DEVICE AND METHOD FOR CONTROLLING A STEER-BY-WIRE SYSTEM

Abstract

Device for controlling a steer-by-wire system with: a reaction torque generator (170) configured to generate a reaction torque as a calculated value of a steering reaction torque applied to a steering wheel; a driver torque estimator (150) trained to detect a driver torque estimator as an estimator of a driver steering torque; a speed controller (140) configured to generate a motor torque command value of a motor-driven power steering system; a torque adjuster (160) configured to calibrate the engine torque command value and the reaction torque based on the driver torque estimate and output as a final active return torque and a final reaction torque; and a target current generator (210) which is configured to generate a target current for motor control using the final active return torque and the final reaction torque supplied by the torque adjuster (160), and to supply the generated target current to a motor which provides a steering wheel reaction force to a driver.

Description

BACKGROUND AREA

[0001] Embodiments of the present disclosure relate to an apparatus and method for controlling a steer-by-wire system, and more particularly, to an apparatus and method for controlling a steer-by-wire system that can generate a target current to control a reaction force of a steering wheel based on a rack force, a vehicle speed, a steering angular velocity, and a steering angle in a steer-by-wire system. DISCUSSION OF THE BACKGROUND

[0002] A steer-by-wire system is a steering system capable of eliminating mechanical connections between a steering wheel and a vehicle's wheels. The steer-by-wire system receives a steering wheel rotation signal through an ECU (Electronic Control Unit) and steers the vehicle by actuating steering motors connected to the wheels based on the received rotation signal.

[0003] Since the steer-by-wire system eliminates a mechanical connection structure of an existing steering system, the steer-by-wire system can increase the degree of design freedom according to the structure of a steering system, improve fuel efficiency, and eliminate disturbances reversely fed from the wheels.

[0004] The related art of the present disclosure is disclosed in Korean Patent Application No. 10-2019-0066995 (KR 10 2019 0 066 995 A), published on June 14, 2019, entitled "Method for Generating Steering Reaction Force of Steer-By-Wire System." This document describes a steer-by-wire steering system in which a reaction torque generator applies a reaction torque to the steering wheel depending on the vehicle speed, the steering wheel angle, and the steering wheel angular velocity.DE 10 2017 222 952 A1 discloses a device for controlling a steer-by-wire system, comprising: a reaction torque generator configured to generate a reaction torque as a calculated value of a steering reaction torque applied to a steering wheel; a driver torque estimator configured to detect a driver torque estimate as an estimated value of a driver steering torque; a speed controller configured to generate a motor torque command value of a motor-driven servo system; and a target current generator configured to generate a target current for motor control using the motor torque command value and as a function of an estimated driver steering torque input by the torque adjuster, and to feed the generated target current to a motor. Another steer-by-wire system is known from DE 10 2017 223 288 A1.The object of the present invention is to further develop the prior art steer-by-wire systems in such a way that the driver's steering feel is improved and manufacturing costs are reduced. Furthermore, the object of the present invention is to provide a corresponding method for controlling a steer-by-wire system. OVERVIEW

[0005] The above object is achieved by devices and a method for controlling a steer-by-wire system having the features of independent claims 1, 11, and 20. Advantageous further developments emerge from the subclaims. Various embodiments relate to a device and a method for controlling a steer-by-wire system, which can generate a target current to control a reaction force of a steering wheel based on a rack force, a vehicle speed, a steering angle speed, and a steering angle in a steer-by-wire system.

[0006] In one embodiment, an apparatus for controlling a steer-by-wire system may include: a reaction torque generator configured to generate a reaction torque as a calculated value of a steering reaction torque applied to a steering wheel; a driver torque estimator configured to detect a driver torque estimate as an estimate of a driver steering torque; a speed controller configured to generate a motor torque command value of a motor-driven power steering system; a torque adjuster configured to calibrate the motor torque command value and the reaction torque based on the driver torque estimate and output them as a final active return torque and a final reaction torque;and a target current generator configured to generate a target current for motor control using the final active return torque and the final reaction torque input from the torque adjuster, and to feed the generated target current to a motor that provides a reaction force of the steering wheel to a driver.;

[0007] The reaction torque generator may generate the reaction torque by adding a hysteresis torque based on a steering angular velocity of a steering wheel to a reaction torque based on a rack force.

[0008] The reaction torque generator may include: a reaction torque decision unit configured to determine the reaction torque based on the rack force, based on a vehicle speed, and a rack force estimate of a steering system; a hysteresis torque decision unit configured to determine the hysteresis torque based on the steering angular velocity of the steering wheel; and a weight application unit configured to calculate the reaction torque by applying a weight to the reaction torque based on the rack force and the hysteresis torque.

[0009] The hysteresis torque decision unit may determine the hysteresis torque by a model that determines a hysteresis torque value based on the steering angular velocity.

[0010] The hysteresis torque decision unit can determine the model taking into account the vehicle speed.

[0011] The weight application unit may determine a weight between the reaction torque based on the rack force and the hysteresis torque according to the steering angular velocity.

[0012] The device may further comprise a final lock torque detector configured to detect a final lock torque when the steering angle reaches an end stop of a steering wheel or a difference between the steering angle and a pinion angle is equal to or greater than a predetermined angle, wherein the target current generator generates the target current for the motor control by further using the final lock torque.

[0013] The end-lock torque detector can detect the end-lock torque based on the steering angle or the rack force estimate.

[0014] The end-lock torque detector may include: a limit stop processing unit configured to detect a torque based on the steering angle from an end-stop torque map when the steering angle reaches the end stop of the steering wheel; a curb processing unit configured to detect a torque based on the rack estimate from a curb torque map when the difference between the steering angle and the pinion angle is equal to or greater than the predetermined angle; and a end-lock torque setting unit configured to set the torque detected by the limit stop processing unit or the curb processing unit as the end-lock torque.

[0015] The apparatus may further comprise a damping torque detector configured to detect a damping torque using one or more of the vehicle speed, the steering angle, and the steering angular velocity, wherein the target current generator generates the target current for the motor control by further using the damping torque.

[0016] In one embodiment, an apparatus for controlling a steer-by-wire system may include: a reaction torque generator configured to generate a reaction torque as a calculated value of a steering reaction torque applied to a steering wheel; a rack force estimator configured to estimate a rack force applied to a rack of a motor-driven power steering system; a speed controller configured to generate a motor torque command value of the motor-driven power steering system; a torque adjuster configured to calibrate the torque command value and the reaction torque based on the rack force estimate and output them as a final active return torque and a final reaction torque;and a target current generator configured to generate a target current for motor control using the final active return torque and the final reaction torque input from the torque adjuster, and to feed the generated target current into a motor that provides a reaction force of the steering wheel to a driver;

[0017] The reaction torque generator may generate the reaction torque by adding the hysteresis torque based on a steering angular velocity of a steering wheel to a reaction torque based on a rack force.

