JPH028773A - Ultrasonic body detector - Google Patents

Abstract

PURPOSE:To certainly detect a moving body while reducing the time necessary for detecting the body by making the time interval from one transmission to the next one variable according to the time ratio contained in a receiving gate and a monitor gate by a transmission pulse control part. CONSTITUTION:The time ratio of the receiving signal contained in a receiving gate is calculated by a receiving ratio calculation part 9 of an ultrasonic body detector and, corresponding to this calculated time ratio, the time interval from one transmission to the next transmission is controlled on the basis of the output of a transmission pulse control part 10 to be supplied to a transmission circuit 2 and a detected distance calculation part 4. The receiving signal 13 is always monitored by a monitor gate 15 other than the gate 14 and the output of a receiving circuit 3 is inputted to the calculation part 9 to calculate the ratio of the receiving signal 13 contained in the receiving gate 14 and the monitor gate 15 in the calculation part 9 and the time necessary for detecting a moving body is reduced and the body is certainly detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic object detector that detects objects using ultrasonic pulses.

[Conventional technology]

Generally, an ultrasonic pulse is transmitted and the reflected wave from an object is received as a received signal, and the existence of the object and the distance between the detector and the object are determined based on the presence or absence of the received signal and the time delay from the time of transmission. (hereinafter, these series of signal processing are collectively referred to as detection processing), the ultrasonic object detector repeats the detection processing at separately determined time intervals (one-time detection method). The repetition time interval of the detection process may be a fixed value, but may also be a random value.

In addition, in order to prevent false detections due to noise such as urban noise, if a detection signal indicating the presence of an object is not output during the repetition of the detection process, the received signal is continuously obtained for a preset number of times or more. A detection signal is output for the first time when the detection signal is detected, and if the detection signal is output, the detection signal is stopped only when the received signal has not been received for a preset number of times. It has been proposed (Japanese Patent Application Laid-open No. 107179/1982, 107180/1982).

[Problems to be Solved by the Invention] However, the above-described one-time detection method has problems in that it malfunctions due to urban noise and the like, and misses when the transmission interval is long.

Furthermore, even in the multiple continuous detection method to reduce malfunctions caused by urban noise, etc., it is extremely rare for noise to constantly enter the detector, and normally noise does not enter the detector for a short period of time. Therefore, even if there is no noise mixed in, if you always use the multiple continuous detection method described above, the detection time delay will become large. When detecting an object that moves out of the detection area again within a short period of time, the detection process cannot be performed the predetermined number of times set in the multiple continuous detection method within the detection area, and the detector will miss an alarm. There was a problem.

The present invention has been made in view of the above problems, and is capable of reliably detecting even moving objects. Furthermore, in the case of multiple continuous detection methods, ultrasonic waves can reduce the time required for object detection. The purpose is to provide an object detector.

[Means for Solving the Problems] The present invention transmits ultrasonic pulses, receives reflected waves from an object, and detects waves within a wave receiving gate that indicates a predetermined detection distance range set by a wave receiving gate setting section. In a pulse type ultrasonic object detector that detects an object using a received signal of It is characterized by comprising a wave transmission pulse control section that outputs a control signal that makes the time interval from one wave transmission to the next wave transmission variable, and further includes:
A monitoring gate that constantly monitors the received signal is provided in addition to the receiving gate, and the receiving ratio calculation section calculates the proportion of time that the received signal is included in the receiving gate and the monitoring gate, and The wave pulse control section is characterized in that the time interval from one wave transmission to the next wave transmission is made variable in accordance with the time ratio.

[Effect]

The ultrasonic object detector of the present invention transmits ultrasonic pulses intermittently, continuously receives reflected waves from the object,
The time ratio of the reception signal entering the preset reception gate to the entire reception gate is calculated, and the transmission time interval is varied based on this time ratio.

Further, the time ratio may be a ratio of the received signal to the entire time including the separately provided monitoring gate and the receiving gate.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on drawings showing one embodiment of the present invention.

