Driving force distribution control apparatus for four-wheel drive vehicle and driving force distribution control method for four-wheel drive vehicle

A driving force distribution control apparatus for a four-wheel drive vehicle including a driving force transmission path via which a driving force generated by a drive source is transferred to primary drive wheels and secondary drive wheels, and a driving force distribution apparatus disposed in the driving force transmission path between the drive source and the secondary drive wheels, the driving force distribution control apparatus comprising:

• primary rotational speed theoretical value calculating means for calculating a primary rotational speed theoretical value of the primary drive wheels based on a steering angle, a vehicle speed, a yaw rate, and a slip angle of the four-wheel drive vehicle;
• secondary rotational speed theoretical value calculating means for calculating a secondary rotational speed theoretical value of the secondary drive wheels based on a steering angle, a vehicle speed, a yaw rate, and a slip angle of the four-wheel drive vehicle;
• rotational difference normative theoretical value calculating means for calculating a rotational difference normative theoretical value indicating a difference between rotational speed theoretical values of input and output shafts of the drive force distribution apparatus using the primary rotational speed theoretical value and the secondary rotational speed theoretical value;
• normative value calculating means for calculating a rotational difference normative value by correcting the rotational difference normative theoretical value based on a deviation between a measurement value of a rotational difference between the input and output shafts of the drive force distribution apparatus and the rotational difference normative theoretical value;
• and
• servo controlling means for correcting the driving force provided to the secondary drive wheels using the drive force distribution apparatus through servo control of the rotational difference measurement value, a target value of the servo control being the rotational difference normative value.

A driving force distribution control method for a four-wheel drive vehicle, the method comprising:

• transferring a driving force generated by a drive source to primary drive wheels and secondary drive wheels via a driving force transmission path;
• calculating a primary rotational speed theoretical value of the primary drive wheels based on a steering angle, a vehicle speed, a yaw rate, and a slip angle of the four-wheel drive vehicle;
• calculating a secondary rotational speed theoretical value of the secondary drive wheels based on a steering angle, a vehicle speed, a yaw rate, and a slip angle of the four-wheel drive vehicle;
• calculating a rotational difference normative theoretical value indicating a difference between rotational speed theoretical values of input and output shafts of the drive force distribution apparatus using the primary rotational speed theoretical value and the secondary rotational speed theoretical value;
• calculating a rotational difference normative value by correcting the rotational difference normative theoretical value based on a deviation between a measurement value of a rotational difference between the input and output shafts of the drive force distribution apparatus and the rotational difference normative theoretical value;
• and
• correcting the driving force provided to the secondary drive wheels using the drive force distribution apparatus through servo control of the rotational difference measurement value, a target value of the servo control being the rotational difference normative value.