JP4058516B2 - Zero point setting device for torque sensor in vehicle steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a zero point setting device for a torque sensor in a steering device for a vehicle such as an automobile.
[0002]
[Prior art]
In a steering apparatus for a vehicle, particularly a steering apparatus for an automobile, a power assist mechanism (power steering apparatus) for steering operation is widely used. For this reason, most automobiles produced in the factory are now standard equipment, and there is an increasing number of repairs and replacements by dealers (dealers) regardless of whether they are new or used. As such a power steering device, a torque detection means detects a steering torque applied to a handle shaft via a steering handle, and a driving force corresponding to the steering torque is applied from an auxiliary power generation means such as an electric motor to a steering wheel. What to give is common (refer patent document 1 or 2).
[0003]
By the way, in the power steering apparatus as described above, the torque detection means includes a torsion bar and a pair of angle detection sensors, such as a twin resolver system (see Patent Document 3), which are spaced apart in the axial direction thereof. In addition, it is extremely difficult in manufacturing to assemble the sensors so that the mounting angle positions of both sensors are completely the same. For this reason, it is no exaggeration to say that a zero point torque error due to the difference between the origin positions of the pair of angle detection sensors always occurs. For this reason, in the pair of angle detection sensors, after both sensors are assembled, the torque (zero point torque error) based on the difference in the origin position when the steering handle is neutral is measured, and this is used as the initial value for power steering. It memorize | stores in the control part of an apparatus. In the subsequent control of the power steering device, when a predetermined steering force is applied to the steered wheels, a torque that takes into account the zero point torque error is calculated with respect to the apparent steering torque detected by the angle detection sensor. Steering control.
[0004]
As a factor affecting steady steering control, in addition to the zero point torque error, the residual torque (hysteresis) due to incomplete return of the steering handle even if the applied torque is removed due to friction of the drive transmission system, etc. There is residual torque generated by
[0005]
[Patent Document 1]
JP 2000-168597 A [Patent Document 2]
JP 2001-341656 A [Patent Document 3]
JP-A-2001-194251 [0006]
[Problems to be solved by the invention]
Therefore, when the applied torque is removed by holding the steering handle stationary at the neutral position in the steering direction in order to perform the initial setting of the steering control of the power steering device, the torque detecting means is zero corresponding to the assembly error in manufacturing. An initial torque including a point torque error and a residual torque due to an incomplete return of the steering handle is detected and indicated. Of these, the zero point torque error cannot be removed without disassembling / adjusting the torque detection means. However, the zero point torque error exists as an eigenvalue (constant value) of the device and can be calibrated (corrected). If the value of the torque error can be specified, the influence on the steady steering control is relatively small. On the other hand, regarding the residual torque, if the residual torque remains (mixed) in the initial torque detection value at the time of initial setting, the state shifts to a steady steering control state and the incomplete return of the steering handle is resolved. The residual torque is likely to cause the steering control to malfunction. Then, rather than the column assist type power steering device (Patent Document 2) in which the auxiliary power generation means and the torque detection means are provided in the steering column, they are provided in the vicinity of the steering shaft (rack teeth). In the case of (Patent Document 1), the distance between the steering handle and the torque detection means becomes longer, and is more susceptible to the residual torque.
[0007]
Regardless of which method is used in Patent Documents 1 and 2, the following operations (1), (2), and (3) are conventionally performed at the time of assembly / inspection in factory production or repair / replacement at a dealer. Both were performed manually (workers).
(1) Operation to hold the steering handle stationary at a neutral position in the steering direction (2) Reducing the residual torque that appears as hysteresis by rotating the steering handle by rotating it slightly around the axis of the steering wheel. Operation (3) While the steering handle is held stationary at a neutral position in the steering direction, the operation of detecting the initial torque by the torque detecting means is reduced (ideally, the residual torque approaches 0 in the above (2)). The power steering device is standard equipment, such as increased production costs at factories and misalignments due to lack of personnel at dealers, etc. It was a problem when doing so.
[0008]
The problem of the present invention is that the residual torque can be easily reduced to a level that does not hinder the steering control without requiring skilled skills and long-time adjustment work, thereby reducing costs and stabilizing performance. Another object of the present invention is to provide a torque sensor zero point setting device in a vehicle steering device.
