Research on nonlinear hysteresis of the flight control system

The aircraft is required to have the ability of precise control and flight stability. Previous investigations about the flight control system (FCS) of a certain type aircraft have shown that the recorded data of the FCS has obvious nonlinear hysteresis between the station of the control column and the deflection angle of the elevator, which may lead to the risk of flight instability. This study set out to solve this nonlinear hysteresis problem of the FCS. The most obvious finding to emerge from this study is that the changes of the pressure altitude (PA) are determined as the root cause of the nonlinear hysteresis. The detail origin analysis is explained in this paper. The second major finding is that the comparison results of multiple models support the idea that the adaptive neuro fuzzy inference system (ANFIS) model is most suitable to build the hysteresis model of the elevator control system (ECS). Based on this model, a fuzzy compensation controller is designed to eliminate the nonlinear hysteresis of the FCS and realize the linear control of the ECS. The results of this study indicate that the addition of the compensator will improve the ability of aircraft precise control and realize the stable flight of the aircraft.