JPS63256878A - Ultrasonic detector - Google Patents

Abstract

PURPOSE:To improve preventive effect to malfunction due to noise by detecting a noise width and a noise period and determining a proper ultrasonic wave detection processing period. CONSTITUTION:When a noise detecting circuit 7 detects a noise pulse passed through a receiving circuit 3, the circuit 7 detects whether or not a next noise pulse is generated within a specific short period after said noise pulse is ceased and a signal processing circuit 8 decides this noise pulse as one noise pulse when the next pulse is detected within the specific time. Then the noise pulse width is measured, the repetitive synchronism of the noise pulse is measured, and the detection processing period is estimated and determined according to the measurement result. The ultrasonic wave detection processing period of a body detecting circuit 5 is controlled properly according to the determination result and the preventive effect to malfunction due to the noise at a noise place such as a city is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field 1] The present invention relates to an ultrasonic detector having a function of preventing malfunctions caused by noise.

[Background Art] In general, when the noise received by an ultrasonic detector is an ultrasonic pulse emitted by a rotating machine, the period is relatively close to the operating cycle of the ultrasonic detector,
There is a problem in that malfunctions are likely to occur due to noise. Therefore, by taking advantage of the periodicity of such noise and measuring its repetition period and duration (pulse width) from the detected noise, it is possible to predict the next point in time when there will be no noise, and to send data at that point. A method has been proposed for detecting objects by outputting wave pulses.

FIG. 3 shows a conventional method for preventing malfunctions caused by periodic noise. FIG. 3(a) shows a tone burst noise waveform generated from a rotating machine. The pulse width of this noise N is τ2, and it is generated at a repetition period τ. Figure 3 (
b) shows the operation timing of the ultrasonic detector when there is no noise N, and during a predetermined period T after transmitting the transmitting pulse P (hereinafter referred to as the receiving period), the reflection from the object is detected. The pulse is received, and the noise N is monitored during a period T2 (referred to as a noise monitoring period) from after the reception period T has elapsed until before the next transmission pulse P is transmitted. Note that the period from when the transmission pulse P is transmitted until the reception period T2 has elapsed is a period T during which the ultrasonic detector performs object detection processing (referred to as a detection processing period).

In this way, when there is no noise N,
), the detection processing during the detection processing period T3 and the noise monitoring during the noise monitoring period T2 are repeatedly performed. In addition,
During the noise monitoring period T2, the reflected wave from the object is outside the detection area, and there is no possibility that the reflected wave from the object will be received by the ultrasonic detector due to attenuation in the air.
It can be determined that the signal received during this noise monitoring period T2 is noise N. If two or more noises N are detected during this noise monitoring period T2, the repetition period τ1 and pulse width τ2 of the noise N are measured, the time when the next noise N arrives is predicted, and the third noise N is detected. A time point A when the detection process is possible shown in FIG. 1 is determined. Then, although the object is normally detected at the operating cycle shown in Fig. 3(b), the time point at which the next transmission pulse P is transmitted is delayed until the point in time as shown in Fig. 2(e), that is, Object detection processing is delayed until immediately after the first noise N after the noise monitoring period T2 to prevent malfunctions caused by the noise N.

By the way, most of the ultrasonic noise N in urban areas is shown in Figure 3 (
It is not a rectangular wave shape as shown in a), but a
), it is composed of a plurality of rectangular tone burst waves, and furthermore, it is often accompanied by a rectangular pulse called a glitch before and after the plurality of tone burst waves.

For such noise N, it is difficult to appropriately judge the repetition period τ1 and pulse width τ2 of the noise N, and in the conventional ultrasonic detector described above, for example, the repetition period τ1 and pulse width τ2 are It is judged as a+taz in Figure 2. In this case, the repetition period τ of the noise N becomes small, and object detection processing cannot be performed until the noise N disappears. As described above, conventional ultrasonic detectors have the disadvantage that it is difficult to determine an appropriate time point at which detection processing is possible.

