JPS623739Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a speedometer using a Doppler radar, and is capable of unifying errors in measured values as positive or negative.

In general, measurements made by Doppler radar include errors due to frequency fluctuations in the high-frequency oscillator or clock oscillator, or asynchrony between the signal processing timing and the Doppler signal. These errors are minute, but when used for traffic enforcement, etc., positive errors are not allowed from the standpoint of protecting suspects.

The present invention takes such cases into consideration and allows errors in measurement values to be unified into positive or negative values.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The speedometer of the present invention will be described below with reference to drawings of an embodiment. 1 and 2 are input terminals to which Doppler signals obtained by a Doppler radar (not shown) are applied; 3 and 4 are waveform shaping circuits such as Schmitt circuits that shape the Doppler signals applied to input terminals 1 and 2; The circuit 5 is a direction discrimination circuit which receives the outputs of the waveform shaping circuits 3 and 4 as input and detects the phase difference to determine whether the measurement point and the measured point are in the approaching direction or in the far direction. 6 is composed of a reference time generating circuit 7 and error correction gate circuits 8 and 9 controlled by the output of the direction discriminator 5, and when the output from the direction discriminator 5 is in the approaching direction, In order to correct the negative maximum permissible error α, the gate circuit 8 is opened for a time equal to 1/1-α times the reference time obtained by the reference time generator 7. A reference time generation circuit 10 is configured to open the gate circuit 9 for a time equal to 1/1+β times the reference time in order to correct the maximum allowable error β of the measurement point; A measuring point moving speed detecting device 11 that outputs a proportional signal is preset by the output of the measuring point moving speed detecting device 10, and subtracts the number of pulses at the output of the waveform shaping circuit 3 when approaching, and adds when moving away. This is a counting circuit that ultimately counts the moving speed of the measured point.

Note that the counting circuit 11 is controlled to perform counting operation only for the time set by the reference time generating circuit 6, and therefore, only the number of pulses in the output of the waveform shaping circuit applied during this time is counted. It will be added or subtracted.

In the above embodiment, the measurement point is a traffic enforcement vehicle (measured vehicle), and the measured point is a suspect's vehicle (measured vehicle). In this case, when the measuring vehicle is moving, its moving speed is detected by the measuring point moving speed detecting device 10, and a value corresponding to the detected speed of the measuring vehicle is preset in the counting circuit 11.

On the other hand, the signal transmitted from the measurement vehicle is reflected by the vehicle to be measured, received by the Doppler radar, and converted into a Doppler signal. These Doppler signals are applied to input terminals 1 and 2, respectively, and waveform-shaped by waveform shaping circuits 3 and 4, and both outputs are sent to a direction discrimination circuit 5.
is applied to determine whether the vehicle to be measured is approaching or moving away from the vehicle to be measured. This determination result is applied to the up and down control terminals of the counting circuit 11. For example, if the direction discrimination circuit 5 determines that the direction is approaching, the counting circuit 1
1 becomes a down counter, and if it is determined that the object is moving away, the counting circuit 11 becomes an up counter. The counting circuit 11 is the reference time generating circuit 6.
It operates as an up counter or a down counter for a predetermined period of time according to the control signal output from the waveform shaping circuit 3, and counts up or down the number of output pulses of the waveform shaping circuit 3 from a preset value (a value corresponding to the speed of the measuring vehicle). Count down. Counting the number of output pulses of the waveform shaping circuit 3 for a predetermined period of time determines the relative speed between the measuring vehicle and the vehicle under test. The speed of the vehicle to be measured is determined by adding or subtracting the relative speed to the vehicle to be measured. However, there may be a slight error in relative speed measurements made by Doppler radar, and this error may result in a speed being measured that exceeds the speed limit when in fact it does not. It is possible to put it away.

Therefore, in the present invention, in order to prevent speed violation judgments based on errors in relative speed measurement values, the reference time is corrected by the gate circuit 8 or 9 in the reference time generation circuit 6, and the up count time in the counting circuit 11 is Alternatively, the down count time is corrected. For example, if the maximum allowable error α is 0.1 when the vehicle to be measured is approaching, the relative speed may be measured as 9 km/h even though the relative speed is 10 km/h. In this case, if the speed of the measuring vehicle is 60km/h, the speed of the vehicle being measured is actually 50km/h.
The speed was measured at 51km/h (60-9=51).

In order to correct such an error, in this embodiment, the time signal applied to the counting circuit 11 is corrected to be (1/1-α) times the reference time.

In addition, in the embodiment, in order to protect the position of the suspect in traffic enforcement, the error in the measured value is configured so that it does not become positive, but in other cases it is also possible to prevent it from becoming negative. .

In addition, although the embodiment is configured to detect the relative velocity based on the wave number of the Doppler signal applied within the reference time, the relative velocity may be detected depending on how much time it takes to obtain a predetermined wave number. It is also possible to detect speed. In this case, the circuit for measuring time or the wave number required for measurement can be corrected to make the error in the measured value either positive or negative.

As described above, according to the present invention, when the measured vehicle speed is measured from the relative speed determined by the Doppler radar which has a measurement error and the measured vehicle speed, even when the measured vehicle and the measured vehicle are approaching, Furthermore, even when the vehicle is moving away, the measured speed of the vehicle to be measured does not become faster than the actual speed of the vehicle due to an error in the relative speed measured by the Doppler radar.

[Brief explanation of drawings]

The figure is a block diagram of essential parts of an embodiment of the speedometer of the present invention. 1, 2...Input terminal, 3, 4...Waveform shaping circuit, 5...Direction discrimination circuit, 6...Reference time generation circuit, 7...Reference time generation circuit, 8, 9...Gate circuit, 10... ...Measuring point movement speed detection device, 11...
...Counting circuit.

Claims (1)

[Scope of utility model registration request] The measurement vehicle and the vehicle to be measured are determined based on the Doppler signal related to the relative speed between the vehicle to be measured and the vehicle to be measured, which is obtained by a measuring vehicle moving speed detection device that detects the moving speed of the measuring vehicle and a Doppler radar that has a measurement error. A direction discrimination circuit determines whether the target is approaching or going away, and if the direction discrimination circuit determines that the target is moving away, the time for counting Doppler signal wave numbers is shortened. and a reference time generation circuit that corrects the reference time so that the time for counting the Doppler signal wave number becomes longer when the direction discrimination circuit determines that the vehicle is approaching, and the measurement vehicle moving speed detection circuit. The value detected by the device is preset, and it operates as an up counter or a down counter depending on the judgment result of the direction discrimination circuit, and adds the Doppler signal wave number whose time is counted according to the output of the reference time generation circuit. or a counting circuit for subtraction, so that the measured speed of the vehicle to be measured does not become greater than the speed of the vehicle to be measured.