ADAPTIVE THERMODYNAMIC ENGINE MODEL FOR THE NEXT GENERATION CONTROL SYSTEM FOR HELICOPTER ENGINES

An adaptive thermodynamic engine model has been developed as part of a United States Army-sponsored development program of an advanced control system for turbo-shaft engines. An embedded engine model in the Electronic Control Unit that is constantly adapted to reflect engine deterioration provides a powerful tool for accurately estimating the maximum power available from the engine. In addition, the adaptive engine model provides real-time estimates for engine speed, pressure and temperature for back up control in case of sensor failure. Adaptation of the model is performed by modifying component efficiencies to match measured engine parameters (shaft power, compressor discharge pressure, power turbine inlet temperature, engine speed) with model computed counterparts at a number of steady state operating conditions. As part of the algorithm, calibration curves for measured fuel flow and Inlet Guide Vane position are automatically generated to effectively cancel errors due to tolerances and fuel property variations. The adaptation process is posed as a non-linear least squares minimization problem which is numerically solved using a quasi-Newton method. This paper outlines the adaptation algorithm along with some numerical results when operating with a real time computer simulation of the Sikorsky BLACK HAWK helicopter and Pratt & Whitney Canada 3000 SHP engines.