Method of feedback controlling engine idle speed

Claim 1

A method of feedback controlling engine idle speed to a target speed on the basis of mathematical dynamic models to determine engine state variables representative of engine dynamic behavior, which comprises the following step of: (a) calculating the differences SA between the target engine idle speed N r and current engine speeds N; (b) integrating the calculated idle speed differences SA to obtain integral value DUN of speed differences; (c) selecting an appropriate mathematical engine dynamic model according to at least one of predetermined engine operating conditions; (d) estimating low-order variables x i representative of engine internal dynamic states in accordance with the selected dynamic model and on the basis of at least one or two or more combinations of preceding increments of engine idle speed controlling parameters δP A , δIT and controlled engine idle speed δN; (e) selecting an appropriate gain K according to external engine load conditions; and (f) determining increments of engine idle speed controlling parameters δP A , δIT on the basis of the estimated state variables x i , the selected gain K, and the integrated idle speed difference DUN, whereby engine idle speed is feedback controlled in accordance with low-order engine dynamic state variables.

Claim 2

A method of feedback controlling engine idle speed to a target speed on the basis of mathematical dynamic models to determine engine state variables representative of engine dynamic behavior, which comprises the following step of: (a) calculating the differences SA between the target engine idle speed N r and current engine speeds N; (b) integrating the calculated idle speed differences SA to obtain integral value DUN of speed differences; (c) selecting an appropriate mathematical engine dynamic model according to at least one of predetermined engine operating conditions; (d) estimating low-order variables x i representative of engine internal dynamic states in accordance with the selected dynamic model and on the basis of at least one or two or more combinations of preceding increments of engine idle speed controlling parameters δP A , δIT and controlled engine idle speed δN; (e) selecting an appropriate gain K according to external engine load conditions; and (f) determining increments of engine idle speed controlling parameters δP A , δIT on the basis of the estimated state variables x i , the selected gain K, and the integrated idle speed difference DUN, whereby engine idle speed is feedback controlled in accordance with low-order engine dynamic state variables.

Claim 20

A method of feedback controlling engine idle speed to a target speed on the basis of mathematical dynamic models to determine engine state variables representative of engine dynamic behavior, which comprises the following steps of: (a) detecting an engine speed when a throttle valve is fully closed; (b) detecting that engine idle speed N drops below a predetermined idle speed N* at which engine idle speed control starts; (c) if the throttle valve is fully closed and further the engine idle speed N drops below a predetermined control start value N*, determining an initial value DUN(0) of integral DUN of speed difference SA between target engine speed value N r and detected engine speed value N, and initial values x 1 (0) to x 4 (0) of engine dynamic state variables in two dimensional table look-up method, when idle speed control starts; (d) selecting an appropriate engine internal dynamic model according to engine operating conditions, and an appropriate control gain K according to engine load conditions; (e) calculating an appropriate target engine idle speed N r according to engine operating conditions; (f) detecting that engine speed N exceeds the calculated target value N r and idle speed controlling values δP A , δIT are fixed at lower limits; (g) if engine speed N drops below the target value N r from the state where engine speed N exceeds the calculated target value N r and the idle speed controlling values are fixed at the lower limits, cancelling all the values of integral DUN, estimated variables x 1 to x 4 , and calculated increments of speed controlling parameters δP A , δIT and setting all the cancelled values to reference values, respectively; (h) if engine speed N does not drop below the target value N and the idle speed controlling values are not fixed at the lower limits, calculating difference SA between the target engine speed value N r and the detected engine speed N; (i) integrating the difference SA to obtain DUN by the use of the determined initial value DUN(0); (j) calculating engine speed perturbation δN from designed reference engine speed value Na; (k) estimating state variables x 1 to x 4 in accordance with the selected engine dynamic model and on the basis of the preceding estimated state variables x 1 * to x 4 *, the calculated engine speed perturbation δN; and the preceding engine speed controlling values δP A , δIT; and (1) calculating increments of engine controlling values δP A , δIT on the basis of estimated state variables x 1 to x 4 , the calculated speed difference integral DUN and the selected gain K.

Claim 21

A method of feedback controlling engine idle speed to a target speed on the basis of mathematical dynamic models to determine engine state variables representative of engine dynamic behavior, which comprises the following steps of: (a) detecting an engine speed when a throttle valve is fully closed; (b) detecting that engine idle speed N drops below a predetermined idle speed N* at which engine idle speed control starts; (c) if the throttle valve is fully closed and further the engine idle speed N drops below a predetermined control start value N*, determining an initial value DUN(0) of integral DUN of speed difference SA between target engine speed value N r and detected engine speed value N, and initial values x 1 (0) to x 4 (0) of engine dynamic state variables in two dimensional table look-up method, when idle speed control starts; (d) selecting an appropriate engine internal dynamic model according to engine operating conditions, and an appropriate control gain K according to engine load conditions; (e) calculating an appropriate target engine idle speed N r according to engine operating conditions; (f) detecting that engine speed N exceeds the calculated target value N r and idle speed controlling values δP A , δIT are fixed at lower limits; (g) if engine speed N drops below the target value N r from the state where engine speed N exceeds the calculated target value N r and the idle speed controlling values are fixed at the lower limits, cancelling all the values of integral DUN, estimated variables x 1 to x 4 , and calculated increments of speed controlling parameters δP A , δIT and setting all the cancelled values to reference values, respectively; (h) if engine speed N does not drop below the target value N and the idle speed controlling values are not fixed at the lower limits, calculating difference SA between the target engine speed value N r and the detected engine speed N; (i) integrating the difference SA to obtain DUN by the use of the determined initial value DUN(0); (j) calculating engine speed perturbation δN from designed reference engine speed value Na; (k) estimating state variables x 1 to x 4 in accordance with the selected engine dynamic model and on the basis of the preceding estimated state variables x 1 * to x 4 *, the calculated engine speed perturbation δN; and the preceding engine speed controlling values δP A , δIT; and (1) calculating increments of engine controlling values δP A , δIT on the basis of estimated state variables x 1 to x 4 , the calculated speed difference integral DUN and the selected gain K.