[0018] The reaction torque generator may include: a reaction torque decision unit configured to determine the reaction torque based on the rack force, based on a vehicle speed, and a rack force estimate of a steering system; a hysteresis torque decision unit configured to determine the hysteresis torque based on the steering angular velocity of the steering wheel; and a weight application unit configured to calculate the reaction torque by applying a weight to the reaction torque based on the rack force and the hysteresis torque.

[0019] The hysteresis torque decision unit may determine the hysteresis torque by a model that determines a hysteresis torque value based on the steering angular velocity.

[0020] The weight application unit may determine a weight between the reaction torque based on the rack force and the hysteresis torque according to the steering angular velocity.

[0021] The device may further comprise a final lock torque detector configured to detect a final lock torque when the steering angle reaches an end stop of a steering wheel or a difference between the steering wheel and a pinion angle is equal to or greater than a predetermined angle, wherein the target current generator generates the target current for the motor control by further using the final lock torque.

[0022] The end-lock torque detector can detect the end-lock torque based on the steering angle or the rack force estimate.

[0023] The end-lock torque detector may include: a limit stop processing unit configured to detect a torque based on the steering angle from an end-stop torque map when the steering angle reaches the end stop of the steering wheel; a curb processing unit configured to detect a torque based on the rack estimate from a curb torque map when the difference between the steering angle and the pinion angle is equal to or greater than the predetermined angle; and a end-lock torque setting unit configured to set the torque detected by the limit stop processing unit or the curb processing unit as the end-lock torque.

[0024] The apparatus may further comprise a damping torque detector configured to detect a damping torque using one or more of the vehicle speed, the steering angle, and the steering angular velocity, wherein the target current generator generates the target current for the motor control by further using the damping torque.

[0025] In one embodiment, a method for controlling a steer-by-wire system may include: generating a reaction torque as a calculated value of a steering reaction torque applied to a steering wheel; detecting a driver torque estimate as an estimate of a driver steering torque or an estimate of a rack force applied to a rack of a motor-driven power steering system; generating a motor torque command value of the motor-driven power steering system; calibrating the motor torque command value and the reaction torque based on the driver torque estimate or the rack force estimate and outputting them as a final active return torque and a final reaction torque;and generating a target current for the motor control using the final active return torque and the final reaction torque and feeding the generated target current to a motor that provides a reaction force of the steering wheel to a driver;

[0026] Generating the reaction torque may include generating the reaction torque by adding a hysteresis torque based on a steering angular velocity of a steering wheel to a reaction torque based on a rack force.

[0027] Generating the reaction torque may include: determining the reaction torque based on the rack force based on a vehicle speed and a rack force estimate of a steering system; determining the hysteresis torque based on the steering angular velocity of the steering wheel; and calculating the reaction torque by applying a weight to the reaction torque based on the rack force and the hysteresis torque.

[0028] Determining the hysteresis torque may include determining the hysteresis torque by a model that determines a hysteresis torque value based on the steering angular velocity.

[0029] Determining the hysteresis torque may include determining the model taking into account the vehicle speed.

[0030] Calculating the reaction torque may include determining a weight between the reaction torque based on the rack force and the hysteresis torque corresponding to the steering angular velocity.

[0031] The method may further include detecting an end-lock torque when the steering angle reaches an end stop of a steering wheel or a difference between the steering angle and a pinion angle is equal to or greater than a predetermined angle. Generating the target current for the motor controller may further include generating the target current for the motor controller using the end-lock torque.

[0032] Detecting the end-lock torque may include detecting the end-lock torque based on the steering angle or the rack force estimate.

[0033] Detecting the end-lock torque may include: detecting a torque based on the steering angle from an end-stop torque map when the steering angle reaches the end-stop of the steering wheel; detecting a torque based on the rack force estimate from a curb torque map when the difference between the steering angle and the pinion angle is equal to or greater than a predetermined angle; and setting the torque based on the steering angle or the torque based on the rack force estimate as the end-lock torque.

[0034] The method may further comprise detecting the damping torque using one or more of the vehicle speed, the steering angle, and the steering angular velocity. Generating the target current for the motor controller may further comprise generating the target current for the motor controller using the damping torque.

[0035] In one embodiment, a method for controlling a steer-by-wire system may include: generating a reaction torque as a calculated value of a steering reaction torque applied to a steering wheel; estimating a rack force applied to a rack of a motor-driven power steering system; generating a motor torque command value of the motor-driven power steering system; calibrating the motor torque command value and outputting the final active reversing torque and the final reaction torque; and generating a target current for motor control using the final active reversing torque and the final reaction torque and feeding the generated target current to a motor.

[0036] Generating the reaction torque may include generating the reaction torque by adding the hysteresis torque based on a steering angular velocity of a steering wheel to a reaction torque based on a rack force.

[0037] Generating the reaction torque may include: determining the reaction torque based on the rack force based on a vehicle speed and a rack force estimate of a steering system; determining the hysteresis torque based on the steering angular velocity of the steering wheel; and calculating the reaction torque by applying a weight to the reaction torque based on the rack force and the hysteresis torque.

[0038] Determining the hysteresis torque may include determining the hysteresis torque by a model that determines a hysteresis torque value based on the steering angular velocity.

[0039] Determining the hysteresis torque may include determining the model taking into account the vehicle speed.

[0040] Calculating the reaction torque may include determining a weight between the reaction torque based on the rack force and the hysteresis torque corresponding to the steering angular velocity.

[0041] The method may further include detecting an end-lock torque when the steering angle reaches an end stop of a steering wheel or a difference between the steering angle and a pinion angle is equal to or greater than a predetermined angle. Generating the target current for the motor controller may further include generating the target current for the motor controller using the end-lock torque.

[0042] Detecting the end-lock torque may include detecting the end-lock torque based on the steering angle or the rack force estimate.

[0043] Detecting the end-lock torque may include: detecting a torque based on the steering angle from an end-stop torque map when the steering angle reaches the end-stop of the steering wheel; detecting a torque based on the rack force estimate from a curb torque map when the difference between the steering angle and the pinion angle is equal to or greater than the predetermined angle; and setting the torque based on the steering angle or the torque based on the rack force estimate as the end-lock torque.

[0044] The method may further comprise detecting a damping torque using one or more of the vehicle speed, the steering angle, and the steering angular velocity. Generating the target current for the motor controller may further comprise generating the target current for the motor controller using the damping torque.

[0045] According to embodiments of the present disclosure, the apparatus and method for controlling a steer-by-wire system can estimate the driver torque or rack force and control the active return of the steering wheel using the estimated driver torque or rack force, thereby improving a driver's steering feel.

