阅读说明：本技术 用于控制电机驱动动力转向系统的设备和方法 (Apparatus and method for controlling motor-driven power steering system ) 是由 金泰弘 于 2020-11-16 设计创作，主要内容包括：一种用于控制电机驱动动力转向系统的设备和方法,该设备可包括：自主驾驶取消确定单元,被配置为在自主驾驶情况下使用通过带阻滤波器的列扭矩来确定是否取消自主驾驶；以及信号处理单元,被配置为使用从自主驾驶系统输出的命令转向角信息来计算命令转向角加速度信息。当转向角加速度信息大于或等于预定参考值时,自主驾驶取消确定单元可确定自主驾驶系统执行了紧急转向,并且禁止取消自主驾驶。(An apparatus and method for controlling a motor driven power steering system, the apparatus may include: an autonomous driving cancellation determination unit configured to determine whether to cancel autonomous driving using the column torque through the band elimination filter in the case of autonomous driving; and a signal processing unit configured to calculate command steering angle acceleration information using the command steering angle information output from the autonomous driving system. When the steering angle acceleration information is greater than or equal to a predetermined reference value, the autonomous driving cancellation determining unit may determine that the autonomous driving system performs urgent steering, and prohibit cancellation of autonomous driving.)

1. An apparatus for controlling a motor driven power steering system, comprising:

an autonomous driving cancellation determination unit configured to determine whether to cancel autonomous driving using the column torque passing through the band elimination filter in the case of autonomous driving; and

a signal processing unit configured to calculate command steering angle acceleration information using command steering angle information output from the autonomous driving system,

wherein the autonomous driving cancellation determining unit determines that urgent steering is performed by the autonomous driving system and prohibits cancellation of the autonomous driving when steering angle acceleration information is greater than or equal to a predetermined reference value.

2. The apparatus of claim 1, wherein the band-stop filter is a filter for removing column torque of frequency components generated in the event of an accidental steering intervention by a user,

wherein the frequency component generated in the case of the user's accidental steering intervention has the same vibration frequency as a resonance point of a torsion bar of the motor-driven power steering system within an error range.

3. The apparatus according to claim 1, wherein the autonomous driving cancellation determining unit removes, through the band-elimination filter, a column torque of a frequency component generated in the event of an accidental steering intervention by a user, and prohibits cancellation of the autonomous driving even if the accidental steering intervention by the user occurs.

4. The apparatus according to claim 1, wherein the autonomous driving cancellation determining unit cancels the autonomous driving when a command steering angle applied from the autonomous driving system is greater than or equal to a maximum steering angle specified based on a geometric characteristic of a vehicle, and cancels the autonomous driving even when a steering angle speed greater than or equal to a specified reference value is input.

5. The apparatus according to claim 1, wherein the emergency steering indicating column torque of the autonomous driving system significantly increases to a predetermined reference value or more as a torsion bar is instantaneously sharply deformed by steering by the autonomous driving system.

6. The apparatus of claim 1, wherein the signal processing unit comprises:

a first differentiator and a second differentiator configured to calculate a steering angle acceleration by differentiating a command steering angle output from the autonomous driving system twice in succession; and

a low-pass filter configured to process and correct noise from the calculated steering angle acceleration.

7. The apparatus of claim 1, wherein the signal processing unit further comprises:

a gain adjustment unit that improves instantaneous gain responsiveness by increasing a gain of a steering angle position controller in a case where the autonomous driving system is urgently steered; and

a variable high-pass filter configured to monitor a position control error of the steering angle position controller, change the urgent steering autonomous driving mode to a general autonomous driving mode when a current steering angle reaches a required command steering angle, and adjust a cutoff frequency and a gain to a cutoff frequency and a gain corresponding to the general autonomous driving mode.

8. The apparatus of claim 7, wherein the variable high pass filter decreases a cutoff frequency to increase gain and frequency response in the event of the autonomous driving system emergency steering and increases the cutoff frequency to decrease gain and frequency response in other than the autonomous driving system emergency steering.

9. The apparatus of claim 7, wherein the variable high pass filter receives a position control error corresponding to a difference between the current steering angle and the commanded steering angle, determines a cutoff frequency according to a commanded steering angle speed, increases the cutoff frequency by decreasing a differentiation time when a vehicle speed is high, and decreases the cutoff frequency by increasing the differentiation time when the vehicle speed is low.

