| The number of patients with upper limb disability due to stroke is increasing with the aging population in China.The rehabilitation treatment is expensive,since most of rehabilitation equipment are imported from oversea.Most patients choose artificial rehabilitation.However the artificial treatment is time cost,sometime improper treatment will cause secondary harm to patients.A twisted string driven upper limb rehabilitation robot is proposed in this paper in order to solve the above problems,which can be realized rehabilitation training of shoulder and elbow joints for patients.The mathematical model of the proposed twisted string drive is established first,and the dynamic equation for the twisted string driver is derived.The torsion string self-winding phenomenon occurs during the movement,and the maximum angle of the drive motor and the maximum displacement of the torsion string drive device are derived.A new two-degree-of-freedom twisted string drive upper limb rehabilitation robot is proposed,and whose structure is designed in Solid Works,which can realize the upper limb rehabilitation movement of shoulder and elbow joint forward flexion/extension.Three different rehabilitation training actions is designed to assist patients in treatment.The kinematics and dynamics model of the twisted string driven upper limb rehabilitation robot were established based on the D-H method and the Lagrange equation.The numerical simulation of the three rehabilitation training actions of the rehabilitation robot were carried out through MATLAB Robot Toolbox,and the simulation results were the same as the derived kinematic and dynamic equation calculation values,which verified the correctness of the established kinematic and dynamic model of the twisted string drive upper limb rehabilitation robot.A dual closed-loop control method of DC motor based on Improved genetic algorithm(IGA)is developed,which can improve the performance of the drive motors in the upper limb rehabilitation robot.The transfer function of each link of the speed loop of the DC motor double closed-loop control system is established,and the optimal value of the sliding mode parameters is tuned by the IGA joint speed loop MATLAB/Simulink simulation model.The numerical simulation and experimental validation of the novel sliding mode speed controller are carried out with the traditional PID controller,ordinary sliding mode speed controller and ordinary sliding mode speed controller tuned by ordinary genetic algorithm.The results show that the control method has obvious advantages in overshoot,response speed and robustness,and the application of this control method to drive the motor can further improve the control performance of the torsion string drive upper limb rehabilitation robot control system.The control system of the twisted string drive upper limb rehabilitation robot is setup based on the above DC motor control method.Numerical simulation of the control system is carried out in MATLAB/Simulink,and the simulation results showed that the designed control system has good robustness.An experimental platform for twisted string drive upper limb rehabilitation robot was built based on the dSPACE 1202 semi-physical simulation platform and three rehabilitation training motion control experiments were carried out.The experimental results show that the designed rehabilitation training action can realized with the proposed robot with acceptable performance.The experimental and simulation results are compared,and the average deviation model is used to prove the correctness of the established mathematical model of twisted string drive and the kinematic and dynamic model of twisted string drive upper limb rehabilitation robot.Finally,the experimental joint acceleration was used as the evaluation index of rehabilitation training,and the stability evaluation of the training results was carried out,and the evaluation results showed that the rehabilitation training process had good stability and can be applied to patients’ upper limb rehabilitation,increasing the versatility of the upper limb rehabilitation robot. |
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