SBW Steering System and Its Method and Device for Generating Steering Wheel Reaction Torque Signal

Abstract

SBW Steering System and Its Method and Device for Generating Steering Wheel Reaction Torque Signal. This disclosure relates to a device and method for generating steering reaction torque. When providing reaction torque to the steering wheel of a steer-by-wire system, the device can determine a target frequency based on the rotational speed of the wheels, generate a filtered rack force signal from which a cut-off frequency band including the target frequency is excluded from the rack force signal, generate a target reaction torque signal based on the filtered rack force signal, and generate reaction torque based on the target reaction torque signal. Therefore, the steering feel of the SBW steering system can be improved by providing the steering wheel with reaction torque from which unnecessary vibration components such as shimmy and chatter are removed.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to an apparatus and method for generating a steering reaction torque, and more particularly, to an apparatus and method for generating a steering reaction torque in which unnecessary vibration components are removed based on wheel speed and rack force in a steer-by-wire system. Background Art

[0002] A steer-by-wire (SBW) steering system of a vehicle refers to a system that uses an electric motor such as a motor to steer the vehicle instead of removing mechanical connection devices such as a steering column, a universal joint, or a pinion shaft between the steering wheel and the wheels.

[0003] The SBW system generally includes an upper device, a lower device, and a control device for controlling them. The upper device may include a torque detection unit connected to the steering wheel to detect a torque applied to the steering wheel, and a steering feedback actuator (SFA) as a motor device to provide a reaction torque to the steering wheel according to steering through a lower rack bar.

[0004] In addition, the lower device may generate a steering assist torque signal proportional to the steering torque applied to the steering wheel, and may control a drive motor or a drive actuator using the steering assist torque signal, and the drive motor or the drive actuator drives a pinion gear or a ball nut mechanism of a rack bar that moves a tie rod connected to the wheels left and right.

[0005] The SBW can operate independently without a mechanical connection between an upper unit including a steering wheel, a steering column, and an SFA and a lower unit including a rack bar drive unit (pinion, ball nut, and a steering motor for driving it).

[0006] Therefore, it is necessary to make the driver feel a steering sensation by rotating the steering wheel connected to the upper device according to the movement of the rack bar of the lower device that performs actual steering. For this purpose, the force or torque applied to the steering wheel may be defined as a reaction force or a reaction torque.

[0007] In addition, during vehicle driving, due to wheel imbalance, poor uniformity, or resonance with the suspension, vibration may occur in the front tires during low-speed or high-speed driving, which is generally referred to as shimmy or wobbling vibration.

[0008] In addition, during vehicle shifting or braking, vibration may occur according to changes in the braking force on the friction surface of the friction clutch or brake, which may be referred to as chatter or shudder vibration.

[0009] In addition, when using SFA to provide a reaction force to the steering wheel, it may be preferable to provide a reaction torque to the steering wheel according to normal steering or to provide an appropriate reaction torque to the steering wheel according to a change in the rack force depending on an external input such as a road surface. However, it is not necessary to reflect in the reaction torque a change in the rack force caused by shimmy or chatter vibration as described above.

[0010] That is, in the case where the SBW system provides a reaction force to the steering wheel, it is necessary to include information about the road surface, but unnecessary information such as shimmy and chatter is removed. SUMMARY OF THE INVENTION

[0011] In this context, one aspect of the present disclosure is to provide an apparatus and method for providing a reaction torque to a steering wheel in a steer-by-wire (SBW) steering system.

[0012] Another aspect of the present disclosure is to provide an apparatus and method capable of providing a reaction torque to a steering wheel in an SBW steering system, from which unnecessary vibration components such as shimmy or chatter are removed.

[0013] Another aspect of the present disclosure is to provide an apparatus and method capable of improving the feeling of feedback torque or reaction torque provided to a steering wheel in an SBW steering system by calculating a reaction torque by attenuating a specific cut-off frequency band in a rack force signal based on the rotational speed of a wheel.

[0014] Another aspect of the present disclosure is to provide an apparatus and method that can, when providing a reaction torque to a steering wheel in an SBW system, determine a target frequency according to the rotational speed of a wheel, generate a filtered rack force signal excluding a cut-off frequency band including the target frequency from the rack force signal, generate a target reaction torque signal based on the filtered rack force signal, and generate a reaction torque based on the target reaction torque signal, so as to provide a reaction torque from which unnecessary vibration components such as shimmy and chatter are removed to the steering wheel to improve the steering feel of the SBW steering system.

[0015] According to one aspect of the present disclosure, there is provided an apparatus for generating a steering reaction torque signal in a steer-by-wire system of a vehicle. The apparatus may include: a target frequency determiner configured to determine a target frequency based on the rotational speed of a wheel; a rack force signal processor configured to generate a filtered rack force signal excluding a cut-off frequency band including the target frequency from a rack force signal of the vehicle; a target reaction torque determiner configured to determine a target reaction torque based on the filtered rack force signal; and a reaction torque signal generator configured to generate a steering reaction torque signal based on the target reaction torque.

