Motor control device and method for an electric power steering system

Abstract

A motor control device and method for an electric power steering system are disclosed. The motor control device for an EPS system in a vehicle includes: a temperature sensing unit configured to sense the temperature of a motor controller used to control the motor in the EPS system; and an output control module configured to adjust the motor current applied to the motor from the steering control module of the EPS system based on the motor current and the temperature of the motor controller sensed by the temperature sensing unit.

Description

Technical Field

[0001] Exemplary embodiments of this disclosure relate to a motor control device and method for an electric power steering (EPS) system for a vehicle, and more specifically, to a motor control device and method for an EPS system for a vehicle that can adjust the output of the motor based on the motor current used to control the motor and the temperature of the motor controller. Background Technology

[0002] An electric power steering (EPS) system for vehicles is a steering device that uses an electric motor to assist the steering force of the steering wheel. EPS systems use inputs such as vehicle speed, steering column torque, absolute torque, absolute steering angle, or vehicle status to control the torque of the motor that assists the steering force of the steering wheel via motor current.

[0003] Typically, the EPS system measures the motor current input to the motor. When the vehicle speed is high, the auxiliary steering torque of the EPS system is reduced by decreasing the motor current, and when the vehicle speed is low, the auxiliary steering torque is increased by increasing the motor current.

[0004] The motor in an EPS system actually functions as an actuator. EPS system motors are categorized into BLAC and DC types. In particular, DC motors (hereinafter referred to as "DC motors") are highly competitive in price, and their applications are expanding with the development of control technology.

[0005] However, DC motors employ protection logic to limit the motor's output in order to protect the DC motor from overheating, as overheating can occur due to the rotation of the DC motor along with the brushes that are always in contact with it.

[0006] The background technology of this disclosure is disclosed in Korean Patent Application No. 2001-0096718 (November 8, 2001), entitled "Control Circuit for DC Motor for Electric Power Steering". Summary of the Invention

[0007] Traditionally, the temperature, current, resistance, reactance, etc. of the motor controller are used to predict the motor temperature. The motor output is then limited based on the predicted motor temperature.

[0008] However, predicting motor temperature based on the motor controller's temperature, current, resistance, reactance, etc., presents a problem: with DC motors having relatively large heat capacity, the prediction accuracy is low. Consequently, the determination of whether a DC motor is overheating is inaccurate.

[0009] Various embodiments relate to providing a motor control device and method for an EPS system in a vehicle, which can protect the motor of the EPS system by adjusting the motor output based on the motor current used to control the motor and the temperature of the motor controller.

[0010] In one embodiment, a motor control device and method for an electric power steering (EPS) system of a vehicle, the device comprising: a temperature sensing unit configured to sense the temperature of a motor controller for controlling a motor in the EPS system; and an output control module configured to adjust the motor current applied to the motor from a steering control module of the EPS system based on the motor current and the temperature of the motor controller sensed by the temperature sensing unit.

[0011] In one embodiment, the output control module includes: a limit value detection unit configured to detect a motor current limit value based on the temperature of the motor controller and the motor current; an adjustment amount detection unit configured to detect an adjustment amount for limiting the motor current based on the temperature of the motor controller and the motor current; and an output adjustment unit configured to limit the motor current by adjusting the motor current limit value based on the adjustment amount detected by the adjustment amount detection unit.

[0012] In one implementation, the adjustment amount detection unit increases or decreases the adjustment amount based on the temperature of the motor controller.

[0013] In one embodiment, the adjustment amount detection unit increases the adjustment amount as the temperature of the motor controller increases, and decreases the adjustment amount as the temperature of the motor controller decreases.

[0014] In one implementation, the adjustment amount is divided into multiple regions based on the magnitude of the adjustment amount.

[0015] In one embodiment, the region includes: a first reduction region, in which the motor current limit value is reduced relatively significantly because the motor current limit value is greater than the motor current; a second reduction region, in which the motor current limit value is reduced relatively slightly compared to the first reduction region after the motor current limit value and the motor current are made the same; a holding region, in which the motor current limit value is maintained; and an increasing region, in which the motor current limit value is increased.