10. The apparatus according to claim 7, further comprising a vibration detection unit configured to monitor, in real time, a frequency at which a sign of a steering angular velocity changes within a predetermined time to prevent an increase in gain of the steering angular position controller due to vibration caused by an external environmental factor or vibration of a cutoff frequency of the variable high-pass filter in the case of an urgent steering of the autonomous driving system;

wherein the variable high-pass filter changes an emergency steering autonomous driving mode to the general autonomous driving mode and adjusts a cutoff frequency and a gain to a cutoff frequency and a gain corresponding to the general autonomous driving mode when the vibration detection unit detects vibration greater than or equal to a specified reference value.

11. A method for controlling a motor driven power steering system, comprising:

calculating, by a signal processing unit of the motor-driven power steering system, command steering angle acceleration information using command steering angle information output from an autonomous driving system; and

when the steering angle acceleration information is greater than or equal to a predetermined reference value, it is determined by an autonomous driving cancellation determination unit that urgent steering is performed by the autonomous driving system, and cancellation of autonomous driving is prohibited.

12. The method of claim 11, further comprising: determining, by the autonomous driving cancellation determining unit, whether to cancel the autonomous driving using the column torque through the band elimination filter in a case of the autonomous driving,

wherein the band-stop filter is a filter for removing a column torque of a frequency component generated in the event of an accidental steering intervention by a user, and

the frequency component generated in the case of the user's accidental steering intervention has the same vibration frequency as a resonance point of a torsion bar of the motor-driven power steering system within an error range.

13. The method according to claim 11, wherein the autonomous driving cancellation determining unit removes, through a band elimination filter, a column torque of a frequency component generated in the event of an accidental turn intervention by a user, and prohibits cancellation of the autonomous driving even if the accidental turn intervention by the user occurs.

14. The method according to claim 11, wherein the autonomous driving cancellation determining unit cancels the autonomous driving when a command steering angle applied from the autonomous driving system is greater than or equal to a maximum steering angle specified based on a geometric characteristic of a vehicle, and cancels the autonomous driving even when a steering angle speed greater than or equal to a specified reference value is input.

15. The method according to claim 11, wherein the emergency steering column torque of the autonomous driving system significantly increases to a predetermined reference value or more as a torsion bar is instantaneously sharply deformed by steering by the autonomous driving system.

16. The method according to claim 11, wherein, when calculating the commanded steering angle acceleration information using the commanded steering angle information output from the autonomous driving system,

the signal processing unit includes:

a first differentiator and a second differentiator configured to calculate a steering angle acceleration by differentiating a command steering angle output from the autonomous driving system twice in succession; and

a low-pass filter configured to process and correct noise from the calculated steering angle acceleration.

17. The method of claim 11, further comprising: in the event of an emergency turn by the autonomous driving system:

improving instantaneous gain responsiveness by increasing a gain of the steering angle position controller by the gain adjustment unit; and is

The position control error of the steering angle position controller is monitored by a variable high-pass filter, which changes an urgent steering autonomous driving mode to a general autonomous driving mode when a current steering angle reaches a required command steering angle, and adjusts a cutoff frequency and a gain to a cutoff frequency and a gain corresponding to the general autonomous driving mode.

18. The method of claim 17, wherein, in adjusting the cutoff frequency and gain,

the variable high pass filter decreases a cutoff frequency to increase a gain and a frequency response in case of the urgent steering of the autonomous driving system, and increases the cutoff frequency to decrease the gain and the frequency response in other cases than the urgent steering of the autonomous driving system.

19. The method of claim 17, wherein, in adjusting the cutoff frequency and gain,

the variable high-pass filter receives a position control error corresponding to a difference between the current steering angle and the command steering angle, determines a cutoff frequency according to a command steering angular velocity, increases the cutoff frequency by decreasing a differential time when a vehicle speed is high, and decreases the cutoff frequency by increasing the differential time when the vehicle speed is low.

20. The method according to claim 17, further comprising monitoring, by a vibration detection unit, a frequency at which a sign of a steering angular velocity changes within a predetermined time in real time to prevent an increase in gain of the steering angular position controller due to vibration caused by an external environmental factor or vibration of a cutoff frequency of the variable high-pass filter in case of urgent steering of the autonomous driving system;

wherein the variable high-pass filter changes an emergency steering autonomous driving mode to the general autonomous driving mode and adjusts a cutoff frequency and a gain to a cutoff frequency and a gain corresponding to the general autonomous driving mode when the vibration detection unit detects vibration greater than or equal to a specified reference value.

Technical Field

Exemplary embodiments of the present disclosure relate to an apparatus and method for controlling an MDPS (motor driven power steering) system, and more particularly, to an apparatus and method for controlling an MDPS system capable of performing emergency steering while maintaining an autonomous driving mode in an emergency situation where a collision or other accident risk suddenly occurs during autonomous driving of a vehicle.

