H_∞ controller with feedforward for yacht course keeping

The autopilot for a yacht is difficulty to design due to its serious nonlinear and non minimum phase characteristics. The H ∞ control is a powerful control tool to deal with this problem. Specified the sensitivity and complementary sensitivity functions are a major difficult point in this method because the conflict of the targets. Feedforward control can solve this problem effectively. This paper introduces a mirror rejection method in feedforward control design to eliminate the influence of non minimum phase.