JP4747883B2 - Target detection apparatus and target detection method - Google Patents

Description

  The present invention relates to a target detection apparatus and target detection method for detecting a target using electromagnetic waves.

  Conventionally, as a technique for controlling a vehicle such as a four-wheeled vehicle, a technique for detecting a target using a radar is known. In this technique, it is common to detect a target using a main lobe having a large gain. However, when the target is detected using only the main lobe, there is a problem that a blind area is generated.

  Therefore, a target detection technique using side lobes in addition to the main lobe is disclosed as a technique that does not generate blind areas and does not detect unnecessary targets (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 6-18657

  However, if the normal threshold level set for the main lobe region is applied to the side lobe region where the gain is low or the region where the main lobe gain is low, the peak frequency of the target can be almost detected because the gain is too low. There were cases where it was not possible.

  On the other hand, if the normal threshold level set for a predetermined region of the main lobe is simply lowered according to the side lobe region or the low gain region of the main lobe, the main body of the main lobe should be detected. Many unnecessary targets will be detected in the area.

  The present invention has been made in view of the above, and an object of the present invention is to provide a target detection device and a target detection method capable of widening the detection area of a target while maintaining the original detection sensitivity. And

In order to solve the above-described problems and achieve the object, a target detection apparatus according to the present invention transmits a signal wave and detects a target by receiving a reflected wave of the transmitted signal wave. A detection device that detects a target existing in a first detection region when the intensity of the signal wave is equal to or greater than a first threshold, and a second that has an intensity of the signal wave smaller than the first threshold. It is characterized by comprising detection means for detecting a target existing in a second detection area that is wider than the first detection area and includes the first detection area when it is equal to or greater than a threshold value.

In the target detection apparatus according to the present invention, in the above invention, the first detection area is set centering on a transmission direction of the signal wave, and the second detection area is a signal transmitted more than the first detection area. It is characterized by being a region where the intensity of is small.

In the above-described invention, the target detection apparatus according to the present invention is based on the magnitude relationship between the peak value of the intensity of the reflected wave reflected by the target and the first and second threshold values. The apparatus further comprises first target tracking processing means for tracking movement from the first detection area to the second detection area.

In the above-described invention, the target detection apparatus according to the present invention captures an image in a third detection region including the second detection region, and uses the captured image to detect a target present in the third detection region. An image detecting means for detecting an image target is further provided.

In the above-described invention, the target detection apparatus according to the present invention is the magnitude relationship between the peak value of the intensity of the reflected wave reflected by the target and the first and second threshold values, and the target and the image detection. And second target tracking processing means for tracking the movement of the target from the second detection area to the first detection area based on the relationship with the target detection width of the image target detected by the means. It is characterized by that.

A target detection method according to the present invention is a target detection method for detecting a target by transmitting a signal wave and receiving a reflected wave of the transmitted signal wave, wherein the intensity of the signal wave is first. When a target existing in the first detection region is detected when it is equal to or larger than the threshold value, and the intensity of the signal wave is equal to or larger than a second threshold value smaller than the first threshold value, the target area is wider than the first detection region. A target existing in a second detection area including the first detection area is detected.

In the target detection method according to the present invention, in the above invention, the first detection region is set centering on a transmission direction of the signal wave, and the second detection region is a signal transmitted more than the first detection region. It is characterized by being a region where the intensity of is small.

In the above-described invention, the target detection method according to the present invention is based on the magnitude relationship between the peak value of the intensity of the reflected wave reflected by the target and the first and second threshold values. The movement from the first detection area to the second detection area is tracked.

In the target detection method according to the present invention, in the above invention, an image is captured in a third detection region including the second detection region, and a target existing in the third detection region is detected using the captured image. It is detected as an image target.

In the target detection method according to the present invention, in the above invention, the magnitude relationship between the peak value of the intensity of the reflected wave reflected by the target and the first and second threshold values, and the target and the image object are described. The movement of the target from the second detection area to the first detection area is tracked based on the relationship with the target detection width of the target.

  According to the present invention, when detecting a target by transmitting a signal wave and receiving a reflected wave of the transmitted signal wave, the first detection region when the intensity of the signal wave is greater than or equal to a first threshold value. A second detection area that includes the first detection area wider than the first detection area when the intensity of the signal wave is equal to or greater than a second threshold that is smaller than the first threshold. By providing the detection means for detecting the target existing in the target, it is possible to widen the detection area of the target while maintaining the original detection sensitivity.

