JP2000088960A - Transmitter / receiver separate reflection type ultrasonic distance measuring device - Google Patents

Abstract

(57) [Problem] To provide an ultrasonic distance measuring apparatus of a transmission / reception separation type reflection type capable of increasing the measuring distance with high reliability, having a simple circuit configuration, and improving the measuring accuracy. SOLUTION: CPU main body 16 in ultrasonic transmitter 1
Reference numeral 2 indicates the start of clocking with the frequency division pulse from the frequency division circuit 166 at the same time as the start of oscillation of the transmission ultrasonic sensor. The ultrasonic wave radiated from the ultrasonic sensor 3 is reflected by the object whose distance is to be measured, and is detected by the ultrasonic sensor 13 for reception. The ranging sensitivity correction circuit 114 corrects the sensitivity of the signal from the ultrasonic sensor 13 based on the sensitivity correction data. The detection circuit 130 includes an A / DC 132, and performs envelope detection on the signal whose sensitivity has been corrected. The CPU main body 162 performs signal processing on the detection signal, detects the reception of an accurate reflected wave, and stops the timing.
The CPU main body 162 further calculates the distance between the measurement target object 7 and the ultrasonic sensor 3 based on the measured time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission / reception separation type ultrasonic distance measuring apparatus for measuring a distance using an ultrasonic sensor. More specifically, the present invention relates to a technology that enables a long distance to be measured with a simple circuit configuration in a transmission / reception separated-type reflection-type ultrasonic distance measuring apparatus that performs distance measurement using two ultrasonic sensors.

[0002]

2. Description of the Related Art A distance measuring method using an ultrasonic sensor is known. As a distance measurement method using such an ultrasonic sensor, a monocular distance measurement device using one ultrasonic sensor for both transmission and reception, and a transmission ultrasonic sensor and a reception ultrasonic sensor are used independently. It can be roughly classified into a transmission / reception separated type ultrasonic distance measuring device.

[0003] The monocular distance measuring device has an advantage that the price of the ultrasonic sensor is reduced because only one ultrasonic sensor is used. However, since the ultrasonic sensor is used for both transmission and reception, it is necessary to switch circuits between transmission timing and reception timing, and it may be difficult to measure a short distance.

The transmission / reception separated type ultrasonic distance measuring apparatus is a binocular ultrasonic distance measuring apparatus in which a transmitting ultrasonic sensor and a receiving ultrasonic sensor are independently provided. Overcome the problems of distance measuring devices. The present invention relates to a transmission / reception separated type ultrasonic distance measuring apparatus. FIG. 1 is a configuration diagram of a transmission / reception separated type ultrasonic distance measuring apparatus. The transmission / reception separation type ultrasonic distance measuring apparatus includes an ultrasonic transmitter 1, an ultrasonic sensor 3 for transmission.
And a transmitting side having a transmitting horn antenna 5 and a receiving side having an ultrasonic receiver 11, a receiving ultrasonic sensor 13 and a receiving horn antenna 15.
The transmission / reception-type reflection type ultrasonic distance measuring apparatus is mounted on a certain device, for example, a vehicle, on the transmitting side and the receiving side, and is used to measure the distance from the vehicle to the distance measuring object 7.

[0005] The central axis of the transmitting ultrasonic sensor 3 (or the central axis of the directivity of the transmitting horn antenna 5) and the central axis of the receiving ultrasonic sensor 13 (or the receiving horn antenna 1).
It is preferable that the angle? This is because, when the angle θ increases, it becomes difficult to receive the ultrasonic waves emitted from the transmitting ultrasonic sensor 3 and reflected by the distance measurement target object 7. The transmission horn antenna 5 and the reception horn antenna 15 are used to minimize noise around the distance measurement environment. Further, the reflected ultrasonic waves are focused using the receiving horn antenna 15. From the viewpoint of minimizing the influence of the vibration of the transmitting ultrasonic sensor 3, it is desirable that the mounting substrate of the transmitting ultrasonic sensor 3 and the mounting substrate of the receiving ultrasonic sensor 13 be separated.

As the transmitting ultrasonic sensor 3, a piezoelectric ceramic ultrasonic sensor, for example, a piezoelectric sensor such as lithium niobate can be used. In this case, the excitation voltage of the transmitting ultrasonic sensor 3 is, for example, 4
It is about 100 V (rms) at 0 KHz. Similarly to the transmission ultrasonic sensor 3, the reception ultrasonic sensor 13 can use a piezoelectric ceramic ultrasonic sensor, for example, a piezoelectric sensor such as lithium niobate.

A distance measuring method in the transmission / reception separated type ultrasonic distance measuring apparatus illustrated in FIG. 1 will be described. The ultrasonic transmitter 1 excites the transmission ultrasonic sensor 3 to generate an ultrasonic wave from the transmission ultrasonic sensor 3. Ultrasonic waves from the transmission ultrasonic sensor 3 are directed toward the distance measurement target object 7 via the transmission horn antenna 5 and strike the distance measurement target object 7. The ultrasonic wave reflected by the distance measurement target object 7 is incident on the receiving ultrasonic sensor 13 via the receiving horn antenna 15, and the receiving ultrasonic sensor 13 outputs an electric signal according to the level of the incident ultrasonic wave. I do. The ultrasonic receiver 11 measures the time from when the transmission ultrasonic sensor 3 radiates ultrasonic waves to when it is received by the reception ultrasonic sensor 13, and from this measurement time, the distance measurement target object 7 and the transmission ultrasonic sensor 3 is calculated. The distance Lx to be measured can be calculated based on the following equation.

