Shift control system for automatic transmission based on fuzzy control

A system for controlling a speed change ratio shifting operation of an automatic transmission for an automotive vehicle, comprising:

• means for inferring a driving force required by a driver of said automotive vehicle;
• means for inferring a driving force after the speed change ratio shifting operation of said automatic transmission for each speed change ratio which is obtainable by said speed change ratio shifting operation of said automatic transmission;
• means for calculating a deviation between said driving force required by the diver and said driving force after the speed change ratio shifting operation as a first parameter for said each speed change ratio;
• means for calculating a given condition of said automotive vehicle as a second parameter value for said each speed change ratio;
• means for determining membership values of said first and said second parameters in accordance with membership functions of said first and second parameters for said each speed change ratio, selecting an optimum speed change ratio based on said membership values of said first and said second parameters for said each speed change ratio, and producing an output signal corresponding to said optimum speed change ratio;
• and
• means, responsive to said output signal, for controlling said speed change ratio shifting operation of said automatic transmission to achieve said optimum speed change ratio.

In a shift control system for an automatic transmission of an automotive vehicle based on fuzzy control, a method for controlling a speed change ratio shifting operation comprising the steps of:

• (a) producing a signal representative of a driving force required by a driver of said automotive vehicle;
• (b) producing a signal representative a driving force after a speed change ratio shifting operation;
• (c) producing a signal representative of a deviation between the signal representative of the driving force required by the driver and the driving force after the speed change ratio shifting operation;
• (d) producing a signal representative of a given condition of said automotive vehicle;
• (e) repeating steps (b)-(d) for each speed change ratio obtainable by said shift control system;
• and
• (f) producing for said each speed change ratio signals corresponding to membership values derived from membership functions of the deviation and the given condition of said automotive vehicle;
• (g) selecting an optimum speed change ratio based on said signals corresponding to said membership values;
• and
• (h) controlling said speed change ratio shifting operation of said automatic transmission to achieve said optimum speed change ratio.