JP2870545B2 - 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 ultrasonic waves composed of a pulse train between a parent device and a child device to measure a distance. is there.

[Prior Art] As this type of distance measuring apparatus using ultrasonic waves, there is an apparatus which transmits and receives ultrasonic pulses between a parent device and a child device and measures the distance from the time required for transmitting and receiving waves. 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. Figure 3 of the ultrasonic distance measuring device, which was used to measure the inter-vehicle distance of the vehicle A _1, A _2, both the vehicle A _1, A ₂ is provided with ultrasonic sensors 1 and 2. In the following description, for convenience the ultrasonic sensor 1 of the vehicle A ₁ is referred to as master unit, the ultrasonic sensor 2 of the vehicle A ₂ is referred to as a slave unit. The transmission and reception between the parent device 1 and the child device 2 is performed using ultrasonic waves composed of pulse trains. An ultrasonic wave P ₁ composed of a pulse train shown in FIG.
Is reception to the slave unit 2 with a delay of time t ₁ as it propagates through the air shown in FIG. (B) (R _1). Slave unit 2, and transmitting ultrasonic wave P ₂ that waiting for the time t ₀ after reception a pulse train as shown in FIG. (C), the time as shown in (d) of FIG.
The signal is received by master device 1 with a delay of t ₂ (R ₂ ). Since the transmission wait time t ₀ of the slave 2 is given to the master 1 in advance, the distance d between the master 1 and the slave 2 is: d = (tt ₀ ) ÷ 2 × c or d = (T ₁ + t ₂ ) ÷ 2 × c. Here, c indicates the speed of sound. Incidentally, the method of obtaining the distance d is disclosed in Japanese Patent Application Laid-Open No. 1-101487 (Japanese Patent Application No. 62-260).
No. 034).

[Problems to be Solved by the Invention] When determining the distance between the vehicle A ₁ and the vehicle A ₂ as in the third diagram, not thinking just only such as vehicle A ₂ vehicle A _1, both vehicles A _1, A2 In _both cases, you often want to know the distance between vehicles. However, when the above method is used, the distance between the parent device 1 and the child device 2 can be obtained by the parent device 1, but the distance cannot be obtained by the child device 2.

The present invention has been provided in view of the above points,
It is an object of the present invention to provide an ultrasonic distance measuring device capable of obtaining a distance in both a parent device and a child device.

[Means for Solving the Problems] The present invention is based on the assumption that the master unit knows the transmission wait time of the slave unit until the slave unit receives the ultrasonic wave from the master unit and returns the ultrasonic wave to the master unit. The slave sets the transmission wait time of the master unit until the master unit receives the ultrasonic wave from the slave unit and returns the ultrasonic wave to the slave unit, and transmits the ultrasonic wave and then receives the wave. Measurement means for measuring the distance between the two from the time until is provided in the parent device and the child device, respectively, and the reception waiting time from the transmission to the start of reception is the same in the parent device and the child device, The parent device and the child device have the same configuration. The operation of the slave unit is slightly different from that of the master unit in that the slave unit receives an ultrasonic wave from the master unit and returns an ultrasonic wave, but the configuration is substantially the same. In this sense, the configurations of the parent device and the child device are the same.

[Operation] With the configuration described above, the master unit and the slave unit each have a known transmission waiting time, and the measuring unit measures the distance between the two from the time from transmission of the ultrasonic wave to reception of the ultrasonic wave. ing.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. According to the present invention, an ultrasonic wave composed of a pulse train is transmitted from a parent device to a parent device, and the ultrasonic wave is received by a child device, and after a predetermined time elapses, an ultrasonic wave composed of a pulse sequence is transmitted from the child device to the parent device. A sound wave is returned, and the distance between the parent device and the child device is measured by the time required from when the ultrasonic wave is transmitted from the parent device to when the parent device receives the ultrasonic wave returned from the child device. That's what we do. In the ultrasonic distance measuring apparatus according to the present invention, a master unit 1 that actively transmits an ultrasonic pulse by itself and a pulse returned to the master unit 1 by a received pulse signal from the master unit 1 are generated. The distance can be measured for the first time by using it as a parent-child system with the handset 2 that transmits waves. In the present invention, the timing at which the base unit 1 transmits waves is based on the principle that the reception pulse signal from the slave unit 2 is used as the next transmission timing, and if there is no reception, transmission is performed at a fixed time interval. Instead, for example, a random time interval may be used.

