Method and apparatus for controlling an internal combustion engine

A method according to claim 6, wherein prior to said perturbing step, said base value determining step includes the steps of:

• determining a first engine operating parameter;
• determining a second engine operating parameter;
• determining a basic value of said engine base value in accordance with a fixed schedule;
• storing correction values for said engine base value as a two-dimensional array as a function of said two engine operating parameters;
• providing a calculated correction value for said two prevailing engine operating parameters, said providing step further including the steps of:
• multiplying each of four correction values stored in a correction schedule at four array points in said two-dimensional array which surround the prevailing engine operating parameters, by respective weighting factors to provide four product values;
• and
• summing said four product values to produce a calculated correction value;
• determining a command value for said engine base value by summing said basic value and said calculated correction value;
• and
• updating said values stored in said correction schedule by the steps of:
• producing a series of error values;
• multiplying each error value by a respective weighting factor for each of said four array points to form four product values;
• and
• using said four product values to update said correction values stored in said four array points;
• said weighting factors being determined by the steps of:
• forming a main rectangle whose corners lie on said four array points surrounding said prevailing engine operating parameters;
• dividing said main rectangle into four sub-rectangles by an ordinate and abscissa which pass through said prevailing engine operating parameters;
• and
• calculating said weighting factor for each array point in dependence upon the area of the diagonally opposite sub-rectangle.

A method of operating an internal combustion engine at a prevailing engine speed and load demand, said method comprising the steps of:

• varying combustion initiation timing;
• detecting engine output variations which result from said combustion initiation variations;
• determining any error between said detected engine output variations and predicted engine output variations for said prevailing engine speed and load demand;
• and
• based upon any determined error, adjusting an engine input other than combustion initiation timing to reduce said error to a desired level.

An apparatus for controlling a power producing engine, said engine having at least two inputs, each of which affect an engine output, said apparatus comprising:

• means for periodically perturbing one of said inputs about a baseline value, said baseline value related to engine operating conditions;
• means for monitoring said engine output;
• means for determining the slope of engine output with respect to said one input;
• and
• means for controlling said other input so as to obtain a desired value of said slope.

An apparatus for controlling an internal combustion engine at a prevailing engine speed and load demand, said apparatus comprising:

• means for varying combustion initiation timing;
• means for detecting engine output variations which result from combustion initiation variations;
• means for determining any error between said engine output variations and predicted engine output variations for said prevailing engine speed and load demand;
• means, responsive to any determined error, for adjusting an engine input other than combustion initiation timing and for reducing said error to a desired level.

An apparatus for controlling an internal combustion engine, at a prevailing engine speed and load demand, said engine having a fuel input, an ignition input, an engine speed output and an engine load demand output, said apparatus comprising:

• spark advance means, responsive to said engine speed and load demand outputs, for providing an output indicative of a desired spark advance for said engine speed and load demand;
• fuel demand means, responsive to said engine speed and load demand outputs, for providing an output indicative of a desired fueling for said engine speed and load demand;
• slope demand means, responsive to said engine speed and load demand outputs, for providing an output indicative of a desired slope (change in engine speed per change in ignition timing) at said engine speed and load;
• perturbation generator means for generating a perturbation signal;
• first summer means for combining said perturbation signal with said spark advance means output;
• ignition means, responsive to said first summer means output and said engine speed output, for providing said engine ignition input;
• slope detector means, responsive to said engine speed output and said perturbation signal, for providing an actual slope output;
• second summer means, responsive to said actual slope output and said slope demand means output, for providing a slope error output;
• controller means, responsive to said slope error output, for providing a modified error output;
• third summer means, responsive to said integrated error output and said fuel demand means output, for providing a combined fuel output;
• and
• fuel means, responsive to said engine speed output and said combined fuel output, for providing said engine fuel input and for reducing said slope error to a desired level.