VSTOL aircraft flight control system design using H∞ controllers and a switching strategy

The problem of designing controllers for plants with widely varying dynamics over the required operating envelopes is addressed. The plant investigated is a generic VSTOL aircraft model. The approach taken is to switch between linear controllers designed on linearizations of the nonlinear model. The linear designs make use of an open-loop singular value shaping technique which optimizes the system robustness to perturbations of the normalized coprime factors of the plant. Switching between controllers is achieved using a technique which enables smooth transition between controllers. It is concluded that the proposed loop-shaping approach produces robust closed-loops, giving the necessary performance capability