A Comparison of Different Guidance Schemes for a Direct Fire Rocket With a Pulse Jet Control Mechanism

Report No. ARL-CR-493
Authors: Thanat Jitpraphai, Bradley Burchett, and Mark Costello
Date/Pages: April 2002; 32 pages
Abstract: Compared to gun launch ammunition, uncontrolled direct fire atmospheric rockets are terribly inaccurate, to the point where they are used most effectively on the battlefield as area weapons. Dispersion characteristics can be dramatically improved by outfitting the rocket with a suitable control mechanism and sensor suite. In the work reported here, a lateral pulse jet control mechanism is considered. The lateral pulse jet mechanism consists of a finite number of small thrusters spaced equally around the circumference of the rocket. Using a simulation model that includes projectile, flight control system, and inertial measurement unit dynamics, three different control laws are contrasted, namely, proportional navigation guidance, parabolic and proportional navigation guidance, and trajectory tracking control laws. When the number of individual pulse jets is small, a trajectory tracking control law provides superior dispersion reduction. However, as the number of pulse jets is increased, the relative performance of the parabolic and proportional navigation guidance control law is slightly better than the trajectory tracking control law. When the number of pulse jets is small, the proportional navigation guidance, as well as the parabolic and proportional navigation guidance control laws, exhibits large mean miss distance. All control laws appear to be equally susceptible to accelerometer and gyroscope errors that corrupt inertial measurement unit rocket state feedback.
Distribution: Approved for public release
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Last Update / Reviewed: April 1, 2002