JPH08292257A - Ultrasonic sensor - Google Patents

Abstract

PURPOSE: To obtain an ultrasonic sensor enabling accurate discrimination, of the presence and absence of a vehicle in a vehicle monitoring space. CONSTITUTION: This ultrasonic sensor is equipped with an ultrasonic transmission control part 5 which emits an ultrasonic pulse from an ultrasonic transmitter-receiver 4, an ultrasonic reception control part 7 which has an amplifier circuit 6 amplifying a reception output of a reflected wave and a detection circuit 8 which has two detection threshold values different in level and outputs first and second detection signals when an output of the amplifier circuit 6 exceeds the individual detection threshold values. Moreover, it is equipped with a detection gate signal generating circuit 9 which generates and outputs a vehicle detection gate signal and a road surface detection gate signal according to the respective reception propagation time of reflected waves from a vehicle and a road surface in relation to the ultrasonic pulse and a vehicle detecting-discriminating circuit 10 which detects the presence or absence of the vehicle on the basis of a combinational logic of the first and second detection signals outputted from the detection circuit 8 and the vehicle detection gate signal and the road surface detection gate signal outputted from the detection gate signal generating circuit 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic sensor for detecting the presence / absence of a vehicle in a surveillance space by emitting an ultrasonic pulse and receiving a reflected wave of the ultrasonic pulse.

[0002]

2. Description of the Related Art Generally, an ultrasonic sensor for detecting a vehicle uses an ultrasonic transducer to transmit an ultrasonic pulse having a predetermined frequency into a monitoring space, and an ultrasonic wave reflected from an object such as a vehicle. The presence of a vehicle or the like is detected by receiving waves with a vibrator. As a vehicle detection system using this ultrasonic sensor for vehicle detection, there is conventionally a vehicle detection system having a basic configuration as shown in the block diagram of FIG. 10, for example.

This vehicle detection system is connected to the ultrasonic wave transmission control section including an ultrasonic wave transmission control section a, an oscillator b, and a wave transmission circuit c, and an ultrasonic transducer (shown in the figure). (Not shown), an ultrasonic wave transmitter / receiver d, an ultrasonic wave receiver / controller connected to the ultrasonic wave transmitter / receiver d, which includes an amplifier circuit e and a detection circuit f, and an ultrasonic wave receiver / controller. And a determination processing unit including a vehicle presence / absence determination circuit g.

In this system, the ultrasonic wave transmission / reception device d is driven by the wave transmission circuit c of the ultrasonic wave transmission control unit to transmit an ultrasonic wave pulse into the monitoring space, and the reflected wave thereof is transmitted to the ultrasonic wave transmission / reception device. d
The signal is received by, the signal is amplified by the amplification circuit of the ultrasonic wave reception control unit, detected by the detection circuit f, and then the presence or absence of an object such as a vehicle is determined by the vehicle presence determination circuit g of the determination processing unit. It has become.

In this system, for example, as shown in FIG. 11, an ultrasonic sensor (ultrasonic wave transmitter / receiver d) is attached right above a parking position where a vehicle C is parked in a parking lot. An ultrasonic pulse of a predetermined frequency is transmitted to the road surface R of the parking lot directly below at an arbitrary timing, and when no object such as a vehicle exists, the transmitted ultrasonic pulse is reflected on the road surface R, The timing at which the reflected wave is received by the ultrasonic sensor, that is, the road surface reflected wave reception time and the vehicle C
Is under the ultrasonic sensor, the ultrasonic pulse transmitted from the ultrasonic sensor is reflected by the vehicle C,
The timing at which the reflected wave is received by the ultrasonic sensor, that is, the vehicle reflected wave reception time is detected, and the time difference between the transmission start time and the road surface reflected wave reception time, the transmission start time and the vehicle reflected wave reception time are detected. The presence or absence of a vehicle is determined by utilizing the difference between the wave time and the time difference.

Incidentally, FIG. 12 is a time chart when the vehicle C exists in the surveillance space.

