Skande Martin. Numerical solution to a nonlinear external ballistics model for a direct fire control system

Stockholm, Sweden: Master of Science Thesis. 2014. – 86 р.This Masters Thesis is a development and evaluation process of a numerically solved nonlinear external ballistics model for a direct Fire Control System developed by SAAB Technologies. The currently used external ballistics model is linearized which significantly simplifies the task of meeting hard real-time constraints on the system but due to the approximations and simplifications tied to the linearization of the external ballistics there exists room for improvements in terms of calculation accuracy. Increasing demands on system level performance together with initial investigations on the Fire Control System concluded that there was interest for an evaluation of a numerical solution in terms of calculation accuracy and processing load. The project focuses on the process from concept development of a numerical external ballistics solution all the way to actual implementation on the targeted Fire Control System. The work is founded on a theoretic frame of reference on primarily external ballistics theory. The concept that has been developed uses a nonlinear external ballistics model based on an existing Modified Point Mass Trajectory Model (MPMTM) described in the theoretic frame of reference and is solved using a fourth order Runge-Kutta integrator. An iterative method similar to that of a discrete time control loop is used to find boundary values of the ballistics model satisfying hard real-time constraints on the system. Parameterization of the external ballistics model was carried out using firing-tables provided from the projectile manufacturer and the resulting calculation accuracy was improved relative the existing linearized solution. The conclusion of the project is that a numerical solution is possible despite the hard real-time constraints on the system and can increase the system level performance, particularly so for long range trajectories. However because the solution increases the complexity of the ballistics calculation software and complicates the parameterization method it is not advised unless the system level performance is deemed a problem.