KR20110080758A - Steering control method of active front steering system - Google Patents

Steering control method of active front steering system Download PDF

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Publication number
KR20110080758A
KR20110080758A KR1020100001143A KR20100001143A KR20110080758A KR 20110080758 A KR20110080758 A KR 20110080758A KR 1020100001143 A KR1020100001143 A KR 1020100001143A KR 20100001143 A KR20100001143 A KR 20100001143A KR 20110080758 A KR20110080758 A KR 20110080758A
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South Korea
Prior art keywords
steering
gear ratio
vehicle
steering gear
steering angle
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KR1020100001143A
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Korean (ko)
Inventor
제성규
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현대모비스 주식회사
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Priority to KR1020100001143A priority Critical patent/KR20110080758A/en
Publication of KR20110080758A publication Critical patent/KR20110080758A/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W10/00—Conjoint control of vehicle sub-units of different type or different function
    • B60W10/20—Conjoint control of vehicle sub-units of different type or different function including control of steering systems
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D6/00—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Steering Control In Accordance With Driving Conditions (AREA)

Abstract

The present invention relates to a steering control method of an active front wheel steering system that tunes a steering gear ratio according to a change in a driving mode and a steering angle according to a vehicle speed in an active current steering (hereinafter referred to as 'AFS') system.
The steering control method of the active front wheel steering system of the present invention is to set a steering gear ratio according to the vehicle speed and steering angle of a vehicle and output a control signal, and to drive a motor and a steering variable mechanism according to the control signal output from the ECU. In an active front wheel steering system including a driving circuit unit, the ECU stores a steering gear ratio table for each driving mode and steering angle, and the ECU controls the vehicle speed and the steering angle of the vehicle when the amount of change in the steering angle exceeds a threshold. A second step of applying a steering gear ratio table to detect a steering gear ratio according to the vehicle speed and steering angle of the vehicle and varying the steering gear ratio of the vehicle to the detected steering gear ratio; If not, the third step of fixing the steering gear ratio of the vehicle.

Description

Steering control method of active front wheel steering system {STEERING CONTROL METHOD OF ACTIVE FRONT STEERING SYSTEM}

The present invention relates to a steering control method of an active current steering (hereinafter referred to as 'AFS') system, and more particularly, an active front wheel for tuning a steering gear ratio according to a change in a driving mode and a steering angle according to a vehicle speed. The present invention relates to a steering control method of a steering system.

In general, a steering system is applied to a vehicle by using an electronic control unit (hereinafter referred to as "ECU") to reduce the driving force of the driver's steering wheel according to the speed of the vehicle to enable light and quick steering operation. The vehicle equipped with the steering system includes a steering gear ratio variable mechanism between the driver handle and the steering actuator, and by varying the output angle to the steering input of the driver's steering wheel through the operation of the steering gear ratio variable mechanism, the vehicle's behavior is improved. An AFS system is applied to make it more stable.

1 is a block diagram of a general AFS system, including a vehicle speed sensor 1 for detecting a vehicle speed, a steering angle sensor 2 for detecting a steering angle of a vehicle steering wheel, and a lateral acceleration sensor for detecting a lateral acceleration of a vehicle (3), the yaw rate sensor 4 for detecting the yaw rate of the vehicle, the vehicle speed sensor 1, the steering angle sensor (2), the lateral acceleration sensor (3), the yaw rate sensor (4) An ECU 5 which receives the detected vehicle speed, steering angle, lateral acceleration, and yaw rate vehicle state information, calculates and sets an appropriate steering gear ratio for the vehicle state, and outputs a control signal according to the set steering gear ratio; A driving circuit section 6 for outputting a driving signal for driving a motor and a steering variable mechanism in accordance with a control signal output from the ECU 5, and between the driver's handle and the steering actuator, and the driving circuit section 6 According to the driving signal output from It is configured to include a motor and a steering variable mechanism (7) which is driven to receive the steering angle of the handle to vary the rotation angle to give a variable rotation angle to the steering actuator as an output value.

This AFS system sets the fast steering gear ratio at low speeds and the slow steering gear ratio at high speeds, resulting in agile steering characteristics at low speeds, significantly reducing the driver's workload in parking situations and steering sensitivity at high speeds. Is reduced, enabling stable steering operation.

