Research On Trajectory Tracking Control For Manipulator System Based On Iterative Learning Method

The manipulator system is nonlinear with strong coupling and time-varying between joints.It is not easy to obtain an accurate dynamic model of the manipulator system in actual situation.The iterative learning control is intelligent with mathematical description to solve problems with strong coupling,nonlinearity and motion repetitiveness.In this paper,some new iterative learning controllers are proposed for trajectory tracking of manipulators.The main research works can be described as follows:Firstly,the dynamic analysis of the manipulator system is proposed in this paper.And the dynamic model of manipulator system is established by using Lagrange methodSecondly,an adaptive iterative learning control(AILC)approach based on disturbance estimation has been developed for trajectory tracking of manipulators with uncertain parameters and external disturbances.The external disturbances are estimated by the iterative learning control whereas the uncertain parameters are compensated by adaptive control.This approach which based on the disturbance estimation technique provides a rapid convergence of trajectory tracking errors.According to the Lyapunov theory,the sufficient condition of the asymptotic stability has been developed for the two degree of freedoms(2-DOFs)manipulator system.The numerical results show that the AILC approach based on disturbance estimation is feasible and effective for the 2-DOFs manipulator system.A comparison of the AILC method and the ILC method is completed,which shows that the AILC method performs a faster convergence of the disturbance to the steady state.Finally,an iterative learning control approach without resetting condition based on accelerated inhibition effort is developed for trajectory tracking of manipulators.The initial state error is modified in a special time interval which can shrink with the increasing number of iterations.This approach provides a rapid convergence of trajectory tracking errors with the initial state value automatically in each iteration.According to the ? norm,the monotone convergence has been developed for the manipulator system.The numerical results show that the developed ILC approach is feasible and effective for the 2-DOFs manipulator system.