JPS5925444B2 - Time occupancy measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring time occupancy of a moving target.

Conventionally, to measure the temporal occupancy of a moving target such as a vehicle 10 traveling on a road, a beam from an ultrasonic or microwave sensor 11 is projected onto the road 12 as shown in Fig. 1, and the intensity of the reflected wave is above a certain level. The period received by the server was output as a time interval.

In this method, the beam size A, that is, the sensing area size l', is added to the vehicle length l, and the value Ti, which is divided by the speed, is output as time occupancy. , the effective sensing region length l' changes due to variations in sensitivity settings, the magnitude of antenna directivity, etc., which affects the output value Tl.

That is, 11'T, = - + - The present invention eliminates these drawbacks, forms a sensing area as thin as possible in the direction of movement of the target object, and is less affected by the size of the reflection of the target object and the size of the sensing area. This provides a time occupancy measurement method.

Examples thereof will be described below.

FIG. 2 shows a measurement state in which an ultrasonic or microwave beam is projected onto a road 12 from a sensor 11. A is the beam size and B indicates the sensing area. The received wave of the emitted microwave beam is subjected to homoturn detection to obtain a Doppler signal.

These Doppler waves can discriminate whether the direction of velocity of the moving target is positive or negative for each wave.

For example, in a microwave radar, the received wave is branched and supplied to two detectors with the same phase, while a portion of the transmitted output is supplied to the two detectors with a π/2 phase difference and detected. The phase difference between the Doppler signals of the detector is reversed depending on whether the velocity direction of the moving target is positive or negative. Sensor 1 as shown in Figure 2
An example of setting 1 will be explained with reference to FIG. 3.The conventional idea is that a threshold value D is set for the Doppler signal as shown in a to determine the size of the sensing area, and that the threshold value D is generated while the target object 10 moves within the sensing area. Let b be the time occupine signal. This is a signal that continues from the time when the leading end of the moving target 10 enters the sensing area B until the time when the rear end of the moving target 10 exits the sensing area 10. Next, assume that the Doppler signal is discriminated in the positive and negative directions during the duration of signal b. For example, if the approaching state is "bi" and the far away state is "0", the direction discrimination output is "1" until the tip of the moving target 10 passes directly below the sensor 11 as shown in c, and at the time it passes directly below. Target moving from 1
Until the rear end of 0 passes directly below, 61-"0゛° is mixed. This is due to the reflection of the moving target 10 before passing directly below the sensor 11 and the reflection of the moving target 10 after passing directly below the sensor 11 This is because the magnitude relationship with the reflection of the portion 10 changes in various ways.When the rear end of the moving target 10 finishes passing directly under the sensor 11, the direction discrimination output becomes O゛.The above-mentioned direction discrimination output TIl-Tn+1, tn+1~T like d
Unit time T of n+2, tn+2 to Tn+3,...
It is checked whether or not there has been a reversal of the direction discrimination output during each O period, and if a signal is created that indicates "1" if there is, and "0" if not, the result will be as shown in e when one unit time delay is taken into account.

This can be made into a time occupancy output. The accuracy of time accuracy is T. Because it is that
The length 15 of the sensing region B in this case is 21-VXTO.

The size of TO is determined by experimentally investigating the possibility that the direction discrimination output will be constrained to either "1" or "01" for the longest time when the target object 10 passes directly under the sensor 11. In this way, the output time T2 of the signal e is actually l'>11, so compared to the conventional method, the size of the beam of the sensor 11 and the size of the moving target 10 are It is possible to form an extremely thin sensing region B, which has almost no relation to the magnitude of reflection, so as to be orthogonal to the traveling direction of the moving target.

As a result, compared to the conventional method, the proportional relationship of time occupancy to the length of the target object 10 is greatly improved, and measurement accuracy is also improved.

When measuring the length of the animal target 10, compared to the conventional method, l=v(T2-TO), and T is calculated from the variation in the actual measurement of l'/v.

Since the value of is small, highly accurate measurements can be made using this method. As is clear from the above embodiments, according to the present invention, time occupancy caused by a moving target can be accurately measured by providing a sensing region with a small thickness in the moving direction.

[Brief explanation of the drawing]

FIG. 1 is a side view of a measurement region in a conventional time occupancy measurement method, FIG. 2 is a side view of a measurement region in a time occupancy measurement method according to the present invention, and FIG. 3 is an operation waveform diagram thereof. 10...Moving target, 11...Sensor.

Claims (1)

[Claims] 1. While the presence of a moving target is detected by a radar that has a function of distinguishing between positive and negative directions of a moving target using a Doppler signal,
Time occupancy characterized by detecting whether or not there is a positive/negative reversal in the output of the direction discrimination circuit every fixed unit time, and setting the continuous time of the unit time in which the reversal exists as the time occupancy output. Measuring method.