Controller for internal combustion engine

A controller for an internal combustion engine comprising:

• at least one processor;
• and
• at least one memory coupled to the at least one processor, the at least one memory including at least one computer-executable program that upon execution causes the at least one processor to execute:
• control amount calculation processing of calculating a control amount relating to combustion of the internal combustion engine for each combustion cycle, based on information from a sensor which detects a state of the internal combustion engine;
• and
• operation amount change processing of changing at least one operation amount among a plurality of operation amounts affecting the control amount for each change cycle, one change cycle consisting of N combustion cycles, where N is greater than or equal to 2;
• wherein, in the operation amount change processing, the at least one processor operates to:
• choose a reference normal population of the control amount under a current operating condition of the internal combustion engine from a plurality of reference normal populations set for each operating condition of the internal combustion engine;
• execute, in each combustion cycle from a first combustion cycle to a Nth combustion cycle that composes the change cycle,
• average calculation processing of calculating a n-cycle average that is an average of the control amounts from the first combustion cycle to a nth combustion cycle, where n is greater than or equal to 1 and n is less than or equal to N,
• error calculation processing of calculating a n-cycle error that is an error of the n-cycle average with respect to an average of the reference normal population, and
• threshold set processing of setting both a positive change determination threshold and a negative change determination threshold with respect to the n-cycle error, based on a standard error of the reference normal population in a case where number of data is n;
• and
• choose an operation amount to be changed from the plurality of operation amounts, based on a comparison between a series of the n-cycle errors from the first combustion cycle to the Nth combustion cycle and a series of the positive change determination thresholds from the first combustion cycle to the Nth combustion cycle and a comparison between the series of the n-cycle errors from the first combustion cycle to the Nth combustion cycle and a series of the negative change determination thresholds from the first combustion cycle to the Nth combustion cycle.