Optical tracking control of a differentially-driven wheeled robot

Yeo, L 2012, Optical tracking control of a differentially-driven wheeled robot, Doctor of Philosophy (PhD), Aerospace, Mechanical and Manufacturing Engineering, RMIT University.

Document type: Thesis
Collection: Theses

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Title Optical tracking control of a differentially-driven wheeled robot
Author(s) Yeo, L
Year 2012
Abstract Mobile robotics has become an increasingly ubiquitous technology in modern times. A typical example is the wheeled mobile robot (WMR). In order for a WMR to function effectively, it must demonstrate excellent tracking control and localisation capabilities. This is achieved by having accurate and responsive control algorithms as well as high-precision sensor systems. However, this often requires complicated algorithms and expensive equipment.

This thesis proposes a system to show that good tracking performance can be achieved with moderately simple control algorithm and relatively inexpensive hardware. The platform used in this research was a differentially-driven wheeled robot constructed using the Lego MindstormsNXT system. Positional tracking was provided by two Avago optical laser sensors commonly found on the computer mouse. The main programming environments were MATLAB and Simulink, along with several other open-source applications.

In the first part of the thesis, a PID-based system is presented along with the two control schemes. The first is a purely kinematic model and the second includes dynamic constraints. For both versions, a cascaded PID design was employed and settings were manually tuned. The final mathematical models were computationally simulated and their respective results were analysed and compared. Hardware validation was not conducted for this phase of the research as the simulation results suggested that the PID-based system may not produce the desired level of tracking performance.

The second part of the thesis explores a model reference adaptive control system. Lyapunov's direct method was used to achieve stability and convergence in the system. In contrast to the PID-based model, a vastly more accurate geometric localisation technique was applied. The research identified a number of shortcomings in current geometric localisation methods and suggested ways to mitigate them. In addition, a novel approach for detecting faulty sensor readings was introduced in conjunction with the development of a semi-redundant system.

The eventual theoretical model was tested using computer simulation, and the outcome was contrasted with the results of the PID-based system. This was followed by the construction of a prototype in order to verify the validity of the proposed model. Various configurations of the adaptive model were tested and compared: the two localisation methods, use of single and dual sensors, and application of semi-redundancy.

The thesis concludes with the analysis of results of the prototype testing. The theoretical propositions in the thesis were shown to be amply validated. Suggestions for future research work are also presented.
Degree Doctor of Philosophy (PhD)
Institution RMIT University
School, Department or Centre Aerospace, Mechanical and Manufacturing Engineering
Keyword(s) Wheeled robot
mobile robotics
optical tracking control
adaptive control
dead reckoning
kinematic modelling
dynamic modelling
computer simulation
optical mouse sensor
Lego MindstormsNXT
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Created: Mon, 12 Aug 2013, 12:54:30 EST by Brett Fenton
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