Holonomic and omnidirectional wheelchairs with synchronized 4WD mechanism

This paper presents a new type of omnidirectional and holonomic mobile platform with a four-wheel-drive (4WD) mechanism for improving traction of electric wheelchairs on slippery surfaces and enhancing mobility on rough terrain. The 4WD mechanism includes a pair of normal wheels on the rear and a pair of omniwheels on the front. The normal wheel in rear and the omniwheel in front on the same side of the drive mechanism are connected by a power transmission to rotate in unison with a common motor. Omniwheels enable the front of the mechanism to roll freely from side to side. A third motor turns the chair about a vertical axis at the center of the mobile platform Thus the platform is controlled by three motors, no redundancy and no motor confliction are found on the drive system High step climb capability of the 4WD mechanism solves the insufficient mobility problem and the omnidirectional control enables simple and easy operation with no complicated maneuvering. To verify the availability of the proposed mobile system for wheelchairs, a prototype is designed and built. The fundamental step climb capability and holonomic and omnidirectional mobility are verified by a series of experiments.