FöRFATTARE
Workicho Oumer, Nassir

INSTITUTION
Rymdvetenskap, Kiruna /

SAMMANFATTNING
The purpose of this thesis was to develop a control method which can reduce oscillation of lateral motion for a pendulum driven spherical robot operating on flat surface. The spherical robot provides a unique mobility and has several applications in surveillance and entertainment.

Controlling a spherical robot is a challenging problem till today due to its nature of kinematics and dynamics. Firstly, its nonholonomic nature prohibits the use of conventional state feedback control laws. Secondly, kinematics of a spherical robot cannot be expressed as a chained-form system to utilize nonholonomic control algorithms. However, various types of nonlinear control algorithms were proposed to settle the problem though none of them provided satisfactory result.

The kinematics and dynamics of the pendulum driven spherical robot was investigated followed by linearization for longitudinal and lateral motions through frequency and state space transformation. Moreover, the controllability of the states of the system was maintained during linearization. A robust self-tuning sliding mode controller which suspends oscillation, maintains desired speed and compensates for unmodeled parameters was developed. The implemented control system consists of control station, prototype robot equipped with on-board microcontroller and sensors, and wireless communication link.

Simulation and experimentation were conducted to test peformance of the control laws in suppressing oscillation and maintaining desired speed of the robot. The robot traveled to the commanded trajectory containing straight line and curve with relatively minimum oscillation at desired speed. Thus, the sliding mode control is an effective controller.

ISSN 1653-0187 / ISRN LTU-PB-EX--09/079--SE / NR 2009:079