Background

In general, a hydraulic power steering apparatus using a hydraulic pump is used as a power-assisted steering apparatus of a vehicle. However, after the 1990 s, MDPS systems using electric motors have been in widespread use.

In the existing hydraulic power steering apparatus, a hydraulic pump used as a power source to supply power is driven by an engine and consumes energy at all times regardless of whether a steering wheel is rotated. However, in the MDPS system, when the steering wheel is rotated to generate torque, the motor driven by electric energy provides steering assist power.

Therefore, when the MDPS system (or MDPS) is used, the energy efficiency of the vehicle can be further improved as compared to when the hydraulic power steering apparatus is used.

A vehicle to which the autonomous driving mode according to the related art is applied has been designed to determine that autonomous driving is not normal when the vehicle is urgently steered during autonomous driving, and to cancel autonomous driving. This is because, in general, a situation in which the vehicle is urgently steered in autonomous driving does not occur. When the vehicle is turned suddenly, a dangerous situation may occur in which the driver is greatly inclined in the direction opposite to the turning of the vehicle. However, when an emergency avoidance operation is required to prevent an accident, the autonomous driving mode may be maintained, thereby emergently steering the vehicle.

In other words, when a risk of a collision or other accident suddenly occurs during autonomous driving, it is necessary to design a vehicle to which an autonomous driving mode is applied to avoid the risk of an accident by reducing the vehicle speed or controlling steering. However, a vehicle to which the existing autonomous driving mode is applied is designed only to cope with a typical case where an obstacle is detected at a specified distance in advance, and is not designed to cope with an emergency (for example, a case where a pedestrian or other vehicle suddenly appears in front of the vehicle).

Therefore, in a non-emergency situation, it is generally effective to reduce the vehicle speed in advance. However, in an emergency situation (e.g., where a pedestrian or other vehicle suddenly appears in front of the vehicle), emergency steering of the vehicle may be more effective to avoid an accident. However, when the autonomous driving mode is cancelled or abnormally performed in an emergency such as in a vehicle to which the existing autonomous driving mode is applied, a driver (or a user) may be in a more dangerous situation. Therefore, there is a need for a technology capable of maximizing responsiveness so that a vehicle can be instantaneously and rapidly steered in response to an emergency while continuously maintaining an autonomous driving mode.

The related art of the present disclosure is disclosed in korean patent No. 10-0247334 entitled "motor-driven power steering apparatus", which was registered 10.12.10.1999.

Disclosure of Invention

Various embodiments relate to an apparatus and method for controlling an MDPS system, which can perform emergency steering in an emergency situation at risk of sudden occurrence of a collision or other accident during autonomous driving of a vehicle, while maintaining an autonomous driving mode.

In an embodiment, an apparatus for controlling an MDPS system may include: an autonomous driving cancellation determination unit configured to determine whether to cancel autonomous driving using the column torque passing through the band elimination filter in the case of autonomous driving; and a signal processing unit configured to calculate command steering angle acceleration information using the command steering angle information output from the autonomous driving system. The autonomous driving cancellation determining unit determines that urgent steering is performed by the autonomous driving system and prohibits cancellation of the autonomous driving when steering angle acceleration information is greater than or equal to a predetermined reference value.

The band-stop filter may be a filter for removing a column torque of a frequency component generated in the case of an accidental steering intervention by a user.

The frequency component generated in the case of the user's accidental steering intervention has the same vibration frequency as the resonance point of the torsion bar of the MDPS system within an error range.

The autonomous driving cancellation determining unit may remove, through the band elimination filter, a column torque of a frequency component generated in the event of an accidental steering intervention by a user, and prohibit cancellation of the autonomous driving even if the accidental steering intervention by the user occurs.

The autonomous driving cancellation determining unit may cancel the autonomous driving when a command steering angle applied from the autonomous driving system is greater than or equal to a maximum steering angle specified based on a geometric characteristic of the vehicle, and cancel the autonomous driving even when a steering angle speed greater than or equal to a specified reference value is input.

As the torsion bar is instantaneously sharply deformed by the steering by the autonomous driving system, the urgent steering of the autonomous driving system may indicate that the column torque is significantly increased to a predetermined reference value or more.

The signal processing unit may include: a first differentiator and a second differentiator configured to calculate a steering angle acceleration by differentiating a command steering angle output from the autonomous driving system twice in succession; and an LPF (low pass filter) configured to process and correct noise from the calculated steering angle acceleration.

The signal processing unit may further include: a gain adjustment unit that improves instantaneous gain responsiveness by increasing a gain of a steering angle position controller in a case where the autonomous driving system is urgently steered; and a variable HPF (high pass filter) configured to monitor a position control error of the steering angle position controller, change the urgent steering autonomous driving mode to a general autonomous driving mode when a current steering angle reaches a required command steering angle, and adjust a cutoff frequency and a gain to a cutoff frequency and a gain corresponding to the general autonomous driving mode.

