JPH07280932A - Ultrasonic distance-measuring apparatus - Google Patents

Abstract

PURPOSE:To avoid that a human being or an animal is subjected continuously to high-output ultrasonic waves at a short distance. CONSTITUTION:The ultrasonic distance-measuring apparatus is provided with a transmitter 1 which transmits ultrasonic waves, a gain-variable amplifier 2 which outputs a driving voltage to the transmitter 1 and whose amplification degree is variable, an oscillator 3 which outputs a burst-like signal, a receiver 4 which receives reflected waves from an object 7 whose distance is to be measured and a signal processing circuit 6 which outputs an oscillating trigger signal 101 to the oscillator 3, which gives a gain instruction signal 102 determining a gain to the gain-variable amplifier 2, which measures the time elapsed until a receiving operation from a transmitting operation and which computes a distance. The signal processing circuit 6 outputs, to the gain amplifier 2, the gain instruction signal 102 which changes the sound pressure of the ultrasonic waves, to be transmitted, according to a distance from the measured object which is to be measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic distance measuring device which transmits ultrasonic pulses, receives reflected waves from an object, and detects the distance to the object.

[0002]

2. Description of the Related Art Conventionally, various measuring devices using a distance sensor using ultrasonic waves, a sensor attached to a moving body to detect the distance from the periphery of the moving body, or an ultrasonic detector to detect irregularities on a traveling road surface have been available. It has been commercialized. When measuring distance using ultrasonic waves, burst-type ultrasonic waves with a constant output sound pressure are emitted to the distance measurement target, the reflected wave from the target is received, and its propagation time is measured to measure the distance. The method is common.

Further, the ultrasonic wave emission period is generally constant regardless of the measurement distance.

[0004]

The conventional ultrasonic distance measuring device has the following problems.

(1) An ultrasonic distance sensor attached to a moving body, for example, an automobile is used outdoors, and various distance measurement targets include automobiles, two-wheeled vehicles, people, animals such as pets, and buildings. Moreover, in order to measure a distance of 10 m or more, it is necessary to output high-power ultrasonic waves. Therefore, it is assumed that a person receives a high-power ultrasonic wave at a very short distance. It has been reported in the literature that it is not desirable for an organism to continue to receive high-power ultrasonic waves, and depending on the frequency, it may be unpleasant if it continues to receive high-power ultrasonic waves.

[0006] A first object of the present invention is to reduce the chance that a human or animal will continue to receive high-power ultrasonic waves at a short distance.

(2) Further, if the cycle of transmitting the ultrasonic pulse is constant, it is necessary to set the maximum measurement distance to be equal to or longer than the time required for the ultrasonic wave to make a round trip. At that time, when the distance of a short-distance target is measured, the received wave arrives at the receiver earlier, and therefore a large part of the transmission cycle becomes unnecessary time for distance measurement.

An object of the present invention is to optimize the transmission cycle according to the measurement distance and improve the reliability of distance measurement.

[0009]

An ultrasonic distance measuring apparatus of the present invention for solving the above-mentioned problems transmits an ultrasonic pulse, receives a reflected wave from an object, and measures the distance to the object. In the ultrasonic distance measuring device for detecting, a transmitter for transmitting ultrasonic waves to the object to be measured, a driving voltage output to the transmitter, and a variable gain amplifier with variable amplification degree and an oscillator for outputting a burst signal. A receiver for receiving a reflected wave from the object to be measured, a receiving circuit for amplifying the signal, a trigger signal for oscillation output to the oscillator, and a gain command signal for determining a gain to the variable gain amplifier, An ultrasonic wave to be transmitted by measuring the time from transmission to reception and including a signal processing circuit for calculating the distance, and changing the gain command signal in accordance with the distance from the object to be measured in the signal processing circuit. It is intended to change the sound pressure.

Alternatively, in an ultrasonic distance measuring device that transmits an ultrasonic pulse, receives a reflected wave from an object, and detects the distance to the object, a transmitter that transmits the ultrasonic wave to a distance measurement target. A gain variable amplifier that outputs a drive voltage to the transmitter and that has a variable amplification degree, an oscillator that outputs a burst signal, a receiver that receives a reflected wave from the object to be measured, and a receiver that amplifies the signal A circuit and a signal processing circuit that outputs an oscillation trigger signal to the oscillator, applies a gain command signal that determines the gain to the variable gain amplifier, measures the time from transmission to reception, and calculates the distance The gain command signal is changed in accordance with the maximum value of the received sound pressure measured by the signal processing circuit to change the sound pressure of ultrasonic waves to be transmitted.

