Jtekt Corporation

Frederic Wilhelm

Robert Fuchs

Tsutomu Tamura

Maxime Moreillon

Philippe Mullhaupt

A vehicle steering device includes a steering wheel, an input shaft, an output shaft coupled to the input shaft via a torsion bar, an electric motor, a torque detector that detects a torsion bar torque applied to the torsion bar, a rotational angle detector that detects a rotational angle of the electric motor, and a microcomputer. The microcomputer is configured to estimate a driver torque applied to the steering wheel using at least (i) the torsion bar torque detected by the torque detector, (ii) the rotational angle of the electric motor detected by the rotational angle detector, and (iii) a physical model that is constructed with a torsion bar viscosity and a torsion bar rigidity, and determine whether the steering wheel is operated in a hands-on state or a hands-off state based on the estimated driver torque.

Vehicle steering device

A vehicle steering device includes a driver torque estimation unit that includes a driver torque estimation observer, a low-pass filter, and a hands-on/off determination unit. The driver torque estimation observer estimates driver torque applied to a steering wheel by a driver on the basis of a detected value that includes at least torsion bar torque detected by a torque sensor and the rotational angle of an electric motor detected by a rotational angle sensor. The low-pass filter performs a low-pass filtering process on the estimated driver torque. The hands-on/off determination unit determines whether in a hands-on state or a hands-off state on the basis of the driver torque after being subjected to the low-pass filtering process.

In an electric power steering system, an ECU includes a rotation angle calculation unit, an assist torque command value calculation unit, a reference model, an angle deviation calculation unit, a PD control unit, an addition unit, and a plant observer. A proportional gain and a derivative gain which are used in the PD control unit and a first gain and a second gain which are used in a first gain multiplication unit and a second gain multiplication unit of the plant observer are set so that a characteristic equation corresponding to an equation of motion representing behavior of the electric power steering system has a double root.

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Obernai, France

Frederic Wilhelm