Hereinafter, the configuration will be specifically described in detail. In FIG. 1, first, the parent device 1 will be described. The transmission circuit 4 is a circuit that generates an ultrasonic pulse signal as a tone burst wave having a preset duration. The transmission drive circuit 5 is a circuit that amplifies the ultrasonic pulse signal obtained by the transmission circuit 4 so that the ultrasonic vibrator 6 can be sufficiently driven. In this embodiment,
Although the ultrasonic vibrator 6 is of an integrated transmission / reception type, two ultrasonic vibrators dedicated to transmission and reception may be used. The reception gate circuit 7 is a circuit that sets a time at which the reception of a reception signal starts and ends after the transmission of the ultrasonic pulse. The receiving circuit 8 amplifies the received ultrasonic pulse, and the distance calculation unit 81 inside the receiving circuit 8 calculates the distance between the parent device 1 and the child device 2. Measuring means for measuring the distance of the object.
In addition, the transmission timing setting circuit 3 is a circuit that determines that the next transmission timing is to be received in response to the reception of the ultrasonic pulse from the reception circuit 8.

Next, the operation will be described. FIG. 2 shows an operation timing chart of the embodiment of the present invention. As shown in FIG. 2 (a), the transmission circuit 4 of the base unit 1 includes a transmission timing setting circuit 3
Receiving more transmission timing signal, for transmitting ultrasonic waves P ₁ including a pulse train. However, for example, when the distance is too long to transmit and receive signals to and from the slave unit 2, no timing signal is sent from the transmission timing setting circuit 3, so the transmission circuit 4 sets its own preset transmission time. to transmit ultrasonic pulses P ₁ at intervals.

Next, master unit 1 waits for time tr (wave reception waiting time) from the transmission start time to start receiving wave circuit 7 so as to start receiving.
To provide a receiving gate. The reason for waiting for this time tr is that when the parent device 1 and the child device 2 are close to each other, the transmission time setting circuit 3 frequently outputs a timing signal because the time delay of the propagation of the ultrasonic wave is small. As a result, the transmission time interval is shortened, so that it becomes more susceptible to multiple reflections. The value of the time tr is determined optimally according to the place where the ultrasonic distance measuring device is installed and the surrounding environment.

The transmitted ultrasonic pulse propagates in the air and is received by the slave 2 as R _{1 with a} delay of time t _{1 as} shown in FIG. 2 (b). Slave unit 2 is transmitting ultrasonic waves P ₂ of a pulse train as shown waiting after reception of R ₁ by a time ts' (transmit latency) in FIG. (B), shown in the diagram (a) As time t ₂
After a delay, the signal is received by the receiver 1 as R _{2 by the} receiver 1.
Since the transmission waiting time ts' of the slave 2 is known to the master 1, the distance d between the master 1 and the slave 2 is represented by the following equation:
The distance is calculated by the distance calculation unit 81.

d = (t−ts ′) ÷ 2 × c where t is the time from the start of the ultrasonic wave to the reception of the returned ultrasonic wave, and c is the speed of sound. When the relative distance between the parent device 1 and the child device 2 does not change, t ₁ = t _2. However, when the relative distance changes, the average distance is (t ₁ + t ₂ ) / 2.