Lx = (V × S) / 2 (1) where V is the propagation speed of the ultrasonic wave in the air at the temperature t. V = 331.5 + 0.6t (m / sec) S is the time from the start of oscillation of the transmitting ultrasonic sensor 3 to the time when the receiving ultrasonic sensor 13 receives the first reflected wave.

The temperature at the time of this measurement is measured with respect to a reference temperature, for example, the propagation speed of the ultrasonic wave at t = 20 ° C. The propagation velocity V of the ultrasonic wave at t = 20 ° C. is 3
32.7 (m / sec).

In the ultrasonic distance measuring apparatus of the transmission / reception separated type reflection type illustrated in FIG. 1, when the transmitting ultrasonic sensor 3 and the receiving ultrasonic sensor 13 are used in a vehicle or the like, they can withstand wind and rain outdoors. Therefore, a drip-proof ultrasonic sensor is often used. The drip-proof type ultrasonic sensor is provided with a cover, so that the overall gain is reduced.
Therefore, when a drip-proof ultrasonic sensor is used for the transmission ultrasonic sensor 3 and the reception ultrasonic sensor 13, the distance measurement range becomes short. For example, when performing distance measurement (ranging) stably using a drip-proof type ultrasonic sensor, usually 4 to
It can be applied only to distance measurement of about 5m. However, when using a transmission / reception separation type ultrasonic distance measuring device as a vehicle approach sensor, a longer distance measurement is also required, and a transmission / reception separation type reflection type reflection type using a drip-proof ultrasonic sensor is required. There has been a demand for an improved ultrasonic distance measuring device.

As a method for overcoming the above-mentioned problems, the present inventor has disclosed, for example, Japanese Patent Application No. 10-104812, filed on April 15, 1998, entitled "Transmission / reception separated type ultrasonic distance measuring apparatus and its method". And proposed a method and apparatus for performing sensitivity correction according to the type of the distance measurement target object and the distance to be measured.

An ultrasonic receiver 11 which also performs such sensitivity correction will be described. FIG. 2 is a diagram mainly illustrating the circuit configuration of the ultrasonic receiver 11 in the transmission / reception separated type ultrasonic distance measuring apparatus. The ultrasonic receiver 11
It has a preamplifier / buffer circuit 110, a high-frequency signal filtering circuit 112, a ranging sensitivity correction circuit 114, a low-frequency signal filtering circuit / buffer circuit 116, a detection circuit 118, a buffer circuit / comparison circuit 120, and a distance measurement operation control circuit 122. .

The operation of each circuit of the ultrasonic receiver 11 will be described. The pre-amplifier / buffer circuit 110 has an amplifying circuit, and amplifies a weak electric signal from the receiving ultrasonic sensor 13 to a predetermined level at which signal processing can be performed by a subsequent-stage circuit. The high-frequency signal filtering circuit 112 includes a preamplifier circuit
Among the signals corresponding to the reflected ultrasonic waves amplified by the buffer circuit 110, high-frequency components are passed and low-frequency components are removed. Thereby, low-frequency noise included in the reflected ultrasonic waves from the distance measurement target object 7 can be removed. The ranging sensitivity correction circuit 114 has a variable gain amplifier circuit, and corrects the sensitivity of the signal from the high frequency signal filtering circuit 112. This will be described in detail below. Low frequency signal filtering circuit / buffer circuit 11
6 is such that it can be detected by a detection circuit 118 at the subsequent stage.
The low frequency signal component of the output signal from the ranging sensitivity correction circuit 114 is passed. The detection circuit 118 detects an output signal from the low-frequency signal filtering circuit / buffer circuit 116. As the detection in the detection circuit 118, for example,
Performs envelope detection. Here, double detection is performed. The buffer circuit / comparison circuit 120 sequentially stores the continuous signal detected by the detection circuit 118 as digital data, and compares the continuous signal with a predetermined level signal, and when the received reflected wave is higher than a predetermined level, a desired reflected wave is generated. It outputs a signal indicating that it has been received. The distance measurement calculation control circuit 122 receives the ultrasonic oscillation from the transmission ultrasonic sensor 3
The time until the reception wave is received by the comparison circuit 120 is measured, and the distance is calculated according to Equation 1.

Prior to the above-mentioned actual measurement, the distance measurement sensitivity correction circuit 11
In step 4, the ultrasonic sensor sensitivity correction data for sensitivity correction is generated, and the sensitivity of the received ultrasonic signal is corrected in the ranging sensitivity correction circuit 114 based on the ultrasonic sensor sensitivity correction data. Therefore, the ultrasonic sensor sensitivity correction data used in the distance measurement sensitivity correction circuit 114 is collected in advance. Hereinafter, the method will be described. The transmission ultrasonic sensor 3 is driven, and the distance measurement calculation control circuit 122 measures a temporary distance from the reception signal of the reception ultrasonic sensor 13 in a state where the sensitivity correction in the distance measurement sensitivity correction circuit 114 is not performed. The distance measurement calculation control circuit 122 generates the obtained temporary distance and the ultrasonic sensor sensitivity correction data to be performed by the distance measurement sensitivity correction circuit 114, and sets the data in the distance measurement sensitivity correction circuit 114.

Thereafter, the transmission ultrasonic sensor 3 is driven again. The signal received by the receiving ultrasonic sensor 13 is subjected to sensitivity correction in the ranging sensitivity correction circuit 114. The reception signal whose sensitivity has been corrected is detected by a detection circuit 118, and the detection signal is transmitted to a distance measurement operation control circuit 122 via a buffer circuit / comparison circuit 120, and is transmitted by the distance measurement operation control circuit 122. The actual distance is calculated from the time from the transmission of the ultrasonic wave from the acoustic wave sensor 3 to the reception of the reflected wave by the ultrasonic sensor for reception 13 according to the equation (1).

