Reliable Control Method Research Of The Omnidirectional Rehabilitative Training Walker

Due to the serious aging population problem, patients suffering from physical injury andwalking disorders increased year by year, the development of omnidirectional rehabilitativetraining walker is very necessary. However, the actuator motors may lose their effectivenessduring the actual applications for the walker. The walker cannot trace the designated routesand the trainer’s safety is affected. Therefore, the safety problem of the walker needs to besolved. Meanwhile in application, the system controller needs to consider the problem ofcontrol constraint owing to the physical limit.In view of this situation, based on the redundant degrees of freedom theory, theexpression of the reliable controller with force constraints is derived by using the method offault tolerant control. When a certain actuator malfunctioned, the controller can achieve thestable trajectory tracking tasks of the walker, and the input force constraints in the range ofactuator control force. The specific contents of reliable control for the omnidirectionalrehabilitative training walker are as follows:First of all, based on the structure of the omnidirectional rehabilitative training walkerwith regard for centre-of-gravity shift, by constructing the Lyapunov function, the errorstracking system asymptotic stability is ensured in global coordinate system and expression ofthe fault tolerant controller is derived. The simulation confirms the stable tracking of thewalker.Secondly, in order to ensure the input force meets the actual requirements, the problem offorce constraints needs to be solved. Hyperbolic tangent function is developed in order todesigning the controller with force constraints. The simulation result demonstrates theeffectiveness of the force constraints.Considering the various forms of actuator fault, including the actuator stuck,actuator constant gain variations, actuator failures of constant deviation. By separating thefault actuators, the fault model of omnidirectional rehabilitative training walker is derived andthe asymptotic stability is ensured by LMI. The walker with reliable controller can achieve thetrajectory tracking in several kinds of fault type conditions.