The position control error may indicate a value corresponding to a difference between the commanded steering angle and the current steering angle.

The variable HPF decreases a cutoff frequency to increase a gain and a frequency response in case of the urgent steering of the autonomous driving system, and increases the cutoff frequency to decrease the gain and the frequency response in other cases than the urgent steering of the autonomous driving system.

The variable HPF may receive a position control error corresponding to a difference between the current steering angle and the command steering angle, determine a cutoff frequency according to a command steering angular velocity, increase the cutoff frequency by decreasing a differential time when a vehicle speed is high, and decrease the cutoff frequency by increasing the differential time when the vehicle speed is low.

A vibration detection unit configured to monitor in real time a frequency at which a sign of a steering angular velocity changes within a predetermined time to prevent an increase in gain of the steering angular position controller due to vibration caused by an external environmental factor or vibration of a cutoff frequency of the variable HPF in the case of an urgent steering of the autonomous driving system may be further included. When the vibration detection unit detects vibration greater than or equal to a specified reference value, the variable HPF may change the emergency steering autonomous driving mode to the general autonomous driving mode and adjust a cutoff frequency and a gain to a cutoff frequency and a gain corresponding to the general autonomous driving mode.

In an embodiment, a method for controlling an MDPS system may include: calculating, by a signal processing unit of the MDPS system, command steering angle acceleration information using command steering angle information output from an autonomous driving system; and determining, by an autonomous driving cancellation determining unit, that urgent steering is performed by the autonomous driving system and prohibiting cancellation of the autonomous driving, when the steering angle acceleration information is greater than or equal to a predetermined reference value.

The method may further comprise: in the case of autonomous driving, determining, by the autonomous driving cancellation determining unit, whether to cancel the autonomous driving using the column torque passing through the band elimination filter. The band-stop filter may be a filter for removing a column torque of a frequency component generated in the case of an accidental steering intervention by a user.

The frequency component generated in the case of the user's accidental steering intervention may have the same vibration frequency as the resonance point of the torsion bar of the MDPS system within an error range.

The autonomous driving cancellation determining unit may remove, through a band elimination filter, a column torque of a frequency component generated in the event of an accidental steering intervention by a user, and prohibit cancellation of the autonomous driving even if the accidental steering intervention by the user occurs.

The autonomous driving cancellation determining unit may cancel the autonomous driving when a command steering angle applied from the autonomous driving system is greater than or equal to a maximum steering angle specified based on a geometric characteristic of the vehicle, and cancel the autonomous driving even when a steering angle speed greater than or equal to a specified reference value is input.

As the torsion bar is instantaneously sharply deformed by the steering by the autonomous driving system, the urgent steering of the autonomous driving system may indicate that the column torque is significantly increased to a predetermined reference value or more.

In calculating the command steering angle acceleration information using the command steering angle information output from the autonomous driving system, the signal processing unit may include: a first differentiator and a second differentiator configured to calculate a steering angle acceleration by differentiating a command steering angle output from the autonomous driving system twice in succession; and an LPF (low pass filter) configured to process and correct noise from the calculated steering angle acceleration.

The method can further comprise the following steps: in the case of emergency steering by the autonomous driving system, improving instantaneous gain responsiveness by increasing the gain of a steering angle position controller by a gain adjustment unit; and monitoring a position control error of the steering angle position controller by a variable HPF, changing the urgent steering autonomous driving mode to a general autonomous driving mode when a current steering angle reaches a required command steering angle, and adjusting a cutoff frequency and a gain to a cutoff frequency and a gain corresponding to the general autonomous driving mode.

The position control error may indicate a value corresponding to a difference between the commanded steering angle and the current steering angle.

In adjusting the cutoff frequency and gain, the variable HPF decreases the cutoff frequency to increase the gain and frequency response in case of an urgent steering of the autonomous driving system, and increases the cutoff frequency to decrease the gain and frequency response in other cases than the urgent steering of the autonomous driving system.

The variable HPF may receive a position control error corresponding to a difference between the current steering angle and the command steering angle when adjusting the cutoff frequency and the gain, determine the cutoff frequency according to the command steering angular velocity, increase the cutoff frequency by decreasing the differential time when the vehicle speed is high, and decrease the cutoff frequency by increasing the differential time when the vehicle speed is low.