EObjective of the Invention 1 The present invention has been made in view of the above-mentioned points, and its object is to appropriately adjust the pulse width even in noise composed of a plurality of noise pulses such as urban noise. [Disclosure of the Invention] Configuration) The present invention is an ultrasonic detector that detects the presence of an object and the distance to the object by transmitting ultrasonic pulses intermittently and receiving reflected waves from an object. Noise is added to the gap between the detection processing period during which object detection processing is performed, from the time the ultrasonic pulse is transmitted to the reception period until the reflected wave from an object existing in the detection area is received, and the next detection processing period. A noise monitoring period is set to monitor, and when noise A/resca C detection d-4 is performed during this noise monitoring period, the force that causes the next noise pulse to occur within a predetermined short time from the time when this noise pulse disappears is determined. The noise pulse detection means detects whether the noise is within a predetermined short time (secondary noise) (
When a pulse is detected, it is assumed that the previous noise pulse and the next noise pulse are 12Il/l less, and the period from the generation of the previous noise pulse to the disappearance of the next noise pulse is (measure the pulse width as the A/res width of the pulse) (using the pulse width measuring means and the pulse width measuring means) (measure the repetition period of the noise pulse whose pulse width force is measured) a repetition period measuring means for measuring the pulse width and the repetition period measuring means, and predicting the generation point of the next noise pulse based on the measurement results of the pulse width and the repetition period measuring means, and determining the next detection processing period based on the prediction result. If the noise pulse detecting means detects the next noise pulse within a predetermined short time even in noise composed of a plurality of noise pulses such as noise in an urban area, The pulse width measuring means determines that the previous noise pulse and the next noise pulse are one noise pulse, and the time from the generation of the previous noise pulse to the disappearance of the next noise pulse is calculated as the pulse of the i-sound pulse. This pulse width is measured as the width to appropriately measure the pulse width, and the repetition period of this noise pulse can be measured by a repetition period measuring means, and prediction is made based on the measurement results of both of the above measuring means. The determining means is configured to be able to determine an appropriate next detection processing period that is free from the influence of this noise.

(Example) An embodiment of the present invention is shown in FIGS. 1 and 2. FIG.

As shown in Fig. 1, the ultrasonic detector of this embodiment is equipped with an ultrasonic transducer 1 for both transmitting and receiving waves, and drives this ultrasonic transducer 1 to intermittently transmit ultrasonic pulses. A wave transmitting circuit 2 that detects a reflected wave pulse from an object, a wave receiving circuit 3 that receives reflected wave pulses from an object, an amplification and detection circuit 4 that amplifies and detects the output of the wave reception circuit 3, and an object that is detected in a detection area from the output of this amplification and detection circuit 4. It consists of an object detection circuit 5 that detects whether an object exists or not, and a display 6 that displays that the object detection circuit 5 detects an object. In this embodiment, the presence of an object is detected from the reflected wave received during the wave reception period T1 shown in FIG. 2 (1)). The presence of an object is detected by calculating the distance to the object based on the time delay from the time of the wave.

The above configuration is a circuit configuration related to object detection processing,
Next, a circuit configuration for preventing malfunctions caused by noise 1 will be explained. In this embodiment as well, the wave reception period T is from the time of transmission of the transmission pulse P until the wave reflected by an object existing in the detection area is received.

A noise monitoring period T2 is provided between the detection processing period T during which the object detection processing up to this point is performed and the next detection processing period T during which noise is monitored. Therefore, the output of the wave receiving circuit 3 is equipped with a noise detection circuit 7 as an m-blind pulse detection means that detects noise pulses during the noise monitoring period T2, and is not affected by noise based on the output of this noise detection circuit 7. A signal processing circuit 8 is provided which performs signal processing to control the wave transmitting circuit 2 and the object detection circuit 5 so that detection processing is performed in an appropriate period. The noise detection circuit 7 is configured to detect, when a noise pulse N is detected, whether or not the next noise pulse will occur within a predetermined short time after the noise pulse N disappears. For example, it is possible to detect urban noise including a plurality of noise pulses as shown in FIG. 2(a). Then, when the next noise pulse is detected by the noise detection circuit 7 within a predetermined short time, the signal processing circuit 8 determines that the previous noise pulse and the next noise pulse are one noise pulse. , a pulse width measuring means for measuring the pulse width of the noise pulse as the time from the generation point of the previous noise pulse to the point of disappearance of the next noise pulse; and the pulse width is measured by the pulse width measuring means. a repetition period measuring means for measuring the repetition period of the noise pulse that has been generated, and a time point at which the next coming noise pulse will be generated based on the measurement results of the pulse width and repetition period measuring means, and based on this prediction result. and a prediction determining means for determining the next detection processing period.

The function of this embodiment for preventing malfunctions due to noise will be explained below with reference to FIG. 2. Note that the operation when the noise pulse N is in the form of a rectangular wave shown in FIG. 3(a) is the same as that described in the conventional example, so a description thereof will be omitted. Assume that noise composed of a plurality of noise pulses is generated, such as the urban noise shown in FIG. 2(a). This noise pulse has gaps between pulses, and glitches before and after a plurality of pulses. When this noise pulse is received by the reception circuit 3 during the noise monitoring period 1m T 2 , the noise detection circuit 7 detects the noise. Then, within a predetermined short time after this noise is detected, the pulse width measuring means does not measure the pulse width, but stores the pulse width and generation time of this noise pulse. Then, the next noise pulse is detected by the noise detection circuit 7 within a predetermined short time.
When the pulse width measurement means determines that the previous noise pulse and the next noise pulse are one noise pulse, the time difference from the generation of the previous noise pulse to the point at which the next noise pulse disappears is determined by the pulse width measuring means. The pulse width is measured by assuming that the pulse width is the pulse width of the above-mentioned noise pulse. In the case of the noise shown in Figure 2 (,), since noise pulses are generated one after another within a predetermined short time, the pulse width when the above-mentioned plurality of noise pulses is considered as one noise pulse is as follows. Each time a noise pulse occurs, it is measured and stored.

