JPS59111063A - Apparatus for detecting speed of moving matter - Google Patents

Abstract

PURPOSE:To accurately measure the speed of moving matter, by providing a means wherein the reflected wave of an ultrasonic signal of which the frequency is continuously changed is passed through a spatial filter to extract a specific frequency component and a signal showing the distance to moving matter is taken out and a means for removing the factor of a distance. CONSTITUTION:The frequency of a transmitted ultrasonic wave is continuously changed at a definite cycle T and the reflected wave from a road surface L received by a receiver 2 is received after a time td while the reflected wave from a vehicle CA is received after a time tv. An optical sensor is also set to a height H and, when the vehicle CA passes a visual field, it is detected by a detector array 3 while the relation of this output signal (g), a speed V and a distance h is given by a formula III wherein K1 is a proportion constant and p is the pitch of a spatial filter. The frequency of the signal (g) is converted to the function only reference to the speed V from formula II, III. By this method, the speed of moving matter can be detected always accurately.

Description

BACKGROUND OF THE INVENTION This invention relates to an apparatus for sensing the speed of a moving object, such as a vehicle, using ultrasound and spatial filters.

A conventional vehicle sensing device using ultrasonic waves includes an ultrasonic transducer installed at a predetermined height above the road surface, and this ultrasonic transducer emits pulsed ultrasonic waves intermittently at a fixed period. It transmits waves toward the road surface, receives the ultrasonic waves that are reflected back from the road surface or the vehicle, and is necessary for the ultrasonic waves to travel back and forth.
The presence or absence of a vehicle was determined by measuring the time it took for the vehicle to pass. The reason why ultrasound is transmitted intermittently is to avoid confusion between the transmitted ultrasound and the reflected ultrasound.
However, after transmitting an ultrasonic wave, it was necessary to wait for the reflected ultrasonic wave to be delivered before transmitting the next ultrasonic wave. For this reason, the ultrasonic wave transmission cycle is a relatively long time, and there is a problem in that accurate vehicle sensing cannot be expected when the vehicle speed is high. For example, if an ultrasonic transducer is installed at a height of 5 m from the road surface, and the speed of sound is 340 m/s, the time required for the ultrasonic waves to travel back and forth between the road surface and the road surface is approximately 30 m5. be. Assuming that the vehicle speed is 1100 K/h and the vehicle length is 4 to 5 m, this vehicle will pass through the vehicle detection point in approximately 150 m5.

Therefore, even if the ultrasonic wave transmission period is increased by 3Qms, sampling can only be performed at a maximum of 5 points for a vehicle running at 1100K/It. Not all of the sampling data is valid, so in reality there will be about three valid data points. With this number of sampling points, vehicle speed,
When measuring vehicle height, etc., large measurement errors occur.

On the other hand, optical vehicle speed detection devices have better linearity than ultrasonic ones because they are not affected by wind, etc., are less affected by temperature changes, and require a larger distance between the sensor and the target vehicle. It has characteristics such as being able to

However, the optical type has the problem that, in principle, when the distance between the sensor and the detection point on the vehicle changes, it is affected by the magnification of the optical system.

In other words, since a vehicle has many uneven surfaces, its height varies depending on the location. If the sensor is placed directly above or diagonally above the vehicle, the distances between the sensor and each part of the vehicle will be different, making it difficult to accurately measure the vehicle speed. Furthermore, since the vehicle height varies depending on the vehicle type, the measurement speed varies depending on the vehicle type, which also makes it difficult to accurately measure the vehicle speed.

Summary of the Invention An object of the present invention is to provide a device that can always accurately detect the speed of a moving object, such as the vehicle speed, regardless of the distance between the vehicle height or the like and the moving object. .