  The best mode for carrying out the present invention (hereinafter referred to as “embodiment”) will be described below with reference to the accompanying drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a functional configuration of the target detection apparatus according to Embodiment 1 of the present invention. A target detection apparatus 1 shown in the figure is an apparatus that is mounted on a vehicle such as a four-wheeled vehicle and detects an object that exists in a predetermined range around the vehicle. The target detection apparatus 1 includes a millimeter wave radar 2 that detects a target in a predetermined range using millimeter waves, and an arithmetic operation that detects a target using a signal output from the millimeter wave radar 2. Unit 3 and a storage unit 4 for storing calculation results and various setting information in the calculation unit 3.

Millimeter-wave radar 2, while sending the millimeter wave in a predetermined range from the transmitting antenna, receives a reflected wave from a target by receiving antenna (also the same if the transmitting antenna), the filtering of the received reflected wave And signal processing such as A / D conversion. As the millimeter wave radar 2, a commonly used method such as an FMCW (Frequency Modulated Continuous Wave) method can be applied.

  The calculation unit 3 detects a target using a signal received by the millimeter wave radar 2 and a target tracking that tracks a target existing in a predetermined area based on a detection result of the detection unit 31. And a processing unit 32 (first target tracking processing means). The calculation unit 3 is realized using a CPU (Central Processing Unit) or the like, and reads various calculation processing programs from the storage unit 4 to execute processing corresponding to the read program.

  The storage unit 4 is realized using a ROM (Read Only Memory) in which an arithmetic processing program is recorded and a RAM (Random Access Memory) that stores various parameters and data.

The target information detected by the target detection device 1 is output to the vehicle control device 5. The vehicle control device 5 performs control such as inter-vehicle distance control and automatic brake control in accordance with the output from the target detection device 1. Thus, the target detection device 1 and the vehicle control device 5 constitute a system such as ACC (inter-vehicle control device), PBA (pre-crash brake assist), PSB (pre-crash seat belt) as a whole. In this sense, the target detection device 1 has a function as a sensor.

FIG. 2 is a diagram schematically showing the relationship between the reception level and the direction of the millimeter wave radar 2. . A curve L shown in the upper part of the figure schematically shows the directivity of the antenna (directional antenna) provided in the millimeter wave radar 2 when the vertical axis P is the reception level and the horizontal axis θ is the direction. Is. In the lower part of the figure, a vehicle C ₀ on which the target detection device 1 is mounted and a detection area of the vehicle C ₀ are shown. In the first embodiment, the reception level P ₁ that does not include the end portion of the main lobe L _m is the same normal threshold value (first threshold value) as the conventional _one, but in addition to this threshold value P ₁ , the main lobe L _m The reception level P ₂ (<P ₁ ) including the region near the boundary with the side lobe L _S is set as the low threshold (second threshold).

The detection area D ₁ (first detection area) at the normal threshold value P ₁ has an azimuth angle of Δθ ₁ , whereas the detection area D ₂ (second detection area) at the low threshold value P ₂ has an azimuth angle. Is Δθ ₂ (> Δθ ₁ ). Therefore, by setting a threshold value lower than the normal threshold value P ₁ and enabling reception of millimeter waves up to the level of the low threshold value P ₂ , the detection area can be detected only by software setting change processing without changing hardware. Can be widened.

If Figure 3, among the processing performed by the target detection device 1 object having the above configuration, the target (e.g., preceding vehicle C ₁ shown in FIG. 2) goes escaped away to undetectable region from the detection area, It is a flowchart which shows the outline | summary of the detachment target tracking process which tracks the target (tracking). The flowchart shown in FIG. 3 shows the flow of processing performed in one detection cycle. That is, in the actual target detection process, the target is detected by repeatedly executing a series of processes shown in FIG. 3 at a predetermined period.