FIG. 3A is a circuit diagram showing an example of the distance measurement operation control circuit 122 in the transmission / reception separated type ultrasonic distance measurement apparatus. Distance measurement calculation control circuit 12
2 performs an operation control unit (C
PU) 1220 and this arithmetic and control unit (CPU) 1
Crystal oscillator circuit 1221 as clock oscillator 220
, A timing pulse generation circuit 1223, a NAND gate 1225, a reset pulse generation circuit 1227, a latch pulse generation circuit 1229, and a distance measurement pulse generation circuit 1231.

The operation of the distance measurement calculation control circuit 122 will be described. 4A to 4G show the distance measurement calculation control circuit 122.
FIG. 6 is a signal waveform diagram for explaining an operation related to FIG. The reset pulse generation circuit 1227 sends a reset pulse Rp (FIG. 4F) to the arithmetic and control unit (CPU) 1220 based on the timing pulse from the timing pulse generation circuit 1223 when the transmission ultrasonic sensor 3 oscillates. Output and reset the counter in the CPU 1220. The reset counter then outputs the carrier (FIG. 4D) output from the ranging pulse generation circuit 1231 to the timing pulse generation circuit 122 by the NAND gate 1225.
The counting of the timing pulse from step 3 and the gated carrier pulse (FIG. 4E), which has been logically operated, is started. When the buffer circuit / comparison circuit 120 determines that the received wave is a proper reflected wave, a timing pulse is output from the timing pulse generation circuit 1223, and the latch pulse generation circuit 1229 outputs the latch pulse Lp (FIG. 4 (g)) to the CPU 1.
Output to 220 to stop counting by the counter. The count value of this counter is the time (FIG. 4A) until the ultrasonic wave is oscillated from the transmitting ultrasonic sensor 3 toward the detection object 7 and the reflected wave is received by the receiving ultrasonic sensor 13. Using this measurement time, distance measurement is performed based on Equation 1. Note that the CPU 1220 performs a correction process in cooperation with the distance measurement sensitivity correction circuit 114 in addition to the above-described distance measurement process. The crystal oscillation circuit 1221 is connected to the clock CL in the CPU 1220.
K signal source.

FIG. 3B is a specific circuit configuration diagram of the detection circuit 118 and the buffer circuit / comparison circuit 120.
The detection circuit 118 has two detection diodes D1 and D2.
2 and a capacitor C1, and detects an input signal as a voltage doubler rectifier circuit, performs envelope detection, and converts the signal into a direct current.
The buffer circuit / comparison circuit 120 includes an operational amplification circuit A functioning as an amplification circuit and a comparison circuit, and RC filters R1 and C2. Buffer circuit 120
Compares the output voltage from the detection circuit 118 with a reference timing signal that determines the timing pulse width and indicates the level of the received wave.

The operation of the buffer circuit / comparison circuit 120 is illustrated in FIGS. 5A is a waveform diagram showing a measurement width, FIG. 5B is a waveform diagram of a timing pulse output from the timing pulse generation circuit 1223, and FIG. 5C is a pulse waveform diagram of a carrier. FIG. 5C is a waveform diagram of a direct wave and a reflected wave of the carrier, FIG. 5D is a detection waveform diagram of the detection circuit 118, and FIG. FIG. 9 is a waveform diagram of a signal indicating a result.

[0020]

FIG. 4B shows an example of the pulse oscillation frequency of the distance measuring pulse generation circuit 1231.
As shown in FIG. 4, when f0 = 17.2 KHz,
The distance over which the ultrasonic wave propagates during the time of one of the distance measurement pulses illustrated in FIG. It is sufficient to increase this frequency to further improve the accuracy of distance measurement. However, the distance measurement pulse generation circuit 1 as a carrier oscillation source is used.
Since the stability of the distance 231 is required, it is necessary to select a high-precision circuit component of the distance measuring pulse generation circuit 1231 and to improve the adjustment accuracy, so that the cost of the distance measurement pulse generation circuit 1231 increases. There is.

The received signal from the receiving ultrasonic sensor 13 has a timing pulse width due to large variations in the diodes D1 and D2 and the capacitor C1 in the detection circuit 118 and the capacitor C2 and the resistance element R1 in the buffer circuit / comparison circuit 120. Is not accurate. As a result, the comparison result in the buffer circuit / comparison circuit 120 may fluctuate in terms of timing, and the timing pulse of the timing pulse generation circuit 1223 may be inaccurate. As a result, diodes D1, D
2. The level fluctuation occurs due to the variation of the capacitor C1 and the like, and the output of the reflected wave comparator illustrated in FIG. 5E fluctuates with time. In theory, an error is added to the distance measured by round trip time conversion, and accurate distance measurement is performed. Sometimes it is difficult.

The frequency range of the ultrasonic wave contains a lot of extraneous noise, and the receiving side receives a signal having a large input level even at a frequency far from the oscillation frequency of the transmitting ultrasonic sensor 3. The error may increase.

In the above description, the case where the ranging sensitivity correction circuit 114 is provided has been described. However, even when the ranging sensitivity correction circuit 114 is not provided, the above-described problem is encountered except that the distance measurement range is shortened. I do. That is, the above-described problem is encountered when the circuit configuration of the distance measurement calculation control circuit 122 shown in FIG.

An object of the present invention is to provide an ultrasonic distance measuring apparatus of a transmission / reception separated type, which enables a more accurate distance measurement by simplifying the circuit configuration regardless of whether or not to perform distance measurement sensitivity correction. To provide.

