Patent ID: 7572203

Claim:
An automatic transmission system for a vehicle having an internal combustion engine, the automatic transmission system comprising: an automatic transmission apparatus that changes a rotational speed of the engine and outputs the changed rotational speed of the engine toward wheels of the vehicle; an automatic transmission (AT) controller that controls gear change in the automatic transmission apparatus; a shift range change mechanism that changes an actual shift range of the automatic transmission apparatus; an electric actuator that includes an electric motor and an output shaft, wherein the output shaft is driven by the electric motor to drive the shift range change mechanism; a shift range setting device, through which a user selects a shift range of the automatic transmission apparatus, wherein the shift range setting device outputs a range demand value that indicates the currently selected shift range; and a shift-by-wire (SBW) controller that controls the electric motor based on the range demand value outputted from the shift range setting device and a rotational angular position of the output shaft to drive the shift range change mechanism and thereby to change the actual shift range to the currently selected shift range, wherein: the SBW controller includes a shift-by-wire (SBW) storage device; the SBW controller stores the rotational angular position of the output shaft into the SBW storage device; and when the SBW controller is restarted due to instantaneous power interruption, the SBW controller maintains and uses the current angular position of the output shaft, which is stored in the SBW storage device, as a latest rotational angular position of the output shaft that is used to drive the shift range change mechanism upon satisfaction of the following conditions: the electric motor has not been driven before the instantaneous power interruption; and the current rotational angular position of the output shaft, which is stored in the SBW storage device, is not destroyed.