according to the extreme position of the leg movement.Finally,in order to fully detect the coupling force and synchronization between man and machine,the three-dimensional force sensor and attitude sensor used for measuring the coupling torque and attitude error in various dimensions between man and machine.2.Secondly,design the measurement and control system according to the application scene of the lower extremity exoskeleton system.The design of the circuit system needs to consider the load power of the motor drive system and the hardware interface conversion.in order to improve the efficiency of algorithm devel-opment,a software platform based on the joint development of MATLAB and LabVIEW is designed for the lower extremity exoskeleton robot system.The software platform can automatically compile the algorithm into a dynamic link library recognized by the con-troller and call it directly.Secondly,model and parameter identification of the extremity robot system.Iden-tifying the parameters of the lower extremity exoskeleton system is the key to its appli-cation,lagrange dynamics modeling and human-machine contact force modeling based on its physical structure and motion characteristics.Using the excitation trajectory de-signed by B spline can reduce the ill-conditionedness of the regression matrix and effec-tively improve the accuracy of the system parameter identification results.In this paper,a heuristic algorithm based on biogeography learning particle swarm optimization(BLPSO)will be used for stimulus trajectory optimization and system parameter identification.By improving the search strategy,BLPSO can not only prevent the system parameters from converging to a local minimum,but also can improve the identification accuracy of system parameters.Then design the controller for the lower exoskeleton robot.The exoskeleton robot is a set of highly nonlinear systems.Design a set of backstepping control algorithm with human-machine coupling force and motion friction compensation for the ”machine-master-assisted” work way combined with the model parameters identified,the stability of the controller which has more design flexibility than model-free control(such as PID)proved by the stability analysis.Finally,debug the system and verify the algorithm for the constructed lower exoskele-ton robot platform.First,debug system from module communication,motor driver param-eter setting and sensor data calibration to make the system work in the optimal state.Sec-ondly,carry out the excitation trajectory tracking experiment on the debugged platform to collect data for parameter identification,by comparing with the GA and PSO identifi-cation results,the BLPSO identification results verify that the identification accuracy is higher,compared with the parameter results identified by GA and PSO algorithms,the accuracy of the parameter results identified by BLPSO is higher.Finally,the designed controller is used to carry out the human-machine-host auxiliary motion control experi-ment on the platform.Compared with the PID controller,the experimental results show that the backstepping controller has better gait following effect and wearing comfort.