[0025]

According to the present invention, an ultrasonic wave radiated from a transmitting ultrasonic sensor is reflected by a distance measuring object, and the reflected ultrasonic wave is received by a receiving ultrasonic sensor. A transmission / reception separated reflection method that measures time from transmission of ultrasonic waves to reception of ultrasonic waves, and measures the distance from the ultrasonic sensor for transmission or the ultrasonic sensor for reception to the distance measurement target object from the measurement time. The ultrasonic distance measuring device, wherein the ultrasonic distance measuring device performs a distance measurement by processing a signal from the transmitting ultrasonic sensor for controlling the driving of the transmitting ultrasonic sensor and a signal from the receiving ultrasonic sensor. A receiving device, and control means for controlling the transmitting device and the receiving device, the receiving device comprising: an envelope detection means; an arithmetic processing means; and a clock signal generation circuit of the arithmetic processing means. And the operation A frequency dividing circuit for dividing the frequency of the original oscillation signal from the clock signal generating circuit, a counting means for counting the frequency-divided clock from the frequency dividing circuit, and an envelope detection signal from the envelope detecting means. Receiving signal detecting means for detecting a normal received signal from, and counting means for counting the frequency-divided signal by the counting means, from the oscillation of the ultrasonic wave to the detection of the received signal, in the counting means. From the result, there is provided an ultrasonic distance measuring apparatus of a transmission / reception separated type reflection type having a distance calculating means for calculating a distance.

Preferably, the envelope detection means includes an analog / digital conversion circuit.

Preferably, said arithmetic processing means monitors a frequency component of a signal inputted to said envelope detection means,
When a signal of a predetermined frequency component is applied to the envelope detection means, the envelope detection means is substantially operated.

The transmitting ultrasonic sensor is a drip-proof transmitting ultrasonic sensor, and the receiving ultrasonic sensor is a drip-proof receiving ultrasonic sensor. Preferably, the receiving device is provided with a sensitivity correction circuit for correcting the sensitivity of a reception signal in the ultrasonic sensor for reception at a stage preceding the envelope detection means, and the envelope detection means outputs an output of the sensitivity correction circuit. Detect.

Preferably, using an envelope detection means represented by an analog / digital conversion circuit (A / DC),
The prototype of the received waveform is subjected to envelope detection, and signal processing is performed by arithmetic processing means to perform accurate ranging.

The arithmetic processing means includes a frequency dividing circuit for dividing the frequency of the original oscillation signal from the clock signal generating circuit, a counting means for counting the frequency-divided clock from the frequency dividing circuit, and an envelope detecting means. Receiving signal detecting means for detecting a normal received signal from the envelope detection signal of the above, and counting control in which the counting means counts the frequency-divided signal from the oscillation of the ultrasonic wave to the detection of the received signal in the counting means. And a distance calculating means for calculating a distance from the counted result. The frequency dividing means can be easily constituted by, for example, a D-type flip-flop, and the counting means can be realized by a counter circuit incorporated in the arithmetic processing means. Other signal processing can be performed as a processing function of arithmetic processing means, for example, a microcomputer.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment As a first embodiment of a transmission / reception separated type ultrasonic distance measuring apparatus according to the present invention, an ultrasonic distance measuring apparatus having a configuration illustrated in FIGS. 2 and 3A is used. In the sound wave receiver 11, a case where the distance measurement calculation control circuit 122A has the circuit configuration of FIG. 6 will be described. Note that the basic configuration of the front part of the transmission / reception separated type ultrasonic distance measuring apparatus of the present invention is the configuration illustrated in FIG.

The ultrasonic receiver 11A shown in FIG. 6 includes a preamplifier / buffer circuit 110, a high-frequency signal filtering circuit 112,
It has a distance measurement sensitivity correction circuit 114, a low frequency signal filtering circuit / buffer circuit 116, a detection circuit 130, and a distance measurement calculation control circuit 140. The detection circuit 130 is a circuit corresponding to the detection circuit 118. In the present embodiment, the detection circuit 130 includes an analog / digital conversion circuit (A / DC) 132. The buffer circuit / comparison circuit 120 having the above-mentioned problem has been eliminated. Therefore, FIG.
The circuit illustrated in FIG. The distance measurement calculation control circuit 140 corresponds to the distance measurement calculation control circuit 122, but has a different configuration. Distance measurement calculation control circuit 140
Are a crystal oscillation circuit 150 corresponding to the crystal oscillation circuit 1221 in FIG.
0 corresponding to an arithmetic control unit (CPU) 160. However, unlike the CPU 1220, the CPU 160 includes a CPU main body 162, a frequency determination circuit 164,
The buffer circuit 165, the 1 / N frequency dividing circuit 166,
And an M frequency dividing circuit 167.

The operation of the ultrasonic receiver 11A illustrated in FIG. 6 will be described. The operation of the ultrasonic receiver 11A illustrated in FIG. 6 is basically the same as the operation of the ultrasonic receiver 11 illustrated in FIG. Therefore, the operation of the ultrasonic receiver 11A shown in FIG.
(G) and FIGS. 5 (a) to 5 (e).

The A / DC 132 is a low-frequency signal filtering circuit.
The signal from the buffer circuit 116 is converted into a digital signal at a predetermined sampling frequency. The converted signal in the A / DC 132 is a kind of envelope detection signal. A / DC
The envelope detection signal from 132 is applied to the CPU main body 162, and a received signal determination process described later is performed. In the present embodiment, the signal from the low-frequency signal filtering circuit / buffer circuit 116 is faithfully converted into a digital signal without identifying the received wave by a simple binary comparison as in the buffer circuit / comparing circuit 120. Only. In addition, the A / DC 132 may convert only the absolute value or the signal on the positive electrode side as illustrated in FIG. 5D without converting the positive and negative signals. Then, A / DC
The number of bits of 132 is reduced, and the accuracy is not substantially reduced.

