Model Reference Adaptive Control of a Ball Valve for Hybrid Rocket Throttling Application

Thrust control of rocket engines is a critical technology in rocket system development. A throttling system with good performance improves efficiency of a launch vehicle and may enable the ability to land softly. Most rockets achieved thrust throttling by controlling a valve or venturi. Common control schemes require depth knowledge on the flow characteristics and apply classic linear control theories. In the past, we employed a 'continuous' gain scheduling controller on a ball valve to regulate oxidizer flow rate in hybrid rocket engines. However, it required tremendous effort on modeling and tuning to ensure uniform performance across multi-engine rocket. To circumvent this, a model reference adaptive control (MRAC) technique is derived and investigated in this paper. The adaptive law for control gain adjustment was derived with the well-known MIT rule. The model reference adaptive system (MRAS) was simulated in different scenarios to evaluate its performance. The encouraging results suggest that MRAC has a huge potential for the throttling application in real-world rocket engines.