[0007]

However, in the above-described conventional system, as shown in FIGS. 13 and 14, when an object other than the vehicle C, for example, a human M exists in the vehicle monitoring space, as shown in FIG. As shown in the time chart, there is a problem that the reflection from the person M is detected as the vehicle reflection.

Further, in the ultrasonic sensor, the transmitted ultrasonic pulse is reflected by the vehicle C and the road surface R, the reflected wave is received, and the output obtained by amplifying the received signal by the amplifier circuit e is output. When the detection circuit f exceeds a preset detection threshold value, it is determined that there is a reflected wave from the vehicle or a reflected wave from the road surface. However, due to the influence of wind,
The reflected wave from the vehicle C or the road surface R is not normally received, and the output amplified by the amplifier circuit e fluctuates in the vicinity of the detection threshold value described above, or as shown in FIG. The detection threshold value may or may not be exceeded due to the influence of the windshield FG of the vehicle C in the space, luggage, etc., and the presence or absence of the vehicle C cannot be accurately determined. .

Therefore, in order to solve these problems,
An ultrasonic sensor has been proposed which processes the reflected wave from the vehicle C and the reflected wave from the road surface R in combination. In this type of ultrasonic sensor, for example, when a person M exists in the vehicle monitoring space, both the reflected wave from the vehicle C and the reflected wave from the road surface R are present as shown in FIG. It is determined that the vehicle C does not exist.

Even if the vehicle C is present in the vehicle monitoring space, if it is affected by wind or the windshield FG or luggage of the vehicle C, as shown in FIG. The reflected wave from the road surface R and the reflected wave from the road surface R both disappear, but in this case, there is a reflected wave from the vehicle C and the road surface R
Since there is no reflected wave from the vehicle C and no reflected wave from the road surface R from the state where there is no reflected wave from the vehicle C, there is once a reflected wave from the vehicle C and a reflected wave from the road surface R. The presence of the vehicle C is determined by eliminating the influence of these and detecting the absence of both the reflected wave from the vehicle C and the reflected wave from the road surface R.

However, when the garage is wide, the vehicle C
Is not directly under the ultrasonic sensor, when the threshold value for detecting the reflected wave from the vehicle C and the reflected wave from the road surface R are set to the same level, the road surface R is detected even if the vehicle C exists.
There is a problem in that the presence of the vehicle C cannot be recognized because the reflected wave from does not disappear. Further, as shown in FIG. 18, when the reflection from the road surface R is specified at the time of setting the initial environment, there is an obstacle such as the protrusion TB from the wall KB in the vehicle monitoring space, so that a wave other than the reflected wave from the road surface R is not included. When a plurality of reflected waves occur in the road, there is a problem that the reflected waves from the road surface R cannot be accurately specified. In addition, FIG.
It is a time chart at the time of road surface detection shown in FIG.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide an ultrasonic sensor capable of accurately determining the presence or absence of a vehicle in a vehicle monitoring space.

[0013]

The present invention has been proposed to achieve the above object, and the ultrasonic sensor according to claim 1 drives an ultrasonic wave transmitter / receiver at predetermined intervals. ,
An ultrasonic wave transmission control unit that emits ultrasonic pulses toward the monitoring space, and an ultrasonic wave reception unit that has an amplification circuit that receives the reflected waves of the ultrasonic pulses with an ultrasonic wave transceiver and amplifies the received output. The wave control unit and two detection thresholds having different levels in advance, and when the output of the amplification circuit exceeds the respective detection thresholds, the first and second detection signals (first detection signal) The threshold value is set to be smaller than the second detection threshold value), and the reception wave of the reflected wave from the vehicle or the road surface to the ultrasonic pulse emitted from the ultrasonic wave transmitter / receiver is output. A detection gate signal generation circuit that generates and outputs a vehicle detection gate signal and a road surface detection gate signal according to the time, a first detection signal and a second detection signal detected by the detection circuit, and the detection gate signal. Vehicle detection gate signal output from the generation circuit, road The combination logic of the detection gate signal is obtained by a vehicle detection determination circuit for detecting the presence or absence of the vehicle.