[0016] In this case, the target frequency can be determined as the number of revolutions of the wheel per second or a multiple of that number of revolutions. Alternatively, the target frequency can be determined as the value obtained by dividing the moving distance of the vehicle per second by (π × wheel diameter) or a multiple of that value.

[0017] Additionally, the determination of the target frequency, the generation of the filtered rack force signal, the determination of the target reaction torque, and the generation of the steering reaction torque signal can be performed only when a brake pedal operation is detected.

[0018] The rack force signal processor can include a notch filter for generating a filtered rack force signal excluding the cutoff band.

[0019] The rack force signal can be determined based on the steering torque applied to the steering column of the vehicle and the motor torque of the drive motor for moving the rack bar of the SBW system.

[0020] According to another aspect of the present disclosure, there is provided a steer-by-wire system including: a wheel rotation sensor for detecting the rotational speed of a wheel; a reaction torque signal generation device configured to determine a target frequency based on the rotational speed of the wheel, generate a filtered rack force signal excluding a cutoff band including the target frequency from a rack force signal, and generate a steering reaction torque signal based on a target reaction torque determined based on the filtered rack force signal; and a steering feedback actuator for providing a reaction torque to a steering wheel according to the steering reaction torque signal.

[0021] Additionally, according to another aspect of the present disclosure, there is provided a method for generating a steering reaction torque signal in a steer-by-wire system of a vehicle. The method can include: determining a target frequency based on the rotational speed of the wheel; generating a filtered rack force signal excluding a cutoff band including the target frequency from a rack force signal of the vehicle; determining a target reaction torque based on the filtered rack force signal; and generating a steering reaction torque signal based on the target reaction torque.

[0022] According to an embodiment of the present disclosure, a reaction torque from which unnecessary vibration components such as shimmy and chatter are removed can be provided to the steering wheel in an SBW steering system.

[0023] Additionally, according to an embodiment of the present disclosure, the feeling of the feedback torque or the reaction torque provided to the steering wheel in the SBW steering system can be improved by attenuating a specific cutoff band in the rack force signal based on the rotational speed of the wheel to calculate the reaction torque.

[0024] In addition, according to an embodiment of the present disclosure, when providing a reaction torque to the steering wheel in an SBW system, by determining a target frequency based on the rotational speed of the wheels, generating a filtered rack force signal from which a cut-off band including the target frequency is excluded from the rack force signal, generating a target reaction torque signal based on the filtered rack force signal, and generating a reaction torque based on the target reaction torque signal, a reaction torque from which unnecessary vibration components such as shimmy and chatter are removed can be provided to the steering wheel to improve the steering feel of the SBW steering system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Illustrates the configuration of an SBW system in which a steering reaction torque signal generation device according to the present embodiment can be used.

[0026] Figure 2 Is a functional block diagram of an SBW system including a steering reaction torque signal generation device according to the present embodiment.

[0027] Figure 3 Is a configuration diagram illustrating components of a steering reaction torque signal generation device according to the present embodiment.

[0028] Figure 4 Illustrates the steering reaction torque generation principle according to the present embodiment.

[0029] Figure 5 Illustrates an example of a rack force signal including noise components according to the present embodiment.

[0030] Figure 6 Illustrates an example of a filtered rack force signal from which a cut-off band is removed according to the present embodiment.

[0031] Figure 7 Illustrates an example of the mapping relationship between the filtered rack force signal and the target reaction torque according to the present embodiment.

[0032] Figure 8 Illustrates an example of the filtering characteristics of a notch filter used in a rack force signal processor for generating a filtered rack force signal according to the present embodiment.

[0033] Figure 9 Is a flowchart illustrating a method for generating a steering reaction torque signal according to the present embodiment.

[0034] Figure 10 Illustrates an example of a reaction torque signal from which shimmy and chatter vibration components are removed by applying the present embodiment. DETAILED DESCRIPTION

[0035] In the following description of examples or embodiments of the present disclosure, reference will be made to the accompanying drawings, which are shown by way of illustration of specific examples or embodiments that can be implemented, and in the drawings, the same reference numerals and symbols can be used to designate the same or similar components, even when they are shown in different drawings. Further, in the following description of examples or embodiments of the present disclosure, when it is determined that a detailed description of well-known functions and components incorporated herein may make the subject matter in some embodiments of the present disclosure rather unclear, such descriptions will be omitted.

[0036] Terms such as "first", "second", "A", "B", "(A)", or "(B)" may be used in the text to describe elements of the present disclosure. Each of these terms is not used to define the nature, order, sequence, or quantity, etc. of the element, but is only used to distinguish the corresponding element from other elements.

[0037] When it is mentioned that a first element "is connected or coupled" or "contacts or overlaps" with a second element, it should be interpreted that not only can the first element be "directly connected or coupled" or "directly contact or overlap" with the second element, but also a third element can be "interposed" between the first element and the second element, or the first element and the second element can be "connected or coupled", "contact or overlap", etc. with each other via a fourth element. Hereinafter, embodiments will be described in detail with reference to the drawings.

