Figure 6

Concept of the proposed step climbing mechanism. It is composed of a linear actuator, an active-caster, and some frames. Point A is at the top of the linear actuator, and point B is on its frame. Points C and D are on the wheel shaft of the active-caster and on the frame AC, respectively. The linear actuator is attached at the back of the wheelchair frame at an angle α, and the points A, B, and D are connected with pin joints so that they can be rotated. The maximum value of the angle β (∠BAD) is restricted by the length of the link BD. By cooperative control of the linear actuator and the active-caster, the points C and D can be moved.