Abstract: A compact, six-degree-of-freedom motion detecting system includes a hollow spherical motion input member adapted to be grasped by an operator, and a decoupling cube disposed within the motion input member and restrained against appreciable motion by a support shaft extending into the motion input member and secured at its opposite ends to the cube and a rigid base. Six translational motion sensors, each spaced outwardly from one of the cube side surfaces, are disposed within the motion input member and movably mounted on the cube by a support rod system. Each of the sensors includes a central longitudinal section of one of six flexible, fluid-filled tubes, the opposite end portions of each tube being extended outwardly through the motion input member and operatively connected to the inlets of one of six differential pressure transducers.