Closed-loop control of throttleable engines - expro plus

The objective of this activity is to develop and test a multivariable robust control system for mixture ratio and chamber pressure in liquid propellant rocket engines to achieve accurate deep throttleability as an enabler for vehicle reusability and for future planetary exploration missions.Description: Europe is currently developing throttleable engines for use in re-usable space transportation systems. Differently to non-throttleable engines, which can be controlled in open loop based on the calibration obtained via ground tests, an open loop approach is not viable for throttleable engines. Such approach would require extensive ground testing and would not guarantee to robustly cope with varying operating points whereby engine conditions vary rapidly as driven by both internal(especially during transient phases) and external sources. In addition, the closed-loop control of these engines, based on inputs like combustion chamber pressure and controlling outputs such as the throttle valve position, is far from mature in Europe.The purpose of this activity is to demonstrate the feasibility of a throttled engine closedloop control by performing system identification based on high-fidelity models of real-world thrusters and by designing and applying sophisticated control algorithms to those models. Besides fulfilling primary objectives such as thrust and mixture-ratio requirements, the closed-loop controller will also aim at extending the life of the engine through real-time diagnostics and hardware conditions monitoring.The activity encompasses the following tasks: Development of a high-fidelity bi-propellant (including cryogenic) throttleable thruster model simulation (e.g. in EcosimPro, or SimScape, or similar modelling environment), that considers the oxidiser and fuel pressures, mass flow rates, throttle valve orifices, and mixture ratio. The model should be able to simulate highfrequency instability effects such as chugging at low throttle levels. Design of system identification tests, that would permit characterisation of the throttle engine dynamic behaviour necessary to generate suitable dynamic models for control design. The application of model reduction and uncertainty quantification techniques should be investigated. Definition of control requirements, and subsequently design and testing of a closedloop controller using modern robust multiple input multiple output (MIMO) control techniques (dictated by the inherent multivariable nature of the problem). If necessary, the system identification tests will be revised or extended to better capture the engine dynamics, as needed for closed-loop control.