Brake booster vacuum prediction algorithm and method of use therefor
AssigneeGeneral Motors Corporation
InventorsJames Collins, Robert Nisonger, Christopher Murphy
Life of this patent
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Abstract
An algorithm residing in, for example the ECM of a motor vehicle, which predicts brake booster vacuum for vehicles using vacuum for brake pedal assist. The predicted brake booster vacuum is compared to a calibrated brake booster vacuum threshold to determine if adequate brake booster vacuum is available to meet vehicle braking requirements, whereupon engine operation can be modified, as necessary, to improve intake manifold vacuum such that brake booster vacuum requirements for vehicle braking are better satisfied.
Claims16
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A method for adjusting brake booster vacuum of an engine of a motor vehicle at a brake booster thereof, said method comprising the steps of:
- initially setting a brake booster pressure of the brake booster equal to a predetermined pressure;
- predicting brake booster vacuum;
- determining whether the predicted brake booster vacuum is above a threshold vacuum;
- modifying operation of the engine to lower a brake booster vacuum of the engine if said step of determining determines the predicted brake booster vacuum is above the threshold vacuum;
- and
- periodically repeating said steps of predicting, determining and modifying;
- wherein said step of predicting comprises:
- acquiring predetermined input variables of the motor vehicle, the variables comprising manifold absolute pressure, atmospheric pressure, and brake pedal position;
- determining from the brake pedal position whether an apply brake event of the motor vehicle is occurring;
- determining from the brake pedal position whether a release brake event of the motor vehicle is occurring;
- determining from the brake pedal position whether a no brake event of the motor vehicle is occurring;
- obtaining a change in brake booster pressure as a function of brake pedal position from an apply brake look-up table if the apply brake event is determined as occurring;
- obtaining a change in brake booster pressure as a function of brake pedal position from a release brake look-up table if the release brake event is determined as occurring;
- obtaining a change in brake booster pressure set equal to zero if the no brake vent of the motor vehicle is determined as occurring;
- and
- calculating brake booster vacuum responsive to the obtained change in brake booster pressure.
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Dependencies are inferred from the claim text.