Patent ID: 8112204

Claim:
An automatic transmission controller for an automatic transmission, comprising: a sensor input state evaluator configured to determine whether a sensor input signal is normal or abnormal, wherein the sensor input signal carries information about a measured vehicle state variable; a vehicle speed calculator configured to: calculate a predicted vehicle speed with reference to the measured vehicle state variable, in response to determination that the sensor input signal is normal; calculate the predicted vehicle speed with reference to a first alternative value instead of the measured vehicle state variable, in response to determination that the sensor input signal is abnormal; and calculate the predicted vehicle speed with reference to the measured vehicle state variable, in response to determination that the sensor input signal becomes normal after abnormal; a target transmission ratio calculator configured to: calculate a target transmission ratio with reference to the predicted vehicle speed, in response to determination that the sensor input signal is normal; calculate the target transmission ratio with reference to a second alternative value instead of the predicted vehicle speed, in response to determination that the sensor input signal is abnormal; calculate the target transmission ratio with reference to the second alternative value instead of the predicted vehicle speed, in response to determination that a predetermined condition is unsatisfied after the sensor input signal becomes normal after abnormal; and calculate the target transmission ratio with reference to the predicted vehicle speed, in response to determination that the predetermined condition is satisfied after the sensor input signal becomes normal after abnormal; and a transmission ratio controller configured to control the automatic transmission with reference to the target transmission ratio.