[0038] Figure 1 The configuration of an SBW system in which a steering reaction torque signal generation device according to the present embodiment can be used is illustrated.

[0039] As Figure 1 shown, an SBW system including a steering reaction torque signal generation device according to the present embodiment may include a steering wheel 11, a steering column 12 for supporting the steering wheel, a reaction motor 130 mounted on one side of the steering column 12 and driven by a reaction torque signal generation device 200 and an ECU 140 according to the present embodiment, a sensing unit 110 located on one side of the steering column 12, the reaction motor 130, or a rack bar 20 to detect steering-related information and rack position information, an electronic control unit (ECU) 140 that generates control signals for steering reaction torque and steering assist force based on vehicle speed information through an assist current control map, and one or more drive motors or drive actuators 150 that independently steer each of the left and right wheels 18 of the vehicle according to the control signal of the ECU.

[0040] In this SBW steering system, the reaction motor 130, the steering torque sensor 14 mounted on the steering column, and the steering angle sensor 13 can be represented as a steering feedback actuator (SFA) device that constitutes the upper level of the SBW system. The drive motor or drive actuator 150 for driving the rack bar 20 can be represented as a road wheel actuator (RWA) device that constitutes the lower level of the SBW system.

[0041] In addition, in the rack and pinion type SBW system 1, the steering torque generated by the rotation of the steering wheel 11 can be transmitted to the rack bar 20 through the rack and pinion mechanism, and the steering assist force generated by the drive actuator 150 can be transmitted to the left and right wheels 18 through the tie rod 19 and the rack bar 109.

[0042] The sensing unit 110 may include at least one of the following sensors: a steering angle sensor 13 that detects the rotational change of the steering column 12 that changes according to the driver's manipulation of the steering wheel 11; a torque sensor 14 that is mounted on one side of the reaction motor 130 and the steering column 12 to detect the steering torque applied to the steering column or the reaction torque output from the reaction motor 130; a vehicle speed sensor 15 that is used to detect the vehicle speed; a rack position sensor 16 that is located on the rack bar 20 to detect rack position information; and a motor position sensor 17 that is used to detect the position of the motor rotor of the drive actuator 150 or the reaction motor 130. Alternatively, the sensing unit 110 may receive sensing information from the sensors.

[0043] In addition, the sensing unit 110 may further include a wheel speed sensor that is used to detect the rotational speed of the wheel used in the reaction torque signal generation device 200 according to the present embodiment.

[0044] Optionally, as will be described below, the wheel speed sensor may not be used, and in this case, the rotational speed of the wheel may be determined based on the vehicle speed information from the vehicle speed sensor 15.

[0045] The reaction motor 130 may be mounted on one side of the steering column 12. The reaction motor 130 is a motor that generates a steering reaction force against the steering force applied by the driver to the steering wheel 11 according to a control signal from the reaction torque signal generation device 200 or the ECU 140 of the present embodiment.

[0046] Specifically, based on the sensing information sensed by the sensing unit 110, the reaction torque signal generation device 200 may generate reaction torque control information as described below to drive the reaction motor 130. The ECU 140 may generate a steering assist control signal using an assist current control map and move the rack bar 20 left or right through the drive actuator 150 based on this signal.

[0047] R-EPS (Rack-type EPS) has been illustrated and described as the Figure 1 SBW system in , but hydraulic EPS, C-EPS (Column-type EPS), DP-EPS (Double-pinion type EPS), etc. can be used.

[0048] In addition, the SBW can operate independently without a mechanical connection between the upper unit including the steering wheel, steering column, and SFA and the lower unit including the rack-bar drive unit (pinion, ball nut, and steering motor for driving it).

[0049] Therefore, it is necessary to make the driver feel the steering sensation by rotating the steering wheel connected to the upper device according to the movement of the rack-bar of the lower device that actually performs the steering. For this purpose, the force or torque applied to the steering wheel can be defined as the reaction force or reaction torque.

[0050] In addition, during vehicle driving, due to wheel imbalance, poor uniformity, or resonance with the suspension, vibrations may occur in the front tires during low-speed or high-speed driving, which can generally be referred to as shimmy or wobble vibration.

[0051] In addition, during vehicle shifting or braking, vibrations may occur according to changes in the braking force on the friction surface of the friction clutch or brake, which can be referred to as chatter or shudder vibration.

[0052] In addition, when using the SFA to provide a reaction force to the steering wheel, it may be preferable to provide a reaction torque to the steering wheel according to normal steering or to provide an appropriate reaction torque to the steering wheel according to the change in the rack force depending on external inputs such as the road surface. However, it is not necessary to reflect the change in the rack force caused by shimmy or shudder vibration as described above in the reaction torque.

[0053] That is, in the case where the SBW system provides a reaction force to the steering wheel, it is necessary to include information about the road surface, but unnecessary information such as shimmy and chatter is removed.

[0054] For this purpose, a low-pass filter (LPF) can be used for processing noise components in the low-end information of the SBW system, or a filter for filtering signals in a specific frequency band to avoid hardware resonance.

