Force Measuring System with Zero-Compliance Suspension

Abstract

The principle and classification of force measuring system with zero-compliance suspension are described. A zero-compliance suspension consists of series-connected suspensions, one of which operates to cancel the variation of length of the other suspension. As a result, the total length of the connected suspensions is invariant even when force acts between the ends. In the force measuring system, one end is fixed to the base and force to be measured is applied to the other end (point of application). The force is estimated from the displacement of the connection point of the suspensions that is to be detected (detection point). This principle of measuring force is explained in a basic model. Measuring systems are classified according to the location of active element, the actuator of the active element, and the location of positive-stiffness element. Several examples of measurement system are described. Then, control methods of achieving zero-compliance are explained for an apparatus using double series magnetic suspension. Finally, measurement results by the developed apparatus are shown. It is confirmed experimentally that the displacement of the detection point is proportional to external force acting on the point of application and high-resolution measurement is possible by the developed system.