Ship Heading Fuzzy Adaptive Control Study

This thesis is based on the science project "The Research of Integration Intelligent Control in Autopilot Design for Marine ship" ,which applied from Shanghai high Education Scientific and Technology Foundation.The maneuvering of a ship along a proscribed course in restrict waters is important from operational, safety and environmental viewpoints. During the ship maneuvering, there are some characteristics of nonlinear, slow time varying and influence of complex disturbance.The PID autopilot . based on linear system math model is hard to control ship maneuver system effectively .For PID control does not has a good active properties and it also deeply depend on precise math model. Fuzzy controller shows promise for these non-linear systems that are not known well or the model is difficult to be identified. Some people try to use fuzzy logic controller autopilot to improve the control properties of the heading control and they got better results such as enhancing the system robust property and much rapid system response. However, pure fuzzy controller relies on the rules derived from past experience of experts or operators to realize fuzzy reasoning which are usually expressed in IF-THEN sentences. This system controls just like a P-D controller. It cannot erase system steady-state derivation. While PID controller always has a precise property in stable state.In this thesis, author puts forward a fuzzy self-turning PID parameters autopilot. This control system uses fuzzy controller to regulate the PID controller' parameters in real-time.To test the new autopilot performance, author designs a simulation program by MATLAB/SIMULINK. In the simulation process, author makes comparisons among three systems-the PID autopilot, fuzzy control autopilot and the fuzzy self-turning PID parameters autopilot. In this stage, author gives some step signals to simulate heading orders given to three systems without any interruption. And then give high frequency signals and low frequency signals to the system separately. Those signals are simulate the wave and current disturbance. After comparing the response curve, the result shows that fuzzy self-turningPID parameters autopilot owns the best properties among three autopilots. Simulate results illustrate the new autopilot design is reasonable. According the result author concludes that the autopilot gain both of the two control systems' advantage, it owns PID controller' s high precision in stable state and also has rapid response property. System's robust properties are also enhanced.Of course there are some aspects of this system need to be improved in the later study. For example, it is hard to get the three parameters domain of the fuzzy self-turning PID parameters autopilot. The distribution of the membership functions in the domain is based on the supposing. There still no effective method to determine the best domain's parameters. All these questions determine the further study direction in this field.Written by Xiaoming Liu directed by Professor Minzhong Bao...