According to another aspect of the ultrasonic sensor of the present invention, in the vehicle detection / discrimination circuit, when the detection circuit outputs the first and second detection signals during the output period of the road surface detection gate signal,
When it is determined that there is no vehicle in the monitoring space, and the detection circuit outputs the first detection signal and does not output the second detection signal during the output period of the vehicle detection gate signal, there is a vehicle in the monitoring space. It is determined to be.

According to another aspect of the ultrasonic sensor of the present invention, when the detection circuit outputs the first and second detection signals during the output period of the road surface detection gate signal at the time of setting the initial environment such as when the power is turned on, It is determined that there is no vehicle. The ultrasonic sensor according to claim 4, wherein the vehicle detection determination circuit does not output the first and second detection signals from the detection circuit during the output period of the road surface detection gate signal,
This is to judge that the orientation of the horn is not proper.

[0016]

According to the ultrasonic sensor of the first aspect, the ultrasonic wave transmission control unit drives the ultrasonic wave transmitter / receiver at a predetermined interval,
An ultrasonic wave pulse is emitted toward the monitoring space, the reflected wave of this ultrasonic wave pulse is received by the ultrasonic wave transmitter / receiver, and the received wave output is amplified by the amplification circuit of the ultrasonic wave reception control unit.

A detection circuit having two detection thresholds having different levels in advance outputs first and second detection signals when the output of the amplifier circuit exceeds the respective detection thresholds. To do. Here, the vehicle detection gate signal and the road surface detection gate signal are output according to the reception propagation time of the reflected wave from the vehicle and the road surface with respect to the ultrasonic pulse emitted from the ultrasonic transmitter / receiver. The presence / absence of a vehicle is detected by a combination logic of the first and second detection signals detected by the vehicle detection gate signal and the road surface detection gate signal output from the detection gate signal generation circuit.

That is, the following judgment is made. If the detection circuit outputs the first and second detection signals during the output period of the road surface detection gate signal, it is determined that there is no vehicle in the monitoring space, while the detection circuit is detected during the output period of the vehicle detection gate signal. Outputs the first detection signal but does not output the second detection signal, it is determined that there is a vehicle in the monitoring space.

In such an ultrasonic sensor of the present invention, with respect to the reflected wave from the road surface, only the reflected wave having a large level reflected directly below the ultrasonic sensor can be detected.
The road surface monitoring area is set to a narrow area immediately below the ultrasonic sensor, but the vehicle monitoring area is not limited to what is reflected by hitting the end of the vehicle or immediately below the ultrasonic sensor, but a relatively wide area. Since the object reflected from the vehicle can also be detected, the substantial road surface monitoring area is set to a wide range including the center and spreading outward.

According to the ultrasonic sensor of the second aspect, the vehicle detection / discrimination circuit is arranged in the monitoring space when the detection circuit outputs the first and second detection signals during the output period of the road surface detection gate signal. When it is determined that there is no vehicle, and the detection circuit outputs the first detection signal and does not output the second detection signal during the output period of the vehicle detection gate signal, it is determined that there is a vehicle in the monitoring space. Therefore, the presence or absence of the vehicle can be accurately determined.

According to the ultrasonic sensor of the third aspect, when the initial environment is set such as when the power is turned on, the detection circuit outputs the first and second detection signals during the output period of the road surface detection gate signal. Since it is sometimes determined that there is no vehicle, even if a wall protrusion or the like is detected in addition to the road surface, this can also be included in the road surface detection range, and the road surface detection by the ultrasonic sensor can be performed accurately. It can be carried out.

According to the ultrasonic sensor of the fourth aspect, the vehicle detection discrimination circuit is fired when the first and second detection signals are not output from the detection circuit during the output period of the road surface detection gate signal. Since the reflected wave for the ultrasonic pulse cannot be detected, the orientation of the horn can be determined to be abnormal. Therefore, it is possible to accurately determine whether the direction of the horn is normal or abnormal by outputting an alarm or the like.

