Research on Control Schemes for Dynamic Positioning of Surface Ships.pdf

1、In control theory, there are many different control methods of which some of them havebeen proposed for DP system.Alternatively, we have witnessed in some literatures, thecombination of two or more control techniques to

2、form an enhanced controller for DP system.Likewise, this thesis presents research on control schemes for dynamic positioning of surfaceships.The emphasis of this thesis is to design and propose various control schemes fo

3、r DPsystem.Firstly, we propose a high-gain observer control scheme for DP system.The key aim isto design a high-gain observer for estimation of unmeasured states (velocity) and eliminate theconstant known disturbances.Eq

4、ually, we design an output feedback controller based on thehigh-gain observer for dynamic position system.The nain theme is to design feedback controllaw that can force the ship to its desired position and heading.Vector

5、ial backstepping techniqueis employed to derive an output feedback control law.The output feedback controller utilizesestimated states from the high-gain observer for feedback.Simultaneously, an adaptive law isderived to

6、 estimate the unknown constant disturbances.Finally, the global uniformly asymptoticstability (GUAS) performance is guaranteed.
　　Secondly, a Relaxed LMI Stability based fuzzy controller for DP system of surface ships

7、 isproposed.Takagi-Sugeno (T-S) fuzzy model is applied to formulate the ship's mathematicalmodel into the fuzzy model.Then, we employ parallel distributed compensation (PDC) designtechnique to formulate the fuzzy rules.R

8、elaxed LMI and decay rate stability conditions are usedto derive the stability of the resulting fuzzy controller.Linear matrix inequality (LMI) solver isused to compute a positive definite matrix and control gains that s

9、tabilize the fuzzy controller.
　　Thirdly, a design of a robust fuzzy controller and the robust observer is presented.Itassumes two cases: case one considers when the states are available for measurements and theenviro

10、nmental disturbances are unknown but bound with the upper limit.Thus, the design of arobust fuzzy controller using H∞ attenuation design method is given.The role of H∞ attenuationmethod in the fuzzy controller is to abol

11、ish the disturbance to a prescribed minimum level.Thesecond case assumes that the state variables are not known for measurements.Hence, robustfuzzy observer is design to estimate the unavailable states.Then, optimal H∞ a

12、ttenuationmethod is utilized in the first case.Applying the LMI stability conditions and Lyapunov stabilitytheory, the stability of the controller can be guaranteed.In addition, both cases prove theuniformly upper bound

13、(UUB) and the performance of H∞ control can be guaranteed.
　　Lastly, simulations for each proposed control scheme are carried out, and simulation resultsare given.Obtained results demonstrate the performance and valid