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a time chart relating to the same. ■ is an ultrasonic transducer, which generates 1 ultrasonic pulse by the transmission signal from the wave transmission circuit described later.
The ultrasonic pulse reflected wave signal 12 is transmitted to a receiving circuit to be described later. Reference numeral 2 denotes a wave transmitting circuit, which sends a wave transmitting signal for driving the ultrasonic transducer 1. 3 is a receiving circuit which receives the ultrasonic pulse reflected wave signal 12 output from the ultrasonic transducer l.
is amplified and detected to obtain a received signal 13. Reference numeral 4 denotes a detection distance calculating section, which calculates the distance from the object to the ultrasonic detector by determining the time delay of the received signal obtained by the wave receiving circuit 3 from the ultrasonic pulse. Reference numeral 5 denotes a detection distance comparison unit that compares the distance to the object obtained by the detection distance calculation unit 4 with a preset detection distance range, and determines a predetermined condition (for example, the former is less than or equal to the latter). A detection signal is output only when the following conditions are satisfied. Reference numeral 5a denotes a receiving gate setting section, which sets the receiving gate 14 corresponding to the preset detection distance. When the detection signal is output from the detection distance comparison unit 5, the detection output control unit 6
This is to create a predetermined detection output signal. Reference numeral 7 denotes a detection output drive circuit, which sends a drive signal to a later-described alarm device based on the detection output signal. Reference numeral 8 denotes a notification device such as a lamp or a buzzer, which uses the drive signal to notify the outside of the presence of an object.

Reference numeral 9 denotes a reception ratio calculation unit, in which the reception signal obtained by the reception circuit 3 is sent to the reception gate 1 set in advance by the reception gate setting unit 5a.
This is to find out what percentage of time exists within the range of 4.

Reference numeral 10 denotes a transmission pulse control unit, which determines the time to transmit the next ultrasonic pulse based on the ratio of the reception signal obtained by the reception ratio calculation unit 9 based on a preset relationship (described later). Then, a control signal is sent to the wave transmitting circuit 2 so that the ultrasonic pulse is transmitted at the determined time.

Here, the preset relationship will be explained.

(2) Normally, if there is no object, the received signal 13 does not appear in the receiving gate 4, so the output of the received rate calculating section 9 has a received rate of O. In such a case, in order to extend the life of the ultrasonic transducer l and to prevent the influence of multiple reflections of the ultrasonic pulse reflected wave signal 12, it is recommended to keep the ultrasonic pulse transmission interval relatively long. good.

(2) If an object exists, a reception signal 13 appears in the reception gate 14 and the reception ratio is no longer 0. In this case, the transmission pulse control unit 10 shortens the transmission interval of the ultrasonic pulses. By doing so, when the continuous detection method is used multiple times, the time delay until object detection can be shortened. Thereby, objects moving within the detection distance range can be detected more reliably.

■ Actual waveform observations of the noise that exists in the city have confirmed that many have longer durations than ultrasonic pulses, and that the noise mixing time is relatively long compared to the transmission interval in the case of ■. Therefore, if such noise is mixed in,
The reception signal 13 is present in most of the reception gate 14, and the reception ratio is significantly increased compared to the case (2). In this case, the transmission pulse control unit 10 extends the transmission interval of ultrasonic pulses according to the reception ratio.

The relationship between the wave transmission interval and the wave reception ratio is determined by considering the conditions (1) to (4) above. Specifically, for example, it may be considered as a continuous function as shown in FIG. 3, or the reception ratio may be considered as divided into several ranges as shown in FIG. However, these are just examples and are not limited to these.

Next, the operation of this embodiment will be explained.

Ultrasonic pulses 11 are intermittently transmitted from the ultrasonic transducer 1 according to a drive signal from the wave transmitting circuit 2, and the reflected waves from the object are received by the ultrasonic transducer 1, resulting in an ultrasonic pulse reflected wave signal. 12 is output.

This ultrasonic pulse reflected wave signal 12 is amplified and detected by the wave receiving circuit 2, and a received wave signal 13 is obtained. The received signal 13 is compared with the ultrasonic pulse 11 in the detection distance calculation unit 4, and the time delay with the ultrasonic pulse 11 is calculated. This time-delayed signal is compared in the detection distance comparison section 5 with the reception gate 14 indicating the detection distance range stored in the reception gate setting section 5a, and it is determined whether the signal is within the range of the reception gate 14 or not. , outputs a detection signal. This detection signal is transmitted to the detection output control section 6,
It is notified to the outside via the detection output drive circuit 7 and the alarm 8.

