阅读说明：本技术 用于控制电机驱动动力转向系统的装置和方法 (Apparatus and method for controlling motor-driven power steering system ) 是由 金泰弘 于 2020-10-16 设计创作，主要内容包括：用于控制MDPS系统的装置可以包括MDPS基本逻辑单元,基于施加到车辆的转向柱的柱扭矩和车速,来测定在手动驾驶模式下用于驱动MDPS电机的第一辅助指令电流；自动驾驶转向控制器,测定在自动驾驶模式下用于驱动MDPS电机的第二辅助指令电流,和以及模式改变控制器,基于在自动驾驶模式下的柱扭矩,使用可变地测定的可变参考时间来测定驾驶员的转向干预,基于柱扭矩测定从自动驾驶模式到手动驾驶模式的模式改变时间,并且通过向第一辅助指令电流和第二辅助指令电流施加合并了模式改变时间的权重,来测定用于模式改变时驱动MDPS电机的最终辅助指令电流。(The apparatus for controlling the MDPS system may include an MDPS basic logic unit determining a first assist command current for driving the MDPS motor in a manual driving mode based on a column torque applied to a steering column of the vehicle and a vehicle speed; an automatic driving steering controller measuring a second assist command current for driving the MDPS motor in an automatic driving mode, and a mode change controller measuring a steering intervention of a driver using a variably measured variable reference time based on a column torque in the automatic driving mode, measuring a mode change time from the automatic driving mode to a manual driving mode based on the column torque, and measuring a final assist command current for driving the MDPS motor at the time of the mode change by applying a weight incorporating the mode change time to the first assist command current and the second assist command current.)

1. An apparatus for controlling a Motor Driven Power Steering (MDPS) system, comprising:

an MDPS basic logic unit configured to determine a first assist command current for driving the MDPS motor in a driver's manual driving mode based on a column torque applied to a steering column of the vehicle and a vehicle speed of the vehicle;

an automatic driving steering controller configured to determine a second assist command current for driving the MDPS motor in an automatic driving mode of the vehicle; and

a mode change controller configured to determine steering intervention of a driver using a variably determined variable reference time according to a column torque in an automatic driving mode of a vehicle, determine a mode change time from the automatic driving mode to the manual driving mode based on the column torque, and determine a final assist command current for driving the MDPS motor when changing from the automatic driving mode to the manual driving mode by applying a weight incorporating the mode change time to the first and second assist command currents.

2. The apparatus according to claim 1, wherein the mode change controller determines that the driver has performed a steering intervention if a state in which a column torque is maintained at a preset reference torque or more for a variable reference time or more is maintained; and measuring the variable reference time to a smaller value as the column torque becomes larger.

3. The apparatus according to claim 2, wherein the mode change controller determines the mode change time based on a measured column torque that is a column torque at which the driver has performed a steering intervention, and determines the mode change time as a smaller value in at least a partial region of the measured column torque when the measured column torque becomes larger.

4. The apparatus according to claim 1, wherein the mode change controller determines the final auxiliary command current by applying the weight supplement to each of the first and second auxiliary command currents; and the mode change controller determines the final assist command current such that the final assist command current approaches from the second assist command current to the first assist command current as the value of the weight changes from a lower value to a higher value.

5. The apparatus of claim 4, wherein:

when the weight is changed within a range between above a preset lower limit and below a preset upper limit by taking the mode change time as a factor,

the mode change controller completes the change from the automatic driving mode to the manual driving mode within the mode change time.

6. The apparatus of claim 1, wherein the mode change controller

Filtering the column torque in a frequency band, the column torque being measured based on a steering angle acceleration of a steering wheel of the vehicle, and the column torque being measured to include a resonance frequency caused based on a mechanical mechanism of the MDPS system mounted on the vehicle, and

determining the steering intervention of the driver from the filtered column torque.

7. The apparatus according to claim 1, wherein the automatic driving steering controller determines the second assist command current through Proportional Integral Derivative (PID) control based on a command steering angle determined according to the running environment of the vehicle in such a manner that MDPS motor position control is performed, and

the second assist command current is measured using a variable high-pass filter (HPF) having a cutoff frequency that is variably measured based on an angular velocity of the command steering angle, and a differential (D) control gain that is calculated based on a position control gain and a differential parameter of the PID control.

8. The apparatus according to claim 1, characterized in that the mode change controller executes a limiting process of limiting the determination of the driver's steering intervention based on the column torque and the variable reference time, based on an angular acceleration of the command steering angle determined according to the vehicle running environment.

9. The apparatus according to claim 8, wherein the mode change controller performs the limiting process using a method of increasing the variable reference time as the angular acceleration of the command steering angle becomes larger, or stops performing the limiting process using a method of determining the driver steering intervention based on the column torque and the variable reference time when the angular acceleration of the command steering angle is a preset reference value or more.

10. A method for controlling a Motor Driven Power Steering (MDPS) system, comprising:

determining, by a mode change controller, whether steering intervention by a driver has occurred based on a variable reference time variably determined according to a column torque applied to a steering column of the vehicle in an autonomous driving mode of the vehicle;

determining, by the mode change controller, a mode change time from the autonomous driving mode to a manual driving mode of the driver based on a column torque if it is determined that steering intervention of the driver has occurred; and is

Determining, by the mode change controller, a final assist command current for driving the MDPS motor when changing from the automatic driving mode to the manual driving mode by applying a weight incorporating the mode change time to a first assist command current and a second assist command current, which are currents for driving the MDPS motor in the manual driving mode and the automatic driving mode, respectively.

