Abstract
This paper presents a two-phase guidance and control algorithm to extend the range and improve the impact point accuracy of a 122-mm rocket using a fixed canards trajectory correction fuze. The guidance algorithm consists of a unique glide and correction phase of the rocket trajectory that is activated after the flight’s apex. The glide phase operates in an open-loop configuration where guidance commands are generated to increase the range of the rocket. In contrast, the correction phase operates in a closed-loop configuration where the Impact Point Prediction method based on Modified Projectile Linear Theory is used as a feedback channel to correct the range and drift errors. The proposed fixed canards trajectory correction fuze has a simple and reliable single channel roll-orientation control configuration. The rocket trajectory model consists of a 7-DOF non-linear dynamic model of a dual-spin rocket configuration with a fixed canards correction fuze mounted at the nose. A Monte Carlo simulation of the rocket’s inertial and launch point perturbations show that the fixed canards fuze with the proposed guidance algorithm can double the range of the rocket without changing the rocket motor thrust-time curve. At the same time, the rocket’s accuracy can also be improved beyond the results of an unguided rocket.
Highlights
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The control mechanism of these trajectory correction fuzes is implemented through force generated by impulse thrusters or aerodynamic asymmetry caused by cruciform-shaped control canards mounted at the outer surface of the fuze
Reference [10] describes the use of impulse thrusters for trajectory correction; the author uses the impact point prediction method to calculate deviation from longitudinal and horizontal axes, with the simulation results showing that the Circular Error of Probability (CEP) of uncontrolled rockets = 359 m, while the CEP for general firing control scheme = 38 m, and the CEP for optimum firing control scheme = 20 m
Summary
122-mm artillery rockets launched from the Multiple Launch Rocket System (MLRS) are still the first battlefield choice against ground targets, but they are attributed with a short range and larger dispersion radius due to manufacturing inaccuracies and launchpoint perturbations. The other method to increase range is to add impulse thrusters near the rocket’s Center of Gravity (C.G) or, more recently, rocket range can be extended by using high lift ratio moveable canards to increase the angle of attack to generate more lift force [14,15]. These methods require a major rocket hardware change, making these methods complex and expensive for the low-cost 122-mm rocket.
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