KR100936444B1 - Vehicle monitoring system and method for controlling the same - Google Patents

Abstract

PURPOSE: A vehicle monitoring system and method for controlling the same are provided to perform immediate measure when abnormality generate in the car sensor. CONSTITUTION: The camera part(20) takes a photograph of the set area including the vehicles. The loop sensor(30) senses the vehicles. The image detection sensor(40) processes the image recording image. The abnormality monitoring unit(100) watches the abnormality of the loop sensor. When the abnormality signal of the loop sensor is a message received, the controller(10) switches the captured image signal sent to the camera part.

Description

Vehicle monitoring system and control method {Vehicle Monitoring System and Method for Controlling the Same}

The present invention relates to a vehicle monitoring apparatus and a control method thereof, but is not limited thereto. The present invention relates to a vehicle monitoring apparatus and a control method of monitoring a driving state of a vehicle by reading a license plate from a photographed image of a vehicle.

Recently, a number of fields using unmanned enforcement systems, crime prevention systems, parking control systems, traffic information collection systems, and the like by reading a license plate of a vehicle and recognizing a vehicle number have been increasing. These systems can be classified according to various criteria, but the system operated for the control of law enforcement vehicles, the arrest of criminal suspects, and the prevention (collectively, "the crime prevention system" for convenience), and the traffic flow by collecting traffic information It can be divided into a system operated for the purpose (hereinafter referred to as "traffic information system"). The crime prevention system may include an unmanned enforcement system used for speeding enforcement, signal violation control, and parking violation enforcement, an anti-security system used for criminal vehicle or criminal suspect, and a parking control system. The traffic information system may include an AVI (Automatic Vehicle Identification) that collects the speed, traffic volume, speed between a certain point, or a certain section of the road. ", As part of the detailed services of the Intelligent Traffic System (ITS). Security systems are generally installed and operated by local governments, police, etc., traffic information systems are generally installed and operated by the Ministry of Land, Transport and Maritime Affairs, Korea Highway Corporation.

As described above, in the apparatus or system for monitoring the vehicle by reading the vehicle number from the captured image, it is generally necessary to detect the vehicle in order to control when the camera photographs the vehicle. There are various vehicle detection methods (vehicle detection sensors), which are the most widely used and most stable, but the buried loop sensor method and the less stable but not buried laser, ultrasonic and image detection methods exist.

Referring to FIG. 1, an example of a vehicle monitoring apparatus according to various vehicle detection sensors will be described.

1A shows a vehicle monitoring apparatus 1 using a loop sensor.

The roof sensor 30 is embedded in the road. When the vehicle passes over the roof sensor 30, the loop sensor 30 detects this and generates a photographing signal (trigger signal) to photograph the vehicle in the camera unit 20. The captured image is transmitted to the controller 10, and the controller 10 reads the license plate by image processing.

1B and 1C are vehicle monitoring apparatuses using an image detection sensor.

The video detection method is VDS (VIDEO DETECTION SYSTEM) and is mainly used for measuring traffic volume. There are two types of video detection methods. As shown in FIG. 1B, there is a method of detecting an entry of a vehicle by analyzing an image using the auxiliary camera unit 40 separately from the camera unit 20 photographing the vehicle in order to read the vehicle number. In addition, as shown in FIG. 1C, there is a method of using only one camera unit 20. In this method, a method of capturing a whole image when a predetermined area of a photographing area of the camera unit 20 is quickly detected and detecting a change in an image, and the camera unit 20 itself operates to capture a vehicle and In the case of extracting the feature point, there is a method of determining and storing as a vehicle.

There are two methods of processing the image: a method using difference images between frames, a method of extracting correspondence points between frames, and a method using background images and difference images. Kalman filtering is widely used to make this possible.

Meanwhile, among the above-described vehicle detection methods, since the loop sensor method is inexpensive and the reliability is relatively high, the loop sensor method is mostly used. However, damage to the roof sensor or damage due to the weight of the vehicle may occur during the construction of the road on which the roof sensor is installed. If an abnormality occurs in the roof sensor, the vehicle cannot be photographed, and in this case, the vehicle detecting device is not preferable because it does not function properly. do. In particular, the security vehicle number reading device (security vehicle monitoring device), if the vehicle is not photographed due to the detection failure of the vehicle is likely to cause a problem. This is because decisive problems, such as failure to arrange a criminal vehicle, often occur due to a vehicle that fails to photograph. Accordingly, there has been a demand for the development of a device capable of photographing a vehicle normally even when an abnormality occurs in the vehicle detection sensor.