11. The method according to claim 10, wherein in the determining whether or not steering intervention of the driver occurs, if the column torque is maintained in a state of a preset reference torque or more for the variable reference time or more, the mode change controller determines that the driver has performed steering intervention, and determines the variable reference time to be a smaller value as the column torque becomes larger.

12. The method according to claim 11, characterized in that during the determination of the mode change time, the mode change controller determines the mode change time based on a measured column torque that is a column torque at which the driver has performed a steering intervention is determined, and when the measured column torque becomes large, the mode change time is determined to be a smaller value in at least a partial region of the measured column torque.

13. The method according to claim 10, wherein during said determining the mode change time, the mode change controller determines the final auxiliary command current by applying the weight supplement to each of the first auxiliary command current and second auxiliary command current; and the mode change controller determines the final assist command current such that the final assist command current approaches from the second assist command current to the first assist command current as the value of the weight changes from a lower value to a higher value.

14. The method of claim 13, wherein:

the mode change controller completes the change from the automatic driving mode to the manual driving mode within the mode change time when the weight changes within a range between above a preset lower limit and below a preset upper limit, taking the mode change time as a factor.

15. The method according to claim 10, characterized in that the mode change controller filters the column torque in a frequency band, the column torque being determined based on a steering angle acceleration of a steering wheel of the vehicle, and the column torque being determined to include a resonance frequency caused based on a mechanical mechanism of the MDPS system mounted on the vehicle, when the determination is made as to whether the steering intervention of the driver occurs, and the mode change controller determines the steering intervention of the driver from the filtered column torque.

16. The method of claim 10, wherein:

the second assist command current is measured by Proportional Integral Derivative (PID) control based on a command steering angle measured according to the running environment of the vehicle in such a manner that MDPS motor position control is performed, and

the second assist command current is determined by taking into account a variable high-pass filter (HPF) having a cutoff frequency variably determined based on an angular velocity of the command steering angle, and a differential (D) control gain calculated based on a position control gain and a differential parameter of the PID control.

17. The method according to claim 10, characterized in that, in the determination of whether the driver's steering intervention is occurring, the mode change controller executes a limiting process of limiting the determination of the driver's steering intervention based on the column torque and the variable reference time, based on an angular acceleration of the command steering angle determined according to the vehicle running environment.

18. The method according to claim 17, characterized in that, in the determination of whether the driver's steering intervention is occurring, the mode change controller performs the limiting process using a method of increasing the variable reference time as the angular acceleration of the command steering angle becomes larger, or stops performing the limiting process based on the method of determining the driver's steering intervention based on the column torque and the variable reference time when the angular acceleration of the command steering angle is a preset reference value or larger.

Technical Field

Exemplary embodiments of the present disclosure relate to an apparatus and method for controlling a Motor Driven Power Steering (MDPS) system, and more particularly, to an apparatus and method for controlling an MDPS system, in which an MDPS motor is controlled in consideration of an automatic driving mode and a manual driving mode of a vehicle.

Background

Power steering of a vehicle is an electric power-based steering device whose function is to assist the driver in steering the steering wheel. For such power steering, a method using hydraulic pressure is mainly used. Recently, however, a motor driven power steering system (MDPS) system, i.e., a method of using power of a motor, is increasingly used. The reason for this is that the MDPS system has advantages of light weight, small occupied space, and no need for oil change, compared to the existing hydraulic power steering system.

The MDPS system determines a running condition of a vehicle through a torque sensor for measuring a steering torque of a driver input to a steering wheel, a steering angle sensor for measuring a steering angle or a steering angular velocity of the steering wheel, and a vehicle speed sensor for measuring a vehicle speed, and provides an assist torque through a motor based on the steering torque applied to a steering shaft when the driver turns the steering wheel.

The autonomous vehicle controls the operation of the MDPS system applied thereto by recognizing a road environment in which the vehicle travels through an autonomous driving module (e.g., a camera sensor, a radar sensor, and a lidar sensor) in an autonomous driving mode, and determines a command steering angle and a command torque required for the operation of the MDPS system.

In this case, for example, in the case where a failure occurs suddenly in the automatic driving module or a manual steering is required for emergency avoidance driving, there may occur a case where the driver has to hold and manipulate the steering wheel at his or her own will. In this case, if the steering torque is maintained above the given level for a given time, the conventional MDPS system will determine that steering intervention by the driver has occurred, and operate to release the autonomous driving mode. However, the conventional method of determining the driver's steering intervention has limitations because it is impossible to quickly release the automatic driving mode and quickly enter the manual driving mode in the case of sudden steering because it must be maintained unconditionally for a given time regardless of the steering torque applied by the driver.

