Parameter estimation error based robust adaptive law design and experiments

To address the sluggish parameter estimation and control performance of conventional adaptive control methods, this paper presents a new robust adaptive law based on the parameter estimation error. The information of parameter estimation error is first derived via filter operations, which is used as a new leakage term in the adaptive law design. The proposed adaptive law is further incorporated into the adaptive control system, which can retain exponential convergence of the tracking control error and the parameter estimation simultaneously. Moreover, comparisons to other classical adaptive laws are provided with respect to the parameter estimation convergence and robustness property. A simple and intuitive approach to online test the required persistent excitation (PE) condition is suggested. Simulation and experimental results based on a small 3 DOF-helicopter show that the newly suggested adaptive method can achieve better control and estimation performance than other conventional adaptive schemes.