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Design and Implementation of Nonsmooth Controller for Mechanical Systems under Nonholonomic Constraint

Jafari Harandi, Mohammad Reza | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48876 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Namvar, Mehrzad
  7. Abstract:
  8. This thesis works on certain type of underactuated mechanical systems with nonholonomic constrain, namely wheeled robots.Since this robots has different types, this work focuses specifically on three-wheeled robot. At first we know kinematic characteristics of robot system and equations of motion.To control this system, at first we will change equations to chain form, then control it by using known methods. It will be shown that between the known methods for convergence to a fixed point,irregular transformation is the best way for control systems in chain form.Also, with dynamic feedback linearization we can control robot on a trajectory that has a continuous third order derivatives. Then for collision avoidance with a fixed obstacle or other robot, we define fields around each robot that is a function of the distance the robot and obstacle. The range of fields are limited and if the distance between the robot and obstacle is higher than certain level, the field does not exist. By reducing the distance, these fields appeared smoothly and their size becomes larger so that at a predetermined distance, are equal to infinity. In addition, the oscillating motion of the robot is minimized. Finally, by simulation, the performance of this method will be shown in a few examples.This field is known as the potential fields. The way is that by guiding the robot in the direction gradient and perpendicular to the gradient, it will be guaranteed that the collision don’t happen. To select the vector perpendicular to the gradient vector, direction that robot pass shorter path to desired point will be selected. The good feature of this vectors is minimizing oscillating motion of the robot. Finally, by simulation, the performance of this method and comparison to previous work in the form of a few examples will be shown
  9. Keywords:
  10. Wheeled Robot ; Collision Avoidance ; Locomotion Control ; Potential Field Method ; Nonholonomic Constraints ; Mechanical System

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