JP5131422B2 - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device providing good steering feeling by suppressing interference of motor control. <P>SOLUTION: An EPS 1 is provided with a rack ECU 31 controlling operation of a rack actuator 23 and a column ECU 32 controlling operation of a column actuator 24. The rack ECU 31 and column ECU 32 (respective microcomputers 41, 42 thereof) calculate electric current values I_r*, I_c* as target assist force by superposing compensation components Ic_r*, Ic_c* calculated by compensation control on basic assist control components Ias_r*, Ias_c*, respectively. The rack ECU 31 and column ECU 32 do not perform compensation control identical to that performed by the other side. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to an electric power steering apparatus including two motors.

  Conventionally, a power steering apparatus for a vehicle includes an electric power steering apparatus (EPS) using a motor as a drive source. Such EPS has a high degree of freedom in layout as compared with a hydraulic power steering apparatus. It is characterized by low energy consumption. For this reason, in recent years, adoption of EPS has been studied not only for small vehicles but also for large vehicles, and in order to cope with this, further improvement in output performance is strongly demanded.

  However, in reality, the vehicle space in which the EPS actuator can be installed is limited. In particular, in the so-called rack-type and pinion-type EPS, there is already much room for increasing the size of the motor as the drive source. The fact is not. Even in the case of a column type EPS having a relatively large installation space, there is a problem in that a significant increase in weight is caused by strengthening the steering shaft to cope with the increase in output.

Thus, conventionally, there has been proposed an EPS in which two motors are used as a drive source, one motor is used to apply assist force to the rack shaft, and the other motor is used to apply assist force to the steering shaft (for example, Patent Documents). 1). And by adopting such EPS, it becomes possible to cope with a large output while avoiding the problem of installation space and weight increase, and ensuring high reliability by ensuring redundancy. become able to.
JP 2004-82798 A

  However, when two motors are used as drive sources, it is difficult to match the phases of the controls, and the control of both motors may interfere with each other due to the phase shift. In particular, in the configuration in which one assists the rack shaft and the other assists the steering shaft as described above, it is difficult to match the phases of the two because there is a twist of the steering shaft. For this reason, there is a possibility that the steering feeling deteriorates due to the occurrence of the interference, and there is still room for improvement in this respect.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide an electric power steering apparatus capable of realizing good steering feeling by suppressing interference of motor control. It is in.

In order to solve the above problems, the invention according to claim 1 is directed to a first steering force assisting device provided to give an assist force for assisting a steering operation to a rack shaft, and the steering shaft to the steering shaft. By supplying driving power to the second steering force assisting device provided to apply the assisting force and the first and second motors that are the driving sources of the corresponding steering force assisting devices, First and second control means for controlling the operation of the steering force assisting device, and first and second current sensors for detecting actual current values energized in the first and second motors, respectively . said first and second control means, the basic assist component, by superimposing the various computed compensation component by the compensation control, said corresponding current as a target assist force to be generated in each steering force assist device By calculating the decree value, said calculating a current command value, wherein an electric power steering apparatus wherein the current command value to perform respectively a feedback control so as to follow the actual current value, said first and second The gist is that the control means does not simultaneously perform the same compensation control as the other.

  That is, the mutual interference of the motor control tends to become remarkable when the compensation control is executed. Therefore, unlike the above configuration, the occurrence of such mutual interference can be suppressed by not performing the same compensation control as that performed on the other side. As a result, a good steering feeling can be ensured.

  According to a second aspect of the present invention, the first control means corresponding to the first steering force assisting device performs torque inertia compensation control for compensating for an influence due to inertia of the steering force assisting device, and The gist is that the second control means corresponding to the second steering force assisting device does not perform the torque inertia compensation control.

  That is, the torque inertia compensation control is a control that compensates for the influence of the inertia of the steering force assisting device such as a motor or an actuator, and the “feeling of catching (following delay)” at the “start of turning” and “end of cutting” in the steering operation. This is executed for the purpose of suppressing the “flow feeling (overshoot)”. Therefore, it is desirable to perform the control in the first steering force assisting device that is closer to the steered wheels, thereby suppressing the occurrence of the above-described mutual interference without reducing the effect of the torque inertia compensation control. .

