JPH05675B2 - - Google Patents

Description

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

[Background Art] Generally, when the noise received by an ultrasonic detector is an ultrasonic pulse emitted by a rotating machine such as an engine, the period is relatively close to the operating cycle of the ultrasonic detector, so There was a problem that malfunctions were likely to occur. 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. 3a shows a tone burst noise waveform generated from a rotating machine. This noise N has a pulse width of τ ₂ and is generated at a repetition period of τ ₁ . Figure 3b shows the operation timing of the ultrasonic detector when _there is no noise N. , and monitors the noise N during a period T ₂ (referred to as a noise monitoring period) from after the reception period T ₁ has elapsed until before the next transmission pulse P is transmitted. Note that the period from when the transmission pulse P is transmitted to when the reception interval T ₂ has elapsed is a period T ₃ (referred to as a detection processing period) during which the ultrasonic detector performs object detection processing. In this way, when the noise N does not exist, as shown in FIG. 3b, the detection processing during the detection processing period _T3 and the noise monitoring during the noise monitoring period _T2 are repeated.
Note that during the above 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. Therefore, this noise monitoring period T ₂
Therefore, it can be determined that the signal received by N 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, and the time when the next noise N will arrive is predicted. , determine a time point A at the bottom of FIG. 3c at which the detection process is possible. Then, the object that was normally detected in the operation cycle shown in figure b,
As shown in figure c, the time to transmit the next transmission pulse P is delayed until time A, that is, the noise monitoring period.
Object detection processing was delayed until immediately after the first noise N after T ₂ to prevent malfunctions due to noise N.

By the way, most of the ultrasonic noise N in urban areas is not rectangular wave-like as shown in Figure 3a;
As shown in FIG. 2a, it is composed of a plurality of rectangular tone burst waves, and furthermore, whisker-like pulses called glitches are often accompanied before and after the plurality of tone burst waves. For such noise N, it is difficult to appropriately judge the repetition period τ ₁ and pulse width τ ₂ of this noise N, and in the conventional ultrasonic detector described above, for example, the repetition period τ ₁ and pulse width τ 2 are difficult to judge appropriately. We judge τ ₂ to be a ₁ and a ₂ in Figure 2. In this case, the repetition period τ ₁ of the noise N becomes small, and object detection processing cannot be performed until the noise N disappears. As described above, the conventional ultrasonic detector has the disadvantage that it is difficult to determine an appropriate time point A at which detection processing is possible.

[Object of the Invention] The present invention has been made in view of the above-mentioned points, and its object is to appropriately control the pulse width even in noise composed of a plurality of noise pulses such as urban noise. Another object of the present invention is to provide an ultrasonic detector that can measure the repetition period and determine an appropriate next detection processing period without being affected by this noise.

[Disclosure of the Invention] (Structure) The present invention provides 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. , a noise monitoring period in which noise is monitored during the detection processing period in which object detection processing is performed from the time of transmitting the ultrasonic pulse to the end of the reception period in which the reflected wave from the object existing in the detection area is received. and a noise pulse detection means for detecting a noise pulse during this noise monitoring period, and when the next noise pulse is detected within a predetermined short time by this noise pulse detection means, the previous noise pulse and the next noise are detected. Pulse width measuring means that determines that a pulse is one noise pulse, and measures the pulse width as the time from the generation point of the previous noise pulse to the point of disappearance of the next noise pulse, as the pulse width of the noise pulse; a repetition period measuring means for measuring the repetition period of the noise pulses when a plurality of noise pulses determined to be one noise pulse are detected within the noise monitoring period, and based on the measurement results of the pulse width and repetition period measuring means. The system is equipped with a prediction determining means that predicts the generation point of the next arriving noise pulse and determines the next detection processing period based on the prediction result. Even in the case of noise composed of It is determined that this is the case, and the time from the generation point of the previous noise pulse to the point of disappearance of the next noise pulse is measured as the pulse width of the above noise pulse, and the pulse width is appropriately measured, and the period is repeatedly measured. A means is capable of measuring the repetition period of this noise pulse, and a prediction determining means determines an appropriate next detection processing period free from the influence of this noise based on the measurement results of both of the measuring means. It was made so that it could be done.

(Example) An example of the present invention is shown in FIGS. 1 and 2.
As shown in FIG. 1, the ultrasonic detector of this embodiment includes 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, a wave receiving circuit 3 that receives reflected wave pulses from an object, an amplifying and detecting circuit 4 that amplifies and detects the output of the wave receiving circuit 3, and this amplifying and detecting circuit 4.
It consists of an object detection circuit 5 that detects whether an object is present in the detection area based on the output, and a display 6 that displays that an object has been detected by the object detection circuit 5. In this embodiment, the presence of an object is detected from the reflected wave received during the reception period _T1 shown in FIG. The presence of an object is detected by calculating the distance to the object based on the time delay.

