| With the increasing degree of population aging in China,the incidence of stroke is increasing year by year.To improve the shortage of rehabilitation resources in China and reduce the working pressure of rehabilitation doctors,the lower limb rehabilitation robot has the advantages of strong repeatability and consistency of movement and rich training mode.Therefore,it has gradually become a research hotspot in the field of rehabilitation at home and abroad.Considering that the lower limb rehabilitation robot is object-oriented for patients with lower limb dysfunction,achieving safe and effective rehabilitation training is the main research goal of the lower limb rehabilitation robot.Aiming at the problem of motor function recovery of stroke patients in the later stage of rehabilitation,this paper takes the lower limb rehabilitation robot as the research object,and aims to provide a safe,effective,flexible and comfortable rehabilitation training environment.Based on the impedance control method,the control system is designed to realize the cooperative movement between the lower limb rehabilitation robot and the human lower limb.The main contents of this paper are as follows:(1)The kinematics-dynamics model is constructed for human-machine coupled lower limb rehabilitation robot.On the premise of human lower limb comfort,the lower limb bone-muscle structure is analyzed based on human anatomy,and evaluated the motion characteristics of lower limb rehabilitation training,and clarified the control requirements and objectives of lower limb rehabilitation robot.After reasonable simplification,the kinematics-dynamics model of lower limb rehabilitation robot with human-machine coupling is constructed,which provides a basis for the subsequent research on humanmachine interaction control method of lower limb rehabilitation robot.(2)An impedance controller design method is proposed for lower limb rehabilitation robot.To solve the secondary damage caused by human-machine confrontation caused by abnormal muscle activity of the affected limb,a closed-loop control model is built to realize compliant control based on the impedance control principle.The superiority of the control system is verified by comparative experiments.According to the Lyapunov stability principle,the stability of the system is proved,and a reasonable index is designed to evaluate the motion performance of the lower limb rehabilitation robot.The feasibility and effectiveness of the controller are confirmed by the experiment of the lower limb rehabilitation training platform.(3)A combined control strategy of impedance control and sliding mode variable structure is designed for lower limb rehabilitation robot.Aiming at the uncertainty of the control system caused by the unknown interference of the system,the impedance control is combined with the sliding mode variable structure control.The chattering problem is solved by analyzing the different motion modes of the sliding mode variable structure control.The sliding mode impedance controller and the non-singular terminal sliding mode impedance controller are projected by comparing the different approaching rate performance of the approaching mode.The superiority of the non-singular terminal sliding mode impedance controller based on the power reaching rate is demonstrated by comparing and dissecting the control performance.(4)A finite-time stable impedance control system to established for lower limb rehabilitation robot.An impedance control system satisfying finite-time stability is designed to improve the tracking performance and steady-state performance of the control system.The finite-time stability of the system is proved by Lyapunov principle.Through detailed comparative analysis,reasonable control parameters are selected to carry out numerical simulation experiments and platform experiments.The results show that the control system has high steady-state tracking accuracy and fast-tracking convergence speed,and the lower limb rehabilitation robot has ideal control performance. |
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