JPS63149583A - Doppler type speed sensor - Google Patents

Abstract

PURPOSE:To enhance speed measuring accuracy, by determining the pulse width distribution of a shaped pulse and replenishing the pulse width based on the correlation of said pulse width and frequency distribution to an omitted part. CONSTITUTION:A two-beam system having two sensor part circuits 20, 22 and two pulse omission replenishing circuit 21, 23 is employed and a Doppler signal is amplified by an amplifier 4 to be passed through a filter 9 and a signal exceeding a definite threshold level is converted to a pulse width due regard to an S/N ratio by a comparator 5. Subsequently, the pulse widths of (n) pulses are counted by a counter 12 and, at the point of time when (n) pulses are counted, the correlation between the pulse widths is taken according to a peak plotting system. Then, a pulse omission part is calculated to be replenished by a pulse width correlation replenishing device 15. The number of pulses replenished at every beam are counted by a counter 16 and added between two beams of the circuits 21, 23 by an adder 17 and, thereafter, a display device 18 and a timing circuit 19 are used to output necessary display and a necessary signal. Therefore, the enhancement of accuracy can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a Doppler speed sensor for detecting the speed of a moving object, and particularly to a Doppler speed sensor using a speed calculation method suitable for highly accurate detection.

[Prior art] 1978-Blood 14 (S53-3) Society of Automotive Engineers of Japan Transactions Microwave vehicle speed sensor for skid control device 19
81-Na803 (S 64-4) IEICE National Conference Paper 1981-9 Hitachi Review V o L 63-
The Ha 9 microwave-applied high-precision speed sensor uses the average value of detected pulses to compensate for missing pulses that do not meet the threshold level.

The frequency of occurrence of missing pulses due to this is not taken into account, and therefore the error is only about 1%.

[Problem that the invention seeks to solve]

Although higher precision detection and control are desired, the conventional technology does not take into account the distribution correlation of detected pulses and simply averages compensation using detected pulses, so it is not possible to significantly improve accuracy. Nakatsuta.

An object of the present invention is to provide a Doppler speed sensor that can obtain sufficiently high precision in terms of software using a control technique without changing the detection hardware.

[Means for solving problems]

The above purpose is to analyze the measurement results with the conventional technology.

The desired high accuracy is achieved by understanding the distribution of the pulse width of the shaped pulse, finding the correlation between the pulse width and the frequency distribution, and filling in the missing parts with the pulse width based on that correlation. be done.

[Effect]

The signal level of the Doppler signal waveform changes continuously in an analog manner. Therefore, this shaped pulse also has a correlation with adjacent pulses and changes almost continuously.

Therefore, by considering this correlation, it is possible to obtain a value closer to the truth. According to the peak plot pulse correlation missing portion compensation method based on pulse distribution correlation according to the present invention, more accurate detection can be performed.

〔Example〕

First, the basic configuration of a microwave Doppler radar type speed sensor is shown in FIG.

When microwaves are irradiated from antenna 1 to the road surface at a certain angle, the reflected waves scattered by the road surface are:

The signal undergoes a Doppler frequency shift due to relative motion and is received again by the antenna 1. This Doppler frequency f4 is proportional to the vehicle speed V and the direction cosine C03A, and the transmission frequency f
The relationship with o is given by the following equation.

fov f a = -cosθ ---(1) Smiling C: Speed of light 3 x 10" (m/s) Part of the transmitted wave and the received wave are applied to the mixer diode 3 at the same time 1
The beat caused by the frequency difference between the two signals becomes a Doppler signal. In actual case.

