JPWO2013098996A1 - Vehicle driving support device - Google Patents

Abstract

The present invention relies on a device for detecting a succeeding vehicle traveling behind the host vehicle in a vehicle driving support device that changes the route of the host vehicle when a three-dimensional object is present on the track of the host vehicle. However, it is an object of the present invention to provide a technique capable of avoiding a situation in which the host vehicle enters the path of the following vehicle by changing the route of the host vehicle. In order to solve this problem, according to the present invention, when a lane marking indicating a boundary of a lane is not detected on the road between the host vehicle and the three-dimensional object, the course change of the host vehicle is prohibited.

Description

  The present invention relates to a technique for implementing driving assistance for avoiding an obstacle present on a vehicle path.

  There has been proposed a technique for changing the course of the host vehicle when it is determined that the host vehicle cannot complete deceleration without coming into contact with an obstacle (see, for example, Patent Document 1). According to such a technique, it is possible to avoid contact between the host vehicle and an obstacle. However, if there is a subsequent vehicle on the rear side (obliquely behind) of the host vehicle, the host vehicle is changed by changing the course of the host vehicle. There is a possibility of entering the path of the following vehicle.

  On the other hand, in the steering control device that changes the traveling lane of the own vehicle in order to avoid contact between the own vehicle and the preceding vehicle, a succeeding vehicle traveling in the lane to be changed is detected, and the succeeding vehicle There is also proposed a technique for prohibiting the change of the traveling lane when there is a possibility that the vehicle contacts with the vehicle (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 2001-247023 JP 2009-280015 A

  By the way, according to the technique described in Patent Document 2 described above, an apparatus for detecting a succeeding vehicle existing behind the host vehicle is required, resulting in an increase in the number of parts and an increase in manufacturing cost. There is a problem.

  The present invention has been made in view of the above circumstances, and its purpose is to change the course of the host vehicle in order to avoid contact between the three-dimensional object existing on the course of the host vehicle and the host vehicle. In the driving support device, it is possible to avoid a situation where the own vehicle enters the course of the succeeding vehicle by changing the course of the own vehicle without depending on the device that detects the following vehicle existing behind the own vehicle. The provision of technology.

  In order to solve the above-described problems, the present invention provides a driving support device for changing the course of a host vehicle in order to avoid contact between the host object and a three-dimensional object existing on the course of the host vehicle. When there is no lane marking that shows the lane boundary on the road between the vehicle and the vehicle, changing the course of the vehicle is prohibited.

Specifically, the driving support device for a vehicle according to the present invention includes:
In a vehicle driving support device for changing the course of the host vehicle when a three-dimensional object is present on the course of the host vehicle,
Detecting means for detecting a lane marking on the road indicating a lane boundary;
When a lane marking indicating a lane boundary is not detected on the road between the host vehicle and the three-dimensional object, a prohibition unit that prohibits a change of course of the host vehicle,
I was prepared to.

  If there is no lane marking (for example, a white line or a yellow line) indicating the boundary of the lane on the road between the three-dimensional object and the own vehicle on the course of the own vehicle, the three-dimensional object is driven by the own vehicle. May be in the lane. Therefore, if the course of the host vehicle is changed in order to avoid contact between the host vehicle and the three-dimensional object, the host vehicle may depart from the travel lane and enter another lane. If there is a traveling vehicle in another lane, especially if the following vehicle is traveling in another lane on the rear side (obliquely behind) of the own vehicle, There is a possibility of causing contact between the vehicle and the following vehicle.

  On the other hand, the vehicle driving support apparatus according to the present invention does not detect a lane marking indicating a lane boundary on a road between a three-dimensional object existing on the course of the own vehicle and the own vehicle (three-dimensional object). Is likely to exist in the travel lane of the host vehicle), the course change of the host vehicle is prohibited. In this case, it is prohibited for the own vehicle to depart from the travel lane and enter another lane (so-called lane change). As a result, it is possible to avoid a situation where the own vehicle enters the course of the following vehicle due to the course change of the own vehicle.

  Therefore, according to the present invention, it is possible to avoid contact between the following vehicle and the own vehicle due to a change in the course of the own vehicle without depending on a device for detecting the following vehicle existing behind the own vehicle. Can do.