[0023]

Embodiments of the ultrasonic sensor according to the present invention will be described below with reference to the drawings. FIG. 1 shows a basic structure of an ultrasonic sensor 1 according to an embodiment, which has a wave transmission instruction control unit 2, an oscillator 3, and a wave transmission circuit 11, and drives an ultrasonic wave transmitter / receiver 4 at predetermined intervals. Then, an ultrasonic wave transmission control unit 5 that emits an ultrasonic wave pulse toward the monitoring space, and an amplifier circuit 6 that receives the reflected wave of the ultrasonic wave pulse with the ultrasonic wave transmitter / receiver 5 and amplifies the received wave output. It has an ultrasonic wave reception control section 7 and two detection thresholds having different levels in advance, and when the output of the amplification circuit 6 exceeds the respective detection thresholds,
The detection circuit 8 that outputs the first and second detection signals (the first detection threshold value is set smaller than the second detection threshold value) and the ultrasonic wave transmitter / receiver 5 are emitted. A detection gate signal generation circuit 9 that generates and outputs a vehicle detection gate signal and a road surface detection gate signal according to the reception propagation time of the reflected wave from the vehicle and the road surface with respect to the ultrasonic pulse, and the detection circuit 8 detects the wave. A vehicle detection discriminating circuit 10 for detecting the presence or absence of a vehicle by a combinational logic of the first and second detected signals, the vehicle detection gate signal output from the detection gate signal generation circuit 9, and the road surface detection gate signal. It is provided.

In the vehicle detection / discrimination circuit 10, the detection circuit 8 has the first and second detection circuits 8 during the output period of the road surface detection gate signal.
When the detection signal is output, it is determined that there is no vehicle in the monitoring space, and the detection circuit 8 outputs the first detection signal and does not output the second detection signal during the output period of the vehicle detection gate signal. At times, it is determined that there is a vehicle in the monitoring space. Further, when the power is turned on or the like, and the initial environment is set, during the output period of the road surface detection gate signal, the detection circuit 8 causes the first and second detection circuits to operate. When the detection signal is output,
It is designed to determine that there is no vehicle.

Further, the vehicle detection / discrimination circuit 10 operates from the detection circuit 8 to the first and second circuits during the output period of the road surface detection gate signal.
When the detection signal is not output, it is determined that the direction of the horn is not proper. Next, the detection operation of the vehicle, the road surface, etc. by the ultrasonic sensor 1 of this embodiment will be described.

By the ultrasonic wave transmission control unit 5 shown in FIG.
The ultrasonic wave transmitter / receiver 4 is driven at a predetermined interval, and as shown in FIGS. 2, 4, 6, and 8, an ultrasonic wave pulse is emitted toward the monitoring space K, and a reflected wave of this ultrasonic wave pulse is generated. The ultrasonic wave transmitter / receiver 4 receives the waves, and the amplification circuit 6 of the ultrasonic wave reception control unit 7 shown in FIG. 1 amplifies the received wave output. Then, in the detection circuit 8 having two detection thresholds Vth1 and Vth2 having different levels in advance, when the output of the amplifier circuit 6 exceeds the detection thresholds Vth1 and Vth2, the first and second detection thresholds Vth1 and Vth2 are detected. The detection signals K1 and K2 are output (see the time charts in FIGS. 3, 5, 7, and 9).

Here, the vehicle detection gate signal CG and the road surface detection gate signal RG are determined according to the reception propagation time of the reflected wave from the vehicle C and the road surface R with respect to the ultrasonic pulse emitted from the ultrasonic wave transmitter / receiver. Since it is output, the combination logic of the first and second detection signals K1 and K2 detected by the detection circuit 8 and the vehicle detection gate signal CG and the road surface detection gate signal RG output from the detection gate signal generation circuit 9 The presence or absence of a vehicle is detected by the.

That is, the following judgment is made. Figure 6,
As shown in FIG. 7, during the output period of the road surface detection gate signal RG, the detection circuit 8 causes the detection circuit 8 to detect the first and second detection signals K1 (for example, the projection portion TB of the wall KB in the vicinity of the road surface shown in FIG. 6).
It is determined that there is no vehicle in the monitoring space by outputting a detection signal based on a reflected wave from the above) and K2 (a detection signal based on a reflected wave from the road surface R).

