Yaw rate and linear velocity stabilized manual wheelchair

We present the development of a prototype novel low-power, inexpensive stability control system for manual wheelchairs. Manual wheelchairs, while providing the ability to maneuver in relatively small indoor spaces, have a high center of gravity making them prone to tipping. Additionally, they can easily slide on sloped surfaces and can even spin and tip when attempting to turn or brake too quickly. When used on ramps and in outdoor environments where the surface is rarely perfectly flat (slopes greater than 1:20 (5%) are common), wheelchair users can easily encounter potentially dangerous situations. The design and evaluation of an accident prevention system for independent manual wheelchair users that increases independence by enabling mobility with greater confidence and safety is described. The system does not limit a wheelchair user´s ability to manually brake, rather, if the system detects that the wheelchair is out of control, braking force will be added by the system to either one or both wheels. The prototype utilized inexpensive bicycle technologies for the wheel brake and electrical power generator assemblies. Custom servos were designed along with custom electronics and firmware in the prototype to evaluate performance. The goal of the project was to derive specifications for a control and actuation system that utilizes inexpensive bicycle components in this cost-sensitive application. The design is detailed and the final specifications provided.