[0009]
[Means for Solving the Problems and Effects of the Invention]
In order to solve the above problem, a torque sensor zero-point setting device in a vehicle steering device of the present invention includes:
Based on the output of a torque sensor that is provided in a steering force transmission system from the steering wheel of the vehicle to the steering wheel and detects steering torque, a steering drive device that applies steering force to the steering wheel is controlled via its steering control means. In a vehicle steering apparatus that
Prior to detection of a zero point torque error of the torque sensor in a state where the steering wheel is at a reference position such as a neutral position in the traveling direction and no steering torque is applied to the steering handle, the steering wheel is moved at a small angle in the steerable direction. A steering wheel damping vibration applying device for ending the vibration while reducing the amplitude while vibrating in a range,
When the output of the torque sensor at or near the end of the vibration is stored in the storage unit of the steering control means as the zero point torque error of the torque sensor, when the steering drive device actually operates, The operation of the steering drive device is controlled via the steering control means based on a correction torque calculated in consideration of the zero point torque error from an apparent output of a torque sensor.
[0010]
Further, the steering wheel damping vibration applying device is:
A turntable installed to be able to rotate at least in the minute angle range in a plane corresponding to the steerable direction by grounding the steered wheel at the reference position;
And a turntable vibration device for ending the vibration while applying a driving force of an attenuation pattern that vibrates the turntable in the minute angle range and reduces the amplitude thereof.
[0011]
The turntable vibration device includes a vibration applying motor that drives the turntable in both forward and reverse directions within the minute angle range;
Motor control means for controlling the electric power to the motor so as to obtain the vibration amplitude of the attenuation pattern.
[0012]
The turntable vibration device includes:
By urging the turntables installed so as to be able to swing in a plane corresponding to the steerable direction with opposite biasing forces in the swinging direction and with an equal biasing force, the turntable is allowed to swing freely and freely. Elastic support means for supporting the elastic support system in a state;
By rotating the turntable supported by the elastic support system in one direction so as to oppose the one urging means generating urging forces in opposite directions, the elastic reaction force of the one urging means And a vibration start device that starts the vibration by reversing the turntable in the other direction,
Thereafter, the turntable continues to vibrate by means of urging means that alternately generate reaction forces in opposite directions, and the vibration ends by natural damping of vibration energy.
[0013]
The torque sensor includes a torsion angle detection unit arranged to form a pair at both axial ends of the torsion bar in order to detect the torsion angle of the torsion bar interposed in the shaft part of the steering force transmission system, The shaft torque of the torsion bar is detected through the twist angle based on the relative angle output difference of the twist angle detector.
[0014]
According to the torque sensor zero point setting device in these vehicle steering devices, the residual torque can be reduced (removed) with high accuracy in a short time. Therefore, as an initial torque detected at the time of initial setting of the power steering apparatus, zero is inevitably generated in manufacturing in the torque detection means including the torsion bar and the pair of angle detection sensors in a state where the residual torque is reduced (removed) as much as possible. It becomes possible to detect the point torque as accurately and rapidly as possible.
[0015]
At this time, the initial torque storage command unit may be stored in the storage unit of the steering control unit together with the initial setting program, and the initial setting program may be activated by a specific trigger signal transmitted from the outside of the vehicle. For example, if you connect a portable terminal device (such as a small tester) that can send a specific trigger signal to the steering control means on the vehicle side, you can perform the initial setting of the steering control unit without bringing it into the production factory. It becomes easy to repair and replace various parts and parts structures constituting the power steering device at the stage of a supplier or the like.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 schematically shows the overall configuration of a torque sensor zero point setting device in a vehicle steering system as an example to which the present invention is applied (in this embodiment, “vehicle” is an automobile. However, the application target of the present invention is not limited to this). An electric power steering device 100 (hereinafter also simply referred to as a power steering device), which is a vehicle steering device, includes a pinion shaft 3 that is coupled to a steering handle 1 and rotates together with the handle shaft 2. The pinion 4 fixed to the tip meshes with the rack teeth 5 a of the steering shaft 5. The steering shaft 5 reciprocates in the axial direction to change the turning angle of the steering wheels 6 and 6. An assist motor 20 (DC electric motor) is coaxially assembled to the steering shaft 5 of the power steering apparatus 100 via a ball screw mechanism (not shown), and the driving force of the assist motor 20 is driven by the steering handle 1. The rack assist type assists the reciprocating motion of the steering shaft 5 (power assist).