The buffer circuit 165 includes the crystal oscillation circuit 150
The original oscillation signal of frequency f0 from the frequency divider 1 / N
And 1 / M frequency dividing circuit 167. The original frequency f0 of the crystal oscillation circuit 150 is 1 MHz, 4 MHz, or the like. As described above, the crystal oscillation circuit 1 for the CPU 160 is originally a highly stable and high frequency oscillation source.
Since the crystal oscillator 50 exists, if the crystal oscillation circuit 150 is utilized, it is not necessary to provide a high-priced frequency oscillation source.

The 1 / N frequency dividing circuit 166 divides the frequency of the original oscillation signal of frequency f0 by 1 / N to generate a first carrier pulse of frequency f1 (FIG. 4B). 1 / M frequency dividing circuit 1
67 divides the frequency of the original oscillation signal of frequency f0 by 1 / N,
A second carrier pulse having a frequency f1 (FIG. 4D) is generated. As described above, by using the crystal oscillation circuit 150, the 1 / N frequency dividing circuit 166, and the 1 / M frequency dividing circuit 167, the timing pulse generating circuit 1223 in FIG. The 1 / N frequency dividing circuit 166 and 1 / M
For example, in the case of a 1/2 frequency dividing circuit, the frequency dividing circuit 167 can be realized by one D-type flip-flop.
Since a / 4 frequency divider can be realized by two D-type flip-flops, the circuit configuration is very simple. In addition, in the case of such a simple circuit, the circuit is hardly affected by environmental changes such as temperature, and the circuit has high stability.

Further, in the crystal oscillation circuit 150 which oscillates at a high frequency, and in the 1 / N frequency dividing circuit 166 and the 1 / M frequency dividing circuit 167, the original frequency is frequency-divided at any appropriate frequency dividing ratio. The accuracy of time measurement can be improved. Since the setting of the frequency division ratio is easy as described above, in the present embodiment, an appropriate frequency division ratio can be easily set, and high-precision time measurement and, consequently, high distance measurement can be performed. .

The CPU main body 162 performs a predetermined gating process (logical process) on the first carrier pulse from the 1 / N frequency dividing circuit 166 according to the timing, and performs the gating process illustrated in FIG. Generate one carrier pulse. Further, the CPU main body 162 performs predetermined gating processing (logical processing) on the second carrier pulse from the 1 / M frequency dividing circuit 167 according to the timing, and performs the gating second carrier illustrated in FIG. Generate a pulse. CPU main body 162
Are 1 / N frequency dividing circuit 166 and 1 / M frequency dividing circuit 167
Reset pulse Rp based on the carrier pulse from
And a latch pulse Lp, and a counter inside the CPU main body 162 is operated in accordance with these pulses,
The time from the start of oscillation of the transmission ultrasonic sensor 3 to the reception of the reception ultrasonic sensor 13 is measured, and the distance is calculated from the measurement result based on Equation 1. As a result, FIG.
The NAND gate 1225, the reset pulse generation circuit 1227, and the latch pulse generation circuit 1229 of FIG.

The frequency determination circuit 164 determines the clock CLK in the low-frequency signal filtering circuit / buffer circuit 116 and determines whether or not the frequency is within a range of an allowable value.
If the frequency of the clock CLK in the low frequency signal filtering circuit / buffer circuit 116 is within a certain range, it indicates that a normal reflected wave is being received. In other words, in the case of external noise or the like, the frequency of the clock CLK is not normal, and thus the frequency does not fall within the allowable range. Frequency judgment circuit 164
Is the A / DC 13 when a normal received wave is arriving.
2, application of a sampling signal or A / DC 130
The gate of the input signal to the A / DC 130 is removed so that the signal from the low-frequency signal filtering circuit / buffer circuit 116 can be normally detected in the A / DC 130 by envelope detection. As described above, the frequency determination circuit 164 increases the reliability against external noise.

The envelope detection signal from the A / DC 130 is represented by C
Appropriate signal processing can be performed in the PU main body 162. As a result, variation in the detection level of the reflected wave can be improved. In particular, when the transmission / reception separated type ultrasonic distance measuring apparatus is applied to, for example, an automobile, there is an advantage that a malfunction due to road surface noise and wind noise does not occur. Further, it is possible to use an ultrasonic distance measuring device of a transmission / reception-separation type reflection type without changing the basic configuration for the feel of a hand of a robot, detection of a thin object to be measured, measurement of minute displacement, and the like.

Second Embodiment FIG. 7 shows an ultrasonic receiver 11 of a transmission / reception separated reflection type ultrasonic distance measuring apparatus according to a third embodiment of the present invention.
FIG. 3 is a diagram mainly illustrating the circuit configuration of FIG. The ultrasonic receiver 11A includes a preamplifier / buffer circuit 110, a high-frequency signal filtering circuit 112, a ranging sensitivity correction circuit 114, a low-frequency signal filtering circuit / buffer circuit 116, a detection circuit 130 similar to that illustrated in FIG. A distance measurement calculation control circuit 140 similar to that illustrated in FIG. 6, a distance measurement target object type setting device 154 and a temperature sensor 156 are provided.

In the ultrasonic distance measuring apparatus of the transmission / reception separated type reflection system according to the present embodiment, the sensitivity of the distance measuring sensitivity correcting circuit 114 in the CPU main body 162 of the distance measuring arithmetic control circuit 140 of the distance measuring arithmetic control circuit 140 is particularly high. Ultrasonic sensor sensitivity correction data for correction is generated, and the sensitivity of the received ultrasonic signal is corrected in the ranging sensitivity correction circuit 114 based on the ultrasonic sensor sensitivity correction data. The ultrasonic sensor sensitivity correction data is determined based on the type of the distance measurement target object 7 set by the distance measurement target object type setting device 154, for example, a metal, concrete, or human body, and a distance measured by the CPU main body 162. . Therefore, data for the ultrasonic sensor sensitivity correction data is collected in advance and stored in the storage unit.

