Helicopter Gust Alleviation; An Optimal Sampled-Data Approach

Helicopter ride quality is largely determined by the vibration level in the fuselage and the sensitivity of the fuselage to gust disturbances. Considerable progress has been made over the years in reducing gust sensitivity and vibration level through improved mechanical and aerodynamic design. These approaches, however, are static in the sense that they cannot adapt to changing flight conditions. An alternate means of achieving gust alleviation and vibration reduction is through active control of the helicopter rotor blade pitch. Sikorsky Aircraft in conjunction with United Technologies Research Center, has investigated the application of modern control techniques to gust alleviation and vibration reduction under NASA Contract NAS2-10121. This paper describes the design of the gust alleviation controller. The control configuration consists of an optimal sampled-data digital controller coupled with an optimal one-step-ahead predictor. A sampled-data approach for the control was chosen to facilitate future implementation with an on-board digital computer. The predictor permits an estimate of the unmeasured gust disturbance magnitude to minimize gust effects on the helicopter fuselage.