| Summary: | 碩士 === 國立海洋大學 === 導航與通訊系碩士班 === 91 === Exact mathematical model description of ship maneuvering is known to be difficult due to ever changing sea states and variations in ship operation condition. To comply with availability of controller design tools and for ease of implementation, a much simplified ship model is usually adopted in the autopilot design. Consequently, the autopilot must possess certain robustness properties to be of practical use. In this work, the internal model control (IMC) method is incorporated with the sliding mode control (SMC) method to form the sliding internal model control (SIMC) method. This will eliminate the undesirable chattering behavior inherent with the sliding mode method, while maintaining the robustness properties. Consequently, the undesirable slew rate limitation (SRL) nonlinear behaviors and unnecessary wear of steering machining caused by chattering can be avoided. The proposed controller is characterized by switching between two controllers is based on a generalized error function that describes the zone of convergence. Numerical simulations indicate that tracking of both the sinusoidal reference heading angle and yaw rate functions are achieved with much improved chattering behavior in the presence of wave disturbances.
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