The Reserch Of Wheel-legged Lower Limb Exoskeleton Control System

Lower limb booster exoskeleton,composed of external skeletal frame,usually refers to a kind of mechanical and electrical system which can be wore on people.As a booster application,it can be applied to enhance the human body's functions of relieving load and fatigue while carrying weight.However,most of the booster exoskeletons only can boost walking with a low speed.Therefore,in this paper,with the support of the National Defense Science and Technology Innovation Special Zone project,combined with the characteristics of wheeled robot and lower extremity exoskeleton,a wheel-leg external bone control system is proposed,and a reasonable control algorithm is designed,which can realize the functions of helping walking and wheeled fast marching.Firstly,this paper introduces the frame of the wheel-legged lower limb exoskeleton and the structure of the wheel hub of the lightweight drive wheel.For the walking systems,Based on the analysis of the walking gait of the human body,combining with Lagrange equation,the dynamic model of the systematic walking and of the human-machine coupling is established.It also models and analyzes the double set cable transmission system and its internal joint friction.For the wheeled system,a slop motion and a flat motion model were established.Secondly,according to the requirements of the wheel-legged lower limb exoskeleton,a reasonable control experiment platform is set up,which includes the systematic hardware circuit design and debugging and the upper computer monitoring software programming,which provides a carrier for the realization of the control function of the lower limb exoskeleton.Then,corresponding control algorithm is designed respectively for the wheeled mode and walking mode of the wheel-legged lower limb exoskeleton.While a closed-loop differential control algorithm is designed for wheeled mode,a hybrid control algorithm based on gait,including fuzzy PD control algorithm at doublelegged support stage and impedance control algorithm at one-legged support stage,is designed for walking mode,and the stability analysis of the two algorithms is proved by using Lyapunov function.Finally,two kinds of motion modes of the wheel-legged lower limb exoskeleton are verified experimentally,and the identification of the system's internal joint friction parameter and the gait recognition experiment based on the foot force are designed.In this case,further experimentally evaluate the effect of boosting walking,analyze the result.,and verify the rationality of the hybrid control algorithm.For the wheeled mode,the motion controlled experiments on the flat field and slope are carried out,so as to verify the feasibility of wheel algorithm and meet the expected requirements.