[0046] The apparatus and method can further perform active return control even without a torque sensor or a torsion bar, thereby reducing the manufacturing cost of the steer-by-wire system.

[0047] The apparatus and method may further calculate the reaction torque by adding the hysteresis torque based on the steering angular velocity of the steering wheel to the reaction torque based on the rack force, thereby improving a driver's steering feel.

[0048] The apparatus and method may further provide an end-stop response feel when the steering angle reaches an end-stop of the steering wheel, thereby preventing a driver from operating the steering wheel beyond the end-stop of the steering wheel in the steer-by-wire steering system.

[0049] The device and method can further provide a reaction feel when the vehicle hits a curb. Thus, a reaction force device and a front-wheel steering system can be mechanically separated, which can improve a driver's steering feel. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a configuration block diagram showing an apparatus for controlling a steer-by-wire system according to an embodiment of the present disclosure. Fig. 2 is a configuration block diagram showing a driver torque estimator according to the embodiment of the present disclosure. Fig. 3 is a configuration block diagram showing a torque adjuster according to the embodiment of the present disclosure. Fig. 4 is a configuration block diagram showing an apparatus for controlling a steer-by-wire system according to another embodiment of the present disclosure. Fig. 5 is a configuration block diagram showing the steer-by-wire system control apparatus according to the other embodiment of the present disclosure. Fig. 6 is a configuration block diagram showing a reaction torque generator according to the embodiment of the present disclosure. Fig. 7 is a diagram showing a specific configuration of the reaction torque generator according to the embodiment of the present disclosure. Fig. 8 is a diagram for describing a road sensitivity attenuation filter of the reaction torque generator according to the embodiment of the present disclosure. Fig. 9 is a diagram for describing a hysteresis map of the reaction torque generator according to the embodiment of the present disclosure. Fig. 10 is a diagram for describing a weight table of the reaction torque generator according to the embodiment of the present disclosure. Fig. 11 is a configuration block diagram showing an end-lock torque detector according to the embodiment of the present disclosure. Fig. 12 is a configuration block diagram showing a target power generator according to the embodiment of the present disclosure. Fig. 13 is a configuration block diagram showing in more detail a feedback controller and a DOB (Disturbance Observer) of the target power generator according to the embodiment of the present disclosure. Fig. 14 shows a flowchart for describing a method for controlling a steer-by-wire system according to an embodiment of the present disclosure. Fig. 15 shows another flowchart for describing the method of controlling a steer-by-wire system according to the embodiment of the present disclosure. Fig. 16 shows a flowchart for describing a method for controlling a steer-by-wire system according to another embodiment of the present disclosure. Fig. 17 shows another flowchart for describing the method of controlling a steer-by-wire system according to the other embodiment of the present disclosure. DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0050] In the following, an apparatus and method for controlling a steer-by-wire system are described with reference to the accompanying drawings using various exemplary embodiments. It should be noted that the drawings are not exactly to scale and may be exaggerated in line thickness or component sizes for the sake of clarity and descriptiveness. Furthermore, the terms used herein are defined with respect to functions of the invention and may be changed depending on the use or intent of users or operators. The terms should therefore be defined in accordance with the present overall disclosures.

[0051] The embodiments described in this specification may, for example, be implemented with a method or process, an apparatus, a software program, a data stream, or a signal. Although a feature is discussed only in a single context (e.g., only in a method), the discussed feature may be implemented in another way (e.g., as an apparatus or program). An apparatus may be implemented in suitable hardware, software, or firmware. The method may be implemented in an apparatus, such as a processor, which generally refers to a processing device, including, for example, a computer, a microprocessor, an integrated circuit, or a programmable logic device.

[0052] Fig. 1 is a configuration block diagram showing an apparatus for controlling a steer-by-wire system according to an embodiment of the present disclosure, Fig. 2 is a configuration block diagram showing a driver torque estimator according to the embodiment of the present disclosure, and Fig. 3 is a configuration block diagram showing a torque adjuster according to the embodiment of the present disclosure.

[0053] Referring to Fig. 1, the control device of a steer-by-wire system according to the embodiment of the present disclosure includes: a vehicle speed detector 110, a steering angle detector 120, a steering angular velocity detector 130, a speed controller 140, a driver torque estimator 150, a torque adjuster 160, a reaction torque generator 170, an end-lock torque detector 180, a damping torque generator 200, and a target current generator 210.

[0054] The vehicle speed detector 110 detects a vehicle speed. A navigation system or a sensor for sensing the wheel speed of a vehicle can be used as the vehicle speed detector 110. Furthermore, the vehicle speed detector 110 can receive the vehicle speed via CAN communication in the vehicle.

[0055] The steering angle detector 120 detects a steering angle of a steering wheel.

[0056] The steering angle speed detector 130 detects a steering angle speed of the steering wheel. The steering angle speed detector 130 may be a sensor for sensing the steering angle speed of the steering wheel. However, the steering angle speed detector 130 may detect a steering angle speed by differentiating the steering angle detected by the steering angle detector 120 without a separate sensor.

[0057] The speed controller 140 generates a motor torque command value of a motor-driven power steering system using the vehicle speed detected by the vehicle speed detector 110 and the steering angle detected by the steering angle detector 120.

[0058] That is, in order to generate the steering angular velocity command value using the vehicle speed detected by the vehicle speed detector 110 and the steering angle detected by the steering angle detector 120, the cruise controller 140 may have an active return tuning table stored therein in advance and configured to store a steering angular velocity command value tuned to the vehicle speed and the steering angle, and to detect a steering angular velocity command value mapped to a current steering angle and a current vehicle speed from the active return tuning table.

[0059] The speed controller 140 receives the steering angular velocity from the steering angular velocity detector 130. As described above, the speed controller 140 generates a motor torque command value based on a difference between the detected steering angular velocity command value and the steering angular velocity detected by the steering angular velocity detector 130 and feeds the generated motor torque command value to the torque adjuster 160.

[0060] The driver torque estimator 150 detects a driver torque estimate using the steering angle, the steering angular velocity, and the engine torque.

[0061] Referring to Fig. 2, the driver torque estimator 150 includes a steering angular velocity estimated value detection unit 152, a steering angular velocity difference detection unit 153, and a driver torque estimated value detection unit 151.

[0062] The steering angular velocity estimation detection unit 152 detects a steering angular velocity estimation using the engine torque and the driver torque estimation. In this case, the steering angular velocity estimation detection unit 152 may detect a steering angular velocity estimation by applying the driver torque estimation and the engine torque to a Kalman filter.

[0063] The steering angular velocity estimation detection unit 152 may receive the driver torque estimation from the driver torque estimation detection unit 151 and may receive the engine torque from another sensor, controller, or device of the steer-by-wire system.