As described above, the ultrasonic sensor sensitivity correction data is collected in advance. In the actual measurement, first, the transmission ultrasonic sensor 3 is driven, and the CPU main body 162 calculates the temporary distance from the reception signal of the reception ultrasonic sensor 13 without performing the sensitivity correction in the distance measurement sensitivity correction circuit 114. Measure. The CPU main body 162 also determines the determined temporary distance and the type setting device 15 of the distance measurement target object.
The ultrasonic sensor sensitivity correction data to be performed by the distance measurement sensitivity correction circuit 114 is generated in accordance with the type of the distance measurement target object 7 set in step 4, and is set in the distance measurement sensitivity correction circuit 114. Next, the transmission ultrasonic sensor 3 is driven again. The signal received by the ultrasonic sensor for reception 13 is a distance measurement sensitivity correction circuit 1
At 14, the sensitivity is corrected. The detection circuit 118 detects the sensitivity-corrected reception signal, and the CPU 162 calculates the actual distance from the time from transmission to reception.

The type setting device 154 of the object whose distance is to be measured
Sets the type of the distance measurement target object 7. The temperature sensor 156 measures the ambient temperature (outside air temperature) where the receiving ultrasonic sensor 13 is installed. The CPU main body 162 receives the temperature detected by the temperature sensor 126, calculates the propagation speed of the ultrasonic wave at that time, and calculates the distance based on the propagation speed at that time. The calculation formula will be described later.

The ultrasonic sensor sensitivity correction data stored in the memory will be described with reference to FIGS.
Distance measurement target object 7 radiated from the transmitting ultrasonic sensor 3
The intensity of the reflected wave of the ultrasonic wave (amplitude in the ultrasonic sensor 13 for reception) that varies with the type of the distance measurement target object 7 varies. The same distance measuring object 7 is also transmitted to the transmitting ultrasonic sensor 3 or the receiving ultrasonic sensor 13 (hereinafter simply referred to as an ultrasonic sensor) and the distance measuring object 7.
The intensity of the receiving ultrasonic sensor 13 (amplitude in the receiving ultrasonic sensor 13) changes according to the distance between.
That is, when an ultrasonic wave excited by the transmission ultrasonic sensor 3 under the same conditions is applied to the distance measurement target object 7, the distance measurement target object 7 depends on the type, material, and degree of surface roughness of the distance measurement target object 7. The intensity of the ultrasonic wave reflected by the ultrasonic wave 7 and received by the ultrasonic sensor 13 for reception changes. For example,
The signal level of the received wave received by the receiving ultrasonic sensor 13 changes between the case where the distance measurement target object 7 is a metal having a smooth surface and a hard metal and the case where the surface is rough and has a hardness lower than that of the metal. Further, even if the distance measurement target object 7 is of the same type, for example, metal, as the distance between the ultrasonic sensor and the distance measurement target object 7 increases, the amplitude of the reflected ultrasonic wave in the receiving ultrasonic sensor 13 decreases. Become.

Therefore, the following measurement is performed. (1) First, a reference attenuation characteristic of a reference distance measurement target object 7, for example, a member such as a mirror that ideally reflects ultrasonic waves is measured. That is, a mirror is used as the distance measurement target object 7, an ultrasonic wave is applied from the transmission ultrasonic sensor 3, and the ultrasonic wave is received by the reception ultrasonic sensor 13,
A signal passed through the preamplifier / buffer circuit 110, the high-frequency signal filtering circuit 112, the ranging sensitivity correction circuit 114, the low-frequency signal filtering circuit / buffer circuit 116, and detected by the detection circuit 130 is processed by the arithmetic and control unit (CPU) 160. The maximum amplitude of the envelope detection signal is detected and stored. This measurement is performed by variously changing the distance between the distance measurement target object 7 and the transmission ultrasonic sensor. The data obtained as a result is reference attenuation characteristic data. (2) Next, for various distance measurement target objects 7, data obtained when the distance between the distance measurement target object 7 and the transmission ultrasonic sensor 3 is variously changed is stored in the memory in the same manner as described above. (3) The attenuation data for the reference attenuation characteristic is calculated by comparing the reference attenuation characteristic with data measured for various distance measurement target objects 7. For example, a difference between the maximum amplitude in the reference attenuation characteristic and the maximum amplitude in the attenuation characteristic of each distance measurement target object 7 is calculated as a relative attenuation characteristic of each distance measurement target object 7.

When the above processing is completed for all the distance measurement target objects 7 for the distance measurement range,
By organizing the measurement results, an ultrasonic attenuation curve illustrated as curves A and B in FIG. 8 is created in comparison with the case where a mirror is used as the distance measurement target object 7. Thus, the degree of attenuation of the distance measurement target object 7 differs between concrete and metal. Further, as the distance between the ultrasonic sensor and the distance measurement target object 7 increases, the signal level of the reflected ultrasonic wave propagating in the air decreases. When the level of the reflected ultrasonic wave decreases, the level of the detection signal in the detection circuit 130 does not reach the predetermined level, and the CPU main unit 162
, The reception of the reflected ultrasonic wave cannot be detected. Therefore, the distance measurement sensitivity correction circuit 114 performs sensitivity correction as described below with reference to FIG.

Step 11 : The ultrasonic sensor sensitivity correction data illustrated in FIG. 8, that is, correction data indicated by curves C and D is generated from the ultrasonic attenuation characteristics created in step 10.