[0016] In one implementation, the limit detection unit sets the initial value of the motor current limit value to a value that is relatively larger than the motor current.

[0017] In one implementation, the limit detection unit sets an initial value for the motor current limit based on the operating duration during which the motor can operate at its rated current.

[0018] In one implementation, the output adjustment unit adjusts the motor current limit value every time a preset time has elapsed.

[0019] In one implementation, the temperature of the motor controller is the initial temperature of the motor controller that is sensed first after the EPS system begins operation.

[0020] In one embodiment, a motor control method for an electric power steering (EPS) system for a vehicle includes the steps of: sensing the temperature of the motor controller of the EPS system; and adjusting the motor current applied to the motor from the steering control module of the EPS system based on the motor current and the temperature of the motor controller sensed by the temperature sensing unit.

[0021] In one embodiment, the regulation of the motor current includes: detecting a motor current limit value based on the temperature of the motor controller and the motor current; detecting an adjustment amount for limiting the motor current based on the temperature of the motor controller and the motor current; and limiting the motor current by adjusting the motor current limit value based on the adjustment amount.

[0022] In one implementation, detecting the adjustment amount includes increasing or decreasing the adjustment amount based on the temperature of the motor controller.

[0023] In one embodiment, detecting the adjustment amount includes: increasing the adjustment amount as the temperature of the motor controller increases, and decreasing the adjustment amount as the temperature of the motor controller decreases.

[0024] In one implementation, the adjustment amount is divided into multiple regions based on the magnitude of the adjustment amount.

[0025] In one embodiment, the region includes: a first reduction region, in which the motor current limit value is reduced relatively significantly because the motor current limit value is greater than the motor current; a second reduction region, in which the motor current limit value is reduced relatively slightly compared to the first reduction region after the motor current limit value and the motor current are made the same; a holding region, in which the motor current limit value is maintained; and an increasing region, in which the motor current limit value is increased.

[0026] In one embodiment, detecting the motor current limit value includes setting the initial value of the motor current limit value to a value that is relatively larger than the motor current.

[0027] In one implementation, detecting the motor current limit includes setting an initial value for the motor current limit based on the operating duration during which the motor can operate at its rated current.

[0028] In one embodiment, detecting the motor current limit value includes: adjusting the motor current limit value by an output adjustment unit every time a preset set time has elapsed.

[0029] In one embodiment, the temperature of the motor controller is the initial temperature of the motor controller that is first sensed after the operation of the EPS system begins.

[0030] According to one aspect of this disclosure, a motor control device and method for an EPS system in a vehicle can protect the motor of the EPS system by adjusting the motor output based on the motor current used to control the motor and the temperature of the motor controller.

[0031] According to another aspect of this disclosure, a motor control device and method for an EPS system for a vehicle can limit the motor output with relatively low logical complexity compared to existing motor temperature prediction models. Attached Figure Description

[0032] Figure 1 This is a block diagram of a motor control device and method for an electric power steering (EPS) system for a vehicle according to embodiments of the present disclosure.

[0033] Figure 2 This is a block diagram of the output control module according to an embodiment of the present disclosure.

[0034] Figure 3 This is a diagram illustrating the rate of change of the command current and the temperature of the motor controller according to an embodiment of the present disclosure.

[0035] Figure 4 This is an illustration showing an example of limiting the output of a motor based on a motor current limit value according to an embodiment of the present disclosure.

[0036] Figure 5 This is a diagram illustrating the initial limit values ​​depending on the motor characteristics and the corresponding slope according to an embodiment of the present disclosure.

[0037] Figure 6 This is a diagram illustrating the variation of the motor current limit value depending on the command current and the temperature of the motor controller according to an embodiment of the present disclosure.

