Hardware-In-The-Loop Tests of Complex Control Software for Rocket Propulsion Systems

Abstract

Software of rocket propulsion systems has a very high complexity but must also guarantee an outstanding level of reliability. Therefore, extensive tests are inevitable during the development process to meet the requirements. However, ground tests of the entire propulsion system are extremely expensive and can not address all nominal and off-nominal behavior that could possibly occur during the mission. Hardware-in-the-loop simulations allow realistic testing of embedded systems (e.g., the engine controller or an actuator) by combining a software simulation with emulated electrical sensor and actuator signals. This contribution discusses hardware-in-the-loop methods for anomaly detection and control systems of rocket propulsion systems. We develop a roadmap surveying a step-by-step approach to demonstrate the reliability of advanced control algorithms and sketch how to deploy such algorithms on space-graded embedded systems. In the future, adaptive and reconfigurable control for the propulsion system will become increasingly important. Adaptive control can tune the control actions to uncertain or changing system characteristics. Also, coupling the control algorithms to suitable anomaly detection systems allows the safe reaction to unforeseen events, which further improves the reliability of the propulsion system. The DLR Institute of Space Propulsion operates extensive test facilities for developing propulsion system technologies to operational maturity and ensuring their quality. Specific attitude pointing aspects of the propulsion system software can be simulated by high precision turntables at the company Zentrum für Telematik (ZfT). Within the cooperation between the DLR Institute and ZfT, different aspects of complex control software for propulsion systems are analyzed and tested using the available facilities.