Application of Multivariable Control Theory to Improve Steering and Propulsion Control of a Containership

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Youhanaie, Mark

• Engineering, Mechanical

Identifier

(UMI)AAI8502352

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/70128