en Ship Hydrodynamic مقاله پژوهشي Research Paper <div style="text-align: justify;"><span style="font-size:8pt"><span new="" roman="" style="font-family:" times=""><span style="font-size:11.0pt">This paper presents a new robust fin control method based on</span><m:omath><i><span style="font-size:11.0pt"><span cambria="" math="" style="font-family:"><m:r> </m:r></span></span></i><m:ssub><m:ssubpr><span style="font-size:11.0pt"><span cambria="" math="" style="font-family:"><m:ctrlpr></m:ctrlpr></span></span></m:ssubpr><m:e><i><span style="font-size:11.0pt"><span cambria="" math="" style="font-family:"><m:r>L</m:r></span></span></i></m:e><m:sub><i><span style="font-size:11.0pt"><span cambria="" math="" style="font-family:"><m:r>2</m:r></span></span></i></m:sub></m:ssub></m:omath><span style="font-size:11.0pt">&nbsp;gain design to reduce ship roll motion and waves disturbance effects. The process involves the nonlinear dynamics of the ship roll and its fin actuator.&nbsp; External disturbances of waves and model parameters variations are considered as process uncertainties. The state feedback controller is designed to reduce the effect of wave disturbance on the controllable variables of the process. For controller design, nonlinear </span><m:omath><m:ssub><m:ssubpr><span style="font-size:11.0pt"><span cambria="" math="" style="font-family:"><m:ctrlpr></m:ctrlpr></span></span></m:ssubpr><m:e><i><span style="font-size:11.0pt"><span cambria="" math="" style="font-family:"><m:r>H</m:r></span></span></i></m:e><m:sub><i><span style="font-size:11.0pt"><span cambria="" math="" style="font-family:"><m:r>&infin;</m:r></span></span></i></m:sub></m:ssub></m:omath><span style="font-size:11.0pt">&nbsp;approach has been employed in the sense that it ensures the stability of the process and achieves the desired control objectives. To solve the inequalities associated with the nonlinear </span><m:omath><m:ssub><m:ssubpr><span style="font-size:11.0pt"><span cambria="" math="" style="font-family:"><m:ctrlpr></m:ctrlpr></span></span></m:ssubpr><m:e><i><span style="font-size:11.0pt"><span cambria="" math="" style="font-family:"><m:r>H</m:r></span></span></i></m:e><m:sub><i><span style="font-size:11.0pt"><span cambria="" math="" style="font-family:"><m:r>&infin;</m:r></span></span></i></m:sub></m:ssub></m:omath><span style="font-size:11.0pt">&nbsp;problem, an efficient SOSTOOL-based algorithm is presented. Simulation results are presented to evaluate the efficiency of the proposed approach.</span> <span style="font-size:11.0pt">In order to validate the proposed algorithm, it is compared with PID controller. Results show the superiority of the designed controller based on Robust Nonlinear </span><m:omath><m:ssub><m:ssubpr><span style="font-size:11.0pt"><span cambria="" math="" style="font-family:"><m:ctrlpr></m:ctrlpr></span></span></m:ssubpr><m:e><i><span style="font-size:11.0pt"><span cambria="" math="" style="font-family:"><m:r>H</m:r></span></span></i></m:e><m:sub><i><span style="font-size:11.0pt"><span cambria="" math="" style="font-family:"><m:r>&infin;</m:r></span></span></i></m:sub></m:ssub></m:omath><span style="font-size:11.0pt">control over PID controller.</span></span></span><br> &nbsp;</div> ship roll,L_2 gain,robust control,nonlinear H_∞ control 57 64 http://ijmt.ir/browse.php?a_code=A-10-1662-2&slc_lang=en&sid=1 hamid malekizadeh h.malekizadeh@yahoo.com 10031947532846004089 10031947532846004089 Yes Department of Electrical Engineering, Imam Khomeini University of Maritime Sciences, Noshahr, Mazandaran, Iran