On the other hand, as shown in FIGS. 2 and 3, during the output period of the vehicle detection gate signal CG, the detection circuit 8 outputs the first detection signal K1 (the detection signal of the reflected wave from the vehicle C). Does not output the second detection signal K2, it is determined that there is a vehicle in the monitoring space. In the present invention, as shown in FIGS. 4 and 5, with respect to the reflected wave from the road surface R, only the reflected wave having a large level reflected from directly below the ultrasonic sensor 2 by increasing the detection threshold value. Since the road surface monitoring area RE is set to a narrow area immediately below the ultrasonic sensor because the detection is performed, and the detection threshold value is set small for the vehicle monitoring area CE, the vehicle C What is reflected by hitting the end C1 (see FIG. 2) of the vehicle and what is reflected from a relatively wide range is not limited to just under the ultrasonic sensor. Therefore, the road surface monitoring area can be detected. RE is set in a substantially wide range including the center and spreading outward.

When the detection circuit 8 outputs the first and second detection signals K1 and K2 during the output period of the road surface detection gate signal RG, as shown in FIGS. , It is judged that there is no vehicle in the monitoring space, and
As shown in, when the detection circuit 8 outputs the first detection signal K1 and does not output the second detection signal K2 during the output period of the vehicle detection gate signal CG, it is determined that there is a vehicle in the monitoring space. it can.

Further, at the time of setting the initial environment such as when the power is turned on, during the output period of the road surface detection gate signal RG, as shown in FIGS. 6 and 7, the detection circuit 8 causes the first and second detection signals K1 to be detected. , K2 is output, it is determined that there is no vehicle. Therefore, in addition to the road surface R, the protrusion T of the wall KB
Even if B or the like is detected, this can also be included in the range of road surface detection, and the road surface can be detected accurately by the ultrasonic sensor 1.

Further, as shown in FIGS. 8 and 9, the vehicle detection determination circuit 10 outputs the first and second detection signals K1 and K2 from the detection circuit 8 during the output period of the road surface detection gate signal RG. If not performed, the reflected wave for the emitted ultrasonic pulse cannot be detected, so that the orientation of the horn H can be determined to be abnormal, and an alarm can be output to accurately determine whether the orientation of the horn is normal or abnormal.

[0033]

As described above, the ultrasonic sensor of the present invention can accurately determine the presence or absence of a vehicle in the vehicle monitoring space. Particularly, in the ultrasonic sensor according to claim 2, the vehicle detection / discrimination circuit has no vehicle in the monitoring space when the detection circuit outputs the first and second detection signals during the output period of the road surface detection gate signal. When the detection circuit outputs the first detection signal and does not output the second detection signal during the output period of the vehicle detection gate signal, it is determined that the vehicle exists in the monitoring space. Therefore, it is possible to accurately determine whether or not there is a vehicle.

According to the ultrasonic sensor of the present invention, the detection circuit outputs the first and second detection signals during the output period of the road surface detection gate signal when the initial environment is set such as when the power is turned on. Since it is sometimes determined that there is no vehicle, even if a wall protrusion or the like is detected in addition to the road surface, this can also be included in the road surface detection range, and the road surface detection by the ultrasonic sensor can be performed accurately. It can be carried out.

Further, in the ultrasonic sensor according to the fourth aspect, the vehicle detection / discrimination circuit, during the output period of the road surface detection gate signal,
When the first and second detection signals are not output from the detection circuit, the reflected wave for the emitted ultrasonic pulse cannot be detected, so that the direction of the horn is determined to be abnormal and an alarm can be output. Therefore, it is possible to accurately determine whether the direction of the horn is normal or abnormal.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic structure of an embodiment of an ultrasonic sensor according to the present invention.

FIG. 2 is an explanatory diagram showing a state in which a side surface portion of a vehicle is detected by the ultrasonic sensor of the embodiment.

FIG. 3 is a time chart when the vehicle shown in FIG. 2 is detected.

