JP2658361B2 - Ultrasonic distance measuring device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic distance measuring apparatus for transmitting and receiving an ultrasonic wave composed of a pulse train between a parent device and a child device to measure a distance. .

[Conventional technology]

As a distance measuring apparatus using such an ultrasonic wave, there is an ultrasonic distance measuring apparatus that transmits and receives an ultrasonic pulse between a parent device and a child device and measures a distance from a time required for transmission and reception. It is known that this ultrasonic distance measuring device can measure a distance relatively easily because its transmission speed is lower than that of a distance measuring device using light or radio waves.

One method of such an ultrasonic distance measuring device will be described with reference to FIGS. 5 and 6. FIG. Ultrasonic distance measuring device of FIG. 5 than those used to measure the distance to the vehicle A _1, A _2, both the vehicle A _1, A ₂ is provided with ultrasonic sensors 1. In the following description for convenience ultrasonic sensor 1 of the vehicle A ₁ and the master unit, called the ultrasonic sensor 2 of the vehicle A ₂ and slave unit. Further, transmission and reception between the parent device 1 and the child device 2 are performed using ultrasonic waves composed of pulse trains. Ultrasonic including a pulse train P ₁ shown in FIG. 6 (a) to be transmitted from the parent device 1, a reception R ₁ with a delay of time t ₁ as it propagates through the air shown in FIG. (B) The child device 2 receives it. Slave unit 2 transmits the ultrasonic waves after waiting for the time t _d after receiving a pulse train P ₂ as shown in FIG. (C), the time as shown in FIG. (D) t ₂
Only later is received in the parent device 1 as reception R _2. Since the transmission waiting time t _d of the slave 2 is given to the master 1 in advance,
The distance d between the parent device 1 and the child device 2 is obtained by d = (t−t _d ) ÷ 2 × c or d = (t ₁ + t ₂ ) ÷ 2 × c (where c is the sound speed). (Japanese Patent Application No. 62-260034).

[Problems to be solved by the invention]

However, since the reception level of ultrasonic waves generally decreases as the distance increases, if the gain is increased to measure a long distance, the reception level is too high at short distances and the effect of multiple reflections of the ultrasonic signal appears. It may cause malfunction. Conversely, if the gain is adjusted to an appropriate value at a short distance, the reception level becomes small at a long distance, and there is a problem that measurement cannot be performed.

The present invention has been made in view of the above points, and an object of the present invention is to provide an ultrasonic distance measuring device capable of reliably measuring a distance regardless of a distance between ultrasonic sensors. It is in.

[Means for solving the problem]

The present invention transmits an ultrasonic wave composed of a pulse train from a parent device, receives the ultrasonic wave by a child device, and after a lapse of a preset transmission wait time, forms a pulse sequence from the child device to the parent device. The ultrasonic wave is returned, and the time required for the ultrasonic wave returned from the child device to be received by the parent device from the transmission time point of the ultrasonic wave from the parent device is between the parent device and the child device. In the ultrasonic distance measuring apparatus for measuring the distance, the master unit and the slave unit each include a gain control circuit for controlling the gain of its own receiving circuit, and the gain control circuit on the master unit side measures the measured value. The gain of the own receiving circuit is determined according to the distance, and the gain information is transmitted to the slave unit. The gain control circuit on the slave unit uses the gain information transmitted from the master unit to determine the gain of the own receiving circuit. The feature is to control the gain of Is shall.

[Action]

In the ultrasonic distance measuring device of the present invention, in the parent device,
The gain of its own receiving circuit is adjusted according to the measured distance between the ultrasonic sensors. That is, if the distance is long, the gain of the receiving circuit is increased by the gain control circuit, and if the distance is short, the gain of the receiving circuit is adjusted to be small. Then, the pulse-modulated ultrasonic wave including this gain information is transmitted to the slave unit. The slave unit receives the ultrasonic wave and performs pulse demodulation to obtain the gain information. By using the gain information, the gain control circuit of the slave unit controls its own reception circuit in the same manner as the master unit. Is to adjust the gain.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described.

FIG. 1 is a block diagram showing a practical example of an ultrasonic distance measuring device according to the present invention. Ultrasonic distance measuring device of this embodiment, which was used to measure the distance to the vehicle A _1, A _2, both the vehicle A _1, A ₂ is provided with ultrasonic sensors 1. In the following description for convenience ultrasonic sensor 1 of the vehicle A ₁ and the master unit, called the ultrasonic sensor 2 of the vehicle A ₂ and slave unit. The transmission and reception between the parent device 1 and the child device 2 are performed using ultrasonic waves composed of pulse trains.

