Basic performance of a joint mechanism with multi-directional adjustable stiffness

This paper describes basic performance of a novel joint mechanism with a multi-directional adjustable stiffness. In this mechanism, two different kinds of air cushions (Cushion A and Cushion B) are placed between a motor-driven disk and an output link. The rotational motion of the motor is transmitted to the output link with the friction force between the surface of Cushion A and the motor-driven disk. In addition, Cushion A plays following two important roles: (1) Absorption of external forces by its elastic deformation and slippage on the motor-driven disk and (2) Sensing the directions and amplitude of external forces with the pressure change in it. On the other hand, Cushion B controls the degree of pressing Cushion A against the motor-driven disk by its expansion. The increment of pressing force of Cushion A results in the increment of joint stiffness, because the elastic deformation and slippage of Cushion A are prevented. This paper describes the detail of joint mechanism and its basic performance.