Estimation of Normalized Longitudinal Force for an Electric Cart Using Equivalent-Input-Disturbance Approach

Electric carts are used by many elderly people living in Japan. To guarantee driving safety under any road and weather conditions, it is very important to obtain the information needed to control the torque of the cart in a real-time fashion. A key item of information is an estimate of the normalized longitudinal force (NLF). This paper presents a method for estimating the NLF based on the equivalent-input-disturbance approach. It uses two estimators: One estimates the inverse of the equivalent inertial of a one-wheel model, and the other uses that value to estimate the NLF. Although the method is very simple, it produces a precise estimate. Simulations have demonstrated the validity of the method.