[0055] However, in the case of using this method, a certain component in the noise component or non-essential signal component can be removed, but the noise whose frequency varies according to the vehicle situation cannot be removed. Specifically, in the case of using a low-pass filter (LPF) that removes low-frequency signal components, the problem is that the necessary information to be reflected when providing the reaction force is also removed.

[0056] Therefore, in the present embodiment, a method can be proposed for improving the feeling of the reaction torque provided to the steering wheel in the SBW steering system by attenuating a certain cut-off frequency band in the rack force signal based on the rotational speed of the wheel. In this specification, the reaction torque can be used with the same meaning as the feedback torque or the reaction force torque, etc.

[0057] Figure 2 is a functional block diagram of an SBW system including a steering reaction torque signal generation device according to the present embodiment.

[0058] The SBW system according to the present embodiment may include: a sensing unit 310 including a wheel rotation sensor 312; a reaction torque signal generation device 200 according to the present embodiment for generating a target reaction torque and a steering reaction torque signal based on the filtered rack force signal; and a steering feedback actuator (SFA) 320 for providing a feedback force, i.e., a reaction torque, to the steering wheel based on the reaction torque signal generated by the reaction torque signal generation device.

[0059] In addition, although not shown, the SBW system according to the present embodiment may further include a drive gear unit connected to the rack bar, a road wheel actuator (RWA) including a drive motor for controlling the movement of the rack bar, and an ECU as a control unit that generates a steering assist signal according to the steering torque applied to the steering wheel to control the road wheel actuator and controls the steering feedback drive unit based on the generated reaction torque signal.

[0060] In addition, in addition to or instead of the wheel rotation sensor 312, the sensing unit 310 may further include a vehicle speed sensor 314.

[0061] In the present embodiment, the reaction torque is controlled based on the wheel rotational speed or the number of revolutions of the wheel per unit time, and the wheel rotational speed can be directly measured using the wheel rotation sensor, or the wheel rotational speed can be estimated based on the vehicle speed information measured by the vehicle speed sensor.

[0062] In addition, the sensing unit 310 of the present embodiment may further include a brake pedal sensor 316, and the reaction torque signal generation device may be activated only when the brake pedal sensor 316 detects the operation of the brake pedal.

[0063] The steering feedback actuator (SFA) 320 may refer to a mechanism and an electronic device for providing a reaction force to the steering wheel based on the reaction torque signal generated by the reaction torque signal generation device, and may include a power transmission mechanism connected to the steering column and a reaction motor for rotating a part of the power transmission mechanism.

[0064] In this case, as an example of the power transmission mechanism, a worm-gear mechanism shaft can be used, which includes a worm connected to the reaction motor shaft and a worm wheel connected to the steering column.

[0065] However, the power transmission mechanism of the SFA 320 is not limited to this, and a belt-pulley type power transmission mechanism can be used, which includes a driving pulley and a driven pulley respectively connected to the reaction motor shaft and the steering column, and a belt provided between the pulleys.

[0066] Figure 3 FIG. is a configuration diagram illustrating components of a steering reaction torque signal generation device according to the present embodiment.

[0067] Refer to Figure 3 , the steering reaction torque signal generation device 200 according to the present embodiment may include a target frequency determiner 210, a rack force signal processor 220, a target reaction torque determiner 230, and a reaction torque signal generator 240.

[0068] The target frequency determiner 210 may determine a target frequency fc based on wheel speed information, which may be measured from a wheel rotation sensor 312 or calculated according to information from a vehicle speed sensor.

[0069] In this case, the target frequency fc may represent the center frequency of a cut-off band that is a frequency band to be removed from the rack force signal.

[0070] The target frequency fc may be determined as the number of revolutions per unit time (e.g., second) of the front wheels or rear wheels of the vehicle or a multiple thereof.

[0071] Alternatively, the target frequency may be determined as a value obtained by dividing the moving distance of the vehicle per unit time (e.g., second) by (π × wheel diameter) or a multiple thereof.

[0072] That is, the target frequency fc can be directly determined from the wheel speed measured by the wheel rotation sensor 312, or can be indirectly calculated from the vehicle speed per second measured by the vehicle speed sensor 314.

[0073] For example, if the rotational speed of the wheel is 30 rpm (revolutions per minute), the target frequency fc may be determined as 30 / 60, that is, 0.5 Hz.

[0074] In the present embodiment, the noise components to be removed when providing the reaction torque may include shimmy noise or chatter noise.

[0075] Shimmy noise is likely to be generated by the rotation of the wheels, especially by resonance with the wheel speed.

[0076] In addition, during shifting or braking, chattering noise may occur according to changes in the braking force on the friction surface of the friction clutch or brake, and this chattering noise may also be related to the rotational speed of the wheel on which the braking device is provided.

[0077] Therefore, in the present embodiment, in order to remove the noise component corresponding to the wheel rotational speed when providing a reaction torque to the steering wheel in the SBW system, the following configuration may be provided: removing a predetermined cut-off band in the rack force signal and then determining the reaction torque based thereon.

