JPH0627806B2 - Ultrasonic object detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention intermittently transmits a pulsed ultrasonic wave and receives a reflected wave from an object to detect the existence of the object and the distance to the object. The present invention relates to an ultrasonic object detector adapted to detect a.

[Prior Art] Conventionally, as an ultrasonic type object detection device of this type, pulsed ultrasonic waves are intermittently transmitted, and after the transmission, within a reception gate period set at a predetermined time interval. There is provided a device that detects an object in a detection area depending on whether a reflected wave from the object is accepted. This is because it is possible to determine whether an object exists in the detection area based on the presence of reflected waves, and the distance to the object can be determined by detecting the time delay between the wave transmission and the wave reception. It is a thing. This type of ultrasonic object detection device has a problem that malfunction occurs when noise of a frequency close to that of the transmitted ultrasonic wave is received. However, in order to prevent such malfunctions, the following measures are taken. That is, if the noise has periodicity, the repetition period and the interruption time are detected from the noise pattern, and the wave is transmitted at the time when it is predicted that the noise does not exist. In some cases, the next transmission is postponed until the noise stops.

However, with respect to the noise having the above periodicity, conventionally, it is predicted that a noise monitoring section is provided after the detection operation by receiving an ultrasonic wave transmission and that the noise does not exist immediately after the end of the noise monitoring section. The wave is being transmitted at a certain point. Therefore, under periodic noise, the transmission intervals are always the same or close.

Here, in an environment where another ultrasonic object detector with the same function is installed side by side, another ultrasonic object detector will generate a transmission with a constant transmission interval as described above under periodic noise. When you do
The ultrasonic pulse to be transmitted is judged to be periodic noise, and its own transmission is performed after a certain period of time from the end of the transmission of the other ultrasonic object detectors. There is a problem that the sound wave object detector hits the wave reception period, resulting in malfunction due to mutual interference.

[Problems to be Solved by the Invention] The present invention has been provided in view of the above-mentioned points, and other super-functions having an equivalent function can be provided by giving priority to arbitrary transmission even under periodic noise. An object of the present invention is to provide an ultrasonic object detector that does not malfunction due to mutual interference or the like with the acoustic object detector.

[Means for Solving the Problem] The present invention is an ultrasonic object detection device that intermittently transmits an ultrasonic pulse and receives a reflected wave from an object to detect the presence of the object or the distance to the object. In the container, a wave sending circuit that sends an ultrasonic pulse, a wave receiving circuit that receives a reflected wave from an object by the sent ultrasonic pulse, and a detection circuit that is provided after the wave sending and the wave receiving are provided. Noise detection circuit that detects noise in the noise monitoring section and measures the repetition period and interruption time of the received periodic noise, and stores the repetition period and interruption time output from this noise detection circuit And a means for randomly determining a transmission time point, and whether the determined transmission time point falls within a noise generation period predicted by the repetition period and the interruption time of the noise stored in the storage circuit. or not And the driving circuit at the time of transmitting the wave when it is determined to be no, and the driving circuit after a predetermined time from the end of the noise generation period when it is determined to be on. And a means for determining a reception period after a lapse of a certain time from the driving of the transmission circuit, and taking in a reception signal from the reception circuit to perform distance detection.

[Action]

According to the present invention, the noise detection circuit detects noise in the noise monitoring section provided after the detection operation by the transmission and reception of ultrasonic waves, and the repetition cycle of the received periodic noise. And the intermittent time is measured, and the measured repetition period and intermittent time are stored in the memory circuit, and the output of the noise detection circuit is received by the signal processing circuit and the data of the memory circuit is set to a predetermined transmission time as an arbitrary value. Therefore, when it is predicted that the periodic noise will arrive, the periodic noise is avoided and transmission and reception are performed.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. The present invention provides a noise monitoring section between a detection processing section including transmission and reception and a next detection processing section, and when a noise pulse is detected in the noise monitoring section, a noise pulse repetition period and The pulse width is measured and stored in a memory circuit, and at the time of wave transmission determined by a predetermined random value before wave transmission, from the data stored in the memory circuit, the receiving gate detects noise. When it is determined that they overlap,
It is characterized in that the transmission / reception gate is opened at a time close to the transmission time.

FIG. 1 shows a block diagram of this device. An ultrasonic transducer 1 for both transmission and reception is driven by a transmission circuit 2 to intermittently transmit ultrasonic pulses and receive reflected wave pulses from an object. It is something that surfs. The received signal is amplified by the receiving circuit 3, further amplified and detected by the amplification detecting circuit 4, and input to the object detecting circuit 5. As shown in FIG. 2 (b), the object detection circuit 5 detects the presence of an object when a signal is received in the receiving section T ₁ , and detects the presence of the received pulse from the transmission pulse P. The distance to the object is calculated from the time delay, and the presence or distance of the object is displayed on the display unit 6.

The output of the wave receiving circuit 3 is also input to the noise detecting circuit 7, and when the noise detecting circuit 7 receives a signal within the noise monitoring section T _{2 as} shown in FIG. 2 (b). , This is detected as noise. When two noise pulses N ₁ and N ₂ are detected in the noise monitoring section T ₂ , the noise detection circuit 7 measures the noise repetition period τ ₁ and its interruption time, that is, the pulse width τ _2. The measured repetition period τ ₁ and the pulse width τ ₂ are stored in the storage circuit 9.

