Attitude control of an inverted-pendulum-type robotic wheelchair to climb stairs considering dynamic equilibrium

Abstract

The wheelchair is the major means of transport for elderly and physically disabled people in their daily lives. However it cannot overcome architectural barriers such as curbs and stairs. In this study, we developed an inverted-pendulum-type robotic wheelchair for climbing stairs. This wheelchair has a seat slider and two rotary links between the front and rear wheels on each side. When climbing stairs, the wheelchair rotates the rotary links while maintaining an inverted state of a mobile body by controlling the position of the center of gravity using a seat slider. In previous research, we confirmed that the wheelchair can climb by applying the control method consisting of a center-of-gravity control phase and rotary link control phase. However, it took approximately 15 s to rotate the rotary links during climbing because faster climbing causes the movement of wheels and the wheelchair to fall. This paper focuses on a control method to restrain the movement of the wheels when the stair climbing speed is increased. We realized that the movement was caused by forces acting on the pitch angle, such as the inertial force and the reaction of the driving force. We proposed the method considering the dynamic equilibrium of the pitch angle and confirmed the effect of the restraining wheels’ movement when the proposed method was applied.

Longitudinal Stability of Wheeled Mobile Robots - Degree of Stability

“…Usually, in similar studies, differential equations are used [1], [2], [4], [5] to represent the mathematical model. Instead, the D'Alembert's principle is used here, which considers an equilibrium system of forces, including inertial forces [6]; the accuracy of the calculations does not deteriorate.…”