Engine and load torque estimation with application to electronic throttle control

Electronic throttle control is increasingly being considered as a viable alternative to conventional air management systems in modern spark-ignition engines. In such a scheme, driver throttle commands are interpreted by the powertrain control module together with many other inputs; rather than directly commanding throttle position, the driver is now simply requesting torque - a request that needs to be appropriately interpreted by the control module. Engine management under these conditions will require optimal control of the engine torque required by the various vehicle subsystems, ranging from HVAC, to electrical and hydraulic accessories, to the vehicle itself. In this context, the real-time estimation of engine and load torque can play a very important role, especially if this estimation can be performed using the same signals already available to the powertrain control module. In this paper we present two methods to estimate the instantaneous indicated torque, combustion by combustion, and the vehicle load torque; we also present some preliminary results. The first method is based on the reconstruction of the in-cylinder pressure based on the measured engine block vibration. The second one exploits a nonlinear estimation technique, in which the difference between the instantaneous measurement of crankshaft angular velocity and an estimate of the same velocity, based on a model of the engine, forms the input to a sliding-mode observer. Experimental results of both methods have been obtained in an engine test cell on a two-cylinder compression-ignition. Copyright © 1998 Society of Automotive Engineers, Inc.