JP2022067150A - Steering device - Google Patents

Abstract

To enhance stability of handle return control, by preventing the control from being affected by variation of a flow rate of a pump.SOLUTION: A steering device 100 comprises: a first transmission mechanism (a manual operation mechanism 210) that transmits a rotation of an input shaft (a shaft member 212) connected to a steering member 211 to an output shaft (a pinion shaft 231); a second transmission mechanism (a steering mechanism 230) that transmits a rotation of the output shaft to a steering wheel 220; an electric motor 110 that applies first assist force to the first transmission mechanism; a hydraulic mechanism 240 that applies power of an oil pump 243 as second assist force to the second transmission mechanism; and a motor control part 100 that controls the electric motor 110. The motor control part estimates hydraulic return torque generated by hydraulic pressure, on the basis of flow rate information concerning a flow rate of the oil pump and a steering angular speed of the steering member and estimates return torque on the basis of a vehicle speed of a vehicle and a steering angle of the steering member, and further controls the electric motor on the basis of a difference between the return torque and the hydraulic return torque.SELECTED DRAWING: Figure 3

Description

The present invention relates to a steering device in which a part of the steering force is applied by a hydraulic mechanism and another part of the steering force is applied by an electric motor.

Conventionally known, a hydraulic power steering device that applies assist force to a steering mechanism by supplying hydraulic oil from an oil pump to a power cylinder coupled to a steering mechanism of a vehicle via a hydraulic control valve. ing. For example, the power steering device (steering device) described in Patent Document 1 is a device that applies an assist force to a steering mechanism by an electric motor in addition to an oil pump. In such a steering device, the assist control amount at the time of steering return control according to the steering angle of the steering wheel (steering member) is obtained from the MAP, and the electric motor is controlled so that the control current becomes the control current according to the assist control amount. Return control is performed.

Japanese Unexamined Patent Publication No. 2006-21304

By the way, in the above-mentioned steering wheel return control, since the fluctuation of the pump flow rate due to the oil pump is not taken into consideration, even if the steering wheel return control is performed, the engine speed decreases and the steering wheel return control becomes unstable. There is a risk.

An object of the present invention has been made in view of the above problems, and is to improve the stability of the handle return control by making it less susceptible to fluctuations in the pump flow rate.

In order to achieve the above object, the steering device, which is one of the present inventions, is connected to the steering member, and the input shaft that rotates with the steering operation of the steering member and the output that rotates in conjunction with the rotation of the input shaft. A first transmission mechanism that transmits the rotation of the shaft and input shaft to the output shaft, a second transmission mechanism that transmits the rotation of the output shaft to the steering wheel, and an electric motor that applies the first assist force to the first transmission mechanism. It has an oil pump powered by the engine of the vehicle, and has a hydraulic mechanism that applies the power of the oil pump to the second transmission mechanism as the second assist force, and a motor control unit that controls the electric motor. Of the return torque for returning the steering member to the reference position, the control unit estimates the hydraulic return torque due to hydraulic pressure based on the flow rate information regarding the flow rate of the oil pump and the steering angular speed of the steering member. The return torque is estimated based on the vehicle speed of the vehicle and the steering angle of the steering member, and the electric motor is controlled based on the difference between the return torque and the hydraulic return torque.

According to the present invention, the stability of the handle return control can be improved by making it less susceptible to fluctuations in the pump flow rate.

It is a figure which shows typically the steering apparatus which concerns on embodiment. It is a block diagram which shows the functional structure of the motor control part which concerns on embodiment. It is a block diagram which showed the functional part about return control in the control part which concerns on embodiment. It is explanatory drawing which shows an example of the target steering angle MAP which concerns on embodiment. It is explanatory drawing which shows the return torque MAP which concerns on embodiment. It is explanatory drawing which shows the vehicle speed gain MAP which concerns on embodiment. It is explanatory drawing which shows the torque gain MAP which concerns on embodiment. It is explanatory drawing which shows an example of the hydraulic pressure return torque MAP which concerns on embodiment. It is a figure which shows typically the steering device which concerns on the modification.

