Steering control device and steering control method

Abstract

The present disclosure relates to a steering control device and a steering control method. The steering control device according to the present disclosure includes a receiver that receives a motor torque from a motor torque sensor provided in a host vehicle, and a controller that enables a steering gear to be driven in a compliance region, calculates a friction of the steering gear based on the motor torque received by the driving of the steering gear, determines a state of the steering gear based on the calculated friction, and outputs a notification message about the state of the steering gear to a driver.

Description

TECHNICAL FIELD

[0001] The present embodiment relates to a steering control apparatus and a steering control method. BACKGROUND

[0002] An electric power steering apparatus detects a steering torque generated by rotation of a steering wheel, and controls a motor to supply a steering assist power proportional to the detected steering torque, thereby performing steering control on a vehicle.

[0003] Specifically, in an electric power steering, a steering torque generated by rotation of a steering wheel is transmitted to a rack via a rack and pinion mechanism, and a steering assist power generated by a motor according to the steering torque is also transmitted to the rack. In other words, the steering assist power generated by the motor is added to the steering torque generated by the steering wheel, axially moves the rack, thereby steering the vehicle.

[0004] Such an electric power steering can experience a reduction in friction between several members constituting the mechanism of the apparatus, for example, a rack and pinion mechanism or a reducer, due to, for example, wear of the members or a weakened fastening force that can occur as the mileage of the vehicle increases. As another example, the rack and pinion mechanism or the reducer can rust, which increases the friction between several members of the mechanism.

[0005] An increase or a reduction in the friction between the internal members of the electric power steering can cause the driver to feel uncomfortable steering. SUMMARY

[0006] In one aspect, the present disclosure provides a steering control apparatus including a receiver that receives a motor torque from a motor torque sensor provided in a host vehicle, and a controller that enables a steering gear to be driven in a compliance zone, calculates a friction of the steering gear based on the motor torque received by the driving of the steering gear, determines a state of the steering gear based on the calculated friction, and outputs a notification message about the state of the steering gear to a driver.

[0007] In another aspect, the present disclosure provides a steering control method including an information receiving step that receives a motor torque from a motor torque sensor provided in a host vehicle, a friction calculating step that enables a steering gear to be driven in a compliance zone, and calculates a friction of the steering gear based on the motor torque received by the driving of the steering gear, and a state determining step that determines a state of the steering gear based on the calculated friction.

[0008] According to the present disclosure, a steering control apparatus and method can calculate and quantify only a friction of a steering gear, determine a state of the steering gear according to the calculated friction. BRIEF DESCRIPTION OF DRAWINGS

[0009] The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:

[0010] Figure 1 is a block diagram illustrating a steering control device according to an embodiment of the present disclosure;

[0011] Figure 2 is a view schematically illustrating a steering control system according to an embodiment;

[0012] Figure 3 and Figure 4 is a view illustrating an example of calculating friction using a compliant zone according to an embodiment;

[0013] Figure 5 is a flowchart illustrating a steering control method according to an embodiment of the present disclosure;

[0014] Figure 6 is a flowchart illustrating step S520 in more detail according to an embodiment; and

[0015] Figure 7 is a view illustrating step S530 in more detail according to an embodiment. DETAILED DESCRIPTION

[0016] In the following description of examples or embodiments of the present disclosure, reference will be made to the accompanying drawings in which specific examples or embodiments that can be implemented are shown by way of illustration, and in which identical or similar components are denoted by identical reference numerals and symbols even when they are shown in different drawings. Further, in the following description of examples or embodiments of the present disclosure, detailed descriptions of well-known functions and components incorporated herein will be omitted when it is determined that such description can make the subject matter of some embodiments of the present disclosure unclear. The terms used herein, such as “include,” “have,” “contain,” “constitute,” “consist of,” and “consist in,” are generally intended to allow the addition of other components, unless the term is used with the term “only.” As used herein, the singular form is intended to include the plural form, unless the context clearly indicates otherwise.

[0017] Terms such as “first,” “second,” “A,” “B,” “(A)” or “(B)” can be used herein to describe elements of the present disclosure. Each of these terms is not used to define the nature, order, sequence, or number of elements, but is merely used to distinguish the corresponding element from other elements.

[0018] When it is mentioned that a first element is "connected or coupled to", "contacts or overlaps" a second element, etc., it should be interpreted that not only the first element can be "directly connected or coupled to" or "directly contact or overlap" 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 to" each other, "contact or overlap" each other, etc. via a fourth element. Here, the second element can be included in at least one of two or more elements that are "connected or coupled", "contact or overlap" each other, etc.

