KR20230045384A - Electric vehicle drift control system and method therefor - Google Patents

Abstract

Disclosed are an electric vehicle drift control system and a method thereof. By an embodiment of the present invention, the electric vehicle drift control system includes: a driving information detector detecting driving information necessary for drift control during the driving of a four-wheel drive electric vehicle; a drift mode switch inputting a drift mode signal according to an operation by a driver; a front-wheel motor and a rear-wheel motor independently transmitting a driving force to the front and rear wheels of the electric vehicle; and a controller, when the drift mode signal is inputted during driving in the general mode, entering the drift mode, and, when a turning index calculated based on the driving information exceeds a set first threshold value, determining the situation as a turning situation to initiate drift driving control while performing a control operation to distribute the driving force only to the rear wheels by using the rear-wheel motor. Therefore, the present invention can improve drivability with consistent vehicle behavior.

Description

Electric vehicle drift control system and method {ELECTRIC VEHICLE DRIFT CONTROL SYSTEM AND METHOD THEREFOR}

The present invention relates to a drift control system and method for an electric vehicle, and more particularly, to an electric vehicle drift control system and method for improving both drift performance and escape acceleration performance through torque control during turning of a four-wheel drive electric vehicle.

In general, all wheel drive (AWD) vehicles have played a role in improving acceleration performance and driving stability by maximizing the frictional force between tires and the road surface. However, these systems have the following drivability limitations for drivers who implement drift during circuit driving and require quick escape performance.

First, during turning drift, the front/rear wheel distribution torque is changed according to the driving condition of the vehicle rather than the driver's will, preventing starting or maintaining the drift. In other words, in order to maintain drift, torque must be distributed only to the rear wheels, but torque to the front and rear wheels is automatically distributed according to the vehicle condition, causing unintended vehicle behavior and confusing the driver.

Second, if the control that distributes the driving force only to the rear wheels for drift performance is executed, the acceleration performance is reduced when escaping straight after drift (turning). This is because the driver demands powerful acceleration performance, but the front wheel drive force is not utilized and only the rear wheel drive force is operated, so the acceleration force is reduced.

Matters described in this background art section are prepared to enhance understanding of the background of the invention, and may include matters that are not prior art already known to those skilled in the art to which this technique belongs.

An embodiment of the present invention provides a drift control system and method for a four-wheel drive electric vehicle that performs torque distribution control of front and rear wheels in drift driving mode and turning escape mode according to a change in turning index based on driving information when entering drift mode while driving. want to do

According to one aspect of the present invention, an electric vehicle drift control system includes a driving information detector for detecting driving information necessary for drift control while a four-wheel drive electric vehicle is running; a drift mode switch inputting a drift mode signal according to a driver's manipulation; a front wheel motor and a rear wheel motor that independently transmit driving force to the front and rear wheels of the electric vehicle; and when the drift mode signal is input while driving in the normal mode, the drift mode is entered, and when the turning index calculated based on the driving information exceeds a set first threshold, a turning situation is determined and drift driving control is started, but the rear wheel and a controller that uses a motor to control driving force to be distributed only to the rear wheels.

In addition, when the turning index calculated during the drift driving control decreases to less than the set second threshold, the controller determines that the turning escape situation after the drift is controlled, and further distributes the driving force to the front wheels through the front wheel motor during the turning escape control. It is possible to control straight driving for turning escape.

In addition, the controller may start torque distribution to control the front wheels at a maximum inclination in consideration of escape acceleration performance and acceleration linearity according to the total required torque when controlling the swing ride.

In addition, the controller may start distributing the driving force to the front wheels after a predetermined time delay in which the driver stabilizes the vehicle without immediately increasing front wheel torque upon determining that the turning escape situation is present.

Also, the driving information detector may detect driving information measured from at least one of an accelerator position sensor (APS), a vehicle speed sensor, a steering angle sensor, and a yaw rate sensor.

In addition, the controller may calculate a turning index using a gain value according to characteristics of the electric vehicle, a tire steering angle, a yaw rate, a vehicle speed, and a yaw change rate, and determine a turning driving condition of the electric vehicle using the calculated turning index.

