Research On Structural Dcsign And Control Method Of Exoskeleton Lower Limb Rehabilitation Robot

The exoskeleton lower limb rehabilitation robot is a medical service robot used to assist patients with hemiplegia or loss of exercise due to a stroke to do lower limb rehabilitation training.It replaces the artificial rehabilitation training performed by traditional rehabilitation therapists and provides patients with more precise,more objective and more effective rehabilitation process.With the aging of the population and the increase of patients with hemiplegia,how to design a more flexible lower limb rehabilitation robot has become a key research direction in the field of rehabilitation technology.This paper mainly studies the structure design,driving and control methods of lower limb rehabilitation robot.The specific research work is as follows:1)With an in-depth analysis of the human lower limb anatomy and gait movement mechanism,the structural freedom of the lower limb rehabilitation robot and joint movement angle indicators are determined,and the corresponding structural design objectives are proposed according to the bionics principle.The standard gait discrete data is obtained by OpenSim and used for dynamic simulation and joint trajectory tracking after fitted in Matlab,which provides a theoretical basis for the latter design and control of joint moving.2)Comparing the advantages and disadvantages of motor,hydraulic and pneumatic drive,a new flexible drive is chosen: pneumatic muscles drive the mechanical leg joint rotation by forming pulling mechanism.A three-dimensional model of the lower limb rehabilitation robot structure is established in Solidworks,and detailed research and design meeting the requirements of support,transmission,connection and safety limit are carried out.Firstly,the kinematics equation of human-machine system is established by the D-H method.Then the dynamic model from the supporting phase and the swing phase is established with the Lagrange method.Finally,the process of the rehabilitation robot driving the lower limbs to normal gait is stimulated in Adams to verify the model's correctness,and the selection of pneumatic muscles is completed based on the simulated torque curve.3)The static mathematical model of a single pneumatic muscle is established by analytical method.The pressure of the pneumatic muscle cavity is controlled by using the high-speed on-off valve and the mass flow equation and the pressure dynamic equation inside the pneumatic muscle during the filling and deflation process are established.Finally,the single joint dynamics models are combined to establish the system model.After the determination of the component and system technical parameters,the model is converted into a single-input single-output system according to the specific control amount and the system's mathematical relationship.The system state equation,which is used for subsequent controller design,is established after linearizing the established system.4)In order to realize passive rehabilitation training for patients,the method using the sliding mode variable structure control algorithm to complete the trajectory tracking of joint angle is proposed.With step response and sinusoidal signal as input,the simulation in Simulink verifies the excellent trajectory tracking performance of slide mode control.Aiming at the control quantity jitter problem of sliding mode controller,a fuzzy control method is combined to improve the system's dynamic performance.The system is proved to be robust to external parameter changes and disturbances through three different models.Finally,the function curve of the three joints is taken as input to verify that the accuracy and response of the controller's trajectory tracking of standard gait meets the control requirements from the three aspects of trajectory tracking,error and control quantity.