Conclusions and Perspectives
This monograph has concentrated on the control of underactuated ocean vessels including ships and underwater vehicles. These vessels have more degrees of freedom to be controlled than the number of independent control inputs. Ships do not have an independent sway actuator while for underwater vehicles there are no independent sway and heave actuators. The book started with a review of the necessary background on ocean vessel dynamics and nonlinear control theory. The authors then demonstrated a systematic approach based on various nontrivial coordinate transformations together with advanced nonlinear control design methodologies founded on the basis of Lyapunov’s direct method, backstepping, and parameter projection techniques for the development and analysis of a number of ocean vessel control systems to achieve advanced motion control tasks. These tasks include stabilization, trajectory-tracking, path-tracking, and path-following. The book has offered new knowledge regarding the nonlinear control of underactuated ocean vessels, efficient controllers for practical control of underactuated ocean vessels, and general methods and strategies to solve nonlinear control problems of other underactuated systems, including underactuated land and aerial vehicles. Numerical simulations and real-time implementations of the designed control systems on a scaled model ship have been included to illustrate the effectiveness and practical guidance of the control systems developed in the book. As an illustration of the constructive feature of the book, the observer design, control design, and stability analysis techniques developed for underactuated ocean vessels have been applied to control of other underactuated mechanical systems including mobile robots and VTOL aircraft.
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