JPH0327871B2 - - Google Patents

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 is not only the signal of the reflected wave from the object of the transmitted pulse, but also the acoustic signal. There is noise (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 is checked multiple times, and the detection output is output when a signal (not necessarily a reflected wave) is present every time. Detection methods have been conventionally provided. However, in such a conventional example, whether it is a reflected wave or noise, if it exists within the reception gate, it is regarded as a reception signal. In the example, the continuous detection method was not useful (three times). That is, in the operation of the conventional example shown in FIG. 1, the first
In the case where the configuration is such that the first to third ultrasonic pulses Pu ₁ to _{Pu 3} are sent out and the reception gate is opened for a period _TG following this sending out, N ₁ , N as shown in the figure. When the noise outputs of ₂ and N ₃ are obtained, these noise outputs N ₁ , N ₂ , and N ₃ are all within the receiving gate period _TG , so the receiving gate output is obtained every time, and 3 There was a problem in that the detection output was output as a false alarm due to the second reception gate output.

[Purpose of the invention]

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

[Disclosure of the invention]

The present invention will be explained based on the following examples. FIG. 2 is a gate timing diagram according to an embodiment of the present invention, and the explanation below will be based on a three-time continuous detection method, but without losing generality, this is a general multiple-time continuous detection method other than three times. It can also be applied to

In Fig. 2, if a signal comes in during the first reception gate period T _G as shown in Fig. 2a,
The distance to the object is determined based on the time delay of the signal from the transmitted pulse Pu ₁ . In this example, the distance is calculated starting from the left end of the first receiving gate period _T The value has no meaning.)
Based on the determined distance, the second reception gate is set to open during period T _G21 . Next, as shown in b of the same figure, for the second time, it is first checked whether the signal _N1 exists within the second receiving gate period T _G21 set previously, and in b of the same figure, there is no signal. However, if the signal _S1 is present in the second reception gate period _TG21 , the distance is determined again, and a new second reception gate period _TG22 is established based on the distance. On the other hand, if there is no signal in the second reception gate period T _G21 (the example shown), the second reception gate period T _G21
The first receiving gate period is removed.
Check everything in T _G. In other words, the process returns to the first detection of the three consecutive detection methods. Next, in c of the same figure, the second reception gate period set last time is
T _G22 is checked, and this time, since signal S ₂ exists within the reception gate period T _G22 , the distance is calculated, a new second reception gate period T _G23 is set, and the next reception is performed using this signal. It is checked whether the signal _S3 exists within the reception gate period _TG23 . In this example, since the signal _S3 exists within the reception gate period _TG23 , an object detection output signal indicating the presence of an object is output for the first time here. Similar processing may be performed thereafter. Here, the setting of the second receiving gate is the distance d determined as shown in Figure 3a.
It is conceivable to examine a fixed distance w on both sides with the center at the center, but especially for objects that approach the detector side, the width of the gate on the approaching side is widened as x, and the gate width on the non-approaching side is designated as y. A narrow gate as shown in FIG. 3b is also conceivable, and furthermore, it is not limited to these two examples, and various gate types can be considered depending on the application.

FIG. 4 is a block diagram showing an example of a circuit configuration for realizing the above embodiment, in which a transmission pulse generated by a transmission pulse generation section 1 is converted into an ultrasonic wave by an ultrasonic transducer 2 and sent out into space. Ru. At the same time, the above-described generation signal for the transmission pulse is sent as a time reference signal to the receiving gate generating section 3, the second receiving gate generating section 4, and the arithmetic circuit section 5. On the other hand, the ultrasonic pulse sent out into space is reflected by an object, received by the ultrasonic transducer 2, amplified and detected by the received signal amplification and detection circuit 6, and input to the arithmetic circuit section 5. 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 5 . The reception gate creation section 3 is operated during the above-mentioned period.
The second _wave reception gate creation unit 4 creates reception gates for the period T _G21 to _{T G23} , and the arithmetic circuit unit 5 receives these gate signals. It is input together with the output of the wave signal amplification/detection circuit 6 and performs the arithmetic operation of the gate creation process as shown in FIG. It is something to remember. Note that the positions of the second reception gate periods T _G21 to T _G23 within the first reception gate period T _G are set in a floating manner based on the detection time of the previous reflected wave signal. If noise is avoided by changing the transmission interval without dependence on the transmission interval of the sound wave pulse, false detection due to noise can be more reliably prevented.

〔Effect of the invention〕

As described above, each time a reflected wave signal is detected within the first reception gate period, the second reception gate period is set as a predetermined period based on the detection time. and a detection signal is output when a state in which a reflected wave signal is detected a predetermined number of times consecutively occurs within the second reception gate period set corresponding to the previous reflected wave signal. Therefore, by setting the second reception gate period as an expected period in which the next reflected wave signal is likely to be obtained based on the reflected wave signal detected during the first reception gate period, The reception gate period can be set to a relatively short period, and the chances of detecting noise are greatly reduced. Moreover, by obtaining a detection signal only when a reflected wave signal is detected a predetermined number of times in a row, the chance of false detection due to noise is reduced. By setting the subsequent reception gate period as a short period, there is an advantage that there is almost no possibility of false detection due to noise. In addition, since the second reception gate period is set for each reflected wave signal, even if the second reception gate period is set due to noise, the second reception gate period that has been set will be reflected during the reception gate period. If the wave signal is not detected, the second wave signal will be detected next time.
The reception gate period has been corrected, and object detection is delayed by only one time relative to the transmission of ultrasonic pulses, which has the effect of preventing false detection due to noise and almost no time delay until object detection. There is. Furthermore, since the second reception gate period is set in a floating manner within the first reception gate period with reference to the detection time of the previous reflected wave signal, the relative position between the detector and the object changes. This has the advantage that it can be used in a form that changes the transmission interval irregularly in order to further reduce the chance of falsely detecting noise. be.

[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 one embodiment of the present invention, and Figs. 3 a and b are explanations of mutually different examples of period setting of the second wave reception gate same as above. 4 are block diagrams of one embodiment of the present invention. 1 is a transmission pulse generation section, 2 is an ultrasonic transducer, 3 is a reception gate generation section, 4 is a second reception gate generation section, 5 is an arithmetic circuit diagram, 6 is a reception signal amplification and detection circuit, 7 is a memory circuit section, T _G is a first reception gate period, and T _G21 to _{T G23} are second reception gate periods.

Claims (1)

[Claims] 1 Transmits ultrasonic pulses intermittently and receives reflected waves from objects, and detects reflected wave signals detected within the first receiving gate period, which is a certain period after transmitting the ultrasonic pulses. In an ultrasonic object detector that outputs a detection signal indicating the presence of an object based on the detection signal, each time a reflected wave signal is detected within the first reception gate period, a second reception gate is set as a predetermined period based on the detection time. a second wave reception gate creation section that sets the wave gate period within the first wave reception gate period; and a second wave reception gate creation section that sets the wave gate period within the first wave reception gate period; An ultrasonic object detector comprising: an arithmetic circuit section that outputs a detection signal when a detected state occurs a predetermined number of times in succession.