Mobility is something able-bodied people take for granted. Approximately 132,500 people in the United Kingdom have disabilities which permanently confine them to a wheelchair; 40,000 of these require a powered wheelchair. The opportunity to lead a normal life and be accepted as an equal by the able-bodied population is limited by their reduced mobility. As much freedom of movement as possible is therefore crucial for these people. Powered wheelchair users' mobility depends upon the manoeuvrability of the chair. For optimum manoeuvrability a chair must be capable of moving in any direction. Currently no omni-directional powered wheelchairs are commercially available. This thesis describes the design and deVelopment of a powered base unit for a wheelchair, controlled to instantaneously move in any direction. The novelty is principally represented by the innovative design and configuration of four omni-directional roller wheels* (LUMAN wheels) which, when individually controlled, produce the omni-directional movement of the base unit. Further novelty within the design is a set of bi-directional angled roller couplings that simultaneously disengage the wheels from the motors, via a cable linkage mechanism, and simple control system. Mathematical data models illustrate the theoretical performance of the wheel configuration, and a prototype base unit is tested to prove these hypotheses.