  According to a third aspect of the present invention, the second control means corresponding to the second steering force assisting device performs a steering return compensation control for smoothly returning the steering to the neutral position, The gist is that the first control means corresponding to the first steering force assisting device does not perform the steering return compensation control.

  In other words, the steering return compensation control is compensation control for smooth return to the neutral position of the steering. Therefore, it is desirable to perform the control in the second steering force assisting device that is closer to the steering, whereby the occurrence of the above-described mutual interference can be suppressed without reducing the effect of the steering return compensation control.

  According to a fourth aspect of the present invention, the second control means corresponding to the second steering force assisting device performs damper compensation control for suppressing steering fluctuation, and the first steering force assisting device. The gist of the first control means corresponding to is that the damper compensation control is not performed.

  That is, the damper compensation control is compensation control for suppressing steering fluctuation. Therefore, it is desirable to perform the control in the second steering force assisting device that is closer to the steering, so that the occurrence of the above-described mutual interference can be suppressed without reducing the effect of the damper compensation control.

  ADVANTAGE OF THE INVENTION According to this invention, the electric power steering apparatus which can suppress the interference of motor control and can implement | achieve favorable steering feeling can be provided.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
As shown in FIG. 1, in the electric power steering apparatus (EPS) 1 of the present embodiment, a steering shaft 3 to which a steering 2 is fixed is connected to a rack shaft 5 via a rack and pinion mechanism 4, and the steering The rotation of the steering shaft 3 accompanying the operation is converted into a reciprocating linear motion of the rack shaft 5 by the rack and pinion mechanism 4. Specifically, the steering shaft 3 of the present embodiment is formed by connecting a column shaft 8, an intermediate shaft 9, and a pinion shaft 10 via universal joints 7a and 7b. The rack and pinion mechanism 4 includes: The pinion teeth 10a formed at one end of the pinion shaft 10 are engaged with the rack teeth 5a on the rack shaft 5 side. The reciprocating linear motion of the rack shaft 5 accompanying the rotation of the steering shaft 3 is transmitted to a knuckle (not shown) via tie rods 11 connected to both ends of the rack shaft 5, whereby the steered angle of the steered wheels 12. That is, the traveling direction of the vehicle is changed.

  The EPS 1 of the present embodiment has a plurality (two) of motors 21 and 22 as drive sources for generating an assist force for assisting a steering operation with respect to the steering system configured as described above. Specifically, the EPS 1 applies assist force to the column shaft 8 using the motor 22 as a drive source and a rack actuator 23 as a first steering force assisting device that applies assist force to the rack shaft 5 using the motor 21 as a drive source. And a column actuator 24 as a second steering force assisting device.

  More specifically, in the present embodiment, the rack actuator 23 includes a motor 21 as a drive source and a ball screw mechanism 26, and the motor torque of the motor 21 is converted into an axial pressing force by the ball screw mechanism 26. Then, it is transmitted to the rack shaft 5. Then, the rack shaft 5 is moved in the axial direction by the motor torque so that an assist force is applied to the rack shaft 5.

  On the other hand, the column actuator 24 includes a motor 22 that is a drive source and a speed change mechanism (worm and wheel) 27. The column actuator 24 is configured to apply an assist force to the column shaft 8 (the steering shaft 3) by transmitting the motor torque of the motor 22 to the column shaft 8 via the speed change mechanism 27. .

  The EPS 1 of the present embodiment includes a rack ECU 31 as a first control unit that controls the operation of the rack actuator 23 and a column ECU 32 as a second control unit that controls the operation of the column actuator 24.

  In the present embodiment, the steering shaft 3 (column shaft 8) is provided with a torque sensor 35 and a steering sensor 36, and the rack ECU 31 and the column ECU 32 have a steering torque τ detected by these sensors, a steering wheel. The angle θs and the steering speed ωs are input. In addition, the vehicle speed V detected by the vehicle speed sensor 37 is input to the rack ECU 31 and the column ECU 32. In the present embodiment, the rack ECU 31 and the column ECU 32 communicate with each other via an in-vehicle network (not shown). Then, the rack ECU 31 and the column ECU 32 calculate a target assist force based on these state quantities, and supply drive power corresponding to the target assist force to the motors 21 and 22. In the present embodiment, brushless motors are employed as the motors 21 and 22 of the rack actuator 23 and the column actuator 24, and the rack ECU 31 and the column ECU 32 have three phases (U, V, W) is supplied. Each rack ECU 31 and column ECU 32 controls the operation so that the corresponding assist force is generated in the corresponding rack actuator 23 and column actuator 24 by supplying the driving power.

