Steering control device and steering control method for vehicle

Abstract

Steering control device (110) of a vehicle comprising the following: a condition determination unit (310) that determines a steering ratio change condition (S810) by determining whether a failure or emergency steering occurs in a steering motor (210) or steering motor control device (220, 230) of the vehicle equipped with a steer-by-wire system; a steering ratio change unit (320) that changes a mean steering ratio (S820) when the steering ratio change condition is determined to be satisfied; and a control device (330) that controls a steering motor output (S830) and adjusts a rack stroke and rack speed based on the changed mean steering ratio; characterized in that the mean steering ratio is changed using a virtual C-factor, wherein the steering ratio changing unit (320) is configured to change the mean steering ratio by reducing the virtual C-factor when the speed of the vehicle increases.

Description

Area

[0001] The present embodiments relate to a steering control device of a vehicle according to the preamble of claim 1 and a steering control method of a vehicle according to the preamble of claim 8. Description of the state of the art

[0002] A vehicle steering system refers to a system in which the driver of a vehicle can change the steering angle of a vehicle's wheels based on the steering force (or rotational force) applied to the steering wheel. The Electric Power Steering System (EPS) has been applied to vehicles to reduce the steering force of the steering wheel to ensure stability of a steering condition. Research on steer-by-wire vehicle steering devices has been continuously intensively pursued. In such a steer-by-wire vehicle steering device, the steering column module connected to the steering wheel and the steering rack module connected to the wheels are mechanically separated from each other. The steer-by-wire vehicle steering device does not need to adjust the angles of the steering wheel and the wheel, so it is possible to change the angles of the steering wheel and the wheel freely.

[0003] In particular, in vehicle steering systems, increasing interest is shifting from systems that conventionally use a single control device to control the vehicle to redundant system application steering, which adopts two or more control devices to control the vehicle's steering. However, if one control device in the steering control system implementing the redundant system fails, it is severely limited in its ability to provide the power steering force required by the driver using only the remaining normal control devices. Accordingly, there is a need for a technology capable of providing stable power steering even when a failure or accident occurs and the driver performs emergency steering.

[0004] DE 10 2016 208 775 A1 and DE 198 41 913 A1 show generic steering control devices of a vehicle. SUMMARY

[0005] In the above background, the present embodiments provide a steering control apparatus and a steering control method for a vehicle that ensure stable steered driving by controlling the output of the steering motor, changing the center steering ratio when the driver initiates emergency steering in a failure situation, and adjusting the rack stroke and the rack speed.

[0006] The invention is defined by the appended claims. The following description is subject to this limitation. Any disclosure outside the scope of the claims is intended for illustrative and comparative purposes only.

[0007] According to a first aspect, the present embodiments provide a steering control device of a vehicle, including a condition determining unit that determines a steering ratio change condition by determining whether a failure or emergency steering occurs in a steering motor or a steering motor control device of the vehicle equipped with a steer-by-wire system, a steering ratio changing unit that changes an average steering ratio using a preset virtual C-factor when the steering ratio change condition is determined to be satisfied, and a control device that controls a steering motor output and adjusts a rack stroke and a rack speed based on the changed steering ratio.

[0008] According to a second aspect, the present embodiments provide a steering control method of a vehicle, including a condition determining step that determines a steering ratio change condition by determining whether a failure or emergency steering occurs in a steering motor or a steering motor control device of the vehicle equipped with a steer-by-wire system, a steering ratio changing step that changes an average steering ratio using a preset virtual C-factor when the steering ratio change condition is determined to be satisfied, and a control step that controls a steering motor output and adjusts a rack stroke and a rack speed based on the average steering ratio.

[0009] According to the present embodiments, a steering control apparatus and a steering control method for a vehicle are provided which ensure stable driving by controlling the output of the steering motor by changing the center steering ratio when the driver initiates emergency steering in a failure situation, and adjusting the rack stroke and the rack speed. DESCRIPTION OF THE DRAWINGS

[0010] The above and other objects, features and advantages of the disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings in which: Fig. 1 is a view illustrating an overall configuration of a steer-by-wire vehicle steering apparatus according to an embodiment of the disclosure; Fig. 2 is a view illustrating a configuration of a steering apparatus of a vehicle to which a redundant system is applied according to an embodiment of the disclosure; Fig. 3 is a view illustrating a configuration of a vehicle steering control device according to an embodiment; Fig. 4 is a flowchart illustrating an operation of controlling by changing an average steering ratio of a steering control device of a vehicle according to an embodiment of the disclosure; Fig. 5 is a view illustrating a relationship between rack stroke and rack speed in a steering control device of a vehicle according to an embodiment of the disclosure; Fig. 6 is a flowchart illustrating an operation for adjusting the steering rack by changing an average steering ratio of a steering control device of a vehicle according to an embodiment of the disclosure; Fig. 7 is a view illustrating an operation for adjusting the rack stroke by controlling the steering motor output of a steering control device of a vehicle according to an embodiment of the disclosure; and Fig. 8 is a flowchart illustrating a vehicle steering control method according to an embodiment of the disclosure. DETAILED DESCRIPTION

[0011] The disclosure relates to a vehicle steering control apparatus and a vehicle steering control method.