Further, if the position control of the MDPS based on the automatic driving module is continuously performed even if the driver forcibly manipulates the steering wheel, a significant accident may be caused because the vehicle is not controlled as intended by the driver. Therefore, in the conventional art, a method of determining the steering intention of the driver based on the magnitude of the column torque or the change in the phase difference between the steering angle sensor and the motor angle sensor is considered. In this case, however, the driver may feel a steering feeling of difference because the control current of the motor is largely changed due to the driver's abrupt steering during the position control of the MDPS in the automatic driving mode. That is, when the mode is changed from the automatic driving mode to the manual driving mode, the immediate control stability is lowered due to the output difference in each mode control case. This may cause a feeling of difference such as abnormal behavior of the vehicle or steering vibration.

Background art of the present disclosure is disclosed in korean patent application laid-open No.10-2017-0065793 (6/14/2017).

Disclosure of Invention

Various embodiments are directed to providing an apparatus and method for controlling a motor-driven power steering system, which can solve the problem of immediate control stability degradation of an MDPS due to an output difference in each mode control case, as well as the problem of occurrence of a sense of difference such as abnormal behavior of a vehicle or steering vibration, by improving the problem that a given time must be unconditionally taken when a mode is changed from an automatic driving mode to a manual driving mode in a conventional MDPS system, enabling the automatic driving mode to be rapidly released and the manual driving mode to be rapidly entered at the time of sudden steering.

In one embodiment, an apparatus for controlling a Motor Driven Power Steering (MDPS) system, comprises: an MDPS basic logic unit configured to determine a first assist command current for driving the MDPS motor in a driver's manual driving mode based on a column torque applied to a steering column of the vehicle and a vehicle speed of the vehicle; an automatic driving steering controller configured to determine a second assist command current for driving the MDPS motor in an automatic driving mode of the vehicle; and a mode change controller configured to determine steering intervention of a driver using a variably determined variable reference time according to a column torque in an automatic driving mode of the vehicle, determine a mode change time from the automatic driving mode to a manual driving mode based on the column torque, and determine a final assist command current for driving the MDPS motor when changing from the automatic driving mode to the manual driving mode by applying a weight incorporating the mode change time to the first and second assist command currents.

In one embodiment, the mode change controller may determine that the driver has performed a steering intervention if the column torque is maintained at the preset reference torque or more for the variable reference time or more; and the variable reference time is measured to a smaller value as the column torque becomes larger.

In one embodiment, the mode change controller may determine the mode change time from a measured column torque that is a column torque at which the steering intervention by the driver is measured, and determine the mode change time as a smaller value in at least a partial region of the measured column torque when the measured column torque becomes larger.

In one embodiment, the mode change controller may determine the final supplementary command current by applying (complementary applying) a weight supplement to each of the first and second supplementary command currents; and the mode change controller determines the final assist command current such that the final assist command current approaches from the second assist command current to the first assist command current as the value of the weight changes from a lower value to a higher value.

In one embodiment, the mode change controller may complete the change from the automatic driving mode to the manual driving mode within the mode change time when the weight is changed within a range between above a preset lower limit and below a preset upper limit by taking the mode change time as a factor.

In one embodiment, the mode change controller filters a column torque in a frequency band, the column torque being determined based on a steering angular acceleration of a steering wheel of the vehicle and the column torque being determined to include a resonance frequency caused based on a mechanical mechanism of an MDPS system mounted on the vehicle, and the mode change controller determines the steering intervention of the driver from the filtered column torque.

In one embodiment, the automatic steering controller determines a second assist command current by Proportional Integral Derivative (PID) control based on a command steering angle determined according to a running environment of the vehicle in a manner of performing MDPS motor position control, and determines the second assist command current using a variable high-pass filter (HPF) having a cutoff frequency variably determined based on an angular velocity of the command steering angle, and a derivative (D) control gain calculated based on a position control gain and a derivative parameter of the PID control.

In one embodiment, the mode change controller executes a limiting process of limiting the determination of the driver's steering intervention based on a column torque and a variable reference time, based on an angular acceleration of a command steering angle determined according to a running environment of the vehicle.

In one embodiment, the mode change controller may perform the limiting process using a method of increasing the variable reference time as the angular acceleration of the command steering angle becomes larger, or stop performing the limiting process using a method of determining the driver's steering intervention based on the column torque and the variable reference time when the angular acceleration of the command steering angle is a preset reference value or more.

In one embodiment, a method for controlling a Motor Driven Power Steering (MDPS) system, comprising: determining, by the mode change controller, whether steering intervention of the driver has occurred based on a variable reference time variably determined according to a column torque applied to the vehicle in an autonomous driving mode of the vehicle; determining, by the mode change controller, a mode change time from the autonomous driving mode to a manual driving mode of the driver based on the column torque if it is determined that steering intervention of the driver has occurred; and the mode change controller determines a final assist command current for driving the MDPS motor when changing from the automatic driving mode to the manual driving mode by applying a weight incorporating a mode change time to a first assist command current and a second assist command current, which are currents for driving the MDPS motor in the manual driving mode and the automatic driving mode, respectively.

Drawings

Fig. 1 is a block diagram for describing an apparatus for controlling a Motor Driven Power Steering (MDPS) system according to an embodiment of the present disclosure.

Fig. 2 is a block diagram for describing detailed elements of an apparatus for controlling an MDPS system according to an embodiment of the present disclosure.

Fig. 3 is a flowchart for describing a method of controlling an MDPS system according to an embodiment of the present disclosure.