Next, an aspect of assist control in the EPS of the present embodiment will be described.
FIG. 2 is a control block diagram of the EPS of this embodiment. Each control block shown below is realized by a computer program executed by microcomputers 41 and 42 described later.

  As shown in the figure, the rack ECU 31 and the column ECU 32 are respectively connected to the microcomputers 41 and 42 that output motor control signals and the motors 21 and 22 that are drive sources of the corresponding actuators based on the motor control signals. Drive circuits 43 and 44 for supplying drive power are provided.

  In the present embodiment, the rack ECU 31 and the column ECU 32 include current sensors 45 and 46 for detecting actual current values I_r and I_c energized to the motors 21 and 22, and the rotation angles θm_r of the motors 21 and 22, respectively. Rotation angle sensors 47 and 48 for detecting θm_c are connected. The microcomputers 41 and 42 are based on the actual current values I_r and I_c and the rotation angles θm_r and θm_c of the motors 21 and 22 detected based on the output signals of these sensors, and the steering torque τ and the vehicle speed V. A motor control signal is output to the drive circuits 43 and 44.

  More specifically, each of the microcomputers 41 and 42 has a current command value calculation unit 51 that calculates current command values I_r * and I_c * corresponding to the target assist force to be generated by the corresponding rack actuator 23 and column actuator 24, respectively. 52, and motor control signal output units 53 and 54 for outputting a motor control signal based on the current command values I_r * and I_c * calculated by the current command value calculation units 51 and 52, respectively.

  In the present embodiment, the current command value calculators 51 and 52 calculate basic assist control components 55 and 56 that calculate basic assist control components Ias_r * and Ias_c *, which are basic control components of the target assist force, and compensation components thereof. Compensation system control units 57 and 58 for calculating Ic_r * and Ic_c *. The basic assist control units 55 and 56 calculate basic assist control components Ias_r * and Ias_c * based on the steering torque τ and the vehicle speed V. Specifically, the basic assist control units 55 and 56 calculate larger basic assist control components Ias_r * and Ias_c * as the detected steering torque τ is larger and the vehicle speed V is smaller. On the other hand, in addition to the steering torque τ and the vehicle speed V, the steering angle θs and the steering speed ωs are input to the compensation system controllers 57 and 58. The compensation system controllers 57 and 58 Compensation components Ic_r * and Ic_c * are calculated by executing various compensation controls based on each state quantity. The current command value calculation units 51 and 52 are compensated for by the basic assist control components Ias_r * and Ias_c * calculated by the basic assist control units 55 and 56, respectively. By superimposing Ic_r * and Ic_c *, current command values I_r * and I_c * as target assist forces are calculated and output to the motor control signal output units 53 and 54, respectively.

  The motor control signal output units 53 and 54 include the current command values I_r * and I_c * output from the current command value calculation units 51 and 52, and the actual current values I_r and I_c detected by the current sensors 45 and 46, respectively. , And rotation angles θm_r and θm_c detected by the rotation angle sensors 47 and 48 are input. Each motor control signal output unit 53, 54 calculates a motor control signal by executing feedback control so that the actual current values I_r, I_c follow the current command values I_r *, I_c * corresponding to the target assist force. This is output to the drive circuits 43 and 44.

  Specifically, in the present embodiment, the motor control signal output units 53 and 54 indicate the phase current values (Iu, Iv, Iw) of the motors 21, 22 detected as the actual current values I_r, I_c, d. The current feedback control is performed by converting into d and q axis current values in the / q coordinate system (d / q conversion).