[0012] In the following description of examples or embodiments of the disclosure, reference is made to the accompanying drawings, in which specific examples or embodiments that may be implemented are shown by way of illustration, and in which the same reference numbers and symbols may be used to designate the same or similar components even if they are shown in different accompanying drawings. Furthermore, in the following description of examples or embodiments of the disclosure, detailed descriptions of well-known functions and components incorporated herein are omitted when it is determined that the description would tend to obscure the subject matter in such embodiments of the disclosure.Terms such as "including," "having," "containing," "constituting," "consisting of," and "formed of" used herein are generally intended to permit the addition of other components, unless the terms are used with the term "only." As used herein, singular forms are intended to include plural forms unless the context clearly indicates otherwise.

[0013] Terms such as "first," "second," "A," "B," "(A)," "(B)," or the like may be used herein to describe elements of the disclosure. Each of these terms is not used to define the nature, order, sequence, or number of elements, etc., but is used merely to distinguish the corresponding elements from other elements.

[0014] When it is mentioned that a first element is “connected or coupled” to a second element, “touches or overlaps” it, etc., this should be interpreted to mean that the first element is not only “directly connected or coupled” to or “directly touches or overlaps” the second element, but that a third element may also be “interposed” between the first and second elements, or that the first and second elements may be “connected or coupled” to each other via a fourth element, “touch or overlap” each other, etc. Here, the second element may be included in at least one of two or more elements that are “connected or coupled,” “touch or overlap” each other, etc.

[0015] When time-related terms such as "after," "following," "next," "before," and the like are used to describe processes or operations of elements or configurations or sequences or steps of operation, processing, or manufacturing methods, these terms may be used to describe non-consecutive or non-sequential processes or operations, unless the term "direct" or "immediate" is used simultaneously.

[0016] When dimensions, relative sizes, etc., are additionally mentioned, it should be considered that numerical values ​​for elements or characteristics, or corresponding information (e.g., level, rank, etc.), include a range of tolerance or error that may be caused by various factors (e.g., process factors, internal or external impact, noise, etc.), even if a relevant description is not specified. Furthermore, the term "may" includes all meanings of the term "can."

[0017] Fig. 1 is a view illustrating an overall configuration of a steer-by-wire vehicle steering apparatus according to an embodiment of the disclosure.

[0018] With reference to Fig. 1, a steer-by-wire based vehicle steering apparatus according to an embodiment of the disclosure may include a steering wheel 100, a steering column module (SCM) 120, a steering rack module (SRM) 130, a control module 110, and a wheel 140.

[0019] The steering wheel 100 can be operated by the driver's input. For example, the steering wheel 100 can be rotated by the driver's input and can determine or change the direction of the vehicle based thereon.

[0020] The steering column module 120 may be connected to the steering wheel 100. The steering column module 120 may include a steering shaft, a reaction force motor, and each sensor. For example, the steering shaft may be connected to the steering wheel 100. If the steering wheel 100 rotates, the steering shaft may rotate in response to the rotating steering wheel 100. The reaction force motor may be connected to the steering shaft. The reaction force motor may rotate in a direction opposite to the rotation direction of the steering wheel 100 to provide a steering reaction force to the steering wheel 100 so that the driver can feel a suitable steering feel. Each sensor may include at least one of a steering angle sensor, a torque sensor, or a steering angular velocity sensor. However, the type of sensor is not limited to these as long as it can measure the states of various components included in the steering column module 120.For example, the steering angle sensor can measure the steering angle, which is the rotation angle of the steering wheel 100. The torque sensor can measure the torque generated at the steering shaft as the steering wheel 100 rotates. The steering angular velocity sensor can measure the steering angular velocity, which is the rotation angular velocity of the steering wheel 100.

[0021] The steering rack module 130 may be mechanically separated from the steering column module 120. The steering rack module 130 may include a steering motor (drive motor), a pinion gear, a rack, and any sensors. The steering motor may be driven, for example, by a drive current. The steering motor may generate a drive torque corresponding to the drive current and may provide a steering force to the steering wheel 100 based on the generated drive torque. The pinion gear may be connected to the steering motor. The pinion gear may rotate based on the drive torque generated by the steering motor. The rack gear may be connected to the pinion gear. The rack gear may perform a linear motion based on the rotation of the pinion gear. In other words, the pinion gear and the rack gear may provide a steering force to the steering wheel 100 based on the drive torque of the steering motor to change the direction of the steering wheel 100.Each sensor may include at least one of a rack position sensor, a rack displacement sensor, a pinion angle sensor, or a pinion angular velocity sensor. However, the type of sensor is not limited to these, as long as it can measure the states of various components included in the steering rack module 130. For example, the rack position sensor may measure the position of the rack, and the rack displacement sensor may measure the displacement of the rack. The pinion angle sensor may measure the pinion angle, which is the rotation angle of the pinion. The pinion angular velocity sensor may measure a pinion angular velocity, which is the rotation angular velocity of the pinion.

