A five-wheel wheelchair with an active-caster drive system

Abstract

A novel wheelchair system with an active-caster drive mechanism is presented in this paper. A manual (hand propelled) wheelchair with an external single-wheel drive system forms a five-wheel configuration. The active-caster mechanism is applied to a drive system to motorize a manual wheelchair. Two electric motors which drive a wheel axis and a steering axis of a drive wheel independently are equipped on the active-caster. A coordinated control of the two motors enables the velocity vector on the steering shaft to direct in an arbitrary direction with an arbitrary magnitude. The generated velocity vector allows a wheelchair to go straight and/or rotate completely in a same way as a standard electric wheelchair. Namely 2DOF of the wheelchair can be controlled independently by a single drive wheel without any constraint, such as the orientation of the drive wheel which is well known as a non-holonomic constraint. In addition to the 2DOF mobility, the proposed system enables wheelchair users to change drive modes, a rear drive and a front drive. The drive wheel on the back side of the wheelchair is vertically actuated by a linear motor to change the height of the drive wheel that can vary load distribution and the number of wheels contacting to the ground. The five-wheel-contact makes the wheelchair to move as the normal mode in which the center of rotation is located at the midpoint of the main wheels. Depressing the drive wheel results in lost contacts of the main wheels from the ground in which the center of rotation is jumped at the midpoint of the front wheels, namely it performs as a front drive wheelchair. In this paper, kinematic models of the wheelchair and that with an active-caster drive system are analyzed and a control method by using a 2DOF joystick is derived. Based on the kinematic model, a prototype mechanism of the active-caster is designed and mounted on a manual wheelchair to realize the five-wheel wheelchair. In the experiments, the independent 2DOF motion can be achieved by the control of the active-caster in which the wheelchair shows successful translation, rotation and compound motions which include flip motions of the active-caster mechanism. Additionally, the two drive modes (front and rear) are tested by the prototype with a linear actuator.

Development and analysis of a novel add-on drive mechanism for motorizing a manual wheelchair and its step climbing strategy

“…This mechanism is realized by a linear actuator, attached between the active-caster and the wheelchair, which can vary the height of the drive wheel to change the number of points of contact with the ground. When all five wheels are in contact with the ground, the wheelchair can perform a pivot turn motion around the center of the large wheels (Figure 4(a)) [7]. Figure 4(a) shows that the large wheels contact on the ground and are rotated since the markers of the large wheels move gradually.…”

“…Figure 4(a) shows that the large wheels contact on the ground and are rotated since the markers of the large wheels move gradually. On the other hand, when the large wheels are hovered above the ground and the steering shafts of the front casters are fixed, the wheelchair can perform the same motion around the center of the front casters, avoiding the nonholonomic constraint of the large wheels (Figure 4(b)) [7]. Figure 4(b) shows that the large wheels float from the ground since the markers of the large wheels don't move.…”

“…As mentioned in the previous section, the kinematics model of a wheel climbing over a step is shown in Figure 7, and the condition required for the wheel to climb the step with only the traction force of the drive wheel is represented by equations (6) and (7). When the large wheels climb over the step, the drive wheel has the risk of slipping Figure 8 Wheelie motion of the wheelchair.…”

A motorized and easy-docking wheelchair drive for persons with lower-limb disabilities

“…He considered a linear actuator to adjust the caster to enable safe turning. [11] A wheelchair puller was attached to the front of a manual wheelchair to enable it to be operated like a motorcycle. However, it is necessary to add fixtures and attachments to the frames of a manual wheelchair.…”

Development of a Non-invasive Brain Computer Interface for Neurorehabilitation

“…From basic control of cursors being displayed on a computer screen [52]- [54] to robotic arms [55], prosthesis [56] and even wheelchairs [57], [58]. Depending on the application of the BCI, different neural-recording techniques can be used.…”