Practical observers for unmeasured states in turbocharged gasoline engines

Turbocharged gasoline engines are becoming more common in production vehicles as consumers demand improved fuel economy with uncompromised performance. Controlling this complex system to meet these and other competing objectives is a challenging task. Knowledge of exhaust manifold pressure and turbocharger speed can be important to success. Physical conditions of the system, however, make measurement impractical and costly, compelling manufacturers to implement some form of on-line estimation. Additional constraints imposed by computational resources and calibration processes limit application of a traditional state observer. In this paper, singular perturbation concepts are employed in concert with the reduced order observer to develop more practical estimates of exhaust manifold pressure and turbocharger speed. Simulation results show excellent observer performance with a significant reduction in calibration complexity.