LAUSR

This brief proposes a tuning methodology for proportional-resonant (PR) controllers by using the design philosophy of the Ziegler–Nichols forced oscillation method. Unlike such related methods that are usual for proportional–integral–differential design, and those that have been recently proposed for PR controllers, the method in this brief is not restricted to plants whose Nyquist diagram crosses the negative real axis. It involves a feedback experiment with an adjustable phase relay, which allows the identification of the most appropriate point of the frequency response for each class of plants. The proposed method, which also includes tuning formulas that provide appropriate stability margins for each class of plants, is analyzed in detail for three examples, showing its wide applicability.