KR100336479B1 - Universal signal processing device of ultrasonic traffic detector - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a universal signal processing apparatus of an ultrasonic vehicle detector, wherein the ultrasonic vehicle detector transmits ultrasonic waves by an ultrasonic sensor and receives reflected waves from the vehicle to detect passage of the vehicle, according to an installation height of the ultrasonic sensor. A microcomputer for outputting a generation time and generation period control signal of the wave and a filter adjustment control signal for detecting the reflected wave; A logic circuit for receiving an external clock as an input, counting an external clock, and outputting a signal for driving the ultrasonic sensor according to the generation time and generation period control signal of the transmission wave from the microcomputer using the counted value is implemented. FPGA; And a center frequency, a frequency selectivity (Q factor), and a gain magnitude of the center frequency to be amplified by the filter control control signal by the microcomputer, and receiving a center frequency control signal from the FPGA to obtain a frequency band according to a control signal. It passes only the reflected wave of, characterized in that it comprises a programmable filter implemented as an integrated circuit. The universal signal processing apparatus of the ultrasonic vehicle detector according to the present invention uses a programmable filter that can input and adjust the gain size of the center frequency as a digital signal instead of the conventional tuning oscillator, even if the driving frequency of the ultrasonic sensor changes. You can get the performance you want without changing hardware. In addition, in the present invention, since the programmable filter is implemented as one integrated circuit, it is possible to compensate for the disadvantage of the conventional tuning oscillator implemented as an analog device in which the characteristics of the filter change according to the change of parameters, and the number of resistors and capacitors used It can be reduced to achieve miniaturization and integration of the signal processing board as a whole.

Description

Universal signal processing device of ultrasonic traffic detector

The present invention relates to a signal processing apparatus for an ultrasonic traffic detector, and in particular, it is possible to process ultrasonic signals having different frequencies with a single device by using an integrated programmable filter.

The traffic detector is the bottommost equipment of the traffic management system and is the most basic element for constructing an urgent intelligent transportation system (ITS) to solve traffic congestion.

Vehicle detectors and traffic information collection equipment using ultrasonic sensors are non-embedded and can be installed at a lower price than other equipments.

First, the principle of the ultrasonic traffic detection device will be described.

An ultrasonic sensor including a transmitter and a receiver is installed at a predetermined height from the road surface, periodically transmitting a transmission wave from the ultrasonic sensor, and detecting a reflected wave to detect the passage of the vehicle.

1 is a view for explaining the principle of the ultrasonic traffic detection device.

For example, when the ultrasonic sensor is installed at a height of 6 m from the road surface, the time it takes for the transmission wave emitted from the ultrasonic sensor to return from the ground without a vehicle is about 35 Hz when the sound velocity is 340 Hz. to be. In consideration of this, the transmitter of the ultrasonic sensor periodically emits a transmission wave every 35 ms. During this period, the gate signal is activated as shown in FIG. It is detected within a shorter time. That is, when the reflected wave is detected in the section in which the gate signal is activated, it means the passage of the vehicle.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing apparatus used for such an ultrasonic traffic detector, wherein the signal processing apparatus functions to remove noise, amplify a function, and convert a received reflected wave into a digital signal of an ultrasonic signal generated by an ultrasonic sensor. . In particular, the size of the vehicle reflection wave and the road reflection wave detected by the receiver of the ultrasonic sensor is about tens to hundreds of dB, and various noises are also included, so that the band pass passing only the ultrasonic frequency band to detect the vehicle reflection wave among the received waves. You need a filter and an amplifier to amplify it.

In the prior art, a tuned oscillator is used as a band pass filter for passing only the ultrasonic frequency band. Since the center frequency and bandwidth of such a tuning oscillator are fixed by the circuit elements used, they can be used for only one frequency in the range of 20 kHz to 50 kHz.

Referring to Fig. 2, the prior art of the ultrasonic traffic detector will be described in detail.

Fig. 2 is a block diagram of the ultrasonic traffic detector according to the prior art, which shows the ultrasonic sensor 10 and the signal processing device 20.

Ultrasonic sensors in the range of 20 kHz to 50 kHz are used as the ultrasonic sensor 10 used for vehicle detection. Currently, a 25 kHz ultrasonic sensor and a 26 kHz ultrasonic sensor are mainly used according to the frequency of a signal given as an input. The ultrasonic sensor 10 is composed of a piezoelectric element, and the piezoelectric element vibrates when a voltage is applied thereto, and on the contrary, when the vibration of the element occurs, a corresponding voltage is generated. By using this, transmission and reception functions are possible with one sensor. As such, the two frequency sensors are used to reduce the interference effect by varying the frequency of the ultrasonic sensors used in the adjacent lanes when the ultrasonic traffic detection device is installed in each lane of the multiple lanes.