[0038] Figure 7 This is a flowchart of a motor control method for an EPS system according to an embodiment of the present disclosure. Detailed Implementation

[0039] As is customary in the relevant art, some exemplary embodiments may be illustrated in the accompanying drawings as functional blocks, units, and / or modules. Those skilled in the art will understand that these blocks, units, and / or modules are physically implemented by electronic (or optical) circuitry, such as logic circuits, discrete components, processors, hardwired circuits, memory elements, wiring connections, etc. When blocks, units, and / or modules are implemented by processors or similar hardware, they can be programmed and controlled using software (e.g., code) to perform the various functions discussed herein. Alternatively, each block, unit, and / or module may be implemented by dedicated hardware, or as a combination of dedicated hardware performing some functions and processors performing other functions (e.g., one or more programmed processors and associated circuitry). Without departing from the scope of the inventive concept, each block, unit, and / or module of some exemplary embodiments may be physically separated into two or more interacting and discrete blocks, units, and / or modules. Furthermore, without departing from the scope of the inventive concept, blocks, units, and / or modules of some exemplary embodiments may be physically combined into more complex blocks, units, and / or modules.

[0040] In the following description, the motor control apparatus and method for an electric power steering (EPS) system will be described with reference to the accompanying drawings through various exemplary embodiments. For clarity and convenience, the thickness of lines or the dimensions of elements in the drawings may be exaggerated. Furthermore, the terms to be described below are defined by consideration of their function in this disclosure and may vary depending on the intent or practice of the user or operator. Therefore, these terms should be defined based on the entire contents of this specification.

[0041] Figure 1 This is a block diagram of a motor control device and method for an EPS system in a vehicle according to embodiments of the present disclosure. Figure 2 This is a block diagram of the output control module according to an embodiment of the present disclosure. Figure 3 This is a diagram illustrating the rate of change of the command current and the temperature of the motor controller according to an embodiment of the present disclosure. Figure 4 This is an illustration showing an example of limiting the output of a motor based on a motor current limit value according to an embodiment of the present disclosure. Figure 5 This is a diagram illustrating the initial limit values ​​depending on the motor characteristics and the corresponding slope according to an embodiment of the present disclosure. Figure 6 This is a diagram illustrating the variation of the motor current limit value depending on the command current and the temperature of the motor controller according to an embodiment of the present disclosure.

[0042] refer to Figure 1 According to embodiments of the present disclosure, the motor control device for an EPS system for a vehicle includes a steering control module 10, an output control module 20, a temperature sensing unit 30, and a motor 40.

[0043] The steering control module 10 assists the steering force of the steering wheel by controlling the motor 40 of the EPS system. The EPS system can be electric power steering (EPS). However, this disclosure is not limited to EPS, and electric motor-driven power steering (MDPS) can also be used.

[0044] The steering control module 10 receives vehicle speed, steering column torque, steering angle, driving information, etc., generates motor current based on vehicle speed, steering column torque, steering angle, driving information, etc., and generates auxiliary steering torque by inputting the motor current to the motor 40.

[0045] The steering control module 10 reduces the auxiliary steering torque by decreasing the motor current when the vehicle speed is relatively high, and increases the auxiliary steering torque by increasing the motor current when the vehicle speed is relatively low.

[0046] The motor 40 is mounted in the steering shaft and generates auxiliary steering torque based on the motor current received from the steering control module 10. In this embodiment, the motor 40 may be a DC motor, but this disclosure is not limited to this embodiment.

[0047] Temperature sensing unit 30 senses the temperature of the motor controller (not shown) used to control motor 40 in the EPS system. The motor controller generates motor current in response to a control signal received from steering control module 10 and inputs the motor current to motor 40.

[0048] The motor controller can be installed separately from the controller of the steering control module 10, but it can also be integrated with the controller of the steering control module 10 as a module. If the motor controller is installed separately from the controller of the steering control module 10, the temperature sensing unit 30 can directly sense the temperature of the motor controller. If the motor controller is installed inside the controller of the steering control module 10, the temperature of the controller of the steering control module 10 can be replaced by the temperature of the motor controller.

