Saturation Control for Reduction of Rotor Blade Lag Vibration

Within the context of this research, the performance of saturation control for reduction in the vibratory lag motion of helicopter rotor blades is investigated. The single-degree-of-freedom plant, which consists of a spring and damper attached to the rotor blade, is perturbed by an aerodynamic force, and produces the unwanted vibration. To restrict this vibration, the second-order controller is provided to couple with the blade system. It works adaptively, when the system is excited and the controller frequency is set at half of the blade lag frequency in accordance with the relationship of both natural frequencies. The nonlinear terms from the controller respond to the blade system. As a result, the system vibration diminishes, and also the system reaches a steady-state condition. The equation of motion from the plant, and the control law equation from the controller are nonhomogeneous second-order equations associated with quadratic nonlinearities. Both of them are coupled together. The approximate solution for these two equations is mathematically determined by a perturbation technique called the method of averaging. Finally, the equations of motion are utilized for assembling a simulation model to evaluate the solution, and to examine the efficiency of the system.