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Journal of Guidance, Control, and Dynamics


"Modified linear theory provides reasonable impact predictions at high speeds. However, for typical small UAS mission speeds, less than 20-m/s impact errors were substantial due to large angles of attack and pitch rates. Low-speed linear theory was developed by including higher-order terms involving w and q that modified linear theory neglects. As a result, the angle of attack, pitch, and yaw predictions are significantly improved, leading to accurate impact predictions even at very low speeds. A predictive control scheme was developed to reduce dispersion using control surfaces near the tail. The predictive controller uses low-speed linear theory to rapidly predict the impact error using the current state and control. Based on the estimated impact error, the control is iteratively found to minimize the predicted-impact error. For an example munition, it was shown that the maximum number of iterations during the control solution only impacted the initial control estimates. Limiting the guidance algorithm to a single iteration had little impact on the final accuracy and permitted a rapid solution. It was shown for the example munition that the predictive guidance significantly reduced the CEP from 14.1 to 2.7 and 2.2 m when the maximum iterations were 1 and 10. Furthermore, for a typical high- explosive 40-mm grenade, the percentage of impacts within a lethal radius was increased from 10 to 78% when the maximum iterations were both 1 and 10. In practical applications, errors in the target location must beincluded when considering the probability of impact within a lethal range of a target."





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Originally published in the Journal of Guidance, Control, and Dynamics, Vol 31, No 3, pp 768-774, 2008.