4WD Mechanism Research Articles

４輪駆動式電動車椅子の設計と全方向移動制御

This paper presents omnidirectional control and prototyping of a new type of electric wheelchair with four-wheel drive (4WD) mechanism for improving traction on the slippery surface and enhancing mobility on rough terrain of standard wheelchairs. The 4WD mechanism equips four wheels, two omni-wheels in front and two normal tires in rear. The normal wheel and the omni-wheel, mounted on the same side of the base, are interconnected by belt transmissions to rotate in unison with a drive motor, i.e. a synchro-drive transmission. To rotate a chair at the center of the 4WD about vertical axis, the third motor is installed on the platform. For omnidirectional control of the 4WD mechanism, two wheel motors are coordinated to translate the center of the chair in an arbitrary direction while the chair orientation is controlled by the third motor separately. Thus a wheelchair with proposed 4WD mechanism can move in any direction without changing the chair orientation and turn in a place, namely holonomic. In the paper, motion analysis of the 4WD mechanism and the omnidirectional control method are presented followed by prototype design for verification of the proposed 4WD omnidirectional wheelchair system.

2P1-E03 4WD全方向移動車いすのパワーアシストシステム

This paper presents a fundamental discussion and testing for designing a power assist system for an omnidirectional wheelchair with 4WD mechanism. It is our aim to develop a power assist system which allows care-givers and wheelchair-users to maneuver wheelchairs using a power assist function. To achieve this functionality, it is required to install a force-torque sensing device on the bottom of a chair. We develop a force-torque sensing system for a omnidirectional wheelchair since a device which is fit to our specification was not found on the market. The developed system was installed on the omnidirectional wheelchair prototype and fundamental functionalities were tested. In the experiments, step climbing and maneuvering by applied force on the front side of the chair were realized by the prototype wheelchair

Omnidirectional and Holonomic Mobile Platform with Four-Wheel-Drive Mechanism for Wheelchairs

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 back and a pair of omniwheels on the front. The normal wheel in back 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. One goal of this project is to apply the 4WD mechanism to a holonomic omnidirectional mobile base for wheelchairs to enhance both maneuverability and mobility in single wheelchair design. The 4WD mechanism guarantees traction on irregular surfaces and enhances step climbing over that of standard wheelchairs because all wheels have a large diameter and no passive casters are used. For omnidirectional control of the 4WD mobile base, two wheel motors are coordinated to move the center of the chair in an arbitrary direction while chair orientation is controlled separately by the third motor. The three motors thus provide nonredundant 3DOF chair movement. A wheelchair with our proposed mobile base moves in all directions without changing chair orientation and turns in place, i.e., holonomic. The configuration minimizing number of motors cuts costs and ensures a high reliable mechanism. We analyze the kinematics of planar motion and statics on the wheel step of the synchronized 4WD, then discuss the development of omnidirectional 4WD control. A series of experiments using a small robotic vehicle verifies kinematic and static models and the feasibility of the 4WD omnidirectional system proposed.