Since the signal processing apparatus 20 according to the prior art can be applied to only one ultrasonic sensor of one frequency in a single apparatus, the ultrasonic sensor 10 used is 25 Hz or 26 Hz.

In order to drive the ultrasonic sensor 10, a 25 kHz (or 26 kHz) 5Vp-p square wave signal is generated by the microcomputer 21 of the signal processing apparatus 20 and applied to the transmission signal amplifier and receiver 22. .

The transmission signal amplifier and the receiver 21 amplify the square wave signal into a square wave of 70Vpp to transmit to the ultrasonic sensor 10, and serves to receive the reflected wave from the ultrasonic sensor 10.

The tuning oscillator 23 serves to pass only an ultrasonic signal frequency band in order to detect only a vehicle reflection wave from a reception wave including various noises. A circuit diagram of the tuning oscillator 23 used in the prior art is shown in Fig. 3A. Fig. 3B is an equivalent circuit diagram of the tuning oscillator circuit shown in Fig. 3A. The tuning oscillator 23 amplifies the signal through oscillation around the selected frequency, and has a fairly high gain near that frequency. The center frequency of the tuning oscillator is 3dB bandwidth And the gain at the center frequency is g _m R. Where g _m is the transconductance of transistor Q1.

The inverting amplifier 24 amplifies the signal passing through the tuning oscillator 23 using an op-amp. At this time, the amplification ratio can be adjusted according to the situation by using a variable resistor between the input terminal and the output terminal. Passing the inverting amplifier 24, the reflected wave reception signal is large enough to determine whether the vehicle is detected.

The multivibrator 25 is a digital conversion circuit that outputs 5V when the reflected wave signal is greater than or equal to a predetermined magnitude and 0V or less for processing the input reflected wave signal by the microcomputer 21.

Sensor height adjustment switch 26 is adjusted in 8 steps from 0 to 7, depending on the height of the sensor is installed, the installation height is usually 5-6m. Since the time taken to return the reflected wave will vary according to the height of the sensor, the microcomputer 21 adjusts the ultrasonic firing cycle according to the output signal of the sensor height adjustment switch 26.

The detection signal output unit 27 outputs an HIGH signal when the vehicle passes, and an OFF signal otherwise.

In this prior art configuration, the tuning oscillator 23 determines the center frequency and its bandwidth according to the C, R, L values of the circuit used. Therefore, once manufactured and having a C, R, L value, the oscillator cannot be used when the frequency of the ultrasonic sensor used is changed. That is, it can be used only for one frequency of 25 kHz or 26 kHz. In addition, there is a problem that the center frequency is fluctuated due to the natural fluctuation of the C, R, and L values.

The present invention is to solve the problems of the prior art as described above, the object of the present invention can be applied universally to the variation of the frequency, so that the ultrasonic signal having a frequency selected in the range of 20 kHz to 50 kHz to a single device It is an object of the present invention to provide a signal processing apparatus for an ultrasonic vehicle detector that can be processed.

1 is a view for explaining the principle of the ultrasonic traffic detection device;

2 is a block diagram of an ultrasonic traffic detector according to the prior art;

3A is a circuit diagram of a tuning oscillator used in the prior art;

3B is an equivalent circuit diagram of FIG. 3A;

4 is a block diagram of an ultrasonic traffic detector according to the present invention;

5 is an input / output diagram of a field programmable gate array (FPGA) for generating a 5 Vpp square wave;

6 is a circuit diagram of an IC filter as an example of implementing a programmable filter used in the present invention;

Fig. 7 shows an example of the installation of the ultrasonic traffic detector according to the present invention, which is installed on the variable information board.

8 is an example of installation of an ultrasonic traffic detector according to the present invention, which shows the case where it is installed in an overpass facility;

Fig. 9 shows an example of installation of an ultrasonic traffic detector according to the present invention, which is installed in a traffic light facility.

Fig. 10 shows an example of installation of an ultrasonic traffic detector according to the present invention, which is installed in a street lamp.

