| Summary: | 碩士 === 國立臺灣大學 === 造船及海洋工程學研究所 === 87 === Owing to the modeling errors, parameter uncertainty and nonlinearity in the dynamics of the autonomous underwater vehicles (AUV) and the uncertainty of its operational environment, we need a robust and stable controller to have good control performance. The development of fuzzy logic control (FLC) in the form of sliding mode (SM) has been shown to provide robustness to the AUV autopilot design. In this thesis, a new method in designing membership functions of sliding mode fuzzy logic control (SMFLC) is presented. The method allows a novice to construct a set of membership, called shrinking-span membership functions (SSMFs) and dilating-span membership functions (DSMFs). Membership functions can be tuned systematically by using only two parameters instead of numerous parameters. The SSMFs and DSMFs have different spans for various term set elements in the universe of discourse and this gives the FLC more power to deal with the nonlinearity of the control problems encountered in real applications, even not having enough domain knowledge about the process.
To implement the control method, we first identify the dynamics of the AUV hull using planar motion mechanism (PMM). Then we identify the actuator dynamics including thruster nonlinearity from PMM model and free running experiments. The identified model was used to verify the control strategy by computer simulations. A series of experiments were then conducted. The results of this thesis show that SMFLC is quite satisfactory for the AUV orientation control and line of sight (LOS) tracking performance both in simulation and experiment results. The influence of disturbances, modeling errors, parameter uncertainty and thruster nonlinearity can be effectively compensated, even for complex maneuvering and operational environment.
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