Equivalence of control signals in nonlinear adaptive controllers and an ´all-linear´ adaptive controller

The authors design three different adaptive controllers for the same second-order plant example. Two of the controllers are contemporary nonlinear adaptive controllers designed by the methods of Narendra and Valavani (1978); and Morse (1987); the third controller is an all-linear, constant coefficient adaptive controller designed by Johnson´s method (1985), which is based on disturbance-accommodating control (DAC) theory. Using computer simulation techniques, the authors demonstrate that the DAC all-linear adaptive controller produces control signals that are essentially equivalent to the control signals produced by the two nonlinear adaptive controllers. This equivalence is demonstrated over a range of uncertain plant parameter perturbations and external disturbances.<>