  The driving support apparatus for a vehicle according to the present invention may further include a deceleration unit that decelerates the host vehicle when the course change of the host vehicle is prohibited by the prohibiting unit. According to such a configuration, when changing the course of the host vehicle is prohibited, the host vehicle is decelerated to prevent contact with the three-dimensional object, or to reduce the impact when the host vehicle contacts the three-dimensional object. be able to.

  Here, as a method for the deceleration means to decelerate the host vehicle, for example, a method of operating a friction brake for converting the rotational energy of the wheel into heat energy, or a method of converting (regenerating) the rotational energy of the wheel into electric energy. Alternatively, a method of increasing the engine brake by changing the transmission gear ratio can be used.

  Further, the vehicle driving support apparatus according to the present invention prevents the own vehicle from deviating from the lane boundary when a lane marking indicating the lane boundary is detected on the road between the own vehicle and the three-dimensional object. The vehicle may further include changing means for changing the course of the host vehicle.

  If a lane marking indicating a lane boundary is detected on the road between the vehicle and the three-dimensional object existing on the path of the host vehicle, the three-dimensional object exists outside the traveling lane of the host vehicle. . In such a case, if the course is changed so that the own vehicle does not deviate from the boundary of the lane, the own vehicle stays in the traveling lane, so that the own vehicle is on the course of the following vehicle traveling in another lane. While avoiding the situation of entering, contact with a three-dimensional object can also be avoided.

  Here, as a method for the changing means to change the course of the host vehicle, a method of changing the steering angle of the wheel, a method of applying different braking forces to the front, rear, left and right wheels of the host vehicle (for example, front, rear, left and right wheels) And the like, a method of applying different hydraulic pressures (brake hydraulic pressures) to the friction brakes attached to each of them.

  According to the present invention, in a driving support device that changes the course of the host vehicle in order to avoid contact between the three-dimensional object existing on the course of the host vehicle and the host vehicle, the following vehicle that exists on the rear side of the host vehicle. It is possible to avoid a situation in which the host vehicle enters the path of the following vehicle by changing the course of the host vehicle without depending on the device that detects the vehicle.

It is a figure which shows the structure of the driving assistance system of the vehicle concerning this invention. It is a figure which shows the 1st example in which the lane marking which shows the boundary of a lane does not exist on the road between the own vehicle and an obstruction. It is a figure which shows the 2nd example in which the lane marking which shows the boundary of a lane does not exist on the road between the own vehicle and an obstruction. It is a figure which shows the 1st example in which the driving assistance accompanying a course change is implemented when the lane marking which shows the boundary of a lane does not exist on the road between the own vehicle and an obstruction. It is a figure which shows the 2nd example in which the driving assistance accompanying a course change is implemented when the lane marking which shows the boundary of a lane does not exist on the road between the own vehicle and an obstruction. It is a figure which shows the 1st example in which the lane marking which shows the boundary of a lane exists on the road between the own vehicle and an obstruction. It is a figure which shows the 2nd example in which the lane marking which shows the boundary of a lane exists on the road between the own vehicle and an obstruction. It is a figure which shows the 1st example in which the driving assistance accompanying a course change is implemented when the lane marking which shows the boundary of a lane exists on the road between the own vehicle and an obstruction. It is a figure which shows the 2nd example in which the driving assistance accompanying a course change is implemented when the lane marking which shows the boundary of a lane exists on the road between the own vehicle and an obstruction. It is a flowchart which shows the process routine performed when ECU implements driving assistance.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. Here, an example will be described in which the present invention is applied to a system that determines a running path or an obstacle of the host vehicle and performs support for avoiding deviation from the determined running path or contact with the obstacle. Note that “support” here is a process executed when the host vehicle can avoid a three-dimensional object that is an obstacle, and a contact damage reduction process that is executed when contact between the vehicle and the obstacle is unavoidable. Performed earlier. Moreover, the structure demonstrated in the following example shows one embodiment of this invention, and does not limit the structure of this invention.

  FIG. 1 is a block diagram showing the configuration of a vehicle driving support system to which the present invention is applied according to function. As shown in FIG. 1, a driving support control unit (ECU) 1 is mounted on the vehicle. The ECU 1 is an electronic control unit that includes a CPU, a ROM, a RAM, a backup RAM, an I / O interface, and the like. The ECU 1 is electrically connected with various sensors such as an external recognition device 2, a yaw rate sensor 3, a wheel speed sensor 4, an acceleration sensor 5, a brake sensor 6, an accelerator sensor 7, a rudder angle sensor 8, and a steering torque sensor 9. The output signals of these sensors are input to the ECU 1.