The method may further include monitoring, in real time, a frequency at which a sign of a steering angular velocity changes within a predetermined time by a vibration detection unit to prevent an increase in gain of the steering angular position controller due to vibration caused by an external environmental factor or vibration of a cutoff frequency of the variable HPF in case of an urgent steering of the autonomous driving system. When the vibration detection unit detects vibration greater than or equal to a specified reference value, the variable HPF may change the emergency steering autonomous driving mode to the general autonomous driving mode and adjust a cutoff frequency and a gain to a cutoff frequency and a gain corresponding to the general autonomous driving mode.

According to an embodiment of the present disclosure, an apparatus and method for controlling an MDPS system may perform emergency steering in an emergency situation where there is a risk of sudden collision or other accident during autonomous driving of a vehicle, while maintaining an autonomous driving mode, thereby avoiding the occurrence of an accident.

Drawings

Fig. 1 is a diagram showing a schematic configuration of an apparatus for controlling an MDPS system according to an embodiment of the present disclosure.

Fig. 2 is a diagram for describing a method in which the vibration detection unit monitors a change in sign of the steering angular velocity in fig. 1.

Fig. 3 is a diagram for facilitating understanding of the characteristics of the variable HPF (high pass filter) in fig. 1.

Fig. 4 is a graph showing the responsiveness of the experimental result according to the steering angle position controller in fig. 1 compared with the related art.

Detailed Description

Some example embodiments may be shown in the drawings in terms of functional blocks, units and/or modules, as is conventional in the relevant art. Those of ordinary skill in the art will appreciate that the blocks, units and/or modules are physically implemented by electronic (or optical) circuits such as logic circuits, discrete components, processors, hardwired circuits, memory elements, wired connections, and so on. When the blocks, units, and/or modules are implemented by a processor or similar hardware, they may 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 for performing some functions or as a combination of dedicated hardware and a processor (e.g., one or more programmed processors and associated circuitry) for performing other functions. Each block, unit and/or module of some example embodiments may be physically separated into two or more interacting and discrete blocks, units and/or modules without departing from the scope of the present inventive concept. Furthermore, the blocks, units and/or modules of some example embodiments may be physically combined into more complex blocks, units and/or modules without departing from the scope of the present inventive concept.

Hereinafter, an apparatus and method for controlling an MDPS (motor driven power steering) system will be described with reference to the accompanying drawings through various exemplary embodiments.

It should be noted that the drawings are not to precise scale and that the thickness of lines or the size of components may be exaggerated for descriptive convenience and clarity only. Further, terms used herein are defined by considering functions of the present invention, and may be changed according to custom or intention of a user or an operator. Accordingly, the terms should be defined in light of the overall disclosure set forth herein.

Fig. 1 is a diagram showing a schematic configuration of an apparatus for controlling an MDPS system according to an embodiment of the present disclosure.

As shown in fig. 1, the apparatus for controlling an MDPS system according to an embodiment of the present disclosure includes a band elimination filter 110, an autonomous driving cancellation determination unit 120, a vibration detection unit 130, an autonomous driving system 140, a steering angle position controller 150, and a signal processing unit 160. The signal processing unit 160 includes a variable HPF (high pass filter) 161, a gain adjustment unit 162, a first differentiator 163, a second differentiator 164, and an LPF (low pass filter) 165.

The autonomous driving cancellation determination unit 120 determines whether to cancel autonomous driving using a signal obtained by passing the column torque through the band elimination filter 110 in other general autonomous driving situations other than a predetermined emergency situation (e.g., a collision avoidance situation by emergency steering of the autonomous driving system).

For example, in the case of an accidental steering intervention by a user (i.e., vibration caused by the user touching the steering wheel, not a steering operation), vibration similar to the resonance point of the torsion bar of the MDPS system may be caused (i.e., the vibration frequencies within the error range are the same). In this case, the autonomous driving cancellation determining unit 120 removes the column torque of the corresponding frequency component (i.e., the column torque of the frequency component caused by the unexpected steering intervention of the user) by filtering the vibration through the band elimination filter 110. With this operation, the autonomous driving cancellation determining unit 120 does not cancel the autonomous driving even if an unexpected steering intervention by the user occurs.

The autonomous driving cancellation determining unit 120 receives the command steering angle and the steering angular velocity information, and determines whether to cancel autonomous driving.

For example, when a command steering angle greater than or equal to the maximum steering angle based on the geometric characteristics of the vehicle is applied from the autonomous driving system 140, the autonomous driving cancellation determination unit 120 cancels autonomous driving. Further, when the steering angular velocity corresponds to a situation in which it is difficult for the driver to comfortably ride during autonomous driving or a level at which control cannot be performed (i.e., when a steering angular velocity greater than or equal to a reference value is input), the autonomous driving cancellation determining unit 120 cancels autonomous driving.

