Performance Evaluation of a Helicopter Main Rotor Hydraulic Control System Using Rotor Equivalent Dynamic Parameters

Hydraulic control systems are commonly used in helicopter main rotor control applications because of the agility of the system and operational capability under heavy loads. It is significant to obtain better performance from hydraulic control system to ease the helicopter control under heavy loads. In this study, a complete helicopter main rotor hydraulic control system is modeled by using MATLAB/Simulink® to simulate system responses. Kinematic model of helicopter input is obtained. Hydraulic interface of a Flight Control Actuator is obtained. Pitch (α) and Roll (β) angle of stationary swashplate is obtained. Finally, 3 degrees of freedom rotor equivalent model is obtained. To enhance the overall dynamic performance of the system, a PI controller is developed and implemented to the system by an additional actuator. Furthermore, feedback system is modified to have a more stable controller by adding a feedback actuator, to give position of equivalent rotor mass as feedback to Flight Control Actuator. It is concluded that adding a PI controller is highly beneficial in terms of extending the controllable frequency range. Furthermore, modified feedback system is found to be extremely beneficial by decreasing amplitude and improving overall dynamic characteristics.