Abstract

An inertial platform accelerometer cluster (FIG. 1) comprises a cluster of gyro and accelerometer system triads disposed in a cluster housing 10 to detect motion along and about orthogonal x, y and z axes. The orthogonal accelerometer systems each comprises a pair of codirectional accelerometers e.g. 15x, 15'x having an operating bandwidth from 0 to several KHz mounted on the housing walls equidistant from a point 14, which represents a common center of percussion to all pairs, at the center of gravity of the cluster. The analogue output signals of each accelerometer pair are scaled, summed and differenced to provide `sum` and `difference` signals which represent respectively acceleration in the sensitive direction and angular acceleration about an orthogonal axis. The sum and difference signals can be used in analogue correction generating circuitry to obtain correction signals for coning and sculling effects, for which responses at high-frequency are called for, while economizing on computer time and capacity. Furthermore the coincidence of the center of percussion for all accelerometer pairs eliminates size effect errors from the `sum` signal which is employed for the normal inertial platform computations. Separate high- and low-frequency responsive accelerometers may be used.