JPS6270781A - Ultrasonic matter detector - Google Patents

Abstract

PURPOSE:To prevent the erroneous information of detection output due to acoustic or electric noises, by providing a means measuring the distances from a plurality of matters and a second receiving gate. CONSTITUTION:When a plurality of signals are inputted at first during a receiving gate period TG, the distance up to reflective matter when it is assumed that said signals are reflected wave signals is calculated on the basis of the time delay from a transmitting pulse with respect to said signals. Then, the distance is calculated at a place where a preset threshold value Vth is exceeded. On the basis of thus calculated respective distances, a second receiving gage is opened during periods TG21, TG21. Next, at the second time, it is investigated whether the signal is present during the periods TG21, TG21 and, when no signal is present during all of the periods TG21, a limit such that the signal is present during the period TG21 is canceled and all of the signals during the original period TG are investigated. When the signal is present at least during one period TG21, the distance is again calculated and a new second receiving gate period TG22 is set on the basis of the calculated value. Further, at the third time, it is investigated whether the signal is present during the period TG22 reset in the previous time and, if there is a reflected signal S3, a detection output signal is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an ultrasonic object detector whose purpose is to obtain information about the presence of an object, or its moving direction and distance.

[Background technology]

In a pulse-type ultrasonic object detector that detects objects using ultrasonic pulses, the signal obtained as the output of the reception gate includes not only the signal of the reflected wave from the object of the transmitted pulse, but also acoustic noise. :1. (external noise), electrical noise, etc. In order to prevent false alarms in the detection output due to these noises, the signal of the reception gate output was checked multiple times, and the detection output was output when a signal (not necessarily a reflected wave) was present every time. A continuous detection method is conventionally provided. However, in such a conventional example, whether it is a reflected wave or noise, if it exists in the receiving gate, it is regarded as a received signal.9For example, in the case of the example shown in FIG. (Three times in the example) The continuous detection method was sometimes useless. That is, the operation of the conventional example shown in Fig. 1 is as follows: (a) (b) (c) K
As shown, the first to third ultrasonic pulses P
In the case where the configuration is such that Ul-pυ3 is transmitted and the receiving gate is opened for a period π following this transmission, 9
As shown, Nl, N2. When the noise outputs N3 are obtained, these noise outputs N, , N2 . N3
Since all of the signals are within the receiving gate period TG, a receiving gate output is obtained every time, and the third receiving gate output causes a problem in that a detection output as a false alarm is output.

Another conventional example is a means for measuring the distance from an object once a reflected wave signal from an object is detected in the reception gate, and a preset distance from the distance measured by this measuring means. A second receiving gate is provided that allows only reflected wave signals from objects within the range to pass through, and this second receiving gate is provided.
A system has been proposed in which only the reflected wave signal input through the receiving gate of the object is confirmed as the reflected wave signal from an object. However, in such conventional cases.

In FIG. 4(a), the period T for each of the transmission pulses of PU1 to PU4. The receiving gate is opened for the period T.

Noise NI+ N2 and reflected wave signal 5 inside! rSt=
84 is detected, the operation of the detector circuit is as shown in FIG. 21 as shown in the same figure (b), the reflected wave signal '8Sz at this time could not be detected, and the period T of the second wave receiving gate was resumed. 2□ is formed as shown in the same figure (C). Thus, in the case of (C) in the same figure, the reflected wave signal 'jl)Ss can be detected, but on the other hand, in this case, due to the noise N2 input at the same time, the second received wave as shown in (d) of the same figure can be detected. Gate period T. 2. was set, and the reflected wave signal S4 could not be detected again, and although it was possible to prevent false alarms from occurring due to the N2CD input, it was also possible to obtain a detection output from the actual reflected wave signals 8 St to S4. There was a problem in which the report was not made and the information was misreported.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an ultrasonic object detector that prevents false alarms and false alarms in detection output due to acoustic noise, electrical noise, and the like.

[Disclosure of the invention]

The present invention will be explained based on the following examples. FIG. 2 is a gate tie three-way diagram according to an embodiment of the present invention. In the following, a three-time continuous detection method will be explained. It can also be applied to a continuous detection method.