[0017]
A torque sensor 10 (torque detection means) is provided between the handle shaft 2 and the pinion shaft 3, and the torque sensor 10 is a torsion bar 11 and a pair of resolvers 12 and 12 (angles) installed apart from each other in the axial direction thereof. Detection sensor). When torque is applied to the torsion bar 11 and the resolvers 12 and 12 detect the angle difference between both ends, the torque applied to the torsion bar 11 from the angle difference measured by the resolvers 12 and 12 and the spring constant of the torsion bar 11. Is detected. The assist motor 20 generates a driving force corresponding to the torque applied to the torsion bar 11 detected by the torque sensor 10 via the motor driver 22.
[0018]
The vehicle is placed on a horizontal floor. The turntables 56 and 56 are installed so that the ground contact surface with the steering wheels 6 and 6 is flush with the floor surface. When the vehicle is lifted by a lift or jack and the steered wheels 6 and 6 are in a non-grounded state, the turntables 56 and 56 are steered so that the steered wheels 6 and 6 are in contact with the turntables 56 and 56. According to the position of the wheels 6 and 6, the structure is such that the same load is applied to the turntables 56 and 56 as when the vehicle is placed on a horizontal floor.
[0019]
The steering control unit 30 includes a CPU 31, a RAM 32, a ROM 33, an input / output interface 34, and the like, and is configured by a microcomputer connected to the bus 35 so as to be able to transmit and receive. The ROM 33 has a program storage area 33a and a data storage area 33b. The program storage area 33a stores a steering control program for controlling the steering angle and steering torque, an initial setting program described later, and the like. The data storage area 33b stores an initial torque, which will be described later, and has a function of an initial torque storage means. The CPU 31 has a function as an initial torque storage command means.
[0020]
The initial setting program stored in the program storage area 33a is for detecting the initial torque after the residual torque has been reduced (removed) and storing the detected initial torque in the data storage area 33b. Can be used in the steering control program as a correction value of the steering torque. Here, a small tester 40 (portable terminal device) is connected to the input / output interface 34, and the initial setting program is activated by a specific trigger signal transmitted from the small tester 40. Of course, an initial setting program is downloaded to the steering control unit 30 from an external microcomputer provided in a production factory or the like via a communication line / storage medium, etc., and a trigger signal from the external microcomputer is received for initial setting. You may make it start a program.
[0021]
When the trigger signal is input, the CPU 31 reads the initial setting program from the program storage area 33a of the ROM 33, and executes at least the following contents of the program according to the following procedure.
(1) The initial torque caused mainly by the difference between the origin positions of the pair of resolvers 12 and 12 is detected by the torque sensor 10 in a state where the residual torque is reduced.
(2) The detected initial torque is stored in the data storage area 33b (initial torque storage means) of the steering control unit 30 as a correction value of the steering torque.
The data storage area 33b is preferably an E ² PROM that can be electrically written and erased so that an initial torque can be written at each initial setting.
[0022]
Next, the contents of the steering control will be described with reference to the flowchart of FIG. FIG. 3 shows an overview of the steering control program. The presence / absence of an external trigger signal is monitored. If there is a signal input (YES in S1), the initial torque is detected and stored by the torque sensor 10 (S2). If there is no signal input (NO in S1), whether or not torque is applied to the torsion bar 11 is checked based on whether or not there is a change in the angle difference between the pair of resolvers 12 and 12 (S3). If there is a change in the angle difference between the resolvers 12 and 12 (YES in S3), the applied torque is detected by the torque sensor 10 (S4). Then, the motor driver 22 is driven to rotate the assist motor 20 with a driving force corresponding to the applied torque detected by the torque sensor 10 (S5). If there is no change in the angle difference between the resolvers 12 and 12 (NO in S3), the process ends.
[0023]
On the other hand, as shown in FIG. 2, the residual torque removal control unit 50 includes a CPU 51, a RAM 52, a ROM 53, an input / output interface 54, and the like, and these are configured by a microcomputer connected to be able to transmit and receive via a bus 55. The ROM 53 has a program storage area 53a and a data storage area 53b. The program storage area 53a stores a residual torque removal control program. A virtual torque described later is stored in the data storage area 53b.
[0024]
The residual torque removal control unit 50 is connected to the torque sensor 10 and the motor 57 via the input / output interface 54. The motor 57 rotates the turntable 56 in a minute angle range via the speed reducer 58. In FIG. 2, only the right turntable 56 is rotated by the motor 57 in the traveling direction of the steering wheel, and the left turntable 56 is freely rotated in the traveling direction of the steering wheel. A configuration may be adopted in which both the left and right turntables are rotated in a minute angle range by a motor.
[0025]
Here, a small tester 40 (portable terminal device) is connected to the input / output interface 54, and the residual torque removal control program is started by a specific trigger signal transmitted from the small tester 40. Of course, the initial setting program is downloaded to the residual torque removal control unit 50 from an external microcomputer provided in a production factory or the like via a communication line or storage medium, and a trigger signal is received from the external microcomputer. You may make it start a residual torque removal control program.
[0026]
When the trigger signal is input, the CPU 51 reads the residual torque removal control program from the program storage area 53 a of the ROM 53 and executes it. That is, from the state in which the steering handle 1 is held stationary at the neutral position in the steering direction, the turntable 56 is slightly rotated using the motor 57, and the residual torque that appears as hysteresis between the steering handle 1 and the torque sensor 10. Is reduced (removed). The data storage area 53b is preferably an E ² PROM that can be electrically written and erased so that a virtual torque according to the configuration of the power steering apparatus can be written.
[0027]
The residual torque removal program will be described using the flowchart of FIG. First, in S21, the operator holds the steering handle 1 stationary at a neutral position in the steering direction. Next, a virtual torque value Tk (for example, +2 N · m) to be applied to the turntable 56 is set in S22, and a target rotation angle θm that is assumed to cause the turntable 56 to slightly rotate by the virtual torque value Tk in S23, The absolute value of the actual rotation angle θz detected by the torque sensor 10 is compared. Since the steering wheels 6 and 6 are initially held stationary at the neutral position in the steering direction, | θz | <θm (NO in S23), and corresponds to the virtual torque value Tk (or the target rotation angle θm) in S27. A current (current value and energization time) is supplied to the motor 57 (for example, a current value corresponding to a torque of +2 N · m and a time of 60 msec; see FIG. 5A). Since the target rotation angle θm is initially greater than 0 in S28 (NO in S28), the process returns to S23, and again comparing the target rotation angle θm and the absolute value of the actual rotation angle θz, | θz | ≧ θm (S23 YES, the virtual torque value Tk is reversed and set in S24, and when the virtual torque value Tk is set to decrease (for example, -1.5 N · m) in S25, the corresponding target rotation angle θm is also set to decrease. (S26). Next, a current (current value and energization time) corresponding to the virtual torque value Tk (or target rotation angle θm) reset in S27 is supplied to the motor 57 (for example, a current corresponding to a torque of −1.5 N · m). 60 msec in value; see FIG. 5 (a)).
[0028]
By repeating S24 to S27, at least one of the operation of reducing the absolute value of the current flowing through the motor 57 and the operation of shortening the energization time is performed (both operations are performed in FIG. 5A), and the turntable The absolute value of the torque value for forward / reverse rotation 56 is decreased with time. Therefore, the turntable 56 is periodically forward / reversely rotated by the motor 57 with a predetermined torque value (virtual torque value Tk) and a rotation direction. The torque sensor 10 detects the torque applied by the motor 57, but the motor 57 does not depend on the torque value detected by the torque sensor 10, but according to the virtual torque value Tk that is predetermined by the initial setting program. Rotate slightly.
[0029]
When the target rotational angle θm becomes 0 or less in S28 (YES in S28), it is determined that the residual torque has been sufficiently reduced (substantially to 0), and the minute rotational motion by the motor 57 is terminated (stopped). . Transition of the target rotation angle θm and the actual rotation angle θz at this time is expressed as shown in FIG.
[0030]
Subsequently, a trigger signal is transmitted from the tester 40 to the steering control unit 30, an initial setting program is executed, and an initial torque T0 (for example, +0.2 N · m) is detected by the torque sensor 10 (S29). The detected initial torque T0 is stored in the data storage area 33b of the steering control unit 30 as a steering torque correction value (S30).