The speed detection device for a moving object according to the present invention includes: means for generating an ultrasonic signal whose frequency is continuously changed; an ultrasonic transmitter continuously driven by the ultrasonic signal;
An ultrasonic receiver receives reflected ultrasonic waves from a moving object, extracts a specific frequency component due to the movement of the moving object through a spatial filter, and converts this into a first electric signal that represents the speed of the moving object and the distance to the moving object. means for converting into a signal, means for frequency demodulating the output signal of the ultrasonic receiver and extracting a signal representing the frequency change, a signal representing the frequency change of the transmitted ultrasonic wave and a frequency change of the received ultrasonic wave. means for extracting a second signal representing the distance to the moving object by comparing it with a Lee signal representing the moving object; and means for removing a no-after representing the distance from the first signal to the moving object by the second signal;
It is characterized by having the following. The detection area of a moving object by ultrasonic waves using an ultrasonic transmitter and receiver and the detection area of an optical moving object using a spatial filter are set at the same location.

In this invention, ultrasonic waves are continuously transmitted to detect moving objects, especially vehicles, and reflected ultrasonic waves from moving objects, road surfaces, vehicles, etc. are continuously received. Continuous transmission and reception of ultrasonic waves is made possible by continuously changing the frequency of the ultrasonic waves, for example, at regular intervals. In this way, information about the moving object, in particular information about the ultrasonic transmission and the distance from the receiver to the moving object, can be obtained continuously. Moreover, the optical moving object detection means using a spatial filter continuously obtains information about the moving object, especially information about the speed of the moving object and the distance to the moving object. In the signal obtained using ultrasound,
Thus, factors relating to the distance to the moving object in the signal obtained using the spatial filter are eliminated. As a result, only one signal representing the speed of the moving object remains, so accurate speed data independent of the distance to the moving object can be obtained.

Other features J5 and detailed configuration of the present invention will become clear in the following description of embodiments with reference to the drawings.

DESCRIPTION OF THE EMBODIMENTS This embodiment shows the case where the present invention is applied to vehicle speed detection.

FIG. 1 shows the arrangement of the ultrasonic transmitter, receiver and optical sensor. Road surface (L) J Specified height H on three sides
An ultrasonic transmitter (1) and an ultrasonic receiver (2) are installed on the holder and fixed to a suitable support member. Ultrasonic waves are transmitted from the transmitter (1) toward the road surface (L),
The receiver (2) receives the ultrasonic waves that are reflected and returned from the road surface (L) or the vehicle (OA>).The frequency of the transmitted ultrasonic waves is constant as shown by the solid line in Figure 2. It changes continuously with a period T. In this example, the change in frequency is a sawtooth wave with respect to time, but any other arbitrary waveform can be adopted. It is preferable that the time required for the ultrasonic wave to travel back and forth between the transmitter, receivers (1) and (2), and the road surface (L) is, for example, 30 m5 or more.The width between the upper and lower limits of the ultrasonic frequency Although it is desirable that the range be wider, there are currently ultrasonic transducers that generate (detect) ultrasonic waves with a substantially constant amplitude (sensitivity) over a band of about 22 to 30 KHz.

In Figure 2, the waveform indicated by the broken line is the waveform of the receiver (2
) shows the change in frequency of the received ultrasound signal. The reflected wave from the road surface (L) is reflected at a time td after ultrasonic wave transmission.
The wave is received when . On the other hand, vehicle <O
The reflected wave from A) is received after time tv (<td). The speed of sound is Vs, transmitter, receiver (1) (2> to vehicle (CA
), the following equation holds true.

td=2H/Vs・・・・・・・・・(1) tv=2b
/Vs------... (2> By comparing the waveforms of the transmitted wave and the received wave shown in Fig. 2, the presence or absence of the vehicle (CA) and the longitudinal cross-sectional shape of the vehicle (CA) can be determined. By measuring the time tv, the distance from the I transmitter and receiver (1) (2) to the vehicle (OA) can be detected.