  The external environment recognition device 2 includes at least a stereo camera among measuring devices such as LIDAR (Laser Imaging Detection And Ranging), LRF (Laser Range Finder), millimeter wave radar, stereo camera, and the like. Information (for example, relative distance and relative angle) related to the relative position to the host vehicle, image information of road markings existing on the road ahead of the vehicle, and the like are output.

  The yaw rate sensor 3 is attached to the body of the host vehicle, for example, and outputs an electrical signal correlated with the yaw rate acting on the host vehicle. The wheel speed sensor 4 is a sensor that is attached to the wheel of the host vehicle and outputs an electrical signal that correlates with the traveling speed (vehicle speed) of the vehicle. The acceleration sensor 5 outputs an electrical signal correlated with acceleration acting in the front-rear direction of the host vehicle (longitudinal acceleration) and acceleration acting in the left-right direction of the host vehicle (lateral acceleration).

  The brake sensor 6 is attached to, for example, a brake pedal in the passenger compartment, and outputs an electrical signal that correlates with an operation torque (depression force) of the brake pedal. The accelerator sensor 7 is attached to, for example, an accelerator pedal in the passenger compartment, and outputs an electrical signal that correlates with the operation torque (depression force) of the accelerator pedal. The steering angle sensor 8 is attached to, for example, a steering rod connected to a steering wheel in the vehicle interior, and outputs an electrical signal correlated with a rotation angle (steering angle) from the neutral position of the steering wheel. The steering torque sensor 9 is attached to the steering rod and outputs an electrical signal correlated with torque (steering torque) input to the steering wheel.

  The ECU 1 is connected to various devices such as a buzzer 10, a display device 11, an electric power steering (EPS) 12, and an electronically controlled brake (ECB) 13 so that these various devices are electrically controlled by the ECU 1. It has become.

  The buzzer 10 is, for example, a device that is attached to a vehicle interior and outputs a warning sound. The display device 11 is, for example, a device that is installed in the passenger compartment and displays various messages and warning lights. The electric power steering (EPS) 12 is a device that assists the steering torque of the steering wheel by using the torque generated by the electric motor. The electronically controlled brake (ECB) 13 is a device that electrically adjusts the operating hydraulic pressure (brake hydraulic pressure) of a friction brake provided on each wheel.

  The ECU 1 has the following functions in order to control various devices using the output signals of the various sensors described above. That is, the ECU 1 includes a travel path recognition unit 100, a course prediction unit 101, a support determination unit 102, an alarm determination unit 103, a control determination unit 104, and a control amount calculation unit 105.

  The travel path recognition unit 100 generates information on a road (running path) on which the host vehicle will travel based on information output from the external environment recognition device 2. For example, the runway recognition unit 100 is a three-dimensional object that can be an obstacle of the host vehicle in the coordinate system with the host vehicle as the origin, or a lane marking that indicates the boundary of the lane in which the host vehicle is traveling (for example, a white line or a yellow line). Etc.) and the position of the vehicle (distance, yaw angle, etc.) with respect to the three-dimensional object or lane marking. The “three-dimensional object” here is not limited to a stationary object but may be a moving object. The travel path recognition unit 100 corresponds to detection means according to the present invention.

  The course prediction unit 101 specifies a route (course) that the host vehicle is predicted to pass in the coordinate system generated by the road recognition unit 100. Specifically, the course prediction unit 101 acquires the current lateral acceleration of the host vehicle from the output signal of the acceleration sensor 5, and is predicted to pass when the host vehicle travels while maintaining the current lateral acceleration. Is identified.

  The support determination unit 102 determines whether to perform driving support based on the information generated by the road recognition unit 100 and the route predicted by the route prediction unit 101. Specifically, the support determination unit 102 permits the driving support to be performed when there is a three-dimensional object that can be an obstacle on the route of the host vehicle.

  The warning determination unit 103 warns the driver by sounding the buzzer 10 or displaying a warning message or warning light by the display device 11 when the driving determination is permitted by the support determination unit 102. Prompt.