For reference, the case where the autonomous driving cancellation determination unit 120 cancels autonomous driving corresponds to a case where the driver safely uses autonomous driving in a general autonomous driving situation other than a specified emergency situation (e.g., a collision avoidance situation caused by urgent steering of the autonomous driving system). This situation may vary depending on the geometry of the vehicle. That is, since the magnitude and the rate of change of the lateral acceleration or the yaw rate can be changed according to the length and the weight of the vehicle and the steering angle characteristic based on the gear ratio, the situation is adjusted in consideration of the characteristic of each vehicle and stored in an internal memory (not shown).

However, as described above, when the vehicle is unable to avoid a collision even when the vehicle speed is reduced due to a sudden occurrence of an obstacle, it is necessary to avoid the collision by urgent steering (or urgent steering).

In this case, when the emergency steering is performed by the autonomous driving system 140, the torsion bar is instantaneously and sharply deformed to significantly increase the line torque. Therefore, in the related art, the autonomous driving cancellation determining unit 120 may determine that the driver intends to make an urgent steering, thereby canceling the autonomous driving.

However, this situation (i.e., emergency steering of the autonomous driving system) does not correspond to the predetermined general autonomous driving situation.

Thus, the autonomous driving may be cancelled according to an existing autonomous driving cancellation situation in which the autonomous driving is cancelled when the column torque is greater than or equal to the predetermined level.

That is, to avoid the obstacle, the autonomous driving system 140 may issue an emergency steering command to increase the line torque. In this case, when the autonomous driving cancellation determining unit 120 erroneously determines that the column torque is increased due to the intentional steering intervention by the user and the autonomous driving is cancelled, the vehicle may not avoid the obstacle but collide with the obstacle.

In order to prevent the autonomous driving cancellation determination unit 120 from erroneously determining that the urgent steering is the steering intervention of the user in the case where the autonomous driving system makes the urgent steering, it is necessary to calculate the command steering angle acceleration information from the command steering angle information output by the autonomous driving system 140.

In general, since the rotation torque is proportional to the product of the rotation inertia moment and the steering angular acceleration, it is expected that the rotation torque will increase when the commanded steering angular acceleration is greater than or equal to a specified reference value. Therefore, the steering angle acceleration is calculated by differentiating the command steering angle output from the autonomous driving system 140 twice by the first differentiator 163 and the second differentiator 164, and the noise generated at this time is processed and corrected by the LPF 165. When the steering angle acceleration value corrected and output by the LPF 165 is greater than or equal to a prescribed reference value, the autonomous driving cancellation determining unit 120 prohibits cancellation of autonomous driving.

For reference, the magnitude of the steering angle acceleration for prohibiting the autonomous driving cancellation indicates a momentary change in the turning angle of the vehicle, and does not need to be changed according to the characteristics of the vehicle. Therefore, the reference steering angle acceleration may be determined through testing and applied to a memory (not shown) and then used for various vehicles.

Further, when an urgent steering command is input from the autonomous driving system 140, the autonomous driving cancellation determining unit 120 may prevent cancellation of autonomous driving. Based on the vehicle speed and the steering angle acceleration generated at this time, the performance of the steering angle position controller 150 can be changed by the variable HPF161 and the gain adjustment unit 162 as shown in fig. 3.

Generally, when the vehicle speed is high, the road load of the vehicle is reduced. On the other hand, when the vehicle speed is low, the road load of the vehicle increases, and a high output is required during steering. Further, when the steering angular velocity is high, high output is required, and when the steering angular velocity is low, low output is required. When vehicle speed is low, the cutoff frequency of variable HPF161 may be reduced to account for the wider bandwidth. When vehicle speed is high, the cutoff frequency of variable HPF161 may be increased to account for the narrow bandwidth. This is because, when the vehicle speed is high, the control stability of the MDPS system may be reduced due to road noise or noise of a mechanism or a tire.

Further, the gain adjustment unit 162 increases the gain G when the steering angular velocity is high, and decreases the gain G when the steering angular velocity is low. Therefore, when the urgent steering is required, the gain G is increased to significantly improve the instantaneous gain responsiveness.

The variable HPF161 monitors the position control error (i.e., the commanded steering angle — the current steering angle) of the steering angle position controller 150. When the current steering angle reaches the required commanded steering angle, variable HPF161 restores the emergency steering autonomous driving mode setting to the general autonomous driving mode setting (e.g., cutoff frequency and gain G).

For reference, the control characteristic of the steering angle position controller 150 improved by applying the variable HPF161 is described below.