First, when the target is not detected with the normal threshold value P ₁ (No in step S1), it is determined whether or not the extrapolation processing number with the normal threshold value P ₁ is a predetermined number or more (step S2). If the number of extrapolation processes is equal to or greater than the predetermined number (Yes in step S2), the target is treated as lost. At that time, it is determined whether or not the peak value of the target treated as lost is equal to or higher than the low threshold P ₂ (step S3). As a result of this determination, if the peak value of the target is greater than or equal to the low threshold (Yes in step S3), the low threshold target detection flag is turned on (step S4). Thereafter, the target corresponding to the low threshold target is tracked (step S5). The extrapolation process at this time is the same as the extrapolation process at the normal threshold value P ₁ . In addition, the number of extrapolations to be handled as the target lost can be arbitrarily set.

  In addition, when the target is detected in Step S1 (Yes in Step S1), the number of extrapolation processes has not reached the predetermined number in Step S2 (No in Step S2), and the peak value of the target is less than the low threshold value. If (No in step S3), the process in the cycle ends.

FIG. 4 is a diagram illustrating an example of the leaving target tracking process described above. Specifically, the preceding vehicle C ₁ is detected from the detection area D ₁ at the normal threshold P ₁ to the detection area D at the low threshold P _2. It is a figure which shows typically the condition which leaves | separates to _2. FIG. Position of the preceding vehicle C ₁ to 4 indicated by a broken line is a position corresponding to the target a1. FIG. 5 is a diagram in which the departure tracking processing of the preceding vehicle C ₁ shown in FIG. 4 is arranged in time series. The case shown in these figures, the outer interpolation number until the normal threshold P ₁ and the low threshold P ₂ together target lost handle indicates the case of two times. That is, both the normal threshold target (displayed with a circle) and the low threshold target (displayed with a square) represent the targets obtained by extrapolation.

Each cycle will be described. In the first cycle, the normal threshold target a1 is detected (step S1), and in the second and third cycles, the normal threshold targets a2 and a3 are extrapolated. When the third cycle is completed, the number of extrapolation of the normal threshold target has reached the predetermined value 2, so that the target to be tracked is treated as lost (step S2). Thereafter, since the peak value is equal to or higher than the low threshold P ₂ (step S3), the low threshold target detection flag is turned ON (step S4), and the low threshold target tracking process is started. As shown in FIG. 5, the detection area D ₁ with the normal threshold value P ₁ is narrower than the detection area D _{2 with} the low threshold value P ₂ , so that a low threshold value is always required when a normal threshold target is detected. A target is also detected.

The fourth to eighth cycles are low threshold target detection processing (step S5). In the case shown in FIGS. 4 and 5, low threshold targets b4, b5, and b6 are sequentially detected in 4 to 6 cycles, while the target after extrapolation of low threshold targets b7 and b8 from the seventh cycle is Absent. This is because the preceding vehicle C ₁ has moved outside the detection area D ₂ of the low threshold target.

Conventionally, for targets detected in the low-gain region of the side lobe region or main lobe of the directional antenna that the millimeter wave radar 2 has, the target is detected with a lower threshold value than the conventional one. Unnecessary targets and incorrect targets may be detected, and the reliability is low. On the other hand, in the first embodiment, by tracking the target in the normal threshold detection region for the vehicle that is leaving, the target is reliably detected up to the wide-angle area without degrading the target detection accuracy. be able to. As a result, it is possible to track the vehicle leaving the detection area D ₁ without losing it, and to realize highly responsive vehicle control with high responsiveness.

Further, in the detection area for the low gain region of the sidelobe region and the main lobe, the target object separately set a low threshold P ₂ lower than the normal threshold value P ₁ from the normal threshold P ₁ that is conventionally set By searching, the detection area of the millimeter wave radar 2 can be widened only by changing the software without changing the hardware configuration of the antenna or the like.

  According to Embodiment 1 of the present invention described above, when a target is detected by transmitting a signal wave and receiving a reflected wave of the transmitted signal wave, the intensity of the signal wave is a first threshold value. A target existing in the first detection region is detected at the above time, and the first detection region is wider than the first detection region when the intensity of the signal wave is equal to or larger than a second threshold value smaller than the first threshold value. By providing the detection means for detecting the target existing in the second detection area including the detection area, it is possible to widen the detection area of the target while maintaining the original detection sensitivity.