In addition, the controller may include a first calculation unit for calculating a first turning index based on a tire steering angle change according to the vehicle speed; a second calculation unit calculating a second turning index based on a yaw rate according to the vehicle speed; A third calculation unit is included to calculate a gain value according to a characteristic change of the electric vehicle that affects the degree of turning, and the turning index can be finally derived by combining the values calculated by each calculation unit.

Meanwhile, a drift control method for a four-wheel drive electric vehicle according to an aspect of the present invention includes the steps of: a) entering a drift mode for monitoring whether to turn when a drift mode signal is input according to a driver's manipulation while driving; b) calculating a turning index of the electric vehicle by collecting driving information detected by various sensors during driving through a driving information detector in the drift mode; c) if the turning index exceeds a first threshold value set as a turning condition, starting drift driving control according to the turning condition determination and controlling driving force to be distributed only to the rear wheels; and d) distributing driving force to the front and rear wheels by starting turning escape control when the turning index calculated during the drift driving control falls below a set second threshold.

The step b) may include calculating the turning index using a gain value according to characteristics of the electric vehicle and a tire steering angle, yaw rate, vehicle speed, and yaw change rate based on the driving information.

Also, the step c) may include controlling normal torque distribution in the drift preparation mode without determining the turning situation when the turning index does not exceed the first threshold.

In addition, the step d) may include determining that the turning situation continues and maintaining the drift driving control if the turning index does not drop below a second threshold.

In addition, the step d) may include increasing the front wheel torque at a maximum torque increase slope set in the front wheel motor when the turning escape control is started.

Further, the step d) may include increasing the front wheel torque after a predetermined time delay in consideration of the behavior characteristics of the electric vehicle without immediately increasing the front wheel torque at the time of determining the turning escape control.

According to an embodiment of the present invention, during drift driving of an electric vehicle, it is possible to improve drivability with consistent vehicle behavior by outputting torque only to the rear wheels through independent motor driving.

In addition, there is an effect of providing escape acceleration performance by providing a powerful four-wheel drive output by maximally utilizing the front wheel driving force during turning escape after drift.

In addition, by determining the turning driving condition using the turning index calculated using the gain value according to the characteristics of the electric vehicle, vehicle speed, steering angle, yaw rate, and yaw change rate, the effect of supporting drift driving and turning escape that meets the driver's will there is

1 schematically shows an electric vehicle drift control system according to an embodiment of the present invention.
2 shows a change in turning index when turning during straight driving in a normal mode according to an embodiment of the present invention.
3 shows a change in turning index during drift driving control and turning escape control in drift mode according to an embodiment of the present invention.
4 is a flowchart schematically illustrating a drift control method of a four-wheel drive electric vehicle according to an embodiment of the present invention.
5 is a graph showing torque control according to driving conditions of a four-wheel drive electric vehicle according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention.

The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the present invention. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprise" and/or "comprising", when used herein, specify the presence of recited features, integers, steps, operations, components and/or components, but It will also be understood that does not exclude the presence or addition of one or more of the features, integers, steps, acts, elements, components and/or groups thereof. As used herein, the term "and/or" includes any one or all combinations of the associated listed items.

As used herein, "vehicle" means an electric vehicle unless otherwise specified, and the electric vehicle includes passenger cars, including sports utility vehicles (SUVs), buses, trucks, and various commercial vehicles. I understand.

Throughout the specification, terms such as first, second, A, B, (a), (b), etc. may be used to describe various components, but the components should not be limited by the terms. These terms are only used to distinguish the component from other components, and the nature, order, or order of the corresponding component is not limited by the term.

Throughout the specification, when a component is referred to as being 'connected' or 'connected' to another component, it may be directly connected or connected to the other component, but there may be other components in the middle. It should be understood that it may be On the other hand, when a component is referred to as 'directly connected' or 'directly connected' to another component, it should be understood that no other component exists in the middle.

Additionally, it is understood that one or more of the methods or aspects thereof below may be executed by at least one or more controllers. The term “controller” may refer to a hardware device that includes memory and a processor. The memory is configured to store program instructions and the processor is specially programmed to execute the program instructions to perform one or more processes described in more detail below. A controller, as described herein, may control the operation of units, modules, components, devices, or the like. It is also understood that the methods below may be practiced by an apparatus that includes a controller along with one or more other components, as will be appreciated by those skilled in the art.

