Pulse Width Modulation of Water Jet Propulsion Systems Using High-Speed Coanda-Effect Valves

Abstract

An integrated high-speed valve switching and pump output control scheme are developed for precision maneuvering of underwater vehicles. High-speed Coanda-effect valves combined with a centrifugal pump allow for precise control of thrust force using a unique pulse width modulation (PWM) control scheme, where both pulse width and pulse height are controlled in a coordinated manner. Dead zones and other complex nonlinear dynamics of traditional propeller thrusters and water jet pumps are avoided with use of the integrated pump-valve control. Three control algorithms for coordinating valve switching and pump output are presented. A simplified nonlinear hydrodynamic model of underwater vehicles is constructed, and design trade-offs between PWM frequency and pulse height, with regard to steady state oscillations, are addressed. The control algorithms are implemented on a prototype underwater vehicle and the theoretical results are verified through experiments.