[0078] In a general electric power steering device, since the rack bar is directly connected to the steering column through a pinion, shimmy or chatter can be directly transmitted to the steering wheel.

[0079] Therefore, in a conventional electric power steering system, a method of determining the assist steering force by directly measuring or estimating shimmy vibration or chatter vibration has been used.

[0080] However, in the SBW steering system to which the present embodiment can be applied, since the RWA device for driving the rack bar and the SFA device connected to the steering wheel are mechanically separated, it is difficult to apply the technique for removing shimmy vibration or chatter vibration of a general electric power steering device.

[0081] Therefore, in the present embodiment, the following method is provided: It is possible to effectively attenuate shimmy or chatter noise in the SBW system by removing a part of the rack force signal for calculating the reaction torque based on the wheel rotational speed and generating a steering wheel reaction torque accordingly.

[0082] The rack force signal processor 220 may perform an operation for generating a filtered rack force signal that excludes a cut-off band including a target frequency fc from the rack force signal of the vehicle.

[0083] The rack force signal processor 220 may be implemented using a notch filter that is designed to have a target frequency fc and a specific margin frequency Δf on both sides of the target frequency fc.

[0084] The notch filter is used to remove the rack force component corresponding to the shimmy / chatter noise component from the measured or estimated rack force signal. In this case, the margin frequency Δf may be appropriately set as a tuning parameter according to the required accuracy of the reaction torque.

[0085] That is, as the margin frequency Δf increases, many sensations caused by shimmy / chatter noise can be removed, and as the margin frequency is set small, less noise can be removed.

[0086] Therefore, if the frequency band of the noise component detected in the estimated rack force signal is large, the margin frequency can be set higher.

[0087] In addition, according to the driver's selection or the like, the margin frequency can be set high in the silent mode to minimize the feeling caused by external influences. Conversely, in the dynamic mode, the margin frequency can be set low to dynamically feel the steering feeling caused by external influences.

[0088] Furthermore, based on the steering torque applied to the vehicle steering column, the motor torque of the drive motor for moving the rack bar of the SBW system, the angle of the pinion, etc., the rack force signal according to the present embodiment can be estimated.

[0089] Below will refer to Figure 5 Describe in more detail the manner of determining the rack force signal.

[0090] In addition, the target reaction torque determiner 230 in the reaction torque signal generation device 200 according to the present embodiment can determine the target reaction torque based on the filtered rack force signal.

[0091] That is, the target reaction torque determiner 230 can determine the filtered rack force signal obtained by removing the cut-off band from the estimated rack force, and then can determine the corresponding target reaction torque value based on the filtered rack force signal.

[0092] The target reaction torque value corresponding to the filtered rack force signal can be determined according to a specific tuning map.

[0093] The reaction torque signal generator 240 can generate a reaction torque signal corresponding to the determined target reaction torque.

[0094] The reaction torque signal is provided to the steering feedback actuator 320 or the reaction motor, and accordingly, a feedback force, that is, a reaction force, is applied to the steering wheel by driving the reaction motor.

[0095] In addition, the SBW steering system according to the present embodiment may further include a brake pedal sensor 316, and the reaction torque signal generation device 200 can be activated only when the brake pedal sensor 316 detects the operation of the brake pedal.

[0096] Among the noises to be removed in the present embodiment, the chatter noise is generated according to the change in the braking force on the friction surface of the friction clutch or brake during braking.

[0097] Therefore, as described above, the brake pedal sensor is used to detect the operation of the brake pedal, and the present embodiment can be applied only during the braking operation, so as to more accurately remove the noise.

[0098] Figure 4Illustrates the steering reaction torque generation principle according to the present embodiment.

[0099] Referring to Figure 4 , the rotational speed information and brake pedal information of the front and rear wheels of the vehicle can be applied to the cut-off target frequency calculation module (M410), and the target frequency can be calculated in the cut-off target frequency calculation module (M410) according to a predetermined algorithm. The calculated target frequency can be applied to the rack force signal processing module M420. For example, when the wheel rotational speed information calculated based on the information of the wheel rotation sensor or the vehicle speed sensor is applied, the cut-off target frequency calculation module can calculate the target frequency based on the applied information. As another example, the cut-off target frequency calculation module can calculate the target frequency based on the wheel rotational speed information only when the motion detection information of the brake pedal is applied from the brake pedal sensor.

[0100] In addition, the rack force signal processing module M420 can pass the input or estimated rack force signal through an adaptive filter determined according to the target frequency, such as a notch filter.

[0101] The filtered rack force signal can be output from the adaptive filter, and the filtered rack force signal can be input to the reaction torque signal generation module M430.

[0102] The reaction torque signal generation module M430 can determine the reaction torque value corresponding to the filtered rack force value according to a predetermined tuning map, and generate and output the corresponding reaction torque signal.

[0103] The output reaction torque signal is transmitted to the reaction motor to apply a reaction force to the steering column.

[0104] As described above, according to the present embodiment, a filtered rack force signal can be generated outside of a predetermined cut-off frequency band including the target frequency corresponding to the wheel rotational speed, and a steering reaction torque signal can be generated based on the filtered rack force signal. Therefore, a reaction torque removing unnecessary vibration components such as shimmy and chatter can be provided to the steering wheel to improve the steering feel of the SBW steering system.