(Embodiment 2)
FIG. 6 is a block diagram showing a functional configuration of the target detection apparatus according to Embodiment 2 of the present invention. The target detection apparatus 11 shown in the figure captures an image within a predetermined field of view using a millimeter wave radar 2 having the same configuration as the target detection apparatus 1 according to the first embodiment, and uses the captured image. Then, a fusion target is generated by fusing the image sensor 6, which is an image detection means for detecting the image target, and the millimeter wave radar target and the image target, and target tracking processing is performed using this fusion target. And a storage unit 4.

  The calculation unit 7 performs a fusion processing to generate a fusion target, and a target tracking processing unit 72 (second object) for tracking a target existing in a predetermined area using the fusion target. Mark tracking processing means).

FIG. 7 is a diagram schematically showing detection areas of the millimeter wave radar 2 and the image sensor 6. As shown in the figure, the detection area D ₃ (third detection area) of the image sensor 6 coincides with the detection area D ₂ of the low threshold level of the millimeter wave radar 2 or is wider than the detection area D ₂ ( FIG. 7 shows the latter case).

FIG. 8 is a flowchart showing an overview of an interrupt target detection process in the case where a preceding vehicle has interrupted in front of a vehicle traveling on a road. The flowchart shown in the figure shows the flow of processing performed in one detection cycle. In the actual processing, the series of processing shown in FIG. 8 is repeated at a predetermined cycle. First, if the low-threshold P ₂ were detected target objects (at step S11 Yes), the millimeter wave low threshold target object is detected whether present within the range of image objects detected width (step S12). FIGS. 9-1 to 9-3 are diagrams illustrating a case where a millimeter wave low threshold target exists within the range of the image target detection width in the processing of step S12 (Yes in step S12). In these drawings, H-shaped regions IP _{1 to} IP ₃ represent image target detection widths, and a square region MP represents a millimeter wave target.

  As shown in FIGS. 9-1 to 9-3, when a millimeter wave target exists within the range of the image target detection width (Yes in step S12), the image flag is turned ON (step S13). In this case, thereafter, the interrupt flag is set to ON (step S15), and the low threshold target is registered as an interrupt target (target whose interrupt flag is ON) (step S16). On the other hand, when the millimeter wave target does not exist within the range of the image target detection width (No in step S12), the image flag is turned off (step S14), and the interrupt flag is turned on (step). S15). Thereafter, an interrupt target is registered as a low threshold target (step S16).

  By the way, in the interrupt target detection process described above, the interrupt flag is set ON regardless of whether the image flag is ON / OFF. However, when the vehicle control device 5 performs control based on the interrupt target information. Is set so as to perform processing based on the premise that the reliability of the low-threshold target is different depending on ON / OFF of the image flag. In other words, the low-threshold target is a target with low reliability by itself, but the control is performed on the premise that the reliability is improved by setting the image flag (ON). That's fine.

  FIG. 10 is a flowchart showing an overview of the interrupt target tracking process for tracking the interrupt target detected by the interrupt target detection process. FIG. 10 also shows the flow of processing performed in one detection cycle as in FIG. 8. In the actual processing, the series of processing shown in FIG. 10 is repeated at a predetermined cycle. First, it is determined whether or not the millimeter wave low threshold is detected as an interrupt target in step S21. If the millimeter wave low threshold is being detected as an interrupt target (Yes in step S21), the millimeter wave low threshold target is detected. It is determined whether the peak value is equal to or greater than the normal threshold (step S22). As a result of this determination, if the peak value of the millimeter-wave low threshold target is equal to or greater than the normal threshold value (Yes in step S22), it means that the vehicle has entered the normal threshold region, so the interrupt flag is turned OFF (step S23), the detected target is registered as a normal threshold target (step S24). On the other hand, when the millimeter wave low threshold is not detected as an interrupt target (No in step S21), or when the peak value of the millimeter wave low threshold target is equal to or less than the normal threshold (No in step S22), processing is performed. Exit.

FIG. 11 is a diagram showing an example of the process from the interrupt target detection process described above to the interrupt target tracking process. Specifically, the preceding vehicle C ₁ is in the detection area D ₃ of the image sensor 6. it is a diagram illustrating a situation where the incoming interrupt the inside of the detection area D ₁ from the outside through the detection region D ₂ (substantially forward direction of the vehicle C _0). Position of the preceding vehicle C ₁ indicated by a broken line in FIG. 11 is a position when it detects the target c1. FIG. 12 is a diagram in which the interrupt tracking processing of the preceding vehicle C ₁ shown in FIG. 11 is arranged in time series.

