Analysis of the Effect of Mass Unbalances and Assembly Tolerances on the Performance of the Four-Axis Stabilised Director Mount

摘要

A necessary component of many weapon systems is the stabilised mechanical mount, used for directing the boresight of sensors and designators and the launching rails of weapons. It must be able to point the boresight accurately in any direction (within a predetermined sector of three dimensional space) despite the inevitable changes in attitude adopted by the carrying vehicle. Two axes of motion between vehicle and boresight is the minimum number required, but practical considerations (such as the difficulty of providing unlimited motion about the axes, and the desire to reduce the inertia of rapidly slewing structures) often result in the use of three or four axes. Perhaps the most commonly used arrangement is that of the elevation-over-azimuth-over-pitch-over-roll, four-axis mount. This Australian report analyzes that type of director mount to determine the torques generated by mass unbalances about the motor driven axes. The effect of these on the motion of the stabilised platform, and the effect of this motion, as well as that of mechanical tolerances, on the accuracy of direction is examined. The analysis is restricted to the case of the fully erect system, firmly connected to a stationary, level surface, but the method of approach could be extended to more complex situations. The results provide the basis for the design of small, lightweight, high performance directors.