JPH02196985A - Ultrasonic distance measuring instrument - Google Patents

Abstract

PURPOSE:To shorten a wait time and to eliminate the influence of multiple reflection, etc., by finding the distance between a master equipment and a slave equipment only when a received signal conforms with the pulse pattern of its sent signal. CONSTITUTION:An ultrasonic wave consisting of a pulse train is sent from the master equipment 1 and received by the slave equipment 2 and then an ultrasonic wave consisting of a pulse grain is sent back to the master equipment 1 from the slave equipment 2 a present specific time later. The distance between the master equipment 1 and slave equipment 2 is measured from the required time from the transmission point of the ultrasonic wave from the master equipment 1 to the reception time of the ultrasonic wave sent back from the slave equipment 2. The master equipment 1 sends a pulse train at certain time and a pulse train in different pattern right after said pulse train and the slave equipment 2 sends a pulse train in the same pattern as the received pulse train pattern back. Further, the master equipment 1 finds the distance only when the sent-back pulse train pattern conforms with the sent pulse train pattern.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an ultrasonic distance measuring device that measures distance by transmitting and receiving ultrasonic waves consisting of a pulse train between a parent device and a slave device. .

(Prior art) This type of distance measuring device using ultrasonic waves is an ultrasonic distance measuring device that transmits and receives ultrasonic pulses between a parent device and a slave device, and measures the distance from the time required for transmission and reception. There is a device. It is known that this ultrasonic distance measuring device has a slower transmission speed than a distance measuring device using light or radio waves, so it can measure distance relatively easily.

One method of such an ultrasonic distance measuring device will be explained using FIGS. 5 and 6. The ultrasonic distance measuring device shown in FIG. 5 is used for vehicle A1. This was used to measure the distance between vehicles A2 and A1. Ultrasonic sensors 1 and 2 are provided at A2. In the following description, for convenience, the ultrasonic sensor 1 of the vehicle Al will be referred to as a parent device, and the ultrasonic sensor 2 of the vehicle A2 will be referred to as a child device. Further, transmission and reception between the master unit 1 and the slave unit 2 are performed using ultrasonic waves consisting of a normal sequence. The ultrasonic wave consisting of the pulse train P+ shown in FIG. 6(a) transmitted from the A device 1 propagates through the air and is received as a wave R after a time delay of L1 as shown in FIG. 6(b). 2 received. After receiving it, the hanging device 2 waits for a time L0 and transmits an ultrasonic wave consisting of a pulse train P2 as shown in FIG. R
It is received as 2. The main unit l has a wave transmission waiting time t of the hanger 2. is given in advance, the distance Aid between the main device 1 and the hanging device 2 can be found as follows: d = (tto) total 2Xc or d. (t, +t2) total 2Xc (where C is the speed of sound) .

[Problems to be Solved by the Invention] However, if the above-mentioned waiting time t0 is shortened in order to shorten the detection time, as shown in FIG. The reflected wave PI (multiple reflections) of the transmitted wave enters the delivery gate G° for the next transmitted ultrasonic wave P, and the distance! The problem was that measurements could be made incorrectly.

The present invention has been made in view of the above points, and its purpose is to provide an ultrasonic distance measuring device that is not affected by multiple reflections even if the waiting time t0 is shortened. There is a particular thing.

[Means to solve the problem]

The present invention transmits ultrasonic waves consisting of a pulse train from a parent device,
After the ultrasonic wave is received by the suspender and a preset predetermined time has elapsed, the suspender sends back an ultrasonic wave consisting of a pulse train to the parent device, and from the point of time when the ultrasonic wave is transmitted from the parent device. , an ultrasonic distance measuring device that measures the distance between the parent device and the hanging device based on the time required for the parent device to receive the ultrasonic waves returned from the hanging device; , the pulse train at a certain time and the pulse train immediately after that are transmitted as a pulse train with a different pattern, the suspension device returns a pulse train with the same pattern as the received pulse train pattern, and the device a transmits a pulse train of a reply pulse train from the suspension device. This method is characterized in that the distance is determined only when the pattern is the same as the transmission pulse train pattern.

[Effect]

In the ultrasonic distance measuring device of the present invention, the transmitting pulse control circuit makes the transmitting pulse pattern from the parent device different from the previous one, and the transmitting pulse pattern from the hanging device is the same as the transmitting pulse pattern from the parent device. Make sure to reply the pulse of
In the parent device, the distance between the parent device and the hanger is determined only when the received wave signal matches the pulse pattern of its own transmitted signal.

(Example) An embodiment of the present invention will be described below.

