Application of non-linear observers to on-line estimation of indicated torque in automotive engines

Abstract

Estimation of the indicated torque for automotive engines is profitable for evaluation of engine combustion conditions, optimization of engine performance, diagnosis of engine faults and control of automotive transmission. On the basis of the crankshaft-wheel system dynamics of the automotive multicylinder engine without including load torque, this paper describes mainly the application of three non-linear observers to the on-line estimation of indicated torque and analyses the similarities and differences between them. Of all the proposed observers the second-order sliding mode observers are most robust and exact. The classical sliding mode observers are slightly more accurate than the high gain observers, but have the undesired chattering effect. These observers require crank angle and crankshaft speed measurements. Experimental results strongly demonstrate that the on-line estimation techniques of the indicated torque based on non-linear observers are valid, not only for steady state operation but also under transients.