Robust digital gain-scheduling control of the UAV altitude

Design of the small unmanned aerial vehicle altitude-hold autopilot for the entire flight envelope on a basis of the robust gain-scheduling control is considered. As far as flights are performed within restricted altitude range, the entries of the matrices of the state-space unmanned aerial vehicle model are assumed to be functions of the true air speed only. So the real time true air speed measurement by airborne air data system is used for gain-scheduling of the altitude control system. The gain scheduled static output feedback was applied as the simplest implementation of altitude control system for unmanned aerial vehicle. For numerical implementation of the design procedure, the mathematical model of the Aerosonde flight dynamics was used as the test-bed. The full range of true air speed for the Aerosonde flight envelope was divided by 6 sub-ranges. The static output feedback parameters for each sub-range were determined by linear matrix inequalities approach for discrete systems, which produces the suboptimal robust controller. Continuous gain-scheduling of the static output feedback gains was achieved by usage of simple Lagrange interpolation between true air speed sub-ranges. The efficiency of this approach was proved by simulation of the control processes in Simulink.