Detailed Description

Hereinafter, embodiments of an apparatus and method for controlling a motor driven power steering system (MDPS) system will be described with reference to the accompanying drawings. In describing the present specification, the thickness of a line or the size of an element shown in the drawings may have been exaggerated for clarity and convenience of description. Terms described below are defined by considering their functions in the present disclosure, and may be different according to the intention or practice of a user or operator. Therefore, these terms should be interpreted based on the entire contents of the present specification.

Fig. 1 is a block diagram for describing an apparatus for controlling an MDPS system according to an embodiment of the present disclosure. Fig. 2 is a block diagram for describing detailed elements of an apparatus for controlling an MDPS system according to an embodiment of the present disclosure.

Referring to fig. 1, the apparatus for controlling the MDPS system according to the embodiment of the present disclosure may include a column torque sensor 100, a vehicle speed sensor 200, an MDPS basic logic unit 300, an automatic driving steering controller 400, and a mode change controller 500.

The column torque sensor 100 may detect a column torque (T) applied to a steering column of the vehicle and transmit the column torque (T) to the MDPS basic logic unit 300 and the mode change controller 500, which will be described later. The column torque (T) applied to the steering column may include not only the column torque applied by the driver but also noise column torque occurring in a situation not desired by the driver, for example, column torque in a resonance frequency region caused based on a mechanical mechanism of an MDPS system mounted on the vehicle. The noise column torque may be filtered (or removed) by a filter unit described later.

The vehicle speed sensor 200 may detect a vehicle speed (V) of the vehicle. The vehicle speed sensor 200 may include various sensors such as a sensor for detecting a vehicle speed using a rotational speed of a wheel, a sensor for detecting a vehicle speed by measuring Revolutions Per Minute (RPM), and a sensor for detecting a vehicle speed using a Global Positioning System (GPS).

The MDPS basic logic unit 300 may determine a first assist command current (I) for driving the MDPS motor in a driver's manual driving mode (or manual steering mode) based on the column torque (T) and the vehicle speed (V) detected by the column torque sensor 100 and the vehicle speed sensor 200, respectively_{ref_A}). The MDPS basic logic unit 300 may determine a first assist command current (I) for driving the MDPS motor in the manual driving mode_{ref_A}) So that the boost curve (boost curve) is applied to the column torque (T) and the vehicle speed (V). To this end, the MDPS basic logic unit 300 may include an MDPS logic unit for calculating an assist command current value based on a column torque (T) and a vehicle speed (V) using a boost curve, and a motor controller for generating a first assist command current (I) based on the calculated assist command current value_{ref_A}) And controls the MDPS motor.

The autopilot steering controller 400 may determine a second assist command current (I) for driving the MDPS motor in the autopilot mode_{ref_B}). The automatic driving steering controller 400 may control the vehicle speed detected by the vehicle speed sensor 200 according to the running environment of the vehicle detected by sensors (e.g., a radar sensor, a camera sensor, and a laser radar sensor) mounted on the vehicle(V) and the current steering angle (theta) of the vehicle from a steering angle sensor (not shown)_v) Based on a command steering angle (theta) measured by the automatic driving system 600 of the vehicle_ref) Determining a second auxiliary command current (I) for driving the MDPS motor in the automatic driving mode_{ref_B}). The autopilot steering controller 400 may control the steering angle by steering angle based on the command (theta)_ref) The second auxiliary command current (I) is determined in such a way that the position control of the MDPS motor is carried out by Proportional Integral Derivative (PID) control_{ref_B}). To this end, the autopilot steering controller 400 may include a position controller and a speed controller for controlling the position and speed of the MDPS motor together in the autopilot mode.

The mode change controller 500 may determine steering intervention of the driver based on a variable reference time variably determined according to a column torque in an automatic driving mode of the vehicle, may determine a mode change time from the automatic driving mode to a manual driving mode based on the column torque (T), and may control the steering intervention of the driver by commanding a current (I) to the first and second assistance_{ref_A}And I_{ref_B}) Applying a weight incorporating a mode change time, and determining a final assist command current (I) for driving the MDPS motor when changing from the automatic driving mode to the manual driving mode_{ref_final})。

Hereinafter, the operation of the mode change controller 500 is specifically described based on a configuration for determining steering intervention of the driver and a configuration for determining a final assist command current and changing the automatic driving mode to the manual driving mode.

1. Determining driver steering intervention

As described above, if the state in which the column torque (T) is above the given value is maintained for a certain time, the conventional MDPS system will determine that steering intervention by the driver has occurred and operate to release the autonomous driving mode. Therefore, the conventional MDPS system has a limitation in that a given time must be maintained unconditionally regardless of the magnitude of the column torque applied by the driver (i.e., regardless of the degree of urgency of manual manipulation). As a result, the driver feels a sense of looseness or discrepancy since no manual operation is performed for a given time, and it is impossible to promptly release the automatic driving mode and promptly enter the manual driving mode at the time of sudden steering.

As means for solving these problems, in the present embodiment, a configuration is adopted that measures steering intervention of the driver based on a variable reference time that is variably measured in accordance with the column torque (T) in an autonomous driving mode of the vehicle.

