Adaptive Estimation of the Engine Friction Torque

Errors in an estimate of friction torque in modern spark ignition automotive engines have a direct impact on driveability performance of a vehicle and necessitate a development of real-time algorithms for adaptation of the friction torque. The friction torque in the engine control unit is presented as a look-up table with two input variables (engine speed and indicated engine torque). Algorithms proposed in this paper estimate the friction torque during engine start and idle. Newton's second law for rotational dynamics is used as a reference model during engine start. The friction torque is estimated via a deviation from the reference model. The values of the friction torque at the nodes of the look-up table are updated, if new measured data of the friction torque are available. New recursive and computationally efficient algorithms are developed for adaptation of the nodes of the look-up tables. The algorithms are tested on a Volvo vehicle equipped with a six cylinder prototype engine.