Acceleration based shift strategy for an automatic transmission

A method of adaptively controlling transmission gear downshifts in an automatic transmission of a vehicle, said method comprising the steps of:

• determining output torque of an automatic transmission;
• determining a learned vehicle inertia;
• determining if a current acceleration of said vehicle is less than a downshift acceleration threshold and, if so, determining a projected gear based on said determined torque output, calculating projected acceleration based on said learned vehicle inertia and said proiected gear, and determining if said projected acceleration is greater than said downshift acceleration threshold;
• if said projected acceleration is greater than said downshift acceleration threshold, then determining if a shift can be made which is within an allowable shift zone and, if so, executing said shift.

A method of adaptively controlling transmission gearshifts in an automatic transmission of a vehicle, said method comprising the steps of:

• determining output torque of an automatic transmission;
• determining a learned vehicle inertia;
• determining if a current acceleration is less than a downshift acceleration threshold and, if not, obtaining an upshift acceleration threshold based on vehicle speed, a throttle opening of a throttle of said vehicle and said learned vehicle inertia;
• selecting possible upshifts one at a time from an upshift hierarchy table in an ordered sequence;
• predicting an expected post upshift acceleration for the selected one of the upshifts from the upshift hierarchy table;
• comparing the predicted post upshift acceleration of the selected upshift to an upshift threshold value;
• initiating a transmission upshift to the selected upshift when the predicted post upshift acceleration exceeds the upshift threshold value;
• selecting possible downshifts one at a time from a downshift hierarchy table in an ordered sequence;
• predicting an expected post downshift acceleration for the selected one of the downshifts from the downshift hierarchy table;
• comparing the predicted post downshift acceleration to a downshift threshold value;
• and
• initiating a transmission downshift to the selected downshift when the predicted post downshift acceleration value is greater than the downshift threshold value.