FIG. 1 is a block diagram showing an embodiment of the ultrasonic distance measuring device of the present invention. The ultrasonic distance measuring device of this embodiment is used for vehicle A1. This was used to measure the distance between vehicles A2 and A1. Ultrasonic sensors 1 and 2 are provided at A2. In addition, in the following description, for convenience, the ultrasonic sensor l of vehicle AI is called the parent device, and the ultrasonic sensor 2 of the vehicle A2 is called a hanger. Further, transmission and reception between the parent device 1 and the hanging device 2 are performed using ultrasonic waves consisting of a pulse train.

In the parent device I, 3 is a transmission pulse control circuit, which determines the pattern of the ultrasonic transmission pulse train based on a signal from a reception circuit 8, which will be described later. As a determining condition, a transmission pulse train having a pattern different from the immediately preceding transmission pulse pattern is generated. FIG. 3 is an example of a pulse train. The time interval between two pulse trains pz and plffi (ultrasonic tone burst waves) is made variable. For example, when setting three types of pulse train patterns, two pulse train pH
, PI3 is defined as time interval 3 in the same figure (a),
The time interval Dz shown in FIG. 6(b) and the time interval Dz shown in FIG. 3(c) may be selected. In addition, Fig. 4 shows another example of a pulse train pattern, in which the pulse train pH is adjusted at regular time intervals.
, P, □, information is sent depending on the presence or absence of pH, as shown in the same figure (
Four types of pulse train patterns are obtained as shown in a) to (d).

4 is a transmitting circuit that generates an ultrasonic signal consisting of a pulse train pattern determined by the transmitting pulse control circuit 3;

Reference numeral 5 denotes a wave transmission drive circuit, which amplifies the ultrasonic signal obtained by the transmission circuit 4 so that it can sufficiently drive the ultrasonic transducer 6. In this embodiment, the ultrasonic transducer 6 is of an integrated type for transmitting and receiving, but it is also possible to use two ultrasonic transducers, one for transmitting waves and one for transmitting waves.

7 is a pulse determination circuit that determines whether the received ultrasonic signal matches the pulse train pattern transmitted this time, and it determines whether the received ultrasonic signal matches the pulse train pattern input from the transmission pulse control circuit 3 and the received ultrasound signal. The pulse train patterns are compared, and if the patterns match, the received signal is sent to the receiving circuit 8, which will be described later, and if not, the received signal is ignored and not sent to the receiving circuit 8.

8 is a receiving circuit which amplifies the received ultrasonic pulse, calculates the distance between the product L and the hanger 2 using the above-mentioned formula from the delay time from transmission, and displays it on a display (not shown) or the like. At the same time, a signal is sent to the transmission pulse control circuit 3 to change the pattern of the next transmission pulse train.

In the hanger 2, the pulse determination circuit 7 identifies the pulse train pattern of the transfer signal, outputs the pattern to the wave transmission pulse control circuit 3, and outputs the transfer signal to the reception circuit 8. The reception circuit 8 amplifies the reception signal output from the pulse determination circuit 7, and sends out a trigger signal to the transmission pulse control circuit 3 after time t4 after receiving the signal. The transmission pulse control circuit 3 transmits the pulse train pattern identified by the pulse determination circuit 7 to the transmission circuit 4 in response to input of a trigger signal from the reception circuit 8 . The transmitting circuit 4 generates an ultrasonic signal having the pulse train pattern. The wave transmission drive circuit 5 amplifies the ultrasonic signal obtained by the transmission circuit 4 so that it can sufficiently drive the ultrasonic transducer 6.

Next, the operation of the above embodiment will be explained.

FIG. 2 is a timing chart for explaining the operation of the ultrasonic distance measuring device of the present invention. In the actual product 1, the transmission circuit 4 generates an ultrasonic pulse train pattern, for example, a pulse train pattern as shown in FIG. 4(b) from the pulse train pattern determined by the transmission pulse control circuit 3, and amplifies it in the transmission drive circuit 5. and transmits it from the ultrasonic transducer 6.

In Fig. 2(a), the actual product 1 has an ultrasonic pulse train P8,
After transmitting Rlg, the reception gate G is opened after waiting for a time t4. This time t4 is for preventing the influence of multiple reflections of the ultrasonic pulses transmitted by the item 1 itself and the hanger 2.

