JPH04330600A - Radar type vehicle sensor - Google Patents

Abstract

PURPOSE:To automatically set the value of a threshold level that becomes reference for vehicle sensing corresponding to the environmental condition of weather and a road, etc. CONSTITUTION:The application of the power source of this device is detected at a power source application detecting part 1, and a time counter 10 is reset. Thence, a noise level is set at an initial preset value at a noise level initial preset part 2. The value is stored in noise level memory 4. Thence, the level of a reception signal is measured at every time T1 at a reception level detecting part 6. The level of the reception signal is compared with the noise level stored in the noise level memory 4 by a comparator 7. When it is judged that the level of the reception signal is less than the noise level, the noise level stored in the noise level memory 4 is decreased by a noise level change part 8. When prescribed time T2 elapses after the power source is applied, a value in which a value decided in advance is added on the noise level stored in the noise level memory 4 is set at a threshold decision part 9 as the threshold level.

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 sensor that detects vehicles, measures traffic volume, vehicle speed, etc., and transmits the measurement results to a traffic control center.

0002

[Prior Art] Conventionally, this type of radar-type vehicle sensing system detects a vehicle by emitting microwaves and receiving the reflected waves, and also measures vehicle speed using the Doppler effect. It is composed of Vehicle sensing is based on the level of the reflected waves received (reception level)
is sensed by comparing it with a threshold level. Both levels are converted into digital values and compared. This sensing method is shown in FIG. The horizontal axis in FIG. 3 is time, and the vertical axis is reception level. In FIG. 3, 31 is a received level waveform, which represents the received reflected wave digitized by an AD converter as a level. 32 is a noise level, and 33 is a threshold level. The threshold level 33 is set to a higher value than the noise level 32. In waveform 31, when a vehicle appears, the reception level increases. While the reception level reaches a level higher than the threshold level 33, it is determined that a vehicle exists or is passing, and while a signal with a reception level lower than the threshold level 33 is received, or Even if the reception level increases, if it does not reach the threshold level 33, it is determined that no vehicle is present. The threshold level 33 is always set to a constant value.

0003

[Problem to be Solved by the Invention] The level of reflected waves (reception level) received by this type of radar-type vehicle detector is different even if the exact same vehicle passes or exists under exactly the same conditions. , the value varies depending on the weather conditions such as snow, the road surface conditions such as dry or wet, or environmental conditions. At the same time, the noise level also varies depending on the environmental conditions. However, in conventional radar-based vehicle detectors, the threshold level, which is the standard for vehicle detection, is fixed at a constant value, so changes in environmental conditions such as weather and road conditions may affect the detection of the vehicle being detected. There have been problems in that the conditions may be different or the vehicle may be detected incorrectly.

The present invention solves these conventional problems by automatically changing the value of the threshold level according to changes in environmental conditions such as weather and road conditions, thereby ensuring that the vehicle is always operated correctly. The purpose of the present invention is to provide an excellent radar type vehicle detector capable of detecting vehicles.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a power-on detection section for detecting that the power of a sensor is turned on, a noise level memory for storing a noise level, and a noise level memory for storing a noise level. A noise level initial setting section that initializes the contents of the memory, a reception level detection section that measures the strength of the received signal from the radar head, and a reception level that measures the noise level stored in the noise level memory and the reception level detection section. a noise level changing unit that modifies the noise level based on the comparison result of the comparing unit; a threshold determining unit that determines the threshold level according to the noise level stored in the noise level memory; It is equipped with a time counter that counts the time since the sensor was powered on.

[0006]

[Operation] Therefore, by using the above configuration, the present invention determines the noise level from the reception level and automatically determines the threshold level according to the noise level, so that it can be adjusted to suit environmental conditions such as weather and road conditions. To always correctly detect a vehicle based on a reception level without being affected by environmental conditions, using a threshold level as a reference.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a power-on detection section that detects that the power of the sensor is turned on, 2 a noise level initial setting section, and 3 a determination section. The determination unit 3 is composed of the following elements. 4 is a noise level memory;
The contents are initialized by the noise level memory 4. 5 is a received signal, which is sent from the radar head and is digitized. Reference numeral 6 denotes a reception level detection unit that measures the level of the reception signal 5, and reference numeral 7 denotes a comparison unit that compares the noise level stored in the noise level memory 4 with the reception level measured by the reception level detection unit 6. 8 is a noise level changing unit that corrects the noise level based on the results compared by the comparing unit 7;
Reference numeral 9 denotes a threshold determination unit for determining a threshold level based on the noise level stored in the noise level memory 4. A time counter 10 counts the time since the power of the sensor is turned on, and sends clock pulses to each section included in the determination section 3.

FIG. 2 is a flowchart showing the operation of this embodiment. Next, the operation of this embodiment is explained in Figs. 1 and 2.
This will be explained in detail using . When the radar vehicle sensor according to the present embodiment is powered on (step S1), the power-on detection section 1 detects this and resets the time counter 10 (variable t=0) (step S2). Thereafter, the time counter 10 automatically starts counting time (increasing the variable t). At the same time, the noise level initial setting section 2 sets the noise level to an initial setting value. The reception level is digitized, and the data has an 8-bit configuration. In this case, the highest level value can be expressed as 255. First, the noise level is set to 255 (for example, 5
(equivalent to V) (step S3). Then, the value is stored in the noise level memory 4. Step S4 is a step in which the time counter 10 counts up the time after the power is turned on. Next, the reception level is measured by the reception level detector 6 (step S5). Next, the comparison unit 7 compares the reception level with the noise level stored in the noise level memory 4 (step S6). When the reception level is lower than the noise level, the noise level change section 8
, the noise level stored in the noise level memory 4 is suddenly lowered (to 50, for example) (step S
7). However, it should not be lower than the reception level. Step S
5 to step S7 are performed at time intervals T1 (for example, 100 ms). The processing up to this point is continuously repeated for a predetermined time T2 (T2 is much longer than T1) after the power is turned on (step S4). After the power is turned on, when time T2 has elapsed (step S4), the noise level memory 4 is stored in the threshold determination unit 9.
The threshold level is set by adding a predetermined level (e.g., equivalent to 1 V) to the noise level stored in (step S8). As described above, according to the above embodiment, the receiving signal level obtained by the receiving level detecting section 6 and the noise level stored in the noise level memory 4 are repeatedly compared in the comparing section 7 at every time interval T1. , change the noise level. Then, since the threshold level is determined by the threshold determination unit 9 from the determined noise level after the time T2, it becomes possible to automatically set the threshold level for vehicle detection.

[0009]

As is clear from the above embodiments, the present invention has the advantage that the threshold level value can be automatically set according to environmental conditions such as weather and road conditions.

[Brief explanation of the drawing]

[Fig. 1] Functional block diagram of a radar-type vehicle sensor in an embodiment of the present invention.

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

[Figure 3
】Explanatory diagram of the detection method of radar type vehicle detector

[Explanation of symbols] 1 Power-on detection section 2 Noise level initial setting section 4 Noise level memory 6 Reception level detection section 7 Comparison section 8 Noise level change section 9 Threshold determination section 10 Time counter

Claims (1)

[Claims] 1. A power-on detection unit that detects power-on of a sensor; a noise level memory that stores a noise level;
a noise level initial setting section that initializes the contents of the noise level memory; a reception level detection section; a comparison section that compares the noise level stored in the noise level memory with the output level of the reception level detection section; a noise level changing unit that receives the output of the comparing unit and modifies the noise level stored in the noise level memory; and a threshold determining unit that sets a threshold level based on the noise level stored in the noise level memory. and a time counter section that starts measuring time when the sensor is powered on.