A Counterbalance System for Dynamic Testing of Equipment Designed to Operate in a Zero-G Field

Abstract

The development and design considerations of a counterbalance system utilizing a servomechanism are given. The purpose of the counterbalance system is to allow dynamic testing of equipment to be used in a zero-g field. The problem of cancellation of gravitational torques and obtaining valid test data is discussed. Various techniques of counterbalancing are investigated. The method having the most flexibility uses a servo-mechanism and an energy-storage device. For this system a linear torsion spring is attached to the device being counterbalanced and is used for the energy-storage element. A strain gage gives a voltage indicating the counterbalance torque being applied by this spring. The reference voltage is proportional to the counterbalance torque required and comes from a resolver. The difference between these two signals controls the position of the other end of the torsion spring. With this mechanization it is shown that the requirements on the performance of the servomechanism are not severe. It is concluded that the technique using an energy-storage device and a servomechanism offers advantages which other techniques do not. The possibility of using other mechanizations of this counterbalancing technique is discussed.