Abstract: The present invention provides an electric power steering device enabled to compensate for the influence of the inertia of a steering-assisting-force generating motor on steering with accurate timing even when a steering direction is reversed at high speed. Based on steering torque and a rotation angular speed of a steering-assisting-force generating motor, a steering angular acceleration correspondence value is obtained. The device has means for regulating a gain, which is multiplied to a change acceleration of the steering torque. The motor is controlled so that the steering assisting force is corrected according to a motor output correction value obtained on the basis of the relation between the motor output correction value and the steering angular acceleration correspondence value, which is preliminarily determined and stored in such a way as to compensate for the influence of the inertia on steering, and the obtained steering angular acceleration correspondence value.

Abstract: An individual-cylinder air-fuel ratio estimation model is designed so as to consider the mixing of gases exhausted from adjacent combustion cylinders, and a movement by which a mixed gas arrives at the position of an air-fuel ratio sensor, in order that influences ascribable to the intervals (combustion intervals) of the adjacent combustion cylinders may be reflected on the estimation values of individual-cylinder air-fuel ratios. In evaluating the mixing of the gases which are exhausted from the adjacent combustion cylinders, there are considered the lengths and shapes of the exhaust manifolds of the respective combustion cylinders. In evaluating the movement by which the mixed gas arrives at the position of the air-fuel ratio sensor, there are considered a distance or volume from the confluence to the position of the air-fuel ratio sensor, and the exhaust gas quantities of the respective combustion cylinders.

Abstract: An air-fuel ratio sensor detects an air-fuel ratio of an exhaust gas at a confluent portion of an exhaust gas. An air-fuel ratios in each cylinder are estimated to be controlled based on an output of the air-fuel ratio sensor. A computer determines whether an air-fuel detecting timing deviates according to a dispersion of the estimated air-fuel ratio among cylinders. When the deviation is detected, the air-fuel ratio detecting timing is varied to estimate an air-fuel ratio before and after correcting amount of fuel. The air-fuel ratio detecting timing is adapted as a proper timing when the variation amount of the estimated air-fuel ratio before and after the correction of fuel amount corresponds to the correct amount of fuel.

Abstract: A secondary air supply abnormality detection system determines that an abnormality is generated in a system including a secondary air supply system if a true secondary air flow rate is out of a predetermined range. The true secondary air flow rate is calculated by subtracting a secondary air flow rate average at the time when an air pump is not operating from another secondary air flow rate average at the time when the air pump is operating. Thus, variation in the secondary air flow rate due to change with time or production tolerance can be suitably corrected. Since calculation accuracy of the true secondary air flow rate is improved, determination accuracy of the abnormality in the system including the secondary air supply system can be improved.

Abstract: When a specified air-fuel ratio F/B control condition is established during supply of a secondary air provided, an air-fuel ratio F/B control is executed, and at this time, an initial value of a target air-fuel ratio is set to a before-catalyst air-fuel ratio detected by an A/F (air-fuel ratio) sensor. The target air-fuel ratio subsequent to this is gradually changed from the initial value to a specified air-fuel ratio. By this, the initial value of the target air-fuel ratio can be suitably set at a start time of execution of the air-fuel ratio F/B control during the supply of the secondary air. The target air-fuel ratio subsequent to this is gradually changed to a stoichiometric air-fuel ratio, so that a change in engine rotation speed is suppressed and the drivability can be improved.

Abstract: A secondary air supply abnormality detection system determines that an abnormality is generated in a system including a secondary air supply system if a true secondary air flow rate is out of a predetermined range. The true secondary air flow rate is calculated by subtracting a secondary air flow rate average at the time when an air pump is not operating from another secondary air flow rate average at the time when the air pump is operating. Thus, variation in the secondary air flow rate due to change with time or production tolerance can be suitably corrected. Since calculation accuracy of the true secondary air flow rate is improved, determination accuracy of the abnormality in the system including the secondary air supply system can be improved.

Abstract: The present invention provides an electric power steering device enabled to compensate for the influence of the inertia of a steering-assisting-force generating motor on steering with accurate timing even when a steering direction is reversed at high speed. Based on steering torque and a rotation angular speed of a steering-assisting-force generating motor, a steering angular acceleration correspondence value is obtained. The device has means for regulating a gain, which is multiplied to a change acceleration of the steering torque. The motor is controlled so that the steering assisting force is corrected according to a motor output correction value obtained on the basis of the relation between the motor output correction value and the steering angular acceleration correspondence value, which is preliminarily determined and stored in such a way as to compensate for the influence of the inertia on steering, and the obtained steering angular acceleration correspondence value.

Abstract: An intermediate target value calculating unit calculates an intermediate target value &phgr;midtg(i) on the basis of an output &phgr;(i−1) of an A/F ratio sensor in computation of last time and a final target value &phgr;tg(i). By the computation, the intermediate target value &phgr;midtg(i) is set between the output &phgr;(i−1) of the A/F ratio sensor in computation of last time and the final target value &phgr;tg(i). A correction amount calculating unit calculates a correction amount AFcomp(i) of the target A/F ratio on the basis of a deviation &Dgr;&phgr;(i) between the intermediate target value &phgr;midtg(i) and the output &phgr;(i) of the A/F ratio sensor. Consequently, the control is hard to be influenced by variations in waste time of the subject to be controlled and an error in modeling. While maintaining the stability of the A/F ratio feedback control, higher gain can be achieved and robustness can be also increased.

Abstract: An intermediate target value calculating unit calculates an intermediate target value &phgr;midtg(i) on the basis of an output &phgr;(i=1) of an A/F ratio sensor in computation of last time and a final target value &phgr;tg(i). By the computation, the intermediate target value &phgr;midtg(i) is set between the output &phgr;(i−1) of the A/F ratio sensor in computation of last time and the final target value &phgr;tg(i). A correction amount calculating unit calculates a correction amount AFcomp(i) of the target A/F ratio on the basis of a deviation &Dgr;&phgr;(i) between the intermediate target value &phgr;midtg(i) and the output &phgr;(i) of the A/F ratio sensor. Consequently, the control is hard to be influenced by variations in waste time of the subject to be controlled and an error in modeling. While maintaining the stability of the A/F ratio feedback control, higher gain can be achieved and robustness can be also increased.