The influence mechanism of transmission stiffness on mechanical resonance of aircraft rudder servo system

Abstract Regarding the mechanical resonance problem caused by the coupling of flexible characteristics and transmission stiffness, this typical problem is faced by aircraft rudder servo systems under the requirement of lightweight design. A model of the aircraft rudder servo system considering flexible coupling links is established, and the influence of transmission stiffness on the open-loop transfer function of the rudder servo system is analyzed. Increasing the transmission stiffness increases both the anti-resonance frequency and the resonance frequency of the rudder servo system, and the system performance changes depending on the change in open-loop gain margin. When the load-motor rotational inertia and product are small, and the resonant frequency is still much lower than the natural frequency of the current loop after increasing the transmission stiffness, the system open-loop gain margin will decrease and mechanical resonance will intensify. When the load-motor rotational inertia and product are relatively large, increasing the transmission stiffness to make the resonant frequency close to or even greater than the natural frequency of the current loop will increase the system’s open-loop gain margin and weaken mechanical resonance. The correctness of the research conclusion was verified through system simulation and experimental validation.