In the parent device 1, reference numeral 3a denotes a modulation circuit, which is a receiving circuit 8a to be described later.
The transmission pulse train of the ultrasonic wave including the gain information is determined based on the gain information corresponding to the distance between the ultrasonic sensors 1 and 2 transmitted from the ultrasonic sensor. FIG. 3 is an example of a transmission pulse train. The time interval between two pulse trains P ₁₁ and P ₁₂ (tone burst waves of ultrasonic waves) is made variable. For example, when three types of gain information to be sent to the slave unit 2 can be set, the time interval between the two pulse trains P ₁₁ and P _{12 is represented by} the time interval D ₁ in FIG. interval
D ₂ , a time interval D ₃ in FIG. 9C, may be selected, and three types of gains may be associated with each of these time intervals D ₁ , D ₂ , and D ₃ . FIG. 4 shows another example of a pulse train. In this case, information is sent at predetermined time intervals depending on the presence or absence of the pulse trains P ₁₁ , P ₁₂ , and P ₁₃ . Different gains can be set.

A transmission circuit 4a generates an ultrasonic signal composed of the pulse train determined by the modulation circuit 3a.

Reference numeral 5a denotes a wave transmission drive circuit which amplifies the ultrasonic signal obtained by the transmission circuit 4a so that the ultrasonic wave transducer 6a can be sufficiently driven. In this embodiment, the ultrasonic vibrator 6a and the ultrasonic vibrator 6b are of the integrated transmission / reception type. However, even if two ultrasonic vibrators dedicated to transmission and reception are used, there is no problem. Absent.

Reference numeral 7a denotes a gain control circuit, which receives a return signal from the handset 2 received by the ultrasonic transducer 6a as a received signal,
In addition to transmitting the control signal to the receiving circuit 8a, the control signal corresponding to the distance measured by the receiving circuit 8a is transmitted to the receiving circuit 8a. That is, when the measured distance is large, a control signal for increasing the gain is generated, and when the distance is small, a control signal for decreasing the gain is generated. The signal of the measured distance is fed back from the receiving circuit 8a.

8a is a receiving circuit, a reception signal from the gain control circuit 7 amplifies the indicated gain by a gain control signal, (delay time from transmitting) preset transmit latency t _d and transmitting The distance between the parent device 1 and the child device 2 is obtained from the calculation formula described above (described in the section of the prior art) using the time t from the reception to the reception of a wave, and the like, and a display (not shown) This is a circuit that outputs a signal for outputting a distance to the modulation circuit 3a and the gain control circuit 7a, and for providing gain information corresponding to the determined distance. When the power is turned on, since the distance is not determined, the gain may be set to, for example, the maximum level.

In the slave unit 2, 7b is a gain control circuit, which is an ultrasonic vibrator.
A received signal, which has received the ultrasonic signal from the parent device 1 received at 6b, is sent to a receiving circuit 8b described later, and a transmission pulse train of the ultrasonic wave corresponding to the distance transmitted from the parent device 1 is transmitted. The demodulation circuit 9b reads the gain information from the pattern, determines the gain of the reception circuit 8b described below, and sends a gain control signal to the reception circuit 8b. A receiving circuit 8b amplifies the received signal from the gain control circuit 7b according to the gain information, sends a trigger signal to the transmitting circuit 4b, and sends a transmitted pulse train pattern corresponding to the gain information to the demodulation circuit 9b. The gain at the time of turning on the power is set to the maximum level, similarly to the receiving circuit 8a on the base unit 1. 4b is a transmission circuit, after receiving a trigger signal of the receiving circuit 8b, the pre-stored after transmitting latency t _d, the return signal is sent to the transmitting drive circuit 5b. Reference numeral 5b denotes a wave transmission drive circuit, which amplifies the return signal obtained by the transmission circuit 4b so that the ultrasonic transducer 6b can be sufficiently driven.
Reference numeral 9b denotes a demodulation circuit for demodulating a signal modulated by the modulation circuit 3a of the master unit 1 and transmitting gain information corresponding to the measured distance to the gain control circuit 7.

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

FIG. 2 is a timing chart for explaining the operation of the ultrasonic distance measuring device of the present invention. In parent device 1,
Transmission circuit 4a ultrasonic pulse train from the pulse train pattern set by the modulation circuit 3a, for example, a pulse train P ₁₁ of the pattern such as Figure 3 (c), to produce the P _12, transmitting the driving circuit
The signal is amplified at 5a and transmitted from the ultrasonic transducer 6a.

The parent device 1 is shown in FIG.
P _11, and sends the P _12, reception gate G after waiting only time t _d
open. The time D ₃ of the pulse train pattern in FIG.
Since the distance is not determined at first, it is assumed that the gain corresponds to the maximum gain V (that is, the longest time interval among the three types of time intervals). The gain of the receiving circuit 8a is initially set by the gain control circuit 7a so as to have the gain V.