  For example, the warning determination unit 103 may cause the buzzer 10 to sound immediately when the support determination unit 102 permits the driving support, or may display a warning message or a warning light on the display device 11.

  The alarm determination unit 103 may sound the buzzer 10 when the distance between the host vehicle and the three-dimensional object is equal to or less than a predetermined distance, or may display a warning message or a warning lamp on the display device 11.

  The alarm determination unit 103 calculates the time until the host vehicle reaches the three-dimensional object, and sounds the buzzer 10 when the calculation result becomes equal to or less than a predetermined time, or displays a warning message or warning light on the display device 11. You may make it display.

  The predetermined distance and the predetermined time described above may be changed according to the output signal of the yaw rate sensor 3 or the output signal of the wheel speed sensor 4. For example, the predetermined distance and the predetermined time may be set longer when the vehicle speed is high than when the vehicle speed is low. Further, when the yaw rate is large, the predetermined distance and the predetermined time may be set longer than when the yaw rate is small.

  Note that the warning method for the driver is not limited to a method for sounding the buzzer 10 or a method for displaying a warning message or a warning light on the display device 11. For example, a method for intermittently changing the tightening torque of the seat belt. It may be adopted.

  When the support determination unit 102 permits the execution of driving support, the control determination unit 104 uses an electric power steering (EPS) 12 or an electronically controlled brake (in order to avoid contact between the host vehicle and the three-dimensional object. The timing for operating the ECB) 13 is determined.

  Specifically, the control determination unit 104 may operate the electric power steering (EPS) 12 or the electronically controlled brake (ECB) 13 when the distance between the host vehicle and the three-dimensional object is equal to or less than a predetermined distance. . In addition, the control determination unit 104 calculates the time for the host vehicle to reach the three-dimensional object, and when the calculation result becomes a predetermined time or less, the electric power steering (EPS) 12 and the electronically controlled brake (ECB) 13 are operated. It may be activated.

  The predetermined distance and the predetermined time used by the control determination unit 104 may be changed according to the vehicle speed and the yaw rate in the same manner as the predetermined distance and the predetermined time used by the alarm determination unit 103. It is assumed that it is set to be equal to or less than a predetermined distance and a predetermined time.

  The control amount calculation unit 105 is configured to operate the electric power steering (EPS) 12 and the electronic control type when the control determination unit 104 determines the operation timing of the electric power steering (EPS) 12 and the electronic control type brake (ECB) 13. The control amount of the brake (ECB) 13 is calculated, and the electric power steering (EPS) 12 and the electronically controlled brake (ECB) 13 are operated according to the calculated control amount and the timing determined by the control determination unit 104. Let

  For example, the control amount calculation unit 105 calculates a target yaw rate necessary to avoid contact between the host vehicle and the three-dimensional object. Next, the control amount calculation unit 105 controls the control amount (steering torque) of the electric power steering (EPS) 12 and the electronic control formula so that the actual yaw rate of the host vehicle (the output signal of the yaw rate sensor 3) matches the target yaw rate. A control amount (brake hydraulic pressure) of the brake (ECB) 13 is determined. At that time, the relationship between the target yaw rate and the steering torque, and the relationship between the target yaw rate and the brake hydraulic pressure may be mapped in advance.

  The method of decelerating the vehicle is not limited to the method of operating the friction brake by the electronically controlled brake (ECB) 13, but the method of converting (regenerating) the kinetic energy of the vehicle into the electric energy or the transmission gear ratio. A method of increasing the engine brake by changing may be used. The method of changing the yaw rate of the vehicle is not limited to the method of changing the steering angle by the electric power steering (EPS) 12, and a method of applying different brake hydraulic pressures to the left and right wheels of the host vehicle may be used.

  By the way, when driving assistance using the electric power steering (EPS) 12 is performed, the course of the host vehicle is changed. At that time, if the course change of the host vehicle is accompanied by a lane change, the host vehicle may enter the course of the following vehicle traveling in the lane to be changed.

  For example, as shown in FIGS. 2 and 3, the host vehicle A travels in the first lane DL1, and the following vehicle B travels diagonally behind the host vehicle A in the second lane DL2 adjacent to the first lane DL1. In this case, when the obstacle C is detected on the course a of the host vehicle A, the control amount calculation unit 105 changes the course of the host vehicle A to the electric power steering (EPS) 12 and the electronically controlled brake ( ECB) 13 is controlled.