Alternatively, in an ultrasonic distance measuring device that transmits an ultrasonic pulse, receives a reflected wave from an object, and detects the distance to the object, a transmitter that transmits the ultrasonic wave to a distance measurement target. A variable amplifier that outputs a drive voltage to the transmitter, an oscillator that outputs a burst signal, a receiver that receives a reflected wave from the object to be measured, a receiving circuit that amplifies the signal, and an oscillator that oscillates to the oscillator. Output the trigger signal,
A gain command signal that determines the gain is given to the variable gain amplifier, a signal processing circuit that measures the time from transmission to reception and calculates the distance, and changes the ultrasonic wave transmission cycle according to the measured distance It is what makes me.

[0012]

According to the above means, when the distance measurement result by the ultrasonic wave is small, the output sound pressure of the ultrasonic wave received by the object is reduced.

On the other hand, when the distance measurement result is large, there is no object nearby and the ultrasonic wave has a large round trip distance, so the output sound pressure of the ultrasonic wave is increased.

As a result, when a human or an animal approaches the ultrasonic transmitter, the distance measured by the ultrasonic wave gradually decreases. As the measuring distance decreases, the transmission output is reduced, so that the human or the animal has a large output nearby. The chance of receiving ultrasound is greatly reduced.

Further, by changing the transmission cycle in accordance with the measured distance, the transmission cycle can be shortened for the near object, and as a result, the closer the object to be measured, the more frequently the distance can be measured.

[0016]

EXAMPLES Details of the present invention will be described below with reference to examples. FIG. 1 shows the configuration of the first embodiment of the present invention.

1 is a transmitter, 2 is a variable gain amplifier, 3 is an oscillator, 4 is a receiver, 5 is a receiving circuit, 6 is a signal processing circuit, and 7 is an object to be measured.

When measuring the distance, the signal processing circuit 6
The oscillation trigger 101 is applied to the oscillator 3, and the oscillator 6 outputs to the variable gain amplifier 2 a sine wave signal 103 having a constant amplitude of several tens of waves.

The signal processing circuit 6 outputs the gain command signal 102 to the variable gain amplifier 103, and the sine wave signal 103 of several tens of waves is amplified by the commanded gain to become the transmitter drive signal 105, and the transmitter 1 To transmit the transmitted ultrasonic wave 8.

The transmitted ultrasonic wave 8 is reflected by the object 7 to be measured and becomes a reflected wave 9 which is received by the receiver 4. The received reflected wave 9 is amplified and detected by the receiving circuit 5 and input to the signal processing circuit 6.

Inside the signal processing circuit, the time from the output of the oscillation trigger to the reception of the received wave of a predetermined value or more is measured. By multiplying this time by the sound velocity and dividing by 2, the distance L to the measurement target 7 is calculated. This process is, for example, A / D
It can be realized by circuits and software equipped with converters, D / A converters, and microprocessors.

FIG. 2 shows an example of the received wave when the reflected wave is received after the transmission trigger is output. At this time, as shown in FIG. 3, the gain command signal 102 is changed according to the measurement distance L.

In this way, when there is an object at a short distance, the gain of the variable gain amplifier becomes low, the amplitude of the transmitter drive signal 105 becomes small, and the ultrasonic wave output from the transmitter 1 becomes small.

On the other hand, when the measurement distance is large, the gain command signal 102 is set large, the amplitude of the transmitter drive signal 105 is large, and the ultrasonic wave output from the transmitter 1 is large.

As a result, when the object approaches a relatively short distance from a far distance, the object may receive a high-power ultrasonic wave at first, but if the measurement distance becomes short, the ultrasonic wave will be measured at the next distance measurement. It is possible to avoid that humans and animals continue to receive high-power ultrasonic waves at a short distance because the output power of the power source decreases.

FIG. 4 shows in the signal processing circuit of the second embodiment,
FIG. 6 is a diagram showing that the gain command signal 106 is determined based on the difference between the received sound pressure set value in which the gain command signal is preset and the maximum value of the observed received sound pressure. The other functions are the same as those in the first embodiment described above, and will be omitted.

When the maximum value of the received sound pressure is smaller than the set value of the received sound pressure, the gain is increased according to FIG. 4 to increase the sound pressure at the next transmission, and the received sound pressure is larger than that at the previous measurement. To be

On the contrary, in order to make the maximum value of the received sound pressure larger than the set value of the received sound pressure, the gain command signal 102 is decreased according to FIG. Make it smaller than the previous measurement.

In this way, the gain command signal 106 is changed so that the magnitude of the received sound pressure approaches the predetermined value. In this embodiment, a limiter is provided for the gain command signal in order to prevent the drive signal from becoming too large or the transmitted sound pressure from becoming too small so that measurement becomes impossible.

With this configuration, when a person receives a high-power ultrasonic wave while the person is near the transmitter, the reflected wave becomes larger than the received sound pressure set value, and as a result, the ultrasonic wave is measured at the next distance measurement. It is possible to avoid that humans and animals continue to receive high-power ultrasonic waves at a short distance because the output power of the power source decreases.

