Process for controlling an automatic transmission

A process for controlling an automatic transmission of a vehicle by an electronic transmission control (4), the process comprising the steps of:

• setting a low road friction drive state for the automatic transmission upon detection of one of slip between driven and non-driven gears of the vehicle and active ABS deceleration (ABS=1);
• determining a value by one of:
• evaluating an active ABS deceleration function (S5 to S7), from one of an actual acceleration of the vehicle and a parameter (e.g., gear speed increase) corresponding to the actual acceleration, and
• evaluating a slip determination function (S8 to S10), from one of a comparison between a theoretical acceleration and the actual acceleration a(DIFF) and a parameter (e.g., torque reserve) corresponding to the comparison between the theoretical acceleration and the actual acceleration;
• determining a value offset (Z(OFF) between the value (Z) with respect to a characteristic line and an actual value (Z) is calculated from the value (Z) plus the value offset (Z(OFF)) (Z=Z+Z(OFF));
• and
• activating via the electronic transmission control (4) a winter operation mode (S15) when the actual value (Z) exceeds (Z>Z(IN)) a limit value (Z(IN)).

A process for determining a low road friction drive state for an automatic transmission of a vehicle by an electronic transmission control (4) based solely on an actual and theoretical acceleration of the vehicle, the process comprising the steps of:

• detecting one of slip between driven and non-driven gears of the vehicle and active ABS deceleration (ABS=1);
• determining a frictional resistance value by one of:
• evaluating an active ABS deceleration function (S5 to S7), from one of the actual acceleration of the vehicle and a parameter (e.g., gear speed increase) corresponding to the actual acceleration, and
• evaluating a slip determination function (S8 to S10), from one of a comparison between the theoretical acceleration and the actual acceleration a(DIFF) and a parameter (e.g., torque reserve) corresponding to the comparison between the theoretical acceleration and the actual acceleration;
• and
• activating via the electronic transmission control (4) a winter operation mode (S15) when the value (Z) exceeds (Z>Z(IN)) a limit value (Z(IN)).