Mixed H₂/H_∞ based Course-following Control for a Small Low Cost Autonomous Boat

Zhenyu Yu, Xinping Bao, Kenzo Nonami

Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba, Japan

http://mec2.tm.chiba-u.jp/~nonami/

Abstract

This paper presents the design of course-following controller for an autonomous boat with low-cost sensors by applying H2/H∞ robust control approach. At first a mathematical model for the under actuated boat is derived which captures the dynamics between rudder deflection and the boat’s horizontal motion. The resulted model could be seen as an extension to the Nomoto’s model. Despite of its simplicity, the model offers the advantage that no compass is required for control, which promotes integrated steering and guidance at low cost. Based on the model, mixed H2/H∞ control approach is applied to provide robust stability in the presence of model uncertainty and environmental disturbance while maximizing the performance in the sense of H2 norm. The proposed modelling and control strategies are tested on a small autonomous boat whose length is about 1 meter. A low-cost GPS receiver and a gyroscope are used for navigation and control. The course-following performance has been demonstrated at sea trials. The standard deviation of the cross track error is 2.3 m which is a good result for the small boat with such low cost sensors.

 Keywords: Autonomous boat, Course-following control, Mixed H₂/H_∞, Modelling, Low cost.

(P1110728001, 1.15 MB),  Sample Video Film 7.7 MB

Biographies:

	Zhenyu Yu received his BS degree in Electronics and Communication Engineering from Beijing Information Technology Institute, China, in 1997, and his M.S.E degree in Electronics and Mechanical Engineering from Chiba University, Japan, in 2005. He is currently on his PhD course study in Chiba University. His research interests include robotics, autonomous vehicles, robust control theory and applications.
	Xinping Bao was born in Shandong, China. He received the Master degree in Mechanical Manufacture and Automation from XIDIAN University, China, in 2004. Currently, he is in his first year PhD study in graduate school of engineering at Chiba University, Japan. His research interests include hydrodynamics, nonlinear control, and intelligent control.
	Dr. Kenzo Nonami received MS degree and Ph.D. degree in Mechanical Engineering in 1976 and 1979 respectively, from Tokyo Metropolitan University. He joined Chiba University in 1979 as a Research Associate, Associate Professor from 1988 to 1994. Since 1994, he has been a full professor in Department of Mechanical Engineering and Department of Electronics and Mechanical Engineering at Chiba University. In 2004, Dr. Kenzo Nonami was a vice dean of faculty of engineering. Also, he has carried out a research in NASA in USA during two years from 1985 to 1988. His recent research interests are Land mine detection robots with multi-functional arm, Walking machines, Master slave manipulator and hand systems, Fully autonomous unmanned small-scale helicopter, Micro air vehicle, Quad tilt wing unmanned aerial vehicle, Unmanned autonomous boats, Energy storage flywheel by Active magnetic bearing system, Robust and nonlinear control, Control applications.

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