Design of a holonomic omnidirectional vehicle using a reconfigurable footprint mechanism and its application to a wheelchair

摘要

In this paper, a new mechanism for varying the footprint of a four-wheeled omnidirectional vehicle ispresented. A chair is mounted on a moving platform with four ball wheels allowing for holonomic,omnidirectional motion. Two pairs of ball wheels at the diagonal positions of the chassis are fixed,respectively, to two beams that intersect at a pivotal point in the middle. The angle between the twobeams crossing at the pivotal point is varied actively so that the ratio of the wheelbase to the tread canbe varied. Four independent servomotors driving the four ball wheels allow the wheelchair to movealong three axes, i.e. x, y, andΦ), and change its footprint at the same time. The footprintconfiguration is controlled based on the measurement of the mass centroid position in such a waythat the mass centroid can be kept within the footprint area at all times. First the concept of thereconfigurable footprint mechanism is described, and its kinematic and static behavior is analyzed,followed by the control design for augmenting the vehicle stability. A prototype wheelchair platformis designed, built, and tested.