Discrete-time nonlinear observer and output feedback design for a combustion engine test bench

Combustion engine control design depends strongly on the availability and the quality of the measurement of quantities involving in the controller construction. In general, not all quantities are available through direct measurement, and therefore an observer is often necessary to realize the controller. In this paper, a discrete-time partial state observer design for a combustion engine test bench is proposed. The observer is used to estimate the torque and the torsion angle of the engine, based on the measurement of the engine and the dynamometer speeds. The convergence of the observer is shown, and separation principle is also proved. The observer is used for constructing an output feedback controller for set point tracking of the test bench. Some numerical simulations are performed, showing the performance of the observer and also comparing the performance of the output feedback controller with the state feedback controller. A discussion, comparing a so called "static observer" and a "dynamic observer" which are possible to construct using the same approach, is also presented.