[0019] When a time-related term such as "after", "subsequent to", "later", "before", etc. is used to describe the process or operation of an element or configuration, or the flow or step in an operation, process, manufacturing method, etc., these terms can be used to describe non-continuous or non-sequential processes or operations, unless the term "directly" or "immediately" is used together.

[0020] In addition, when any dimension, relative dimension, etc. is mentioned, it should be considered that the numerical value or the corresponding information of the element or feature (e.g., level, range, etc.) includes a tolerance or error range that can be caused by various factors (e.g., process factors, internal or external impact, noise, etc.), even if the relevant description is not specified. In addition, the term "may" fully covers all meanings of the term "can".

[0021] Hereinafter, a steering control apparatus according to an embodiment of the disclosure will be described with reference to the accompanying drawings.

[0022] Figure 1 is a block diagram illustrating a steering control apparatus 10 according to an embodiment of the disclosure.

[0023] Referring to Figure 1 The steering control apparatus 10 according to an embodiment of the disclosure can include a receiver 110 and a controller 120.

[0024] According to an embodiment of the disclosure, the steering control apparatus 10 can be an advanced driver assistance system (ADAS) equipped in a host vehicle to provide information that helps to drive the host vehicle or assist a driver in the host vehicle.

[0025] Here, the ADAS can refer to various types of advanced driver assistance systems. For example, the driver assistance system can include, for example, autonomous emergency braking, an intelligent parking assistance system (SPAS), a blind spot detection (BSD), an adaptive cruise control (ACC), a lane departure warning system (LDWS), a lane keeping assistance system (LKAS), and a lane change assistance system (LCAS). However, the disclosure is not limited thereto.

[0026] Here, the host vehicle can refer to a vehicle equipped with a prime mover and driven by power of the prime mover. Also, the host vehicle can be an electric vehicle, which is a power-driven vehicle that obtains driving energy by rotating a motor using electric power from a battery, rather than obtaining driving energy from combustion of fossil fuel.

[0027] The steering control device 10 is applicable to a case where the host vehicle is a passenger car as well as a case where the host vehicle is an autonomous vehicle that is unmanned.

[0028] The receiver 110 can receive a motor torque from a motor torque sensor provided in the host vehicle.

[0029] The above-described motor torque sensor can be installed to the host vehicle. In one embodiment, the motor torque sensor can be included in the steering control system 1.

[0030] Hereinafter, an embodiment of the steering control system 1 in which a function of the steering control device 10 can be performed is described.

[0031] Figure 2 is a view schematically showing the steering control system 1 according to the embodiment.

[0032] Referring to Figure 2 The steering control system 1 according to the embodiment can refer to a system in which steering of a host vehicle equipped with the steering control system 1 is controlled according to a rotation angle of a steering wheel 211 manipulated by a driver.

[0033] The steering control system 1 can include a hydraulic power steering (HPS) that generates hydraulic pressure by rotating a pump to provide a steering assist force and an electric power steering (EPS) that drives a motor according to a driving type to provide a steering assist force. The following description mainly focuses on the electronic steering control system 1, but the present disclosure is not limited thereto.

[0034] Depending on whether the steering input actuator 210 and the steering output actuator 220 are coupled through a mechanical connection member (or a link), the steering control system 1 can be a mechanical steering control system 1 that steers a wheel 223 by transmitting a force (torque) generated by a driver who steers the steering wheel 211 to the steering motor 221 via a mechanical power transmission device (e.g., a link) to steer the wheel 223 by driving of the steering motor 221, or a steer-by-wire (SbW) system that transmits power by transmitting / receiving an electric signal via, for example, an electric cable rather than a mechanical power transmission device. The following description describes an example in which the steering control system 1 is an SbW system, but the present disclosure is not limited thereto.

[0035] As Figure 2As illustrated, the steering control system 1 according to the present disclosure can include a steering input actuator 210, a steering control device 10, and a steering output actuator 220. As described above, if the steering control system 1 is an SbW system, the steering input actuator 210 and the steering output actuator 220 can be mechanically separated from each other.

[0036] The steering input actuator 210 can refer to a device that inputs steering information desired by a driver. As described above, the steering input actuator 210 can include a steering wheel 211, a steering shaft 212, and a reaction force motor 213. Although not illustrated, the steering angle information can further include a steering gear for transmitting a rotational force of the reaction force motor 213 to the steering shaft 212.

