This article describes the practical application of a vibration control technique, developed by the authors and known as the receptance method, to the AgustaWestland W30 helicopter airframe in the vibration test house at Yeovil. The experimental work was carried out over a total of 5 days in two visits to the Yeovil site during February and March 2011. In the experiments, existing electro-hydraulic actuators were used; they were built into the airframe structure and originally designed for vibration suppression by the methodology known as active control of structural response developed at the AgustaWestland Helicopters site in Yeovil. Accelerometers were placed at a large number of points around the airframe and an initial open-loop modal test was carried out. In a subsequent test, at higher actuator input voltage, considerable non-linearity was discovered, to the extent that the ordering of certain modes had changed. The vibration modes were, in general, heavily damped. Control was implemented using measured frequency response functions obtained at the higher input level. After acquiring the necessary measurements, simulations were carried out and the controller was implemented using MATLAB/Simulink and dSPACE. The closed-loop poles were mostly assigned with small real parts so that the system would be lightly damped and sharp peaks would be clearly apparent in the measured closed-loop frequency response functions. Locations of the open- and closed-loop poles in the complex s-plane were obtained to verify that the required assignment of poles had taken place.
On-Line Identification of Open-Loop Frequency Response and Two-Degree-of-Freedom Design Method of PID Control Systems