Note that the time point at which the first noise pulse is generated is thus stored as long as the next noise pulse is detected by the noise detection circuit 7 within a predetermined short time, and from the time point at which the first noise pulse is generated, the above-mentioned steps are performed. The pulse width is measured as described above. Then, when the next noise pulse is no longer detected by the noise detection circuit 7 within a predetermined short time, the pulse width that is the output of the pulse width measuring means is output to the prediction determining means. The pulse width of this noise measured by the pulse width measuring means is τ shown in FIG. 2(e). Then, when the next noise similar to the above-described noise is received by the wave receiving circuit 3 within the noise monitoring period T2, the repetition period measuring means measures the repetition period τ of this noise pulse.

Then, based on the measurement results of both of the measuring means, the prediction determining means determines an appropriate dog detection processing period that is not affected by this noise. In this way, even if the noise is made up of multiple noise pulses and glitches, such as city noise, the multiple noise pulses are collectively judged to be one noise, so unlike the conventional method, The detection processing period is not determined by the pulse width a1 and repetition period a2 of the glitch and noise pulse (this makes it possible to reliably prevent malfunctions due to noise and sound, and improve the reliability of the ultrasonic detector. can be improved.

[Effect of the Invention 1] As described above, the present invention provides a detection method that performs object detection processing from the time of transmitting an ultrasonic pulse to the reception period from the time of transmitting an ultrasonic pulse to the time of receiving a reflected wave from an object 1 existing in a detection area. processing period and
A noise monitoring period for monitoring noise is provided between the next detection processing period, and when a noise pulse is detected during this noise monitoring period, the next noise is detected within a predetermined short time from the time when this noise pulse disappears. noise pulse detection means for detecting whether a pulse is generated; and when the next noise pulse is detected within a predetermined short time by the noise pulse detection means;
The previous noise pulse and the next noise pulse are determined to be one noise pulse, and the time from the point at which the previous noise pulse occurs to the point at which the next noise pulse disappears is set as the pulse width of the upper LJI sound pulse. a pulse width measuring means for measuring the width;
a repetition period measuring means for measuring the repetition period of the noise pulse whose pulse width is measured by the pulse width measuring means; and a repetition period measuring means for measuring the repetition period of the noise pulse whose pulse width is measured by the pulse width measuring means; Since it is equipped with a prediction determining means that predicts the time of occurrence and determines the next detection processing period based on the prediction result, it can be When the pulse detection means detects a dog noise pulse within a predetermined short time, the pulse width measurement means determines that the previous noise pulse and the next noise pulse are one noise pulse, and the previous noise pulse is determined to be one noise pulse. The time from the generation of the noise pulse to the disappearance of the next noise pulse is measured as the pulse width of the noise pulse, and the pulse width is measured appropriately.The repetition period measuring means is used to determine the repetition period of this noise pulse. Therefore, based on the measurement results of both of the measurement means mentioned above, the prediction and determination means can determine an appropriate next detection processing period that is free from the influence of this noise, thus preventing malfunctions due to noise. It has the effect of increasing the preventive effect.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the circuit configuration of an embodiment of the present invention, FIG. 2 is an explanatory diagram of the operation of the main parts of the same, and FIG. 3 is an explanatory diagram of the operation of the conventional example. 7 is a noise detection circuit, 8 is a signal processing circuit, P is a transmission pulse, τ1 is a repetition period, τ2 is a pulse width, T is a reception period, T2 is a noise monitoring period, and T is a detection processing period. Agent Patent Attorney Ishi 1) Chief 7 Figure 1 Figure 2

Claims (1)

[Claims] (1) In an ultrasonic detector that transmits ultrasonic pulses intermittently and receives reflected waves from an object to detect the presence of an object and the distance to the object, from the time the ultrasonic pulse is transmitted, A noise monitoring period for monitoring noise is provided between a detection processing period in which object detection processing is performed up to the wave reception period until receiving a reflected wave from an object existing in the detection region, and the next detection processing period, Noise pulse detection means for detecting whether or not a next noise pulse is generated within a predetermined short time from the time when this noise pulse disappears when a noise pulse is detected during this noise monitoring period, and this noise pulse detection means. When the next noise pulse is detected within a predetermined short time by the means, it is determined that the previous noise pulse and the next noise pulse are one noise pulse, and the next noise pulse is started from the point of occurrence of the previous noise pulse. pulse width measurement means for measuring the pulse width of the noise pulse, and a repetition period measurement means for measuring the repetition period of the noise pulse whose pulse width is measured by the pulse width measurement means. means, and prediction determining means for predicting the generation point of the next arriving noise pulse based on the measurement results of the pulse width and repetition period measuring means, and determining the next detection processing period based on the prediction results. An ultrasonic detector characterized by comprising: