Predictive Launcher Guidance Using Second Order Sliding Mode Control

Abstract

A new approach to the design of a simplified predictive launcher-guidance is presented. The first stage open-loop prescribed launcher trajectory is simply defined by a controlled pitch tip-off maneuver. Second and third stage closed loop in-plane guidance is based on the continuous calculation, at each thrusting-time of commanded velocity required to achieve the mission objective; function of the current position. Second and third stage out of plane guidance is based on the dot product of velocity and position errors with the unity vector orthogonal to the desired orbital plane. Corresponding values of second and third stage in-plane terminal semi major axis, eccentricity required to achieve desired circular orbit altitude objectives are calculated off-line for given launch latitude and azimuth angle. The autopilot tracking commanded velocity is based on second order sliding mode control technique that yields continuous controls, and achieves desired error response in finite time. Robust high accuracy launcher guidance is achieved in presence of wind shear at the beginning of the trajectory and considerable uncertainties in the thrust magnitude model. The algorithm was tested on Ariane IV type launcher model. Results of the computer simulation demonstrate excellent robust high accuracy tracking performance of the proposed design. Nomenclature