A rear wheel steering motor generates rotational force. A movement converter has a converting portion coupled to the wheel steering motor and configured to convert the rotational force transmitted from the rear wheel steering motor into a linear movement. An MR fluid is applied on the converting portion. An inverter controls driving of the rear wheel steering motor. A magnet switch works in concert with the inverter to change a magnetic field to selectively provide the magnetic field to the MR fluid of the movement converter.

A power supply voltage terminal and a ground terminal having a rectangular cross section are respectively connected to a first terminal hole of a power supply pattern and a second terminal hole of a ground pattern. An inductor is surface-mounted on a substrate, and has a rectangular parallelepiped shape in which an input end connected to a power supply pattern and an output end connected to a power supply relay face each other. A first electrode terminal of a capacitor is connected to the power supply pattern, a second electrode terminal is connected to the ground pattern, and constitutes a filter circuit together with the inductor. A wall surface of an input end of the inductor is arranged parallel to the longitudinal axis direction (x direction) of the first terminal hole. The inductor opposes the first terminal hole so as to include the entire length Wh of the first terminal hole within the width Wt of the input end in the x direction.

A power supply voltage terminal and a ground terminal having a rectangular cross section are respectively connected to a first terminal hole of a power supply pattern and a second terminal hole of a ground pattern. An inductor is surface-mounted on a substrate, and has a rectangular parallelepiped shape in which an input end connected to a power supply pattern and an output end connected to a power supply relay face each other. A first electrode terminal of a capacitor is connected to the power supply pattern, a second electrode terminal is connected to the ground pattern, and constitutes a filter circuit together with the inductor. A wall surface of an input end of the inductor is arranged parallel to the longitudinal axis direction (x direction) of the first terminal hole. The inductor opposes the first terminal hole so as to include the entire length Wh of the first terminal hole within the width Wt of the input end in the x direction.

A motor includes a rotor, a stator that surrounds the radial outer side of the rotor, a housing that contains the rotor and the stator, a holder axially above the stator, a substrate fixed to the axial upper side of the holder, and a connector radially outward of the housing and electrically connected to the substrate. The holder includes a holder body, and a holder protrusion that connects to the holder body and extends radially outward from the housing. The connector contacts the underside of the holder protrusion.

A motor includes a rotor, a stator that surrounds the radial outer side of the rotor, a housing that contains the rotor and the stator, a holder axially above the stator, a substrate fixed to the axial upper side of the holder, and a connector radially outward of the housing and electrically connected to the substrate. The holder includes a holder body, and a holder protrusion that connects to the holder body and extends radially outward from the housing. The connector contacts the underside of the holder protrusion.

The torque transmission joint includes an intermediate transmission member, and a first transmission member and a second transmission member that are arranged with one each on both side sections in the axial direction of the intermediate transmission member, with the outer side sections in the radial direction of each engaging with the inside section in the radial direction of the intermediate transmission member. The first transmission member and the second transmission member have a first preliminary engagement section and a second preliminary engagement section at the end sections in the axial direction on sides close to each other. The first preliminary engagement section and the second preliminary engagement section engage with each other with a circumferential gap interposed therebetween that does not disappear when torque transmission is performed between the first transmission member and the second transmission member via the intermediate transmission member.

An ECU includes a plurality of motor driving circuits for driving at least one motor, a plurality of computers and a plurality of clock circuits. A first computer, which is at a synchronization signal transmission-side, transmits a synchronization signal to a second computer, which is at a synchronization signal reception-side. The first computer and the second computer execute a plurality of specific periodic processes, which are processes executed at cycle periods (for example, 200 μs, 400 μs) of different natural number multiples of a cycle period (for example, 200 μs) of the synchronization signal and need be synchronized. Each timing of the plurality of specific periodic processes is determined based on one synchronization signal.

A steering system is configured such that a ratio of a turning angle change amount with respect to a steering angle change amount in a first steering angle area is larger than the ratio of the turning angle change amount with respect to the steering angle change amount in a second steering angle area, and a steering angle in the second steering angle is smaller than the steering angle of the first steering angle area. An electronic control unit of the steering system sets a delay degree of a change in turning angle with respect to a change in steering angle in the first steering angle area to be larger than the delay degree of the change in turning angle with respect to the change in steering angle in the second steering angle area regardless of a turning-over operation or a turning-back operation.

Disclosed is zero point compensation method and device for EPS. The method includes: acquiring a value of lateral distance when a vehicle travels along an ideal path and obtaining a smoothed lateral distance value, for each control cycle; calculating a longitudinal movement distance value of the vehicle for each control cycle; performing linear fitting to obtain a linear relationship between the longitudinal movement distance value and the smoothed lateral distance value; calculating a zero point compensation angle for the EPS based on a first parameter in the linear relationship and a preset steering wheel transmission ratio, and compensating a steering control angle; and determining that the zero point compensation angle passes verification when a minimum residual error is less than a preset acceptable deviation. In this way, the time required for calibration can be reduced, and the accuracy and effectiveness of the control algorithm can be improved.

A motor driven power steering control method may include setting a virtual friction model to a column connected between a steering wheel and a rack gear; calculating a frictional torque of the column by taking a steering angular speed of the steering wheel as an input parameter in the set virtual friction model; and calculating a target steering torque on the basis of a virtual steering system model using the frictional torque of the column as a parameter.