Patent Document ID: 9228528
Application ID: 14359774
Patent Flag: 1

Claim One:
1. A feedback control system that calculates a P term and an I term on the basis of a deviation between a target value and a measured value of an air-fuel ratio, and calculates a correction amount to be applied to at least one of fuel injection amount and an air amount of an internal combustion engine on the basis of a PI term, which is a sum of the P term and the I term, wherein the feedback control system comprises a controller programmed to: restrict a magnitude of the PI term using a first guard; calculate, as a corrected previous value of the I term, a value obtained by subtracting a difference between a value of the PI term prior to restriction by the first guard and a value of the PI term following restriction by the first guard, from a value of the I term; update the value of the I term by adding an update amount calculated from the deviation to the corrected previous value; store a learned term; calculate a sum of the PI term following restriction by the first guard and the learned term, as a total correction term used to calculate the correction amount; update a value of the learned term on the basis of the value of the PI term following restriction by the first guard; restrict a magnitude of the total correction term using a second guard; and correct the corrected previous value of the I term by subtracting a difference between a value of the total correction term prior to restriction by the second guard and a value of the total correction term following restriction by the second guard, wherein the controller controls one of a fuel injector and an air flow regulator in accordance with the correction amount.