[0037] The reaction force motor 213 can receive a control signal (or referred to as an "instruction current") from the steering control device 10 and apply a reaction force to the steering wheel 211. Specifically, the reaction force motor 213 can receive an instruction current from the steering control device 10 and be driven at a rotational speed indicated by the instruction current, generating a reaction force torque. The generated reaction torque can be transmitted to the steering wheel through the steering gear.

[0038] The steering control device 10 can receive steering information from the steering input actuator 210, calculate a control value, and output an electrical signal indicating the control value to the steering output actuator 220. The steering information can refer to information including at least one of a steering angle and a torque.

[0039] The steering control device 10 can receive power information actually output from the steering output actuator 220 as feedback, calculate a control value, and output an electrical signal to the steering output actuator 220 based on the control value, thereby providing a steering feel to the driver.

[0040] The steering output actuator 220 can refer to a device that actually drives the steering of the host vehicle. The steering output actuator 220 can include, for example, a steering motor 221, a rack 222, and a wheel 223.

[0041] The steering input actuator 210 and the steering output actuator 220 can further include a motor torque sensor capable of detecting a motor torque of each of the reaction force motor 213 and the steering motor 221.

[0042] The steering motor 221 can axially move the rack 222. Specifically, the steering motor 221 can be driven by receiving an instruction current from the steering control device 10 and linearly move the rack 222 in an axial direction. The wheel 223 can be steered left or right by the linear motion of the rack 222.

[0043] Although not shown, the steering control system 1 according to the present disclosure can further include a clutch for decoupling or coupling the steering input actuator 210 and the steering output actuator 220, for example. The clutch can be operated by the control of the steering control device 10.

[0044] If the steering control system 1 according to the present disclosure is an SbW system, and the host vehicle travels in an autonomous driving mode, the steering control system 1 according to the present disclosure can control only the steering output actuator 220 to perform steering control on the host vehicle, or can control both the steering input actuator 210 and the steering output actuator 220 to perform steering control on the host vehicle.

[0045] Referring back to Figure 1 , the controller 120 can enable the steering gear to be driven in a compliance zone, calculate the friction of the steering gear based on the motor torque received by the driving of the steering gear, determine the state of the steering gear based on the calculated friction, and output a notification message about the state of the steering gear to the driver.

[0046] The controller 120 can estimate the rack force based on the information sensed about the motor torque of the receiver 110. The estimated rack force can refer to the sum of the friction of the steering gear, the suspension friction of the host vehicle, and the friction of the tire. Thus, the environment for determining the state of the steering gear needs to calculate only the friction of the steering gear.

[0047] Figure 3 And Figure 4 are views showing examples of calculating the friction using the compliance zone according to an embodiment.

[0048] Referring to Figure 3 And Figure 4 , the friction of the steering gear can be calculated by enabling the steering gear to be driven in a compliance zone. The compliance zone can be set in a motor position range in which the rack does not move even when the steering gear is driven. Specifically, the steering gear can be driven by a steering motor controlled by a command signal from the steering control device 10, and the rack can thus move. However, there can be a small interval in which the rack does not move although the steering gear is driven by the steering motor, and such a small interval can be defined as the compliance zone.

[0049] Referring to Figure 3 , the compliance zone can be set in a motor position range. The motor position can refer to the angle of clockwise or counterclockwise rotation of the motor. Thus, the compliance zone can be set based on a preset rotation angle of the motor.

[0050] The motor position range in which the rack does not move although the steering gear is driven by the steering motor can vary according to the mechanical specifications of the steering gear. Thus, the compliance zone can be set differently according to the mechanical specifications of the steering gear.

[0051] Referring to Figure 4 , the controller 120 can receive a motor torque generated by the steering motor by driving the steering gear from the motor torque sensor, thereby calculating a rotational force estimate. The calculated rotational force estimate can be generated in a graph as shown in Figure 4

[0052] In Figure 4 , A and B can be a maximum value and a minimum value of the rotational force estimate, respectively, but are not limited thereto. For example, in an interval in which the motor position is constant, the rotational force estimate can vary, in which case A and B can each be an average value of the varying rotational force estimate.

[0053] The controller 120 can calculate the friction of the steering gear based on A and B. For example, the friction of the steering gear can be an average value obtained by dividing A and B by 2.