[0022] The control module 110 may control the operation of the steering column module 120 and the steering rack module 130. For example, the control module 110 may receive information from each of the components included in the steering column module 120 and the steering rack module 130, generate a steering control signal using the received information, and control the operation of each component included in the steering column module 120 and the steering rack module 130 based on the generated steering control signal. As another example, the control module 110 may control the operation of each sensor disposed on the vehicle. The control module 110 may control the operation of each sensor disposed on the vehicle, generate each control signal based on each piece of information therefrom, and control the operation of each component included in the steering column module 120 and the steering rack module 130 using each generated control signal.The control module 110 may represent a steering control device. The control module 110 is described in detail below with reference to FIG. Fig. 2 to 8 described.

[0023] The wheel 140 may be connected to the steering rack module 130. For example, the rotational force of the steering motor may be converted into a linear motion force in the axial direction of the rack while being transferred to the rack using a reduction gear provided between the steering motor and the rack. The linear motion force of the rack may be transmitted to the wheel 140, which is connected by a tie rod and a steering arm.

[0024] Fig. 2 is a view illustrating a configuration of a steering apparatus of a vehicle to which a redundant system is applied according to an embodiment of the disclosure.

[0025] With reference to Fig. 2, the steering device 110 of the vehicle according to one embodiment of the disclosure may implement a redundant system including a plurality of steering motor control devices. For example, the plurality of steering motor control devices 220 and 230 may be implemented with an electronic control unit (ECU) including a motor control unit (MCU), an inverter, and a printed circuit board (PCB) (not shown), as well as software. For example, the first steering motor control device 220 may include a first MCU 221 and a first inverter 222, and the second steering control device 230 may include a second MCU 231 and a second inverter 232. However, embodiments of the disclosure are not limited thereto.

[0026] Furthermore, the steering devices 110 of the vehicle may be electrically connected to each other to implement a redundant system. For example, the first steering motor control device 220 and the second steering motor control device 230 may be electrically connected. By being electrically connected, the plurality of steering motor control devices can internally perform mutual communication and transfer or receive their respective status information. As a specific example, when the first steering motor control device 220 is in a failure state (or abnormal state), the first steering motor control device 220 may output an electrical signal indicating the status information about the first steering motor control device 220 to the second steering motor control device 230.The second steering motor control device 230 may receive the electrical signal output from the first steering motor control device 220 to know the state of the first steering motor control device 220. In this case, the electrical signal may be implemented in the form of a flag.

[0027] In the vehicle's steering control device 110, a plurality of winding motors included in the dual-winding steering motor 210 may be electrically connected to the steering motor control devices, respectively. For example, the first inverter 222 included in the first steering motor control device 220 may be electrically connected to the first winding motor 211 included in the steering motor 210. The second inverter 232 included in the second steering motor control device 230 may be electrically connected to the second winding motor 212 included in the steering motor 210.

[0028] The steering motor controllers 220 and 230 can calculate a target rack stroke based on the steering information and can calculate the target command current corresponding to each target rack stroke. For example, the first MCU 221 included in the first steering motor controller 220 can calculate a target rack stroke and a target command current. In this case, the steering motor controller can calculate a command current for finally applying the target command current to the steering motor 210, considering the state information of the other steering motor controller.

[0029] Each of the steering motor controllers 220 and 230 can calculate a portion of the target command current when the other steering motor controller is abnormal or fails. For example, when the first steering motor controller 220 and the second steering motor controller 230 are normal or not failing, the first MCU 221 and the second MCU 231 can each calculate half of the target command current.

[0030] If one of the plurality of steering motor control devices fails, the vehicle's steering control device 110 may implement restricted driving on the vehicle using the remaining normal steering motor control device to prevent accidents. In other words, the normal steering motor control device may operate the steering motor 210 using the command current corresponding to a preset reference rack stroke as a limit range to prevent burnout due to overheating. As a specific example, if the second steering motor control device 230 fails due to a failure in, for example, the second MCU 231 or the second inverter 232, the second steering control device 230 may generate a signal and output the signal to the first steering motor control device 220.If the first steering motor control device 220 receives the failure signal from the second steering motor control device 230, the first steering motor control device 220 can use the first winding motor 211 as a limit range by using half of the command current corresponding to the end of the rack. Accordingly, the range of the rack stroke can be reduced. Accordingly, the vehicle steering device 110 can change the average steering ratio to generate the steering motor output at 0% and 100% at a preset period to increase the rack stroke with insufficient output.