Hereinafter, embodiments of the steering device according to the present invention will be described with reference to the drawings. The numerical values, shapes, materials, components, positional relationships of the components, connection states, steps, the order of steps, etc. shown in the following embodiments are examples, and are not intended to limit the present invention. Further, in the following, a plurality of inventions may be described as one embodiment, but the components not described in the claims will be described as arbitrary components with respect to the claimed invention. ing. In addition, the drawings are schematic views in which emphasis, omission, and ratio are adjusted as appropriate to explain the present invention, and may differ from the actual shape, positional relationship, and ratio.

[Steering device]
FIG. 1 is a diagram schematically showing a steering device according to an embodiment. The steering device 200 is a system that steers the steering wheel 220 according to the target steering angle and operates the traveling direction of the vehicle on which the steering device 200 is mounted. The steering device 200 includes a steering mechanism 230, a hydraulic mechanism 240, a manual operation mechanism 210, an electric motor 110, and a motor control unit 100.

The steering mechanism 230 is a mechanism for steering the steering wheel 220, and is an example of the second transmission mechanism according to the present invention. The steering mechanism 230 is not particularly limited, but in the case of the present embodiment, a rack and pinion is adopted. Specifically, the steering mechanism 230 includes a pinion shaft 231, a rack shaft 232, and a tie rod 233.

The pinion shaft 231 is a rod-shaped member provided with a pinion that meshes with the rack provided on the rack shaft 232. The pinion shaft 231 is connected to the electric motor 110, and the torque from the electric motor 110 and the torque from the steering member 211 are applied to rotate the pinion shaft 231 to move the rack shaft 232 in the axial direction of the rack shaft 232. The pinion shaft 231 is an example of an output shaft according to the present invention.

The rack shaft 232 is provided with a rack that meshes with the pinion shaft 231 on a part of the outer peripheral surface, converts the rotation of the pinion shaft 231 into an axial movement amount of the rack shaft 232, and makes the steering wheel 220 via the tie rod 233. It is a member to steer. A hydraulic mechanism 240 is connected to the rack shaft 232, and a part of the steering force for steering the steering wheel 220 by hydraulic pressure, a so-called assist force, is applied. The rack shaft 232 is housed in a rack housing attached to the vehicle body, and the rack housing guides the movement of the rack shaft 232.

The hydraulic mechanism 240 adjusts the hydraulic pressure according to the rotation angle of the pinion shaft 231 and the like, and applies an axial force of the rack shaft 232 to the rack shaft 232 as a part of the steering force. A part of the steering force applied by the hydraulic mechanism 240 is the hydraulic steering force, which is an example of the second assist force. The hydraulic mechanism 240 is not particularly limited, but in the case of the present embodiment, it includes a power cylinder 241, a rotary valve 242, an oil pump 243, and a reservoir tank 244.

The power cylinder 241 includes a cylinder 246 separated into two spaces by a piston 245, and the piston 245 moves in the axial direction of the rack shaft 232 by adjusting the hydraulic pressure of the oil filled in each of the two spaces. .. The piston 245 is connected to the rack shaft 232, and a force in the moving direction is applied from the piston 245 to the rack shaft 232.

The rotary valve 242 is a device that adjusts the hydraulic pressure supplied to each of the two spaces separated by the piston 245. The structure of the rotary valve 242 is not particularly limited, but in the case of the present embodiment, the second torsion bar 282 interposed between the pinion shaft 231 and the motor control unit 100 is provided. The rotary valve 242 supplies the oil pumped from the oil pump 243 to one of the two spaces separated by the piston 245 in response to the relative movement between the inner valve and the outer valve caused by the twist of the second torsion bar 282. The operation of the piston 245 is controlled by adjusting the amount and adjusting the amount of excess oil in the other space to be returned to the reservoir tank 244.

The oil pump 243 is a hydraulic pump powered by an engine provided in a vehicle. The oil in the reservoir tank 244 is supplied to the power cylinder 241 by driving the oil pump 243.

The manual operation mechanism 210 is a device capable of steering the steering wheel 220 by the driver operating the steering member 211 such as the steering wheel. In the case of the present embodiment, as shown in FIG. 1, the manual operation mechanism 210 includes a steering member 211, a shaft member 212, a first torsion bar 281 and a torque detection device 213. The manual operation mechanism 210 may further include a reaction force device, a target steering angle detecting means, and the like.

