Development of cart providing constant steerability regardless of loading weight or position : 2nd Report: Proposal of the operational interface

In this study, we aim at development of the cart providing constant steerability. The steerability of a cart is changed by the loading weight and position. Thus, user feels uncomfortable, and usability is decreased. To solve this problem, we have developed an active steering caster being attached on the cart and provides a constant steerability. Two proposed active steering casters and two conventional casters are attached on the cart in diagonal position. The moving direction is determined by controlling the steering angles of the active steering casters. In this paper, we propose an operational interface that measures the force and the moment of force at the handlebar. The direction of the force and the moment of force determine the moving directions of the cart as user intention. In order to measure the force and the moment of force, strain gauges are glued on both handle posts of a cart. Therefore, additional component is not needed. Moreover, this interface is simple structure. The experiment has been conducted to verify the feasibility of measuring force and torque at the handlebar in order to estimate user’s intention for moving direction.