JPH05323014A - Radar type vehicle detector - Google Patents

Abstract

PURPOSE:To automatically determine a threshold level value which becomes a reference for detecting a vehicle according to environmental conditions such as weather and road surface using a radar type vehicle detector. CONSTITUTION:A power supply throwing detection part 1 detects throwing of the power supply of the title detector and resets a time counter 10. Then, a noise level initial setting part 2 initializes noise level and then the value is stored in a noise level memory 4. Then, a reception level detection part 6 measures the reception signal level at each time period of T1. Then, a comparison part 7 compares the reception level with the noise level which is stored in the noise level memory 4. Then, a noise level modification part 8 lowers the noise level which is stored in the noise level memory 4 when the reception signal level is lower than the noise level. When a certain amount of time T2 passes after power is turned on, a value which is obtained by adding a predetermined value to the noise level which is stored in the noise level memory 4 is set as a threshold level by a threshold determination part 9. Further, the threshold level is set again at each certain amount of time T3 after power is turned on.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar type vehicle detector which senses a vehicle and measures traffic volume and vehicle speed.

[0002]

2. Description of the Related Art Conventionally, a radar type vehicle detector of this type emits a microwave and receives a reflected wave thereof,
It is configured so that the vehicle speed can be measured by the Doppler effect while sensing the vehicle.
The vehicle is sensed by comparing the level of the received reflected wave (reception level) with a threshold level (threshold value) to determine the level. Both levels are converted into digital values and compared. This sensing method is shown in FIG. The horizontal axis of FIG. 3 represents time, and the vertical axis represents reception level. In FIG. 3, reference numeral 31 is a reception level waveform, and the received reflection wave is digitized by an AD converter and is represented as a level. 32 is a noise level, and 33 is a threshold level. The threshold level 33 is set to a value higher than the noise level 32. In waveform 31, the reception level rises when a vehicle appears. While the reception level reaches the level higher than the threshold level 33, it is determined that the vehicle exists or is passing, and while the signal of the reception level lower than the threshold level 33 is received, or Even if the level rises, it is determined that there is no vehicle until the threshold level 33 is reached. The threshold level 33 is always set to a constant value.

[0003]

The level of the reflected wave (reception level) received by this type of radar type vehicle detector is, for example, rain or fog even if the same vehicle passes or exists under exactly the same conditions. The value varies depending on weather conditions such as snow and road surface conditions such as dry and wet conditions, that is, environmental conditions. At the same time, the noise level also varies depending on the environmental conditions. However, in the conventional radar type vehicle detector, the threshold level value, which is a reference for vehicle detection, is fixed to a constant value, and therefore the vehicle to be detected may change due to changes in environmental conditions such as weather and road conditions. There was a problem that the conditions may be different and the vehicle may be erroneously sensed.

The present invention solves the above-mentioned conventional problems. By automatically changing the threshold level value according to changes in environmental conditions such as weather and road conditions, the vehicle is always correctly operated. It is an object of the present invention to provide an excellent radar type vehicle detector that can be detected.

[0005]

In order to achieve the above-mentioned object, the present invention provides a power-on detector for detecting that the sensor is powered on, a noise level memory for storing a noise level, and a noise level. A noise level initial setting unit that initializes the contents of the memory, a reception level detection unit that measures the strength of the received signal from the radar head, a noise level stored in the noise level memory, and a reception level measured by the reception level detection unit A comparing unit that compares with, a noise level changing unit that corrects the noise level in response to the result of comparison by the comparing unit, and a threshold determining unit that determines the threshold level according to the noise level stored in the noise level memory, A time counter unit that counts the time after the power of the sensor is turned on.

[0006]

With the above configuration, the noise level is determined from the reception level, and the threshold level is automatically determined according to the noise level. Therefore, with reference to the threshold level that matches the environmental conditions such as weather and road conditions, This makes it possible to always correctly detect the vehicle based on the reception level without being affected by environmental conditions.

