Application of Multivariable Control Theory to Improve Steering and Propulsion Control of a Containership
Youhanaie, Mark
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https://hdl.handle.net/2142/70128
Description
Title
Application of Multivariable Control Theory to Improve Steering and Propulsion Control of a Containership
Author(s)
Youhanaie, Mark
Issue Date
1984
Department of Study
Mechanical Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Mechanical
Abstract
Motivated by economic and safety considerations, the ship propulsion and steering control problems are considered for the SL-7 containership. Extending previous work by Reid in the area of minimum-added-resistance steering control, modern multivariable control methods are applied to the steady-state coursekeeping control problem. Specifically, the full loop-transfer recovery procedure of Doyle and Stein is applied to provide acceptable stability margins at the plant input. Also, using robustness analysis and a numerically determined uncertainty bound, it is shown that the maximum allowable uncertainty in the ship hydrodynamic coefficients before a potential for closed loop instability exists is 6.5 percent. The multivariable propulsion/steering control problem is considered including the effect of a varying wake fraction. A new minimum mean fuel rate performance index is derived, but little improvement in propulsion economy is achieved compared to minimum-added-resistance steering control, as the steering induced losses constitute over 95 percent of the increased mean fuel rate. Analysis of multivariable stability margins reveals, however, very small stability margins when a decoupled control approach is used in the presence of the varying wake fraction. The benefit of employing the multivariable controller is therefore, that acceptable multivariable stability margins are achieved.
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