In addition, since the steering gear ratio is varied according to the position of the steering angle, the on-center (lower) steering gear ratio is set in the on-center, and the faster steering gear ratio is set toward the off-center (emergency, such as steep steering of the vehicle). This adds to the agility of the vehicle due to the fast steering gear ratio. The AFS system calculates an appropriate steering gear ratio by inputting a vehicle speed and a steering angle to determine a ratio between an input angle of a steering wheel and an output angle transmitted to a tire by a planetary gear or a link structure.

However, in this AFS system, when the deceleration or acceleration occurs due to the speed change of the vehicle, the steering gear ratio is changed irrespective of the driver's intention.In this case, if there is a steering input, the oversteer or oversteer Understeer occurs and the vehicle's behavior may be out of the trajectory or in an unstable state, thereby providing a sense of heterogeneity to the driver.

In order to solve this problem, Korean Patent Application No. 2005-0118794 has been filed and disclosed.

2 is an operational flow diagram illustrating the operation of the prior art.

When the AFS system applied to the steering system is operated, the respective vehicle state information detecting sensors, that is, the vehicle speed sensor 1, the steering angle sensor 2, the lateral acceleration sensor 3, and the yaw rate sensor 4 are respectively vehicle speeds. (V), steering angle (θ), lateral acceleration and yaw rate of the vehicle steering wheel are detected, respectively. Subsequently, the ECU 5 receives the vehicle speed V and the steering angle θ detected by the vehicle speed sensor 1 and the steering angle sensor 2 (S1), and performs proper steering on the vehicle state through a check-up table. The gear ratio G is calculated and set (S2).

In addition, the ECU 5 determines whether the steering angle θ detected by the steering angle sensor 2 is out of a neutral range of a predetermined range (S3), and if the vehicle is out of a neutral range of a predetermined range with a predetermined steering angle applied thereto. The acceleration a of the vehicle is calculated using the vehicle speed V input from the sensor 1 (S4).

At this time, as a result of the determination in step S3, it is determined to change the steering gear ratio G if the steering angle θ does not deviate from the neutral of a predetermined range (S7). That is, the steering gear ratio G set in step S2 is determined as the variable steering gear ratio, and a control signal corresponding to the determined steering gear ratio is output to the driving circuit unit 6.

Then, the drive circuit unit 6 outputs a drive signal for driving the motor and the steering variable mechanism 7 according to the control signal output from the ECU 5, and accordingly the motor provided between the driver's handle and the steering actuator. And the steering variable mechanism 7 is driven in accordance with the drive signal output from the driving circuit unit 6 to vary the steering gear ratio (S8).

On the other hand, as a result of the determination in step S3, after calculating the acceleration a of the vehicle with the steering angle θ being out of a neutral range of a certain range, the speed change amount of the vehicle using the absolute value of the acceleration a is a reference value ( δ) or less (S5), and if the speed change amount of the vehicle is equal to or less than the reference value (δ), it is determined whether the change amount of the steering angle θ is less than or equal to the reference value α by using the absolute value of the steering angle θ (S6). ).

As a result of the determination in step S5, if the speed change amount of the vehicle is not equal to or less than the reference value δ, that is, if the deceleration or acceleration of the vehicle speed occurs, the steering gear ratio G set in step S2 is determined as the variable steering gear ratio and the steering gear ratio is determined. It is determined not to vary, but to have the current fixed steering gear ratio as it is (S9), and outputs a control signal according to the fixed steering gear ratio thus determined to the driving circuit unit 6.

Further, as a result of the determination in step S6, if the amount of change in the steering angle θ is not equal to or less than the reference value α, it is determined to have the current fixed steering gear ratio as it is (S9). Similarly, the control signal according to the fixed steering gear ratio is driven. Output to the circuit part 6 is carried out.