The shaft member 212 is a rod-shaped member that is mechanically connected to the steering member 211 and rotates in response to a steering operation on the steering member 211. The shaft member 212 is an example of an input shaft according to the present invention. The connection mode between the shaft member 212 and the steering mechanism 230 is not particularly limited. In the case of the present embodiment, the shaft member 212 is mechanically connected to the pinion shaft 231 via the steering shaft body 111. That is, since the rotation of the shaft member 212 is transmitted to the pinion shaft 231 by the manual operation mechanism 210, the pinion shaft 231 rotates in conjunction with the rotation of the shaft member 212. As described above, the manual operation mechanism 210 is an example of the first transmission mechanism according to the present invention.

The first torsion bar 281 is a member that is interposed in the shaft member 212 and twists according to the torque input by the driver operating the steering member 211. The torque detection device 213 detects the amount of twist of the first torsion bar 281 and outputs the steering torque.

The electric motor 110 is a motor that applies a first assist force to the manual operation mechanism 210. Specifically, the electric motor 110 is connected to the shaft member 212 and transmits the rotation of the output shaft of the electric motor 110 to the shaft member 212. The force applied to the shaft member 212 from the electric motor 110 is the first assist force, and the steering force (motor steering force) applied to the steering mechanism 230 by the electric motor 110.

[Motor control unit]
FIG. 2 is a block diagram showing a functional configuration of the motor control unit according to the embodiment. The motor control unit 100 is a portion that controls the electric motor 110 according to the target steering angle, and is one of the ECUs (Electronic Control Units). The motor control unit 100 includes an actual steering angle acquisition unit 130, a target steering angle acquisition unit 131, and a control unit 132 as processing units realized by executing a program.

The actual steering angle acquisition unit 130 acquires the actual steering angle of the steering wheel 220. In the case of the present embodiment, the actual steering angle acquisition unit 130 acquires the actual steering angle based on the signal output by the sensor attached to the steering wheel 220, the link mechanism for steering the steering wheel 220, and the like.

The target steering angle acquisition unit 131 acquires a target steering angle for steering the steering wheel 220. In the case of the present embodiment, the target steering angle acquisition unit 131 acquires the target steering angle from the target steering angle detecting means provided in the manual operation mechanism 210. The target steering angle detecting means is a device that detects the steering angle (rotation angle) of the steering member 211 and outputs it as the target steering angle. For example, the target steering angle detecting means detects the rotation of the shaft member 212 as the rotation of the steering member 211. The type of the target steering angle detecting means is not particularly limited, but for example, a main gear that rotates together with a resolver, a rotary encoder, and a shaft member 212 attached to the electric motor 110, and two driven gears having different diameters that mesh with the main gear. An example of a device provided with a gear and capable of detecting not only the rotation angle of the output shaft but also the rotation direction by detecting the rotation of the permanent magnet provided in each of the driven gears with a Hall element or the like can be exemplified.

The control unit 132 so that the actual steering angle of the actual steering wheel 220 matches the target steering angle based on the target steering angle acquired by the target steering angle acquisition unit 131 and the actual steering angle acquired by the actual steering angle acquisition unit 130. Controls the electric motor 110. In the case of the present embodiment, the electric motor 110 is supplied with electric power by a PWM inverter 260 provided with a plurality of switching elements. The control unit 132 generates a target torque for controlling the electric motor 110 as a motor control value according to the difference between the target steering angle and the actual steering angle. PID control is generally used to generate the target torque. Specifically, the term of the difference between the target steering angle and the actual steering angle, the integral term of the difference, and the derivative term of the difference are multiplied by the proportional gain, the integral gain, and the derivative gain, respectively, and then those terms are added. By doing so, the target torque is calculated as a motor control value.

[Handle return control]
Here, the control unit 132 executes steering wheel return control in order to return the steered steering member 211 to the reference position (neutral position) after steering. Specifically, during the handle return control, the control unit 132 determines the hydraulic pressure return torque due to hydraulic pressure among the return torques for returning the steering member 211 to the reference position based on the flow rate information regarding the flow rate of the oil pump 243. The return torque is estimated based on the vehicle speed of the vehicle and the steering angular velocity of the steering member 211. After that, the control unit 132 controls the electric motor 110 based on the difference between the return torque and the hydraulic pressure return torque (motor return torque).

FIG. 3 is a block diagram showing a functional unit related to return control in the control unit 132 according to the embodiment. The control unit 132 includes a return torque estimation unit 133, a hydraulic pressure return torque estimation unit 134, and a motor control value generation unit 135.