[0064] The steering angular speed difference detection unit 153 detects a difference between the steering angular speed detected by the steering angular speed detector 130 and the steering angular speed estimated value detected by the steering angular speed estimated value detection unit 152, and inputs the detected difference to the driver torque estimated value detection unit 151. That is, the steering angular speed difference detection unit 153 detects a difference between an actual steering angular speed (the steering angular speed detected by the steering angular speed detector 130) and the steering angular speed estimated value (the steering angular speed estimated value detected by the steering angular speed estimated value detection unit 152), and inputs the detected steering angular speed difference to the driver torque estimated value detection unit 151.

[0065] The driver torque estimated value detection unit 151 detects the driver torque estimated value using the steering angle detected by the steering angle detector 120 and the steering angular velocity difference received from the steering angular velocity difference detection unit 153.

[0066] That is, the driver torque estimated value detection unit 151 receives the steering angle and the steering angular velocity difference, detects the driver torque estimated value, and outputs the detected driver torque estimated value.

[0067] The steering angular velocity estimation detection unit 152 receives the driver torque estimation output from the driver torque estimation detection unit 151 and receives the engine torque from another sensor, controller, or device of the steer-by-wire system. The steering angular velocity estimation detection unit 152 then generates the steering angular velocity estimation by applying the driver torque estimation and the engine torque to the Kalman filter and inputs the generated steering angular velocity estimation to the steering angular velocity difference detection unit 153.

[0068] The steering angular velocity difference detection unit 153 detects a difference between the steering angular velocity detected by the steering angular velocity detector 130 and the steering angular velocity estimated value detected by the steering angular velocity estimated value detection unit 152, and inputs the detected steering angular velocity difference to the driver torque estimated value detection unit 151.

[0069] Such a process is repeated continuously.

[0070] The driver torque estimate output from the driver torque estimate detection unit 151 is input to the torque adjuster 160.

[0071] The torque adjuster 160 calibrates the motor torque command value input from the speed controller 140 and the reaction torque input from the reaction torque generator 170 based on the driver torque estimate, and outputs the final active reversing torque and the final reaction torque.

[0072] Referring to Fig. 3, the torque adjuster 160 includes a decoupling gain detection unit 161, an active return torque adjusting unit 162, and a reaction torque adjusting unit 163.

[0073] The decoupling gain detection unit 161 detects a decoupling gain using the driver torque estimate input from the driver torque estimate detection unit 151. The decoupling gain detection unit 161 includes an absolute value detection part 1611 and a decoupling gain extraction part 1612.

[0074] The absolute value detection part 1611 detects the absolute value of the driver torque estimate.

[0075] The decoupling gain extraction part 1612 extracts a decoupling gain corresponding to the absolute value of the driver torque estimate detected by the absolute value detection part 1611 from a predetermined lookup table.

[0076] The active backlash torque setting unit 162 generates the final active backlash torque by applying the decoupling gain detected by the decoupling gain detection unit 161 to the motor torque command value input from the speed controller 140, and outputs the generated final active backlash torque.

[0077] That is, the active backlash torque setting unit 162 generates the final active backlash torque by multiplying the decoupling gain by the input motor torque command value and outputs the generated final active backlash torque.

[0078] The reaction torque setting unit 163 sets the final reaction torque by applying the decoupling gain detected by the decoupling gain detection unit 161 to the reaction torque.

[0079] The reaction torque serves to provide a driver with proper steering feel by rotating in a direction opposite to the direction of rotation of the steering wheel. In some embodiments, such reaction torque may be received from a reaction force motor (not shown) that provides a reaction force corresponding to the rotation of the steering wheel in a steer-by-wire system that steers a front wheel using a controller and motor according to input from a sensor without a mechanical connection, such as a universal joint between the steering wheel and a front-wheel steering system. Alternatively, as described below, such reaction torque may be received from the reaction torque generator 170.

[0080] The reaction torque setting unit 163 includes a decoupling gain calibration value generating part 1631 and a reaction torque generating part 1632.

[0081] The decoupling gain calibration value generation part 1631 generates a decoupling gain calibration value by subtracting the decoupling gain detected by the decoupling gain detection unit 161 from a predetermined reference gain. The reference gain is set to 1. Therefore, the decoupling gain calibration value generation part 1631 generates the decoupling gain calibration value by subtracting the decoupling gain from 0 to 1 from the reference gain of 1.

[0082] The reaction torque generation part 1632 generates the final reaction torque by applying the decoupling gain calibration value generated by the decoupling gain calibration value generation part 1631 to the reaction torque received from the reaction torque generator 170. That is, the reaction torque generation part 1632 adjusts the reaction torque by multiplying the decoupling gain calibration value by the reaction torque received from the reaction torque generator 170, and provides a driver with a proper driving feel through the reaction torque.

[0083] This means that the torque adjuster 160 outputs the active return torque to return the steering wheel to center. During this process, the torque adjuster 160 outputs a proper reaction torque, thus providing the proper reaction force to the driver while returning the steering wheel to center.

[0084] In the first embodiment, it was described that the steer-by-wire system control device generates the driver torque estimate and generates the active return torque and the reaction torque based on the driver torque estimate. However, the device may use both a rack force estimate and the driver torque estimate. The rack force estimate will be described with reference to a second embodiment.

[0085] Fig. 4 is a configuration block diagram showing an apparatus for controlling a steer-by-wire system according to another embodiment of the present disclosure, and Fig. 5 is a configuration block diagram showing the steer-by-wire system control apparatus according to the other embodiment of the present disclosure.

[0086] Referring to Fig. 4, the steer-by-wire system control apparatus according to the other embodiment of the present disclosure includes a vehicle speed detector 110, a steering angle detector 120, a steering angular velocity detector 130, a speed controller 140, a rack force estimator 250, a rack force estimation value scaling unit 252, and a torque adjuster 190.

[0087] For reference purposes, in the second embodiment, the same components as in the above-described embodiment are represented by the same reference numerals, and a detailed description thereof will be omitted.

[0088] The rack force estimator 250 estimates a rack force of a rack of a motor-driven power steering system.

[0089] The rack force estimator 250 estimates the rack force by applying a vehicle state value or the like, which is detected as vehicle state information from various sensors, to a predefined rack force estimation model. The method for estimating a rack force is not limited to the embodiment described above, but will be apparent to those skilled in the art. Therefore, detailed descriptions thereof are omitted in the present embodiment.

[0090] The rack force estimate scaling unit 252 scales the rack force estimate estimated by the rack force estimator 250 according to the driver torque and feeds the scaled rack force estimate to the torque adjuster 190. Typically, the rack force has a very similar profile to the driver torque, but a different magnitude than the driver torque. Therefore, the rack force estimate scaling unit 252 scales the rack force to match the profile and magnitude of the driver torque. Thus, the rack force can be scaled in a similar manner to the driver torque.