Specifically, if the column torque (T) remains in a state of a preset reference torque or more for a variable reference time or more, the mode change controller 500 may determine that steering intervention by the driver has occurred. In this case, the variable reference time may be measured to a smaller value as the train torque (T) becomes larger (in this case, the reference torque is a value that is a criterion for measuring whether the driver has a steering intention, and may be designed in advance and set in the mode change controller 500 based on the specification of the MDPS system and the intention of the designer).

That is, as the column torque (T) becomes larger, this may be considered as a case where the driver has an urgent steering intention. In this case, the mode change controller 500 may be operative to change the reference time, which is used as the time taken to determine the steering intervention, since it is necessary to rapidly change the automatic driving mode to the manual driving mode by reducing the time taken to determine the steering intervention. Accordingly, as shown in fig. 2, the mode change controller 500 may enable a quick change to the manual driving mode under the emergency steering condition by measuring the variable reference time (@) as a value becomes smaller as the column torque (T) becomes larger, and similarly, as the column torque (T) becomes smaller, the variable reference time (@) is measured as a higher value. For example, the mode change controller 500 may determine the variable reference time corresponding to the currently detected column torque (T) with reference to a mapping table (or graph) between the column torque (T) and the variable reference time, such as shown in table 1 below, or correspondence information between the column torque (T) and the variable reference time, such as a function of the variable reference time of the column torque (T). The correspondence information between the column torque (T) and the variable reference time may be previously designed based on the MDPS system specification and the designer's intention, and is previously set in the mode change controller 500.

[ Table 1]

Column torque	Variable reference time
		5Nm	50ms
6Nm	40ms
		7Nm	30ms
8Nm	20ms
		9Nm	10ms

If the variable reference time is employed, since the variable reference time is reduced as the column torque (T) becomes larger, the time taken to determine steering intervention is reduced, enabling a faster change to the manual driving mode. An embodiment may be considered in which the driver's steering intervention is not determined when the column torque (T) converges to 0. In this case, the reference value of the column torque (T) at which the steering intervention of the driver is not determined may also be designed in advance based on the specification of the MDPS system and the intention of the designer, and may be incorporated into corresponding related information.

As described above, the column torque (T) applied to the steering column may include not only the column torque applied by the driver but also noise column torque that occurs in a situation that is not desired by the driver (for example, column torque generated when the driver touches the steering wheel when the driver is not steering intentionally). In the case where the noise column torque is the reference torque or more, if the noise column torque is maintained at the variable reference time or more determined based on the corresponding noise column torque, although the driver has no intention of steering intervention, there may occur a case where the driver has performed steering intervention according to the noise column torque. It is therefore necessary to filter out (or eliminate) such noise column torques and to determine the steering intervention of the driver from the filtered column torque (in particular the absolute value of the filtered column torque).

In order to filter out the noise column torque, the mode change controller 500 may include a filter unit (or band-stop filter) for filtering out the column torque (T) in a given frequency band, as shown in fig. 2. The frequency band filtered by the filter unit may be measured based on the steering angle acceleration (θ "v) of the steering wheel, and may be measured to include a resonance frequency caused by a mechanical mechanism based on the MDPS system (i.e., the frequency filtered band of the filter unit may be measured to include a resonance frequency measured based on the steering angle acceleration (θ" v)).

Specifically, according to mechanical mechanisms such as a steering wheel, a universal joint, and a torsion bar of the MDPS system, the noise column torque corresponds to vibration in a resonance frequency region. The vibration in the resonance frequency region cannot be perfectly eliminated by a conventional Low Pass Filter (LPF). Therefore, the present embodiment employs a configuration for finding the resonant frequency in which the mechanical mechanisms of the MDPS system (e.g., the inertia and rigidity of the steering wheel, the gimbal and the torsion bar) are incorporated, and filtering the resonant frequency by a band-stop filter.

In general, the resonant frequency can be modeled asIn this case, K represents a parameter (typically 2.1-2.8N) set in advance according to the characteristics of the torsion bar_mPer deg). J is the moment of inertia, which can be preset by testing, since it isA parameter that varies according to the diameter of the universal joint, the steering wheel, and the steering angular acceleration (θ "v). Therefore, the resonance frequency may also be preset to have a given range of values. For example, assuming that the resonance frequency has been preset to a value of 8 to 10Hz, the factor affecting the resonance frequency is the steering angle acceleration (θ "v). Therefore, the problem of erroneously determining the steering intervention of the driver due to the noise column torque, that is, when the steering angular acceleration (θ "v) has a high value and a frequency filtering region of the filter unit (i.e., band elimination filter) is designated, the target to be filtered needs to have a high value in the range of 8Hz to 10Hz so that the column torque (T) is filtered in the determined resonance frequency region, can be solved by determining the resonance frequency. In this case, the mode change controller 500 may determine the resonance frequency corresponding to the currently calculated steering angle acceleration (θ "v) with reference to a mapping table between the steering angle acceleration (θ" v) and the resonance frequency or correspondence information between the steering angle acceleration (θ "v) and the resonance frequency, for example, a function of the resonance frequency of the steering angle acceleration (θ" v). The correspondence information between the steering angle acceleration (θ "v) and the resonance frequency may be previously designed and previously set in the mode change controller 500 based on the specification of the MDPS system and the designer's intention.

