Research On Design And Motion Control Of Lower Limb Rehabilitation Robot

Due to the increasing number of patients with hemiplegia caused by factors such as stroke and aging,the number of rehabilitation physicians under the tremendous pressure is relatively small.The traditional rehabilitation and treatment processes are mostly heavy and repetitive physical tasks.The treatment cycle expends long time and there are high requirements of the endurance of the doctor.So there is an urgent need to seek alternatives to replace physicians to help patients with rehabilitation training.The development of rehabilitation robot technology has brought the dawn to doctors and brought hope to patients for rehabilitation training.In this paper,based on a large number of related literature,a simple and easy-to-use pedal-type lower limb rehabilitation robot is designed.In the structural design of rehabilitation robots,this article analyzes the transmission mechanism of lower limbs in detail and discusses the advantages and disadvantages of various transmission methods.Considering comprehensively,this article adopts worm and gear transmission,and discusses the driving methods in detail,and determines the motor drive scheme in the end.After the transmission mode and driving mode are determined,this paper estimates the human-machine interaction torque,and determines the rated torque of the motor as well as reduction ratio along with dynamics simulation.Finally this article selects suitable servo equipment and gives the three-dimensional model figure of the complete machine.In order for patients to better train,this article simplified the human lower extremities and established a human-machine model after understanding the mechanism of human lower limb movement.Based on this model,a kinematics model was established using the vector method.Simulations on the matlab platform verify the correctness of the kinematics model;a human-machine dynamics model is established using the Lagrange's dynamical equations,which provides a theoretical basis for the study of the following control algorithms.In the control algorithm,this paper divides the three control modes to be implemented into two categories.The passive training mode is classified as position control and active and assisted training mode is classified as force control.As for position control,this paper studies the PID control algorithm and the calculation of torque method in detail.The PID control algorithm is simulated and the reasons of the simulation results are analyzed.The motion control is optimized,which makes the hip-knee joint of the lower extremities more uniform in angular velocity,without severe impact.As for force control,this paper studies carefully the impedance control,adaptive control,fuzzy control,and the combination of them.In the active and assisted training mode,simulations were performed using an impedance control algorithm.The results of the simulation show that when the patient's lower limb exists active force,the motor drive torque will be reduced accordingly to help the patient to exercise;When the active force of the patient's lower extremity is sufficient to drive itself,the motor will apply a reverse moment to increase the patient's muscle strength.In general,the algorithm proposed in this paper can implement these three kinds of motion modes.Finally,this paper gives the overall control scheme of the system,which provides reference for future hardware circuit connection.