Simulation and Control of Submarines

Abstract: When designing control systems for real applications, it is important to first do testing in a simulated environment, to ensure adequate performance. This is especially important when designing control systems for applications that have high operation costs, e.g., submarines, since late errors in the development can be extremely costly. Saab develops steering systems for submarines. Prior to this thesis, testing for those have been performed in an open-loop environment, where only static test cases could be examined. Saab therefore identified the need to implement a dynamic test simulator, which could react to the different signals from the steering system, i.e., act as a real submarine. In this thesis, such a simulator was developed. It consists of two parts, a physical model of a submarine, and a control system for motion control. As for the physical submarine model, it can be approximated from mechanical data of a submarine that the user provide, such as dimensions and weight. The second options is for the user to explicitly supply the simulator with hydrodynamic coefficients. The control system was derived to control a model of a demo submarine. Saab is also involved in submarine navigation systems and saw the need to, in the future, also have the possibility to test those products. A navigation system assumes an autopilot exists, hence, an autopilot control system was developed. In the end, the control system consisted of a two-level cascade controller of mixed LQG- and PID-control, along with a Kalman estimator for estimating unknown states. The results were overall satisfactory. The performance of the control system is well within usual customer specifications and the main problems in this thesis lay in getting a proper model.