JPH0882673A - Ultrasonic distance-measuring apparatus - Google Patents

Abstract

PURPOSE: To obtain an ultrasonic distance-measuring apparatus by which a distance can be measured precisely by a method wherein a threshold value with reference to reflected waves is set at the level of reflected waves with reference to previous ultrasonic waves received at a point of time when next ultrasonic waves are being transmitted. CONSTITUTION: A microcomputer 8 turns on a starting signal F for a definite time, it drives a transmission pulse generator 1 at the timing, it outputs a transmission pulse signal A for a definite time, and it transmits ultrasonic waves for a wave transmitter-receiver 2 to a part within a measuring range. While the signal A is being outputted, a trigger pulse signal B is turned on from a trigger pulse generator 3. A counter circuit 7 is reset at the timing, and it starts a counting operation when the signal is turned off. The microcomputer 8 transmits first ultrasonic waves by the signal F, it reads out a counted value when a transmission time interval has elapsed, it finds a distance up to an object to be measured, it turns on a second signal F, and it transmits ultrasonic waves. When reflected waves at a threshold value Y or higher are received before the second signal F, a comparator 6 outputs a detection signal D, and the counted value of the circuit 7 is held by the signal. As a result, the distance can be computed precisely.

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.

[0002]

2. Description of the Related Art As an ultrasonic distance measuring device, ultrasonic waves are transmitted at a constant transmission time interval, and after the ultrasonic waves are transmitted, reflected waves from an object to be measured which exceed a predetermined threshold value are received. It is known that the distance to the object to be measured is measured by measuring the time until the movement (the round-trip time of ultrasonic waves).

As shown in the timing chart of FIG.
In the conventional ultrasonic distance measuring device, the ultrasonic wave transmission time interval is set to a value longer than the time required for the ultrasonic wave to make a round trip over the maximum measurement distance within the measurement range (maximum measurement distance round trip time).

This is for the following reason.

First, ultrasonic waves are attenuated during propagation, and the degree of the attenuation increases as the propagation distance, that is, the round trip time, becomes longer. Therefore, the level of the reflected wave received is from (a) to (a) of FIG.
As shown in (d), the longer the round trip time, the smaller it becomes. Therefore, if the threshold value for the reflected wave is set too high, the reflected wave reciprocating the maximum measurement distance (see FIG.
The level in (b)) becomes smaller than the threshold value, and this reflected wave cannot be detected. That is, it becomes impossible to measure the maximum measurement distance within the measurement range. Therefore, the threshold value Y is set to a value much lower than the level of the reflected wave received after the maximum measurement distance round trip time. However, in this way, as shown in Fig. 3 (c), even after the maximum measurement distance round trip time has passed,
The level of the reflected wave becomes larger than the threshold value Y. Therefore, if it is assumed that the second ultrasonic wave is transmitted when the maximum distance round-trip time has elapsed from the first ultrasonic wave transmission, the ( The reflected wave like c) is detected and the distance is erroneously measured based on the time from the second ultrasonic transmission. Therefore, the transmission time interval is made sufficiently longer than the maximum distance round trip time, and as shown in (d) of FIG. 3, after the round trip time in which the level of the reflected wave becomes sufficiently smaller than the threshold value Y, the next It is designed to transmit ultrasonic waves. For example,
When the maximum measurement range within the measurement range is 6 m, the transmission time interval is set to the time of reciprocating the distance of 10 m.

[0006]

In the conventional ultrasonic distance measuring device, as described above, since the ultrasonic wave transmission time interval is set to a value considerably longer than the maximum distance round trip time, the distance measurement interval is increased. Becomes longer, the response speed becomes slower, and particularly when the relative speed between the object on which the measuring device is mounted and the object to be measured is large, there is a problem that an accurate distance cannot be measured.

The object of the present invention is to solve the above problems,
It is an object of the present invention to provide an ultrasonic distance measuring device capable of accurately measuring a distance up to a maximum measuring distance within a measuring range, and further shortening an ultrasonic wave transmission time interval as much as possible to enhance a response speed.

