Patent ID: 6354149
Filing Date: 2002-03-12
Classification: F02D,G01M

Abstract:
A method for determining a progression of load torque in an internal-combustion engine having at least one crankshaft, intake manifold, piston, and cylinder during a combustion cycle having an ignition phase, the method comprising the steps of:detecting a progression of instantaneous angular velocity (v(t)) of the crankshaft of the engine; determining an existing operating point (K) of the engine as a function of a set of operating parameters of the engine; obtaining a progression of pressure (P(t)) inside the cylinder from the progression of the instantaneous angular velocity (v(t)) and from a transfer function (H(j&OHgr;m)) that relates to the existing operating point (K) and correlates the pressure (P(t)) inside the cylinder to the instantaneous angular velocity (v(t)); determining a progression of load torque (Tc(t)) as a function of the progression of the instantaneous angular velocity (v(t)) and the progression of the said internal pressure (P(t)), wherein determining a relevant transfer function (H(j&OHgr;m)) for each operating point comprises the preliminary steps of: determining a plurality of reference operating points (R) of the engine, each of the plurality of reference operating points being a function of the operating parameters of the engine, and determining, for each of the plurality of reference operating points (R), a respective reference transfer function (HR(j&OHgr;m)) for the pressure (P(t)) inside the cylinder and the instantaneous angular velocity (v(t)) of the crankshaft, and wherein the transfer function (H(j&OHgr;m)) for the internal pressure (P(t)) and the said instantaneous angular velocity (v(t)) of the crankshaft at the existing operating point (K) of the engine is calculated by processing at least some of the reference transfer functions (HR(j&OHgr;m)) relating to reference operating points (R) which are closest to the existing operating point (K); obtaining a progression of the torque (Tt(t)) transmitted to the crankshaft from the progression of the pressure (P(t)) inside the cylinder; assigning a trial load torque (Tcst) to a first input of a block that models the dynamic behavior of a system defined by a combination of engine and load, the block having a second input receiving the torque (Tt(t)) transmitted to the crankshaft; estimating, using the block, an angular velocity of the crankshaft (Vst) as a function of the trial load torque (Tcst) and the torque (Tt(t)) transmitted to the crankshaft, the estimated angular velocity being a velocity at which the crankshaft should travel in order to balance the transmitted torque (Tt(t)) with the trial load torque (Tcst); comparing the measured angular velocity (v) with the estimated angular velocity (Vst) and generating a velocity error signal (&Dgr;v); correcting the trial load torque (Tcst) by means of an estimator circuit which receives at its input the velocity error signal (&Dgr;v) and estimates the load torque (Tcst) based the velocity error signal (&Dgr;v); and repeating the above steps of estimating, comparing and generating, and correcting until the velocity error signal (&Dgr;v) is approximately equal to zero so that the trial load torque (Tcst) outputted by the estimator circuit is approximately equal to the load torque actually applied to the engine.