Forward Chaining for Potential Field Based Navigation

A key ability for any real world robotic agent and for many simulated agents in virtual environments is the ability to navigate successfully to goal positions within their world. It is often necessary to do this in the presence of obstacles that limit access to parts of the agent’s world. This thesis addresses the problem of agent navigation in the situation where an agent is seeking a goal in the presence of obstacle configurations. Potential fields are used to model the navigational problems, and purely potential field based heuristics are given as solutions. Existing potential field based techniques and alternative navigation approaches are shown to lack certain desirable properties that might allow them to be considered completely successful. The general problem of potential field navigation is addressed here using subgoal chaining. A series of novel potential field based subgoal selection heuristics are developed that guide the agent to success in the presence of the stated problem conditions. Development of the heuristic begins by modelling a solution for the simplest two dimensional environments, and then extending it to solutions for problems of greater complexity. The techniques developed here are shown to be successful on a wide variety of problems. Applications for these solutions are suggested in robotics, animation and computer games as well as in other areas of potential field research such as neural networks. Suggestions are given for ways in which competing techniques within navigation can be augmented by applying the results of this research. The remaining problems for potential field based agent navigation are highlighted for future study. I, Graeme Bell, hereby certify that this thesis, which is approximately 71000 words in length, has been written by me, that it is the record of work carried out by me, and that it has not been submitted in any previous application for a higher degree. date signature of candidate I was admitted as a research student in September and as a candidate for the degree of Doctor of Philosophy in September ; the higher study for which this is a record was carried out in the University of St Andrews between and . date signature of candidate I hereby certify that the candidate has fulfilled the conditions of the Resolution and Regulations appropriate for the degree of Doctor of Philosophy in the University of St Andrews and that the candidate is qualified to submit this thesis in application for that degree. date signature of supervisor In submitting this thesis to the University of St Andrews I understand that I am giving permission for it to be made available for use in accordance with the regulations of the University Library for the time being in force, subject to any copyright vested in the work not being affected thereby. I also understand that the title and abstract will be published, and that a copy of the work may be made and supplied to any bona fide library or research worker. date signature of candidate “If I have seen farther than others, it is because I was standing on the shoulders of giants. ” Isaac Newton “If I have not seen as far as others, it is because giants were standing on my shoulders. ” Hal Abelson “In computer science, we stand on each other’s feet. ” Brian Reid