Arrangements for determining a direct steering intervention by a driver when the vehicle is travelling in an autonomous driving mode have been mainly described. However, it is also necessary to consider a case where an obstacle needs to be urgently avoided by automatic steering during driving in the automatic driving mode. That is, in an emergency situation where it is necessary to avoid an obstacle during traveling in the autonomous driving mode, when a command steering angle (θ) based on a command for emergency steering is input from the autonomous driving system 600_ref) The actual column torque increases greatly. This corresponds to a case where the column torque (T) is increased by urgent automatic steering in order to avoid an obstacle during normal execution of the automatic driving mode rather than the steering intervention by the driver. Therefore, it is necessary to maintain the automatic driving mode without any change.

For this, the steering angle is determined based on the traveling environment of the vehicle (i.e., received from the automatic driving system 600)Commanded steering angle (theta)_ref) Angular acceleration, the mode change controller 500 may execute a process of limiting the determination of the steering intervention by the driver based on the column torque (T) and the variable reference time (for convenience, referred to as a limiting process). In this case, the steering angle (θ) can be commanded by_ref) Twice differentiating to calculate the command steering angle (theta)_ref) The angular acceleration of (a). LPF processing for noise removal may be further performed.

That is, although the column torque (T) is measured as the reference torque or more, when the angular acceleration of the command steering angle (θ ref) is large, it can be considered that the column torque (T) increases due to emergency automatic steering performed during execution of the automatic driving mode, rather than steering intervention by the driver. In this case, the mode change controller 500 may limit the determination of steering intervention by the driver.

As an example of the limiting process, the mode change controller 500 may use a follow-command steering angle (θ)_ref) The angular acceleration of (a) becomes large and the variable reference time is increased (i.e., when the steering angle (θ) is commanded_ref) Is a preset reference value or more, a method of delaying determination of driver steering intervention by increasing a variable reference time although the detected column torque (T) is equal to or greater than the reference torque and the variable reference time has a smaller value, or when the steering angle (θ) is commanded_ref) Is a preset reference value or more, the method of determining driver steering intervention based on column torque (T) and a variable reference time is stopped.

2. Changing from an autonomous driving mode to a manual driving mode

As described above, since abrupt steering of the driver occurs during the MDPS position control performed by the autopilot module, a large variation in the motor control current may occur, possibly resulting in a steering feeling of driver's variation. That is, when the mode is changed from the automatic driving mode to the manual driving mode, the immediate control stability is lowered due to the output difference in each mode control case. This may cause a feeling of difference such as abnormal behavior of the vehicle or steering vibration.

As means for solving these problems, the present embodiment adopts a configuration for performing mode change using a method of measuring a mode change time from an automatic driving mode to a manual driving mode based on a column torque (T), and commanding a current (I) to first and second assist_{ref_A}And I_{ref_B}) Applying a weight incorporating a mode change time, and determining a final assist command current (I) for driving the MDPS motor when changing from the automatic driving mode to the manual driving mode_{ref_final})。

Specifically, the mode change controller 500 may determine the mode change time based on the column torque at the time of determining that steering intervention by the driver has occurred (indicated as "determine column torque" for convenience). The measured column torque may be expressed as a column torque at the time of maintaining the column torque (T) at the preset reference torque or more to reach the variable reference time. In this case, as the column torque is measured to be larger, the mode change time from the automatic driving mode to the manual driving mode may be measured to a smaller value.

That is, as the measured column torque becomes larger, this may be considered as a case where the driver has an urgent steering intention. In this case, since it is necessary to rapidly change the automatic driving mode to the manual driving mode by reducing the time required for the mode change, the mode change controller 500 may operate based on the measured column torque to change the mode change time for changing to the manual driving mode. Thus, as shown in fig. 2, the mode change controller 500 may enable a quick change to the manual driving mode under the emergency steering condition by measuring the mode change time as a value that becomes smaller as the measured column torque becomes larger, and similarly, measuring the mode change time as a value that becomes higher as the measured column torque becomes smaller. For example, the mode change controller 500 may determine the mode change time corresponding to the currently detected measured column torque with reference to a map (or graph) between the measured column torque and the mode change time, or correspondence information between the measured column torque and the mode change time, such as a function of the mode change time depending on the measured column torque. The correspondence information between the measured column torque and the mode change time may be previously designed based on the MDPS system specification and the designer's intention, and may be previously set in the mode change controller 500. Further, as the column torque is measured to be larger, the mode change time may be measured to a smaller value in the entire region where the column torque is measured, and, as the column torque is measured to be larger, it may be measured to a smaller value only in some regions where the column torque is measured. That is, as the measured column torque becomes larger, the mode change controller 500 may measure the mode change time to a smaller value in at least a partial region of the measured column torque.

When the mode change time is measured through the above-described procedure, the mode change controller 500 may complete the operation of changing from the automatic driving mode to the manual driving mode within the measured mode change time. This configuration is described in detail below.

