JPS6264973A - Ultrasonic range finder - Google Patents

Abstract

PURPOSE:To make it possible to measure the distance up to objective matter present in a wide range from a short distance to a long distance by a single apparatus, by automatically adjusting the oscillation frequency of an ultrasonic wave. CONSTITUTION:When objective matter is present at a relatively short distance within a predetermined range, the pulse width of the output signal Sf outputted from a FF circuit 10 comes to T1 and a pulse width discriminating circuit 11 discriminates that said width T1 is shorter than the predetermined time interval Ts preset to the circuit 11. On the basis of this result, a transmitting frequency control circuit 12 enhances the oscillation frequency of a transmitting frequency oscillation circuit 3. Contrarily, when the objective matter is present at a relatively long distance out of the predetermined range,the pulse width of the signal Sf outputted from the circuit 10 comes to T2 and the circuit 11 discriminates that the width T2 is longer than the interval Ts. On the basis of this result, the circuit 12 lowers the oscillation frequency of the circuit 3. As mentioned above, the oscillation frequency of an ultrasonic wave is automatically adjusted corresponding to the distance up to the objective matter and the distance up to the objective matter can be measured.

Description

Detailed Description of the Invention "Industrial Application Field" This invention provides a method for detecting the distance to a target object based on the L'J interval from when an ultrasonic wave is emitted until the reflected wave of the ultrasonic wave is detected. The present invention relates to an ultrasonic distance measuring device that measures distance.

"Prior Art" FIG. 3 is a block diagram showing the configuration of a conventional ultrasonic distance measuring device. In this FIG. 7, 1 is a timing circuit, 2 is a transmission pulse generation circuit, and these
A transmission pulse signal Sa having a constant period TO+T and a constant pulse width T shown in a) is generated. 3 is a transmission frequency oscillation circuit;
4 is a gate circuit, and the gate circuit 4 generates the transmission signal shown in FIG. A signal sb is generated and supplied to the transmitter drive circuit 5. Reference numeral 6 denotes a transmitting ultrasonic transducer (hereinafter simply referred to as a transmitting transducer) that converts an electric signal supplied from the transmitter drive circuit 5 into an ultrasonic wave.

On the other hand, 7 is a reception ultrasonic transducer (hereinafter simply referred to as reception transducer) that converts ultrasound into an electric signal, and 8 is a reception signal amplification circuit that amplifies the reception signal detected by reception transducer 7. It is. 9 detects the received signal Sc shown in FIG. 4(c) amplified by the received signal amplification circuit 8 to produce the signal Sd shown in FIG. 4(d),
This is a signal detection and shaping circuit that further shapes the waveform and generates the received pulse signal Se shown in FIG. 4(E). 10 is set at the rising edge of the transmitting pulse signal Sa supplied from the transmitting pulse generating circuit 2, and is reset at the rising edge of the receiving pulse signal Se supplied from the signal detection and shaping circuit 9, as shown in FIG. This is a flip-flop circuit that outputs the output signal S shown in

The ultrasonic pulse emitted from the transmitting transducer 6 propagates through the air, hits the target object and is reflected, and this reflected wave propagates through the air again and returns to the receiving transducer 7. This reflected wave is converted into an electrical signal by the receiving transducer 7, and the received signal amplifying circuit 8
The received pulse signal Se is amplified by the signal detection and shaping circuit 9, and is further subjected to detection and waveform shaping by the signal detection and shaping circuit 9.
This received signal Se is supplied to the flip-flop circuit IO.

Here, the relationship between the pulse interval Tp of the output signal SF of the flip-flop circuit IO and the distance Q to the target object is as shown in the following equation.

12Cm) = 1/2X speed of sound (m/sl)
Cs) Therefore, by measuring the pulse interval Tp of the output signal Sr of the flip-flop circuit 10, the distance to the target object can be obtained.

"Problems to be Solved by the Invention" By the way, the degree of attenuation due to the air propagation distance of the ultrasonic waves emitted from the transmitting transducer 6 is as high as the transmitting frequency. In the conventional ultrasonic distance measuring device described above, the transmission frequency is always constant, so there is a problem that the measurable range is limited. In other words, when measuring the distance to a target object within a relatively short range with high accuracy, the transmission frequency must be increased, but in this case, after the ultrasonic wave is emitted, the transmission frequency suddenly increases. Because of the attenuation, it becomes impossible to measure the distance to a target object that is relatively far away. Conversely, when measuring the distance to a target object that is relatively far away, it is necessary to lower the transmission frequency in order to minimize the degree of attenuation due to air propagation distance. The resolution decreases in all ranges up to long distances, resulting in low distance measurement accuracy.

This invention was made in order to solve the two conflicting problems mentioned above: if you try to expand the measurement range, the measurement accuracy will decrease, and if you try to increase the measurement accuracy, the measurement range will be limited. Ultrasonic measurement is capable of measuring the distance to a target object within a relatively short range with high precision, and can also measure the distance to a target object located at a long distance. The purpose is to provide a range device.