Then, starting from the transmitting P ₂ of the slave unit 2, slave unit 2 is provided with a reception gate to start the reception waiting from transmitting start time by time tr '(reception wait time). The transmitted ultrasonic pulse propagates in the air and is received by the master 1 as R _{2 with a} delay of time t _{2 as} shown in FIG. 2A. Parent device 1
After receiving R _2, after waiting for a time ts (transmission waiting time), an ultrasonic wave P ₃ composed of a pulse train is transmitted as shown in FIG. 11A, and only for a time t _{3 as} shown in FIG. Late to child unit 2
It is reception as R _3. Transmitting wait time of master unit 1 for slave unit 2
Since ts is known, the distance d between the parent device 1 and the child device 2 is expressed by the following equation.

d = (t′-ts) ÷ 2 × c where c is the speed of sound. When the relative distance between the parent device 1 and the child device 2 does not change, t ₂ = t _3. However, when the relative distance changes, the average distance is (t ₂ + t ₃ ) / 2.

As described above, the slave unit 2 knows the reception waiting time from the transmission of the base unit 1 to the start of reception, and the reception waiting time from the transmission of the slave unit 2 to the start of reception. Since the time is known by the master 1, the distance can be obtained by both the master 1 and the slave 2.

Even if the reception wait time and the transmission wait time are the same in both the master unit 1 and the slave unit 2, there is no hindrance to the above-mentioned operation. The device 2 can be realized by a device having the same configuration. This is because, for example, if the times ts and ts' take different values, the circuit will change, or the program or data will change. Disappears.

[Effects of the Invention] As described above, the present invention is based on the assumption that the master unit knows the transmission waiting time of the slave unit until the slave unit receives the ultrasonic wave from the master unit and returns the ultrasonic wave to the master unit. The slave sets the transmission wait time of the master unit until the master unit receives the ultrasonic wave from the slave unit and returns the ultrasonic wave to the slave unit, and transmits the ultrasonic wave and then receives the wave. Measurement means for measuring the distance between the two units are provided in the master unit and the slave unit, respectively, and the reception wait time from the transmission to the start of reception is the same for the master unit and the slave unit. Since the transmission wait time from the start of the wave transmission to the start of the next transmission is the same for the parent device and the child device, and the configurations of the parent device and the child device are the same, the parent device and the child device Each have known transmission latency,
The measuring means measures the distance between the two from the time from transmitting the ultrasonic wave to receiving the ultrasonic wave, so that the distance can be measured by both the parent device and the child device. It is possible to make the reception wait time from transmission to the start of reception the same for the master unit and the slave unit, and to set the transmission wait time from reception to the start of the next transmission to the parent unit. Since the configuration of the parent device and that of the child device are the same and the configuration of the parent device and that of the child device are the same, it is not necessary to make a dedicated device for each of the parent device and the child device.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a timing chart of the above example, FIG. 3 is an explanatory diagram of a conventional example, and FIG. 4 is a timing chart of the above example. 1 is a parent device and 2 is a child device.

Claims (1)

(57) [Claims] An ultrasonic wave composed of a pulse train is transmitted from a master unit, the ultrasonic wave is received by a slave unit, and after 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 parent device, the distance between the parent device and the child device by the time required for the parent device to receive the ultrasonic wave returned from the child device from the transmission time of the ultrasonic wave from the parent device In the ultrasonic distance measuring device to be measured, the parent device assumes that the transmission wait time of the child device until the child device receives the ultrasonic wave from the parent device and returns the ultrasonic wave to the parent device is known by the parent device, When the slave unit receives the ultrasonic wave from the slave unit and returns the ultrasonic wave to the slave unit, the slave unit assumes that the transmission wait time is known, and the time from transmitting the ultrasonic wave to receiving it Measurement means for measuring the distance between the two are provided in the parent device and the child device, respectively, and the reception wait time from the transmission to the start of reception is measured by the parent device. And that the slave unit and the slave unit have the same configuration, and that the transmission wait time from the reception of a wave to the start of the next transmission is the same for the master unit and the slave unit, and that the configuration of the master unit and the slave unit is the same. Ultrasonic distance measuring device.