[0054] Accordingly, the rotational force estimate can be calculated based on the torque generated by the steering motor when the steering gear is driven in the compliant zone such that the rack does not move, and the friction of the steering gear can be calculated based on the rotational force estimate. If the steering gear is driven in the compliant zone, the actual position of the rack does not change such that only the internal parts of the steering gear are operated without affecting the suspension friction and the tire friction. Accordingly, an environment in which the friction of the steering gear can be calculated separately can be formed.

[0055] The compliant zone is not limited to the position of the rack. In other words, regardless of where the rack is located, if the position of the rack is at a midpoint between forces, the friction of the steering gear when the steering gear is driven in the compliant zone can be calculated based on the rack located at the midpoint between the forces. In other words, although the rack is not positioned at the center, the steering gear is driven in the compliant zone in which the position of the rack does not change from the midpoint between the forces, so that the friction of the steering gear can be calculated.

[0056] The controller 120 can control the steering gear to be driven in the compliant zone before the host vehicle is steered by the driver, calculate the friction of the steering gear, and determine the state of the steering gear based on the calculated friction of the steering gear. For example, the controller 120 can control the steering gear to be driven in the compliant zone before the host vehicle starts and performs steering, thereby determining the state of the steering gear. As another example, the controller 120 can control the steering gear to be driven in the compliant zone before the host vehicle, which is traveling and has stopped to make its speed zero, performs steering again, thereby determining the state of the steering gear.

[0057] As described above, the controller 120 can determine the state of the steering gear based on the calculated friction of the steering gear. Various embodiments of the state of the steering gear determined according to the calculated friction of the steering gear are described below.

[0058] ​For example, if the calculated friction is a preset first reference value or greater, the controller 120 can determine that the steering gear has been damaged. The preset first reference value can refer to a maximum value at which the steering gear can be driven without damage. In this case, the controller 120 can output a notification message about damage to the steering gear to the driver.

[0059] As another example, the receiver 110 can also receive a temperature from a temperature sensor provided in the host vehicle. The received temperature can be an internal temperature of the host vehicle, but is not limited thereto. For example, the temperature can be a temperature of an external environment in which the host vehicle travels.

[0060] If the calculated friction is a preset first reference value or greater, and the received temperature is a preset temperature or less, the controller 120 can determine that the state of the steering device is an increase in friction due to low temperature. In other words, the grease applied to the bearing of the steering gear, for example, can undergo a change in physical properties due to low temperature, as a result of which the friction of the steering gear increases. In this case, the controller 120 can output a notification message indicating that the friction of the steering gear has increased due to low temperature to the driver. The controller 120 can perform additional control to increase the output of the steering motor so as to compensate for the increased friction of the steering gear due to low temperature.

[0061] As described above, if the calculated friction is a preset first reference value or greater, and a temperature is preset as a factor for determining the state of the steering gear, the controller 120 can distinguish and determine an increase in the friction of the steering gear due to damage to the steering gear or low temperature based on the temperature received from the temperature sensor, and output a notification message about the determination result to the driver.

[0062] As another example, if the calculated friction is a preset second reference value or less, the controller 120 can determine that the steering gear has been worn. The preset second reference value can refer to a maximum value at which a part needs to be replaced due to wear of the steering gear. In this case, the controller 120 can output a notification message indicating that a part needs to be replaced due to wear of the steering gear to the driver.

[0063] As another example, if the calculated friction is less than the preset first reference value and greater than the preset second reference value, the controller 120 can determine that the steering gear is in a normal state. In other words, a range between the preset first reference value and the second reference value can refer to a range of values of friction at which the steering gear can be normally driven. In this case, the controller 120 can output a notification message indicating that the steering gear is normal, but the output of the notification message can be omitted in the normal state.

[0064] Further, although the deflector is in the normal driving range based on the calculated friction, the controller 120 can determine that the deflector is rusted based on the calculated friction. For example, as long as the deflector is driven in the compliance zone, the controller 120 can calculate the friction of the deflector and store the calculated friction. The controller 120 can compare the stored frictions, and if the result of the comparison shows that the friction gradually increases, determine that the deflector is rusted. In other words, as the rust and the state deteriorate, the friction of the deflector can gradually increase. The controller 120 can determine that the deflector has rusted by storing and comparing the calculated friction. In this case, the controller 120 can output a notification message indicating that maintenance is required due to rust on the deflector to the driver.

[0065] As described above, the steering control apparatus 10 according to the present disclosure can calculate the friction of the deflector and determine the state of the deflector according to the calculated value.