Then, the driving circuit unit 6 outputs a driving signal for driving the motor and the steering variable mechanism 7 in accordance with the control signal output from the ECU 5, at which time the output of the driving signal does not change the steering gear ratio. The motor and the steering variable mechanism 7 are driven so that the steering gear ratio does not change and remains fixed at the instant. Therefore, the unstable state of the vehicle, such as the conventional oversteer or understeer, does not occur, and the heterogeneity is eliminated during steering, and the driver can safely drive while maintaining a constant steering angle even during deceleration of the vehicle.

However, the above-described prior art suffers from a failure to fix the number of revolutions of the steering (the normal steering has a rotation angle of -520 to +520 degrees). For example, if the vehicle speed is 10km and the steering wheel is turned to the left, the gear ratio is low, so it becomes Fulton at about 300 degrees, but when the vehicle is rapidly accelerated to about 50km, the gear ratio is increased, and the gear ratio is increased to turn to the right. can not do it. Therefore, the driver feels heterogeneity because the driver has to turn more to the right turn than the steering wheel turned to the left turn in order to drive straight, and there is a problem that the vehicle driving becomes unstable.

That is, the existing AFS system provides a non-constant amount of rotation of the steering wheel due to the change in the gear ratio with the vehicle speed. Accordingly, if the vehicle speed changes rapidly, the driver feels heterogeneity due to the application of different gear ratios during the left turn and right turn, and the system is unstable. And, the total number of rotations of the right turn in the left turn of the steering wheel is a full turn in about one and a half wheels when the gear ratio is low, but when the gear ratio is high, the full turn is about four wheels. Therefore, there is a problem that the safe driving of the driver is disturbed due to such an inconsistent gear ratio change.

An object of the present invention devised to solve the problems of the prior art, the steering of the active front wheel steering system to enable precise and safe AFS control by selecting the driving mode for each vehicle speed and varying the gear ratio according to the steering angle for each mode To provide a control method.

In addition, another object of the present invention is to provide a steering control method of an active front wheel steering system that minimizes the heterogeneity felt by the driver in the low speed driving mode or the high speed driving mode by limiting the number of revolutions of the total steering wheel.

Steering control method of the active front wheel steering system according to the present invention for achieving the above object, according to the ECU for setting the steering gear ratio according to the vehicle speed and steering angle of the vehicle and outputs a control signal, according to the control signal output from the ECU A steering control method for an active front wheel steering system including a driving circuit unit for driving a motor and a steering variable mechanism, wherein the ECU stores a steering gear ratio table for each driving mode and each steering angle, and the ECU changes the amount of change in the steering angle. A second step of applying a vehicle speed and a steering angle of the vehicle to the steering gear ratio table to detect a steering gear ratio according to the vehicle speed and a steering angle of the vehicle and varying the steering gear ratio of the vehicle to the detected steering gear ratio if the threshold value is exceeded; When the amount of change in the steering angle does not exceed a threshold, the steering gear ratio of the vehicle; Characterized by including a third step of fixing.

As described above, according to the present invention, the gear ratio is variable according to the driving mode for each vehicle speed and the steering angle for each driving mode to enable precise and safe AFS control, and the heterogeneity felt by the driver is minimized by limiting the number of revolutions of the steering wheel. Has the effect of helping to drive safely.

In addition, in low-speed parking, the gear ratio is improved by lowering the gear ratio in the range where the initial steering wheel angle is small, and in high-speed driving, the gear ratio is increased by increasing the gear ratio in the small range of the steering wheel angle. Has the effect of providing.

In addition, by not adding a separate mechanical hardware device to limit the number of revolutions of the steering wheel, the process is simple, the number of parts is reduced, light weight, and there is an effect of reducing the feel.

1 is a block diagram of a general AFS system,
2 is an operation flowchart showing the operation of the prior art described in Korean Patent Application No. 2005-0118794,
3 is a flowchart illustrating a steering control method of an active front wheel steering (AFS) system according to an embodiment of the present invention.

Hereinafter, a steering control method of an active front wheel steering (AFS) system according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

The AFS system receives vehicle information (vehicle speed, steering angle, yaw rate, etc.) to vary the steering gear ratio. The present invention receives the vehicle speed and steering angle which have the most influence on the gear ratio change of the AFS system from each sensor, calculates the change of the steering angle, and when the steering angle change exceeds the threshold (when the driver gives steering input), the vehicle speed and The driving gear ratio is varied for each driving mode tuned to the steering angle.