An object of the present invention is to provide a vehicle monitoring apparatus and a control method thereof that can minimize the occurrence of vehicle detection abnormality.

In order to achieve the above object, the present invention includes a camera unit for photographing a predetermined area including a vehicle; A loop sensor for sensing the vehicle; An image sensor configured to image the photographed image by photographing the vehicle and determine whether the vehicle passes through a predetermined region; An abnormality monitoring unit for monitoring an abnormality of the loop sensor; When the abnormality monitoring unit receives a signal that the loop sensor is abnormal, it provides a vehicle monitoring value including a control unit for switching the shooting signal (trigger signal) sent to the camera unit.

The loop sensor may include a loop coil part embedded in a road, and a loop control part connected to the loop coil part through a connection line to sense a vehicle using a predetermined value, wherein the abnormality monitoring part is connected to the loop control part. Preferably, the abnormality monitoring unit may be connected to the connection line. The abnormality monitoring unit preferably includes a reset module for resetting the loop control unit.

The control unit may use the vehicle detection signal of the loop sensor as a basic photographing signal for operating the camera unit, and switch the signal of the image detection sensor to a photographing signal when the loop sensor is abnormal.

On the other hand, the image detection sensor may use a separate auxiliary camera unit, or may use the original camera unit.

According to another embodiment of the present invention, the present invention comprises a camera unit for photographing a predetermined area including a vehicle, and selects a specific signal from among a plurality of photographing signals (trigger signals); A loop sensor for sensing the vehicle; An image sensor configured to image the photographed image by photographing the vehicle and determine whether the vehicle passes through a predetermined region; An abnormality monitoring unit for monitoring an abnormality of the loop sensor; And a controller for controlling the image detection sensor and including a controller configured to process an image photographed by the camera unit.

According to another embodiment of the present invention, there is provided a basic sensing mode setting step of setting which sensor signal is the basic sensing mode among at least a vehicle sensing sensor including a loop sensor and an image sensing sensor; An abnormality determining step of determining an abnormality of the vehicle detecting sensor; When the predetermined vehicle detection sensor is determined to be abnormal, the control method of the vehicle monitoring apparatus including a switching step of switching the detection mode to another vehicle detection sensor is provided. In the basic sensing mode setting step, it is preferable to set the basic sensing mode to the loop sensor sensing mode.

In the abnormality determination step, it is preferable to determine whether or not the abnormality of the loop sensor by comparing the predetermined characteristic value and the measured characteristic value. The characteristic value is preferably at least one of current, voltage, frequency, and period. In addition, the characteristic value may be a characteristic value defined by a statistical technique. The characteristic value may be the number of photographing signals for a predetermined time. The characteristic value may be traffic information of a vehicle for each lane, and the characteristic value may be a real-time detection signal of a loop sensor installed in an adjacent lane.

On the other hand, the switching step preferably includes a step of switching to a signal of the normal vehicle detection sensor, and an abnormality alarm step of informing the abnormality of the abnormal occurrence vehicle detection sensor. In the switching step, it is preferable to further include an operation step of operating the image detection sensor when switching from the loop sensor to the image detection sensor.

The present invention described above has the following effects.

First, according to the present invention, even if an abnormality occurs in the vehicle detection, there is an advantage that the vehicle can be stably photographed.

Secondly, according to the present invention, if an error occurs in the vehicle detection sensor, there is an advantage that it can take immediate action.

First, referring to FIG. 2, a general loop sensor will be described as follows.

The loop sensor 30 is generally installed according to the National Electronic Manufactu Ring Association (NEMA) standard of the United States, and is mainly composed of a loop coil part 32, a lead wire 36, and a loop control part 34, and a loop control part 34. ), The vehicle detection signal is output.

The roof coil portion 32 is formed of a loop having 2 to 4 rotational speeds embedded in a lane and typically forms a 1.8m circular or 1.8m X 1.8m sensing area. The loop coil unit 32 is configured in a circular, octagonal, and 32-angular shape according to the purpose of the desired parameters, that is, speed, traffic volume, occupancy rate, saturation, and the like. After cutting about 80mm from the ground, the loop coil is rotated 3 to 4 times, and the cutting part is sealed to prevent the loop work from vibrating through the sealant.

