When a European Space Agency (ESA) launcher, such as the Ariane 5 or Vega, delivers its satellite payload into orbit, the attitude control system (ACS) takes control, orients the payload, and commands the separation from the upper stage of the launcher. In addition to orienting the satellite, the ACS must identify and manage problems associated with the separation process, the sloshing of propellant, and a wide range of potential hardware faults.
The ESA Future Launcher Preparatory Programme (FLPP) evaluates novel technologies that increase launcher capabilities at reduced costs. A special FLPP project dedicated to develop an Upper Stage Attitude Control and Design Framework (USACDF) has been put into place for development of future complex orbital missions. The framework was developed using Model-Based Design with MATLAB® and Simulink® and includes multidomain physical models of separation mechanisms, thermodynamics-based propulsion, and CFD-based fuel tank fluid sloshing, enabling closed-loop, system-level simulation of the control software in normal operation and under fault conditions.
“In the past, it was difficult for control engineers to switch between and integrate domain-specific fluid dynamics, mechanics, thermal, propulsion, and other disciplines,” says Samir Bennani, guidance navigation and control system engineer at ESA. “Model-Based Design enables us to span multiple disciplines and use one environment for the entire process, from tracing specifications to the design through validation with processor-in-the-loop testing.”