[0049] The output control module 20 adjusts the motor current based on the motor current applied to the motor 40 by the steering control module 10 of the EPS system and the temperature of the motor controller sensed by the temperature sensing unit 30.

[0050] That is, if the driver performs a steering wheel operation (e.g., rotates the steering wheel to both ends), the output control module 20 adjusts the motor current limit value based on the temperature of the motor controller and the motor current, and limits the motor current based on the motor current limit value, thereby reducing the heat generated when driving the motor 40. Therefore, it prevents the motor 40 from being damaged by the heat that may be generated by driving the motor 40, or prevents the motor 40 from malfunctioning.

[0051] refer to Figure 2 The output control module 20 includes a limit value detection unit 21, an adjustment amount detection unit 22, and an output adjustment unit 23.

[0052] The limit value detection unit 21 detects the motor current limit value based on the temperature of the motor controller and the motor current.

[0053] The motor current limit is a set current quantity that restricts the motor current. Therefore, when the motor current limit is increased or decreased based on an adjustment amount, the motor current can also be adjusted within the motor current limit. This adjustment amount will be described later.

[0054] The temperature of the motor controller is the first temperature sensed after the EPS system is started when the vehicle is turned on.

[0055] The temperature of the motor controller can vary at different points in the vehicle's operation. The temperature of the motor controller may be affected by the time interval between the vehicle's shutdown and startup. When the vehicle starts after a relatively long period since it stopped, the temperature of the motor controller can be relatively low. If the vehicle turns quickly after a period of time since it was previously shut down, the temperature of the motor controller can be relatively high.

[0056] When detecting the motor current limit value, the limit value detection unit 21 sets the initial value of the motor current limit value to be relatively larger than the motor current.

[0057] The initial value of the motor current limit is the maximum value of the motor current limit, and it is set based on the operating duration for which the motor 40 can operate at its rated current. Because the motor 40 needs to be able to operate at its rated current for a given time, the initial value of the motor current limit needs to be relatively higher than the rated current value. That is, the motor current limit has an initial value as its maximum value, and then decreases based on the adjustment amount, thereby limiting the motor current.

[0058] The regulation detection unit 22 detects the regulation amount used to limit the motor current based on the temperature of the motor controller and the motor current.

[0059] The adjustment amount detection unit 22 sets the adjustment amount based on the temperature of the motor controller (i.e., the temperature of the motor controller sensed first after the operation of the EPS system begins).

[0060] When the initial value of the motor current limit is determined as described above, an adjustment amount is applied to each segment of a preset set time. As a result, the motor current limit is adjusted. This adjustment amount can be increased or decreased based on the temperature of the motor controller and the motor current. For example, the adjustment amount can increase as the temperature of the motor controller increases and decrease as the temperature of the motor controller decreases.

[0061] like Figure 3 As shown, the adjustment amount can be divided into multiple regions according to its size, for example, four regions.

[0062] The adjustment amount can be divided into a first decreasing region, a second decreasing region, a maintaining region, and an increasing region.

[0063] First Decreasing Region This is the region where, because the motor current limit is higher than the motor current and the adjustment amount is relatively the largest, the motor current limit is reduced relatively significantly. This is the first reduction region. This is a region where, because the motor current is relatively very high, a relatively large current limit is required. (Reference) Figure 3 The first reduced region This refers to the region where the motor current is 77A or less, down to 70A, and the adjustment amount is -0.51A / s. That is, when the motor current is 77A or less, down to 70A, for each set time, such as 1 second, an adjustment amount of -0.51A / s is applied to the motor current limit, causing the motor current limit to decrease at intervals of -0.51A / s.

