Applications of internal translating mass technologies to smart weapons systems

The field of guided projectile research has continually grown over the past several decades. Guided projectiles, typically encompassing bullets, mortars, and artillery shells, incorporate some sort of guidance and control mechanism to generate trajectory alterations. This serves to increase accuracy and decrease collateral damage. Control mechanisms for smart weapons must be able to withstand extreme acceleration loads at launch while remaining simple to reduce cost and enhance reliability. Controllable internal moving masses can be incorporated into the design of smart weapons as a mechanism to directly apply control force, to actively alter static stability in flight, and to protect sensitive components within sensor packages.;This dissertation examined techniques for using internal translating masses (ITM's) for smart weapon flight control. It was first shown that oscillating a mass orthogonal to the projectile axis of symmetry generates reasonable control force in statically-stable rounds. Trade studies examined the impact of mass size, mass offset from the center of gravity, and reductions in static stability on control authority. A more detailed analysis followed in which a physical internal translating mass control mechanism was designed that minimizes force and power required using a vibrating beam as the internal moving mass. Results showed that this relatively simple mechanism provides adequate control authority while requiring low on-board power. Trade studies revealed the affect of varying beam lengths, stiffness, and damping properties. Then, the topic of static margin control through mass center modification was explored. This is accomplished by translating a mass in flight along the projectile axis of symmetry. Results showed that this system allows for greater control authority and reduced throw-off error at launch. Finally, a nonlinear sliding mode controller was designed for a projectile equipped with an internal moving mass as well as for a projectile equipped with both an ITM and canard control mechanisms. Monte Carlo simulations that incorporated realistic uncertainty demonstrated the robust nature of the control system. These dispersion simulations examined the effect of ITM size and incorporation of a variable stability mechanism. It is shown that use of an ITM as a direct control mechanism can reduce circular error probable by nearly half, while coupling ITM control with canard control can reduce required canard area by approximately half as well. Overall, it was determined that direct ITM control generates modest control authority for practical systems. Therefore, it can be used to reduce dispersion error but not eliminate it to levels commensurate with sensor noise. Likewise, the ITM variable stability mechanism provides a limited control authority enhancement to guided projectiles controlled by other means. Thus, while the mechanism may not be useful for guided munitions that exhibit ample control authority, it provides a useful supplement to projectiles requiring slight control authority improvement.