JPH0682156B2 - Ultrasonic distance measuring device - Google Patents

Description

The present invention relates to an ultrasonic distance measuring device for detecting an object by transmitting an ultrasonic wave composed of a pulse train and receiving a reflected wave from the object. It is a thing.

[Prior Art] FIG. 3 is a block diagram of a conventional ultrasonic distance measuring device that detects the presence of an object and measures the distance to the object from the presence or absence of a reflected wave of an ultrasonic pulse and the time delay from the transmission. Is shown. This ultrasonic distance measuring device is composed of a detector 1 and a signal processor 2 '. The transmission timing control unit 2a of the signal processing unit 2'determines the transmission timing of the transmission circuit 1b, the signal from the transmission circuit 1b is amplified by the transmission drive circuit 1c, and drives the ultrasonic transducer 1a. . The wave reception gate circuit 1d opens the gate for a predetermined time to receive the reflected wave from the object, and the wave transmission timing control unit 2a determines the time. Then, the wave reception circuit 1e receives the reflected wave, and the distance calculation unit 2b of the signal processing unit 2 calculates the distance and outputs a detection output.

FIG. 4 shows a time chart of the operation, in which the distance from the signal that first appears in the receiving gate 6 to the object is determined by the above-mentioned configuration. However, even if the noise 5 comes in before the received pulse 4, the receiving circuit 1e cannot distinguish whether it is the noise or the reflected wave from the object, and the distance is calculated as it is. It was Since it is not possible to determine when the noise 5 is mixed in, even if the distance is obtained by the received pulse 4 at one time, the distance is obtained by the noise 5 at some times, so the distance measured at each detection is Differently, there is a problem that the reliability of the obtained distance data is low.

[Problems to be Solved by the Invention] Therefore, a detection signal is first output when a reflected wave from an object is continuously received a predetermined number of times or more.
The present inventor has devised a plurality of continuous detection means for stopping the detection signal for the first time when there is no received signal for the continuous number of times (Japanese Patent Application 59-228.
No. 763, Japanese Patent Application No. 59-228764), to prevent false detection due to noise. However, when the above-mentioned plural times continuous detection means is used, the response time until detection becomes slower than that of the conventional one, and further, as shown in FIG. Even if the distance is obtained, if the noise 5 is mixed in the last n times, the distance data is obtained from the noise 5, so that there is a problem in data reliability.

The present invention has been provided in view of the above-mentioned points, and compared with the conventional one, the response time to detection is comparable, and the ultrasonic distance measurement is designed to increase the reliability of distance measurement data. The purpose is to provide a device.

[Means for Solving the Problems] The present invention transmits a plurality of ultrasonic pulses having different transmission frequencies and simultaneously receives ultrasonic waves from a plurality of detection units that receive reflected waves. And a frequency selection circuit provided in each detection unit for attenuating ultrasonic signals reflected from other detection units other than the frequency transmitted by itself. And a distance calculation unit that detects the presence of an object and the distance to the object from the received signals obtained by the respective detection units, and the presence detection of the object is performed by all the detection units based on the signal from the distance calculation unit. When there is a received wave in the above, the distance to the above object is ignored and the latter is used only when the obtained partial distance differs from the other distance by a preset value or more. It has a judgment unit that outputs is there.

[Operation] Then, the presence detection of the object is performed by the determination unit that receives the signal from the received signal obtained by each detection unit and the presence calculation of the object and the distance calculation unit that measures the distance to the object. When all the detectors receive a wave, the distance to the above object is ignored by ignoring the former if some of the obtained distances are different from other distances by a preset value or more. I am trying to output using only.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. First
The figure shows a block diagram of an ultrasonic distance measuring apparatus, in which a plurality of detecting units 11, 12, ... 1n (n ≧ 2) having the same configuration as the conventional detecting unit 1 are provided. Further, these detection units 11 ... Have different transmission frequencies.

The following description is common to the detection units 11 ...
The wave transmission circuit 1b is a circuit that generates an ultrasonic pulse of a tone burst wave having a preset duration and a frequency different from that of other detection units. The wave transmission drive circuit 1c is a circuit that amplifies the ultrasonic pulse signal obtained by the wave transmission circuit 1b so as to sufficiently drive the ultrasonic transducer 1a (in the present embodiment, the ultrasonic transducer 1a transmits and receives signals). I am using a body type,
It does not matter even if you use two ultrasonic transducers dedicated to wave transmission and wave reception). The receiving gate circuit 1d includes the signal processing unit 2
The signal from the transmission timing control unit 2a is used as a trigger, and after waiting for a predetermined time from this trigger signal, the reception pulse is received until a time delay corresponding to the detection distance range.
Send to 1e. The wave receiving circuit 1e has a frequency selection circuit therein, and attenuates ultrasonic signals other than the frequency transmitted by itself, thereby only the received pulse due to reflection of the ultrasonic pulse of itself from the object. Is amplified to obtain a signal from which the distance calculation unit 2b can obtain the distance.

Next, there is only one wave transmission timing control section 2a for transmitting the input signal of each wave transmission circuit 1b, whereby each detection section 1 is provided.
1,12, ... 1n transmit waves at the same time. The distance calculation unit 2b uses the output signal from each wave reception circuit 1e to detect each detection unit 11b.
The existence of the object and the distance to the object detected in step S6 are obtained.
In addition, the determination unit 2c determines the detection output from a plurality of object existences and distance data obtained by the distance calculation unit 2b as described later. It should be noted that the signal processing unit 2 is configured by the transmission timing control unit 2a, the distance calculation unit 2b, and the determination unit 2c, and in the present embodiment, it is realized by using a microprocessor, but it is not limited to this. .

