JPH0448206A - Ultrasonic pulse type body detector - Google Patents

Abstract

PURPOSE:To prevent misdetection due to urban district noises, etc., by providing a wave reception rate calculation part calculating the time rate, which indicates how long a received signal is included, in a received wave gate. CONSTITUTION:An ultrasonic wave vibrator 1 is used for both transmission and reception and sent wave pulses from a control part 3 are supplied intermittently to the ultrasonic wave vibrator 1 thorough a transmitting circuit 2. Then the wave reception rate calculation part 6 which calculates the time rate of the inclusion of the received signal R is provided in the received wave gate G. When the wave reception rate Wb calculated by this wave reception rate calculation part 6 exceeds a preset wave reception rate Wc, it is decided that body detecting operation is not performed normally, and the body detecting operation is inhibited. Consequently, even if a noise which contains an ultrasonic wave component much such as urban district noises is received by the received wave gate G, it can be discriminated from the reflected wave of original ultrasonic wave pulses P from a body and the misdetection can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ultrasonic pulse type object detector that detects objects using ultrasonic pulses, and can be used, for example, as an on-vehicle obstacle sensor. It is something that will be done.

[Prior Art] Object detectors that utilize ultrasonic pulses are conventionally known. This type of object detector first transmits an ultrasonic pulse, receives a reflected wave from an object as a received signal, and detects the presence or absence of an object based on the presence or absence of the received signal. Furthermore, the distance to the object is measured based on the time delay between the time when the ultrasonic pulse is transmitted and the time when the reflected wave is received.

However, in such ultrasonic pulse type object detectors, a single ultrasonic transducer is often used as both the ultrasonic transducer for transmitting waves and the ultrasonic transducer for receiving waves. Even when using separate ultrasonic transducers for transmitting and receiving waves,
The two are often placed close to each other. Therefore, before the ultrasonic pulse from the transmitting ultrasonic transducer is received as a reflected wave from the object by the receiving ultrasonic transducer, There was a risk that the reverberation of the ultrasonic transducer for transmitting waves would be directly received by the ultrasonic transducer for receiving waves, resulting in erroneous detection of the presence or absence of an object or its distance.

Therefore, it has been proposed to set up a reception gate for a certain period of time after the reverberation of the transmitted pulse has subsided, and to detect the presence or absence of an object and the distance based on the reception signal received within this reception gate. . In other words, the reception gate is a time period during which a reception signal is received, and the start time corresponds to the shortest object detection distance, and the end time corresponds to the longest object detection distance.

[Problems to be Solved by the Invention] As described above, in the conventional example, the received signal within the reception gate is recognized as a reflected wave from an object within the detection distance, so ultrasonic components such as urban noise are detected. If noise containing a lot of noise is received within the reception gate, false detections may occur.

The present invention has been made in view of these points, and its purpose is to provide an ultrasonic pulse type object detector that can prevent false detection due to noise containing many ultrasonic components such as city noise. There is a particular thing.

[Means for Solving the Problems] In order to solve the above problems, in the ultrasonic pulse type object detector according to the present invention, as shown in FIG. 1 and FIG. In an ultrasonic pulse type object detector that transmits a wave, receives a reflected wave from an object, and detects an object using a reception signal R within a reception gate G corresponding to a predetermined detection distance range, the The present invention is characterized in that it includes a reception ratio calculating section 6 that calculates the time ratio in which the reception signal R is included in the wave gate G.

Note that it is preferable to include means for prohibiting the object detection operation when the reception ratio calculated by the reception ratio calculation unit 6 exceeds a predetermined value We.

Furthermore, even if the calculated wave reception ratio exceeds a predetermined value We, the object detection operation may not be prohibited and only a warning display may be displayed.Furthermore, the calculated wave reception ratio may simply be displayed numerically. It is also possible to display the information in multiple stages.

[Function] The present invention provides an ultrasonic pulse type object detector that detects an object using a reception signal R within a predetermined reception gate G.
Since it is equipped with a reception ratio calculation unit 6 that calculates the time ratio in which the reception signal R is included in the reception gate G, the reception ratio calculated by the reception ratio calculation unit 6 is set in advance. If the reception ratio We is lower than the reception ratio We, it is determined that the object detection operation can be performed normally, and the normal object detection operation is performed. on the other hand,
If the calculated wave reception ratio exceeds the preset wave reception ratio Wc, it is determined that the object detection operation cannot be performed normally,
Prohibit object detection operation. Alternatively, a warning is displayed to warn that the object detection result is unreliable.