[0031] Fig. 3 is a view illustrating a configuration of a vehicle steering control device according to an embodiment.

[0032] With reference to Fig. 3, according to an embodiment of the disclosure, a steering control device 110 of a vehicle may include a condition determination unit 310 that determines whether a failure occurs and whether emergency steering occurs in a steering motor or a steering motor control device in the vehicle having the steer-by-wire system to determine a steering ratio change condition, wherein a steering ratio change unit 320, upon determining that the steering ratio change condition is satisfied, changes the average steering ratio using a preset virtual C-factor, and wherein a controller 330 controls the steering motor output based on the changed average steering ratio and adjusts the rack stroke and the rack speed.

[0033] The condition determination unit 310 may determine the steering ratio change condition by determining whether a failure or emergency steering occurs in the steering motor or the steering motor control device of the vehicle equipped with the steer-by-wire system. For example, the condition determination unit 310 may determine that the steering ratio change condition is met when a failure and emergency steering occur. For example, the condition determination unit 310 may determine that a failure occurs if a failure occurrence signal is detected. The failure occurrence signal may be a flag indicating the failure generated by the steering motor control device.Specifically, the failure occurrence signal may be detected in a situation where overheating occurs due to an overload of the applied current of the steering motor, or in a situation where a steering angle sensor or a steering torque sensor of the steering motor control device is incorrectly installed or malfunctions.

[0034] As another example, the condition determination unit 310 may determine that emergency steering is occurring if the target rack stroke is greater than a preset reference rack stroke. The condition determination unit 310 may obtain a target rack stroke requested by the driver from steering wheel sensor information including steering angle information or steering torque information. The target rack stroke may represent a rack stroke required for the steering rack to generate appropriate power steering force according to steering information. The target rack stroke may represent the output of the steering motor 210 required for the steering rack to move linearly by the target amount.In a case where a specific steering motor control device among the plurality of steering motor control devices fails and the steering motor 210 is controlled only with the remaining, normal steering motor control device, the condition determination unit 310 may set the limit rack stroke that can be implemented without overheating damage thereto as the reference rack stroke. The reference rack stroke may be a rack stroke corresponding to a specific rack force proportional to the rack force at positions where a rack is located at both ends of the steering rack stroke. For example, the condition determination unit 310 may set a rack stroke corresponding to a case where the rack moves linearly at 50% of the maximum output of the steering motor 210 as the reference rack stroke.The maximum output of the steering motor 210 may represent a rack force value at the end of the rack. However, 50% is merely an example, and embodiments of the disclosure are not limited thereto.

[0035] If it is determined that the steering ratio change condition is satisfied, the steering ratio change unit 320 may change the average steering ratio according to the preset virtual C-factor. As an example, if it is determined that the steering ratio change condition is satisfied, the steering ratio change unit 320 may change the average steering ratio according to the virtual C-factor set to a value less than 1. In this case, the average steering ratio may be a ratio of the steering angle to angular displacement calculated from rotation angle information via the steering motor when a steering wheel is arranged at both ends of a rotatable range of the steering wheel.Specifically, the average steering ratio may be the ratio of the steering angle of the steering wheel to the average value of the rotation angle of the steering motor when the steering wheel is rotated in the state of maximum rotation in one direction to the maximum in the opposite direction. For example, if the virtual C-factor is set to 1 / 2 when the average steering ratio is 1:8, the steering ratio changing unit 320 may change the average steering ratio to 1:4.

[0036] The control device 330 can control the steering motor output and adjust the rack stroke and rack speed based on the changed average steering ratio. For example, the control device 330 can control the steering motor output to be repeatedly generated at different values ​​at preset periods by applying the changed average steering ratio. For example, the control device 330 can control the rack stroke by repeatedly generating the steering motor output at 0% and 100% of the steering motor output by applying the changed average steering ratio. Accordingly, the control device 330 can provide the effect of enabling steering even at the end of the steering wheel.Furthermore, the control device 330 can control the rack speed, which is a moving speed of a rack moving between positions of the two ends of the rack stroke, by controlling the output of the steering motor by applying the changed average steering ratio. This can provide stable steered driving by more stable alignment of the idler wheel actuator (RWA).

[0037] Fig. 4 is a flowchart illustrating an operation of controlling by changing an average steering ratio of a steering control device of a vehicle according to an embodiment of the disclosure.

[0038] With reference to Fig. 4, an exemplary operation is described in which the steering control device 110 of the vehicle according to an embodiment of the disclosure changes the average steering ratio using the virtual C-factor and controls to reduce the rack speed based on the changed average steering ratio.