[0064] Second reduction region This is a region in which, after making the motor current limit and the motor current the same, the motor current limit decreases relatively slightly compared to the first reduction region, and the adjustment amount is relatively small compared to the first reduction region. (Reference) Figure 3 The second reduced region This refers to the region where the motor current is 70A or less, down to 17A, and the adjustment amount is -0.45A / s. That is, when the motor current decreases to 70A or less, down to 17A, for each set time interval, an adjustment amount of -0.45A / s is applied to the motor current limit, causing the motor current limit to decrease at intervals of -0.45A / s. This limits the motor current within the motor current limit. Therefore, although the motor current is relatively greater than the motor current limit, it is still kept within the motor current limit.

[0065] Maintain area This is a region where the motor current limit is maintained, and although current is used, the adjustment amount can be 0 because the temperature change of the motor 40 is very small. (Reference) Figure 3 Maintain the area This refers to the region where the motor current is 17A or less, down to 11A, and the adjustment is 0. That is, when the motor current limit decreases to 17A or less, down to 11A, the motor current limit is maintained. (Maintaining this region) The motor current in the motor is relatively less than the motor current limit.

[0066] Add area This is the area where the motor current limit is increased. Although the motor current is used, because the motor temperature of 40°C can be maintained at room temperature, it is necessary to restore the adjustment value. (Reference) Figure 3 Increase the area This refers to the region where the motor current is 11A or less up to 0A and the adjustment is +0.069A / s. In the increasing region... In this process, for each set time interval, the motor current limit is increased at intervals of 0.069 A / s to restore the adjustment range. (Increase area) The motor current in the motor is relatively less than the motor current limit.

[0067] Based on the temperature of the motor controller and the motor current, the initial value and adjustment amount of the motor current limit can be set differently.

[0068] In particular, the magnitude of the adjustment can increase as the temperature of the motor controller increases and decrease as the temperature of the motor controller decreases, as examples are shown in Table 1 below.

[0069] Table 1

[0070] 77A -0.51A / s -2.858A / s -3.573A / s 70A -0.45A / s -2.568A / s -3.21A / s 17A 0A / s 0A / s 0A / s 11A 0A / s 0A / s 0A / s 0A +0.069A / s +0.069A / s +0.069A / s

[0071] As can be seen from Table 1, the adjustment amount is relatively large when the temperature of the motor controller increases.

[0072] The output adjustment unit 23 adjusts the motor current limit value based on the adjustment amount detected by the adjustment amount detection unit 22.

[0073] That is, when the adjustment amount detection unit 22 detects the adjustment amount, the output adjustment unit 23 adjusts the motor current limit value in stages every time a set time has elapsed, and limits the motor current within the adjusted motor current limit value.

[0074] refer to Figure 4 When the initial value of the motor current limit is 79.4A and the motor current is 70A, for each set time interval of 1 second, the output adjustment unit 23 reduces the motor current limit at an interval of -0.51A / s. Although the motor current limit is reduced, the motor current is still relatively less than the motor current limit. Therefore, the motor current output by the steering control module 10 remains unchanged at 70A.

[0075] When the motor current limit decreases and the motor current becomes 70A or less, down to 17A, the output regulating unit 23 reduces the motor current limit at intervals of -0.45A / s after a set time, and limits the motor current within the reduced motor current limit.

[0076] When the motor current limit decreases and the motor current becomes 17A or less, down to less than 11A, the output regulating unit 23 continues to maintain the motor current limit because the adjustment amount is 0A / s. At this time, the motor current is within the range of the motor current limit.

[0077] When the motor current limit decreases and the motor current becomes 11A or even less (down to 0A), the output regulating unit 23 increases the motor current limit at intervals of +0.069A / s after a set time. This restores the motor current limit. At this point, the motor current is within the range of the motor current limit.

[0078] In this embodiment, the initial value of the motor current limit is the maximum value of the motor current limit, and it needs to be relatively higher than the rated current value, because the motor 40 needs to generate the rated current for a given time.

