On some key issues in the windsurfer approach to adaptive robust control

We examine a number of crucial questions that arise in the windsurfer approach to adaptive robust control. Considerations are limited to the case where the plant is stable and has no zeros on the imaginary axis. The key conclusion is that, given a strictly proper stable model of a strictly proper stable plant, we can improve the performance robustness of the closed-loop system through the windsurfer approach if the plant and the existing model have no unstable zeros within the designed closed-loop bandwidth and if the deterioration in performance robustness caused by increasing the closed-loop bandwidth results in a sufficiently high signal-to-noise ratio for a certain closed-loop output error. Situations that may cause the iterative identification and control design process to terminate prematurely are identified. A simulation example is used to illustrate the results discussed.