  That is, the current command values I_r * and I_c * are input to the motor control signal output units 53 and 54 as q-axis current command values, and the motor control signal output units 53 and 54 are rotated by the rotation angle sensors 47 and 48, respectively. Each phase current value (Iu, Iv, Iw) is d / q converted based on the detected rotation angles θm_r, θm_c. The motor control signal output units 53 and 54 calculate the d and q axis voltage command values based on the d and q axis current values and the q axis current command value. Then, each phase voltage command value (Vu *, Vv *, Vw *) is calculated by performing d / q reverse conversion on the d and q axis voltage command values, and a motor control signal is calculated based on the phase voltage command values. Is generated.

  In the rack ECU 31 and the column ECU 32, the microcomputers 41 and 42 output the motor control signals calculated in the motor control signal output units 53 and 54 to the drive circuits 43 and 44, respectively. However, by supplying three-phase drive power based on the motor control signal to the motors 21 and 22, the operation of the corresponding actuators is controlled.

  As described above, in an EPS having two motors as a drive source, it is an important issue to suppress mutual interference between these two motor controls and the accompanying deterioration in steering feeling.

  In consideration of this point, in the EPS 1 of the present embodiment, the rack ECU 31 and the column ECU 32 do not perform the same compensation control as the compensation control performed on the other side. That is, the mutual interference of the motor control tends to become remarkable when the compensation control is executed. Therefore, the present embodiment is configured to suppress the occurrence of such mutual interference by not performing the same compensation control as that performed on the other side.

  More specifically, in the present embodiment, the compensation system control unit 57 on the rack ECU 31 (microcomputer 41) side includes a torque inertia compensation control unit 61, while the compensation system control unit 58 on the column ECU 32 (microcomputer 42) side performs steering. A return compensation control unit 62 and a damper compensation control unit 63 are provided.

  Here, “torque inertia compensation control” is a control that compensates for the effects of EPS inertia, such as motors and actuators, and specifically, “feeling of catching (following delay)” when “starting to cut” in steering operation. ”And“ flow feeling (overshoot) ”at the time of“ cutting end ”. Further, “steering return compensation control” is compensation control for smooth return to the neutral position of the steering, and “damper compensation control” is compensation control for suppressing steering wobbling.

  In this embodiment, each of these compensation controls is executed only on one side of the rack ECU 31 or the column ECU 32 as described above, thereby suppressing the occurrence of mutual interference in motor control. .

  More specifically, in the present embodiment, in the compensation system control unit 57 on the rack ECU 31 (microcomputer 41) side, the torque inertia compensation control unit 61 includes the differential value of the steering torque τ (steering torque differential value dτ) and the vehicle speed V. Is entered. The torque inertia compensation control unit 61 executes the torque inertia compensation control based on the steering torque differential value dτ and the vehicle speed V.

  Specifically, as shown in FIG. 3, the torque inertia compensation control unit 61 of the present embodiment includes a map 61a in which the steering torque differential value dτ and the basic compensation amount εti are associated, the vehicle speed V, and the interpolation coefficient α. Is associated with the map 61b. In the map 61a, the basic compensation amount εti is a value that increases the basic assist control component Ias_r * (absolute value) calculated by the basic assist control unit 55 as the absolute value of the input steering torque differential value dτ increases. It is set to become. Further, in the map 61b, the interpolation coefficient α is set so as to increase as the vehicle speed V increases in the low vehicle speed region, and to decrease as the vehicle speed increases in the high vehicle speed region. Then, the torque inertia compensation control unit 61 calculates the torque inertia compensation component Iti * by multiplying the basic compensation amount εti and the interpolation coefficient α obtained by referring to these maps 61a and 61b.

Then, the compensation system control unit 57 outputs the torque inertia compensation component Iti * as the compensation component Ic_r *.
On the other hand, as shown in FIG. 2, in this embodiment, in the compensation system control unit 58 on the column ECU 32 (microcomputer 42) side, the steering angle θs and the vehicle speed V are input to the steering return compensation control unit 62, and damper compensation is performed. The control unit 63 receives the steering speed ωs and the vehicle speed V. Then, the steering return compensation control unit 62 executes steering return compensation based on the steering angle θs and the vehicle speed V, and the damper compensation control unit 63 executes damper compensation control based on the steering speed ωs and the vehicle speed V. .