In FIG. 2, as shown in FIG. 2(a), the reception gate period T is first applied. Multiple signals (transmission pulses PU1 to PU4)
It is not limited to only the reflected wave signals S and -Ss,
In the figure, +Nl is the noise and 5-53 is the reflected wave signal. ) comes in, the distance to the reflecting object is determined for each signal 5 + signal based on the time delay from the transmitted pulse, assuming that these signals are reflected wave signals. Therefore, in this embodiment, the distance is calculated when the preset threshold value vth is exceeded. Even if the incoming signal is noise N, the distance -
The distance is calculated, but its value is meaningless. Based on the respective distances determined as described above, the second reception gate is set to open during the period TG211 to TG21. Next, for the second time, as shown in FIG. 6(b), first, the period T of each 20th reception gate set last time. 21. To2. If there is no signal within all the 20th receiving gate period "O reception gate period T.

Check everything inside. In other words, this is the third consecutive detection method. On the other hand, at least one second reception gate period T. If there is a signal within 2
reception gate period T. Set 22. Now, in this example, there is a reflected wave signal 8S3, so the third time (C) in the same figure
The 20th receiving gate period T that was reset last time. 22
It is checked whether a signal exists within the object, and since a signal is present, a detection output signal is output for the first time as a signal indicating the presence of an object.

The setting of the receiving gate @2 may be to examine a range of a certain distance W on both sides centering on the distance 1ild determined as shown in Fig. 3(a), but it is possible to For large objects, make the gate width wider on the near side
3(b) in which the non-approaching side is narrowed as Y, and these two examples are not limited.

Various gate types can be considered depending on the application.

Thus, in the embodiments of the present invention, (a) ~ of Figure 4 (0)
As shown in (d), the same noise N as in (a) of the same figure,
,N.

, even when the reflected wave signal Sl""S4 enters.

Same receiving gate period T. Even if a plurality of signals are detected during the period, the second reception gate period T is set for each signal. , 1~To
To set 2□? 11 In fact, it is possible to detect the repetition of the reflected wave signals M to S4 and turn on the detection output from the time point shown in FIG.

FIG. 5 is a block diagram showing an example of a circuit configuration for realizing the above embodiment, in which a transmission pulse created by a transmission pulse generation section [1] is converted into an ultrasonic wave by an ultrasonic transducer (2). , sent out into space. At the same time, the above-mentioned transmission pulse generation signal is sent as a time base i$ signal to the reception gate generation section (3), the second reception gate generation section (4), and the arithmetic circuit section (6)K. On the other hand, the ultrasonic pulse sent into space is reflected by an object and sent to the ultrasonic transducer (2).
The received signal is amplified and detected by the received signal amplification and detection circuit (6), and is input to the arithmetic circuit section (6). Furthermore, the outputs of the reception gate creation section (3) and the second reception gate creation section (4) are also input to the arithmetic circuit section (6). The reception gate creation section (3) creates a reception gate for the above-mentioned period TGO, and the second reception gate creation section (4) creates the reception gate for the above-mentioned period T. 2
The arithmetic circuit section (5) inputs these gate signals together with the output of the received signal amplification/detection circuit (6) to create the gates as shown in Fig. 3 mentioned above. The arithmetic operation of the creation process is performed, and the arithmetic circuit unit (5) outputs a detection output signal, and the memory circuit unit (7) stores the results.

〔Effect of the invention〕

Since the present invention is configured as described above, it is possible not only to extract only signals within the expected movement range of the object to be detected as a reflected wave signal from the object, but also to eliminate noise. Even when the reflected wave signals are combined and have a large depth, it is possible to reliably detect the repetition of the reflected wave signals, greatly improving the accuracy of signal detection and greatly reducing the risk of false alarms or missed alarms due to noise, etc. It has the effect that it can.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the operation of the conventional example, Fig. 2 is an explanatory diagram of the operation of an embodiment of the present invention, and Fig. 3 (a) (b) td.
Figures 4(a) and 4(b) are diagrams for explaining the comparative operation of the conventional example and the embodiment of the present invention, respectively, and Figure 5 is a diagram of an embodiment of the present invention. It is a block diagram. Agent Patent Attorney Ishi 1) Chief Figure 1 Figure 2 Figure 3 d: Figure 5\=

Claims (1)

[Claims] (1) Transmission of ultrasonic pulses and detection of reflected wave signals via a reception gate are repeated a preset number of times, and a detection output is output when a reflected wave signal is present all of those times. In a conventional ultrasonic object detector, once a plurality of signals are detected within the receiving gate, a means for measuring the distance to each reflecting object assuming that each signal is a reflected wave signal, and a means for measuring the distance to each reflecting object, and A second wave receiving gate is provided that allows only reflected wave signals to pass from objects within a preset distance range from the respective distances measured by the means, and reflection signals input through the second wave receiving gate are provided. An ultrasonic object detector characterized in that only a wave signal is confirmed as a reflected wave signal from an object.