* Explanation of symbols on the main parts of the drawings *

10,30: ultrasonic sensor 20,40: ultrasonic signal processing device

21,41: Microcomputer 22,43: Transmission signal amplifier and receiver

23: tuning oscillator 24,45: inverting amplifier

25,46: Multivibrator 26,47: Sensor height adjustment switch

27,48: detection signal output unit

42: Field Programmable Gate Array

44: Programmable Filter

In order to achieve the above object, the universal signal processing apparatus of the ultrasonic vehicle detector according to the present invention, in the ultrasonic vehicle detector for transmitting the ultrasonic wave by the ultrasonic sensor and receiving the reflected wave by the vehicle to detect the passage of the vehicle, A microcomputer that outputs a generation time and a generation period control signal of a transmission wave and a filter adjustment control signal for detecting a reflected wave according to an installation height of the ultrasonic sensor; A logic circuit for receiving an external clock as an input, counting the external clock, and outputting a signal for driving the ultrasonic sensor according to the generation time and generation period control signal of the transmission wave from the microcomputer using the counted value is implemented. FPGA; And a center frequency, a frequency selectivity (Q factor), and a gain magnitude of the center frequency to be amplified by the filter control control signal by the microcomputer, and receiving a center frequency control signal from the FPGA to obtain a frequency band according to a control signal. It passes only the reflected wave of, characterized in that it comprises a programmable filter implemented as an integrated circuit.

In addition, the FPGA is provided with a plurality of channel functions to output ultrasonic sensor driving signals of different frequencies, and to pass only the reflected wave signal of the corresponding frequency according to the center frequency control signal respectively output from the FPGA to the plurality of channels. A plurality of programmable filters corresponding to each channel of the FPGA may be provided.

Hereinafter, a universal signal processing apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

4 is a block diagram of the ultrasonic traffic detector according to the present invention, showing the ultrasonic sensor 30 and the universal signal processing device 40. As shown in FIG.

Since the signal processing device 40 according to the present invention is a single device and can be applied to all frequency ranges of 20 kHz to 50 kHz, it is called a universal signal processing device. The universal signal processing apparatus according to the present invention can be applied to both 25 kHz and 26 kHz ultrasonic sensors which are mainly used at present, and therefore, both 25 kHz and 26 kHz can be used as the ultrasonic sensor 30.

In the conventional ultrasonic processing apparatus 20 shown in FIG. 2, the microcomputer 21 generates a square wave for driving the ultrasonic sensor. In the ultrasonic processing apparatus 40 according to the present invention, the microcomputer is an FPGA 42. Only time and periodic control signals for square wave generation are transmitted, and the square wave causes the FPGA 42 to be generated by the control signal. The FPGA 42 allows a logic circuit to be implemented through programming. The FPGA 42 according to the present invention counts an externally input clock and generates a transmission wave from a microcomputer using the clocked value. The 5Vpp square wave is generated by the time and generation period control signal. For example, if an external clock is input at intervals of 0.1 milliseconds, and the microcomputer's control signal instructs to generate square waves for driving at intervals of 1 milliseconds, the FPGA generates a square wave every 10 times the clock is counted.

In general, to generate a square wave in the microcomputer, the internal timer interrupt of the microcomputer should be used. For example, since the oscillation period is 25 ms and 38 ms respectively, the microcomputer generates a signal of at least 1.6 ms. It must operate to have a resolution of M. Therefore, the burden of the microcomputer may increase. In addition, the number of internal timers is limited and the number of output ports is limited, and considering the case of driving two sensors with a single microcomputer, the microcomputer only outputs a proper control signal. Alternatively, it would be advantageous to create a high-speed oscillation signal of 26 Hz. In addition, through this, elements around the microcomputer can be integrated and used as a control signal source of the programmable pulser 33.

5 is an input / output diagram of an FPGA for generating a 5 Vpp square wave.

An 8 MHz clock with a 0.125 Hz period is input, and a 25 MHz square wave with a 40 Hz period or a 26 MHz square wave with a 38.4 Hz period is used. For this purpose, a pulse is generated every time 160 counts (40 / 0.125) in the case of 25 Hz and every count 152 (38.4 / 0.125) in the case of 26 Hz to obtain a square wave of 5 Vpp of each frequency.

In an ultrasonic vehicle detector, in general, it generates a transmission wave for 2 ms, and then does not generate a transmission wave for about 33 ms waiting for a reflected wave thereafter, since this period varies depending on the installation height of the sensor. To adjust it.

The sensor height adjustment switch 47 applies an output signal corresponding to the height at which the sensor is installed to the microcomputer 41, and the microcomputer 41 generates a time and generation of a suitable transmission wave according to the output signal of the sensor height adjustment switch 47. The period control signal is applied to the FPGA 42, and the FPGA 42 generates a square wave having a frequency within a range of 20 Hz to 50 Hz in accordance with the control signal from the microcomputer 41 to generate the square wave generation period in the microcomputer 41. It can be controlled and at the same time relieves the burden of generating square waves directly.