[0031]
In S21 of FIG. 4, the operator may advance to the next step by pressing the confirmation switch when confirming the stationary holding at the neutral position of the steering handle 1.
[0032]
As described above, in the residual torque reduction operation of FIG. 4, the steering wheel 6 is repeatedly rotated forward and backward at a predetermined torque value using the turntable 56, and the absolute value of the torque value is reduced as time passes. As a result, the occurrence of an incomplete return phenomenon (hysteresis phenomenon) of the steering handle 1 can be suppressed, and the residual torque can be reduced (removed) in a short time to such an extent that the steering control is not hindered. In the DC motor, the current value is proportional to the driving torque (rotational force). Therefore, in the residual torque reduction operation, if the current value flowing through the motor 57 is a control target (parameter), the torque value can be precisely controlled using the motor 57 (DC motor).
The means for reducing the rotational force (torque) applied to the turntable 56 by the motor 57 with time can be selected from the following.
(1) Reduce the current value gradually;
(2) Decreasing energization time gradually;
(3) Perform (1) and (2) simultaneously;
[0033]
In the above-described residual torque removal control, the turntable is rotated by a motor. However, instead of the motor, it may be finely vibrated by a solenoid, or an electromagnet and a permanent magnet are combined to use the attractive / repulsive force by magnetic force. Micro vibrations may be used.
[0034]
Moreover, you may take the method of vibrating a turntable, without performing a motor drive like FIG. This method will be described below. FIG. 6 is a view of the turntable as viewed from below. As shown in FIG. 6A, the connecting portion 62 of the springs 60 and 61 connected in series to the turntable 56 is fixed, and the ends of the springs 60 and 61 are orthogonal to the traveling direction of the vehicle. Fix outside. A protrusion 64 is provided at a position opposite to the rotation center 63 of the turntable 56 when viewed from the connecting portion 62, and the protrusion 64 is left when the L-shaped shaft 59 is viewed from the top surface of the turntable 56 with respect to the traveling direction. It is structured to pull in the direction.
[0035]
When the shaft 59 is pulled, the protrusion 64 is also pulled by the shaft 59. When the shaft 59 is pulled to a predetermined position as shown in FIG. 6B, the protrusion 64 is detached from the shaft 59. At this time, damped vibration is performed by the restoring force of the springs 60 and 61, and the turntable 56 is damped and vibrated accordingly. As the turntable 56 moves, the steering wheel 6 also vibrates to remove the residual torque.
[0036]
As the springs 60 and 61 in this case, those that can apply a virtual torque as shown in FIG. The means for pulling the shaft 59 is not particularly limited as long as it can be controlled such as a combination of a motor and a gear, a solenoid, a hydraulic cylinder, or the like. Further, instead of the shaft 59, a method may be adopted in which a cam is disposed so as to contact the projection 64 with a rotating shaft outside the turntable and the projection 64 is pushed. The attachment positions of the springs 60 and 61, the shaft 59, and the protrusion 64 are not particularly limited as long as the residual torque can be removed.
[0037]
After the residual torque is removed as described above, a trigger signal is transmitted from the small tester 40 to the steering control unit 30, an initial setting program is executed, the initial torque T0 is detected by the torque sensor 10, and the data storage area 33b is detected. Remember.
[0038]
Note that when the residual torque removal control program stored in the residual torque removal control unit 50 and the initial setting program stored in the steering control unit 30 are executed in the inspection process of the production factory or the repair process of the dealer, etc. The matters are as follows.
(1) Start with the steering handle 1 held stationary at a neutral position in the steering direction.
(2) Do not apply applied torque to the steering handle 1 and the steering wheels 6 and 6 (wheels) from the outside including the operator.
(3) Install a battery.
(4) The steered wheels 6 and 6 (wheels) are in contact with the turntables 56 and 56.