[0079] refer to Figure 5 When motor 40 can continuously input a rated current of 70A for 21 seconds, the initial value and adjustment amount of the motor current limit can be set so that the motor current can be limited to 70A or less within 21 seconds. For example, when the initial value of the motor current limit is 79.4A and the adjustment amount is -0.51A / s, the motor current limit can be adjusted to 70A within 21 seconds.

[0080] from Figure 6 As can be seen, if the driver operates the steering wheel all the way to both ends, the motor current is limited to the motor current limit value by limiting the motor current limit value as described above.

[0081] See below for reference Figure 7 A motor control method for an EPS system according to embodiments of the present disclosure is described in detail.

[0082] Figure 7 This is a flowchart of a motor control method for an EPS system according to an embodiment of the present disclosure.

[0083] refer to Figure 7 When the steering control module 10 operates and starts the operation of the motor controller (S10), the temperature sensing unit 30 senses the temperature of the motor controller (S20).

[0084] When the temperature of the motor controller is sensed, the limit detection unit 21 detects the motor current limit based on the motor current received from the steering control module 10 and the temperature of the motor controller (S30).

[0085] In addition, the regulation detection unit 22 detects the regulation amount used to limit the motor current based on the temperature of the motor controller and the motor current (S40).

[0086] When the motor current limit value is detected by the limit value detection unit 21 and the adjustment amount is detected by the adjustment amount detection unit 22, the output adjustment unit 23 adjusts the motor current limit value in stages (S50 and S60) every time a set time has elapsed, and limits the motor current within the adjusted motor current limit value (S70).

[0087] For example, when the initial value of the motor current limit is 79.4A and the motor current is 70A, for each set time interval of 1 second, the output regulating unit 23 reduces the motor current limit at intervals of -0.51A / s, and limits the motor current within the reduced motor current limit. In this case, although the motor current limit decreases, the output motor current of 70A remains unchanged because the motor current is relatively less than the motor current limit.

[0088] Subsequently, when the motor current limit decreases and the motor current becomes 70A or less, down to 17A, the output regulating unit 23 reduces the motor current limit at intervals of -0.45A / s after a set time, and limits the motor current within the reduced motor current limit.

[0089] Furthermore, when the motor current limit decreases and the motor current becomes 17A or even less than 711A, the output regulating unit 23 continues to maintain the motor current limit because the adjustment amount is 0A / s. Subsequently, when the motor current becomes 11A or even less than 0A, the output regulating unit 23 increases the motor current limit at intervals of +0.069A / s after a set time, causing the motor current to gradually recover.

[0090] As described above, the motor control device and method for an EPS system for a vehicle according to embodiments of the present disclosure protects the motor from overheating by adjusting the motor output based on the motor current used to control the motor in the EPS system and the temperature of the motor controller.

[0091] Furthermore, the motor control device and method for an EPS system for a vehicle according to embodiments of this disclosure can limit the motor output with relatively low logical complexity compared to existing motor temperature prediction models.

[0092] The implementations described in this specification can be implemented as, for example, methods or procedures, devices, software programs, data streams, or signals. While this disclosure is discussed only in the context of a single form of implementation (e.g., discussed only as a method), implementations having the discussed features can also be implemented in another form (e.g., a device or program). The device can be implemented as suitable hardware, software, or firmware. The method can be implemented in a device, such as a processor commonly referred to as a processing device, including computers, microprocessors, integrated circuits, or programmable logic devices. The processor includes communication devices, such as computers, mobile phones, mobile phones / personal digital assistants (PDAs), and other devices that facilitate information communication between end users.

[0093] While exemplary embodiments of this disclosure have been disclosed for illustrative purposes, those skilled in the art will understand that various modifications, additions, and substitutions are possible without departing from the scope and spirit of this disclosure as defined in the appended claims. Therefore, the true technical scope of this disclosure should be defined by the appended claims.