An optical sensor is also installed at a height H above the road surface. The optical sensor υ includes an optical system including a lens (4) that captures the vehicle (OA) within its field of view, and a detection array (3) that is arranged on the imaging plane of the lens (4) and constitutes a spatial filter.
), J5 and a differential amplifier circuit (5) are built-in. The vehicle sensing area of this optical sensor includes transmitter, receiver (1) and (2)
) is set in the same location as the vehicle sensing area by ultrasonic waves of the sensor. The detector array (3) consists of a large number of elongated photoelectric conversion elements (3a) (3b) arranged alternately in parallel and in a line, and every other photoelectric conversion element is connected to each other, Detector array (3)
Two outputs are taken from. These two outputs are sent to the differential amplifier circuit (5), which
A difference signal ((+)) between the two output signals is output from.

- When a vehicle (CA) passes within the field of view of the optical system, its emitted light (e.g. headlights) or reflected light is detected by the detector array (3), and the height J of the detection point of the vehicle is detected.
3 and the output signal (g
) is obtained from the differential amplifier circuit (5). This output signal (
The relationship between (1> and vehicle speed V and distance l111 to the vehicle) is given by the following equation.

fo = K + V / 1) II ・・・・・・(
3) Here, is the proportionality constant, p is the pitch of the spatial filter, and one photoelectric conversion element (3a) or (3)
b) is the interval between.

It will be easily understood that by removing the weight of Equation (3) by Equation (2), the distance-related component is eliminated, and the frequency of the signal ((1) is converted into a function of only the vehicle speed. .

FIG. 3 shows the electrical configuration of the vehicle speed detection device, and FIG. 4 shows the output signal waveforms of each block of this electric circuit.

The clock signal generation circuit (11) outputs a square wave signal (a) with a constant period T, and this signal (a >
2), it is converted into a sawtooth wave signal (1)). This signal (
b) is input to the voltage controlled oscillation circuit (13). The voltage controlled oscillation circuit (13) has a voltage/frequency conversion function that outputs a signal with a frequency proportional to the input voltage. Oscillation circuit (1
The output signal of step 3) is sent to a power amplification circuit (14), and the ultrasonic transmitter (1) is driven by this amplification circuit (14). In this way, ultrasonic waves whose frequency changes continuously at a constant period of 1, that is, frequency modulated, are sent to the transmitter (1
) is transmitted toward the road surface (L).

・A violation occurs on the road surface <1) or a vehicle (OA), and the receiver (2
) The ultrasonic signal received by the voltage amplification circuit (21
) and then input to the phase comparator circuit (22). This phase comparison circuit (22) is connected to the voltage controlled oscillation circuit (22).
4) The phase of the output signal and the phase of the transfer signal are compared, and a voltage signal corresponding to the phase difference between them is output. This phase difference component is sent to a low pass filter (23) and its high frequency components are removed. The output (C) of the filter (23) controls the oscillation frequency of the voltage controlled oscillation circuit (24). The voltage controlled oscillator circuit (24), the phase comparator circuit (22), and the low-pass filter (23) constitute a phase locked loop (PLL), and this PLL is used here as an FM demodulation circuit. . In this way, a voltage signal <C> proportional to the frequency of the received signal is obtained.

The output signal (1) of the integrating circuit (12) is output from the delay circuit (15).
) is delayed by the above-mentioned time td.

This delayed signal ((1) and demodulated signal (C) are input to the differential amplifier circuit (25), and the difference between them (e) is input to the differential amplifier circuit (25).
) is obtained. The differential J width circuit (25) outputs a signal at the maximum level when the difference between the meat input signals is zero, and outputs a signal at a level lower than the maximum level by the difference when the difference between the two signals is not zero. It has been formatted for output.

Therefore, the output signal (e) represents the time interval from ultrasonic wave transmission to reception, or tv (L, therefore, equation (1), and H or 11) from equation (2). The delay time td is the time required for the ultrasonic waves to travel back and forth over the distance −1lift H between the transmitter and receiver (1), (2) and the road surface (E-), so when there is no vehicle, is both signals (C)
and (d) are isomorphic, and the difference No. 1a (e) is the maximum level.

