Novel Design of a Wheelchair with Stair Climbing Capabilities

Stair climbing wheelchairs were created to help disabled people overcome one of the most common architectural barrier, stairs. Many types of devices have been developed using tracked, leg, leg-wheel and hybrid wheels to climb stairs but they are expensive, thus, out of the reach of the neediest. This paper presents a stair climbing wheelchair with four "X"-shaped wheel that uses its legs to climb and descend stairs. This mechanism maintains contact with the stair during climbing activity to perform better at the climbing task. The seat of the wheelchair provides 1 DOF so that the inclination angle can be changed in order to correct the position of the center of gravity to be close to the center of the supporting polygon. An inertial measurement unit (IMU) sensor was used to detect the angle of the seat in relation to the ground and by using a motor utilizing PID control, automatically balance the seat in the horizontal position. In order to climb stairs smoothly the angular position of the wheels should be the same, thus a PD control was implemented to control the position of the wheel so that they will be synchronized, therefore, capable of performing the climbing task at the same time and at the same position. Simulation and experimental results demonstrate the effectiveness of this mechanism and wheelchair.