First, the mode change controller 500 may control the first and second auxiliary command currents (I)_{ref_A}And I_{ref_B}) Applying a weight incorporating a mode change time to determine a final assist command current (I) for driving the MDPS motor after the mode change_{ref_final}). In this case, the mode change controller 500 may apply the weight supplement to the first and second auxiliary command currents (I)_{ref_A} and I_{ref_B}) To determine a final auxiliary command current (I)_{ref_final}) (ii) a And the mode change controller may determine the final auxiliary command current (I)_{ref_final}) Such that the final assist command current changes from the second assist command current (I) as the value of the weight changes from a lower value to a higher value_{ref_B}) To a first auxiliary command current (I)_{ref_A}) Close. That is, as the value of weight K changes from a lower value to a higher value, it is merged to the final assist command current (I)_{ref_final}) Of (a) a first auxiliary command current (I)_{ref_A}) Is increased, the second auxiliary command current (I)_{ref_B}) The ratio of (a) to (b) is decreased. Final auxiliary command current (I)_{ref_final}) Can be determined by an exponential smoothing filter, such as equation 1 below.

I_{ref_final}＝KI_{ref_A}+(1-K)I_{ref_B}…(1)

According to equation 1, when the value K converges to 1, the final auxiliary command current (I)_{ref_final}) Becomes closer to the first auxiliary command current (I)_{ref_A}). With the value K converging to 0, the final auxiliary command current (I)_{ref_final}) Becomes closer to the second auxiliary command current (I)_{ref_B})。

Therefore, when the driver intends to release the automatic driving mode by forced steering in the automatic driving mode, the second assist command current (I) is applied_{ref_B}) Is gradually decreased, i.e., 1-K in equation 1, and is applied to the first assist command current (I)_{ref_A}) Gradually increases the gain of (i.e., the weight K). Therefore, when the mode is changed from the automatic driving mode to the manual driving mode, the automatic driving mode can be released more naturally without a feeling of difference in the steering wheel.

Further, in equation 1, the weight K may be designed to vary within a range between a preset lower limit (e.g., a value of 0) or more and a preset upper limit (e.g., a value of 1) or less, taking the mode change time as a factor, so that the change from the autonomous driving mode to the manual driving mode performed according to equation 1 may be completed within the mode change time. That is, if the weight is expressed as "x/T_translate”(T_translateIs the mode change time), and the parameter x is gradually changed from 0 to T_translateThe value of the weight is changed from 0 to 1 within the mode change time so that the final auxiliary command current reaches the first auxiliary command current (I)_{ref_A}). Thus, the mode change is completed.

Therefore, since the mode change time is determined based on the large column torque applied in the case where the driver has an urgent steering intention, the time required for the mode change is reduced. Furthermore, by applying an exponential smoothing filter (e.g., equation 1), the autonomous driving mode can be released more naturally without a sense of difference in the steering wheel.

3. In the autonomous driving mode, MDPSControl responsiveness of a system

As described above, the autopilot steering controller 400 may include a position controller and a speed controller for controlling the position and speed of the MDPS motor in the autopilot mode. In general, proportional (P) control is applied to a position controller, and Proportional Integral (PI) control is applied to a velocity controller. In this case, since an increase in the control response is limited, a Low Pass Filter (LPF) is generally applied to the front end of the differential (D) controller. However, in this case, the structure of the MDPS system is complicated, and it is difficult to control the MDPS motor due to an increased tuning factor.

In order to simplify the structure of the MDPS system and optimize the tuning factor while increasing the control responsiveness, the automatic steering controller 400 according to the present embodiment may be designed to determine the second assist command current (I) using a variable High Pass Filter (HPF)_{ref_B}) The variable high-pass filter has a command-based steering angle (theta)_ref) And a differential (D) control gain calculated based on a position control gain and a differential parameter (or a differential time) of the PID control.

Specifically, in a general PID controller, when an LPF or a hysteresis compensator is applied to the D controller, the transfer function is as shown in equation 2.

In equation 2, K_pIndicating the position control gain. T is_iAnd T_dIs the control time of the D controller, integration time and differentiation time, respectively.

In equation 2, if the position is controlled by the gain (K)_p) Divided into integral control gains (K)_i) And differential control gain (K)_d) Then, the integral control gain (K) is arranged_i) And differential control gain (K)_d) Equation 3 can be derived.

In equation 3, the differential control term is again arranged to obtain equation 4.

In equation 4, it can be seen that this term has the format of the primary HPF. Therefore, if the LPF or the hysteresis compensator is not applied to the D controller but the specified D control gain G is set and the HPF is applied to the D controller, a system configuration having high control responsiveness and strong noise and interference resistance can be designed.

By adopting this design method, it is possible to consider a design if the command steering angle (θ) of the position controller_ref) Faster (i.e., if steering angle (θ) is commanded_ref) Large angular velocity of (a) no response to vibration and interference will occur; if the commanded steering angle (theta) of the position controller_ref) Slower (i.e., if steering angle (θ) is commanded_ref) Less) and increases the gain and frequency response required for the steering region by lowering the cutoff frequency of the HPF, and makes the response insensitive to noise by increasing the cutoff frequency of the HPF.

Accordingly, in the present embodiment, as shown in fig. 2, the automatic steering controller 400 may determine the second assist command current (I) using the variable HPF_{ref_B}) The variable HPF has a command-based steering angle (theta)_ref) And position control gain (K) based on PID control_p) And a differential parameter (T)_d) Calculated D control gain G (G ═ K)_p*T_d). If abrupt avoidance of steering is required in the autonomous driving mode, the position control of the MDPS motor can be performed very efficiently and actively by this design. Further, if the control response continues to increase, at the time of normal driving, since disturbance or noise is amplified, the performance of position control is lowered, but the performance of position control can be maintained and driving stability can be improved by this design. As shown in fig. 2, the current steering angle(θ_v) And a command steering angle (theta)_ref) The error value in between is input to the variable HPF as input. The cutoff frequency is based on the commanded steering angle (θ)_ref) Is measured. D controlling the gain G by controlling the position of the gain (K)_p) Multiplied by the differential time (T)_d) Is calculated.

