Position And Force Control For Coordinated Multiple Flexible Joint Manipulators

The position/force control of manipulators has been widely concerned by scholars at home and abroad.How to obtain high precision position/force tracking is the research hotspot in this field.The paper addresses the issue of the flexible joint single manipulators and multi manipulator model,considering the constrained end-effecter,unknown parameters,interference,time delay,hysteresis input,put forward a robust adaptive control scheme based on improved sliding mode.Finally,the simulation results show the feasibility of the proposed method.The constrained single manipulator dynamics multi manipulator dynamics model,constrained multi manipulator dynamics are proposed respectively for the flexible joint manipulator system.And a coordinate transformation is introduce to simplify the model and reducing dimensions,finally out of the force after the decoupling dynamic equations of the robot arm.Finally,the decoupling dynamic model can be obtained.For the flexible single manipulator system,firstly,an adaptive controller based on linear sliding mode is designed to ensure the stability of the system.Then,considering the influence of the time delay,and the delay is approximately as the first order by using Taylor expansion.Secondly,the improved sliding mode is proposed by adding force error is to the sliding mode control to solve the problem that general linear sliding mode cannot guarantee the position and force asymptotic convergence.Then a robust adaptive controller based on the improved sliding mode is proposed.The controll strategy can compensate the uncertain parameters of the model.At the same time,the time delay and the flexible joint are also suppressed,and the position error,force error are also converged.For the cooperative control of multiple manipulators,firstly,a simplified dynamic model is considered,and an adaptive strategy based on linear sliding mode is proposed.Then the time delay is approximated as a second-order rational fraction by Pade theorem and is compensated,a neural network adaptive strategy is designed by using the improved sliding mode for the uncertain parameters.By Lyapunov theorem,the proposed control scheme can effectively compensate the influence of the time delay and the flexible joint,and the position error,the force error are also converged at the same time.For the constrained multi manipulator position/ orce control,firstly,an adaptive controller is designed for the reduced dimension dynamic model.Then,the system input hysteresis characteristics is espressed by a first-order differential equation.Similar to the control method used in single manipulator system,consider unknown parameters and external disturbance,a robust adaptive controller is designed,then,based on Lyapunov theorem,it is proved that the control scheme can compensate the hysteresis input,and the position error,force error can also asymptotic convergenc,the internal force error are also bounded at the same time.Finally,the validity of the proposed strategy is verified by simulation.