[0039] The condition determination unit 310 may determine whether a failure occurs in the implemented redundant system to include a plurality of steering motor control devices (S410). As an example, the condition determination unit 310 may determine that a failure occurs if a failure occurrence signal is detected due to a failure in the steering motor or the steering motor control devices. For example, the condition determination unit 310 may determine that a failure occurs upon detecting a failure occurrence signal generated by the steering motor control device connected to the steering motor if a failure occurs due to an overload of the current applied to the steering motor or due to a defect, for example, in the stator, rotator, or bearing of the steering motor.Now, when a failure occurs due to a defect in various sensors, a failure occurs due to a defect of the inverter, or a failure occurs due to a defect of the steering motor control device itself, a failure occurrence signal is generated from the corresponding steering motor control device, and based on this, the condition determination unit 310 can determine that a failure occurs.

[0040] The condition determination unit 310 may identify that the steering motor output is reduced by 50% if the failure occurrence signal is detected (S420). For example, if the steering control device 110 of the vehicle is a redundant system implemented to include a plurality of steering motor control devices, the steering control device 110 may perform restricted steering on the vehicle using a normal steering motor or a normal steering motor control device to prevent accidents. Accordingly, since only the normal steering motor or the normal steering motor control device is used, if a failure occurrence signal is detected, the condition determination unit 310 may identify that the steering motor output is reduced by 50%.

[0041] The condition determination unit 310 may determine whether emergency steering is occurring (S430). As one example, the condition determination unit 310 may determine whether emergency steering is occurring in conjunction with various sensors of the vehicle, such as the steering angle sensor, the yaw rate sensor, and the vehicle speed sensor. For example, if a preset steering angle speed is equal to or greater than a reference value according to the driver's steering wheel manipulation, the condition determination unit 310 may determine that emergency steering is occurring. As another example, the condition determination unit 310 may determine that emergency steering is occurring if the target rack stroke is greater than a preset reference rack stroke. The target rack stroke is a value calculated from the steering angle information or steering torque information, which changes depending on whether the driver is manipulating the steering wheel, and can be obtained from the steering wheel sensor information.The reference rack stroke can be set to a rack stroke corresponding to a specific rack force proportional to the rack force at positions where a rack is located at both ends of the steering rack stroke. For example, the reference rack stroke can be set to the rack stroke at the point corresponding to half the rack force at two opposite ends of the rack. Furthermore, the reference rack stroke is a value corresponding to the reference current for controlling the steering motor within a range where the steering motor control device is not damaged due to overheating, but is not limited to half the rack force.

[0042] The steering ratio changing unit 320 may apply a preset virtual C-factor (S440). For example, if it is determined that the steering ratio changing condition is met, the steering ratio changing unit 320 may set the virtual C-factor to a value less than 1. The steering ratio changing unit 320 may change the average steering ratio using the set virtual C-factor. Therefore, since the virtual C-factor is set and applied to a value less than 1, the gear ratio may be reduced.

[0043] The controller 330 may be controlled to repeatedly generate 0% and 100% of the steering motor output based on the changed average steering ratio (S450). For example, the controller 330 may control the rack stroke by repeatedly generating 0% and 100% of the steering motor output at preset periods by applying the changed average steering ratio. For example, when the steering ratio change condition is met, the controller 330 may apply and control a rectangular wave current having a preset cycle and a duty cycle according to the changed average steering ratio to the steering motor using the virtual C-factor to repeatedly generate 0% and 100% of the steering motor output. The period and duty cycle may be set to be different according to the target rack stroke.The values ​​of 0% and 100% set for the steering motor output are not limited to this, as long as the reference rack stroke or more can be provided.

[0044] The controller 330 may control to reduce the rack speed by controlling the steering motor output based on the changed average steering ratio (S460). For example, the controller 330 may control to repeatedly generate 0% and 100% of the steering motor output, thereby increasing the rack stroke to enable steering at two opposite ends. The controller 330 may reduce the gear ratio and the movement speed of the rack stroke, which correspond to the position of the rack, by applying the virtual C-factor set to a value less than 1.

[0045] Fig. 5 is a view illustrating a relationship between rack stroke and rack speed in a steering control device of a vehicle according to an embodiment of the disclosure.

[0046] With reference to Fig. 5, the rack stroke can be increased or decreased based on the origin P1, which is the center position of the rack, in the range of two opposite ends P4 and P'4 of the rack. As the rack stroke moves away from the origin P1 in one direction or the other, the rack can perform a linear rightward or leftward movement. In this case, the x-axis direction may correspond to the position of the rack. For example, +x may represent a state where the rack moves to the right, and -x may represent a state where the rack moves to the left. However, embodiments of the disclosure are not limited to this.

[0047] Furthermore, as the rack stroke increases, the rack force corresponding to the output of the steering motor 210 may increase non-linearly. For example, as the rack stroke increases, the rack force may also increase, and the overall graph shape may be a curve passing through P1 to P4. The graph shape may be symmetrical with respect to the y-axis such that P1 is symmetrical to P4 and P'1 is symmetrical to P'4.