The loop coil unit 32 is supplied with energy having a frequency of 10 to 200 KHz from the loop control unit 34, and the inductance changes when the vehicle passes over the roof coil unit 32, and the electric and electronic The characteristic value is sensed by the loop control unit 34 to determine the presence or absence of the vehicle.

The sensitivity of the roof coil unit 32 is defined as the minimum change in inductance that can determine the presence or absence of a vehicle. In the absence of the vehicle, the roof coil unit 32 has a constant inductance LN. When the vehicle passes, a change in inductance LV occurs due to the interaction between the roof coil unit 32 and the passing vehicle, and the inductance change amount LL is LL = LN-LV. The ratio of the change in inductance when there is no vehicle and when the vehicle passes is SL (%) = (LL / LN) X 100 when the loop sensitivity (SL) is used. This loop sensitivity varies depending on the loop pattern change of the loop coil portion 32 to be formed and the change of the loop inductance due to the rotation speed. In the state where the loop pattern change and the rotation speed of the loop coil are determined, the sensitivity is determined according to the increase or decrease of the inductance along the length of the loop cable (connecting line) 36. If the loop sensitivity (SD) is defined at the input of the loop control unit 34 including the inductance (LC) and the change rate (LCR) of the connection line 36, SD (%) =-(LL + LCR) / (LN + LC) X 100.

On the other hand, the loop sensitivity is the sensitivity of the loop coil unit 32 only, and the connection line 36 which serves to connect the loop coil unit 32 to the loop control unit 34 in order to transmit it to the loop control unit 34 without change. Is typically 5.5 times / feet twist to cancel the change in inductance and connect to loop control 34. On the other hand, the loop control unit 34 is referred to as a scanning rate (scanning rate) to determine whether the vehicle is detected is typically performed within 20ms. At this time, when detecting the detection of the vehicle triggers a trigger signal to the camera unit or the control unit.

On the other hand, the loop sensor 30 is divided into an analog and a digital method, and at present, a highly reliable digital method is mainly used. Digital methods include frequency change measurement method, frequency change rate measurement method, and period change measurement method. In the frequency change measurement method, the digital processor counts a loop frequency when there is no vehicle, stores a reference count value in a memory, and compares and detects a count value when there is a vehicle based on the value. The frequency change rate measurement method is similar to the frequency change measurement method, except that the frequency counter has a constant value. The vehicle is detected by comparing the rate of change of the frequency according to the vehicle presence and the predetermined threshold value. The measurement method of the period change converts the loop frequency into a period and detects the vehicle by comparing the period with the reference frequency. As the vehicle enters the sensing area, the inductance decreases, the frequency increases and the period becomes shorter, with a decrease in the period measured at the fixed frequency. By this reduction, the detector produces an output indicating that the vehicle is present. In the periodic rate measurement method, the sensor's built-in digital processor compares a count that is proportional to the reference count in the absence of the vehicle and the oscillator period in the presence of the vehicle. The sensitivity of this type of detector is independent of the detector's sensitivity independent of the period change value.

Referring to Figure 3, the overall configuration of the vehicle monitoring apparatus 1 according to the present invention will be described.

The camera unit 20, which captures a predetermined area including the vehicle, is connected to a controller 10 that reads the license plate by image processing the captured image. In addition, the loop sensor 30 for detecting a vehicle and the image detection sensor 40 for determining whether the vehicle passes through a predetermined region by image processing the image photographed by photographing the vehicle are also preferably connected to the controller 10. Do. Then, the abnormality monitoring unit 100 for monitoring the abnormality of the loop sensor 30 is provided. Here, the image sensor 40 may be an auxiliary camera unit or a camera unit, but FIG. 3 shows the auxiliary camera unit as an image detection sensor for convenience.

On the other hand, as described above, the loop sensor 30 is configured to include a loop coil portion 32, the connection line 36 and the loop control unit 34. The abnormality monitoring unit 100 is connected to the loop sensor 30 to determine whether there is an abnormality of the loop sensor, and transmits the determined content to the control unit 10. (Details of the abnormality monitoring unit will be described later) In FIG. Although the abnormality monitoring unit 100 is illustrated as being connected to the connection line 36, the exemplary embodiment is not limited thereto, and the abnormality monitoring unit 100 may be connected to the loop control unit 34. In addition, the loop control unit 34 and the abnormality monitoring unit 100 are not necessarily separated physically, and of course, may be simultaneously implemented in one device.