The hanger 2 receives the ultrasonic pulse trains R0 and Rlg from the actual product 1, as shown in FIG. 2(b). At this time, the pattern of the received ultrasonic pulse train R0, Rtz is recognized by the pulse determination circuit 7, and the result is sent to the transmission pulse control circuit 3. In this case, the pattern is a pulse train R with an interval of
8. It is recognized as Rlg. The transmission pulse control circuit 3 determines a return transmission pulse train pattern to be sent to the actual product 1 from the obtained pulse pattern. Then, the determined pulse train is sent to the transmitting circuit 4, and after waiting for a time of L4 after reception, a trigger signal outputted from the receiving circuit 8 is input, and the transmitting circuit 4, the drive circuit 5, and the ultrasonic transducer 6 are activated. An ultrasonic signal is sent back to the actual item 1 via the . This reply ultrasonic pulse train pattern is the same as the transmission pulse train pattern of the actual product 1.

The actual product 1 receives a reply from the hanger 2, but the transmitted wave pulse train p
The following operation is performed for the transfer signal in the transfer gate G that is opened after time t4 after transmitting H, p+z.

The pulse determination circuit 7 determines the received ultrasonic pulse train Rz
, Lx' is input from the transmission pulse control circuit 3, it is determined whether or not it is the same as the pulse train P11% P Ig transmitted this time, and if it is the same, the reception signal is sent to the reception circuit 8, and if not, the reception signal is sent to the reception circuit 8. ignores the received signal and does not send this received signal to the receiving circuit 8. The receiving circuit 8 calculates the distance between the actual item 1 and the hanger 2 based on the received signal input from the pulse determination circuit 7. . Further, the reception circuit 8 sends the next transmission pulse pattern to the transmission pulse control circuit 3, for example, a pattern P8 as shown in FIG. 3(a).
, Rlg, and PI3.

The above operation is repeated, and in FIG. 2, received pulse trains R,, R, (previously transmitted wave P).

, Plff, the reflected wave from a distant object or multiple reflections) is certainly within the receiving gate G, but the previous transmitted pulse train pH, PI! This is the same pattern as the current transmission pulse pH, P18, PI
Since the pattern is different from the pattern corresponding to No. 3, the received signal in this case is not sent to the receiving circuit 8, and therefore the distance based on this received signal is not measured.

In this way, the distance is measured only when the transmitted wave pulse train pattern and the pulse train pattern of the received signal obtained in the transfer gate G match in the master device L, so that after the wave is transmitted, the transmitted wave of the master device 1 is The influence of reflections (multiple reflections, etc.)
It is not as good as the received wave compared to the transmitted wave.

〔Effect of the invention〕

As described above, according to the present invention, an ultrasonic wave consisting of a pulse train is transmitted from a parent device, the ultrasonic wave is received by a suspender,
After a predetermined period of time has elapsed, the suspender sends back an ultrasonic wave consisting of a pulse train to the parent device, and from the time of transmission of the ultrasonic wave from the parent device, the ultrasonic wave returned from the hanger is transmitted to the parent device. In an ultrasonic distance measuring device that measures the distance between the parent device and the hanging device based on the time it takes for the parent device to receive the signal, the parent device determines the difference between a pulse train at a certain time and a pulse train immediately after that. The suspension transmits a pulse train with a different pattern, the suspension device returns a pulse train with the same pattern as the received pulse train pattern, and the parent device:
Since the distance is determined only when the return pulse train pattern from the hanging device is the same as the transmitted pulse train pattern, ultrasonic distance measurement is not affected by multiple reflections even if the waiting time is shortened. Equipment could be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a time chart for explaining the operation of the above, FIGS. 3 and 4 are transmission pulse pattern diagrams according to the above, FIG. 15 is a schematic diagram showing a conventional example, and FIGS. 6 and 7 are time charts for explaining the same operation. 1-.Main device 2-.-Hanger 3-.. Wave transmission pulse control circuit 4--Transmission circuit 5-.. Wave transmission drive circuit 6.-
Ultrasonic transducer 7 - Pulse judgment circuit 8 - Receiving circuit Patent applicant Matsushita Electric Works Co., Ltd. Agent Patent attorney Toshimaru Takemoto (and 2 others) q -No Figure 3 Figure 4

Claims (1)

[Claims] (1) Ultrasonic waves consisting of a pulse train are transmitted from the parent device, the ultrasonic waves are received by the child device, and after a preset period of time has elapsed, the ultrasonic wave consisting of a pulse train is transmitted from the child device to the parent device. and the distance between the parent device and the child device is determined by the time required from the time the ultrasound is transmitted from the parent device until the parent device receives the ultrasound returned from the child device. In an ultrasonic distance measuring device that measures distance, the parent device transmits a pulse train at a certain time and the pulse train immediately after that as a pulse train with a different pattern, and the slave device transmits a pulse train with the same pattern as the received pulse train pattern. In response, the parent device only sends a signal when the reply pulse train pattern from the slave device is the same as the transmitted pulse train pattern.
An ultrasonic distance measuring device characterized by being adapted to determine distance.