[0048] In the steering control device 110 for a vehicle according to an embodiment of the disclosure, if the first steering motor control device 220 of the plurality of steering motor control devices fails, the steering motor 210 can be controlled only with the second steering motor control device 230. In this case, the second steering motor control device 230 can preset and store the rack stroke corresponding to the point P2, which is 50% of the rack force value at the ends P4 and P'4 of the rack, as the reference rack stroke. If the second steering motor control device 230 is limited to the range of the reference rack stroke set to prevent overheating damage, the driver may experience discomfort due to restricted steering and may fail to prevent unexpected accidents.In contrast, if the second steering motor control device 230 is not limited to the set reference rack stroke range, the internal temperature of the second steering motor control device 230 may suddenly rise, and the normal steering control device may be damaged due to overheating. Accordingly, the vehicle steering control device 110 according to an embodiment of the disclosure divides the output of the steering motor 210 into 0% and 100% and repeats them at different times, thereby controlling to increase the rack stroke by generating the output equal to or more than 50% of the rack force value at the end P4 or P'4. The vehicle steering control device 110 can accordingly control to increase the rack stroke beyond the reference rack stroke without overheating.

[0049] Fig. 6 is a flowchart illustrating an operation for adjusting the rack speed by changing an average steering ratio of a steering control device of a vehicle according to an embodiment of the disclosure.

[0050] With reference to Fig. 6, an exemplary operation is described in which the controller 330 controls the output of the steering motor according to the average steering ratio changed using the virtual C-factor to adjust the rack stroke and the rack speed. Fig. Figure 6 illustrates a rack force graph versus time when the virtual C-factor is not applied (610) and the rack force graph versus time when the virtual C-factor is applied (620). The rack force graph versus time can identify the rack speed.

[0051] For example, the steering ratio changing unit 320 may set the virtual C-factor to a value less than 1 based on vehicle speed information and change the average steering ratio. According to the invention, the steering ratio changing unit 320 changes the average steering ratio by decreasing the virtual C-factor as the vehicle speed increases. As a specific example, if the virtual C-factor is set to 1 / 2 when the average steering ratio is 1:8, the steering ratio changing unit 320 may change the average steering ratio to 1:4. If the vehicle speed increases, the steering ratio changing unit 320 may set the virtual C-factor to 1 / 4 and change the average steering ratio to 1:2.This is because, as the vehicle speed increases, the vehicle's movement increases with a small change in the steering angle, so stable steered driving can be achieved by setting a relatively smaller average steering ratio for the vehicle at higher speeds. However, the average steering ratio value and the virtual C-factor setting value are examples for describing the disclosure, and the disclosure is not limited thereto.

[0052] As another example, if the virtual C-factor set to a value less than 1 is applied, the controller 333 may control the rack speed to reduce according to the changed average steering ratio. As a specific example, if the controller 333 may control the rack stroke to move at 50 mm per second as much as the restricted length when the virtual C-factor is not applied (610), the controller 333 may identify that the rack stroke is moved at 25 mm per second as much as the restricted length when the virtual C-factor set to 1 / 2 is applied (620). However, the movement distance per second is an example and is not limited thereto. Accordingly, if the virtual C-factor is applied, the rack force graph may be as shown in Fig. 6 shown, can be changed over time.

[0053] Fig. 7 is a view illustrating an operation for adjusting the rack stroke by controlling the steering motor output of a steering control device of a vehicle according to an embodiment of the disclosure.

[0054] With reference to Fig. 7, an exemplary operation is described in which the controller 330 of the steering control device 110 of the vehicle according to an embodiment of the disclosure controls the output of the steering motor and adjusts the rack stroke and the rack speed based on the changed average steering ratio.

[0055] The controller 330 can change the average steering ratio using the virtual C-factor set to a value less than 1 and generate a larger rack stroke with the same steering motor output while changing the average steering ratio. The controller 330 can further reduce the rack speed by applying the changed average steering ratio. If the changed average steering ratio is applied, the controller 330 can accordingly generate a rack stroke at two opposite ends P4 and P4' of the rack with the same steering motor output.

[0056] Meanwhile, the control device 330 can control the steering motor output 710 to repeatedly generate different values ​​with a preset period T by applying a rectangular wave current having a preset period T, a duty ratio D, and an amplitude to the steering motor 210 under the changed average steering ratio. The current can be a current corresponding to the rack stroke. The different values ​​can be set to 0% and 100% of the steering motor output, but are not limited to this, as long as the reference rack stroke and more can be provided. Accordingly, the control device 330 can increase the rack stroke by controlling to repeatedly generate the steering motor output as 0% and 100% of the steering motor output, thereby providing steered driving even at two opposite ends of the rack.

