Feedback Control of a Hovercraft over a Wireless Link

Abstract

Nonlinear underactuated systems (i.e. systems with fewer control inputs than configuration variables) present significant challenges for automatic control. This thesis explores feedback control of an underactuated hovercraft over a wireless communication channel using techniques from nonlinear control theory. A family of control laws stabilizing the hovercraft <em>reduced dynamics</em> - including zero velocity, constant forward/reverse velocity, and constant angular velocity stabilization - are derived. Lyapunov arguments are used to prove convergence of the reduced dynamics under the control laws. It is shown that heading cannot be stabilized by a continuously differentiable state feedback law. In response, two hybrid control algorithms for heading stabilization are proposed. The control laws are demonstrated on a real R/C hovercraft using a distributed autopilot and a Bluetooth network. A two-dimensional aided INS is developed using a MEMs IMU and the "Cricket" RF/ultrasonic ranging system. Experimental and simulated results from a high-fidelity model are shown to agree nicely.