In FIG. 8, a horizontal line E extending to the right from the origin 0 is a line indicating the attenuation characteristics when a member having ultrasonic perfect reflection characteristics such as a mirror is used as the object 7 for distance measurement. Although this line is expressed as if there is no attenuation, it shows a reference for the attenuation characteristic when the distance measuring object 7 is metal or concrete. Curve A is
When the distance measurement target object 7 is concrete, when the distance between the ultrasonic sensor and the distance measurement target object 7 is predetermined,
7 shows a relative attenuation characteristic with respect to a reference attenuation characteristic when a mirror is used as the distance measurement target object 7. For example, at the distance L1, when the distance measurement target object 7 is concrete, the distance measurement target object 7 is attenuated by an amount of Y to Q1 compared to when the distance measurement target object 7 is a mirror. Curve B indicates a relative relative attenuation characteristic with respect to a reference when the distance is between the ultrasonic sensor and the distance measuring object 7 when the distance measuring object 7 is a metal, and when the distance between the ultrasonic sensor and the distance measuring object 7 is predetermined. Shows attenuation characteristics. For example, at the distance L1, when the distance measurement target object 7 is a metal, the distance measurement target object 7 is attenuated by an amount of Y to Q2 compared to when the distance measurement target object 7 is a mirror.

Curves C and D show the ultrasonic sensor sensitivity correction data corresponding to the attenuation curves A and B, respectively. Curve C is line 0
-E is sandwiched between the curve B and the line B, and the distance measurement sensitivity correction circuit 11 is provided with YP2 corresponding to the relative attenuation YQ2.
4 shows data for sensitivity correction. The curve D has a line-symmetric relationship with the curve B with respect to the line 0-E, and shows data for which the distance measurement sensitivity correction circuit 114 performs sensitivity correction by YP1 corresponding to the relative attenuation YQ1. C
The PU main body 162 corrects the signal received by the receiving ultrasonic sensor 13 according to the ultrasonic sensor sensitivity correction data based on the curves C and D. As the attenuation due to reflection increases, the correction amount in the distance measurement sensitivity correction circuit 114 increases.

As a method of correction by the ultrasonic sensor sensitivity correction data in the distance measurement sensitivity correction circuit 114, the distance measurement sensitivity correction circuit 114 is constituted by a variable gain amplifier circuit,
The gain is changed based on the ultrasonic sensor sensitivity correction data from the main body 162.

Step 12 : The generated ultrasonic sensor sensitivity correction data is stored in the memory of the arithmetic and control unit (CPU) 160.

As a method of storing the ultrasonic sensor sensitivity correction data in the memory of the arithmetic and control unit (CPU) 160 in each ultrasonic distance measuring apparatus, a break point (break point) of the data shown by the curves C and D is used. Store in memory. When used as ultrasonic sensor sensitivity correction data described later, break point data is interpolated and used.

According to an experiment, when a drip-proof type ultrasonic sensor is used as the transmitting ultrasonic sensor 3 and the receiving ultrasonic sensor 13, an ultrasonic wave sensor capable of performing accurate and stable measurement based on the present embodiment. The distance between the sound wave sensor and the object 7 to be measured can be extended from 4 to 5 m to 12 to 15 m.
In other words, by correcting the sensitivity of the drip-proof ultrasonic sensor using the ultrasonic sensor sensitivity correction data in the distance measurement sensitivity correction circuit 114, the measurable distance is extended. Also, considering the simplification of the circuit described in the first embodiment, the improvement of the distance measurement accuracy, and the improvement of the reliability against noise, etc., the ultrasonic distance measuring apparatus of the transmission / reception separated type reflection type of the present embodiment is considered. High reliability (high circuit stability), high accuracy and long distance measurement are possible.

Therefore, when the transmission / reception separated type ultrasonic distance measuring apparatus according to the present embodiment is applied to, for example, a vehicle, the conventional purpose is to mainly prevent collision with a garage wall when the garage is placed. What is used can be applied not only to collision prevention in garages but also to various uses. For example, the ultrasonic transmission / reception-type reflection-type ultrasonic distance measuring apparatus according to the present embodiment can be applied to distance measurement between a preceding and following vehicle when traveling on a road. For example, it is possible to detect that a vehicle before or behind a road is approaching, for example, approaching within 10 m. Therefore, at that time, if an alarm is output, an alarm can be issued to the driver. As a warning to the driver, a warning of the approaching state of the driver equipped with the transmission / reception separate type reflection type ultrasonic distance measuring device, and the approach of the following vehicle to the driver if the following vehicle is too close. For example, a case where an excessive warning is output may be considered.

The implementation of the method for and apparatus for measuring the ultrasonic distance of the transmission / reception-separation type reflection type according to the present invention is not limited to the above-described embodiment, but may take various modifications. For example, the distance measurement sensitivity correction circuit 114 illustrated in FIGS. 2, 3A, 6, and 7 is particularly desirable when the distance measurement range is lengthened, but is not essential. The deleted circuit configuration shown in FIG. 6 can be adopted.

The transmitting ultrasonic sensor 3 and the receiving ultrasonic sensor 13 are not limited to the piezoelectric ceramic ultrasonic sensor exemplified above, more specifically, the lithium ceramic niobate piezoelectric ceramic ultrasonic sensor. In addition, various ultrasonic sensors can be used.

The above-described control device 21, ultrasonic transmitter 1,
The configuration and operation of the ultrasonic receivers 11 and 11A and the configuration and operation of the distance measurement calculation control circuit 140 are examples, and the configuration and the operation are not limited by the above-described configuration.

As described above, the ultrasonic distance measuring method and apparatus of the transmission / reception separated type reflection method according to the present invention, particularly when the transmission ultrasonic sensor 3 and the reception ultrasonic sensor 13 are drip-proof ultrasonic sensors. However, the present invention is not limited to the case where the drip-proof ultrasonic sensor is used, but also has the above-described effect when a normal ultrasonic sensor is used.

