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Modeling the Dynamics of Planing Craft and Its Optimal Control in Acceleration Mode

Azizi Yengejeh, Morteza | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 47648 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Seif, Mohammad Saeed; Mehdigholi, Hamid
  7. Abstract:
  8. Properly adjusting the trim angle during the craft speed up will be extremely important in special cases as in sport competitions or military missions. In such applications, the goal of trim adjustment is to reach final speed in a minimum possible time which is an advantage to just passing the resistance hump. Present study tries to provide insight into how the concerned control variables such as angles of the drive system and trim tab of a planing craft should be changed during acceleration mode so as to minimize the time needed to reach the final speed. This is a time-optimal control problem. Optimal control theory has been used previously for the motion control of marine vessels in applications such as seakeeping, maneuvering and navigation. This study introduces a new application of this theory for increasing the craft speed performance.Theatrical methods besides empirical relations are used in the equations of motion for calculating aerodynamic, hydrodynamic, propulsion and control element forces on hull to develop a 3 DOF dynamic model for planing crafts in forward acceleration mode.To provide more evaluation of the dynamic model and understanding the nature of forces, the wetted area pattern and the interference effect in planing catamarans, a numerical study has been conducted and some of its results are presented in a separate chapter. Finally, the formulation and solution algorithm for time-optimal problem (by an indirect method based on Pontryagain Minimum Principle) are described and then, as two case studies, optimal solutions for a racing catamaran and a conventional planing monohull are presented in different control conditions. For catamaran, optimal control of thrust angle leads to 40% reduction in time to reach the speed of 110 kn and also 14% lower resistance at this speed in comparison with an uncontrolled case. Addition of a stability constraint for this problem changes optimal solution for drive angle and causes craft trim angle follow a decreasing trend at higher speeds.This increases the resistance and time needed to reach final speed. For monohull, the control problem has been solved in single-variable and dual-variable cases with two different LCGs. For this vessel, results show a simultaneity and similarity in trend between optimal control variables and hull trim angle. However the optimal signal is restricted by upper physical margin. Control law for each of the control variables in dual control variable case is very similar to single variable one
  9. Keywords:
  10. Catamaran Boat ; Aerodynamics ; Reacceleration ; Optimal Control ; Planning Boat ; Time Optimal Control ; Pontryagin Minimum Principle

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