Since the radiation beam of antenna 1 has a width and the reflection from the road surface is irregular, the Doppler waveform is a mixture of multiple frequencies and has a center frequency expressed by equation (1), and its envelope amplitude is A waveform like the one shown in FIG. 2 is formed, which frequently becomes zero. The standard type of conventional speed sensor amplifies this signal wave by the required frequency, then converts the signal that exceeds a certain threshold level considering the signal-to-noise ratio into pulses, and calculates the speed from the number of pulses. , a larger error occurred between the dropout times T1 and T2 of this pulse. Furthermore, in the conventional high-precision speed sensor, the microwave is of a second beam type, and the average width of the detected pulses is calculated and the pulse width is used to compensate for the missing pulse portion. As a result, the accuracy improved significantly to about 1% due to pulse compensation, but recent improvements in detection and control accuracy (about 0%)
．． 5% or more) is becoming unable to meet the demands. Therefore, according to the present invention, the pulse generation frequency in the conventional method is always distributed almost symmetrically around the pulse width τdo, which is expressed as the reciprocal of the Doppler frequency f-, as shown in FIG. 3. However, in the present invention, as shown in FIG.
A so-called two-beam system having two of each 3 is adopted, and the Doppler signal is amplified by an amplifier 4, passed through a filter 9, and a comparator 9 converts the signal exceeding a certain threshold level considering the signal-to-noise ratio into a pulse. Then, the pulse dropout compensation circuits 21 and 22 sequentially write the n pulse widths counted by the counter 12 into the I10RAM, and when the n pulses have been counted, the true value pulse width τdo is symmetrically distributed. Correlation between pulse widths is calculated using a peak plot method, and a pulse width correlation compensator 15 calculates and compensates for pulse missing portions. The resulting number of pulses for each beam is counted by a counter 16, and the number of pulses for each beam is added by an adder 17,
After performing high-precision speed calculations, the display 18 and timing 19 are used to issue necessary displays and signals.

According to this method, since the signal level of the Doppler signal waveform changes continuously in an analog manner, it is assumed that this shaped pulse also changes in a close to continuous manner with a correlation with adjacent pulses, and also based on the actual measurement results. Since pulse width correlation compensation is performed in consideration of the symmetrical distribution of true values, the value becomes even closer to the true value and high accuracy can be obtained. Accuracy verification results show a high accuracy of 0.2%, which is even higher than the current required accuracy of 0.5%. The results are shown in Figure 5. In Figure 5, 2 is a coupler, 5 is a comparator, 6 is an oscillator, 7 is a constant voltage power supply,
8 is Gunn diode, 10 is adder, 11 is I/DRA
M, 13 is a timing circuit, 14 is a pulse width memo, 24
is the calculation section.

〔Effect of the invention〕

According to the present invention, even if the hardware configuration is the same as that of the conventional two-beam method, the width of one generated pulse is analyzed using software, and the missing pulse portion is determined based on the true value symmetric distribution using the peak plot method. Since the compensation is based on so-called pulse width correlation compensation, the accuracy can be improved significantly compared to the conventional method.

[Brief explanation of the drawing]

Fig. 1 is a basic configuration block diagram of a microwave Doppler radar speed sensor, Fig. 2 is an explanatory diagram of processing of Doppler signal waveform, Fig. 3 is an actual measurement diagram of pulse width occurrence frequency distribution, and Fig.
The figure is a block diagram of the configuration of the two-beam microwave Doppler radar speed sensor of the present invention, and FIG. 5 is a comparison diagram of accuracy verification results. 13.19... Timing circuit, 14... Pulse width memory, 15... Pulse width correlation compensator, 16... Counter circuit, 17... Adder, 18... Display section, 2
0.22...Sensor circuit, 21.23...Pulse 2nd port Figure 4 name 5 (2)

Claims (1)

[Claims] 1. Microwaves are irradiated from an antenna to a moving object at a fixed angle, and the reflected waves reflected by the moving object and subjected to a Doppler frequency shift due to relative motion are received again by the antenna. In a Doppler speed sensor that detects speed from the Doppler frequency. When the signal wave does not reach a certain threshold level considering the signal-to-noise ratio, a large number of pulse widths of the shaped pulses of the Doppler signal are stored for the dropped pulse missing portion, and the autocorrelation and distribution correlation of the pulse widths are calculated. A Doppler speed sensor is characterized in that a peak plot pulse correlation missing part compensation method is used to virtually count pulses, and calculations are performed using pulse widths and pulse numbers that are close to the true value.