[0105] The rack force signal used in the embodiments of the present disclosure can be based on the pinion of the vehicle steering system. Specifically, by using the state equation calculated based on the first modeling analysis for the steering control device side not including the pinion and the second modeling analysis for the drive motor side including the pinion, at least one of the rack force, the estimated angle of the pinion, and the estimated angular velocity of the pinion can be estimated.

[0106] In addition, by using the driving motor torque calculated based on the motor current, the angle estimation error of the pinion gear calculated by subtracting the estimated angle of the pinion gear from the angle of the pinion gear, and the column torque, at least one of the final rack force, the estimated angle of the pinion gear, and the estimated angular velocity of the pinion gear can be estimated.

[0107] In this way, the rack force signal can be determined.

[0108] In addition, when calculating the rack force signal, it has been assumed that the RWA device includes a driving motor, a power transmission mechanism such as a ball screw gear and a belt, and a mechanism part in which the pinion gear and the rack bar are further separately connected.

[0109] However, the calculation or estimation of the rack force signal is not limited to the above structure and method, and the rack force signal can be calculated according to another functional relationship using the motor torque and the steering torque of the driving motor as variables.

[0110] Figure 5 Examples of the rack force signal including noise components according to the present embodiment are illustrated, and Figure 6 Examples of the filtered rack force signal from which the cut-off frequency band is removed according to the present embodiment are illustrated.

[0111] In Figure 5 and Figure 6 In both cases, the above figures illustrate the signals in the time domain and the frequency domain.

[0112] As Figure 5 shown in the above figure of , a typical rack force signal Frack may periodically include a peak component Ni at a specific time ti in the time domain.

[0113] That is, according to the present embodiment, the peak component generated for each Δt may become a shimmy noise component or a chatter noise component related to the wheel rotation.

[0114] Such a noise component can be represented as a peak component at a specific frequency in the frequency domain, as Figure 5 shown in the following figure of , and the peak frequency can be the target frequency fc in the present embodiment.

[0115] That is, the target frequency fc of the present embodiment can be Figure 5 the reciprocal of the period Δt at which the peak is generated in the above figure of . Therefore, the target frequency can correspond to the number of revolutions (rotational speed) of the wheel per second or a multiple thereof.

[0116] The rack force signal processor 220 according to the present embodiment can output a filtered rack force signal F'rack from which the cut-off frequency band including the target frequency is removed.

[0117] As Figure 6As shown, the filtered rack force signal F'rack is a signal from which noise components (peaks) in a specific frequency band related to wheel rotation, as shown in Figure 5 are removed.

[0118] Figure 7 FIG. illustrates an example of the mapping relationship between the filtered rack force signal and the target reaction torque according to the present embodiment.

[0119] Referring to Figure 7 , there may be a specific proportional relationship between the filtered rack force signal F'rack and the target reaction torque Tr value, and there may be a specific hysteresis according to the steering toward the rack end and the steering back to the center.

[0120] In addition, the target reaction torque Tr may have a specific saturation relationship. That is, above a specific filtered rack force signal F'rack, the target reaction torque Tr may have a constant maximum value.

[0121] The relationship between the filtered rack force signal F'rack and the target reaction torque Tr is not limited to the Figure 7 example, and may have a specific other relationship.

[0122] The relationship between the filtered rack force signal F'rack and the target reaction torque Tr can be defined as a tuning map as shown in Figure 7 , but is not limited thereto, and may also be defined in the form of a preset look-up table.

[0123] Figure 8 FIG. illustrates an example of the filtering characteristics of the notch filter used in the rack force signal processor for generating the filtered rack force signal according to the present embodiment.

[0124] The rack force signal processor 220 according to the present embodiment can be implemented as a notch filter or an adaptive filter that attenuates a signal in a predetermined cut-off frequency band including the target frequency fc by a predetermined amount or more.

[0125] As shown in Figure 8 , the notch filter can be designed to have a specific margin frequency Δf on both sides of the target frequency fc. In addition, the notch filter can be designed such that the attenuation rate is maximum at the target frequency fc and decreases toward both sides of the target frequency fc.

[0126] The notch filter can allow signals exceeding the margin frequency Δf on both sides of the target frequency fc to pass through without attenuation.

[0127] As described above, the notch filter is used to remove the rack force component corresponding to the shimmy / chatter noise component from the measured or estimated rack force signal.

[0128] In this case, as the margin frequency Δf increases, more shimmy / chatter noise sensation can be removed, and the smaller the margin frequency, the less noise is removed. Therefore, the margin frequency Δf can be appropriately set as a tuning parameter according to the required accuracy of the reaction torque.

[0129] Therefore, in the case where the frequency band of the noise component detected in the estimated rack force signal is large, the margin frequency can be set high.

[0130] In addition, according to the driver's selection or the like, the margin frequency can be set high in the silent mode to minimize the sensation caused by external influences. Conversely, in the dynamic mode, the margin frequency can be set low to dynamically feel the steering sensation caused by external influences.