The ultrasonic distance measuring apparatus of the present invention comprises a plurality of detection units having different transmission frequencies, and the detection units are timed so as to simultaneously transmit detection unit pulses, and each detection unit is It has a frequency selection circuit that attenuates ultrasonic signals reflected from other detection units other than the frequency transmitted by itself, from the received signal obtained by each detection unit to the presence detection and object detection of each object. It has a distance calculator that measures the distance. Then, the presence of an object is detected when all the detection units have received waves, and regarding the distances to the objects, the distances calculated by the respective distance calculation units are all within a predetermined distance range ε. Output when there is.

If noise is mixed and the distance obtained by some distance calculation units differs from the distance obtained by other distance calculation units by a preset value or more, ignore the former and use only the latter. , Output only when they are all within a predetermined distance range.

The operation will be specifically described below. FIG. 2 shows a time chart. Each of the ultrasonic transducers 1a is further amplified by the transmission drive circuit 1c at the transmission intervals determined by the transmission timing control unit 2a in the signal processing unit 2 and at the frequencies determined by the transmission circuit 1b. Transmission is performed by the drive signal, and the ultrasonic pulse hits the object and is reflected, and returns to each ultrasonic transducer 1a and is received with a time delay corresponding to the distance to the object. The plurality of ultrasonic transducers 1a are installed as close as possible in order to minimize the difference in distance to the object. The received signal passes through the wave reception gate circuit 1d and enters the wave reception circuit 1e. At this time, the receiving circuit 1e has a frequency selecting circuit that attenuates components other than the transmitting frequency, and the receiving pulse 4 by the transmission of another ultrasonic transducer is
Can also be attenuated, and noise of frequency components other than the transmission frequency can be attenuated, and only the reception pulse 4 by the transmission by itself is selected for noise having a specific frequency component.

The output of each receiving circuit 1e is the distance calculation unit in the signal processing unit 2.
The existence of the objects collected in 2b and detected by the respective detection units 11 ... Figure 2 (a),
(B), ..., (n) represent the state of reception of the respective detection units 11, ... For example, the reception pulse 4 in FIG.
With reference to the time delay Ta from the transmission pulse 3 of the above, the time delays Tb, ..., Tn of the received pulse 4 from the transmission pulse 3 in the remaining (b), ..., (n) of FIG. ,) Ta · c / 2−ε ≦ Tx · c / 2 ≦ Ta · c / 2 + ε, where ε is the allowable distance error c is the condition that the sound velocity is not satisfied Tx (noise 5 in Fig. 2 is (B) Tb preceding the received pulse 4 corresponds to this) is removed,
Using other Tx, for example, the average is taken and used as the detection output. There is no problem even if the minimum value is selected without taking the average.

In the case where Ta is the noise 5 preceding the received pulse 4, most of the cases do not satisfy the condition when Ta is used as a reference. In such a case, the determination unit 2c changes the reference. Try again as Tx. By doing so, even if the noise 5 is mixed in a part of the detection units, the majority of the devices will be decided, so that the reliability of the data is improved.

[Advantages of the Invention] As described above, the present invention transmits ultrasonic pulses having different transmission frequencies and simultaneously receives ultrasonic waves from a plurality of detection units that receive reflected waves. And a frequency selection circuit provided in each detection unit for attenuating ultrasonic signals reflected from other detection units other than the frequency transmitted by itself. And a distance calculation unit that detects the presence of an object and the distance to the object from the received signals obtained by the respective detection units, and the presence detection of the object is performed by all the detection units based on the signal from the distance calculation unit. When there is a received wave in the above, the distance to the above object is ignored and the latter is used only when the obtained partial distance differs from the other distance by a preset value or more. And a determination unit for outputting Therefore, the presence detection of the object is performed by all the detection units by the determination unit that receives the signal from the distance detection unit that detects the presence of the object and the distance to the object from the received signal obtained by each detection unit. When there is a received wave in the above, the distance to the above object is ignored and the latter is used only when the obtained partial distance differs from the other distance by a preset value or more. Therefore, compared with the conventional ultrasonic distance measuring device, the response time to detection is comparable to that of the conventional ultrasonic distance measuring device, and the ultrasonic distance measuring device that increases the reliability of the distance measurement data is used. This is an effect that can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is an operation waveform diagram of the above, FIG. 3 is a block diagram of a conventional example, FIG. 4 is an operation waveform diagram of the same, and FIG. It is a waveform diagram. 11, 12 ... 1n is a detection unit, 2 is a signal processing unit, 2a is a transmission timing control unit, 2b is a distance calculation unit, and 2c is a determination unit.

Claims (1)

[Claims] 1. An ultrasonic distance measuring device for detecting the presence of an object and measuring the distance to the object by transmitting an ultrasonic pulse and receiving a reflected wave from the object. Provided in each detection unit, a plurality of detection units that transmit different ultrasonic pulses and receive reflected waves, a transmission timing control unit that simultaneously transmits ultrasonic pulses from all detection units, and each detection unit. , Each detection unit attenuates ultrasonic signals reflected from other detection units other than the frequency transmitted by itself, and the presence detection of each object from the received signal obtained by each detection unit And the distance calculation unit that measures the distance to the object, and the presence detection of the object by the signal from the distance calculation unit is performed when all the detection units receive the wave, and the distance to the object is Compared with other distances Ultrasonic distance measuring apparatus characterized by comprising a determination unit that outputs using only the latter ignoring the former if a different preset value or more.