Control Authority of a Projectile Equipped With an Internal Unbalanced Part

A key technical challenge for smart weapon developers is the design of appropriate control mechanisms that provide sufficient control authority to enable correction of typical trajectory errors while not excessively burdening the overall weapon design. The work reported here considers a rotating mass unbalance control mechanism, created by radial orientation of an internal part. To investigate the potential of this control mechanism, a seven degree-of-freedom flight dynamic model of a projectile, equipped with an internal part is defined. Using this dynamic model it is shown that by holding the internal part fixed with respect to a nonrolling reference frame, predictable trajectory changes are generated including predictable impact point changes. As expected, when unbalance-offset distance, or mass is increased, control authority increases proportionally. This control mechanism creates impact point changes that are the same order of magnitude as dispersion caused by errors induced at launch and in flight. Control authority is significantly altered with changing projectile characteristics, such as, the mass center location, pitch inertia, yaw inertia, aerodynamic drag, and aerodynamic normal force.