Patent ID: 9296415
Filing Date: 2016-03-29
CPC Classification: B62D

Claim Text:
1. An electronic power steering apparatus comprising: a steering force assist device having a motor as a drive source, wherein the steering force assist device applies an assist force to a steering system of a vehicle; a torque sensor for outputting sensor signals generated by a plurality of systems based on torsion of a torsion bar provided in a steering shaft; a vehicle speed sensor for detecting a vehicle speed; a torque calculation section for detecting a steering torque based on the sensor signals outputted from the torque sensor; and a control section for controlling the steering force assist device, for calculating an assist control variable based on the steering torque and the vehicle speed, and for executing an assist control for applying an assist force based on the assist control variable to the steering system; wherein upon detection that only one of the sensor signals generated by the plurality of systems is normal, the control section executes an assist restriction process for setting an upper limit value and a lower limit value of the assist control variable based on a map according to at least any one of the lateral acceleration, steering angle, steering speed and yaw rate, the control section has a first map selected when the vehicle speed is lower than or equal to a first speed and a second selected when the vehicle speed is a second speed being higher than the speed, and the control section executes, when the vehicle speed is higher than the first speed but lower than the second speed, the assist restriction process based on an upper limit value and a lower limit value of the assist control variable obtained by interpolation of the first map and the second map.