[0091] The torque adjuster 190 includes a decoupling gain detection unit 191, an active return torque adjusting unit 192, and a reaction torque adjusting unit 193.

[0092] The decoupling gain detection unit 191 detects a decoupling gain using the rack force estimate input from the rack force estimate scaling unit 252. The decoupling gain detection unit 191 includes an absolute value detection part 1911 and a decoupling gain extraction part 1912.

[0093] The absolute value detection part 1911 detects the absolute value of the rack force estimated value.

[0094] The decoupling gain extraction part 1912 extracts a decoupling gain corresponding to the absolute value of the rack force estimated value detected by the absolute value detection part 1911 from a predetermined lookup table.

[0095] The active backlash torque setting unit 192 generates an active backlash torque by applying the decoupling gain detected by the decoupling gain detection unit 191 to the motor torque command value input from the speed controller 140, and outputs the generated active backlash torque as the final active backlash torque.

[0096] That is, the active backlash torque setting unit 192 generates the final active backlash torque by multiplying the decoupling gain by the input motor torque command value and outputs the generated final active backlash torque.

[0097] The reaction torque setting unit 193 sets the final reaction torque by applying the decoupling gain detected by the decoupling gain detection unit 191 to the reaction torque received from the reaction torque generator 170.

[0098] The reaction torque setting unit 193 includes a decoupling gain calibration value generating part 1931 and a reaction torque generating part 1932.

[0099] The decoupling gain calibration value generation part 1931 generates a decoupling gain calibration value by subtracting the decoupling gain detected by the decoupling gain detection unit 191 from a predetermined reference gain. The reference gain is set to 1. Therefore, the decoupling gain calibration value generation part 1931 generates the decoupling gain calibration value by subtracting the decoupling gain from 0 to 1 from the reference gain of 1.

[0100] The reaction torque generation part 1932 generates a final reaction torque by applying the decoupling gain calibration value generated by the decoupling gain calibration value generation part 1931 to the reaction torque received from the reaction torque generator 170. That is, the reaction torque generation part 1932 adjusts the reaction torque by multiplying the decoupling gain calibration value by the reaction torque, and provides a driver with a proper driving feel through the reaction torque.

[0101] This means that the torque adjuster 190 outputs the active return torque to return the steering wheel to center. During this process, the torque adjuster 190 outputs a proper reaction torque, thus providing the proper reaction force to the driver while returning the steering wheel to center.

[0102] Fig. 6 is a configuration block diagram showing a reaction torque generator according to the embodiment of the present disclosure.

[0103] Fig. 6 shows a configuration of a steering wheel reaction force control device according to an embodiment of the present disclosure.

[0104] As in Fig. As shown in Figure 6, the reaction torque generator 170 in the steering wheel reaction force control device may generate a reaction torque using a vehicle speed, a steering angular velocity, and a rack force. The reaction torque may be a value obtained by calculating the steering reaction torque applied to the steering wheel.

[0105] Such a reaction torque can be used as a control parameter to control the current of a motor, which provides a reaction force to a driver. In this case, the reaction torque itself can be used to control the motor, or the reaction torque and a torque factor, such as the damping torque, which is not the reaction torque, can be combined to control the motor.

[0106] The detailed configuration of the reaction torque generator 170 described may include circuits, logic elements, or the like, or may be implemented as logic included in a control unit that includes the circuits, logic elements, and the like, or may include a combination of such configurations.

[0107] Fig. 7 is a diagram showing a specific configuration of the reaction torque generator according to the embodiment of the present disclosure.

[0108] As in Fig. 7, the reaction torque generator 170 may include a road sensitivity attenuation filter 171, a reaction torque map 172, a hysteresis map 173, and a weight table 174.

[0109] The road sensitivity attenuation filter 171 may be referred to as a filter unit, the reaction torque map 172 may be referred to as a reaction torque decision unit, the hysteresis map 173 may be referred to as a hysteresis torque decision unit, and the weight table 174 may be referred to as a weight application unit.

[0110] The road sensitivity attenuation filter 171 may filter the rack force estimate output from the rack force estimator 250 and output the filtered rack force estimate to the reaction torque map 172. The road sensitivity attenuation filter 171 may receive the vehicle speed output from the vehicle speed detector 110 and filter the received vehicle speed.

[0111] Fig. 8 is a diagram for describing a road sensitivity attenuation filter of the reaction torque generator according to the embodiment of the present disclosure.

[0112] Referring to Fig. 8, the road sensitivity attenuation filter 171 is described in more detail below.

[0113] As in Fig. 8, the road sensitivity attenuation filter 171 may include notch filters 1711 and 1713 and low-pass filters 1712 and 1714.

[0114] The notch filters 1711 and 1714 can adjust the rack force vibration depending on a mechanism or a specific vibration frequency, and the low-pass filters 1712 and 1714 can adjust the sensitivity of the rack force.

[0115] Such a filtering process can adjust the sensitivity of the road surface response in the rack force estimate output by the rack force estimator 250.

[0116] Notch filters 1711 and 1713 have control parameters such as a cutoff frequency fc, an amplitude, and a depth. The amplitude specifies the width of a filtered frequency, and the depth specifies a decrease in filter gain.

[0117] The cutoff frequency fc, amplitude, and depth can all be determined according to the vehicle speed, and the values ​​of the cutoff frequency fc, amplitude, and depth corresponding to each vehicle speed can be stored in the form of predetermined equations or tables.

[0118] The cutoff frequency may be used as a control parameter of the low-pass filters 1712 and 1714. The cutoff frequencies of the low-pass filters 1712 and 1714 may also be determined according to the vehicle speed, and the value of the cutoff frequency corresponding to each vehicle speed may be stored in the form of a predetermined equation or table.

[0119] As in Fig. As shown in Figure 8, the road sensitivity attenuation filter 171 can be operated in three different modes. The modes can be divided into a mode for filtering a rack force estimate (input value) using only the notch filter 1711 (Mode 1), a mode for filtering the rack force estimate using only the low-pass filter 1712 (Mode 2), and a mode for filtering the rack force estimate using the notch filter 1713 and the low-pass filter 1714 (Mode 3). Such modes can be selected by a user. Depending on the selected mode, the rack force vibration adjustment depending on a mechanism or the specific vibration frequency and the sensitivity adjustment can be selectively applied.

[0120] The reaction torque map 172 may receive the filtered rack force estimate and output the reaction torque corresponding to the rack force.

[0121] Such a reaction torque is determined according to both the vehicle speed and the rack force. For example, a reaction torque value corresponding to each vehicle speed and rack force may be stored in the form of a predetermined equation or table. The reaction torque map 172 may read a value from the table according to the input rack force estimate and the vehicle speed, or determine the reaction torque according to the rack force using an equation.

[0122] The hysteresis card 173 can determine the hysteresis torque according to the steering angular velocity and output the determined hysteresis torque.