The above configuration is a circuit configuration related to object detection processing. Next, a circuit configuration for preventing malfunctions due to noise will be explained. In this embodiment as well, there is a detection processing period T in which object detection processing is performed from the time of transmitting the transmission pulse P to the end of the wave reception period _T1 in which the reflected wave from an object existing in the detection area is received. ₃ , there is a noise monitoring period T ₂ for monitoring noise, and during this noise monitoring period T ₂ the receiving circuit 3
A noise detection circuit 7 is provided as a noise pulse detection means for detecting noise pulses from the output of the
A signal processing circuit 8 is provided which performs signal processing based on the output of the noise detection circuit 7 to control the wave transmitting circuit 2 and the object detection circuit 5 so that detection processing is performed in an appropriate period unaffected by noise. . The noise detection circuit 7, when the noise pulse N is detected,
It is designed to detect whether the next noise pulse occurs within a predetermined short time from the time when this noise pulse N disappears. It is designed so that it can be detected that 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 extinction of _the next noise pulse;
a repetition period measuring means for measuring the repetition period of the noise pulses when a plurality of noise pulses determined to be noise pulses are detected; and a repetition period measuring means for measuring the repetition period of the noise pulses determined as noise pulses; It is comprised of a prediction determining means that predicts the time of occurrence and determines the next detection processing period based on the prediction result.

The malfunction caused by noise and the prevention function of this embodiment will be explained below with reference to FIG. 2. Note that the operation when the noise pulse N has a rectangular waveform shown in FIG. 3a is the same as that described in the conventional example, and therefore the description thereof will be omitted. Suppose that noise composed of a plurality of noise pulses is generated, such as the urban noise shown in FIG. 2a. 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 _T2 , 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, when the next noise pulse is detected by the noise detection circuit 7 within a predetermined short time,
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 point of the previous noise pulse to the point of extinction of the next noise pulse is calculated as the pulse of the above noise pulse. Measure the pulse width as width. In the case of the noise shown in Figure 2a, since noise pulses are generated one after another within a predetermined short time, the pulse width when the above-mentioned plurality of noise pulses are considered as one noise pulse is the same as that of the next noise pulse. Each time a 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, only when the next noise pulse is no longer detected by the noise detection circuit 7 within a predetermined short time, the pulse width, which is the output of the pulse width measuring means, is output to the prediction determining means. The pulse width measured by the pulse width measuring means of this noise is τ ₃ shown in FIG. 2c.
becomes. Then, when the next noise similar to that described above is received by the wave receiving circuit 3 within the noise monitoring period T ₂ , the repetition period measuring means measures the repetition period τ ₄ of this noise pulse. Then, based on the measurement results of both of the measuring means, the prediction determining means determines an appropriate next detection processing period free from the influence of 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 determined to be one noise, so unlike the conventional method, The detection processing period is not determined by the pulse width a ₁ and repetition period a ₂ of the glitch and noise pulse, which makes it possible to reliably prevent malfunctions due to noise and improve the reliability of the ultrasonic detector. can be improved.

[Effects of the Invention] As described above, the present invention provides 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. Noise monitoring that monitors noise during the detection processing period in which object detection processing is performed from the time of transmitting the ultrasonic pulse to the end of the reception period in which the reflected wave from the object existing in the detection area is received. Set a period,
Noise pulse detection means detects a noise pulse during this noise monitoring period, and when the next noise pulse is detected within a predetermined short time by this noise pulse detection means, the previous noise pulse and the next noise pulse are 1
a pulse width measuring means that determines that the pulse is a noise pulse, and measures the pulse width of the noise pulse as the time from the time when the previous noise pulse is generated until the time when the next noise pulse disappears; and the noise monitoring period. a repetition period measuring means for measuring the repetition period of the noise pulses when a plurality of noise pulses determined to be one noise pulse are detected within the same period; The device is equipped with a prediction determining means that predicts the time point at which a noise pulse will occur and determines the next detection processing period based on the prediction result. Also, when the next noise pulse is detected within a predetermined short time by the noise pulse detection means, the pulse width measurement means determines that the previous noise pulse and the next noise pulse are one noise pulse. , the time from the generation point of the previous noise pulse to the point of disappearance of the next noise pulse is measured as the pulse width of the noise pulse, and the pulse width is appropriately measured, and the pulse width is measured appropriately, and the repetition period measuring means is used to measure the pulse width. The repetition period of this noise pulse can be measured, and therefore, based on the measurement results of both of the measurement means, the prediction and determination means can determine an appropriate next detection processing period that is free from the influence of this noise. Therefore, the effect of preventing malfunctions due to noise is enhanced.

[Brief explanation of the drawing]

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 a conventional example. 7 is a noise detection circuit, 8 is a signal processing circuit, P is a transmission pulse, τ ₁ is a repetition period, τ ₂ is a pulse width, T ₁
is the wave reception period, T ₂ is the noise monitoring period, and T ₃ is the detection processing period.

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, the detection area starts from the time the ultrasonic pulse is sent. A noise monitoring period for monitoring noise is provided during the detection processing period in which object detection processing is performed up to the end of the reception period in which reflected waves from objects existing in the area are received, and noise pulses are transmitted during this noise monitoring period. When the noise pulse detection means detects the next noise pulse within a predetermined short time, it is determined 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 determining that there is one noise pulse within the noise monitoring period. a repetition period measuring means for measuring the repetition period of the noise pulses when a plurality of noise pulses are detected; and a repetition period measuring means for measuring the repetition period of the noise pulses; What is claimed is: 1. An ultrasonic detector comprising prediction determining means for predicting and determining the next detection processing period based on the prediction result.