A robust flight control system design for a small-scale UAV helicopter

The aim of this paper is to design a robust automatic flight control system for a small-scale UAV helicopter. A nonlinear search based on differential evolution (DE) algorithm is conducted for a six degrees-of-freedom linear state-space model that matches the frequency-response data set. The accuracy of the identified model is verified by comparing the model-predicted responses with the responses collected during flight experiments. Based on the identified model, the H_∞ loop shaping method is used to design the inner-loop of the unmanned helicopter in order to satisfy the flight performance requirements specified in the military standard ADS-33E. The greatest common right divisor method is used to solve the difficulties in choosing a proper weighting matrix in the H_∞ loop-shaping procedure, compared with the traditional method, the system using the new method have a larger robust stability margin, the decoupling and the bandwidth of the system are also greatly improved. The simulation results prove high standard of the control performance of the unmanned helicopter system in accordance with ADS-33E.