Fuzzy logic shift scheduling for automatic transmissions

The method of producing shift signals in an automatic transmission driven by an engine having a governed speed, comprising the steps of:

• acquiring transmission output speed and throttle position signals;
• deriving an acceleration value from the output speed;
• setting a plurality of upshift values and downshift values which are fixed percentages of the governed speed;
• establishing membership functions for positive and negative acceleration and for throttle position;
• determining the degree of membership in each membership function for current acceleration and throttle position values;
• weighting upshift values and downshift values according to rules employing the degree of membership in selected membership functions;
• calculating shift points in accordance with said weighted values;
• and
• producing a shift signal in accordance with the relation of the speed signal to said shift points by calculating an upshift range speed from the output speed and the current gear ratio and producing an upshift signal when the upshift range speed is greater than the upshift point;
• and calculating a downshift range speed from the output speed and the gear ratio for the next lower range, and producing a down shift signal when the downshift range speed is less than the downshift point.

The method of producing shift signals in an automatic transmission driven by an engine having a governed speed, comprising the steps of:

• acquiring transmission output speed and throttle position signals:
• deriving an acceleration value from the output speed;
• setting a plurality of upshift values and downshift values which are fixed percentages of the governed speed;
• storing sets of upshift and downshift values for at least two different modes of operation;
• selecting a set of said values for a desired mode of operation;
• establishing membership functions for positive and negative acceleration and for throttle position;
• determining the degree of membership in each membership function for current acceleration and throttle position values;
• weighting upshift values and downshift values according to rules employing the degree of membership in selected membership functions;
• calculating shift points in accordance with said weighted values;
• and
• producing a shift signal in accordance with the relation of the speed signal to said shift points.

In an automatic transmission having a torque converter and a lockup clutch, the method of producing shift signals using fuzzy inference and for controlling the lockup clutch by producing apply and release signals comprising the steps of:

• acquiring transmission output speed and throttle position signals;
• deriving an acceleration value from the output speed;
• setting a plurality of upshift values and downshift values;
• establishing membership functions for positive and negative acceleration and for throttle position;
• determining the degree of membership in each membership function for current acceleration and throttle position values;
• weighing upshift values and down shift values according to rules employing the degree of membership in selected membership functions;
• calculating shift points in accordance with said weighted values;
• producing a shift signal in accordance with the relation of the speed signal to the calculated shift points;
• controlling the lockup clutch by determining whether torque multiplication is being produced by the converter on the basis of engine speed, output speed and acceleration, controlling the lockup clutch on in the absence of such multiplication and controlling the lockup clutch off when multiplication occurs, and producing a clutch release signal when the current transmission range is equal to the lowest allowable range for lockup and the throttle position has a given relationship to one of the throttle position membership functions and the engine speed is less than a learned turbine speed calculated when the throttle position is in the range of a very large throttle position membership function and the converter speed ratio is in a calibrated torque multiplication window, and the learned turbine speed is equal to a percentage of the current turbine speed combined with a percentage of the previous learned turbine speed, the sum of the percentages being 100 percent.

In an automatic transmission having a torque converter and a lockup clutch, the method of producing shift signals using fuzzy inference and for controlling the lockup clutch by producing apply and release signals comprising the steps of:

• acquiring transmission output speed and throttle position signals;
• deriving an acceleration value from the output speed;
• setting a plurality of upshift values and downshift values;
• establishing membership functions for positive and negative acceleration and for throttle position;
• determining the degree of membership in each membership function for current acceleration and throttle position values;
• weighing upshift values and down shift values according to rules employing the degree of membership in selected membership functions;
• calculating shift points in accordance with said weighted values;
• producing a shift signal in accordance with the relation of the speed signal to the calculated shift points;
• controlling the lockup clutch by determining whether torque multiplication is being produced by the converter on the basis of engine speed output speed, and acceleration, controlling the lockup clutch on in the absence of such multiplication and controlling the lockup clutch off when multiplication occurs, and producing a clutch release signal when the current transmission range is equal to the lowest allowable range for lockup, the throttle position is at nearly full throttle, and the engine speed is less than a learned turbine speed;
• and wherein the learned turbine speed is calculated when the throttle is at nearly full throttle and the converter speed ratio is in a calibrated torque multiplication window, and is updated by summing weighted values of the current turbine speed and a previously learned turbine speed.