[0131] Alternatively, after detecting vehicle vibration, in a driving environment where the influence of vibration caused by wheel rotation is large, such as an off-road environment, the margin frequency can be set large, and in a stable driving environment such as highway driving, a small margin frequency can be set.

[0132] Figure 10 An example of a reaction torque signal from which shimmy and chatter vibration components are removed by applying the present embodiment is illustrated.

[0133] According to the above configuration, the reaction torque signal generator 240 can generate a reaction torque signal corresponding to the determined target reaction torque.

[0134] In the reaction torque signal St output at this time, as Figure 10 shown, the noise components repeatedly included according to the wheel speed can be removed.

[0135] As described above, according to the present embodiment, by dynamically setting the margin frequency of the notch filter used as the rack force signal processor according to the driving environment (mode) or the driver's selection, the reaction torque of the steering wheel can be controlled more precisely.

[0136] Furthermore, the reaction torque signal generation device 200 according to the present embodiment as described above, and the target frequency determiner 210, the rack force signal processor 220, the target reaction torque determiner 230, and the reaction torque signal generator 240 included therein can be implemented as part of a control device or an ECU of an SBW steering system.

[0137] Such a control device or ECU of the SBW steering system may include a processor, a storage device such as a memory, and a computer program capable of performing specific functions. In addition, the target frequency determiner 210, the rack force signal processor 220, the target reaction torque determiner 230, and the reaction torque signal generator 240 may be implemented as software modules capable of performing each corresponding function.

[0138] That is, the target frequency determiner 210, the rack force signal processor 220, the target reaction torque determiner 230, and the reaction torque signal generator 240 as described above may be implemented as corresponding software modules and stored in the memory, and each software module may be executed in an arithmetic processing device such as an ECU included in the SBW steering system at a specific time.

[0139] Figure 9 is a flowchart illustrating a method for generating a steering reaction torque signal according to the present embodiment.

[0140] Refer to Figure 9 , the method for generating a steering reaction torque signal according to the present embodiment may include: a step (S1010) of determining a target frequency based on the rotational speed of the wheel; a step (S1020) of generating a filtered rack force signal obtained by excluding a cut-off band including the target frequency from the rack force signal of the vehicle; a step (S1030) of determining a target reaction torque based on the filtered rack force signal; and a step (S1040) of generating a steering reaction torque signal based on the target reaction torque.

[0141] The method for generating the steering reaction torque signal of the SBW system may be executed by the steering reaction torque signal generation device described with reference to Figures 2 to 8 and a detailed description will be omitted to avoid repetition.

[0142] In addition, in this case, the target frequency may be determined as the number of revolutions of the wheel per second or a multiple of the number of revolutions. Alternatively, the target frequency may be determined as a value obtained by dividing the moving distance of the vehicle per second by (π × wheel diameter) or a multiple of the value.

[0143] In addition, the target frequency determination (S1010), the filtered rack force signal generation (S1020), the target reaction torque determination (S1030), and the steering reaction torque signal generation (S1040) may be executed only when a brake pedal operation is detected.

[0144] As described above, according to the present embodiment, a filtered rack force signal can be generated except for a predetermined cut-off band including a target frequency corresponding to the wheel speed, and a steering reaction torque signal can be generated based on the filtered rack force signal. Therefore, a reaction torque from which unnecessary vibration components such as shimmy and chatter are removed can be provided to the steering wheel to improve the steering feel of the SBW steering system.

[0145] It should be noted that although all or some of the configurations or elements included in the above-described one or more embodiments have been combined to form a single configuration or component or operate in combination, the present disclosure is not necessarily limited thereto. That is, within the scope of the purpose or spirit of the present disclosure, all or some of the configurations or elements included in the one or more embodiments can be combined to form one or more configurations or components or operate as such combined configurations or components. In addition, each configuration or element included in the one or more embodiments can be implemented by an independent hardware configuration; however, some or all of the configurations or elements can be selectively combined and implemented by one or more computer programs having one or more program modules that execute some or all of the functions of the one or more combined hardware configurations. Those skilled in the art can easily generate the code or code segments constituting the computer program. Since the computer program stored in the computer-readable medium is read and executed by the computer, the embodiments of the present disclosure can be implemented. The medium for storing the computer program can include, for example, a magnetic storage medium, an optical recording medium, and a carrier medium.

[0146] In addition, unless otherwise specified herein, the terms "comprising", "including", "constituting", "having", etc. described herein mean that in the corresponding configuration or element, one or more other configurations or elements can be further included. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as understood by those skilled in the art. Unless otherwise defined herein, the terms commonly used (such as those defined in a dictionary) should be interpreted as having the same meaning as in the context of the related art and should not be interpreted as idealized or overly formal meanings.

