Adaptive disturbance accommodating controller for nonlinear stochastic systems

This paper presents the the formulation of an adaptive disturbance accommodating controller for nonlinear stochastic systems with unknown nonlinearities and external disturbances. The disturbance accommodating control scheme presented here utilizes an estimator to determine the corrections to the nominal control input required to minimizes the effects of both unknown system nonlinearities and external disturbances on the controlled system. Similar to the disturbance accommodating controller for linear systems, performance of the nonlinear disturbance accommodating controller depends on the accuracy of the assumed disturbance model. The proposed formulation indicates that an adaptive law can be developed for updating the process noise covariance matrix associated with the disturbance model online so that the controlled system is stable.