In addition, the controller of the present disclosure may be implemented as a non-transitory computer-readable recording medium including executable program instructions executed by a processor. Examples of computer-readable recording media include ROM, RAM, compact disk ROM, magnetic tapes, floppy disks, flash drives, smart cards, and optical data storage devices. It is not limited to this. Computer-readable recording media may also be distributed throughout a computer network to store and execute program instructions in a distributed manner, such as, for example, a telematics server or a controller area network (CAN).

Now, an electric vehicle drift control system and method according to an embodiment of the present invention will be described in detail with reference to the drawings.

1 schematically shows an electric vehicle drift control system according to an embodiment of the present invention.

Referring to FIG. 1 , a drift control system 100 according to an embodiment of the present invention is applied to a four-wheel drive electric vehicle and includes a driving information detector 110, a drift mode (D/M) switch 120, and front wheels. It includes a motor 130, a rear wheel motor 140 and a controller 150.

The driving information detector 110 detects driving information necessary for drift control from sensors and controllers according to the operation of the four-wheel drive electric vehicle (hereinafter, also referred to as “vehicle” for convenience of explanation) and transmits the driving information to the controller 150.

For example, the driving information detector 110 includes an accelerator position sensor (APS) 111, a brake pedal sensor (BPS) 112, a vehicle speed sensor 113, a steering angle sensor 114, and a steering angle sensor 114. Driving information measured from at least one of the rate sensors 115 may be detected.

The D/M switch 120 transfers the drift mode input signal according to the driver's manipulation to the controller 150. The D/M switch 120 can be input with a separately configured button or paddle shift operation.

The front wheel motor 130 is driven according to a control signal applied from the controller 150 to transmit driving force to the front wheels of the electric vehicle.

The rear wheel motor 140 is driven according to the control signal applied from the controller 150 to transmit driving force to the rear wheels of the electric vehicle.

As described above, the conventional four-wheel drive internal combustion engine vehicle is a system that distributes the torque generated by driving one engine to each axle of the front and rear wheels through a central drive shaft, so during turning drift, the driving force of the front and rear wheels is affected respectively. A problem existed.

Unlike this, in the electric vehicle according to the embodiment of the present invention, individual motors 130 and 140 are mounted on the front and rear wheels, respectively, and the controller 150 is a drive system capable of fast independent control of each motor 130 and 140. Since it uses , it is possible to secure not only drift implementation but also escape acceleration performance.

In other words, it is difficult to independently control a four-wheel drive internal combustion engine vehicle because it is a system that needs to distribute driving force from one output source (engine) to the front and rear axles, but a four-wheel drive electric vehicle controls two independent output sources (motor). Because it is a system that controls the driving force, immediate control is possible for drift implementation and escape acceleration situations.

The controller 150 controls the overall operation of the drift control system 100 according to an embodiment of the present invention, and includes at least one program and data for this purpose.

2 shows a change in turning index when turning while going straight in a normal mode according to an embodiment of the present invention.

Referring to FIG. 2 , the controller 150 distributes normal set front/rear wheel torque according to driving conditions in the normal driving mode of an electric vehicle. Since this is a general driving condition before entering the drift mode, even if the turning index fluctuates depending on the steering angle, yaw rate, and vehicle speed, regardless of the turning index, the shift ratio is adjusted according to the preset distribution ratio in consideration of the driver's required torque, launch performance, and motor efficiency. /Rear wheel torque distribution is made.

The controller 150 enters the drift mode when receiving an input signal from the D/M switch 120 while driving the electric vehicle. The drift mode monitors whether driving information of an electric vehicle satisfies a turning driving condition, and may be referred to as a drift preparation mode or a turning preparation mode.

The controller 150 calculates a turning index based on the APS, BPS, vehicle speed, steering angle, and yaw rate collected as driving information, and controls torque distribution by determining the turning condition of the electric vehicle according to the turning index. .

3 shows a change in turning index during drift driving control and turning escape control in drift mode according to an embodiment of the present invention.