On the other hand, the reception ratio calculating section 9 takes in the signals from the reception circuit 3 and the reception gate setting section 5a, and calculates the ratio of the reception signal 13 in the reception gate 14. The transmission pulse control unit 10 determines a transmission time interval based on this reception ratio and a preset relationship between the reception ratio and the transmission time interval, and sends a control signal indicating the transmission time to the transmission circuit 2. send. Based on this control signal, a drive signal is sent to the ultrasonic transducer 1 via the wave transmitting circuit 2, and the next ultrasonic pulse is transmitted.

According to this embodiment, when the received signal 13 is not within the receiving gate 14, the wave is transmitted relatively slowly, and when the received signal 13 is present within the receiving gate 14, it is transmitted quickly (transmitted). So,
In the case of the multiple continuous detection method, the time required for object detection is shortened, and detection is possible reliably without missing a signal, and when the reception ratio is large, it is determined that noise is being input and the transmission interval is lengthened. Therefore, malfunctions due to noise can be reduced.

Further, other embodiments of the present invention will be described.

FIG. 5 is a time chart for explaining another embodiment of the present invention. In this embodiment, the section for which the reception ratio calculation unit 9 calculates the reception ratio includes not only the reception gate 14 but also the monitoring gate 15 shown in FIG. The monitoring gate 5 occupies the period from the end of the wave reception gate 14 until the next wave transmission time, and the wave reception gate 4 and the monitoring gate 15 can take in the reception signal almost all the time. Conventionally, if noise did not accidentally enter the received wave signal 4, it could only be determined that there was no noise, but by providing the monitoring screen 5, it is possible to determine the proportion of time in which the received signal is always included. It is possible to determine the transmission interval of ultrasonic pulses appropriately.

〔Effect of the invention〕

According to the ultrasonic object detector of the present invention, an ultrasonic pulse is transmitted, a reflected wave from an object is received, and a detection range within the reception gate indicating a predetermined detection distance range set by the reception gate setting section is set. In a pulsed ultrasonic object detector that detects an object using a received wave signal, a reception ratio calculation unit that calculates a time ratio in which the reception signal is included in the reception gate; Equipped with a transmission pulse control unit that outputs a control signal that varies the time interval from one transmission to the next transmission,
Furthermore, a monitoring gate that constantly monitors the received signal is provided in addition to the receiving gate, and the receiving ratio calculation section calculates a time ratio in which the received signal is included in the receiving gate and the monitoring gate. In the transmission pulse control section, the time interval from one transmission to the next transmission is made variable according to the time ratio, thereby reducing the time required for object detection and moving. We have been able to provide an ultrasonic object detector that can reliably detect objects.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a time chart for explaining the same operation as above, and Figs. 3 and 4 show the reception ratio and transmission time interval. Graph showing the relationship, FIG. 5 is an im chart explaining the operation of another embodiment of the present invention, Ultrasonic transducer transmitter circuit receiver circuit detection distance calculation section detection distance comparison section reception gate setting section detection output Control unit Detection output drive circuit Alarm Reception ratio calculation unit Transmission pulse control unit Ultrasonic transmission pulse Ultrasonic pulse Reflected wave signal Reception signal Reception gate Monitoring gate Figure 1 Figure 2

Claims (2)

[Claims] (1) Send an ultrasonic pulse, receive the reflected wave from the object, and detect the object using the reception signal in the reception gate that indicates the predetermined detection distance range set by the reception gate setting section. In the pulse type ultrasonic object detector, a reception ratio calculation unit calculates a time ratio in which a reception signal is included in the reception gate, and a reception ratio calculation unit that calculates a time ratio in which a reception signal is included in the reception gate, and a reception ratio calculation unit that calculates a time ratio in which a reception signal is included in the reception gate; An ultrasonic object detector comprising a transmission pulse control section that outputs a control signal that makes the time interval variable. (2) A monitoring gate that constantly monitors the received signal is provided in addition to the receiving gate, and the receiving ratio calculation section calculates the proportion of time that the received signal is included in the receiving gate and the monitoring gate. , wherein the transmission pulse control section is configured to vary the time interval from one transmission to the next transmission according to the time ratio. Ultrasonic object detector.