[0008]

SUMMARY OF THE INVENTION An ultrasonic distance measuring apparatus according to the present invention transmits an ultrasonic wave at a constant transmission time interval, and after the ultrasonic wave is transmitted, a measured value exceeding a predetermined threshold value is measured. In an ultrasonic distance measuring device that measures the distance to the object to be measured by measuring the time until the reflected wave from the object is received, the threshold value for the reflected wave is the time when the next ultrasonic wave is being transmitted. It is characterized in that it is set to the level of the reflected wave with respect to the ultrasonic wave to which it is received.

For example, the distance measuring device controls the ultrasonic wave transmitting means for transmitting the ultrasonic wave, the ultrasonic wave receiving means for receiving the reflected wave reflected by the object to be measured, and the ultrasonic wave transmitting means. And a processing means for measuring the time from the transmission of the signal to the reception of the reflected wave exceeding the threshold value to obtain the distance to the object to be measured. The ultrasonic wave transmission means includes a transmission pulse generation means for outputting a transmission pulse signal (electrical signal) and a wave transmission means for transmitting the transmission pulse signal as an ultrasonic wave. The ultrasonic wave reception means includes a wave reception means for receiving the reflected wave and converting the reflected wave into a reception signal (electrical signal). A known pulse generator can be used as the transmission pulse generating means. A known wave transmitter can be used as the wave transmitting means. A known wave receiver can be used as the wave receiving means. A wave transmitter / receiver (ultrasonic sensor) that performs both wave transmission and wave reception can also be used as the wave transmitting means and the wave receiving means. The processing means processes the received signal from the wave receiving means to detect that a reflected wave exceeding a threshold is received, and a reflected wave detecting means for transmitting an ultrasonic wave and then a reflection exceeding the threshold. A counting means for counting the time until the wave is received is provided. The reflected wave detection means is provided with threshold value setting means for setting a threshold value for the reflected wave. The threshold setting means is
For example, the threshold value for the reflected wave is set relatively by adjusting the gain of the amplifier circuit for the received signal of the reflected wave from the wave receiving means. The threshold value is set to the level of the reflected wave with respect to the previous ultrasonic wave received at the time of transmitting the next ultrasonic wave. A fixed ultrasonic wave transmission time interval is set in the processing means. As will be described later, this transmission time interval can be made equal to the maximum measurement distance round-trip time in which the ultrasonic waves make a round trip over the maximum measurement distance within the measurement range. The processing means drives the ultrasonic wave transmitting means to transmit ultrasonic waves at every transmission time interval, and at the same time, resets the counting means to start counting. If no reflected wave exceeding the threshold value is received before the transmission time interval elapses after the ultrasonic wave is transmitted, it is determined that there is no DUT within the measurement range. Alternatively, the maximum measurement distance within the measurement range is used as the distance measurement value. When a reflected wave that exceeds the threshold is received before the transmission time interval elapses, counting by the counting means is stopped, and at that time or when the transmission time interval elapses, from the count value of the counting means to the DUT. Find the distance of. It should be noted that the processing means does not detect the reflected wave during the ultrasonic wave transmission, that is, does not judge whether or not the reflected wave exceeding the threshold value is received.

[0010]

In the ultrasonic distance measuring device of the present invention,
The threshold value for the reflected wave is set to the level of the reflected wave for the previous ultrasonic wave that is received at the time when the next ultrasonic wave is being transmitted, so the ultrasonic wave transmission time interval is set to the maximum measurement within the measurement range. The distance can be set to a value equal to the round-trip time, and even in this case, the distance up to the maximum measurement distance within the measurement range can be accurately measured.

The threshold value for the received signal of the reflected wave is 2
It is set to the level of the reflected wave for the first ultrasonic wave received at the time of transmitting the first ultrasonic wave. Therefore, after the first ultrasonic wave is transmitted, the level of the reflected wave for the first ultrasonic wave received during the second ultrasonic wave transmission may or may not exceed the threshold value. However, since the reflected wave is not detected during ultrasonic wave transmission,
There is no possibility that the reflected wave for the first ultrasonic wave is detected during the second ultrasonic wave transmission to make an erroneous measurement. The level of the reflected wave for the first ultrasonic wave received after the second ultrasonic wave transmission is 1 received during the second ultrasonic wave transmission.
It is lower than this level because it is attenuated from the level of the reflected wave for the ultrasonic wave of the second time, and thus lower than the threshold value.
After the second ultrasonic wave transmission, the reflected wave is detected,
Thus, since the level of the reflected wave for the first ultrasonic wave received after the second ultrasonic wave transmission is lower than the threshold value, the reflected wave for the first ultrasonic wave is detected after the second ultrasonic wave transmission. There is no need to make erroneous measurements. Two
Since the level of the reflected wave for the first ultrasonic wave received before the second ultrasonic wave transmission is less attenuated than the level of the reflected wave for the first ultrasonic wave received during the second ultrasonic wave transmission, Higher than this and therefore higher than the threshold. Therefore, the level of the reflected wave received from the first ultrasonic wave transmission until the transmission time interval, that is, the maximum distance round-trip time elapses, is higher than the threshold value and is reliably detected. Therefore, the distance up to the maximum measurement distance within the measurement range can be accurately measured.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of the constitution of the main part of the ultrasonic distance measuring device, and FIG. 2 shows an example of the signal waveform of each part.

In FIG. 1, the measuring device comprises a transmission pulse generator (1), a transceiver (2), a trigger pulse generator (3), an amplifier circuit (4), a gain adjusting circuit (5), a comparator ( 6), counter circuit (7) and microcomputer (microcomputer)
(8) is provided.

The transmission pulse generator (1) constitutes a transmission pulse generating means for outputting a transmission pulse signal A having a constant frequency for a certain period of time at the timing when a control input, which will be described later, is turned on. It can be configured by a vessel. The wave transmitter / receiver (2) includes a wave transmitting means for transmitting the transmission pulse signal A as an ultrasonic wave, and an object to be measured (not shown).
It constitutes a wave receiving means for receiving the reflected wave reflected by and converting it into a received signal, which can be constituted by a known ultrasonic sensor. The transmitting means of the transmitting pulse generator (1) and the transmitting / receiving device (2) constitutes an ultrasonic wave transmitting means for transmitting ultrasonic waves. Transceiver
The wave receiving means (2) constitutes an ultrasonic wave receiving means for receiving the reflected wave.

The trigger pulse generator (3) is for outputting (turning on) the trigger pulse signal B having a constant time width while the transmission pulse signal A is being output. Will be explained in detail later,
Input to the counter circuit (7).

The amplifying circuit (4), the gain adjusting circuit (5) and the comparator (6) are reflected by the reception signal of the transmitter / receiver (2) for detecting the reception of a reflected wave exceeding a threshold value. It constitutes a wave detecting means. The received signal of the wave transmitter / receiver (2) is amplified by the amplifier circuit (4), and the amplified received signal C is input to one input terminal of the comparator (6). A constant threshold value Y is input to the other input terminal of the comparator (6). The amplification circuit (4) and the gain adjustment circuit (5) constitute a threshold value setting means for setting the threshold value, and the gain adjustment circuit (5) must adjust the gain of the amplification circuit (4). Due to
A threshold Y for the received signal C of the reflected wave is set relatively. The comparator (6) outputs (turns on) the reflected wave detection signal D having a constant time width when the level of the received signal C exceeds the threshold value Y. The reflected wave detection signal D is input to the counter circuit (7) as described later in detail.

The counter circuit (7) constitutes a counting means for counting the time from the transmission of the ultrasonic wave to the reception of the reflected wave exceeding the threshold value. The trigger pulse signal B from the trigger pulse generator (3) is input to the reset terminal (R) and start terminal (S) of the counter circuit (7), and the counter circuit (7) turns on the trigger pulse signal B. It is reset at the timing and trigger pulse signal B
Starts counting at the timing when turns off from
Each time a constant clock pulse is input, the count value E increases by one. The reflected wave detection signal D from the comparator (6) is input to the hold terminal (H) of the counter circuit (7), and the count value E output from the counter circuit (7) indicates that the reflected wave detection signal D is on. Will be held at the timing. The count value E of the counter circuit (7) is the microcomputer (8)
To enter.

