Locomotion Solution for Stair Climbing Wheelchair with ER Fluid Based Control

Wheelchairs for people with disabilities are generally intended for movement on dedicated or arranged terrains. Stair climbing or uneven terrain is a real challenge. Current models use two methods to overcome this problem. The first method is to move with the mixed wheels/tracks. The tracks are used for movement on stairs or rough terrain and wheels in the rest of the cases. The second method uses multiple wheels to solve the staircase issue. In this paper the authors propose a wheelchair whose wheels have variable geometry. When the stairs or rough terrain type appears, the wheels change their geometry by adjusting to the ground. Practically the wheelchair wheel is made up of slices/spokes that can extend linearly and controlled, along the wheel's rays. Thus, the contour of the wheel can be modeled so that it becomes the negative of the ground, and the movement of the seat is made along some curves or linear trajectories. The actuator used for the wheel extension is a hybrid structure combining a spring-type actuator with a rheological hydraulic piston. For extension of wheel spokes the spring action is used. The retraction of the wheel elements is made by trough of the weight of the wheelchair. The control of the extension and retraction of the wheel spokes are made through by the control of a rheological piston. In the paper is also presented the control algorithm for movement to a known topometry field.