"Means for Solving the Problem" The present invention has a measuring means for measuring the time interval from when an ultrasonic wave is emitted by an ultrasonic emitting means until a reflected wave of the ultrasonic wave is detected, In an ultrasonic distance measuring device that measures the distance to a target object based on the measurement result of the measurement means, a distance discrimination device that determines whether the distance to the target object is equal to or greater than a predetermined distance based on the measurement result of the measurement means. and if the distance to the target object is determined by the distance determining means to be less than or equal to the predetermined distance, the transmission frequency of the ultrasonic waves emitted from the ultrasonic emitting means is increased; The apparatus is characterized by comprising a transmission frequency control means for lowering the transmission frequency of the ultrasonic waves emitted from the ultrasonic emission means when it is determined that the distance is greater than the predetermined distance.

"Effect" The transmission frequency of the ultrasonic waves is adjusted according to the distance to the target object, which makes it possible to measure the distance to the target object within a relatively short range with high precision. It is also possible to measure the distance to a target object that is located far away.

"Example" Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and parts corresponding to those in FIG. 3 are designated by the same reference numerals, and their explanations will be omitted.

In this figure, 11 is a pulse width discrimination circuit that determines whether the pulse width of the output signal Sr of the flip-flop circuit 10 is equal to or longer than a predetermined time interval Ts. Reference numeral 12 denotes a transmission frequency control circuit that controls the oscillation frequency of the transmission frequency oscillation circuit 3 based on the determination result of the pulse width discrimination circuit 11. This transmission frequency control circuit 12 is controlled by a flip-flop circuit 10 by a pulse width discrimination circuit 11.
If it is determined that the pulse width of the output signal Sr is less than or equal to the predetermined time interval Ts, the oscillation frequency of the transmission frequency oscillation circuit 3 is increased, and conversely, the pulse width discrimination circuit 11 increases the pulse width of the output signal Sf. If it is determined that the pulse width is greater than or equal to the predetermined time interval Ts, the oscillation frequency of the transmission frequency oscillation circuit 3 is lowered.

In such a configuration, when the target object is present at a relatively short distance within a predetermined range, the transmission signal sb output from the gate circuit 4 and the reception signal Sc output from the reception signal amplification circuit 8 , and the received pulse signal Se output from the signal detection and shaping circuit 9, for example, as shown in FIG.
It becomes as shown in ~(c). In such a relationship,
Output signal Sf output from the flip-flop circuit 10
The pulse width is T1 as shown in FIG. 2(d), and the pulse width T1 is shorter than the predetermined time interval Ts preset in the pulse width discrimination circuit 11 shown in FIG. 2(e). This is determined by the width discrimination circuit 11. Based on this determination result, the transmission frequency control circuit 12 increases the oscillation frequency of the transmission frequency oscillation circuit 3.

Conversely, when the target object is located at a relatively long distance outside the predetermined range, the transmission signal sb output from the gate circuit 4
The relationship between the received signal Sc outputted from the received signal amplification circuit 8 and the received pulse signal Se outputted from the signal detection shaping circuit 9 is, for example, as shown in FIGS. become. In this relationship, the pulse width of the output signal Sr output from the flip-flop circuit IO is the second
As shown in FIG. 2(e), the pulse width is T, and the pulse width discrimination circuit 11 determines that this pulse width T1 is longer than the predetermined time interval Ts shown in FIG. 2(e).

Based on this determination result, the transmission frequency control circuit l.

2 lowers the oscillation frequency of the transmission frequency oscillation circuit 3.

In this way, the oscillation frequency of the ultrasonic waves is automatically adjusted according to the distance to the target object, and the distance to the target object is measured.

"Effects of the Invention" As explained above, according to the present invention, the oscillation frequency of ultrasonic waves is automatically adjusted according to the distance to the target object, so It is possible to measure the distance to a target object existing in a wide range with a single device, and at the same time, it is possible to obtain an effect of improving the accuracy of distance measurement for a target object existing at a short distance.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an ultrasonic distance measuring device according to an embodiment of the present invention, FIGS. Block diagram showing the configuration of the ultrasonic distance measuring device, Fig. 4 (a)
~(f) are timing charts showing signals of each part of the device. 3...Transmission frequency oscillation circuit, 6...Transmission transducer, 7...Reception transducer, 10...Flip-flop circuit (measuring means) , 11...Pulse width discrimination circuit (distance discrimination means)
, 12... Transmission frequency control circuit.

Claims (1)

[Claims] It has a measuring means for measuring the time interval from when the ultrasonic wave is emitted by the ultrasonic emitting means until the reflected wave of the ultrasonic wave is detected, and the distance to the target object is determined based on the measurement result of the measuring means. In an ultrasonic distance measuring device for measuring a distance, the distance determining means determines whether the distance to the target object is greater than or equal to a predetermined distance based on the measurement result of the measuring means, and the distance determining means determines the distance to the target object. If the distance to the target object is determined to be less than the predetermined distance, the transmission frequency of the ultrasonic waves emitted from the ultrasonic emitting means is increased; conversely, if the distance to the target object is determined to be greater than the predetermined distance, the ultrasonic wave is emitted. 1. An ultrasonic ranging device comprising: a transmission frequency control means for lowering the transmission frequency of ultrasonic waves emitted from the means.