Generally, a D controller (or a differential controller) is added to the steering angle position controller 150 to improve responsiveness to a position change. In this case, however, noise generated by disturbance or introduced from the external environment may be amplified to cause vibration, and the performance of the steering angle position controller 150 may be degraded. To prevent performance degradation, an LPF or hysteresis compensator is typically applied to the front stage of the D controller. However, when the structure becomes complicated and needs to be changed according to the steering situation, the number of parameters or factors to be changed increases. That is, in the general P-PI configuration of the steering angle position controller 150, the P controller stage is designed as PI or PID, and PI-PI or PID-PI configuration is used. Therefore, there is a need for a more efficient method that maximizes the performance of the controller according to the steering situation and significantly improves the responsiveness while resisting noise or interference.

Therefore, when an LPF or a hysteretic compensator is generally used as a D controller (or a derivative controller) in a PID controller (or a proportional-derivative-integral controller), the following equation can be established: g(s) ═ Kp (1+1/Ti + Td/(1 + s) Td)). When the PID control gains are split to rearrange the equations, or the gains are split to adapt Kp to an I or D controller, the equations can be expressed as g(s) ═ Kp + Ki/Ti × s + Kd × s/(1+ Td × s). At this time, for the D controller, the equations may be rearranged to (1/Td)/((1/Td + s) × Td × Kp s.

That is, when a hysteresis compensator or an LPF is not applied as the D controller, but a dedicated D control gain is set and an HPF is applied, a structure of noise or interference resistance can be made while improving responsiveness. Here, Ti and Td represent control times of the respective controllers, where Ti represents an integration time and Td represents a differentiation time.

Therefore, in the present embodiment, when the commanded steering speed input to the steering angle position controller 150 is high, the cutoff frequency of the variable HPF161 is lowered according to the above-described control characteristics. I.e. the required gain of the frequency response and steering region is improved. On the other hand, when the commanded steering speed is low, the cutoff frequency of HPF161 increases. That is, the required gain of the frequency response and steering region is reduced to make the structure insensitive to noise so that the structure does not react to vibration or interference.

Therefore, when collision avoidance by urgent steering is required during autonomous driving, the position control can be performed efficiently and actively.

When the control response is continuously improved even after the completion of the emergency steering, the disturbance or noise is amplified, thereby reducing the performance of the position control during general driving. However, when the emergency steering control is required as in the present embodiment, such control is required to improve the safety of the driver.

That is, the variable HPF161 receives an error value (i.e., a position control error) corresponding to a difference between the current steering angle and the command steering angle, determines a cutoff frequency according to the command steering angular velocity, and calculates the gain G of the gain adjustment unit 162 by multiplying the position control gain Kp (G-Kp Td) by the differential time Td.

Here, Kp represents the P gain of the PID controller.

For reference, since the differential time Td may define a control period and frequency of a D controller in the PID controller, a value of Kd is changed to control the gain G.

Here, Kd represents the D gain of the PID controller.

As already defined, the value of Kd increases when the steering angle speed is high within the transfer function, and decreases when the steering angle speed is low. Therefore, the gain response characteristic of the controller varies. Further, as described above, a specific portion (i.e., (1/Td) + s) ((1/Td) + s)) + Td × Kp × s) in the transfer function ((1/Td)/((1/Td + s)) has the same form as the HPF, and can be set to a desired frequency by 1/Td.

That is, the transfer function of a general HPF can be expressed as s/(s + w). Here, w is 2 × pi f, where f denotes the cut-off frequency.

In the transfer function, 1/Td becomes w, and the value of Td is changed to set a desired frequency.

That is, since the vehicle speed is high and external noise or tire vibration increases, the cutoff frequency may lag (or increase) when the value of the differential time Td decreases (or falls). Further, when the value of the differential time Td rises (or increases) because the vehicle speed is low, the cutoff frequency can be lowered to control a wider bandwidth. This is determined by a test considering the control stability of the MDPS, and the value of the gain G and the value of the differential time Td are stored in a tuning map (tuning map) according to the vehicle speed and the steering angular velocity.

However, when emergency steering is performed during autonomous driving, vibration or the like may be caused by factors such as the external environment. In this case, it is necessary to detect the vibration in advance to prevent the gain G from excessively increasing or the cutoff frequency vibration of the variable HPF161 from excessively increasing.

For this operation, the vibration detection unit 130 monitors in real time the frequency at which the sign of the steering angular velocity changes within a predetermined time (see fig. 2).

For example, when the sign of the steering angular velocity is changed three times in total within the count time of one second as shown in fig. 2, it can be determined that 1Hz noise occurs.