Referring to FIG. 3 , the drift mode according to an embodiment of the present invention can be divided into sections before drift immediately before turning, during drift during turning, and after drift in turning escape, according to driving conditions of an electric vehicle over time. Here, the turning driving conditions in the drift mode include a first threshold value for determining a drift start point in a pre-drift situation using a turning index and a second threshold value set for determining a turning escape point during drift.

When the turning index calculated based on the driving information exceeds a set first threshold, the controller 150 determines that it is a turning situation and starts drift driving control. It controls so that the driving force is distributed.

At this time, the controller 150 controls torque to be distributed only to the rear wheels in order to maintain a drift state (that is, continuously generate oversteer) while turning the electric vehicle, so that the front/rear wheels are divided according to the vehicle's driving state as in the prior art. It is possible to prevent the distribution torque from fluctuating and to ensure consistent vehicle behavior. In addition, during drift driving, the yaw rate is offset by the countersteer (steering angle), so that the turning index is maintained at a relatively constant value.

The controller 150 determines a turning escape situation after the drift when the turning index calculated based on the driving information during the drift driving control decreases to less than a set second threshold, and uses an independent front wheel motor 130 during turning escape control. By distributing more driving force to the front wheels, straight driving for turning escape is controlled. At this time, the controller 150 may start torque distribution to control the front wheels at the maximum inclination in consideration of escape acceleration performance and acceleration linearity according to the driver's requested torque.

At this time, the controller 150 does not immediately increase the front wheel torque at the time of turning and exiting, but starts distributing the front wheel torque after a certain time delay when the driver completely stabilizes the vehicle, thereby preventing unstable behavior such as jerking of the electric vehicle. It can be prevented.

In addition, it is possible to achieve escape acceleration performance by providing powerful four-wheel drive output by maximally utilizing individual front-wheel driving force and rear-wheel driving force according to the total required torque reflecting the driver's will.

Meanwhile, the controller 150 utilizes a turning index based on driving information collected in real time in order to determine a turning driving condition and a turning escape condition of the electric vehicle.

In general, the turning of a vehicle can be determined by a steering angle, yaw rate sensor, lateral acceleration sensor, etc., but this is because the response of the vehicle is different depending on the driving speed even under the same steering angle and yaw rate conditions, so the accuracy of the turning determination is reduced only by the absolute value.

In addition, using the yaw rate change rate (i.e., yaw acceleration), the turning trend can be determined more quickly.

Considering these points, the controller 150, as shown in Equation 1 below, gain values (G1, G2, G3), tire steering angle (ABS (δ _tire )), yaw rate (ABS (γ) according to the characteristics of the electric vehicle )), vehicle speed (V _veh ), and yaw change rate (ABS (dγ/dt)), the turning index (K _connering ) is calculated, and the turning driving condition of the electric vehicle is determined using this.

The controller 150 includes a first arithmetic unit 151 , a second arithmetic unit 152 , and a third arithmetic unit 153 for calculating the turning index K _connering .

The first calculation unit 151 calculates a first turning index based on a tire steering angle change according to vehicle speed.

The first calculation unit 151 calculates the first turning index by reflecting the characteristic that the degree of turning of the electric vehicle increases as the steering angle of the tire increases. A factor for vehicle speed is added to the first turning index in order to reflect the characteristic that the degree of turning varies depending on the driving vehicle speed even if the steering angle of the tire is the same.

The second calculation unit 152 calculates the second turning index based on the yaw rate according to the vehicle speed.

The second calculation unit 152 calculates the second turning index by reflecting the characteristic that the degree of turning of the electric vehicle increases as the yaw rate increases. A factor for vehicle speed is added to the second turning index to reflect the characteristic that the degree of turning varies depending on the running vehicle speed even at the same yaw rate.

The third calculation unit 153 calculates a gain value according to a change in characteristics of an electric vehicle that affects the degree of turning.

The gain value according to the change in characteristics of the electric vehicle refers to a tuning parameter according to the characteristics of the electric vehicle considering that the degree of turning may vary depending on specifications such as the center of gravity, wheel base, and stiffness of the electric vehicle even under the same driving conditions.

The controller 150 collects the first turning index, the second turning index, and the gain value according to the electric vehicle characteristic change calculated by each operation unit 151 to 153 to obtain a final turning index (K _connering ) for determining the turning driving condition. can be derived.