  At that time, as shown in FIGS. 4 and 5, the route of the host vehicle A is changed to a route that crosses the lane marking CL indicating the boundary between the first lane DL1 and the second lane DL2, in other words, a route a1 accompanied by a lane change. There is a possibility that. If the course of the host vehicle A is changed as shown in FIGS. 4 and 5, the course a1 after the change may intersect the course b of the following vehicle B. That is, there is a possibility that the host vehicle A enters the course b of the following vehicle B by driving support.

  Therefore, when the lane marking CL indicating the boundary of the lane DL is not detected on the road between the host vehicle A and the obstacle C, the control amount calculation unit 105 prohibits the course change of the host vehicle A while Driving assistance that can avoid contact between the vehicle A and the obstacle C is implemented.

  Specifically, the control amount calculation unit 105 controls the electronically controlled brake (ECB) 13 so that the host vehicle A stops before the obstacle C. When driving assistance is performed by such a method, driving assistance accompanied by a course change (lane change) is not performed when an obstacle C exists in the travel lane DL1 of the host vehicle A. As a result, it is possible to avoid a situation in which the host vehicle A enters the course of the following vehicle B due to the driving assistance. Moreover, since an apparatus for detecting a succeeding vehicle existing on the side or rear of the host vehicle A is not required, an increase in the number of parts and an increase in manufacturing cost can be suppressed.

  On the other hand, as shown in FIGS. 6 and 7, when there is a lane marking CL indicating the boundary of the lane DL on the road between the own vehicle A and the obstacle C, the control amount calculation unit 105 The driving assistance that can avoid the contact between the own vehicle A and the obstacle C is performed while permitting the change of the route. That is, the control amount calculation unit 105 calculates a target yaw rate necessary to avoid contact between the host vehicle A and the obstacle C, and the electric power steering (EPS) 12 so that the actual yaw rate matches the target yaw rate. And an electronically controlled brake (ECB) 13 is controlled.

  When the lane marking CL exists on the road between the host vehicle A and the obstacle C, the obstacle C exists outside the lane DL on which the host vehicle A is traveling, and the host vehicle A is traveling. It can be considered that the vehicle is about to depart from the lane DL. Therefore, as shown in FIGS. 8 and 9, if the course of the host vehicle A is changed to a course a1 that travels along the travel lane DL, it is possible to avoid contact with other vehicles while avoiding contact with other vehicles. Contact can also be avoided.

  Therefore, when calculating the target yaw rate, the control amount calculation unit 105 calculates the target yaw rate necessary to change the actual route of the host vehicle A to the route a1, and the actual yaw rate matches the target yaw rate. Thus, the electric power steering (EPS) 12 and the electronically controlled brake (ECB) 13 are controlled.

  Hereinafter, the driving assistance execution procedure in the present embodiment will be described with reference to FIG. FIG. 10 is a processing routine that is repeatedly executed by the ECU 1 and is stored in advance in the ROM of the ECU 1 or the like.

  In the processing routine of FIG. 10, first, in S101, the ECU 1 generates information (running road information) related to a running road on which the host vehicle will run from the output signal of the external environment recognition device 2. Specifically, in the coordinate system with the own vehicle as the origin, the ECU 1 is a three-dimensional object that can be an obstacle of the own vehicle, the position of a lane line that indicates the boundary of the lane in which the own vehicle is traveling, the three-dimensional object, Information about the attitude of the host vehicle with respect to the lane marking is generated.

  In S102, the ECU 1 identifies a route (route) that the host vehicle is predicted to pass through in the coordinate system generated in S101. Specifically, the ECU 1 acquires the current lateral acceleration of the host vehicle from the output signal of the acceleration sensor 5, and specifies a course predicted to pass when the host vehicle travels while maintaining the current lateral acceleration.

  In S103, ECU1 discriminate | determines whether the solid object which becomes an obstruction exists on the course of the own vehicle based on the coordinate system produced | generated by said S101, and the course predicted by said S102. If a negative determination is made in S103, the ECU 1 ends the execution of this routine without performing driving support. On the other hand, if an affirmative determination is made in S103, the ECU 1 proceeds to S104.

