[CCoE Notice] Ph. D. Dissertation Defense on July 23 at 1 pm in 102D

[Khator, Suresh]

Ph.D. Dissertation Defense 

Room  : 102D 

Date    : 07.23.2010    (1-3pm)

 

LPV GAIN SCHEDULING CONTROL AND ITS APPLICATIONS ON HYSTERESIS COMPENSATION AND BIOMEDICAL ROBOTICS

 

Atilla Kilicarslan

Abstract:

This dissertation addresses the problems of compensating for the hysteresis nonlinearity present in Shape Memory Alloy (SMA) wire actuators and control of a biomedical robotic system.

At first, we examine some important properties of the hysteresis nonlinearity and formulate the control methods implemented on the designed experimental systems. The first system is actuated with an SMA wire actuator. Due to the temperature dependent hysteretic nonlinearity, it is a challenging problem to model and control the response of the SMA system precisely. We formulate an Adaptive Neuro-Fuzzy Inference System (ANFIS) model and controller, robust H∞ and LPV gain scheduling controllers for this purpose. 

In the second part, we experimentally verify the designed modeling and control methods and compensate for the hysteretic nonlinearity in real time. The robustness of the controllers plays an important role in hysteresis compensation especially for systems actuated with SMA wires. Having a responsive behavior highly dependent on the applied heat, environmental disturbance acting on these systems can greatly affect the displacement response, or make the overall closed loop system unstable. We compare the performances of the controllers under high levels of plant disturbance (heat fluctuations).

The third part is dedicated to the modeling, prototyping and control of a novel biomedical robotic system. This system is designed to assist the surgeon during the delicate minimally invasive direct apical approach to aortic valve replacement operations. The designed robot has the capability of exerting haptic force feedback on the medical tool that the surgeon uses during the operation. We define the design constraints, work space and working principle of the robot in detail. We then introduce the prototype of the robot and discuss; the details of the mechanical components and assembly, electronics used for actuation, the real time data acquisition system and the software development for real time control purposes. For a realistic real time implementation, we use a dynamic virtual model of the left ventricle of the heart. The workspace of the robot is defined as the boundaries of the left ventricle. For haptic controller, we model these boundaries as virtual walls and provid
 e operator the interaction forces acting between the end effector of the robot and these unilateral constraints. These safe boundaries define the dynamically changing maximum available workspace that separates the inner gap and the inner most layer (endocardium) of the heart. By proving the haptic effect, the robotic system assists the surgeon to keep the end effector position between these safe boundaries. A virtual frictionless environmental model is also introduced to compensate for the inherent damping of the system to let the end effector move freely if the tool’s end effector is not interacting with the unilateral constraints. Finally an LPV gain scheduling controller is implemented on the haptic system for precise trajectory tracking applications. The designed controller then tested on the experimental system in real time for a pre-defined trajectory on the workspace of the robot. This controller’s performance yields promising results to be used for deve
 loping teleoperation (remote surgery) applications where the needs of precise and robust trajectory tracking control schemes are essential.

 

Committee Members
Dr. Karolos Grigoriadis (Advisor, Chair of the Committee)                      
Dr. Gangbing Song                  
Dr. Javad Mohammadpour       
Dr. Nikolaos Tsekos               
Dr. Jagannatha R. Rao <http://www.egr.uh.edu/me/faculty/rao/> 

 

_______________________________________________________

Suresh K. Khator, Ph.D., P.E.                         Phone: 713-743-4205         

Associate Dean, College of Engineering    Fax: 713-743-4214

University of Houston                                     Email: skhator at uh.edu   

E421 Engineering Bldg 2                                www.egr.uh.edu/ie

Houston, TX 77204-4008

 

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