Abstract
A large number of small-size helicopters are widely used for some industrial works. This study deals with a problem of a transportation system of the helicopters which carry a load by suspending a load. Dynamics of the small-size helicopters is fast and sensitive in comparison with normal large-scale helicopters and tends to be unstable to disturbances. The transportation system needs a vibration control of the slung load. The purpose of our study is to suppress the vibration of the slung load during hovering. To simplify the control system, we assume that it is possible to measure only the angle of the slung load by potentiometer. Since the helicopter with slung load system is nonlinear and constrained system in three dimensional space, it is difficult to design a state estimator. Therefore we adopt output delayed feedback control to suppress the vibration of the slung load. A limitation of the delayed feedback control is that the theoretically control design method is not established. We tried to determine the delayed feedback control parameters theoretically by using a linearized model and system parameters identified by the frequency response test. To verify the effectiveness of the present vibration control method, we implemented flight tests with a small-size helicopter with slung load system. Consequently, the control parameters are nearly identical to the parameter determined by trial-and-error in the experiments.