Claims

1. A motor control device for an electric power steering system of a vehicle, the device comprising: A temperature sensing unit is configured to sense the temperature of a motor controller used to control the motor in the electric power steering system; as well as The output control module is configured to adjust the motor current applied to the motor from the steering control module of the electric power steering system based on the motor current and the temperature of the motor controller sensed by the temperature sensing unit. The output control module includes: The limit value detection unit is configured to detect the motor current limit value based on the temperature of the motor controller and the motor current. The regulation detection unit is configured to detect the regulation amount used to limit the motor current based on the temperature of the motor controller and the motor current; and The output regulation unit is configured to limit the motor current by adjusting the motor current limit value based on the regulation amount detected by the regulation amount detection unit. The temperature of the motor controller is the initial temperature of the motor controller that is sensed first after the operation of the electric power steering system begins.

2. The apparatus of claim 1, wherein, The adjustment amount detection unit increases or decreases the adjustment amount based on the temperature of the motor controller.

3. The apparatus of claim 2, wherein, The adjustment amount detection unit The adjustment amount increases as the temperature of the motor controller rises, and The adjustment amount decreases as the temperature of the motor controller decreases.

4. The apparatus of claim 1, wherein, The adjustment amount is divided into multiple regions based on its magnitude.

5. The apparatus of claim 4, wherein, The region includes: In the first reduction region, because the motor current limit value is greater than the motor current, the motor current limit value is reduced relatively significantly. The second reduction region, in which the motor current limit value and the motor current are made the same as each other, reduces the motor current limit value relatively slightly compared to the first reduction region; A holding region is established in which the motor current limit value is maintained; and An additional region is added, and the motor current limit value is increased in the added region.

6. The apparatus of claim 1, wherein, The limit value detection unit sets the initial value of the motor current limit value to a value that is relatively larger than the motor current.

7. The device according to claim 6, wherein, The limit value detection unit sets the initial value of the motor current limit value based on the operating duration during which the motor can operate at its rated current.

8. The device according to claim 1, wherein, Each time a preset time has elapsed, the output adjustment unit adjusts the motor current limit value.

9. A motor control method for an electric power steering system in a vehicle, the method comprising the following steps: Sensing the temperature of the motor controller of the electric power steering system; as well as The motor current applied to the motor from the steering control module of the electric power steering system is adjusted based on the motor current and the temperature of the motor controller sensed by the temperature sensing unit. The adjustment of the motor current includes: detecting a motor current limit value based on the temperature of the motor controller and the motor current; detecting an adjustment amount for limiting the motor current based on the temperature of the motor controller and the motor current; and limiting the motor current by adjusting the motor current limit value based on the adjustment amount. The temperature of the motor controller is the initial temperature of the motor controller that is sensed first after the operation of the electric power steering system begins.

10. The method according to claim 9, wherein, Detecting the adjustment amount includes increasing or decreasing the adjustment amount based on the temperature of the motor controller.

11. The method according to claim 10, wherein, Detecting the adjustment amount includes: The adjustment amount increases as the temperature of the motor controller increases, and The adjustment amount decreases as the temperature of the motor controller decreases.

12. The method according to claim 9, wherein, The adjustment amount is divided into multiple regions based on its magnitude.

13. The method of claim 12, wherein the region comprises: In the first reduction region, because the motor current limit value is greater than the motor current, the motor current limit value is reduced relatively significantly. The second reduction region, in which the motor current limit value and the motor current are made the same as each other, reduces the motor current limit value relatively slightly compared to the first reduction region; A holding region is established in which the motor current limit value is maintained; and An additional region is added, and the motor current limit value is increased in the added region.

14. The method according to claim 9, wherein, Detecting the motor current limit value includes setting the initial value of the motor current limit value to a value that is relatively larger than the motor current.

15. The method according to claim 14, wherein, Detecting the motor current limit value includes setting an initial value for the motor current limit value based on the operating duration during which the motor can operate at its rated current.

16. The method according to claim 9, wherein, The detection of the motor current limit value includes: adjusting the motor current limit value every time a preset time has elapsed.

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