Force tracking system using a semi-active valve lag damper for vibration reduction in helicopters

This paper considers a closed-loop force tracking system for an active valve lag damper intended for vibration reduction applications in helicopters. The mathematical model of the damper is treated in a simplified form and is the basis for controller design. Due to the inherent nonlinearity of the damper, a controller is constructed using concepts from nonlinear control, namely, nonlinear dynamic inversion (NDI). Tuning methods according to several frequency-domain requirements are introduced and a realistic simulation example demonstrates the effectiveness of the controller.