[0123] In the case of the reaction torque corresponding to the rack force described above, the rack force estimate received through CAN communication or the like is used as a control input. Thus, a time delay occurs in the rack force received corresponding to a steering angle input. When such a time delay occurs, vibration may be generated. In the present embodiment, the hysteresis torque can be applied in advance to prevent the delay.

[0124] Fig. 9 is a diagram for describing a hysteresis map of the reaction torque generator according to the embodiment of the present disclosure.

[0125] Referring to Fig. 9 the hysteresis map 173 is described in more detail below.

[0126] The hysteresis map 173 is configured to determine the hysteresis torque according to the steering angular velocity, and the hysteresis torque is determined by a hysteresis model 1731.

[0127] The hysteresis model 1731 for determining the hysteresis torque corresponding to a steering angular velocity may have a plurality of graphs, and one of the graphs may be used to calculate the hysteresis torque value.

[0128] The graphs used in the hysteresis model 1731 can be determined according to the slopes of the graphs and the maximum hysteresis value, which are used as parameters. As in Fig. As shown in Figure 9, the inclinations and the maximum hysteresis value can be determined according to the vehicle speed.

[0129] That is, the slope and maximum value of the hysteresis model 1731 corresponding to each vehicle speed may be stored in the form of a predetermined equation or table.

[0130] When such a hysteresis torque is applied, the vehicle can be precisely steered according to the vehicle speed in a central portion of the vehicle, and the drop in starting torque can vary according to the vehicle speed.

[0131] Finally, the reaction torque can be calculated by the weight table 174, which determines the weights of the determined reaction torque and hysteresis torque.

[0132] A steering angle velocity can be used as a control parameter of the weight table 174. According to the steering angle velocity, a weight between the reaction torque and the hysteresis torque can be determined.

[0133] Fig. 10 is a diagram for describing the weight table of the reaction torque generator according to the embodiment of the present disclosure.

[0134] Referring to Fig. 10, a weight corresponding to a steering angular velocity can be stored in the form of a predetermined equation or table. Thus, the weight is determined based on the steering angular velocity. The determined weight is multiplied by a reaction torque based on a rack force, and (1-weight) is multiplied by the hysteresis torque. The two values ​​thus calculated are added to calculate the reaction torque.

[0135] The calculated reaction torque can be used as a control parameter used in the device for controlling a steer-by-wire system as described above.

[0136] In the steer-by-wire system, a reaction force device and a front-wheel steering device are separated from each other, so that a steering shaft and a pinion shaft are not mechanically connected. Since a driver can turn a steering wheel infinitely, the steering wheel's rotation must be stopped at any angle.

[0137] When the steering angle reaches an end stop of the steering wheel, the end lock torque detector 180 sets the end lock torque based on the steering angle and controls a motor to follow the end lock torque.

[0138] This means that the final locking torque detector 180 provides the motor with the final locking torque according to the steering angle at the end stop of the steering wheel (e.g. -360° and 360° when the steering wheel is turned from -360 0 rotated to 360°) and thus interrupts the rotation of the steering wheel so that the driver can see the end stop of the steering wheel.

[0139] Thus, the end-lock torque detector 180 can prevent the driver from operating the steering wheel beyond the end stop of the steering wheel, thereby preventing noise and vibration caused by a collision between a rack and another mechanism at an end stop of the rack stroke, and also improving the durability of the vehicle.

[0140] Furthermore, in the steer-by-wire steering system, the reaction force device and the front-wheel steering device are separated from each other, so the steering shaft and pinion shaft are not mechanically connected. Thus, if the vehicle hits a curb, the steering rack does not move, even though the rack is not positioned at its end stop. Therefore, the steering wheel rotation must be stopped.

[0141] Thus, when the vehicle hits the curb, the final lock torque detector 180 determines the final lock torque based on a rack force estimate and controls the motor to follow the final lock torque.

[0142] That is, when a difference between the steering angle and a pinion angle is equal to or greater than a predetermined angle, the final lock torque detector 180 determines that the vehicle has hit the curb, sets the final lock torque based on the rack force estimation value, and controls the motor to follow the final lock torque.

[0143] As described above, when the steering angle reaches the end stop of the steering wheel or the difference between the steering angle and the pinion angle is equal to or greater than a predetermined angle, the final lock torque detector 180 can set the final lock torque according to the steering angle or the rack force estimation value and control the motor to follow the final lock torque.

[0144] Fig. 11 is a configuration block diagram showing an end-lock torque detector according to the embodiment of the present disclosure.

[0145] The end-lock torque detector 180 includes an end-stop processing unit 181, a curb processing unit 182, and an end-lock torque setting unit 187.

[0146] The end stop processing unit 181 receives the steering angle of the steering wheel and detects a torque corresponding to the steering angle from an end stop torque map when the steering angle reaches the end stop.

[0147] Here, the end stop torque map may be a table in which a torque is set in advance corresponding to each steering angle, as shown in Table 1 below. [Table 1] Lenkwinkel [Grad] 0 5 ... T.B.D[Grad] Drehmoment [Nm] 0 ... ... T.B.D[Nm]

[0148] The curb processing unit 182 receives the steering angle, the pinion angle, and the estimated rack force, and detects the torque corresponding to the estimated rack force from a curb torque map when the difference between the steering angle and the pinion angle is equal to or greater than the predetermined angle. The curb processing unit 182 may receive the pinion angle and the estimated rack force through a communication line (e.g., direct CAN) of the steer-by-wire steering system.

[0149] The curb processing unit 182 may include a calculation part 183 and a curb torque detection part 185.

[0150] The calculation part 183 calculates a difference between the steering angle and the pinion angle and determines whether the calculated difference is equal to or greater than the predetermined angle.

[0151] When the difference between the steering angle and the pinion angle is equal to or greater than the predetermined angle, the curb torque detecting part 184 may determine that the vehicle has hit the curb and detect the torque according to the rack force estimate from the curb torque map.

[0152] Here, the curb torque map may be a table in which a torque is set in advance corresponding to each rack force estimation value, as shown in Table 2 below. [Table 2] Zahnstangenkraft [N] T.B.D ... T.B.D[Grad] Drehmoment [Nm] 0 ... T.B.D[Nm]

[0153] The end-lock torque setting unit 187 sets the torque detected by the end-stop processing unit 181 or the curb processing unit 182 as the end-lock torque.

[0154] The damping torque detector 200 detects the damping torque using the vehicle speed detected by the vehicle speed detector 110, the steering angle detected by the steering angle detector 120, and the steering angular velocity detected by the steering angular velocity detector 130. It will be apparent to those skilled in the art that the damping torque detector 200 detects the damping torque using the vehicle speed, the steering angle, and the steering angular velocity. Therefore, detailed descriptions thereof will be omitted here. The method for detecting the damping torque is not specifically limited.