The return torque estimation unit 133 estimates the return torque based on the vehicle speed of the vehicle, the steering angle of the steering member 211, and the steering torque. Specifically, the return torque estimation unit 133 acquires the vehicle speed from the vehicle speed sensor of the vehicle. The return torque estimation unit 133 acquires the steering torque from the torque detection device 213. The return torque estimation unit 133 acquires the steering angle (rotation angle) of the steering member 211 detected by the target steering angle detecting means.

The return torque estimation unit 133 obtains a plurality of MAPs (target steering angle MAP, return torque MAP, vehicle speed gain MAP, torque gain MAP) for estimating the return torque from the acquired vehicle speed, steering angle, and steering torque. I remember.

FIG. 4 is an explanatory diagram showing an example of the target steering angle MAP according to the embodiment. As shown in FIG. 4, the target steering angle MAP is a MAP for estimating the target steering angular velocity from the vehicle speed and the steering angle. Examples of the target steering angle MAP include a MAP having a vehicle speed of 0 km / h, a MAP having a vehicle speed of 20 km / h, a MAP having a vehicle speed of 80 km / h, and a MAP having a vehicle speed of 140 km / h. For example, the return torque estimation unit 133 selects the MAP closest to the vehicle speed acquired from the vehicle speed sensor, and estimates the target point steering angle based on the steering angle acquired at that time. In addition, another vehicle speed may be MAP-ized in the target turning angle MAP.

FIG. 5 is an explanatory diagram showing a return torque MAP according to the embodiment. As shown in FIG. 5, the return torque MAP is a MAP for estimating the return torque based on the target steering angular velocity. The return torque estimation unit 133 estimates the return torque based on the target steering angular velocity estimated based on FIG. 4 and the return torque MAP. The return torque estimated here is the reference return torque.

FIG. 6 is an explanatory diagram showing a vehicle speed gain MAP according to the embodiment. As shown in FIG. 6, the vehicle speed gain MAP is a MAP for estimating the vehicle speed gain based on the vehicle speed of the vehicle. The return torque estimation unit 133 determines the vehicle speed gain based on the vehicle speed of the vehicle and the vehicle speed gain MAP, and integrates the return torque into the reference return torque.

Here, the vehicle speed gain MAP is a MAP for reducing the return torque when the vehicle speed is smaller than a constant value (10 km / h in the present embodiment). That is, when the vehicle speed gain is determined to be a value smaller than 1, the return torque is reduced to the reference return torque because the value is integrated with the reference return torque. If the steering member 211 is returned to the reference position with a large return torque when the vehicle speed is lower than a certain value, the driver may feel uncomfortable. By integrating the vehicle speed gain into the reference return torque and determining the return torque, it is possible to control the steering wheel return with less discomfort.

FIG. 7 is an explanatory diagram showing a torque gain MAP according to the embodiment. As shown in FIG. 7, the torque gain MAP is a MAP for estimating the torque gain based on the steering torque. The return torque estimation unit 133 determines the torque gain based on the steering torque and the torque gain MAP, and integrates the torque gain into the reference return torque (or the reference return torque in which the vehicle speed torque is integrated).

Here, the torque gain MAP is a MAP for reducing the return torque when the steering torque is larger than a constant value (1 Nm in the present embodiment). That is, when the torque gain is determined to be smaller than 1, the return torque is reduced to the reference return torque because the value is integrated with the reference return torque. When the driver operates the steering member 211 and the steering torque becomes larger than a certain value, if a large return torque is applied, the driver may feel uncomfortable. If the torque gain is integrated with the reference return torque to determine the return torque, it is possible to control the steering wheel return with less discomfort.

As shown in FIG. 3, the hydraulic pressure return torque estimation unit 134 estimates the hydraulic pressure return torque due to the hydraulic pressure of the oil pump 243 based on the flow rate information regarding the flow rate of the oil pump 243. Specifically, the hydraulic pressure return torque estimation unit 134 acquires the engine rotation speed from the rotation speed sensor provided in the engine of the vehicle. The flow rate of the oil pump 243 and the rotation speed of the engine have a relationship that the flow rate increases in proportion to the rotation speed. Therefore, the engine speed can be used as the flow rate information without directly detecting the flow rate of the oil pump 243.