The slave unit 2 converts the transmission pulse trains P ₁₁ and P ₁₂ transmitted from the master unit 1 into ultrasonic pulse trains R ₁₁ and R _{12 as shown in FIG.}
As received. At this time, the received ultrasonic pulse train R
_11, R ₁₂ is a gain control circuit 7b, via the receiving circuit 8b, is input to the demodulation circuit 9b, is demodulated. As a result, the pulse train
Get information gain V corresponding with P _11, time D ₃ is the distance information between the P _12, and sends to the gain control circuit 7b. Gain control circuit
At 7b, a control signal for setting the gain of the receiving circuit 8b to V is sent to the receiving circuit 8b. When the power is turned on, the demodulation circuit
Since there is no gain information from 9b, a control signal for setting the maximum level gain V has already been sent to the receiving circuit 8b. Further, it transmits the received signal to the receiving circuit 8b. The receiving circuit 8b sends the received signal to the demodulation circuit 9b,
The trigger signal is transmitted to the transmission circuit 4b. In the transmission circuit 4b,
Reply pulse train P ₁₁ trigger signal from the input from the reception circuit 8b after transmitting the waiting time t _d ', P _12' transmits ultrasound signals to transmit drive circuit 5b, amplified in transmitting drive circuit 5b Then, a reply is sent from the ultrasonic transducer 6b to the parent device 1. The ultrasonic pulse trains P ₁₁ ′ and P ₁₂ ′ for reply may be exactly the same as the pulse train transmitted from the parent device 1, but are not limited thereto.

Parent device 1 receives a response signal from the slave unit 2, but for received signals in the reception gate G to be held after transmitting a transmission pulse train P _11, P ₁₂ after a time t _d, the following operations I do.

In the gain control circuit 7a, reception pulse train R ₁₁ is within the reception gate G ', and detects the R _12, the receiving circuit 8a, than the time delay t from transmission pulse master unit 1, the parent device 1 and the child The distance between the containers 2 is obtained. Now, assuming that the distance obtained here is a small value, in order to change the gain of the receiving circuit 8a to a small value V ', a pulse pattern train corresponding to the gain V' is transmitted to the transmitting circuit 4a.
To the gain control circuit 7a.
Send to The gain control circuit 7a sends a control signal for setting the gain of the receiving circuit 8a to V 'according to the information of the gain V' to the receiving circuit 8a. In the transmission circuit 4a, as shown in FIG. 3 (a), generates a pulse train P _21, P ₂₂ of the pattern of the time interval D _1, is amplified by transmit circuit 5a, to transmit the ultrasonic transducer 6a .

 Hereinafter, the above operation is repeated.

According to the present embodiment, the gain of each of the receiving circuits 8a and 8b of the master unit 1 and the slave unit 2 is determined by the distance between the master unit 1 and the slave unit 1. If the distance is short, the mutual multiplexing of the ultrasonic waves is performed. Since it is susceptible to multiple reflections, reduce the gain, reduce the effects of multiple multiple reflections, and conversely, increase the gain if the distance is long,
A minute ultrasonic pulse from a long distance can be reliably received.

〔The invention's effect〕

As described above, according to the present invention, an ultrasonic wave composed of a pulse train is transmitted from a parent device, the ultrasonic wave is received by a child device, and after a predetermined transmission wait time has elapsed, the child device From the ultrasound returned from the pulse train to the parent device,
From the transmission time of the ultrasonic wave from the parent device, the time required for the ultrasonic wave returned from the child device to be received by the parent device, the distance between the parent device and the child device is measured. In the acoustic distance measuring device, each of the master unit and the slave unit has a gain control circuit for controlling the gain of its own receiving circuit, and the gain control circuit of the master unit has its own gain control circuit according to the measured distance. Along with determining the gain of the receiving circuit, the gain information is transmitted to the slave, and the gain control circuit on the slave side controls the gain of its own receiving circuit based on the gain information transmitted from the master. Therefore, an ultrasonic distance measuring device capable of reliably measuring the distance regardless of the distance between the ultrasonic sensors can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a time chart for explaining the operation of the above, FIG. 3 and FIG. FIG. 5 is a schematic diagram showing a conventional example, and FIG. 6 is a time chart for explaining the operation of the above example. 1... Master unit 2... Slave unit 3a... Modulation circuits 4a and 4b. 5a, 5b: Wave transmission drive circuit 6a, 6b: Ultrasonic vibrator 7a, 7b: Gain control circuit 8a, 8b: Receiving circuit 9b: Demodulation circuit

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-62-224333 (JP, A) JP-A-3-102282 (JP, A) JP-A-1-2211691 (JP, A) JP-A-1- 221692 (JP, A) JP-B 63-3268 (JP, B2) Jiko-62-17737 (JP, Y2)

Claims (1)

(57) [Claims] An ultrasonic wave composed of a pulse train is transmitted from a master unit, and after the ultrasonic wave is received by a slave unit and a predetermined transmission wait time has elapsed, the slave unit transmits the ultrasonic wave from the pulse train to the master unit. The ultrasonic wave returned from the time of transmission of the ultrasonic wave from the parent device, by the time required until the parent device receives the ultrasonic wave returned from the child device, between the parent device and the child device In the ultrasonic distance measuring device for measuring a distance between the master unit and the slave unit, each of the master unit and the slave unit is provided with a gain control circuit for controlling a gain of its own receiving circuit. The gain of its own receiving circuit is determined according to the distance, and the gain information is transmitted to the slave unit. The gain control circuit on the slave unit side receives the gain information transmitted from the master unit, The feature is to control the gain of the circuit. Ultrasonic distance measuring device for.