[0155] Fig. 12 is a configuration block diagram showing a target power generator according to the embodiment of the present disclosure, and Fig. 13 is a configuration block diagram showing in more detail a feedback controller and a DOB (Disturbance Observer) of the target power generator according to the embodiment of the present disclosure.

[0156] The target current generator 210 may generate a target current for motor control using the final active backlash torque and the final reaction torque input from the torque adjuster 160, the final stall torque input from the final stall torque detector 180, and the damping torque input from the damping torque detector 200, and may feed the generated target current to the motor.

[0157] In some embodiments, the target current generator 210 may be configured to generate the target current for motor control using only some of the final active reversing torque, the final reaction torque, the final stall torque, and the damping torque, as described above.

[0158] In another embodiment, the target current generator 210 may be configured to generate the target current for motor control using an additional control factor as well as the control factors described above.

[0159] Referring to Fig. 12 and Fig. 13, the target current generator 210 includes a command reaction torque generator 211, a torque difference calculator 212, a feedback controller 213, a DOB (Disturbance Observer) 214, and an adder 215.

[0160] The command reaction torque generator 211 generates a command reaction torque by combining the final active reversing torque, the final reaction torque, the final stall torque, and the damping torque.

[0161] The torque difference calculator 212 may subtract a column torque from the command reaction torque and output the resulting value as the reaction torque.

[0162] The feedback controller 213 may generate a compensation reaction torque by compensating the torque by a steering mechanism based on the reaction torque output from the torque difference calculator 212, a motor angular velocity, and a steering angular velocity.

[0163] As in Fig. 13, the feedback controller 213 can generate the compensation reaction torque by adding values ​​obtained by reflecting a predefined gain k into the reaction torque output from the torque difference calculator 212, the motor angular velocity, and the steering angular velocity to a value obtained by reflecting the predefined gain K into a value obtained by integrating the reaction torque, thereby obtaining a stable phase range and a high reaction speed.

[0164] The DOB 214 can receive the column torque and the motor input reaction torque and generate a disturbance compensation value by estimating the disturbance.

[0165] The DOB 214 may generate the disturbance compensation value by adding a value obtained by applying a Q filter Q(s) to the received motor input reaction torque to a value obtained by applying an inverse transfer filter G(s) -1 calculated by a steering mechanism and the Q-filter is applied to the received column torque.

[0166] This means that the DOB 214 can compensate for the reaction torque fed into the motor, assuming that mechanical assembly error and mechanism efficiency are disturbances. The Q filter can be adjusted to a certain degree.

[0167] The adder 215 may apply the compensation reaction torque generated by the feedback controller 213 and the disturbance compensation value generated by the DOB 214 and output a motor input reaction torque as the motor torque of a drive motor.

[0168] In the present embodiment, the target current generator 210 can derive a column torque Tc using a worm gear and a torsion bar, which are steering mechanisms.

[0169] Fig. 14 shows a flowchart for describing a method for controlling a steer-by-wire system according to an embodiment of the present disclosure and Fig. 15 shows another flowchart for describing the method of controlling a steer-by-wire system according to the embodiment of the present disclosure.

[0170] As in Fig. 14, the method for controlling a steer-by-wire system according to some embodiments of the present disclosure may include the steps of: step S100 of generating a reaction torque as a calculated value of a steering reaction torque applied to a steering wheel; step S110 of estimating a rack force applied to a rack of a motor-driven power steering system; step S120 of generating a motor torque command value of the motor-driven power steering system; step S130 of calibrating the motor torque command value and the reaction torque based on the rack force estimate and outputting the calibrated values ​​as a final active reversing torque and a final reversing torque, respectively.a final reaction torque; and step S140 for generating a target current for a motor controller using the final active backlash torque and the final reaction torque and for feeding the generated target current to a motor.

[0171] As in Fig. 15, the method for controlling a steer-by-wire system according to some embodiments of the present disclosure may further include steps of: step S240 for detecting a final lock torque when a steering angle reaches an end stop of the steering wheel or a difference between the steering angle and a pinion angle is equal to or greater than a predetermined angle; and step S250 for detecting a damping torque using one or more of the vehicle speed, the steering angle, and a steering angular velocity. In this case, the method may include step S260 for generating the target current for a motor controller further considering the final lock torque and the damping torque in addition to the final active return torque and the final reaction torque.

[0172] Fig. 16 shows a flowchart for describing a method for controlling a steer-by-wire system according to another embodiment of the present disclosure and Fig. 17 shows another flowchart for describing the method of controlling a steer-by-wire system according to the other embodiment of the present disclosure.

[0173] As in Fig. 16, the method for controlling a steer-by-wire system according to some embodiments of the present disclosure may include the steps of: step S300 of generating a reaction torque as a calculated value of a steering reaction torque applied to a steering wheel; step S310 of estimating a rack force applied to a rack of a motor-driven power steering system; step S320 of generating a motor torque command value of the motor-driven power steering system; step S330 of calibrating the motor torque command value and the reaction torque based on the rack force estimate and outputting the calibrated values ​​as a final active reversing torque and a final reversing torque, respectively.a final reaction torque; and step S340 for generating a target current for a motor controller using the final active backlash torque and the final reaction torque and for feeding the generated target current to a motor.

[0174] As in Fig.17, the method for controlling a steer-by-wire system according to some embodiments of the present disclosure may further include steps of: step S440 for detecting a final lock torque when a steering angle reaches a final stop of the steering wheel or a difference between the steering angle and a pinion angle is equal to or greater than a predetermined angle; and step S450 for detecting a damping torque using one or more of the vehicle speed, the steering angle, and a steering angular velocity. In this case, the method may include step S460 for generating the target current for a motor controller further considering the final lock torque and the damping torque in addition to the final active return torque and the final reaction torque.

[0175] The details of the respective steps included in the method for controlling a steer-by-wire system according to the present disclosure can be understood by referring to the above operations of the apparatus for controlling a steer-by-wire system.

[0176] As described above, the steer-by-wire system control apparatus and method according to embodiments of the present disclosure can compensate for the reaction torque by reflecting the column torque from a steering mechanism into the generated command reaction torque when the steering mechanism is in a steer-by-wire system that steers a vehicle by driving a steering motor connected to a rack based on a vehicle speed and a steering angle, and drives a reaction motor to generate a reaction force on the steering wheel. Thus, the apparatus and method can compensate for undesirable steering feel generated by a mechanical linkage, thereby improving a driver's steering feel.

[0177] Furthermore, the apparatus and method may estimate driver torque or rack force and control an active return of the steer-by-wire system using the estimated driver torque or rack force, thereby improving a driver's steering feel.

[0178] Furthermore, the apparatus and method can perform active return control even without a torque sensor or a torsion bar, thereby reducing the manufacturing cost of the steer-by-wire system.