Further, the hydraulic return torque estimation unit 134 acquires the steering angle of the steering member 211 detected by the steering angle detecting means, and obtains the steering angular velocity by time-differentiating the steering angle. When the manual operation mechanism 210 is provided with a steering angular velocity sensor that directly detects the steering angular velocity, the hydraulic return torque estimation unit 134 may acquire the steering angular velocity from the steering angular velocity sensor.

The hydraulic pressure return torque estimation unit 134 stores the hydraulic pressure return torque MAP for estimating the hydraulic pressure return torque from the acquired flow rate information and the steering angular velocity.

FIG. 8 is an explanatory diagram showing an example of the hydraulic pressure return torque MAP according to the embodiment. As shown in FIG. 8, the hydraulic pressure return torque MAP is a MAP for estimating the hydraulic pressure return torque from the flow rate information (engine rotation speed) and the steering angular velocity. In this hydraulic return torque MAP, 0-1000 rpm MAP, 1001-2000 rpm MAP, 2001-3000 rpm MAP, 3001-4000 rpm MAP, 4001-5000 rpm MAP, 5001-6000 rpm MAP, 6001-7000 rpm MAP, 7001 -8000 rpm MAP and 8000 rpm or more MAP are listed. For example, the hydraulic pressure return torque estimation unit 134 selects a MAP including the rotation speed acquired from the rotation speed sensor, and estimates the hydraulic pressure return torque based on the steering angular velocity acquired at that time.

As shown in FIG. 3, the difference between the return torque estimated by the return torque estimation unit 133 and the hydraulic pressure return torque estimated by the hydraulic pressure return torque estimation unit 134 is input to the motor control value generation unit 135. This difference is a value excluding the influence of the hydraulic pressure return torque.

The motor control value generation unit 135 calculates a control value (current command value) for controlling the electric motor 110 based on the acquired difference. As a result, the obtained control value is input to the PWM inverter 260 to drive the electric motor 110. Thereby, the electric motor 110 can be controlled by excluding the influence of the hydraulic pressure return torque.

[Effects, etc.]
As described above, according to the present embodiment, in the handle return control, the electric motor 110 is controlled based on the difference between the return torque and the hydraulic pressure return torque, so that the influence of the hydraulic pressure return torque is excluded from the electric motor. 110 can be controlled. The hydraulic pressure return torque reflects the fluctuation of the flow rate of the oil pump 243, but since the influence of this hydraulic pressure return torque is excluded in the handle return control, the fluctuation of the flow rate is not easily affected. Therefore, it is possible to improve the stability of the handle return control.

Further, since the hydraulic pressure return torque estimation unit 134 estimates the hydraulic pressure return torque by using the engine rotation speed as the flow rate information, the hydraulic pressure return torque can be estimated without using the flow sensor that detects the flow rate of the oil pump 243. .. Therefore, it is possible to reduce the manufacturing cost of the steering device 200.

Further, the return torque estimation unit 134 integrates the torque gain based on the steering torque of the steering member 211 with respect to the value (reference return torque) obtained based on the vehicle speed of the vehicle and the steering angle of the steering member 211. Since the return torque is estimated by, it is possible to control the handle return with less discomfort due to the steering torque.

Further, the return torque estimation unit 134 estimates the return torque by integrating the vehicle speed gain based on the vehicle speed with respect to the value (reference return torque) obtained based on the vehicle speed of the vehicle and the steering angle of the steering member 211. Therefore, it is possible to control the steering wheel return with less discomfort due to the vehicle speed.

[others]
The present invention is not limited to the above embodiment. For example, another embodiment realized by arbitrarily combining the components described in the present specification and excluding some of the components may be the embodiment of the present invention. The present invention also includes modifications obtained by making various modifications that can be conceived by those skilled in the art within the scope of the gist of the present invention, that is, the meaning indicated by the wording described in the claims, with respect to the above-described embodiment. Will be.

For example, in the above embodiment, the case where the engine speed is used as the flow rate information has been exemplified. However, it is also possible to adopt the flow rate of the oil pump 243 as the flow rate information. FIG. 9 is a diagram schematically showing a steering device according to a modified example. Specifically, FIG. 9 is a diagram corresponding to FIG. 1. In the following description, the same parts as those in the above embodiment may be designated by the same reference numerals and the description thereof may be omitted.

