EXPERIMENTAL RESULTS ON ADAPTIVE NONLINEAR CONTROL AND INPUT PRESHAPING FOR MULTILINK FLEXIBLE MANIPULATORS

Adaptive input precompensators in conjunction with nonlinear controlle rs for multi-link flexible manipulators are considered in this paper. In an earlier paper, we had shown that application of a nonlinear inne r-loop control reduces the variations in frequencies due to the geomet rical configuration for multi-link flexible manipulators. This results in a better performance when input preshaping or any other controller based on a linear model is designed. To improve the performance of th e system to parameter variations (e.g. changes in payload), an adaptiv e version of the advocated controller is utilized. This is achieved by estimating the time of application of the impulses for on-line presha ping and in the case of payload uncertainty, estimation of the payload and real-time adjustment of the nonlinear inner-loop based controller . Frequency domain Time-Varying Transfer Function Estimate (TTFE) and Empirical Transfer Function Estimate (ETFE) system identification algo rithms are proposed for estimation of vibrational modes and unknown pa yload. Experimental results on a two-link flexible manipulator with ad aptive nonlinear control and preshaping are provided to show the effec tiveness of the advocated controllers. Overall, the present paper comp letely generalizes the adaptive input preshaping technique for multi-l ink flexible manipulators.