[0007]

1 is a block diagram showing the configuration of an embodiment of the present invention. In FIG. 1, the output of the power-on detection unit 1 that detects that the sensor is powered on is input to the determination unit 3 via the noise level memory initial setting unit 2.
The determination unit 3 is composed of the following elements. The noise level memory 4 is input from the noise level initial setting unit 2. The reception signal 5 is sent from the radar head, digitized, and input to the reception level detector 6. The comparison unit 7 is input from the noise level memory 4 and the reception level detection unit 6 and output to the noise level changing unit 8. The noise level changing unit 8 is also input from the reception level detecting unit 6 and outputs it to the noise level memory 4. The threshold determination unit 9 is input from the noise level memory 4. Reference numeral 10 is a time counter that counts the time after the power of the sensor is turned on. The time counter 10 is input from the power-on detection unit 1 and sends a clock pulse to each unit included in the determination unit 3.

FIG. 2 is a flow chart showing the operation of this embodiment. Next, the operation of the above embodiment will be described in detail with reference to FIGS. When the power supply of the radar type vehicle detector according to the present embodiment is turned on (step S1), the power-on detection unit 1 detects this and resets the time counter 10 (variable t = 0) (step S2). After that, the time counter 10 automatically starts counting time (increase of the variable t). At the same time, the noise level initial setting unit 2 sets the noise level to the initial setting value (step S3). The reception level is digitized and the data has an 8-bit structure. In this case, the maximum noise level can be expressed as 255 (for example, 5V). First, the noise level initial setting unit 2 sets the noise level to 255. Then, the value is stored in the noise level memory 4. Next, the reception level detector 6 measures the reception level (step S6). Next, the comparison unit 7 compares the reception level with the noise level stored in the noise level memory 4 (step S7). When the reception level is lower than the noise level, the noise level changing unit 8 sharply (for example, 50) lowers the noise level stored in the noise level memory 4 (step S8). However, do not lower it below the reception level. The process from step S5 to step S8 is performed at time interval T1 (for example, 100 ms) (step S
4). After the power is turned on, the operation up to this point is continuously and repeatedly performed for a time period T2 (for example, 5 minutes) longer than the time T1. A value obtained by adding a predetermined value level (e.g., 1 V equivalent) to the noise level stored in the noise level memory 4 in the threshold level determining unit 9 at the time when the time T2 has elapsed after the power is turned on (step S5). Is set as the threshold level (step S
9). Furthermore, time longer than time T2 (for example, 2 hours)
After the lapse of the time T3 (step S10), the process returns to step S2 again, and the threshold level is set again. This flow is repeated at intervals of time T3.
The function of determining the reception level using the threshold level that is automatically set is the same as in the conventional example.
It is not included in FIG.

As described above, according to the above embodiment, the receiving level obtained by the receiving level detecting section 6 and the noise level stored in the noise level memory 4 are repeatedly compared by the comparing section 7 at every time interval T1. And change the noise level. Then, after the time T2, the threshold level is determined by the threshold level determination unit 9 from the determined noise level, so that the threshold level for vehicle detection can be automatically determined. Further, by setting the threshold level again at each time T3, the optimum threshold level is always maintained even if there is a change in the environment such as rain or fog while the sensor is in use. be able to.

[0010]

As is apparent from the above embodiments, the present invention has the effect that the threshold level value can be automatically determined according to the road condition and environment, and the optimum criterion can always be maintained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a radar type vehicle detector according to an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the embodiment of the present invention.

FIG. 3 is a diagram illustrating a detection method of a radar type vehicle detector.

[Explanation of symbols]

 1 Power-on detection unit 2 Noise level initial setting unit 3 Judgment unit 4 Noise level memory 6 Reception level detection unit 7 Comparison unit 8 Noise level change unit 9 Threshold determination unit 10 hour counter

Claims (1)

[Claims] 1. A power-on detection unit for detecting power-on of a sensor, a noise level memory for storing a noise level, a noise level initial setting unit for initializing the contents of the noise level memory, and a reception level detection unit. And a comparing unit that compares the noise level stored in the noise level memory with the output level of the reception level detecting unit, and receives the output of the comparing unit and corrects the noise level stored in the noise level memory. A noise level changing unit, a threshold determining unit that sets a threshold level based on the noise level stored in the noise level memory, and a time counter unit that starts timing when the sensor is powered on. , Radar type vehicle detector that updates the threshold level setting at regular intervals.