[0057] Upon determining that the steering ratio change condition is satisfied, the controller 330 may adjust the steering ratio of the applied current to differ according to the detected initial internal temperature. For example, the duty ratio may be set to decrease as the initial internal temperature rises and increase as the initial internal temperature decreases. As a specific example, the controller 330 may increase the internal temperature while the steering motor output of 100% is applied and decrease the internal temperature while the steering motor output is 0%, that is, not applied. The internal temperature may repeat a rise and fall until the end P4 or P'4 of the steering rack is reached. Accordingly, the controller 330 can provide the effect of preventing damage due to overheating by adjusting the timing of the steering motor output application.

[0058] A vehicle steering method performed by the vehicle steering control device 110 described above in connection with the Fig. 1 to 7 can be carried out is described below.

[0059] Fig. 8 is a flowchart illustrating a vehicle steering control method according to an embodiment of the disclosure.

[0060] With reference to Fig.8, a steering control method of the disclosure may include a condition determination step that determines a steering ratio change condition (S810). As an example, the steering control device may determine the steering ratio change condition by determining whether a failure or emergency steering of the steering motor or the steering motor control device of the vehicle equipped with the steer-by-wire system occurs. The steering control device may determine that the steering ratio change condition is satisfied when a failure and emergency steering occur. For example, the steering control device may determine that a failure occurs if a failure occurrence signal is detected. The failure occurrence signal may be a flag indicating the failure generated by the steering motor control device.Specifically, the failure occurrence signal may be detected in a situation where overheating occurs due to an overload of the applied current of the steering motor, or in a situation where a steering angle sensor or a steering torque sensor of the steering motor control device is incorrectly installed or malfunctions.

[0061] As another example, the steering controller may determine that emergency steering is occurring if the target rack stroke is greater than a preset reference rack stroke. The steering controller may obtain a target rack stroke requested by the driver from wheel sensor information including steering angle information or steering torque information. The target rack stroke may represent a rack stroke for the steering rack required to generate appropriate power steering force according to steering information. The target rack stroke may represent the output of the steering motor 210 required for the steering rack to move linearly as much as the target. The target rack stroke may represent a rack stroke for the steering rack required to generate appropriate power steering force according to steering information.The target rack stroke may refer to the output of the steering motor required for the rack to move linearly as much as the target. The reference rack stroke may be a rack stroke corresponding to a specific rack force proportional to the rack force at two opposite ends of the rack. As a specific example, the steering control device may set the rack stroke when the rack is moving linearly at 50% of the steering motor output as the reference rack stroke. However, 50% is only an example, and embodiments of the disclosure are not limited thereto.

[0062] The steering control method may include a steering ratio changing step that changes the average steering ratio (S820). If it is determined that the steering ratio changing condition is met, the steering control device may change the average steering ratio according to the preset virtual C-factor. As an example, if it is determined that the steering ratio changing condition is met, the steering control device may change the average steering ratio according to the virtual C-factor set to a value less than 1. In this case, the average steering ratio may be a ratio of the steering angle to angular displacement calculated from rotation angle information via the steering motor when a steering wheel is arranged at both ends of a rotatable range of the steering wheel.Specifically, the average steering ratio may be the ratio of the steering angle of the steering wheel to the average value of the steering motor's rotation angle when the steering wheel is rotated in the state of maximum rotation in one direction to the maximum in the opposite direction. As a specific example, if the virtual C-factor is set to 1 / 2 when the average steering ratio is 1:8, the steering control device may change the steering ratio to 1:4.

[0063] The steering control method may include a control step that adjusts the rack stroke and the rack speed (S830). As an example, the steering control device may control the steering motor output and adjust the rack stroke and the rack speed based on the changed average steering ratio. The steering control device may control the steering motor output to repeatedly generate different values ​​by applying the changed average steering ratio. For example, the steering control device may control the rack stroke to increase by repeatedly generating the steering motor output at 0% and 100% of the steering motor output by applying the changed average steering ratio. Accordingly, the steering control device can provide the effect of enabling steering even at the end of the steering wheel.Furthermore, the steering control device can control the speed of the rack, which is the speed of movement of a rack moving between positions of the two ends of the rack stroke, by controlling the output of the steering motor by applying the changed average steering ratio. This can provide stable steered driving by allowing the idler wheel actuator (RWA) to be aligned more stably.

[0064] As set forth above, according to the disclosure, a steering control device and a steering control method can be provided. Specifically, a steering control device and a steering control method for a vehicle can be provided that can ensure stable driving by controlling the output of the steering motor by changing the center steering ratio when the driver initiates emergency steering and adjusting the rack stroke and rack speed in a failure situation.

