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 the use of an observer is often necessary for the realization of the controller. In this paper, a discrete-time observer design for a combustion engine test bench is proposed. Euler discrete-time model is used for the construction. The observer is a partial state observer, used to estimate the torqe 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 then used for constructing an output feedback controller which is used 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 dynamic observer which are possible to construct using the same approach, is also presented.