  Specifically, as shown in FIG. 4, the steering return compensation control unit 62 of the present embodiment associates a map 62a in which the steering angle θs and the basic compensation amount εsb are associated with each other, the vehicle speed V and the vehicle speed gain K1. Map 62b. In the map 62a, the basic compensation amount εsb becomes a value that further decreases the basic assist control component Ias_c * (absolute value) calculated by the basic assist control unit 55 as the absolute value of the input steering angle θs increases. Is set to In the present embodiment, in the map 62a, a dead zone is set near the steering neutral position where the steering angle θs (absolute value) is small. In the map 62b, the vehicle speed gain K1 is set so as to decrease as the vehicle speed V increases. Then, the steering return compensation control unit 62 calculates a steering return compensation component Isb * by multiplying the basic compensation amount εsb and the vehicle speed gain K1 obtained by referring to these maps 62a and 62b.

  As shown in FIG. 5, the damper compensation control unit 63 of the present embodiment includes a map 63a in which the steering speed ωs and the basic compensation amount εdp are associated, and a map 63b in which the vehicle speed V and the vehicle speed gain K2 are associated. And. In the map 63a, the basic compensation amount εdp is a value that further decreases the basic assist control component Ias_c * (absolute value) calculated by the basic assist control unit 55 as the absolute value of the input steering speed ωs increases. Is set to In this embodiment, in the map 63a, a dead zone is set in a region where the steering speed ωs (absolute value) is small. In the map 63b, the vehicle speed gain K2 is set so as to increase as the vehicle speed V increases. Then, the damper compensation control unit 63 calculates the damper compensation component Idp * by multiplying the basic compensation amount εdp and the vehicle speed gain K2 obtained by referring to these maps 63a and 63b.

  Then, the compensation system control unit 58 of the present embodiment superimposes the steering return compensation component Isb * calculated by the steering return compensation control unit 62 and the damper compensation component Idp * calculated by the damper compensation control unit 63. To calculate the compensation component Ic_c *.

As described above, according to the present embodiment, the following operations and effects can be obtained.
(1) The EPS 1 includes a rack ECU 31 that controls the operation of the rack actuator 23 and a column ECU 32 that controls the operation of the column actuator 24. The rack ECU 31 and the column ECU 32 (each of the microcomputers 41 and 42) superimpose the compensation components Ic_r * and Ic_c * calculated by the compensation control on the basic assist control components Ias_r * and Ias_c *, respectively. Current command values I_r * and I_c * are calculated. The rack ECU 31 and the column ECU 32 do not perform the same compensation control as that performed on the other side.

  That is, the mutual interference of the motor control tends to become remarkable when the compensation control is executed. Therefore, unlike the above configuration, the occurrence of such mutual interference can be suppressed by not performing the same compensation control as that performed on the other side. As a result, a good steering feeling can be ensured.

(2) The rack ECU 31 (microcomputer 41) executes torque inertia compensation control, and the column ECU 32 (microcomputer 42) does not execute the torque inertia compensation control.
That is, the torque inertia compensation control is a control that compensates for the influence of the inertia of the EPS, such as a motor or an actuator, and at the time of “start of cutting” in steering operation, “feeling of being caught (following delay)” and This is executed for the purpose of suppressing “flow feeling (overshoot)”. Therefore, it is desirable to carry out the control of the rack actuator 23 closer to the steered wheel 12, and this can suppress the occurrence of the mutual interference without reducing the effect of the torque inertia compensation control.

(3) The column ECU 32 executes the steering return compensation control, and the rack ECU 31 does not execute the steering return compensation control.
In other words, the steering return compensation control is compensation control for smooth return to the neutral position of the steering. Therefore, it is desirable to carry out the control of the column actuator 24 closer to the steering 2, whereby the occurrence of the mutual interference can be suppressed without reducing the effect of the steering return compensation control.

(4) The column ECU 32 executes damper compensation control, and the rack ECU 31 does not execute the damper compensation control.
That is, the damper compensation control is compensation control for suppressing the fluctuation of the steering 2. Therefore, it is desirable to perform the control in the column actuator 24 closer to the steering 2, whereby the occurrence of the mutual interference can be suppressed without reducing the effect of the damper compensation control.

