Minimization of Spring Torque in Flexible Connections to Instruments

Abstract

Precision electromechanical measuring instruments of various kinds often require establishing electrical connection to the suspended part of the instrument, with minimum introduction of disturbing torques. Requirements are especially demanding in the case of gyroscopes. Gyroscopes of high-precision type, as used in inertial-guidance systems and in advanced flight-control systems, generally take the form of a gimbal member which contains the rotor and which is supported relative to the case by some form of minimum-friction bearings. Usually, at least three electrical connections are required (for the polyphase rotor drive motor), which take the form of wires or ribbons extending from the case to the gimbal member. Disturbing-torque levels about the gimbal axis or axes must be kept to extremely low values; the total tolerable disturbing torque from all sources whatever is often of the order of one dyne-cm or less. Special attention must be given to the electrical lead-in connections (a) to minimize mechanical hysteresis effects, which result in erratic bias changes, and (b) to minimize spring rate. While spring coercion is a conservative type of force, it nevertheless must he kept very small, otherwise a shift of null of the pickoff which detects gimbal displacement will result in a steady spring bias.

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