The microcomputer (8) is for reading the count value E of the counter circuit (7), processing the count value E, and outputting the activation signal F to the transmission pulse generator (1). In the microcomputer (8), a constant value equal to the round trip time of the maximum measuring distance within the measuring range of the measuring device is set as the ultrasonic wave transmission time interval. The microcomputer (8) reads the count value E of the count circuit (7) at every transmission time interval, calculates the distance to the DUT based on this, and immediately after that it starts to transmit ultrasonic waves. The signal F is turned on for a fixed time.

The transmission pulse generator (1) outputs a transmission pulse signal A for ultrasonic transmission at the timing when the activation signal F from the microcomputer (8), which is a control input, is turned on.

Trigger pulse generator (3), amplifier circuit (4),
The gain adjusting circuit (5), the comparator (6), the counter circuit (7) and the microcomputer (8) constitute a processing means.
The processing means is a transmission pulse generator at every transmission time interval.
Controls (1) to transmit ultrasonic waves, and measures the time from the transmission of ultrasonic waves until the reception of a reflected wave that exceeds the threshold value to obtain the distance to the DUT. . During transmission of ultrasonic waves, that is, while the trigger pulse signal B is on, the counter circuit (7) does not count in the reset state, and the reflected wave is not detected.

Next, an example of the operation of the above-mentioned measuring device will be briefly described with reference to the timing charts of FIGS.

In FIG. 2, the microcomputer (8) turns on the activation signal F for a fixed time at every transmission time interval, and at the timing when the activation signal F is turned on, the transmission pulse generator is turned on.
(1) is driven, the transmission pulse signal A is output for a fixed time, and the ultrasonic wave is transmitted from the transducer (2) within the measurement range. Also, while the transmission pulse signal A is being output,
When the trigger pulse signal B from the trigger pulse generator (3) turns on, the counter circuit (7) resets when the trigger pulse signal B turns on, and the counter circuit (when the trigger pulse signal B turns off 7) starts counting, and the count value E increases with the passage of time. On the other hand, the microcomputer (8) turns on the start signal F
At the time when the transmission time interval has elapsed after transmitting the ultrasonic wave for the second time, the count value E of the counting circuit (6) is read, the distance to the DUT is calculated based on this, and immediately after that, The activation signal F is turned on for the second ultrasonic transmission.

As shown in FIG. 2A, before the transmission time interval elapses from the first ultrasonic transmission, that is, before the second ultrasonic transmission, a reflected wave exceeding the threshold value Y is received. Then, the reflected wave detection signal D of the comparator (6) is turned on for a fixed time, and at the timing when this is turned on, the counter circuit (7) stops counting and until the transmission time interval elapses, The count value E is held. Therefore, the count value E read by the microcomputer (8) remains as it is when the reflected wave exceeding the threshold value is received, and the distance to the object to be measured is accurately calculated based on this.

As shown in (b) or (c) of FIG.
Between the second ultrasonic transmission and the second ultrasonic transmission,
When the reflected wave exceeding the threshold value is not received, the reflected wave detection signal D of the comparator (6) remains off, the transmission time interval elapses, and the count value E is read by the microcomputer (8). The counter circuit (7) keeps counting until the count is reached. Therefore, the count value E read by the microcomputer (8) corresponds to the maximum measured distance round trip time, and the maximum measured distance is calculated as the distance measurement value. If a reflected wave exceeding the threshold is not received before the transmission time interval elapses, it should be determined that there is no DUT within the measurement range without calculating the distance. You can also

In the above measuring device, since the threshold value for the reflected wave is set to the level of the reflected wave for the previous ultrasonic wave received at the time point when the next ultrasonic wave is being transmitted, the ultrasonic wave is transmitted. The time interval can be set to a value equal to the maximum measurement distance round trip time within the measurement range, and even in this case, the distance to the maximum measurement distance within the measurement range can be accurately measured.