As a result, even if noise containing many ultrasonic components, such as urban noise, is received within the receiving gate, it can be distinguished from the original ultrasonic pulse reflected from an object, preventing false detections. It is preventable.

[Example] FIG. 1 is a block diagram of one embodiment of the present invention.

The ultrasonic transducer 1 is used for both wave transmission and wave reception. Transmission pulses from the control section 3 are intermittently supplied to the ultrasonic transducer 1 via the transmission circuit 2.

As a result, the ultrasonic pulse P shown in FIG. 2 is transmitted from the ultrasonic transducer 1 toward the object. The reflected wave from the object is received by the ultrasonic transducer 1, amplified and detected by the wave receiving circuit 4, and a received signal R shown in FIG. 2 is obtained. Further, the reception gate setting unit 5 sets a reception gate G corresponding to a preset detection distance, and the reception ratio calculation unit 6 calculates the time ratio occupied within the reception gate G of the reception signal R. Calculate as a percentage. Then, the calculated wave reception ratio and the preset wave reception ratio We are compared by the wave reception ratio comparison section 7.

As shown in Fig. 2(a), the calculated reception ratio Wa is
If the reception rate We is lower than the preset reception ratio, the time delay from the transmission time of the ultrasonic pulse P of the reception signal R obtained by the reception circuit 4 is determined, and the time delay from the object to the ultrasonic detector is determined. A distance calculation unit 8 calculates the distance.

The control unit 3 creates a detection output signal based on the distance calculation result of the distance calculation unit 8, and uses an alarm 10 such as a lamp or a buzzer to notify the outside of the presence of the object via the alarm drive unit 9. be. On the other hand, as shown in Fig. 2(b), if the calculated reception ratio wb exceeds the preset reception ratio We, noise N containing many ultrasonic components such as urban noise is received. Since it is thought that the object is being detected and there is a possibility of malfunction, the detection operation for measuring the presence of the object and the distance to the object from the reception signal R obtained by the reception circuit 4 is prohibited.

In other words, since a normal received signal R has a pulse width that is almost the same as that of the transmitted pulse P or a little wider, if a reception ratio Wc that is slightly wider than this pulse width is set in advance, W
In the case of Fig. 2 (a) where a<Wc, it is normal, and W e<
In the case of FIG. 2(b) where W b is reached, it can be determined that there is an abnormality.

In addition, as shown in FIG. 2(b), Wc<Wb,
Even if it is determined that the received signal is abnormal, the alarm 1o may be configured to notify that the presence of an object has been detected, and at the same time display a warning that there is a possibility of malfunction.

[Effects of the Invention] According to the invention according to claim 1, in the ultrasonic pulse type object detector that detects an object using a received wave signal within a predetermined wave receiving gate, the received wave signal is detected within the wave receiving gate. Since it is equipped with a wave reception ratio calculation unit that calculates the proportion of time in which This has the effect of being able to be judged.

In the invention according to claim 2, when the reception ratio calculated by the reception ratio calculation unit exceeds a preset reception ratio, the object detection operation is prohibited.
This has the effect of preventing false detections caused by urban noise, etc.

Note that if the object detection operation is not prohibited and only a warning display is displayed, there is an advantage that the user can be informed of the possibility of false detection due to city noise or the like.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the circuit configuration of an embodiment of the present invention, and FIG. 2 is an explanatory diagram of the same operation. 1 is an ultrasonic transducer, 2 is a wave transmitting circuit, 3 is a control unit, 4 is a wave receiving circuit, 5 is a wave receiving gate setting unit, 6 is a wave receiving ratio calculation unit,
Reference numeral 7 denotes a reception ratio comparison section, 8 a distance calculation section, 9 an alarm drive section, and 10 an alarm.

Claims (2)

[Claims] (1) Ultrasonic pulse type object detector that transmits ultrasonic pulses, receives reflected waves from objects, and detects objects by receiving signals within a receiving gate corresponding to a predetermined detection distance range. An ultrasonic pulse type object detector characterized in that the ultrasonic pulse type object detector is equipped with a wave reception ratio calculating section that calculates a time ratio in which a wave reception signal is included in the wave reception gate. (2) The ultrasonic pulse type object according to claim 1, further comprising means for prohibiting an object detection operation when the reception ratio calculated by the reception ratio calculation unit exceeds a predetermined value. Detector.