H_∞ controller design of an ostraciiform swimming fish robot

Abstract

In this paper, proposed is a design of a robust controller for a fish robot. A simple third order model is used to develop the feedback controller. With proper weighting functions augmented for loop shaping, a robust controller is obtained using H-infinity control methodology. Frequency analysis shows that the proposed controller is very robust, having gain margin of 17.3 dB and phase margin of 44.8 degrees, respectively. The stability robustness and performance analysis is done using step input and uncertainties of damping, and natural frequency. The step disturbance and measurement noises are also considered. The simulation results show that the proposed controller keeps the stability and performance even though there are a little degradation of them as uncertainties increase. The experimental result also demonstrates that the controller works well in a real fish robot. Thus it is expected that the proposed controller can be used effectively in real environment with model uncertainties and disturbances.