Controller for automatic transmission and method for controlling automatic transmission

A controller for an automatic transmission of a planetary gear type, wherein the automatic transmission includes multiple friction-type engagement elements and an input shaft configured to be connected to an output shaft of an internal combustion engine, each of the engagement elements is configured to be switched between an engaged state and a disengaged state, and a change in combination of ones of the engagement elements that are in the engaged state changes a gear stage of the automatic transmission, the controller comprising:

• processing circuitry that is configured to
• when starting a skip downshift that shifts the gear stage from a pre-shifting gear stage to a post-shifting gear stage, which is two or more stages lower than the pre-shifting gear stage, through a single shifting operation, execute disengaging two or more of the engagement elements that are in the engaged state, wherein the disengaging two or more of the engagement elements includes a first process that sets a first engagement element to an engagement preparation state that maintains a state immediately before the engaged state, the first engagement element is one of the two or more of the engagement elements that are disengaged and is used to form an intermediate gear stage, and the intermediate gear stage has a lower transmission ratio than the post-shifting gear stage,
• after executing the first process, execute a second process that engages a second engagement element, which is one of the engagement elements used to form both the intermediate gear stage and the post-shifting gear stage, and temporarily increases engagement pressure of the first engagement element, and
• after executing the second process, execute a third process that disengages the first engagement element and engages a third engagement element, which is one of the engagement elements used to form the post-shifting gear stage, to form the post-shifting gear stage.