[0065] The present description has been presented to enable a person skilled in the art to carry out and use the technical idea of ​​the disclosure, and has been provided in the context of a particular application and its requirements. Various changes, additions, and replacements to the described embodiments will be readily apparent to those skilled in the art, and the general concepts defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the disclosure. The above description and the accompanying drawings provide an example of the technical idea of ​​the disclosure for illustrative purposes only. The disclosed embodiments therefore aim to illustrate the scope of the technical idea of ​​the disclosure.The scope of the disclosure is therefore not limited to the embodiments shown, but is intended to be accorded the broadest scope consistent with the claims. The scope of the disclosure should be interpreted based on the following claims, and all technical ideas within the scope of equivalents thereof should be construed as included within the scope of the disclosure.

Claims

[1] Steering control device (110) of a vehicle, comprising: a condition determination unit (310) that determines (S810) a steering ratio change condition by determining whether a failure or emergency steering occurs in a steering motor (210) or a steering motor control device (220, 230) of the vehicle equipped with a steer-by-wire system; a steering ratio changing unit (320) that changes a middle steering ratio (S820) when the steering ratio changing condition is determined to be satisfied; and a control device (330) that controls (S830) a steering motor output and adjusts a rack stroke and a rack speed based on the changed average steering ratio; characterized bythat the average steering ratio is changed using a virtual C-factor, wherein the steering ratio changing unit (320) is arranged to change the average steering ratio by decreasing the virtual C-factor as the speed of the vehicle increases. [2] Steering control device (110) according to claim 1, characterized by in that the condition determination unit (310) determines that the failure occurs if a failure occurrence signal is detected, and determines that emergency steering occurs if a target rack stroke is greater than a preset reference rack stroke, and determines that the steering ratio change condition is satisfied when the failure and the emergency steering occur. [3] Steering control device (110) according to claim 2, characterized bythat the reference rack stroke is a rack stroke corresponding to a specific rack force set proportionally to a rack force at positions where a rack is located at both ends of the steering rack stroke. [4] Steering control device (110) according to claim 1, characterized by in that the steering ratio changing unit (320) changes the average steering ratio using the virtual C-factor set to a value less than 1 if it is determined that the steering ratio changing condition is satisfied, and wherein the average steering ratio is a ratio of a steering angle to an angular displacement calculated from rotation angle information about the steering motor (210) when a steering wheel (100) is arranged at both ends of a rotatable range of the steering wheel (100). [5] Steering control device (110) according to claim 1, characterized bythat the control device (330) controls to repeatedly generate the steering motor output with different values ​​in a preset period by applying the changed average steering ratio. [6] Steering control device (110) according to claim 5, characterized by that the different values ​​are set to 0% and 100% of the steering motor output, and the rack stroke is increased while the steering motor output is repeatedly generated. [7] Steering control device (110) according to claim 1, characterized by that the control device (330) controls so that the rack speed, which is a moving speed of a rack moving between positions of the two ends of the rack stroke, is reduced by applying the changed average steering ratio. [8] A vehicle steering control method comprising: a condition determination step (S810) that determines a steering ratio change condition by determining whether a failure or emergency steering occurs in a steering motor (210) or a steering motor control device (220, 230) of the vehicle equipped with a steer-by-wire system; a steering ratio changing step (S820) that changes an average steering ratio when the steering ratio changing condition is determined to be satisfied; and a control step (S830) that controls a steering motor output and adjusts a rack stroke and a rack speed based on the changed steering ratio, characterized by that the mean steering ratio is changed using a virtual C-factor, wherein the mean steering ratio is changed by decreasing the virtual C-factor as the speed of the vehicle increases. [9] Steering control method according to claim 8, characterized bythat the condition determination step (S810) determines that the failure occurs if a failure occurrence signal is detected, and determines that emergency steering occurs if a target rack stroke is greater than a preset reference rack stroke, and determines that the steering ratio change condition is satisfied when the failure and the emergency steering occur. [10] Steering control method according to claim 9, characterized by that the reference rack stroke is a rack stroke corresponding to a specific rack force set proportionally to a rack force at positions where a rack is located at both ends of the steering rack stroke. [11] Steering control method according to claim 8, characterized byin that the steering ratio changing step (S820) changes the average steering ratio using the virtual C-factor set to a value less than 1 if the steering ratio changing condition is determined to be satisfied, and wherein the average steering ratio is a ratio of a steering angle to an angular displacement calculated from rotation angle information about the steering motor (210) when a steering wheel (100) is arranged at both ends of a rotatable range of the steering wheel (100). [12] Steering control method according to claim 8, characterized by that the control step (S830) controls to repeatedly generate the steering motor output with different values ​​in a preset period by applying the changed average steering ratio. [13] Steering control method according to claim 12, characterized bythat the different values ​​are set to 0% and 100% of the steering motor output, and the rack stroke is increased while the steering motor output is repeatedly generated. [14] Steering control method according to claim 8, characterized by that the control step controls so that the rack speed, which is a moving speed of a rack moving between positions of the two ends of the rack stroke, is reduced by applying the changed mean steering ratio.

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