Evolution of a heave control system for an amphibious hovercraft

A heave control system for amphibious hovercraft was designed and tested. The central element in the system being an axial flow, lift fan whose blade angles are continuously varied by means of feedback signals from a pressure transducer located in the front end of the hovercraft cushion and from an accelerometer measuring the heave acceleration are discussed. Results from experiments, conducted on the Cranfield Whirling-Arm facility, have shown that the system provides a rapid and effective means of controlling the heave acceleration, and, in addition, produces a valuable reduction in craft drag whilst traversing waves. An extensive parameter identification program, using a nonlinear optimization algorithm, was constructed and applied to the control subsystem, such that a full mathematical model of the controlled craft was obtained. This was then used to design an optimum control with particular reference to passenger ride comfort.