APPARATUS, SYSTEM, AND VEHICLE CONTROL APPARATUS

An apparatus to be applied to a vehicle including a transmission configured to execute a gear shifting operation for changing a gear ratio by engaging or disengaging friction engagement elements having friction members pushed by a piston that moves through hydraulic pressure supply to an oil chamber, the apparatus including: a memory storing mapping data for defining mapping, the mapping including a pressure variable and a period variable as input variables, the mapping including a stroke amount as an output variable, the pressure variable indicating a waiting pressure, the period variable indicating a waiting period; and a processor configured to: acquire values of the input variables, and calculate a value of the output variable by inputting, to the mapping, the acquired values of the input variables.