In addition, you may change this embodiment as follows.
In the present embodiment, the EPS 1 includes a rack ECU 31 as a first control unit that controls the operation of the rack actuator 23 and a column ECU 32 as a second control unit that controls the operation of the column actuator 24. . However, the present invention is not limited to this, and the present invention may be applied to a configuration in which the rack actuator 23 and the column actuator 24 are controlled by one ECU. That is, the first and second control means do not need to be physically separate.

  In this embodiment, the compensation system control unit 57 on the rack ECU 31 (microcomputer 41) side includes a torque inertia compensation control unit 61, while the compensation system control unit 58 on the column ECU 32 (microcomputer 42) side performs steering return compensation control. The unit 62 and the damper compensation control unit 63 are provided. However, the present invention is not limited to this, and the present invention may be applied to a configuration in which steering return compensation control and damper compensation control are performed on the rack ECU 31 side, or a configuration in which torque inertia compensation control is performed on the column ECU 32 side. That is, any configuration that does not perform the same compensation control as the compensation control performed on the other side may be used.

Further, even if both the rack ECU 31 and the column ECU 32 have the same compensation control calculation unit, it is not necessary to simultaneously perform the same compensation control as the compensation control performed on the other side.
-Furthermore, the applied compensation control is not limited to torque inertia compensation, steering return compensation control, and damper compensation control. Similarly, other various compensation controls such as friction compensation control are also performed on the other side. The same compensation control may not be performed.

  In the present embodiment, the present invention is embodied in EPS 1 including a column actuator 24 that applies assist force to the column shaft 8 as a steering force assisting device that applies assist force to the steering shaft 3. However, the present invention is not limited to this, and the steering force assisting device that applies assist force to the steering shaft 3 may be embodied with a pinion-type EPS actuator that applies assist force to the pinion shaft.

The schematic block diagram of an electric power steering device (EPS). The control block diagram of EPS. The control block diagram of a torque inertia compensation control part. The control block diagram of a steering return control part. The control block diagram of a damper compensation control part.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering device (EPS), 2 ... Steering, 3 ... Steering shaft, 5 ... Rack shaft, 8 ... Column shaft, 10 ... Pinion shaft, 12 ... Steering wheel, 21, 22 ... Motor, 23 ... Rack actuator, 24 ... column actuator, 31 ... rack ECU, 32 ... column ECU, 41, 42 ... microcomputer, 51, 52 ... current command value calculation unit, 55, 56 ... basic assist control unit, 57, 58 ... compensation system control unit, 61 ... torque inertia compensation control unit, 62 ... steering return compensation control unit, 63 ... damper compensation control unit, I_r *, I_c * ... current command value, Ias_r *, Ias_c * ... basic assist control component, Ic_r *, Ic_c * ... compensation Component, Iti * ... torque inertia compensation component, Isb * ... steering return compensation component, Idp * ... damper compensation component.

Claims (4)

A first steering force assisting device provided to apply an assist force for assisting a steering operation to the rack shaft; a second steering force assisting device provided to apply the assist force to the steering shaft; First and second control means for controlling the operation of each steering force assisting device by supplying driving power to the first and second motors which are the driving sources of the corresponding steering force assisting devices; , And first and second current sensors for detecting actual current values energized to the first and second motors, respectively, and the first and second control means include various types of basic assist components. by superimposing a computed compensation component by the compensation control, by calculating the current command value as a target assist force to be generated in the corresponding said each steering force assist device, follow the actual current value to the current command value The electric power steering apparatus for performing feedback control of each in order to,
The first and second control means do not simultaneously perform the same compensation control as the other;
An electric power steering device. The electric power steering apparatus according to claim 1, wherein
The first control means corresponding to the first steering force assisting device performs torque inertia compensation control for compensating for the influence of the inertia of the steering force assisting device, and corresponds to the second steering force assisting device. The second control means does not perform the torque inertia compensation control;
An electric power steering device. The electric power steering apparatus according to claim 1, wherein
The second control means corresponding to the second steering force assisting device performs steering return compensation control for smooth return to the neutral position of the steering, and the first steering force assisting device The corresponding first control means does not perform the steering return compensation control. The electric power steering apparatus according to claim 1, wherein
The second control means corresponding to the second steering force assisting device performs damper compensation control for suppressing steering fluctuation, and the first control means corresponding to the first steering force assisting device. Do not perform the damper compensation control,
An electric power steering device.

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