Each cycle will be described. In the first cycle, a low threshold target object in the detection region D ₂ of the low threshold target object in accordance with the above-described interrupt target object detection processing is detected and registered as an interrupt target object. Thereafter, until the fourth cycle, it is detected as a low threshold target (interrupt flag ON). During this time, if a low threshold target exists in the image target detection width detected by the image sensor 6 (see FIGS. 9-1 to 9-3), the image flag is turned ON.

In the fifth cycle, target detection region D ₁ come to enter the interior of the normal threshold. As a result, the interrupt flag is turned off and registered as the normal threshold target d5. Thereafter, normal threshold targets d6, d7, and d8 are sequentially registered up to the eighth cycle (omitted after the ninth cycle).

In this way, for a target that is interrupted from the outside of the detection area D ₃ , the target is detected and determined based on the result of the sensor fusion process to which the information of the image sensor 6 is added. It becomes possible to detect the target early. This makes it possible to realize highly responsive and smooth vehicle control with high responsiveness.For example, an alarm is issued from an earlier stage to a vehicle that is likely to collide, and seat belt control, brake control, etc. Will be able to start with.

  The leave tracking process may be performed in the same manner as in the first embodiment. In this sense, the target tracking processing unit 72 also has a function as first target tracking processing means.

  According to the second embodiment of the present invention described above, when a target is detected by transmitting a signal wave and receiving a reflected wave of the transmitted signal wave, the intensity of the signal wave is a first threshold value. A target existing in the first detection region is detected at the above time, and the first detection region is wider than the first detection region when the intensity of the signal wave is equal to or larger than a second threshold value smaller than the first threshold value. By providing detection means for detecting a target existing in the second detection area including the detection area, the detection area of the target is widened while maintaining the original detection sensitivity as in the first embodiment. It becomes possible.

  Further, according to the second embodiment, by performing sensor fusion processing to which image sensor information is added, it becomes possible to detect a vehicle that has entered from outside the detection region of the millimeter wave radar at an early stage, thereby further safety. A system that supports smooth driving can be realized.

(Other embodiments)
Up to this point, the first and second embodiments have been described in detail as the best mode for carrying out the present invention, but the present invention should not be limited only by these two embodiments. For example, two millimeter wave radars may be provided as detection means. In this case, it is possible to realize more accurate target detection while complementing each other by using one of the millimeter-wave radars using the long-distance narrow-angle DBF method and the other using the short-distance monopulse-type millimeter-wave radar. it can.

  Further, the combination in the case of using two detection means is not necessarily limited to the above-described combination of millimeter wave radars, and any one is a high-resolution radar and the detection areas of the two radars are different. A type of radar may be applied.

  Thus, the present invention can include various embodiments and the like not described herein, and various design changes and the like can be made without departing from the technical idea specified by the claims. It is possible to apply.

It is a block diagram which shows the function structure of the target detection apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows typically the relationship between the reception level and azimuth | direction of millimeter wave radar with which the target detection apparatus which concerns on Embodiment 1 of this invention is provided. It is a flowchart which shows the outline | summary of the detachment target tracking process which the target detection apparatus which concerns on Embodiment 1 of this invention performs. It is a figure which shows the specific example of a detachment target tracking process. FIG. 5 is a diagram in which departure tracking processing illustrated in FIG. 4 is arranged in time series. It is a block diagram which shows the function structure of the target detection apparatus which concerns on Embodiment 2 of this invention. It is a figure which shows typically the detection area of a millimeter wave radar and an image sensor. It is a flowchart which shows the outline | summary of the interrupt target detection process which the target detection apparatus which concerns on Embodiment 2 of this invention performs. It is a figure which shows the example (1st example) in case a millimeter-wave low threshold target exists in the range of an image target detection width. It is a figure which shows the example (2nd example) in case a millimeter-wave low threshold target exists in the range of an image target detection width. It is a figure which shows the example (3rd example) in case a millimeter-wave low threshold target exists in the range of an image target detection width. It is a flowchart which shows the outline | summary of the interrupt target tracking process which the target detection apparatus which concerns on Embodiment 2 of this invention performs. It is a figure which shows an example of the process from an interruption target detection process to an interruption target tracking process. It is the figure which arranged in order from the interruption detection process shown in FIG. 11 to the interruption tracking process in time series.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 11 Target detection apparatus 2 Millimeter wave radar 3, 7 Calculation part 4 Storage part 5 Vehicle control apparatus 6 Image sensor 31 Detection part 32, 72 Target tracking process part 71 Fusion process part C ₀ vehicle C ₁ Predecessor vehicle D ₁ , D ₂ , D ₃ detection area L curve L _m main lobe L _S side lobe