The steering control method according to the present invention is applied to the AFS system shown in FIG.

As shown in FIG. 1, the AFS system includes a vehicle speed sensor 1 for detecting a vehicle speed, a steering angle sensor 2 for detecting a steering angle of a vehicle steering wheel, and a lateral acceleration sensor 3 for detecting a lateral acceleration of the vehicle. ), The yaw rate sensor 4 for detecting the yaw rate of the vehicle, the vehicle speed sensor 1, the steering angle sensor 2, the lateral acceleration sensor 3, and the yaw rate sensor 4. An ECU 5 which receives vehicle state information of each vehicle speed, steering angle, lateral acceleration, and yaw rate, calculates and sets an appropriate steering gear ratio for the vehicle state, and outputs a control signal according to the set steering gear ratio; A driving circuit portion 6 for outputting a driving signal for driving the motor and the steering variable mechanism in accordance with the control signal output from (5), and between the driver's handle and the steering actuator, and outputting from the driving circuit portion 6 Driven according to the driving signal Receiving the variable of the steering angle by the angle of rotation is configured to include a motor and a variable steering mechanism 7 to take the rotation angle to the steering actuator with variable output.

The ECU 5 presets the steering gear ratio according to the steering angle for each driving mode according to the vehicle speed of the vehicle and stores it in a table.

For example, the steering gear ratio table for each driving mode and steering angle according to the vehicle speed stored in the ECU 5 is shown in Table 1 below.

mode Steering angle Steering Gear Ratio Mode 0
0-20 km / h 0 to ± 90 10: 01 ± 90 to ± 180 10: 01 ± 180 to ± 270 16: 01 ± 270 to ± 360 16: 01 ± 360 to ± 450 22: 01 ± 450 to ± 540 22: 01 Mode 1
20 ~ 80 km / h 0 to ± 60 16: 01 ± 60 to ± 180 10: 01 ± 180 to ± 270 10: 01 ± 270 to ± 330 16: 01 ± 330 to ± 450 22: 01 ± 450 to ± 540 22: 01 Mode 2
80 ~ max 0 to ± 60 19: 01 ± 60 to ± 180 13: 01 ± 180 to ± 270 16: 01 ± 270 to ± 360 16: 01 ± 360 to ± 450 16: 01 ± 450 to ± 540 16: 01

The steering gear ratio table for each driving mode and steering angle according to the vehicle speed is divided into driving modes (mode 0, mode 1 and mode 2) by vehicle speed, which can be tuned by a developer. The low steering gear ratio and the high steering gear ratio are appropriately distributed for each mode, so that the average value of the steering gear ratio for each driving mode is always 16: 1 (basic steering gear ratio of the steering wheel). This is to maintain a constant rotation speed of the steering wheel so that the driver does not feel heterogeneous when steering. The steering gear ratio for each steering angle is differently tuned for each driving mode according to the vehicle speed.

In the low speed mode (mode 0), the driving environment is parking or exiting a narrow road. Therefore, the steering gear ratio at the 0 to 180 degree steering angle is tuned low so that the vehicle can be easily driven.

In medium speed mode (mode 1), driving on a normal road, and there may be driving, such as lane change, maintain the normal gear ratio in the on-center (0 to 60 degrees) section and apply a low steering gear ratio in the steering angle section between 60 and 270 degrees. Thereby providing convenience of driving.

In the high speed mode (mode 2), the vehicle is determined to be driving at a high speed (high speed driving), so the steering gear ratio of the on-center (0 to 60 degrees) is further lowered for vehicle stability, and 60 to 120 degrees is the same as a lane change. Set the steering gear ratio high to make the movement agile.

3 is a flowchart illustrating a steering control method of an active front wheel steering (AFS) system according to an embodiment of the present invention.

When the AFS system applied to the steering system is operated, the respective vehicle state information detecting sensors, that is, the vehicle speed sensor 1, the steering angle sensor 2, the lateral acceleration sensor 3, and the yaw rate sensor 4 are respectively vehicle speeds. (V), steering angle (θ), lateral acceleration and yaw rate of the vehicle steering wheel are detected, respectively.