As shown in FIG. 9, the steering device 200A according to the modified example is provided with a flow rate sensor 290a that directly detects the flow rate of the oil pump 243 on the path of the oil pumped by the oil pump 243. .. The flow rate detected by the flow rate sensor 290a is used as the flow rate information. Specifically, the flow rate detected by the flow rate sensor 290a is input to the hydraulic pressure return torque estimation unit 134. In this case, the hydraulic pressure return torque estimation unit 134 stores the hydraulic pressure return torque MAP for estimating the hydraulic pressure return torque from the acquired flow rate and the steering angle speed, and the flow rate and steering with respect to this hydraulic pressure return torque MAP. The hydraulic pressure return torque is estimated from the angular speed. That is, since the flow rate of the oil pump 243 is directly used, it is possible to estimate the hydraulic pressure return torque more accurately than when the flow rate is estimated from other parameters (for example, the rotation speed of the engine). Therefore, the stability of the handle return control can be further improved.

Further, in the above embodiment, a case where various estimations are performed using each MAP shown in FIGS. 4 to 8 is illustrated. However, each MAP is just an example. That is, each MAP may be set so as to be adapted to various parameters of the steering device, usage conditions, etc. by various experiments, simulations, empirical rules, and the like. It is also possible to execute each estimation by a mathematical formula or the like without using MAP.

The present invention can be used for a steering device that applies an assist force by a hydraulic mechanism and an electric motor.

100 ... motor control unit, 110 ... electric motor, 111 ... steering shaft body, 130 ... actual rudder angle acquisition unit, 131 ... target rudder angle acquisition unit, 132 ... control unit 133 ... return torque estimation unit, 134 ... hydraulic return torque Estimating unit, 135 ... Motor control value generation unit, 200, 200A ... Steering device, 210 ... Manual operation mechanism (first transmission mechanism), 211 ... Steering member, 212 ... Shaft member (input shaft), 213 ... Torque detection device, 220 ... Steering wheel, 230 ... Steering mechanism (second transmission mechanism), 231 ... Pinion shaft (output shaft), 232 ... Rack shaft, 233 ... Tie rod, 240 ... Hydraulic mechanism, 241 ... Power cylinder, 242 ... Rotary valve, 243 ... oil pump, 244 ... reservoir tank, 245 ... piston, 246 ... cylinder, 260 ... inverter, 281 ... first torsion bar, 282 ... second torsion bar, 290a ... flow sensor

Claims (5)

An input shaft that is connected to the steering member and rotates with the steering operation of the steering member,
An output shaft that rotates in conjunction with the rotation of the input shaft,
The first transmission mechanism that transmits the rotation of the input shaft to the output shaft,
A second transmission mechanism that transmits the rotation of the output shaft to the steering wheel,
An electric motor that applies the first assist force to the first transmission mechanism,
A hydraulic mechanism having an oil pump powered by an engine provided in a vehicle and applying the power of the oil pump to the second transmission mechanism as a second assist force.
A motor control unit that controls the electric motor is provided.
The motor control unit
Of the return torque for returning the steering member to the reference position, the hydraulic pressure return torque due to hydraulic pressure is estimated based on the flow rate information regarding the flow rate of the oil pump and the steering angular velocity of the steering member, and is described above. The return torque is estimated based on the vehicle speed of the vehicle and the steering angle of the steering member, and the return torque is estimated.
A steering device that controls the electric motor based on the difference between the return torque and the hydraulic return torque. The steering device according to claim 1, wherein the motor control unit estimates the hydraulic pressure return torque by using the rotation speed of the engine as the flow rate information. A flow sensor for detecting the flow rate of the oil pump is provided.
The steering device according to claim 1, wherein the motor control unit estimates the hydraulic pressure return torque using the detection result of the flow rate sensor as the flow rate information. The motor control unit estimates the return torque by integrating a torque gain based on the steering torque of the steering member with respect to a value obtained based on the vehicle speed of the vehicle and the steering angle of the steering member. The steering device according to any one of claims 1 to 3. The motor control unit estimates the return torque by integrating the vehicle speed gain based on the vehicle speed with respect to the value obtained based on the vehicle speed of the vehicle and the steering angle of the steering member. The steering device according to any one of 4.

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