On the other hand, the camera unit 20 is operated by a shooting signal (trigger signal) from the vehicle detection sensor, in the present invention, since two or more vehicle detection sensors 30 and 40 are installed, the signal from one of them It is preferable to set in advance the basic photographing signal. Since the loop sensor 30 is relatively stable, it is preferable to use the signal of the loop sensor 30 as a basic photographing signal. In this case, when the control unit 10 receives a signal that the loop sensor 30 is abnormal in the abnormal monitoring unit 100, the control signal 10 switches the photographing signal sent to the camera unit 20 to the signal of the video monitoring sensor 40. .

In the present embodiment, since the loop sensor 30 and the image detection sensor 40 are used, it is preferable that the controller 10 has a control method suitable for each sensor. This is because the loop sensor method and the image detection sensor method need to be changed not only for image processing but also for operating lighting at night. For example, the loop sensor method operates infrared light only when a vehicle is detected, but the image sensor method requires continuous light emission or continuous light emission. In addition, it may be necessary to change the algorithm due to the characteristics of the algorithm for reading the license plate by processing the image. In the loop sensor method, the camera unit and the lighting are operated in accordance with the detection signal of the loop sensor. In the video sensor method, the vehicle must be detected as an image. This is because the trigger itself must be generated by the controller.

First, referring to FIGS. 3 and 4, the abnormality monitoring unit 100 detects an abnormality of the loop sensor 30 in detail as follows.

The abnormalities that can normally occur in the loop sensor 30 include disconnection, short circuit, fusion, etc. of the loop coil unit 32 and the connection line 36, and the holding of the loop control unit 34. Holding refers to a case where the state in which the loop sensor 30 does not detect the presence of the vehicle continues, and may occur due to a problem of the loop coil unit, the connection line, the loop control unit, and the loop control unit 34 may be restored by resetting. Most of this is. In addition, short-circuit, fusion, disconnection, etc. of the loop coil part 32 or the connection line require maintenance normally.

As described above, in the loop sensor 30, the electric and electronic characteristic values, that is, inductance, current, voltage, frequency, period, etc., when the vehicle is absent and when the vehicle is present, are changed. In addition, when an abnormality occurs in the loop sensor 30, these electric and electronic characteristic values also change. Therefore, the abnormality of the loop sensor 30 may be determined by comparing a predetermined characteristic value (hereinafter, referred to as a “normal characteristic value”) with the measured characteristic value. That is, the "normal characteristic value" means an electric and electronic characteristic value when a vehicle is not present and the loop sensor is not a failure and an electric and electronic characteristic value which is normally measured when the vehicle is detected, and may be defined (set) through experiments or the like in advance.

Therefore, the normal characteristic value is first set. (S52) Then, the measured characteristic value (hereinafter referred to as "measurement characteristic value") in real time is compared with the normal characteristic value (S54), and if the measured characteristic value is within the range of the normal characteristic value, the loop sensor is normal. If it is determined (S56), if it is outside the normal characteristic value range, it can be determined that the loop sensor is abnormal (S58). For example, as a result of testing voltage and frequency according to various situations, if there is no vehicle and the loop sensor is normal, 11V, 40kHz, if there is a vehicle and the loop sensor is normal, 9.5V, 46kHz, and the loop is disconnected. It was 14V and 13.8kHz. Therefore, for example, when the frequency is used as the characteristic value, when the measured characteristic value is not 40 kHz or 46 kHz, it may be determined that the loop sensor 30 is abnormal. Of course, it is desirable to predefine the values of these characteristic values so as to be in an appropriate error range through experiments.

By using the above-described principle, the abnormality monitoring unit 100 configures and detects a circuit for detecting an electric and electronic characteristic value (frequency, inductance, current, voltage, etc.) in the loop coil unit 32 or the connecting line 36. It is possible to implement That is, the abnormality monitoring unit 100 is connected in parallel to the loop coil unit 32 or the connecting line 34 so that these characteristic values are periodically or continuously measured, and the measured characteristic values are different from the predetermined characteristic values. In case of occurrence, it is determined that the loop sensor 30 is abnormal, and whether the abnormality is sent to the control unit 10 is attempted to switch to the image detection sensor system.