In general, since the stiffness of the torsion bar is the lowest in the MDPS system, vibration occurs most frequently at the resonance frequency of the torsion bar. The resonance frequency ranges from 8Hz to 12 Hz. For example, it can be assumed that a vibration of 8Hz occurs when the sign of the steering angular velocity changes 17 times per second. This may indicate that the gain G has increased excessively or that the cutoff frequency of the variable HPF161 has decreased excessively. Therefore, in a predetermined general autonomous driving situation, the value of the gain G or the cutoff frequency is restored to the value of the gain G or the cutoff frequency.

In order to prevent resonance of the MDPS system when the MDPS system performs position control in a normal situation during autonomous driving, the steering angle position controller 150 is designed, and the PID gain is tuned. However, when the performance of the steering angle position controller 150 is maximized to instantaneously avoid the obstacle, that is, when the gain G is instantaneously raised or the cutoff frequency of the variable HPF161 is lowered to the range of 8Hz to 12Hz, the gain may be increased according to the frequency characteristic. Therefore, the stability of the steering angle position controller 150 may be degraded to cause vibration. Typically, a torsion bar resonant frequency of 8Hz to 12Hz is not detected in MDPS systems. When the vibration detection unit 130 detects a signal of a corresponding frequency, the gain G may be lowered, or the cutoff frequency of the variable HPF161 may be restored to a level corresponding to a normal case where no vibration occurs.

In other words, when the gain G of the steering angle position controller 150 is raised to increase the instantaneous responsiveness, or the cutoff frequency is adjusted to increase the gain characteristic of the frequency requiring instantaneous steering (generally, as the cutoff frequency of the variable HPF161 is lowered, the gain level according to the frequency of 8Hz to 12Hz is increased), the safety margin of the steering angle position controller 150 is lowered. When the vibration detection unit 130 monitors the decrease in the safety margin and determines that vibration occurs, the performance of the steering angle position controller 150 is restored to a normal state.

By this operation, cancellation of autonomous driving can be prohibited in an emergency steering situation, and the performance of the steering angle position controller 150 can be maximized by the variable HPF161, so that the autonomously driven vehicle can avoid an obstacle in an emergency situation. Further, according to a general autonomous situation, the cutoff frequency of the variable HPF161, which varies due to the position control error, is restored. When vibration occurs according to the situation during emergency steering, the variable HPF 151 may be optimized to prevent side effects caused by the emergency steering.

Therefore, as shown in fig. 4 a to 4 d, the experimental results of the steering angle position controller according to the present embodiment show that, as a command steering angle, the responsiveness (blue signal) according to the input (black signal) of a step signal (e.g., a signal corresponding to urgent steering) is more improved than other existing position controllers (red, yellowish green and brown signals), as shown in fig. 4 a and 4 b. Furthermore, the experimental results show that, as the command steering angle, the responsiveness (blue signal) according to the input (black signal) (e.g., signal corresponding to general steering other than abrupt steering) of the chirp signal (e.g., signal corresponding to general steering other than urgent steering) is more improved than other existing position controllers (red, yellowish green and brown signals), as shown in fig. 4 (c) and fig. 4 (d).

In the present embodiment, when the vehicle intends to avoid an obstacle that suddenly appears during autonomous driving, the vehicle may not sufficiently cope with such a situation by merely decelerating. In this case, the emergency steering will be performed. When the emergency steering is performed, the autonomous driving may be cancelled. That is, when emergency steering is performed, signals such as high steering speed, acceleration, a non-linear steering command, and a train torque increase, which are not generated in a general autonomous driving situation, are applied to the MDPS system. When it is determined that a signal, which is not generated in a general autonomous driving situation, is applied to the MDPS system, the performance of the position controller may be instantaneously maximized, so that an emergency steering command may be rapidly and accurately performed without canceling the autonomous driving, which makes it possible to stably and urgently avoid an obstacle at a dangerous time.

Although the present disclosure has been disclosed with reference to the embodiments shown in the drawings, these embodiments are for illustrative purposes only, and it will be understood by those skilled in the art that various modifications and other equivalent embodiments may be made thereto. Therefore, the true technical scope of the present disclosure should be defined by the appended claims. Furthermore, for example, the embodiments described in this specification can be implemented in methods or processes, apparatuses, software programs, data streams, or signals. Although a function is discussed only in the context of a single implementation (e.g., only in one method), the features discussed may be implemented in another type (e.g., device or program). The apparatus may be implemented in suitable hardware, software or firmware. The method may be implemented in a device such as a processor, which generally refers to a processing device including a computer, microprocessor, integrated circuit, or programmable logic device. The processor includes a communication device, such as a computer, a cellular telephone, a PDA (personal digital Assistant), and another device, which can facilitate the communication of information between end users.

Although the 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.