MODELING AND ESTIMATION FOR ELECTROMECHANICAL THRUST VECTOR CONTROL OF ROCKET ENGINES

Increased use of electromechanical actuators (EMA) in high-power, flig ht-critical applications where hydraulics have traditionally been empl oyed has increased the need for accurate, measurable models of the EMA -load systems. Thrust vector control (TVC) of rocket engines is such a n application. An intuitive, linearized model of a TVC-EMA system is p resented along with practical and accurate methods of estimating the m odel parameters. The estimation techniques are a combination of calcul ations using engineering design data and of experiments based on first principles that are designed to isolate the effects of specific param eters and/or combinations of parameters. The techniques use measuremen ts that are commonly available in an EMA system and inputs that are ea sily generated with either a computer or signal generator. The validit y of the model and the parameter estimation techniques are experimenta lly verified with a pendulum simulator of a rocket engine and an EMA d esigned for TVC.;Nonlinearities are discussed and simulated, and reson ance shifting caused by backlash is demonstrated with experimental dat a.