Passive Fault-Tolerant Flight Control Design Example for Elevator Efficiency Reduction Using Structured H∞ Control

This paper presents a design example of structured H∞ control-based passive Fault-Tolerant Flight Control (FTFC) for the longitudinal motion of a research airplane MuPAL-α, and also presents the results of Hardware-In-the-Loop Simulation (HILS) tests using the actual MuPAL- α. The FTFC comprising PID and feedforward gains is designed using hinfstruct command implemented in MATLAB
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for the linearized longitudinal airplane motion model combined with a Linear Time-Invariant Parameter-Dependent (LTIPD) system representing the modeling errors of the onboard actuator and a Linear Parameter-Varying (LPV) system representing the possible actuator efficiency reduction. As hinfstruct command cannot handle parameter-dependent systems directly, we adopt two-step design, viz., we first obtain controller gain candidates which are common for multiple Linear Time-Invariant (LTI) models selected from the combined system comprising the longitudinal motion model, the LTIPD system and the LPV system with specifically fixed parameter values, and we then analyze the actual performance using the combined system via Linear Matrix Inequalities (LMIs) under the supposed parameter variation rate bounds.