FIG. 4 is an explanatory diagram showing a state where a road surface immediately below is detected by the ultrasonic sensor of the embodiment.

FIG. 5 is a time chart when the road surface shown in the figure is detected.

FIG. 6 is an explanatory diagram showing a state in which a road surface and a wall projection located at a position close to the road surface are detected by the ultrasonic sensor of the embodiment.

FIG. 7 is a time chart at the time of detecting the road surface in FIG.

FIG. 8 is an explanatory diagram at the time of detecting a road surface when the horn of the ultrasonic sensor according to the embodiment has an abnormal orientation.

9 is a time chart at the time of detecting the road surface in FIG.

FIG. 10 is a block diagram showing a basic structure of a conventional ultrasonic sensor.

FIG. 11 is an explanatory diagram showing a state where a conventional ultrasonic sensor is detecting a vehicle.

12 is a time chart at the time of vehicle detection in FIG.

FIG. 13 is an explanatory diagram showing a state in which a human body is being detected by a conventional ultrasonic sensor.

14 is an explanatory view seen from a plane when detecting a human body in FIG. 13. FIG.

15 is a time chart at the time of detecting a human body in FIG.

FIG. 16 is an explanatory diagram showing a problem when a vehicle is moving when a vehicle is detected by a conventional ultrasonic sensor.

17 is a time chart at the time of vehicle detection in FIG.

FIG. 18 is an explanatory diagram showing a state where a conventional ultrasonic sensor is detecting a wall protrusion located at a position close to a road surface.

19 is a flowchart at the time of detecting the road surface in FIG.

[Explanation of symbols]

 1 Ultrasonic Sensor 5 Ultrasonic Wave Transmission Control Unit 6 Amplification Circuit 7 Ultrasonic Wave Reception Control Unit 8 Detection Circuit 9 Detection Gate Signal Generation Circuit 10 Vehicle Detection Discrimination Circuit K1 First Detection Signal K2 Second Detection Signal Vth1 First Detection threshold Vth2 Second detection threshold CG Vehicle detection gate signal RG Road surface detection gate signal C Vehicle R Road surface

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Goro Oda 1048 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works, Ltd.

Claims (4)

[Claims] 1. An ultrasonic wave transmission / reception unit for driving an ultrasonic wave transmitter / receiver at a predetermined interval to emit an ultrasonic wave pulse toward a monitoring space, and a reflected wave of the ultrasonic wave pulse by the ultrasonic wave transmitter / receiver. An ultrasonic wave reception control unit that has an amplification circuit that receives and amplifies the reception output, and two detection thresholds with different levels in advance, and the output of the amplification circuit has the respective detection thresholds. When it exceeds, the first and second detection signals (the first detection threshold is the second
Is set to a value smaller than the detection threshold of), the vehicle for the ultrasonic pulse emitted from the ultrasonic transmitter / receiver, and the reception propagation time of the reflected wave from the road surface, A detection gate signal generation circuit for generating and outputting a vehicle detection gate signal and a road surface detection gate signal, first and second detection signals detected by the detection circuit, and output from the detection gate signal generation circuit An ultrasonic sensor comprising: a vehicle detection determination circuit that detects the presence or absence of a vehicle by a combination logic of a vehicle detection gate signal and a road surface detection gate signal. 2. The vehicle detection / discrimination circuit determines that there is no vehicle in the monitoring space when the detection circuit outputs the first and second detection signals during the output period of the road surface detection gate signal. 2. The vehicle is determined to be present in the monitoring space when the detection circuit outputs the first detection signal and does not output the second detection signal during the output period of the detection gate signal. Ultrasonic sensor. 3. A vehicle is not present when the detection circuit outputs the first and second detection signals during the output period of the road surface detection gate signal at the time of setting the initial environment such as when the power is turned on. 1. The ultrasonic sensor according to 1. 4. The vehicle detection determination circuit determines that the orientation of the horn is not proper when the first and second detection signals are not output from the detection circuit during the output period of the road surface detection gate signal. 1. The ultrasonic sensor according to 1.