Claims (10)

A target detection device that detects a target by transmitting a signal wave and receiving a reflected wave of the transmitted signal wave,
As a reflected wave from the first detection region, it is possible to receive a reflected wave having a peak value that is equal to or greater than a preset first threshold, and as a reflected wave from the second detection region including the first detection region. , A reflected wave having a peak value smaller than the first threshold and having a peak value equal to or larger than a second threshold preset as a value smaller than the first threshold can be received, and the received reflection the Rukoto with waves, detecting means for repetitively detecting a target in a predetermined cycle,
When the peak value of the reflected wave received from the first detection area is smaller than the first threshold value and the number of extrapolation processes at the first threshold value is a predetermined number or more, a target corresponding to the reflected wave is selected. When the target is treated as lost in the first detection area and the peak value of the target treated as lost is equal to or greater than the second threshold, the low threshold target flag is turned on to turn the target into a low threshold target. A first target tracking means for registering and tracking as a target;
A target detection apparatus comprising:   2. The first detection area is set with a transmission direction of the signal wave as a center, and the second detection area is an area where the intensity of a signal to be transmitted is smaller than that of the first detection area. The target detection apparatus described. Image detecting means for capturing an image in a third detection area including the second detection area and detecting a target existing in the third detection area as an image target using the captured image is further provided. The target detection apparatus according to claim 1 or 2 , characterized in that Detection width of the image target detected by the image detection means when the peak value of the reflected wave reflected by the target is smaller than the first threshold and not less than the second threshold. 4. The apparatus according to claim 3 , further comprising second target tracking means for registering and tracking the target as an interrupt target by turning on an interrupt flag when the target is within the range of Target detection device. The second target tracking means is
When the peak value of the reflected wave corresponding to the interrupt target is equal to or greater than the first threshold, the interrupt flag is turned off, and the target is registered as a normal threshold target for tracking. The target detection apparatus according to claim 4 . A target detection method for detecting a target by transmitting a signal wave and receiving a reflected wave of the transmitted signal wave,
As a reflected wave from the first detection region, it is possible to receive a reflected wave having a peak value that is equal to or higher than a preset first threshold, and as a reflected wave from the second detection region including the first detection region. The reflected wave having a peak value smaller than the first threshold and having a peak value equal to or larger than a second threshold preset as a value smaller than the first threshold can be received, and the received reflected wave the Rukoto used to detect repeatedly the target in a predetermined cycle,
When the peak value of the reflected wave received from the first detection area is smaller than the first threshold value and the number of extrapolation processes at the first threshold value is a predetermined number or more, a target corresponding to the reflected wave is selected. When the target is treated as lost in the first detection area and the peak value of the target treated as lost is equal to or greater than the second threshold, the low threshold target flag is turned on to turn the target into a low threshold target. A target detection method characterized by registering and tracking as a target. Said first detection area, claims are set around the transmission direction of the signal wave, the second detection region is characterized by the intensity of the signal to be transmitted than the first detection area is a small area 6 The described target detection method. Captures an image in the third detection area including the second detection region, claim 6, characterized in that detecting a target existing in said third detection area using the captured image as image object or 7. The target detection method according to 7 . When the peak value of the reflected wave reflected by the target is smaller than the first threshold and not less than the second threshold, the target is within the detection width of the image target. The target detection method according to claim 8 , wherein the target is registered and tracked as an interrupt target by turning on an interrupt flag. When the peak value of the reflected wave corresponding to the interrupt target is equal to or greater than the first threshold, the interrupt flag is turned off, and the target is registered as a normal threshold target for tracking. The target detection method according to claim 9 .

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