[0147] The above description is provided to enable those skilled in the art to implement and use the technical idea of the present disclosure, and is provided in the context of a specific application and its requirements. Various modifications, additions, and substitutions to the described embodiments will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. For illustrative purposes only, the above description and drawings provide examples of the technical idea of the present disclosure. That is, the disclosed embodiments are intended to illustrate the scope of the technical idea of the present disclosure. Therefore, the scope of the present disclosure is not limited to the illustrated embodiments, but conforms to the broadest scope consistent with the claims. The protection scope of the present disclosure should be interpreted based on the appended claims, and all technical ideas within the scope of their equivalents should be construed as being included in the protection scope of the present disclosure.

[0148] Cross-reference to related applications

[0149] This application claims the priority of Korean Patent Application No. 10-2020-0079255, filed on Jun. 29, 2020, which is incorporated herein by reference for all purposes as if fully set forth herein.

Claims

1. An apparatus for generating a steering reaction torque signal in a steer-by-wire system of a vehicle, the apparatus comprising: A target frequency determiner configured to determine a target frequency based on a rotational speed of a wheel when the vehicle is in a moving state, the target frequency being determined as (i) the number of revolutions of the wheel per second or a multiple of the number of revolutions, or (ii) a value obtained by dividing a moving distance of the vehicle per second by π and then by a wheel diameter, or a multiple of the value; A rack force signal processor configured to generate a filtered rack force signal by excluding a cut-off band including the target frequency from a rack force signal of the vehicle, the rack force signal being determined based on a steering torque applied to a steering column of the vehicle and a motor torque of a drive motor for moving a rack bar of the steer-by-wire system; A target reaction torque determiner configured to determine a target reaction torque based on the filtered rack force signal; And A reaction torque signal generator configured to generate a steering reaction torque signal based on the target reaction torque, wherein the rack force signal processor is configured to generate the filtered rack force signal excluding the cut-off band using a notch filter, the notch filter being set to have specific margin frequencies on both sides of the target frequency, and the specific margin frequencies are set differently according to a driving environment or a driving mode of the vehicle.

2. The device according to claim 1, wherein The determination of the target frequency, the generation of the filtered rack force signal, the determination of the target reaction torque, and the generation of the steering reaction torque signal are performed only when a brake pedal operation is detected.

3. The apparatus according to claim 1, wherein the specific margin frequencies are set high in a silent mode and set low in a dynamic mode.

4. The apparatus according to claim 1, wherein after detecting vehicle vibration, in a driving environment where the influence of vibration caused by wheel rotation is large, the specific margin frequencies are set large, and in a stable driving environment, the specific margin frequencies are set small.

5. A steer-by-wire system of a vehicle, the steer-by-wire system comprising: A wheel rotation sensor configured to detect a rotational speed of a wheel; A reaction torque signal generation apparatus configured to: determine a target frequency based on the rotational speed of the wheel when the vehicle is in a moving state, the target frequency being determined as (i) the number of revolutions of the wheel per second or a multiple of the number of revolutions, or (ii) a value obtained by dividing a moving distance of the vehicle per second by π and then by a wheel diameter, or a multiple of the value; generate a filtered rack force signal by excluding a cut-off band including the target frequency from a rack force signal, the rack force signal being determined based on a steering torque applied to a steering column of the vehicle and a motor torque of a drive motor for moving a rack bar of the steer-by-wire system; and generate a steering reaction torque signal based on a target reaction torque determined based on the filtered rack force signal; And A steering feedback actuator for providing a reaction torque to a steering wheel according to the steering reaction torque signal, wherein the rack force signal processor is configured to generate the filtered rack force signal excluding the cutoff band using a notch filter, the notch filter being set to have specific margin frequencies on both sides of the target frequency, and the specific margin frequencies are set differently according to the driving environment or driving mode of the vehicle.

6. The steer-by-wire system according to claim 5, further comprising a brake pedal sensor that detects an operation of a brake pedal of the vehicle, Among them, and activating the reaction torque signal generating means only when the brake pedal sensor detects an operation of the brake pedal.

7. A method for generating a steering reaction torque signal in a steer-by-wire system of a vehicle, the method comprising the steps of: determining a target frequency based on the rotational speed of a wheel when the vehicle is in a moving state, the target frequency being determined as (i) the number of revolutions of the wheel per second or a multiple of the number of revolutions or (ii) a value obtained by dividing the moving distance of the vehicle per second by π and then by the wheel diameter or a multiple of the value; generating a filtered rack force signal excluding a cutoff band including the target frequency from a rack force signal of the vehicle, the rack force signal being determined based on a steering torque applied to a steering column of the vehicle and a motor torque of a drive motor for moving a rack bar of the steer-by-wire system; determining a target reaction torque based on the filtered rack force signal; and generating a steering reaction torque signal based on the target reaction torque, wherein the rack force signal processor is configured to generate the filtered rack force signal excluding the cutoff band using a notch filter, the notch filter being set to have specific margin frequencies on both sides of the target frequency, and the specific margin frequencies are set differently according to the driving environment or driving mode of the vehicle.

8. The method according to claim 7, wherein Performing the target frequency determination, the filtered rack force signal generation, the target reaction torque determination, and the steering reaction torque signal generation only when a brake pedal operation is detected.

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