A Research On Driving And Control Technology Of Lower Extremity Exoskeleton Joint

As a nonlinear,multi-variable,high-coupling complex mechanical wear device,the lower extremity exoskeleton robot has an extremely wide range of research fields.Among them,joint drive and control technology provide power and control instructions for exoskeleton robots,which is undoubtedly an extremely important part of many research fields.It is only meaningful to discuss control techniques based on high-performance joint drive control systems.This thesis has studied these two aspects.In order for the lower extremity exoskeleton to exhibit excellent control quality,a high-performance joint drive system must be designed.In this thesis,the joint drive mode of permanent magnet synchronous motor is selected,and the direct torque control(Direct Torque Control,DTC)is the basic joint motor drive control strategy.Single joint motor drive design,introducing space vector pulse width modulation technology to avoid the limited voltage control vector in traditional DTC;In order to reduce the robustness caused by the change of system parameters,the resulting output ripple,the flux linkage and the torque loop adopt the super twisting sliding mode controller,which can fundamentally solve the sliding mode buffeting;In order to enhance the system's ability to resist external interference,the speed loop uses exponential sliding mode control;In order to improve the self-adaptive ability of the single joint motor,the position loop uses fuzzy control.The feasibility of the designed system method in the exoskeleton single joint drive control is proved by MATLAB simulation.Next,from the mathematical point of view,the lower extremity exoskeleton robot is analyzed and studied,and the kinematics and dynamics models are established.Kinematics modeling is expected to describe and study the motion characteristics of a robot from the perspective of spatial geometry.Using the Lagrangian dynamics modeling method,the mathematical correspondence between the trajectory of the lower extremity exoskeleton and the driving torque is studied from the perspective of dynamics.Finally,the control algorithm of the lower extremity exoskeleton robot is studied and designed.The designed control algorithm has high servo precision,strong resistance to external interference,and labor-saving features.Firstly,the exoskeleton PID control is introduced,and the influence of gravity compensation on control performance is analyzed.Then the calculated torque sliding mode control is introduced,and the online gravity compensation algorithm is combined to improve the servo accuracy and external interference resistance of the exoskeleton.Further,in order to achieve the effect of labor saving,the impedance sliding mode control is designed,which not only has high position servo precision,but also the human-machine interaction torque is obviously smaller than the actual joint driving torque,achieving the purpose of wearing labor-saving power and suppleness.Through MATLAB simulation comparison,the design control algorithm is very feasible in the lower extremity exoskeleton.