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چكيده انگليسي :

Adaptive Robust Control System Design for an Autonomous Underwater Vehicle Saeed Bahador Saeed bahador@me iut ac ir Date of Submission 2012 09 17 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Mohammad Danesh danesh@cc iut ac irAbstract Autonomous underwater vehicles could perform various underwater task ranging from sea floorsurveying ocean cable inspection and maintenance to petroleum drilling lost asset location and underwaterrescue Some of these applications necessitate a very strict positioning and force requirement on to theAUV controller However the AUV dynamics is inherently nonlinear It is also subject to uncertainexternal disturbances and the hydrodynamic forces are difficult to model All of these make AUV control avery challenging task These vehicles require autonomous guidance and control systems in order to performunderwater tasks Modeling system identification and control of these vehicles are still major active areasof research and development The control issue of underwater robots is very challenging due to the nonlinearity time variance unpredictable external disturbances such as the sea current fluctuation and the difficulty in accuratelymodeling the hydrodynamic effect Conventional linear controllers may fail in satisfying performancerequirements especially when changes in the system and environment occur during the operation since it isalmost impossible to manually retune the control parameters in water Therefore it is highly desirable tohave an underwater robot controller capable of self adjusting control parameters when the overallperformance degrades This thesis presents adaptive plus disturbance observer controller for underwaterrobots which is robust with respect to external disturbance and uncertainties in the system This controlscheme consists of disturbance observer as the inner loop controller and a nonregressor based adaptivecontroller as the outer loop controller This thesis describes an adaptive plus disturbance observer controller for underwater robots The nonregressor based adaptive controller does not require any physical information about the robot model exceptthe number of inputs and the number of outputs The non regressor based adaptive controller is veryeffective for autonomous underwater vehicles whose hydrodynamics can not be accurately modeled or mayvary while in operation as some changes occur in the system and environment Although the adaptivecontroller does not address robustness with respect to external disturbances while disturbance observer isvery robust with respect to external disturbances The disturbance observer basically removes the effect ofexternal disturbances and modeling errors and makes the system behave close to a nominal model that wasprechosen by the user However the disturbance observer controllers require using a low pass filter affectedby the nominal model and therefore the performance of the disturbance observer controller such asadaptive plus disturbance observer varies depending on the nominal model or the low pass filter In fact inthis thesis presents an adaptive disturbance observer controller using disturbance observer as an inner loopcompensator taking advantage of its robustness with respect to disturbances and using the non regressorbased adaptive controller as an outer loop controller taking advantage of its robustness with respect tomodel uncertainties due to the nominal model or the low pass filter The effectiveness of the adaptivedisturbance observer was investigated by simulating two control systems adaptive controller and adaptivedisturbance observer on an autonomous underwater robot ODIN The thesis is organized as follows Section II and Section III describes the factors affecting an underwater vehicle and Section IV describes the

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طراحي سيستم كنترل مقاوم وفقي براي شناور زير سطحي خودگردان

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