Also in the case of the above measuring apparatus, the level of the received reflected wave becomes smaller as the round trip time becomes longer, as shown in FIGS. 2 (a) to 2 (c), as in the case of the conventional example. Since the threshold value Y for the reflected wave is set to the level of the reflected wave for the first ultrasonic wave received at the time of transmitting the second ultrasonic wave, as shown in (b) of FIG. After the first ultrasonic wave is transmitted, the level of the reflected wave for the first ultrasonic wave received during the second ultrasonic wave transmission may or may not exceed the threshold value Y. But,
Since the reflected wave is not detected during the ultrasonic wave transmission, there is no possibility that the reflected wave for the first ultrasonic wave is detected during the second ultrasonic wave transmission to make an erroneous measurement. As shown in (c) of FIG. 2, the level of the reflected wave for the first ultrasonic wave received after the second ultrasonic wave transmission is for the first ultrasonic wave received during the second ultrasonic wave transmission. It is lower than this because it is more attenuated than the level of the reflected wave, so
It is lower than the threshold Y. After the second ultrasonic wave transmission, the reflected wave is detected. Thus, since the level of the reflected wave for the first ultrasonic wave received after the second ultrasonic wave transmission is lower than the threshold value Y, 1 after transmitting the second ultrasonic wave
The reflected wave for the ultrasonic wave of the second time is not detected to make an erroneous measurement. As shown in Fig. 2 (a), the level of the reflected wave for the first ultrasonic wave received before the second ultrasonic wave transmission is equal to the level of the first ultrasonic wave received during the second ultrasonic wave transmission. It is higher than this because it is less attenuated than the level of the reflected wave to the sound wave, and therefore higher than the threshold Y. Therefore, the level of the reflected wave received from the first ultrasonic transmission until the transmission time interval, that is, the maximum measured distance round trip time elapses, is higher than the threshold value Y, and is reliably detected. Therefore, it is possible to accurately measure the distance up to the maximum measurement distance within the measurement range.

In the above embodiment, the threshold value for the reflected wave is set relatively by adjusting the gain of the amplifier circuit (4). However, the threshold value itself may be directly adjusted and set. It is also possible.

[0029]

According to the ultrasonic distance measuring apparatus of the present invention, as described above, the ultrasonic wave transmission time interval can be set to a value equal to the maximum measured distance round trip time within the measurement range, and Even in this case, the distance up to the maximum measurement distance within the measurement range can be accurately measured. And
Since the ultrasonic wave transmission time interval can be set to the minimum necessary value that is equal to the maximum measurement distance within the measurement range, the ultrasonic wave transmission time interval can be made as short as possible to increase the response speed. . Therefore, even when the relative speed between the object on which the measuring device is mounted and the object to be measured is large, more accurate distance measurement can be performed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an ultrasonic distance measuring apparatus showing an embodiment of the present invention.

FIG. 2 is a timing chart showing signals of respective parts of the ultrasonic distance measuring device of FIG.

FIG. 3 is a timing chart showing signals of respective parts of a conventional ultrasonic distance measuring device.

[Explanation of symbols]

 (1) Transmit pulse generator (2) Transceiver (3) Trigger pulse generator (4) Amplifying circuit (5) Gain adjusting circuit (6) Comparator (7) Counter circuit (8) Microcomputer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaru Nishizaki 3-5-8 Minamisenba, Chuo-ku, Osaka Koyo Seiko Co., Ltd. (72) Tomoho Kada 3-5-8 Minamisenba, Chuo-ku, Osaka Koyo Within Seiko Co., Ltd. (72) Inventor Yoshifumi Obata 3-5-8 Minamisenba, Chuo-ku, Osaka City Koyo Seiko Co., Ltd.

Claims (2)

[Claims] 1. An ultrasonic wave is transmitted at a constant transmission time interval, and the time from the transmission of the ultrasonic wave to the reception of a reflected wave from an object to be measured which exceeds a predetermined threshold value is measured. In an ultrasonic distance measuring device that measures the distance to the object to be measured, the threshold for the reflected wave is set to the level of the reflected wave for the previous ultrasonic wave that is received at the time when the next ultrasonic wave is being transmitted. An ultrasonic distance measuring device characterized by being provided. 2. The ultrasonic distance measuring apparatus according to claim 1, wherein the threshold value for the reflected wave is set by adjusting the gain of the amplification circuit for the received signal of the reflected wave.