Subsequently, the ECU 5 receives the vehicle speed V and the steering angle θ detected by the vehicle speed sensor 1 and the steering angle sensor 2 (S31), and determines whether the amount of change in the steering angle exceeds a threshold (S32). .

As a result of the determination in step S32, when the amount of change in the steering angle exceeds the threshold, the vehicle speed and the steering angle are applied to the steering gear ratio table as shown in Table 1, and the driving mode according to the vehicle speed is selected (S33), and the corresponding driving is performed using the table for each driving mode. In operation S34, the steering gear ratio corresponding to the steering angle is detected.

In addition, the ECU 5 outputs a control signal according to the detected steering gear ratio to the drive circuit section 6 in order to vary the steering gear ratio of the steering wheel of the vehicle to the steering gear ratio detected in step S34.

Then, the drive circuit unit 6 outputs a drive signal for driving the motor and the steering variable mechanism 7 according to the control signal output from the ECU 5, and accordingly the motor provided between the driver's handle and the steering actuator. And the steering variable mechanism 7 is driven according to the drive signal output from the driving circuit section 6 to vary the steering gear ratio.

On the other hand, as a result of the determination in step S32, if the amount of change in the steering angle does not exceed the threshold, it is determined not to change the steering gear ratio but to fix the current steering gear ratio and output a control signal according to the determined steering gear ratio to the driving circuit unit 6. (S36).

In the present invention, the steering gear ratio is set individually according to the angle of the steering wheel for each driving mode, but the steering gear ratio change according to the steering angle of the left turn and the right turn is the same in order to eliminate heterogeneity and instability while the driver is driving. In order to prevent the steering wheel ratio from changing due to the variable steering gear ratio, the steering gear ratio of the steering wheel is always 16: 1, which is the same as the steering gear ratio of the general steering wheel. In other words, the steering wheel is -580 to 580 degrees from the left Fulton to the right Fulton. While the steering angle goes from 0 to 580, the ratio of the low steering gear ratio to the high steering gear ratio is equal, so that the average steering gear ratio is always constant.

Vehicle speed sensor: 1 Steering angle sensor: 2
Lateral acceleration sensor; 3 yaw rate sensor: 4
ECU: 5 drive circuit sections: 6

Claims (2)

A steering control method of an active front wheel steering system including an ECU that sets a steering gear ratio according to a vehicle speed and a steering angle of a vehicle and outputs a control signal, and a driving circuit that drives a motor and a steering variable mechanism according to the control signal output from the ECU. In
The ECU includes a first step of storing a steering gear ratio table for each driving mode and steering angle;
The ECU detects a steering gear ratio according to the vehicle speed and the steering angle of the vehicle by applying the vehicle speed and the steering angle of the vehicle to the steering gear ratio table when the amount of change in the steering angle exceeds a threshold, and determines the steering gear ratio of the vehicle to the detected steering gear ratio. The second step is variable to
And said ECU comprises a third step of fixing a steering gear ratio of said vehicle if the amount of change of said steering angle does not exceed a threshold. 2. The steering control method according to claim 1, wherein the average value of the steering gear ratio for each steering angle in each driving mode is a basic steering gear ratio of a steering wheel.
KR1020100001143A 2010-01-07 2010-01-07 Steering control method of active front steering system KR20110080758A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101327116B1 (en) * 2011-11-21 2013-11-07 현대자동차주식회사 Mdps control method with learning of driving pattern
KR101526796B1 (en) * 2014-04-01 2015-06-05 현대자동차주식회사 Catch-up protection method of active front steering and an apparatus thereof
CN111114624A (en) * 2018-10-30 2020-05-08 丰田自动车株式会社 Steering system and control method for steering system

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101327116B1 (en) * 2011-11-21 2013-11-07 현대자동차주식회사 Mdps control method with learning of driving pattern
KR101526796B1 (en) * 2014-04-01 2015-06-05 현대자동차주식회사 Catch-up protection method of active front steering and an apparatus thereof
CN111114624A (en) * 2018-10-30 2020-05-08 丰田自动车株式会社 Steering system and control method for steering system

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