Research On Robust Control For Helicopter With Actuators Saturation

The helicopter is widely used in the military and civilian with its unique capability, such as vertical takeoff and landing, hovering and flight in an arbitrary direction. However, the helicopter is a multivariable system, and has some distinguishing features, such as static instability, nonlinearity and strong coupling, which make the designing of flight control system a challenge. Research on flight control of the helicopter has a broad application prospect and practical significance. We mainly studied the design of three attitudes controller and the anti-windup control for helicopter with actuators saturation in this paper.In the paper, the flight characters and nonlinear dynamic model of helicopter were firstly introduced, and the linearization of the model was analyzed. Analysis of stability and system response was also provided to the higher order linearization mathematical model of Black Hawk helicopter UH-60A. Before designing the control system, coprime factor model reduction theory was used to reduce the high order model of helicopter.Then, the double-loop flight control system of helicopter was devised, according to the thought of inner and outer loop and H_∞loop shaping. The inner loop mainly controlled the all helicopter attitudes including roll angle, pitch angle and yaw angle simultaneously, while the outer loop realized track of the velocity. The control system realized the decoupling of channels of the helicopter, showing the high bandwidth and robustness. Simulation results show that the flight quality was the 1st level, according to the ADS-33E standard.In the end, we discussed the anti-windup problem of the helicopter with actuators saturation, and studied the design method of the anti-windup controller. After introducing the definition of actuator saturation, we summarized two general design strategies of the anti-windup controllers and related technologies. Then the difficulties in designing anti-windup controller of the helicopter were pointed out. Then, we used the LMI method to design the anti-windup compensator of helicopter on the basis of the H_∞loop-shaping controller. Finally, we compared the changes of response between the system with and without the designed anti-windup compensator, when the output amplitude of the actuator was restricted. The simulation results showed that the designed anti-windup compensator could make the system reach to the desired performance requirements.