[0179] Although embodiments of the disclosure have been disclosed for illustrative purposes, it will be apparent to those skilled in the art that various modifications, additions, and substitutions are possible without departing from the scope and spirit of the disclosure as defined in the appended claims. Therefore, the true technical scope of the disclosure should be defined by reference to the appended claims.

Claims

[1] Device for controlling a steer-by-wire system with: a reaction torque generator (170) configured to generate a reaction torque as a calculated value of a steering reaction torque applied to a steering wheel; a driver torque estimator (150) configured to detect a driver torque estimate as an estimate of a driver steering torque; a speed controller (140) configured to generate a motor torque command value of a motor-driven power steering system; a torque adjuster (160) configured to calibrate the engine torque command value and the reaction torque based on the driver torque estimate and output them as a final active reversing torque and a final reaction torque; and a target current generator (210) configured to generate a target current for motor control using the final active return torque and the final reaction torque input from the torque adjuster (160), and to feed the generated target current into a motor that provides a reaction force of the steering wheel to a driver. [2] Device according to claim 1, characterized by that the reaction torque generator (170) generates the reaction torque by adding a hysteresis torque based on a steering angular velocity of a steering wheel to a reaction torque based on a rack force. [3] Device according to claim 2, characterized by that the reaction torque generator (170) comprises: a reaction torque decision unit configured to determine the reaction torque based on the rack force, based on a vehicle speed and a rack force estimate of a steering system; a hysteresis torque decision unit configured to to determine the hysteresis torque based on the steering angular velocity of the steering wheel; and a weight application unit configured to calculate the reaction torque by applying a weight to the reaction torque based on the rack force and the hysteresis torque. [4] Device according to claim 3, characterized by that the hysteresis torque decision unit determines the hysteresis torque by a model that determines a hysteresis torque value based on the steering angular velocity. [5] Device according to claim 4, characterized bythat the hysteresis torque decision unit determines the model taking into account the vehicle speed. [6] Device according to claim 3, characterized by that the weight application unit determines a weight between the reaction torque based on the rack force and the hysteresis torque according to the steering angular velocity. [7] Device according to claim 1, characterized by a final lock torque detector (180) configured to detect a final lock torque when the steering angle reaches an end stop of a steering wheel or a difference between the steering angle and a pinion angle is equal to or greater than a predetermined angle, wherein the target current generator (210) generates the target current for the motor control by further using the final lock torque. [8] Device according to claim 7, characterized bythat the final locking torque detector (180) detects the final locking torque based on the steering angle or the rack force estimate. [9] Device according to claim 8, characterized by that the final blocking torque detector (180) comprises: an end stop processing unit (181) configured to detect a torque based on the steering angle from an end stop torque map when the steering angle reaches the end stop of the steering wheel; a curb processing unit (182) configured to detect a torque based on the rack estimate from a curb torque map when the difference between the steering angle and the pinion angle is equal to or greater than the predetermined angle; and an end-lock torque setting unit (187) configured to set the torque detected by the end-stop processing unit (181) or the curb processing unit (182) as the end-lock torque. [10] Device according to claim 1, characterized by a damping torque detector (200) configured to detect a damping torque using one or more of the vehicle speed, the steering angle, and the steering angular speed, wherein the target current generator (210) generates the target current for the motor control by further using the damping torque. [11] Device for controlling a steer-by-wire system comprising: a reaction torque generator (170) configured to generate a reaction torque as a calculated value of a steering reaction torque applied to a steering wheel; a rack force estimator (250) configured to estimate a rack force applied to a rack of a motor-driven power steering system; a speed controller (140) configured to generate a motor torque command value of the motor-driven power steering system; a torque adjuster (160) configured to calibrate the motor torque command value and the reaction torque based on the rack force estimate and output it as a final active return torque and a final reaction torque; and a target current generator (210) configured to generate a target current for motor control using the final active return torque and the final reaction torque input from the torque adjuster (160), and to feed the generated target current into a motor that provides a reaction force of the steering wheel to a driver. [12] Device according to claim 11, characterized by that the reaction torque generator (170) generates the reaction torque by adding the hysteresis torque based on a steering angular velocity of a steering wheel to a reaction torque based on a rack force. [13] Device according to claim 12, characterized by that the reaction torque generator (170) comprises: a reaction torque decision unit configured to to determine the reaction torque based on the rack force based on a vehicle speed and a rack force estimate of a steering system; a hysteresis torque decision unit configured to to determine the hysteresis torque based on the steering angular velocity of the steering wheel; and a weight application unit configured to calculate the reaction torque by applying a weight to the reaction torque based on the rack force and the hysteresis torque. [14] Device according to claim 13, characterized by that the hysteresis torque decision unit determines the hysteresis torque by a model that determines a hysteresis torque value based on the steering angular velocity. [15] Device according to claim 13, characterized bythat the weight application unit determines a weight between the reaction torque based on the rack force and the hysteresis torque according to the steering angular velocity. [16] Device according to claim 11, characterized by a final lock torque detector (180) configured to detect a final lock torque when the steering angle reaches an end stop of a steering wheel or a difference between the steering wheel and a pinion angle is equal to or greater than a predetermined angle, wherein the target current generator (210) generates the target current for the motor control by further using the final lock torque. [17] Device according to claim 16, characterized by that the final locking torque detector (180) detects the final locking torque based on the steering angle or the rack force estimate. [18] Device according to claim 17, characterized bythat the final blocking torque detector (180) comprises: an end stop processing unit (181) configured to detect a torque based on the steering angle from an end stop torque map when the steering angle reaches the end stop of the steering wheel; a curb processing unit (182) configured to detect a torque based on the rack estimate from a curb torque map when the difference between the steering angle and the pinion angle is equal to or greater than the predetermined angle; and a final locking torque setting unit (187) configured to set the torque detected by the end stop processing unit (181) or the curb processing unit (182) as the final locking torque. [19] Device according to claim 11, characterized bya damping torque detector (200) configured to detect a damping torque using one or more of the vehicle speed, the steering angle, and the steering angular speed, wherein the target current generator (210) generates the target current for the motor control by further using the damping torque. [20] Method for controlling a steer-by-wire system comprising the following steps: generating a reaction torque as a calculated value of a steering reaction torque applied to a steering wheel; Detecting a driver torque estimate as an estimate of a driver steering torque or estimating a rack force applied to a rack of a motor-driven power steering system; Generating a motor torque command value of the motor-driven power steering system; Calibrating the engine torque command value and the reaction torque based on the driver torque estimate or the rack force estimate and outputting them as a final active return torque and a final reaction torque; and Generating a target current for a motor controller using the final active return torque and the final reaction torque, and feeding the generated target current to a motor that provides a steering wheel reaction force to a driver.

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