Reduced‐order implementation of disturbance observers for robust tracking of non‐linear systems

The disturbance‐observer‐based control (DOBC) is a well‐known robust control scheme and recently its non‐linear version has been developed. Observing that two components (so‐called Q‐filters) in the conventional DOBC structure have the same transfer function, the authors propose a reduced‐order DOBC for uncertain non‐linear systems. It is shown that the proposed controller also guarantees the same robust transient response as those developed before. Numerical simulations using a magnetic levitation system are included to illustrate the detailed design procedure and validate the performance of the proposed controller.