Fig. 3 is a flowchart for describing a method of controlling an MDPS system according to an embodiment of the present disclosure. Hereinafter, the method of controlling the MDPS system according to the present embodiment is described with reference to fig. 3, and a description overlapping with the foregoing description is omitted for convenience.

First, whether steering intervention by the driver has occurred is determined by the mode change controller 500 based on a variable reference time that is variably determined according to a column torque (T) applied to the vehicle in the autonomous driving mode of the vehicle (S100);

in step S100, if the state in which the column torque (T) is the preset reference torque or more is maintained for the variable reference time or more, the mode change controller 500 may determine that steering intervention by the driver has occurred. In this case, the mode change controller 500 may measure the variable reference time to a smaller value as the column torque (T) becomes larger. Further, in step S100, the mode change controller 500 filters a column torque (T) in a frequency band, the column torque being measured based on a steering angular acceleration (θ "v) of a steering wheel of the vehicle, and the column torque being measured to include a resonance frequency caused based on a mechanical mechanism of an MDPS system mounted on the vehicle, and may measure a steering intervention of the driver from the filtered column torque.

In step S100, the mode change controller 500 may execute a limiting process based on the column torque (T) and the steering angle (θ) depending on the command_ref) The variable reference time of the angular acceleration of (a) limits the determination of the steering intervention of the driver. If the steering angle (theta) is commanded_ref) Is a preset reference value or more, a following command steering angle (theta) may be set_ref) Based on the column torque (T) and the variable reference time or the method of increasing the variable reference time with a greater angular accelerationThe method of time-lapse determination of the steering intervention of the driver is used as the method of the limiting process.

If it is determined at step S100 that steering intervention by the driver has occurred, the mode change controller 500 determines a mode change time from the automatic driving mode to the manual driving mode of the driver based on the column torque (T) (S200).

In step S200, the mode change controller 500 may determine the mode change time based on the measured column torque, that is, determine the column torque at which the driver has performed the steering intervention, and may determine the mode change time as a smaller value in at least a partial region of the measured column torque when the measured column torque becomes larger.

Then, the mode change controller 500 controls the first and second auxiliary command currents (I)_{ref_A}And I_{ref_B}) Applying a weight incorporating a mode change time, and determining a final assist command current (I) for driving the MDPS motor when changing from the automatic driving mode to the manual driving mode_{ref_final}). As described above, the first and second auxiliary command currents (I)_{ref_A}And I_{ref_B}) Are currents for driving the MDPS motor in a manual driving mode and an automatic driving mode, respectively (S300).

In step S300, the mode change controller 500 may supplement the application of the weight to the first and second auxiliary command currents (I)_{ref_A}And I_{ref_B}) To determine a final auxiliary command current (I)_{ref_final}) (ii) a And the mode change controller may determine the final auxiliary command current (I)_{ref_final}) Such that the final assist command current changes from the second assist command current (I) as the value of the weight changes from a lower value to a higher value_{ref_B}) To a first auxiliary command current (I)_{ref_A}) Close. In this case, the weight may be set to vary within a range between above a preset lower limit and below a preset upper limit, taking the mode change time as a factor. Accordingly, the mode change controller 500 may complete the change from the automatic driving mode to the manual driving mode within the mode change time.

In addition, a second auxiliary command current (I)_{ref_B}) Can be used forTo pass through a steering angle (theta) based on the command_ref) And can be determined by considering a variable High Pass Filter (HPF) having a steering angle (θ) based on the command_ref) And a differential (D) control gain calculated based on the position control gain of the PID control and a differential parameter.

As described above, according to the present embodiment, when the mode is changed from the automatic driving mode to the manual driving mode, the steering intervention of the driver is measured using the variable reference time that is actively changed based on the column torque. Therefore, at the time of sudden steering, it is possible to quickly release the automatic driving mode and quickly enter the manual driving mode. Further, the driving of the MDPS motor is controlled by optimally determining the assist command current for driving the MDPS motor by a given weight, which incorporates the time for the mode change. Therefore, control stability for the MDPS can be ensured and a feeling of difference, such as abnormal behavior of the vehicle or steering vibration, can be reduced at the time of the mode change.

The embodiments described in this specification may be implemented as, for example, a method or process, an apparatus, a software program, a data stream, or a signal. Although the present disclosure has been discussed in the context of only a single form of implementation (e.g., discussed only as a method), an implementation having the features discussed may also be implemented in another form (e.g., an apparatus or program). The apparatus may be implemented as suitable hardware, software or firmware. For example, the method may be implemented in an apparatus, such as a processor, which is generally referred to as a processing device, including a computer, microprocessor, integrated circuit, or programmable logic device. Processors include communication devices such as computers, cellular telephones, mobile telephones/personal digital assistants ("PDAs"), and another type of device that facilitates the communication of information between end-users.

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