Research On Tracking Control Of Manipulator Based On Impedance Control

In recent years,manipulators have been widely used in parts of grinding,cargo handling,medical rehabilitation and other fields.At the same time,with the rapid development of science and technology,the tasks of manipulators are becoming more and more difficult.Simple position control can't meet the control requirement for the manipulators with the harsh external environment.Considering the environmental contact force is necessary when the manipulators interact with the open external environment.Because excessive contact force is easy to damage the manipulators or bring physical injury to the operators,and light contact force can't meet the control requirement.Therefore,the manipulators need to have compliance characteristics with conduct operation.One of the important compliance control methods is impedance control.How to improve the compliance of manipulators under the intervention of system modeling error and external disturbances is very important for the intelligent development of manipulators.Therefore,this thesis studies the tracking control for manipulator based on impedance control.The main work is summarized as follows:(1)Considering the dynamics model and joint friction of manipulator are unknown,an impedance control based on adaptive neural network is proposed with the contact operation for the manipulator.Using radial basis function neural network(RBFNN)compensates the unknow item,and the stability condition of adaptive neural network impedance controller in four cases are analyzed.Then,using particle swarm optimization(PSO)obtains the optimal impedance parameters to ameliorate the tracking control effect of the controller.Finally,through the simulation example,the designed controller is verified to be effective.(2)An impedance control method based on disturbance observer is proposed for manipulator system with unknown disturbances.For tracking the second order impedance dynamic model,the composite control strategy is designed,which includes disturbance observer(DOB),the impedance controller and the position controller.They are used to estimate the unknown disturbances,correct input angle,and track the adjusted angle respectively.At the same time,considering the dynamic model of manipulator is not completely known,using RBFNN estimates the uncertainties of the system.This control strategy ensures the impedance error can converge to a small neighborhood.The desired dynamic tracking of the order impedance model is realized.Finally,the above control method is verified by a simulation example,which proves that is effective.(3)To solve the problem of slow convergence of manipulator's tracking control,the adaptive non-singular terminal sliding mode impedance control for manipulator system is proposed.The chattering phenomenon of the system reduced by exponential reaching law.First,we set the impedance system parameters to estimate the external environment,making the external environment contact force into the impedance traceable trajectory.Nonsingular terminal sliding mode controller is devised to track the motion trajectory.At the same time,considering the dynamic model of manipulator is not completely known,using RBFNN estimates the uncertainties of the system.Finally,the designed controller is verified to be effective by simulation example.