An Adaptive Robust Nonlinear Motion Controller Combined With Disturbance Observer

Parameter adaptation and disturbance observer (DOB) have been considered as two contrastively different approaches to handle uncertainties in motion control problems. The purpose of this brief is to merge both techniques into one control design with theoretically guaranteed performance. It is shown that the DOB compensates low-passed components of the lumped uncertainties without the necessity of parameterization, whereas the adaptive mechanism is only automatically activated in the cases where the fast-changing components of the uncertainties beyond the pass-band of the DOB can be parameterized by unknown parameters. It is thus shown theoretically how the DOB and adaptive mechanism play in a cooperative way so that the controller is more effective than the individual ones. Simulation results are provided to support the theoretical results.