However, if a vehicle (CA) is present, the signal (e
) shows a shape similar to the longitudinal cross-sectional shape of the vehicle (CA) toward the negative side. The signal (e) is discriminated in a comparator circuit (26) at a suitable threshold level S h to obtain a detection signal (1) representing the presence of a vehicle. This detection signal (i>) is used as a gate control signal for the AND gate (36).

The sound speed Vs changes depending on the temperature, and the time td changes accordingly. In order to prevent malfunctions due to changes in ambient temperature, it is preferable to perform temperature compensation for the delay time td of the delay circuit (15). However, if the threshold level sh is selected in consideration of level fluctuations in the signal (e) due to temperature changes, the temperature compensation circuit is not necessarily required.

The output signal (e) of the differential amplifier circuit (25) is also sent to an analog/digital (A/D) conversion circuit 31) and converted into a digital signal. This digital signal becomes the setting input for the programmable counter (32). If the frequency of the input signal is f, then the frequency of the output signal of the counter (32) is f/N.Then, the setting manual power N is set by the A/D conversion circuit (31). This output is given by the distance from the sensor to the vehicle 11 (or the distance to the road surface 1")
Since it is proportional to , we can set K2 as a constant of proportionality to N=2h...(4).

On the other hand, the output ((+
) is input to the phase comparison circuit (33). This phase comparison circuit (33) compares the phase of the signal (9) and the output signal of the counter 3:L (office), and outputs a voltage according to the phase difference. This phase difference voltage has its high frequency components removed by a low pass filter (34), and then is sent to a voltage controlled oscillation circuit (35) to control its oscillation frequency f. The voltage controlled oscillation circuit (35) is controlled by a closed loop consisting of a programmable counter (32), a phase comparison circuit (33) and a low pass filter (34) so that its oscillation frequency matches f=Nfo. .

When the equation (3) and the equation (/I) are substituted into the above equation [-NfO and the new proportionality constant is set to 3, the frequency f is expressed by the following equation.

f=to,,V... (5) That is,
The frequency f of the output signal (j) of the voltage controlled oscillation circuit (35) has a value proportional only to the vehicle speed V. This signal (
j) is determined by the vehicle detection signal (i) by the AND gate (
36) is taken out as a speed signal (m2) when the gate is opened. The speed signal (n3) is converted into data directly representing the vehicle speed V by a known processing circuit, such as a counter that divides the number of pulses (frequency) of the signal (m) by the number of it.

[Brief explanation of the drawing]

Figure 1 shows the arrangement of the 16-wave transmitter, receiver, and optical sensor; Figure 2 shows the changes in the frequency of the transmitter and receiver; Figure 3 shows the time shift; A block diagram showing the electrical configuration of the sensing device is shown, and FIG. 4 is a time chart showing the output signals of this block diagram. (1)... Ultrasonic transmitter, (2)... Ultrasonic receiver, (3)... Detector array, (5) (25)... Differential amplifier circuit, (11 )...Clock signal generation circuit, (
12)...Integrator circuit, (13) (24) (3
5)... Voltage controlled oscillation circuit, (15)... Delay circuit, (22) (33)... Phase comparison circuit, (23>
(34)...Low pass filter, (26)...
Comparison circuit, (32)...programmable counter. Patent applicant Tateishi Electric Co., Ltd.

Claims (1)

[Claims] Means for generating an ultrasonic signal whose frequency is continuously changed; an ultrasonic transmitter continuously driven by the ultrasonic signal; and a means for receiving reflected ultrasonic waves from a moving object. A means for extracting a specific frequency component due to the movement of a moving object through a spatial filter and converting it into a first electrical signal representing the speed of the moving object and the distance to the moving object; Means for demodulating the frequency of the output signal of the transducer and extracting a signal representing the frequency change, and comparing and moving the signal representing the frequency change of the transmitted ultrasonic wave with the signal representing the frequency change of the received ultrasonic wave. A speed detection device for a moving object, comprising means for taking out a second signal representing the distance to the object, and means for removing a factor representing the distance to the moving object from the first signal by means of the second signal.