Controller for automatic transmission

A controller for a stepped automatic transmission that includes a plurality of frictional engagement elements that are each selectively switched between engaged and disengaged states to selectively establish a plurality of shift stages, the controller comprising:

• an electronic control unit configured to:
• (i) perform gear shift control when performing a gear shift operation between different ones of the plurality of shift stages, the gear shift control being based on a target gear shift characteristic value determined based on an input torque of the automatic transmission at a gear shift start time;
• and
• (ii) update the target gear shift characteristic value during the gear shift operation when the input torque increases during the gear shift operation to a first torque value that is greater by a predetermined value than the input torque that existed at the gear shift start time, wherein
• the target gear shift characteristic value is updated to a first updated target gear shift characteristic value that is determined based on the first torque value, and
• the gear shift control is continued based on the first updated target gear shift characteristic value from a first updating time at which the input torque was determined to have become the first torque value.