As such, the controller 150 performs the front and rear wheel torque distribution according to the drift driving control and turning escape control according to the change in turning index when the electric vehicle enters the drift mode while driving.

The controller 150 may be implemented as one or more processors that operate according to a set program, and the set program may be programmed to perform each step of the drift control method of a four-wheel drive electric vehicle according to an embodiment of the present invention. .

The drift control method of the four-wheel drive electric vehicle will be described in more detail with reference to the drawings below.

4 is a flowchart schematically illustrating a drift control method of a four-wheel drive electric vehicle according to an embodiment of the present invention.

5 is a graph showing torque control according to driving conditions of a four-wheel drive electric vehicle according to an embodiment of the present invention.

4 and 5, the controller 150 of the electric vehicle drift control system 100 equipped with independent motors 130 and 140 on the front and rear wheels, respectively, transfers the total required torque of the vehicle to the front wheels when driving in the normal mode after starting. and normal torque distribution to the rear wheels is controlled (S10). That is, referring to the general driving situation graph of FIG. 5 , the total required torque of the vehicle is the sum of the required torque of the front wheels and the required torque of the rear wheels.

If the drift mode signal according to the driver's will is not input (S20; No), the controller 150 continues the normal torque distribution control set in the normal mode (S30).

On the other hand, the controller 150, when a drift mode signal according to the driver's manipulation is input, enters the drift mode for monitoring whether or not to turn (S20; Yes).

When entering the drift mode, the controller 150 collects driving information detected from various types of sensors while driving through the driving information detector 110 (S40), and calculates a turning index based on the driving information (S50). At this time, the controller 150 may calculate the turning index using the gain values G1, G2, and G3 according to the characteristics of the electric vehicle and the tire steering angle, yaw rate, vehicle speed, and yaw change rate based on the driving information.

The controller 150 controls normal torque distribution in the drift preparation mode without determining that it is a turning situation if the turning index does not exceed a set first threshold in the drift mode (S60; No).

On the other hand, if the turning index exceeds the set first threshold value in the drift mode (S60; Yes), the controller 150 determines that it is a turning situation and starts drift driving control (S70). At this time, the controller 150 uses the rear wheel motor 140 to distribute the driving force only to the rear wheels according to the drift driving control. Referring to the graph of the drift driving situation in FIG. 5 , only the rear wheel required torque is generated and the front wheel torque becomes zero among the total required torque of the vehicle.

The controller 150 determines that the turning situation continues and maintains the drift driving control when the turning index does not fall below the set second threshold value during the drift driving control (S80: No).

On the other hand, the controller 150 determines that the turning index is less than the set second threshold value during the drift driving control (S80: Yes), determines the driver's will to escape turning, and initiates turning escape control to apply driving force to the front and rear wheels, respectively. Allocate (S90).

At this time, the controller 150 increases the front wheel torque at the maximum torque increase slope set in the front wheel motor 130 when determining a straight driving situation according to the driver's intention to turn and escape. However, the upward slope of the front wheel torque may be limited in consideration of shocks and hardware (H/W) performance of the front wheel motors.

In addition, the controller 150 may increase the front wheel torque after a certain time delay in consideration of vehicle characteristics (shock, jolt), etc. there is.

Thereafter, the controller 150 repeats the drift and escape control at the next turn in the drift mode state, but the drift mode may be canceled by the driver's manipulation or terminated when the ignition is turned off.

As described above, according to an embodiment of the present invention, there is an effect of improving drivability with consistent vehicle behavior by outputting only rear wheel torque through independent motor driving during drift driving of an electric vehicle.

In addition, there is an effect of providing escape acceleration performance by providing a powerful four-wheel drive output by maximally utilizing the front wheel driving force during turning escape after drift.

In addition, by determining the turning driving condition using the turning index calculated using the gain value according to the characteristics of the electric vehicle, vehicle speed, steering angle, yaw rate, and yaw change rate, the effect of supporting drift driving and turning escape that meets the driver's will there is

Embodiments of the present invention are not implemented only through the devices and/or methods described above, and may be implemented through a program for realizing functions corresponding to the configuration of the embodiments of the present invention, a recording medium on which the program is recorded, and the like. Also, such an implementation can be easily implemented by an expert in the technical field to which the present invention belongs based on the description of the above-described embodiment.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concept of the present invention defined in the following claims are also included in the scope of the present invention. that fall within the scope of the right.