[0060]

According to the present invention, highly reliable and accurate distance measurement can be performed with a simple circuit configuration.

Further, according to the present invention, by appropriately correcting the sensitivity of the ultrasonic sensor, even when a drip-proof ultrasonic sensor is used, the distance of the ultrasonic distance measurement of the transmission / reception separation type reflection type can be reduced. Could be longer. Further, according to the present invention, since the sensitivity is corrected in accordance with the type of the distance measurement target object or the distance, the distance measurement is reliably and stably performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a transmission / reception separated type ultrasonic distance measuring apparatus.

FIG. 2 is a basic configuration diagram of a receiver of an ultrasonic distance measuring apparatus of a transmission / reception separated type reflection type according to the present invention.

3 (A) is a configuration diagram of a distance measurement arithmetic control circuit in a transmission / reception separated type reflection type ultrasonic distance measurement device as a background art, and FIG. 3 (B) is a detection diagram in FIG. 3 (A); FIG. 3 is a circuit configuration diagram of a circuit and a buffer circuit / comparison circuit.

4 (a) to 4 (g) show the operation of the transmission / reception separated type ultrasonic distance measuring device of FIG. 3 (A) and the operation of the transmission / reception separated type reflection type ultrasonic distance measuring device of FIG. 6; FIG. 4 is a signal waveform diagram to be described.

5 (a) to 5 (e) show the operation of the transmission / reception separated type ultrasonic distance measuring device of FIG. 3 (A) and the operation of the transmission / reception separated type reflection type ultrasonic distance measuring device of FIG. 6; FIG. 4 is a signal waveform diagram to be described.

FIG. 6 is a configuration diagram of a distance measurement operation control circuit in the transmission / reception separated type ultrasonic distance measurement apparatus according to the first embodiment of the present invention.

FIG. 7 is a configuration diagram of a distance measurement calculation control circuit in a transmission / reception separated type ultrasonic distance measurement apparatus according to a second embodiment of the present invention.

FIG. 8 is a correction curve for performing a correction process in the distance measurement calculation control circuit of FIG. 7;

FIG. 9 is a flowchart showing a method for obtaining ultrasonic sensor sensitivity correction data.

[Explanation of symbols]

 1. Ultrasonic transmitter 3. Ultrasonic sensor for transmission 5. Horn antenna for transmission 7. Object to be measured for distance 11. Ultrasonic receiver 110. Preamplifier circuit / buffer circuit 112. High frequency signal Filtering circuit 114 Distance measuring sensitivity correction circuit 116 Low frequency signal filtering circuit / buffer circuit 118 Detection circuit 120 Buffer circuit / comparison circuit 122 Distance measurement arithmetic control circuit 130 Detection circuit 130 132・ Analog / digital conversion circuit 140 ・ ・ Distance measurement calculation control circuit 150 ・ ・ Crystal oscillation circuit 160 ・ ・ Calculation control unit (CPU) 154 ・ ・ Type setting device for distance measurement target object 156 ・ ・ Temperature sensor 13 ・ ・ Reception Ultrasonic sensor 15 ・ ・ Reception horn antenna 21 ・ ・ Control device

Claims (5)

[Claims] An ultrasonic wave radiated from an ultrasonic sensor for transmission is reflected by an object to be measured, and the reflected ultrasonic wave is received by an ultrasonic sensor for reception. From transmission of ultrasonic waves to reception of ultrasonic waves An ultrasonic distance measuring apparatus of a transmission / reception separation type reflection type that measures the time of the transmission ultrasonic sensor or the reception ultrasonic sensor from the measurement time to measure the distance from the distance measurement target object to the distance measurement target object, The ultrasonic distance measuring device includes: a transmitting device that performs drive control of the transmitting ultrasonic sensor; a receiving device that processes a signal from the receiving ultrasonic sensor to measure a distance; the transmitting device and the receiving device Control means for controlling the apparatus, the receiving apparatus comprises: an envelope detection means, an arithmetic processing means, and a clock signal generation circuit of the arithmetic processing means, wherein the arithmetic processing means comprises the clock Faith A frequency dividing circuit for dividing the frequency of the original oscillation signal from the generating circuit; a counting means for counting the frequency-divided clock from the frequency dividing circuit; and a normal reception signal detected from the envelope detection signal from the envelope detection means. Receiving signal detecting means, and counting means for counting the frequency-divided signal by the counting means from the oscillation of the ultrasonic wave to the detection of the receiving signal, wherein the distance is calculated from the counting result. An ultrasonic distance measuring apparatus of a transmission / reception separated type reflection type having a distance calculating means. 2. An ultrasonic distance measuring apparatus according to claim 1, wherein said envelope detection means includes an analog / digital conversion circuit. 3. The arithmetic processing unit monitors a frequency component of a signal input to the envelope detection unit, and when a signal of a predetermined frequency component is applied to the envelope detection unit, the envelope detection unit monitors the frequency component of the signal. 3. An ultrasonic distance measuring apparatus according to claim 2, wherein said means substantially operates. 4. The transmission / reception separation type reflection system according to claim 1, wherein the transmission ultrasonic sensor is a drip-proof transmission ultrasonic sensor, and the reception ultrasonic sensor is a drip-proof reception ultrasonic sensor. Ultrasonic distance measuring device. 5. The receiver according to claim 1, further comprising: a sensitivity correction circuit that corrects a sensitivity of a reception signal in the receiving ultrasonic sensor before the envelope detection means. 5. An ultrasonic distance measuring apparatus according to claim 4, wherein the output is detected.