[0039]
In the above description, only the rack assist type power steering apparatus has been taken up, but it goes without saying that the present invention can also be applied to a column assist type power steering apparatus. In addition, as long as the steering handle and the steering wheel are mechanically connected, the present invention can be implemented even with a steering force variable type power steering device such as a speed sensitive type or a rotational speed sensitive type. In addition to the electric motor, a hydraulic motor, a hydraulic cylinder, or the like can be used as the auxiliary power generation source. In the residual torque reduction operation (S24 to S27) in FIG. 4, after performing a plurality of micro rotational movements at a predetermined virtual torque value Tk (for example, ± 2 N · m), the virtual torque value Tk is decreased ( For example, ± 1.5 N · m) A plurality of micro rotational movements may be performed.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the overall configuration of a torque sensor zero point setting device in a vehicle steering system as an example of the present invention;
FIG. 2 is a schematic diagram showing a configuration of a residual torque removal control unit.
FIG. 3 is a flowchart showing the contents of a steering control program.
FIG. 4 is a flowchart showing the contents of a residual torque removal program.
FIG. 5 is an explanatory diagram showing a state of a residual torque reducing operation in FIG.
FIG. 6 is an explanatory diagram showing a modification of residual torque removal control.
[Explanation of symbols]
1 Steering handle 2 Handle shaft 6 Steering wheel 10 Torque sensor (torque detection means)
11 Torsion bar 12 Resolver (angle detection sensor)
20 Assist motor (electric motor)
30 Steering control unit 31 CPU (initial torque detection command means, initial torque storage command means)
33 ROM (initial torque storage means)
50 Residual torque removal control unit 51 CPU (residual torque removal means)
56 Turntable 57 Motor 58 Reducer 100 Power steering device

Claims (5)

Based on the output of a torque sensor that is provided in a steering force transmission system from the steering wheel of the vehicle to the steering wheel and detects steering torque, a steering drive device that applies steering force to the steering wheel is controlled via its steering control means. In a vehicle steering apparatus that
Prior to detection of a zero point torque error of the torque sensor in a state where the steering wheel is at a reference position such as a neutral position in the traveling direction and no steering torque is applied to the steering handle, the steering wheel is moved at a small angle in the steerable direction. A steering wheel damping vibration applying device for ending the vibration while reducing the amplitude while vibrating in a range,
When the output of the torque sensor at or near the end of the vibration is stored in the storage unit of the steering control means as the zero point torque error of the torque sensor, when the steering drive device actually operates, The vehicle steering apparatus characterized in that the operation of the steering drive device is controlled via the steering control means based on a correction torque calculated in consideration of the zero point torque error from an apparent output of a torque sensor. Torque sensor zero point setting device. The steering wheel damping vibration applying device is:
A turntable installed so as to be able to vibrate and rotate at least in the minute angle range in a plane corresponding to the steerable direction by grounding the steered wheel at the reference position;
A turntable vibration device that terminates vibration while applying a driving force of an attenuation pattern that vibrates the turntable in the minute angle range and reduces the amplitude;
A zero point setting device for a torque sensor in a vehicle steering system according to claim 1. The turntable vibration device includes a vibration applying motor that drives the turntable in both forward and reverse directions within the minute angle range;
Motor control means for controlling the electric power to the motor so as to obtain the vibration amplitude of the attenuation pattern;
A zero point setting device for a torque sensor in a vehicle steering system according to claim 2. The turntable vibration device includes:
By urging the turntables installed so as to be able to swing in a plane corresponding to the steerable direction with opposite biasing forces in the swinging direction and with an equal biasing force, the turntable is allowed to swing freely and freely. Elastic support means for supporting the elastic support system in a state;
By rotating the turntable supported by the elastic support system in one direction so as to oppose the one urging means generating urging forces in opposite directions, the elastic reaction force of the one urging means And a vibration start device that starts the vibration by reversing the turntable in the other direction,
The torque sensor zero in the vehicle steering system according to claim 2, wherein the vibration is continued by the biasing means that alternately generates reaction forces in opposite directions to each other, and the vibration is terminated by natural damping of the vibration energy. Point setting device.   The torque sensor includes a torsion angle detection unit arranged to form a pair at both axial ends of the torsion bar in order to detect the torsion angle of the torsion bar interposed in the shaft part of the steering force transmission system, The torque sensor zero in the vehicle steering system according to any one of claims 1 to 4, wherein the axial torque of the torsion bar is detected via a torsion angle based on a relative angle output difference of the torsion angle detection unit. Point setting device.

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