[0066] The steering control apparatus 10 can be implemented as, for example, an electronic control unit (ECU).

[0067] According to the embodiment, a computer system (not shown) such as the steering control apparatus 10 can be implemented as an electronic control unit (ECU). The ECU can include one or more processors, a memory, a storage unit, at least one or more of a user interface input unit or a user interface output unit, which can communicate with each other via a bus. The computer system can further include a network interface for accessing a network. The processor can be a central processing unit (CPU) or a semiconductor device that executes processing instructions stored in the memory and / or the storage unit. The memory and the storage unit can include various types of volatile / non-volatile storage media. For example, the memory can include read-only memory (ROM) and random access memory (RAM).

[0068] Described below is a steering control method using the steering control apparatus 10 capable of executing the above-described embodiments of the present disclosure.

[0069] Figure 5 is a flowchart illustrating a steering control method according to an embodiment of the present disclosure.

[0070] Referring to Figure 5 , the steering control method according to the present disclosure can include an information receiving step S510 for receiving a motor torque from a motor torque sensor provided in a host vehicle, a friction calculating step S520 for enabling a deflector to be driven in a compliance zone and calculating a friction of the deflector based on the motor torque received by driving the deflector, and a state determining step S530 for determining a state of the deflector based on the calculated friction.

[0071] Although not shown, the steering control method can further include an output step (not shown) for outputting a notification message of the state of the steering gear determined in the state determination step S530 to the driver.

[0072] Figure 6 is a flowchart illustrating step S520 according to an embodiment in more detail.

[0073] Referring to Figure 6 , the steering control method can determine whether the rack of the host vehicle is located at a midpoint between the forces. The midpoint between the forces can represent a balance of the forces. Thus, if the rack is located at the midpoint between the forces, the rack can be in a state in which no external force acts thereon.

[0074] The steering control method can control the steering gear to be driven in a compliance zone (S620). The compliance zone can be set in a range of motor positions in which the rack does not move even when the steering gear is driven. In general, the rotational force estimate can refer to a sum of the friction of the steering gear, the suspension friction of the host vehicle, and the tire friction. If the steering gear is driven in the compliance zone, the rack does not move, so that the friction of the steering gear can be calculated separately based on the rotational force estimate.

[0075] The control of driving the steering gear in the compliance zone can be performed before the driver performs steering of the host vehicle. For example, the steering gear to be driven can be controlled in the compliance zone before the host vehicle starts and performs steering, or before the host vehicle that has once traveled and stopped to have its speed of zero performs steering again.

[0076] The steering control method can calculate the friction of the steering gear (S630). For example, the steering control method can calculate the rotational force estimate by receiving, from the motor torque sensor, the motor torque generated by the driving of the steering gear by the steering motor when the steering gear is driven in the compliance zone, and calculate the friction of the steering gear based on the calculated rotational force estimate.

[0077] Figure 7 is a view illustrating step S530 according to an embodiment in more detail.

[0078] Referring to Figure 7 , the steering control method can determine whether the calculated friction is a preset first reference value or greater (S710). If the calculated friction is the preset first reference value or greater (YES in S710), the information receiving step can further receive a temperature from a temperature sensor provided in the host vehicle, and the state determination step can determine whether the temperature received from the temperature sensor is a preset temperature or lower (S720). If the temperature received from the temperature sensor is the preset temperature or lower (YES in S720), the steering control method can determine that the state of the steering gear is an increase in friction due to low temperature (S730). In this case, although the rack is not moved in the compliance zone, the rack can be moved in the non-compliance zone.Figure 7 Although not shown in the

[0079] If the temperature received from the temperature sensor is greater than the preset temperature, the steering control method can determine that the steering gear has been damaged (S740). In this case, although not shown in the Figure 7 Although not shown in the

[0080] If the calculated friction is less than the preset first reference value (NO in S710), the steering control method can determine whether the calculated friction is a preset second reference value or less (S750).

[0081] If the calculated friction is the preset second reference value or less (YES in S750), the steering control method can determine that the steering gear is worn (S760). In this case, although not shown in the Figure 7 Although not shown in the

[0082] If the calculated friction is greater than the preset second reference value (NO in S750), the steering control method can determine that the steering gear is in a normal state (S770). In this case, although not shown in the Figure 7 Although not shown in the

[0083] Further, although not shown in the Figure 7 Although not shown in the

[0084] As described above, according to the present disclosure, the steering control apparatus and method can calculate and quantify only the friction of the steering gear, and determine the state of the steering gear according to the calculated friction.