The transmission signal amplifier and the receiver 43 amplify the obtained square wave and transmit the amplified square wave to the ultrasonic sensor 30 and receive the reflected wave from the ultrasonic sensor 30.

The programmable filter 44 serves to pass only the ultrasonic frequency band of the ultrasonic sensor used to detect only the vehicle reflected wave from the received wave having a small reflected wave and containing various noises.

The programmable filter 44 used in the present invention is an integrated band pass filter that can control the performance of the microcomputer 41. In other words, since the programmable filter 44 can determine the center frequency, the frequency selectivity (Q factor), the gain magnitude of the center frequency, etc., as a digital signal from the microcomputer, and the driving frequency of the ultrasonic sensor changes. Get the performance you want without changing your new hardware.

According to the above characteristics, the characteristics of the programmable filter 44 can be changed even at a remote location, and the performance of the system can be adapted to the situation because the characteristics of the filter are not fixed but variable.

In addition, since the programmable filter 44 used in the present invention is implemented as one integrated circuit, it is possible to compensate for the disadvantages of the conventional tuning oscillator implemented as an analog device in which the characteristics of the filter change according to the change of parameters. The number of resistors and capacitors to be reduced can be achieved to miniaturize and integrate the signal processing apparatus as a whole.

6 is a circuit diagram of an IC filter as an example of implementing a programmable filter used in the present invention.

In addition, the inverting amplifier 45 for amplifying the reflected wave reception signal, the multivibrator 46 which is a digital conversion circuit which outputs 5V if the reflected wave signal is greater than or equal to a predetermined magnitude, and 0V or less according to the magnitude of the reflected wave signal, and the vehicle passes. The function of the detection signal output unit 48 that outputs an ON (HIGH) and other OFF (LOW) signals at the time is the same as in the prior art.

7 to 9 are installation examples of the ultrasonic traffic detector according to the present invention, FIG. 7 is installed in a variable information board, FIG. 8 is installed in an overpass facility, and FIG. 9 is installed in a traffic light facility. 10 shows the case where it is installed in the street lamp, respectively.

As described above, in the universal signal processing apparatus of the ultrasonic vehicle detector according to the present invention, instead of the conventional tuning oscillator, the ultrasonic sensor is driven by using a programmable filter which can input and adjust the gain size of the center frequency as a digital signal. Even if the frequency changes, the desired performance can be achieved without changing the new hardware. In addition, in the present invention, since the programmable filter is implemented as one integrated circuit, it is possible to compensate for the disadvantage of the conventional tuning oscillator implemented as an analog device in which the characteristics of the filter change according to the change of parameters, and the number of resistors and capacitors used It can be reduced to achieve miniaturization and integration of the signal processing board as a whole.

In addition, according to the universal signal processing apparatus according to the present invention, since it can be applied to ultrasonic waves having a frequency in the range of 20 kHz to 50 kHz, two ultrasonic frequency sensors, 25 kHz and 26 kHz, which are mainly used, are used in one board. For processing, you can build a universal board that includes a single microcomputer that integrates the redundant functions of two microcomputers.

Claims (3)

In the ultrasonic vehicle detector for transmitting the ultrasonic wave by the ultrasonic sensor and receiving the reflected wave by the vehicle to detect the passage of the vehicle, A microcomputer that outputs a generation time and a generation period control signal of a transmission wave and a filter adjustment control signal for detecting a reflected wave according to an installation height of the ultrasonic sensor; A logic circuit for receiving an external clock as an input, counting an external clock, and outputting a signal for driving the ultrasonic sensor according to a generation time and a generation period control signal of the transmission wave from the microcomputer using the counted value is implemented. FPGA; And The center frequency, the frequency selectivity (Q factor), and the gain magnitude of the center frequency to be amplified by the filter control control signal by the microcomputer are determined, and the center frequency control signal is received from the FPGA to determine the frequency band according to the control signal. The universal signal processing device of the ultrasonic vehicle detector, characterized in that it comprises a programmable filter that passes only the reflected wave, and implemented as an integrated circuit. The method of claim 1, The FPGA is provided with a plurality of channel functions to output ultrasonic sensor drive signals of different frequencies, Universal signal processing of the ultrasonic vehicle detector is provided with a plurality of programmable filters corresponding to each channel of the FPGA so that only the reflected wave signal of the corresponding frequency is passed in accordance with the center frequency control signal respectively output to the plurality of channels by the FPGA. Device. The method according to claim 1 or 2, The universal signal processing device is a universal signal processing device of the ultrasonic vehicle detector, characterized in that installed in a variable information plate, overpass facilities, signage facilities, traffic light facilities or street lights.