  In S104, the ECU 1 determines whether or not there is a lane marking indicating a lane boundary on the road between the host vehicle and the obstacle in the coordinate system generated in S101. If an affirmative determination is made in S104, the ECU 1 executes the process of S105. On the other hand, if a negative determination is made in S104, the ECU 1 executes the process of S106.

  In S105, the ECU 1 permits the execution of driving assistance accompanied by a change in the course of the host vehicle. In that case, the ECU 1 first performs driving support using the buzzer 10 or the display device 11. Thereafter, if the driver does not perform a driving operation for avoiding the obstacle, the ECU 1 performs driving assistance using at least one of the electric power steering (EPS) 12 and the electronically controlled brake (ECB) 13. Specifically, the ECU 1 calculates a target yaw rate required when the host vehicle travels without departing from the lane marking, and the electric power steering (EPS) 12 and the electronic device so that the actual yaw rate matches the target yaw rate. Control at least one of the controlled brakes (ECB) 13.

  When driving assistance is performed by such a method, it is possible to avoid contact between the host vehicle and an obstacle while preventing the host vehicle from departing from the traveling lane. As a result, it is possible to avoid contact with an obstacle while avoiding a situation in which the host vehicle enters the course of a succeeding vehicle traveling in another lane. It should be noted that the changing means according to the present invention is realized by the ECU 1 executing the process of S105.

  Moreover, in S106, ECU1 prohibits implementation of the driving assistance accompanying the course change of the own vehicle. That is, the ECU 1 prohibits driving assistance using the electric power steering (EPS) 12. In that case, the ECU 1 first performs driving support using the buzzer 10 or the display device 11. Thereafter, if the driver does not perform a driving operation for avoiding the obstacle, the ECU 1 performs driving support using only the electronically controlled brake (ECB) 13. Specifically, the ECU 1 calculates a deceleration acceleration necessary for the host vehicle to stop before the obstacle, and calculates a target brake hydraulic pressure necessary for obtaining the deceleration acceleration. The ECU 1 controls the electronically controlled brake (ECB) 13 so that the actual brake hydraulic pressure matches the target brake hydraulic pressure.

  When driving assistance is implemented by such a method, it is possible to avoid contact between the host vehicle and an obstacle while prohibiting a change in the course of the host vehicle. In other words, it is possible to avoid contact with an obstacle while avoiding a situation in which the host vehicle enters the course of a subsequent vehicle traveling in another lane. As a result, it is possible to avoid a situation in which contact between the host vehicle and the following vehicle is induced by the implementation of driving assistance. In addition, since an apparatus for detecting a succeeding vehicle existing on the side or rear of the host vehicle is not required, an increase in the number of parts and an increase in manufacturing cost can be suppressed. In addition, when the ECU 1 executes the process of S106, the prohibiting unit and the decelerating unit according to the present invention are realized.

  According to the embodiment described above, in a vehicle driving support device that changes the course of the host vehicle when a three-dimensional object is present on the course of the host vehicle, a subsequent vehicle that travels behind the host vehicle is detected. Without depending on the device, it is possible to avoid a situation in which the own vehicle enters the course of the following vehicle by changing the course of the own vehicle.

1 ECU
2 External recognition device 3 Yaw rate sensor 4 Wheel speed sensor 5 Acceleration sensor 6 Brake sensor 7 Acceleration sensor 8 Steering angle sensor 9 Steering torque sensor 10 Buzzer 11 Display device

Claims (3)

In a vehicle driving support device for changing the course of the host vehicle when a three-dimensional object is present on the course of the host vehicle,
Detecting means for detecting a lane marking on the road indicating a lane boundary;
When a lane marking indicating a lane boundary is not detected on the road between the host vehicle and the three-dimensional object, a prohibition unit that prohibits a change of course of the host vehicle,
A vehicle driving support device.   The vehicle driving support device according to claim 1, further comprising a decelerating unit that decelerates the host vehicle when a change in the course of the host vehicle is prohibited by the prohibiting unit.   In claim 1 or 2, when a lane marking indicating a lane boundary is detected on the road between the host vehicle and the three-dimensional object, the route of the host vehicle is set so that the host vehicle does not deviate from the boundary of the lane. A driving support apparatus for a vehicle, further comprising changing means for changing.

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