On the other hand, when holding occurs, the traffic volume of the predetermined time, the comparison of the traffic volume with the side lane, or the vehicle is not in the continuous sensing state when the vehicle does not stop. It is possible. In this case, the abnormality monitoring unit 100 may also perform a function of performing a power reset of the loop sensor 30 through the relay output. Therefore, the abnormality monitoring unit 100 preferably includes a reset module (not shown) for resetting the loop sensor 30.

In the above, the abnormality of the loop sensor was determined using the electric and electronic characteristic values, but the abnormality of the loop sensor may be determined using other statistical techniques. Referring to Figure 5, it will be described as follows.

The number of vehicle detection signals output from the roof sensor can be used as a characteristic value. That is, by using a statistical technique, if there is no vehicle detection signal for a predetermined time, it may be determined that the loop sensor is abnormal.

In detail, for example, the real-time detection information of the loop sensor, for example, the number of times of detection, is detected for each lane (S552). In operation S554, it is determined whether the vehicle is detected for a predetermined time. If the vehicle is not detected at all for a predetermined time, the corresponding loop sensor is determined to be abnormal (S556), otherwise it is determined to be normal (S558). This method can also be used to determine the abnormality of the image sensor.

In addition, the traffic information of the vehicle statistically collected for each lane may be used as a characteristic value. Because the traffic volume for each specific road is usually determined in a certain range, it may be tabled by a statistical technique, for example, if the vehicle is not detected a predetermined number of times in a predetermined time period, it may be determined that the loop sensor is abnormal.

In addition, the real-time output signal of the loop sensor installed in the adjacent lane can be used as a characteristic value. Because the situation of a vehicle that normally passes adjacent lanes will be similar, a vehicle is detected in an adjacent lane, but if the vehicle is not detected at all, the loop sensor may be determined to be abnormal.

Referring to Figure 6, the control method of the embodiment of the vehicle monitoring apparatus according to the present invention will be described.

First, at least a sensor of a vehicle sensor including a loop sensor and an image sensor is set as a basic detection mode. (S3) Hereinafter, for convenience of description, the basic detection mode will be looped below. For example, the sensing mode is described.

The abnormality of the loop sensor is determined (S5), and when the loop sensor is determined to be abnormal, the image sensor is switched to the image sensing mode (S9). Of course, the loop sensor continues to operate in the loop detection mode as normal (S7). Determining the abnormality of the loop sensor has been described above, and thus description thereof is omitted.

7, switching to the image sensing mode will be described.

When an abnormality occurs in the loop sensor, the signal of the vehicle detection sensor, that is, the image detection sensor, in which the abnormality does not occur is switched to the photographing signal (S94). At this time, it is preferable to notify the user of the abnormality of the loop sensor (S96). The abnormality alarm may be performed by the abnormality monitoring unit or the control unit, or may be performed by an operation center connected to the control unit through a communication network.

On the other hand, when switching from the loop sensor to the image sensor, it is preferable to start the operation of the image sensor, for example, the auxiliary camera (S96). Because the auxiliary camera unit is preferably operated only when there is an abnormality in the loop sensor, when the abnormality occurs in the loop sensor, the control unit operates the auxiliary camera unit. In addition, if it is determined that the abnormality of the loop sensor is holding, it is preferable to reset the loop sensor (S98).

9, another embodiment of a vehicle monitoring apparatus according to the present invention will be described.

This embodiment also has the same principle as the above-described embodiment. However, in this embodiment, the loop sensor 30 is connected to the camera unit 20. In this case, the camera unit 20 preferably has a function of selecting a specific signal among a plurality of photographing signals.

Meanwhile, in the above-described embodiment, the switching from the loop sensor method to the image sensor method is illustrated and described, but the present invention is not limited thereto. In other words, it is also possible to switch from the video sensor method to the loop sensor method.

Determining an abnormality of the image sensor may be relatively easier than determining an abnormality of the loop sensor. Because the image sensor detects the presence or absence of the vehicle by image processing, it is possible to determine whether the image sensor is abnormal by using the image processing algorithm immediately.

In addition, the method using the statistical method described in the method of determining whether there is an abnormality of the loop sensor may also be used to determine the abnormality of the image sensor.

