Position And Force Control For Underactuated Flexible Manipulator

The position/force control of manipulators has been widely concerned by scholars at home and abroad.The underactuated flexible manipulator,which has characteristics of light weight,flexibility and low energy consumption,has become a research hotspot in the field of manipulators.Considering the constrained end-effecter,unknown parameters,external disturbance and time delay,the paper put forward a robust adaptive control scheme based on improved sliding mode,aiming at the model of the flexible manipulator,the underactuated manipulator and the underactuated flexible manipulator model,respectively.Finally,the simulation results show the feasibility of the proposed method.In this paper,the dynamic model of flexible-link manipulator,the dynamic model of flexible-link manipulator with flexible joint and the dynamic model of the underactuated flexible manipulator are prposed respectively.Then,the simplified dynamic models are obtained using coordinate transformation to reduce dimension.Aiming at the position/force control of the constrained flexible-link manipulator,a robust controller based sliding mode is proposed to ensure the stability of the system,which can guarantee the position tracking error tends to zero and the force eeor is bounded.Then considering the influence of the model uncertainties and external disturbance,an adaptive control based on sliding mode is designed,which can effectively compensate the model uncertainties and external disturbance.Compared with the traditional linear sliding mode control,the method in this paper can guarantee the final force error convergence and improve the state tracking accuracy of the system.Considering the control of constrained flexible-link manipulator with flexible joint,an improved adaptive control strategy based on sliding mode is proposed for the reduced model,which can guarantee the asymptotic convergence of the position error and the force error.Then,for the flexible joint with unknown parameters,considering the finite time convergence theory,an adaptive controller based on backstepping method is designed.The controller can effectively compensate the uncertainty of model parameters and the influence of the flexible joint.And compared with the traditional sliding mode control,the control strategy can guarantee the asymptotic convergence of the position tracking error and force error in finite time.For the position/force control of underactuated manipulator,considering the influence of external disturbance,a robust control strategy based sliding mode is proposed,which can ensure that the position error of the system is asymptotically convergent and the force error is bounded.Then according to the influence of time delay,the time delay is approximately as a secondorder rational fraction form by Pade theorem.Concerding the infulence of uncertain model parameters for the underactuated flexible manipulator,a neural network adaptive control strategy is proposed,it can be proved that the designed controller can effectively compensate the uncertain model parameter,time delay and effect of flexible joint.Compared with the traditional method,this method can ensure the position error and force error asymptotic convergence.Finally,the feasibility of the above proposed control strategy is verified by the comparison of MATLAB simulation.