The signal processing circuit 8 does not make the interval from the previous transmission to the current transmission constant, but uses an arbitrary value obtained by the random number generation function provided in the circuit as the transmission interval, The function to determine the time after the transmission interval is maintained as the transmission time, and whether the determined transmission time falls within the noise generation period predicted by the noise repetition period and the interruption time stored in the memory circuit. A function of determining whether or not the function is to drive the wave transmitting circuit at the time of wave transmission when the function is determined to be no, and a wave transmitting circuit after a predetermined time from the end of the noise generation period when it is determined to enter. Of the noise detection circuit 7 and the function of driving the wave transmission circuit and detecting the distance by receiving the reception signal from the reception circuit by setting the reception period after a certain period of time from the driving of the transmission circuit. Received stored data from the storage circuit 9 Possible time A detection process close to a point
₁ , that is, when the periodic noise is predicted to arrive, the time point A ₁ is determined based on the random value for transmitting and receiving while avoiding the periodic noise, and the time point A ₁ is transmitted based on the result. The wave circuit 2 is controlled. Incidentally, T ₃ is a detection processing section.

FIG. 2 shows a time chart of the present invention, and FIG. 3 shows a time chart of a conventional example. N is periodic noise,
B is a transmission pulse of another ultrasonic object detector having a function equivalent to that of this apparatus. As can be seen from this time chart, in the case of FIG. 3, in order to carry the transmission pulse P at the time point A immediately after the end of the noise monitoring section T ₂ , it was transmitted from another ultrasonic object detector. The transmission pulse B is also periodically transmitted at the same point in time, and this transmission pulse B exists within the receiving section T ₁ , causing mutual interference and the like. However, in the case of the present invention, as shown in FIG. 2, since the transmission pulses are random with respect to each other, the transmission pulse B from another ultrasonic object detector may once enter the receiving gate. But next time I will not enter. In addition, these ultrasonic object detectors
Normally, the so-called “ _n- continuous detection method” that outputs a detection output only when the received wave is detected n times consecutively is adopted, so that malfunction can be prevented.

[Advantages of the Invention] As described above, the present invention is an ultrasonic object detection system that intermittently transmits ultrasonic pulses and receives reflected waves from an object to detect the presence of the object or the distance to the object. In the bowl,
A noise detection circuit that detects noise in a noise monitoring section provided after a detection operation by ultrasonic wave transmission and reception and that measures a repetition period and an interruption time of the received periodic noise and And a memory circuit for storing the repetition period and the interruption time output from the noise detection circuit, and means for randomly determining the transmission time point, and noise for which the determined transmission time point is stored in the storage circuit. Means for deciding whether or not to enter the noise generation period predicted by the repetition cycle and the interruption time, and if it is determined to be no, the wave transmission circuit is driven at the time of wave transmission, and it is judged to enter. In this case, the means for driving the wave transmission circuit after a lapse of a predetermined time from the end of the noise generation period, and the wave reception signal from the wave reception circuit by setting the wave reception period after a fixed time from the driving of the wave transmission circuit are detected. Hand to do Since it is equipped with a signal processing circuit consisting of and, noise is detected and received in the noise monitoring section provided after the detection operation by ultrasonic wave transmission and reception by the noise detection circuit. The repetition period and the interruption time of periodic noise are measured, the measured repetition period and the interruption time are stored in the memory circuit, and the output of the noise detection circuit is received by the signal processing circuit, and the value is predetermined as an arbitrary value. When it is predicted from the data of the memory circuit that the periodic noise arrives at the transmission time, it is possible to avoid the periodic noise and perform transmission and reception. Therefore, there is an effect that malfunction due to mutual interference with other ultrasonic object detectors having the same function is eliminated.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a time chart of the above, and FIG. 3 is a time chart of a conventional example. Reference numeral 7 is a noise detection circuit, 8 is a signal processing circuit, and 9 is a storage circuit.

Claims (1)

[Claims] 1. An ultrasonic type object detector for intermittently transmitting an ultrasonic wave pulse and receiving a reflected wave from the object to detect the presence of the object or the distance to the object. A wave transmission circuit that performs a wave, and a wave reception circuit that receives a reflected wave that is returned by the transmitted ultrasonic pulse reflected by an object,
A noise detection circuit that detects noise in a noise monitoring section provided after a detection operation based on transmission and reception and also measures the repetition period and duration of the received periodic noise, and the noise detection circuit. A storage circuit that stores the repetition period and the duration output from the detection circuit is provided, and means for randomly determining the transmission time point and the repetition period of the noise in which the determined transmission time point is stored in the storage circuit And a means for judging whether or not to enter the noise generation period predicted by the duration, and if it is judged to be no, drive the wave transmission circuit at the time of wave transmission, and if it is judged to enter Is an ultrasonic object detector characterized by comprising a signal processing circuit comprising means for driving a wave transmission circuit after a lapse of a predetermined time from the end of the noise generation period.