System and method for cylinder power imbalance prognostics and diagnostics
First Claim
1. For an internal combustion engine having a plurality of cylinders and an engine control computer for controlling the operating conditions of each cylinder, a method for the diagnosis and prognosis of engine performance degradation, comprising the steps of:
- conducting a test sequence at each of a plurality of selected engine operating hours/mileages to;
determine the firing times of each of the engine cylinders; and
calculate a differential value [Ci] corresponding to the firing time for each engine cylinder [i] relative to the firing time for the immediately prior cylinder in the engine firing sequence; and
accumulating the differential values for each of the enginecylinders as a function of the number of test sequence conducted; and
calculating a trend parameter for each test sequence based upon the accumulated differential values;
evaluating changes in the trend parameter as an indication of a change in cylinder power balance conditions over a predetermined plurality of the test sequences; and
storing the trend parameter in memory as a function of the number of the test sequence.
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Accused Products
Abstract
A system and method for the diagnosis and prognosis of cylinder power imbalance in an internal combustion engine utilizes cylinder firing times to determine a differential value indicative of the power imbalance. This differential value identifies a cylinder power imbalance condition and can be used in a one dimensional or a two dimensional analysis to predict future engine performance. In one embodiment, a trend parameter is calculated from the differential values over several test sequences at periodic mileage of the vehicle. The rate and magnitude of change or deterioration of the engine performance is indicated by the trend parameter. In another embodiment, a two dimensional trend array is evaluated using singular value decomposition to arrive at an eigenvalue transformation matrix used to obtain two trend variables related to the two principal eigenvalues at a particular engine operating hour/mileage. In one specific embodiment, the two trend variables are converted to polar coordinates in which the polar radius ρ is indicative of the severity of the imbalance condition and the polar angle θ is indicative of the cause or of a change of cause for the engine power imbalance.
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Citations
16 Claims
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1. For an internal combustion engine having a plurality of cylinders and an engine control computer for controlling the operating conditions of each cylinder, a method for the diagnosis and prognosis of engine performance degradation, comprising the steps of:
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conducting a test sequence at each of a plurality of selected engine operating hours/mileages to; determine the firing times of each of the engine cylinders; and
calculate a differential value [Ci] corresponding to the firing time for each engine cylinder [i] relative to the firing time for the immediately prior cylinder in the engine firing sequence; andaccumulating the differential values for each of the engine cylinders as a function of the number of test sequence conducted; and calculating a trend parameter for each test sequence based upon the accumulated differential values; evaluating changes in the trend parameter as an indication of a change in cylinder power balance conditions over a predetermined plurality of the test sequences; and storing the trend parameter in memory as a function of the number of the test sequence. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. For an internal combustion engine having a plurality of cylinders and an engine control computer for controlling the operating conditions of each cylinder, a method for the diagnosis and prognosis of engine performance degradation, comprising the steps of:
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conducting a baseline test sequence including a series of tests to determine the firing times of each of the engine cylinders; for each engine cylinder [i], calculating a vector of cylinder firing time differentials [Ci] relative to the immediately prior cylinder in the engine firing sequence for each test of the baseline test sequence; creating a matrix [X] of firing time differentials with the number of columns corresponding to the number of cylinders and the number of rows corresponding to the number of baseline test; calculating a variance matrix [A] for the matrix [X] of firing time differentials; applying a singular value decomposition to the variance matrix [A] and extracting transformation row vectors [V[1], V[2]] from the eigenvalue transformation matrix [V] corresponding to the two principal eigenvalues [λ
1 and λ
2] developed in the decomposition;storing the transformation vectors in memory in the engine control computer; and applying the transformation vectors to subsequent test sequences to determine the nature and magnitude of degradation of engine cylinder performance at a particular engine operating hour/mileage. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A system for use with an internal combustion engine having a plurality of cylinders and an engine control computer for controlling the operation of each cylinder, the system operable for the diagnosis and prognosis of engine performance degradation and comprising:
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means associated for determining cylinder firing for each cylinder during a test sequence conducted at a plurality of engine operating hours/mileages; time processing unit associated with the engine control computer for calculating a differential firing time value for each cylinder relative to the prior cylinder in the engine firing sequence; and an algorithm processor associated with the engine control computer operable to evaluate the trend of the differential firing time values for each cylinder over the plurality of engine operating hours/mileages, wherein said algorithm processor includes; means for determining a baseline matrix of cylinder firing time differentials generated by said time processing unit for a plurality of cylinder firing tests conducted at a baseline operating condition; means for obtaining an eigenvalue transformation matrix from a variance matrix of said baseline matrix of cylinder firing time differentials; means for mapping the differential firing time values of each cylinder at a current engine operating hour/mileage onto the transformation matrix to derive a pair of trend variables [x(j), j(j)] corresponding to the largest eigenvalues associated with the transformation matrix; and means for comparing the trend variables at the current engine operating hour/mileage with trend variables at prior engine operating hours/mileages and generating a signal indicative of a change in the rate of degradation of the cylinder power imbalance condition. - View Dependent Claims (15, 16)
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Specification