Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant
Reexamination Certificate
1999-10-26
2001-04-24
Wolfe, Willis R. (Department: 3747)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
With indicator or control of power plant
C701S115000, C701S102000
Reexamination Certificate
active
06223120
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to methods and apparatus for estimating cylinder torque in a system including a multi-cylinder engine and, more particularly, to a method and apparatus for estimating such cylinder torque based on system angular response measurements and a mathematical model of the system.
2. Description of the Prior Art
The estimation of cylinder torque in a multi-cylinder engine provides insight into the performance and health of each cylinder in the engine. Several related prior art methods have been developed for estimating cylinder torque based on system angular response measurements and a mathematical model of the system. A survey of such prior art methods is provided by Jeremy Williams in “An Overview of Misfiring Diagnostic Techniques Based on Crankshaft Angular Velocity Measurements”, SAE 960039, in Electronic Engine Controls 1996 SP-1149, SAE International Congress and Exposition, Detroit, Mich., Feb. 26-29, 1996. incorporated herein by reference.
In essence, all of the related prior art methods have the following elements in common:
1. Develop a mathematical model representing the angular dynamics of the system;
2. Measure the angular response at one or more places in the system; and
3. Use the measured angular response and the mathematical model to calculate the system inputs.
U.S. Pat. No. 4,843,870 to Citron et. al., incorporated herein by reference, uses measured crankshaft angular velocity and a system model to calculate the indicated torque waveform applied by the engine cylinders. Although the Citron et al. patent teaches a reconstruction of engine torque from the measurement of angular velocity, it fails to recognize that the crankshaft is a rather flexible body under certain conditions, particularly in multi-cylinder engines operating at medium and high engine speeds. Since the system model does not allow for crankshaft torsional deflection, the method is limited by the conditions under which the rigid crankshaft assumption is valid.
U.S. Pat. No. 5,771,482 to Rizzoni, incorporated herein by reference, uses measured crankshaft angular velocity and a system model to calculate the indicated torque waveform applied by the engine cylinders. Rizzoni teaches a first method in which the crankshaft is modeled as two lumped inertias connected by a flexible element. However, this method does not fully model the dynamic torsional flexibility in the crankshaft. Since the system model does not allow for crankshaft torsional deflection between each crank throw, the method has limited use under conditions in which dynamic deflection in the crankshaft between each cylinder is significant.
In a second method, Rizzoni models the crankshaft as fully flexible, with a flexible element between each crankshaft throw. In engines in which the number of cylinders is greater than the number of angular response measurement locations, the number of unknown system inputs is greater than the number of known outputs. In such a case, Rizzoni teaches using a least squares, pseudo-inverse technique to solve for the unknown cylinder torque inputs at a single frequency. However, since the equation set relating the known outputs to the unknown inputs is rank deficient, the pseudo-inverse approach taught by Rizzoni does not accurately estimate the individual cylinder inputs.
SUMMARY OF THE INVENTION
The present invention relates generally to methods and forms of apparatus for estimating cylinder torque in multi-cylinder engines using the measured angular response of the system in combination with a mathematical model of the system dynamics. A fundamental challenge with all such methods is that the equation set relating the known angular responses to the unknown cylinder torque inputs is rank deficient as long as the number of unknown inputs is greater than the number of measured system responses.
The present invention provides a novel method and apparatus for cylinder torque estimation that offers significant advantages over the related prior art. Cylinder torque is parameterized as a function of at least one parameter for each cylinder. Angular response is measured at one or more places in the system to define at least one measured angular response. A set of frequency domain equations is developed relating the at least one measured angular response to the at least one parameter for each cylinder. At any selected analysis frequency, this equation set is under-determined, i.e. rank deficient.
A plurality of selected analysis frequencies are considered simultaneously, which results in a plurality of sets of frequency domain equations which are defined as over-determined. Each set of frequency domain equations relates the at least one measured angular response to the at least one parameter for each cylinder at the selected analysis frequency. These over-determined plurality of equation sets are solved simultaneously for the parameters for each cylinder using a least squares approach. The resulting parameters are used to estimate the torque contributed by each cylinder. In the specific case in which the chosen cylinder parameter is the indicated mean effective pressure (IMEP), the parameter is a direct measure of the torque contributed by each cylinder.
The method and apparatus of the present invention have been developed in a general form applicable to a wide variety of engines in a wide variety of applications. Analysis has shown that the method is valid for all engine types in general, and for four, six, and sixteen cylinder engines in particular. The analysis verifies that the method does not apparently place any restrictions on the maximum amount of crankshaft angular deflection between cylinders. Finally, the method and apparatus of the present invention have been built, tested, and experimentally verified using data taken on a heavy-duty six cylinder diesel engine. The experimental data shows that the new method is successful under a variety of conditions, particularly those in which there is large torsional deflection in the crankshaft. This experimental data further demonstrates that the present invention provides accurate estimation of cylinder torque under engine conditions in which prior art methods provide results of questionable accuracy.
Therefore, it is an object of the present invention to provide a method and apparatus for estimating with improved accuracy the torque produced by each of a plurality of cylinders in a reciprocating machine.
It is a further object of the present invention to provide such a method and apparatus which accounts for angular deflection between the plurality of cylinders.
It is another object of the present invention to provide such a method and apparatus for parameterizing the torque produced by each cylinder as a function of at least one parameter.
It is still yet another object of the present invention to provide such a method and apparatus for considering simultaneously a plurality of sets of frequency domain equations relating the measured angular response to the at least one parameter at a plurality of selected analysis frequencies.
Other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.
REFERENCES:
patent: 4532592 (1985-07-01), Citron et al.
patent: 4697561 (1987-10-01), Citron
patent: 4843870 (1989-07-01), Citron et al.
patent: 5200899 (1993-04-01), Ribbens et al.
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patent: 5249558 (1993-10-01), Imamura
patent: 5269271 (1993-12-01), Kawai et al.
patent: 5278760 (1994-01-01), Ribbens et al.
patent: 5377537 (1995-01-01), James
patent: 5528931 (1996-06-01), James et al.
patent: 5592386 (1997-01-01), Gaultier
patent: 5646340 (1997-07-01), Gee et al.
patent: 5771482 (1998-06-01), Rizzoni
patent: 5774823 (1998-06-01), James et al.
patent: 5794171 (1998-08-01), Bryant et al.
patent: 5921221 (1999-07-01), Davis, Jr. et al.
patent: 60-8429 (1985-01-01), None
Ribbens, W.B., “A New Metric for Torque Nonuniformity”, SAE Paper No. 830425, in SAE SP-540,Electronic Engine
Biebel & French
Wolfe Willis R.
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