FIG. 5 is a graph showing the relationship between the transmission period and the measured distance in the third embodiment. The solid line is an example of the setting of the transmission cycle according to the measurement distance used in this example,
The dotted line is the time required for the ultrasonic waves to travel back and forth over the measurement distance.

As an example, if a transmission cycle is a sum of a time required for a round trip and a fixed time, the distance is measured at an optimum transmission cycle according to the measured distance. That is, distance measurement is frequently performed with a short transmission cycle in short-distance measurement, and long-distance measurement can be performed with a necessary minimum time transmission cycle according to the distance.

[0033]

As described above, according to the present invention, an amplifier which outputs a drive voltage of a transmitter depending on a distance measured by ultrasonic waves or an error between a maximum value of received sound pressure and a predetermined value of received sound pressure. Change the gain command signal of, the ultrasonic output becomes small when it is in the distance measurement object near the transmitter, it is possible to avoid that humans and animals continue to receive high output ultrasonic waves at a short distance, Its practical effect is extremely large.

Alternatively, there is an advantage that the distance can be measured as frequently as possible according to the distance to the object to be measured, and its practical effect is great.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is a sound pressure waveform diagram of a received reflected wave in the example.

FIG. 3 is a gain command signal diagram in the embodiment.

FIG. 4 is an explanatory diagram of setting of a gain command voltage in the second embodiment of the present invention.

FIG. 5 is an explanatory diagram of a measurement distance and a transmission cycle according to the third embodiment of the present invention.

[Explanation of symbols]

 1 transmitter 2 variable gain amplifier 3 oscillator 4 receiver 5 receiving circuit 6 signal processing circuit 7 measurement target 8 transmitted ultrasonic wave 9 reflected wave 101 oscillation trigger 102 gain command signal 103 sine wave signal 105 transmitter drive signal

Claims (6)

[Claims] 1. An ultrasonic distance measuring device that transmits an ultrasonic pulse, receives a reflected wave from a measurement target, and detects a distance to the measurement target, and transmits ultrasonic waves to the distance measurement target. , A variable gain amplifier that outputs a driving voltage to the transmitter and has a variable amplification degree, an oscillator that outputs a burst signal, a receiver that receives a reflected wave from the object to be measured, and its signal A signal that outputs a trigger signal for oscillation to the oscillator and a gain command signal that determines the gain to the variable gain amplifier, measures the time from transmission to reception, and calculates the distance. And a processing circuit, wherein the signal processing circuit outputs a gain command signal for changing the sound pressure of ultrasonic waves to be transmitted to the gain variable amplifier, according to the measured distance from the object to be measured. Sound wave Away measurement device. 2. A variable gain amplifier which outputs a gain command signal from a signal processing circuit, such that the sound pressure of the ultrasonic wave to be transmitted is smaller as the measurement distance is smaller, and the sound pressure of the ultrasonic wave is larger as the measurement distance is larger. The ultrasonic distance measuring device according to claim 1, wherein the ultrasonic distance measuring device is output. 3. An ultrasonic distance measuring device that transmits an ultrasonic pulse, receives a reflected wave from a measurement target, and detects a distance to the measurement target, and transmits ultrasonic waves to the distance measurement target. A variable gain amplifier that outputs a driving voltage to the transmitter and has a variable amplification degree, an oscillator that outputs a burst signal, and a receiver that receives a reflected wave from the object to be measured, A reception circuit that amplifies a signal and an oscillation trigger signal are output to the oscillator, a gain command signal that determines the gain is given to the gain variable amplifier, the time from transmission to reception is measured, and the distance is calculated. A signal processing circuit, wherein the signal processing circuit outputs a gain command signal for changing the sound pressure of ultrasonic waves to be transmitted to the gain variable amplifier according to the magnitude of the maximum value of the received sound pressure measured. Features Ultrasonic distance measuring device. 4. The ultrasonic distance measuring device according to claim 3, wherein the gain command signal is given in proportion to the difference between the predetermined value of the received sound pressure and the maximum value of the received sound pressure. 5. An ultrasonic distance measuring device that transmits an ultrasonic pulse, receives a reflected wave from a measurement target, and detects a distance to the measurement target, and transmits ultrasonic waves to the distance measurement target. Amplifier, a variable amplifier that outputs a drive voltage to the transmitter, an oscillator that outputs a burst-shaped signal, a receiver that receives a reflected wave from the target object, a receiving circuit that amplifies the signal, and the oscillator. An oscillation trigger signal is output, a gain command signal that determines the gain is given to the variable gain amplifier, the time from transmission to reception is measured, and a signal processing circuit that calculates the distance is provided. An ultrasonic distance measuring device characterized in that it changes according to the measured distance. 6. The ultrasonic distance measuring apparatus according to claim 5, wherein the transmission cycle is decreased as the measurement distance is smaller, and the transmission cycle is increased as the measurement distance is larger.