[0085] The above description is given to enable those skilled in the art to carry out and use the technical idea of the disclosure, and is provided in the context of a specific application and its requirements. Various modifications, additions and substitutions to the described implementations will be apparent to those skilled in the art and can be made without departing from the spirit and scope of the disclosure, and the general principles defined herein can be applied to other implementations and applications. The above description and drawings are provided only for illustrative purposes of the technical idea of the disclosure. That is, the disclosed implementations are intended to illustrate the scope of the technical idea of the disclosure. Therefore, the scope of the disclosure is not limited to the illustrated implementations, but is consistent with the broadest scope of the claims. The scope of protection of the disclosure should be interpreted based on the appended claims, and all technical ideas within the scope of equivalents thereof should be interpreted as included in the scope of the disclosure.

[0086] Cross Reference to Related Applications

[0087] This application claims priority to Korean Patent Application No. 10-2021-0069350, filed on May 28, 2021, which is incorporated herein by reference for all purposes as if fully set forth herein.

Claims

1. A steering control device, comprising: a receiver that receives motor torque from a motor torque sensor provided in the host vehicle, the motor being a reaction force motor; as well as a controller that enables a steering gear to be driven in a compliance zone, calculates friction of the steering gear based on motor torque received through driving of the steering gear, determines a state of the steering gear based on the calculated friction, and outputs a notification message regarding the state of the steering gear to a driver, the steering gear transmitting the rotational force of the reaction force motor to a steering shaft, wherein the receiver further receives a temperature from a temperature sensor disposed in the host vehicle, wherein, if the calculated friction is a preset first reference value or greater and the temperature is a preset temperature or less, the controller determines that the state of the steering gear is increased friction due to low temperature, and performs additional control to increase the output of the motor to compensate for the increased friction of the steering gear due to low temperature, wherein, if the calculated friction is the preset first reference value or greater and the temperature exceeds the preset temperature, the controller determines that the steering gear is damaged, The compliance zone is defined as a motor position range in which the rack does not move despite the steering gear being driven, and the wheel is steered left or right by the linear movement of the rack.

2. The steering control device according to claim 1, wherein: If the calculated friction is a preset second reference value or less, the controller determines that the steering gear is worn.

3. The steering control device according to claim 1, wherein: The controller controls the steering device to be driven in the compliance zone before the host vehicle is steered by the driver.

4. The steering control device according to claim 1, wherein: If the calculated friction is less than a preset first reference value and greater than a preset second reference value, the controller determines that the steering gear is in a normal state.

5. The steering control device according to claim 4, wherein: The controller stores the calculated frictions, and if a comparison result between the stored frictions shows that the frictions are gradually increasing, the controller determines that the steering gear is rusted.

6. A steering control method, comprising: an information receiving step of receiving a motor torque from a motor torque sensor provided in the host vehicle, the motor being a reaction force motor; a friction calculating step of enabling a steering gear to be driven in a compliance zone and calculating friction of the steering gear based on motor torque received through driving of the steering gear, the steering gear transmitting the rotational force of the reaction force motor to a steering shaft; as well as a state determining step of determining a state of the steering gear based on the calculated friction, wherein the information receiving step further receives a temperature from a temperature sensor provided in the host vehicle, wherein, if the calculated friction is a preset first reference value or greater and the temperature is a preset temperature or less, the state determining step determines that the state of the steering gear is increased friction due to low temperature, and performs additional control to increase the output of the motor to compensate for the increased friction of the steering gear due to low temperature, wherein the state determining step determines that the steering gear is damaged if the calculated friction is the preset first reference value or greater and the temperature exceeds the preset temperature, The compliance zone is defined as a motor position range in which the rack does not move despite the steering gear being driven, and the wheel is steered left or right by the linear movement of the rack.

7. The steering control method according to claim 6, wherein: If the calculated friction is a preset second reference value or less, the state determination step determines that the steering gear is worn.

8. The steering control method according to claim 6, wherein: The state determining step controls the steering device to be driven in the compliance zone before the host vehicle is steered by the driver.

9. The steering control method according to claim 6, wherein: If the calculated friction is less than a preset first reference value and greater than a preset second reference value, the state determination step determines that the steering gear is in a normal state.

10. The steering control method according to claim 9, wherein: The state determination step stores the calculated frictions, and if a comparison result between the stored frictions shows that the frictions are gradually increasing, the state determination step determines that the steering gear is rusted.

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