Patent ID: 8249786

Claim:
A control apparatus for an automatic transmission, comprising: a shift control section configured to perform a shift of the automatic transmission by engaging a first friction-engagement element which is in a released state, and by releasing a second friction-engagement element which is in an engaged state; and a judder judging section configured to judge an occurrence of a judder due to self-excited vibration; wherein the shift control section includes an inertia-phase determining section configured to judge whether or not a progress of the shift is during an inertia phase, the inertia phase being one of phases each representing a degree of shift progress under a shift control, an input speed of the automatic transmission being varied for the inertia phase; wherein the judder judging section is configured: to calculate a characteristic-gradient index value, the characteristic-gradient index value being a value obtained by quantifying a phenomenon that appears as a relative rotational speed of input and output of the first friction-engagement element becomes reduced with a progress of the inertia phase, the phenomenon appearing in a different way in dependence upon whether a relational characteristic of a friction coefficient of the first friction-engagement element with respect to the relative rotational speed is a positive-gradient characteristic or a negative-gradient characteristic, and to determine that the judder has occurred, when the characteristic-gradient index value indicates that the phenomenon has appeared due to the negative-gradient characteristic.