100: electric vehicle torque control system 110: driving information detector
111: accelerator pedal sensor (APS) 112: brake pedal sensor (BPS)
113: vehicle speed sensor 114: steering angle sensor
115: yaw rate sensor 120: drift mode (D/M) switch
130: front wheel motor 140: rear wheel motor
150: controller 151 to 153: first to third operation unit

Claims (13)

a driving information detector for detecting driving information necessary for drift control of a four-wheel drive electric vehicle;
a drift mode switch inputting a drift mode signal according to a driver's manipulation;
a front wheel motor and a rear wheel motor that independently transmit driving force to the front and rear wheels of the electric vehicle; and
When the drift mode signal is input while driving in the normal mode, the drift mode is entered, and when the turning index calculated based on the driving information exceeds a set first threshold, a turning situation is determined and drift driving control is started, but the rear wheel motor a controller for controlling driving force to be distributed only to the rear wheels by using;
An electric vehicle drift control system comprising a. According to claim 1,
The controller
If the turning index calculated during the drift driving control decreases to less than the set second threshold, it is determined that the turning escape situation after the drift has occurred, and during the turning escape control, driving force is further distributed to the front wheels through the front wheel motor to go straight for turning escape. An electric vehicle drift control system that controls driving. According to claim 2,
The controller
An electric car drift control system that starts torque distribution to control the front wheels at a maximum inclination in consideration of escape acceleration performance and acceleration linearity according to the total required torque during the turning deactivation control. According to claim 2,
The controller
An electric vehicle drift control system that starts distributing driving force to the front wheels after a predetermined time delay in which the driver stabilizes the vehicle without immediately increasing front wheel torque when it is determined that the turning escape situation occurs. According to any one of claims 1 to 4,
The driving information detector
An electric vehicle drift control system that detects driving information measured from at least one of an accelerator pedal sensor (APS), a vehicle speed sensor, a steering angle sensor, and a yaw rate sensor. According to claim 5,
The controller
An electric vehicle drift control system that calculates a turning index using a gain value, tire steering angle, yaw rate, vehicle speed, and yaw change rate according to the characteristics of the electric vehicle and determines turning conditions of the electric vehicle using the same. According to claim 6,
The controller
a first calculation unit calculating a first turning index based on a change in tire steering angle according to the vehicle speed;
a second calculation unit calculating a second turning index based on a yaw rate according to the vehicle speed;
A third calculation unit for calculating a gain value according to a change in characteristics of the electric vehicle that affects the degree of turning,
An electric car drift control system that finally derives the turning index by collecting values calculated by each calculation unit. In the drift control method of a four-wheel drive electric vehicle,
a) entering a drift mode for monitoring whether to turn when a drift mode signal is input according to a driver's manipulation while driving;
b) calculating a turning index of the electric vehicle by collecting driving information detected by various sensors during driving through a driving information detector in the drift mode;
c) if the turning index exceeds a first threshold value set as a turning condition, starting drift driving control according to the turning condition determination and controlling driving force to be distributed only to the rear wheels; and
d) distributing driving force to front and rear wheels by starting turning escape control when the turning index calculated during the drift driving control falls below a set second threshold;
Drift control method of an electric vehicle comprising a. According to claim 8,
In step b),
and calculating the turning index using a gain value according to characteristics of the electric vehicle and a tire steering angle, yaw rate, vehicle speed, and yaw change rate based on the driving information. According to claim 8,
In step c),
and controlling normal torque distribution in a drift preparation mode without determining the turning situation when the turning index does not exceed a first threshold. According to claim 8,
In step d),
and determining that the turning situation continues and maintaining the drift driving control when the turning index does not fall below a second threshold. According to claim 8,
In step d),
The method of controlling drift of an electric vehicle comprising the step of increasing front wheel torque with a maximum torque increase gradient set in a front wheel motor when the turning escape control is started. The method of claim 8 or 12,
In step d),
The drift control method comprising increasing front wheel torque after a predetermined time delay in consideration of the behavior characteristics of the electric vehicle without immediately increasing the front wheel torque at the time of determining the turning escape control.

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