1 is a configuration diagram showing the configuration of a general vehicle monitoring device

2 is a block diagram showing the configuration of a typical loop sensor

3 is a configuration diagram schematically showing an embodiment of a vehicle monitoring apparatus according to the present invention

4 is a flowchart illustrating a method of detecting an abnormality of a loop sensor in an embodiment of a control method of a vehicle monitoring apparatus according to the present invention.

5 is a flowchart illustrating another method of detecting an abnormality of a loop sensor in an embodiment of a control method of a vehicle monitoring apparatus according to the present invention.

6 is a flowchart showing the overall configuration in an embodiment of a control method of a vehicle monitoring apparatus according to the present invention.

7 is a flowchart illustrating an image sensing mode of FIG. 6.

8 is a schematic view showing another embodiment of a vehicle monitoring apparatus according to the present invention

Claims (17)

A camera unit for photographing a predetermined area including a vehicle; A loop sensor for sensing the vehicle; An image sensor configured to image the photographed image by photographing the vehicle and determine whether the vehicle passes through a predetermined region; An abnormality monitoring unit for monitoring an abnormality of the loop sensor; And a controller configured to switch a photographing signal (trigger signal) to the camera unit when the loop sensor receives a signal that the loop sensor is abnormal. The loop sensor of claim 1, wherein the loop sensor comprises a loop coil part embedded in a road, and a loop control part connected to the roof coil part through a connection line to sense a vehicle using a predetermined value. Vehicle monitoring device, characterized in that connected to the loop control unit. The loop sensor of claim 1, wherein the loop sensor comprises a loop coil part embedded in a road, and a loop control part connected to the roof coil part through a connection line to sense a vehicle using a predetermined value. Vehicle monitoring device, characterized in that connected to the connecting line. The loop sensor of claim 1, wherein the loop sensor comprises a loop coil part embedded in a road, and a loop control part connected to the roof coil part through a connection line to sense a vehicle using a predetermined value. And a reset module for resetting the loop control unit. The method of claim 1, wherein the control unit uses the vehicle detection signal of the loop sensor as a basic photographing signal for operating the camera unit, and when the loop sensor is abnormal, converts the signal of the image detection sensor into a photographing signal. Vehicle monitoring equipment. The vehicle monitoring apparatus according to claim 1, wherein the image detection sensor is an auxiliary camera unit. The vehicle monitoring apparatus according to claim 1, wherein the image detection sensor is the camera unit. A camera unit for photographing a predetermined area including a vehicle and selecting a specific signal among a plurality of photographing signals (trigger signals); A loop sensor for sensing the vehicle; An image sensor configured to image the photographed image by photographing the vehicle and determine whether the vehicle passes through a predetermined region; An abnormality monitoring unit for monitoring an abnormality of the loop sensor; And a controller for controlling the image detection sensor and processing an image captured by the camera. A basic detection mode setting step of setting which of the vehicle detection sensors including at least a loop sensor and an image detection sensor is a basic detection mode; An abnormality determining step of determining an abnormality of the vehicle detecting sensor; And a switching step of switching the detection mode to another vehicle detection sensor when it is determined that the predetermined vehicle detection sensor is abnormal. The control method of a vehicle monitoring apparatus according to claim 9, wherein in the basic sensing mode setting step, the basic sensing mode is set as the loop sensor sensing mode. The control method of claim 9, wherein in the abnormality determining step, the presence or absence of the abnormality of the loop sensor is determined by comparing a predetermined characteristic value and a measured characteristic value. 12. The method of claim 11, wherein the characteristic value is at least one of a current, a voltage, a frequency, and a period. The method of claim 11, wherein the characteristic value is a characteristic value defined by a statistical technique. 12. The control method for a vehicle monitoring apparatus according to claim 11, wherein the characteristic value is the number of photographing signals during a predetermined time. The control method of claim 11, wherein the characteristic value is a real-time detection signal of a loop sensor installed in an adjacent lane. The control method according to claim 9, wherein the switching step includes a step of switching to a signal of a normal vehicle detection sensor and an abnormal alarm step of notifying an abnormality of the abnormally generated vehicle detection sensor. The control method according to claim 16, further comprising an operation step of operating the image detection sensor when switching from the loop sensor to the image detection sensor in the switching step.

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