Adaptive control system for an internal combustion engine

Claim 2

An adaptive control system for an internal combustion engine (l0), said control system comprising: means (30) for determining the engine speed; means (3l) for determining the load demand to which the engine (l0) is subjected; characterised in that the system further comprises means (36) for determining a basic value or a series of basic values for a particular engine control parameter in accordance with a fixed schedule (35); a correction schedule (38) in which correction values for said particular control parameter are stored as a two dimensional array as a function of engine speed and load demand; means (39) for providing a calculated correction value for the prevailing engine speed and load demand, said means multiplying each of the correction values stored in the correction schedule (39) at the four array points in the speed/load plane which surround the prevailing engine speed and load demand by a respective weighting factor to provide product values and then summing the four product values to produce a calculated correction value; means (37) for determining a command value for said particular control parameter by summing a respective basic value and a respective calculated correction value; and means (47) for updating the values stored in the correction schedule (38), said updating means (47) producing a series of error values, multiplying each error value by a respective weighting factor for each of the four array points which surround the prevailing engine speed and load demand to form four product values, and using said four product values to update the correction values stored at said four array points; said weighting factors being determined by forming a main rectangle whose corners lie on the four array points surrounding the prevailing speed and load demand, dividing said main rectangle into four sub-rectangles by the ordinate and abscissa which pass through the prevailing speed and load demand point, and calculating the weighting factor for each array point in dependence upon the area of the diagonally opposite sub-rectangle.

Claim 3

An adaptive control system as claimed in Claim l, characterised in that the weighting factor for each array point is calculated by dividing the area of the diagonally opposite sub-rectangle by the area of the main rectangle.

Claim 4

An adaptive control system as claimed in Claim l or Claim 2, characterised in that said updating means (47) updates the correction value stored at each array point by multiplying a respective product value by a constant and adding the resulting value to the correction value presently stored at the array point.

Claim 5

An adaptive control system as claimed in any one of the preceding claims, characterised in that fixed values for said particular control parameter are stored in said fixed schedule (35) as a two dimensional array as a function of engine speed and load demand, and each basic value of said particular control parameter is determined for the value stored at the four array points in the speed/load plane which surround the prevailing speed and load demand, said particular control parameter at each point being multiplied by a respective weighting factor to form a product value and the four product values being summed to produce the basic value, said weighting factors being determined in the same manner as for the correction schedule.

Claim 6

An adaptive control system as claimed in any one of the preceding claims, characterised in that the system further comprises means (40, 4l, 43, 44, 45, 46) for determining a series of values for the slope of engine output with respect to a certain engine control parameter, each such value corresponding to the prevailing engine speed and load demand, said certain and particular parameters being the same parameter or different parameters, and said updating means comparing each slope value with a predetermined value to produce said series of error values.

Claim 7

An adaptive control system as claimed in claim 5, characterised in that the internal combustion engine (l0) has a flywheel (ll)connected through resilient shafting (l2, l4) and a gear arrangement (ll) to a load (l5), said flywheel (ll), resilient shafting (l2, l4) and gear arrangement (l3) forming a resonant system which has a particlar resonant frequency for each gear ratio established by said gear arrangement (l3); said system further includes a position transducer (l6) for detecting the passage of the engine crankshaft past at least one reference point during each engine fire period; and said slope determining means comprises: a perturbation generator (40) for generating a periodic perturbation waveform, said perturbation generator (40) producing a positive perturbation value for said certain control parameter during the first part of each period of the pertubation waveform and a negative perturbation value for said certain control parameter during the second part of each period of the perturbation waveform, each period of said waveform being equal to a whole number of engine fire periods and the frequency of said waveform being greater than three quarters of the highest resonant frequency of the resonant system; means (43) for creating at least one series of contiguous positive and negative measurement windows associated with respective first and second parts of each period of said perturbation waveform, each measurement window lagging its respective part of a period of the perturbation waveform by a predetermined phase shaft; a first accumulator (44) for accumulating for each positive measurement window the individual fire periods whose central points fall within said positive window to produce a total fire period for said positive window; a second accumulator (45) for accumulating for each negative measurement window the individual fire periods whose central points fall within said negative window to produce a total fire period for said negative windows; and means (46) for calculating a series of values for the slope of engine output with respect to said certain control parameter from said total fire periods accumulated in said first and second accumulators (44, 45).

Claim 8

An adaptive control system as claimed in claim 5 or claim 6, characterised in that said certain control parameter is an ignition timing parameter.

Claim 9

An adaptive control system as claimed in Claim 7, characterised in that said engine (l0) is a spark ignition engine, and said certain control parameter is the spark advance angle.

Claim 10

An adaptive control system as claimed in any one of the preceding claims in which said particular control parameter is a mixture control parameter.

Claim 11

l0. An adaptive control system for a power producing device, said control system comprising means (30, 3l) for determining the prevailing operating conditions of the device; characterised in that the system further includes a schedule (38) in which values relating to a particular control parameter are stored as a two dimensional array as a function of the prevailing operating conditions; means (39) for calculating a value relating to said particular control parameter for the prevailing operating conditions, said means (39) multiplying each of the values stored in said schedule (38) at a set of array points which surround the prevailing operating point by a respective weighting factor to provide product values, and then summing the product values to produce a calculated value; and means (46) for updating the values stored in said schedule (38), said updating means producing a series of error values, multiplying each error value by a respective weighting factor for each of a set of array points which surround the prevailing operating point to form a set of product values, and using said set of product values to update the values stored at said set of array points; said set of array points used by the calculating means (39) and said set of array points used by the updating means (47) being similar, and the weighting factors used in the calculating means (39) and the weighting factors used in the updating means (47) being determined in a similar manner.

Claim 12

l0. An adaptive control system for a power producing device, said control system comprising means (30, 3l) for determining the prevailing operating conditions of the device; characterised in that the system further includes a schedule (38) in which values relating to a particular control parameter are stored as a two dimensional array as a function of the prevailing operating conditions; means (39) for calculating a value relating to said particular control parameter for the prevailing operating conditions, said means (39) multiplying each of the values stored in said schedule (38) at a set of array points which surround the prevailing operating point by a respective weighting factor to provide product values, and then summing the product values to produce a calculated value; and means (46) for updating the values stored in said schedule (38), said updating means producing a series of error values, multiplying each error value by a respective weighting factor for each of a set of array points which surround the prevailing operating point to form a set of product values, and using said set of product values to update the values stored at said set of array points; said set of array points used by the calculating means (39) and said set of array points used by the updating means (47) being similar, and the weighting factors used in the calculating means (39) and the weighting factors used in the updating means (47) being determined in a similar manner.

Claim 17

A method as claimed in Claim 9 or Claim l0, characterised in that said cerain control parameter is an ignition timing parameter.