Patent ID: 8874316
Filing Date: 2014-10-28
Classification: B62D

Abstract:
1. A vehicle steering system that applies a driving force to a steering mechanism of a vehicle using a motor having a rotor and a stator that faces the rotor, the vehicle steering system comprising: a current driving device that drives the motor based on an axis current value on a rotation coordinate system that rotates in accordance with a control angle used as a rotation angle in control; a control angle computing device that obtains a present value of the control angle by adding an addition angle to an immediately preceding value of the control angle in each predetermined computation cycle without using an input from a rotational angle sensor that detects a rotation angle of the rotor so that the control angle is determined independently from the rotation angle of the rotor; a vehicle speed detecting device that detects a speed of the vehicle; a steering torque detecting device that detects a steering torque applied to an operating member that is operated to steer the vehicle; a command steering torque setting device that sets a command steering torque used as a target value of the steering torque; an addition angle computing device that computes, without detecting a change of the rotation angle of the rotor, the addition angle based on a torque deviation that is a deviation between the detected steering torque detected by the steering torque detecting device and the command steering torque set by the command steering torque setting device; a command current value computing device that obtains a command current value that is a target value of the axis current value based on the torque deviation; a command current value limiting device that limits the command current value, obtained by the command current value computing device, to a value at or below a high limit value; and a high limit value setting device that sets the high limit value based on the vehicle speed detected by the vehicle speed detecting device.