JPS61172085A - Range finding type matter detection apparatus - Google Patents

Abstract

PURPOSE:To prevent erroneous information due to external noise generated in non-synchronous relation to a transmitted ultrasonic wave, by outputting a detection signal only when the difference between distances measured corresponding to one pulse like ultrasonic wave and the pulse like ultrasonic wave previous thereto is within a predetermined value. CONSTITUTION:An ultrasonic wave is transmitted from a transmitting part 10 to be received by a receiving part 20 and the delay time during this time is measured by a delay time measuring circuit 25. The delay time corresponding to one pulse like ultrasonic wave is stored in a first memory circuit 26. When the delay time corresponding to the next pulse like ultrasonic wave is stored in the circuit 26, the delay time having been stored in the circuit 26 is transferred to a second memory circuit 27 to be stored therein. The delay times stored in the circuits 26, 27 are compared by a comparing judge circuit 28 and a detection signal is outputted when the difference between both delay times is within a predetermined value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field 1] The present invention relates to a distance-measuring object detection device, and more particularly, to a distance-measuring object detection device that outputs a detection signal when an object is present within a predetermined distance. It is something.

[Background Art] Generally, as shown in FIG. 3, this type of distance-measuring object detection device causes an oscillation circuit 12 to intermittently oscillate at predetermined intervals determined by a transmission interval setting circuit 11, and transmits a wave. A pulsed ultrasonic wave is intermittently sent out through the device 13, and when this ultrasonic wave is reflected by an object 3 existing within the detection distance, this reflected wave is received by the delivery device 21, and the receiving circuit 22 receives the reflected wave. After performing amplification, noise removal, detection, etc., the detection date circuit 23 extracts only those whose time between transmitting the ultrasonic wave and receiving the reflected wave is within a predetermined time range. When a signal is output from the detection circuit 23, a determination circuit 24 outputs a detection signal.

That is, as shown in FIG. 4(a), when a pulsed ultrasonic wave is sent out from the transmitter 13, as shown in FIG. The vibrations are simultaneously transmitted to the transfer device 21 and received by the wave receiver 21.

Thereafter, the reflected wave is received by the delivery device 21. Delivery device 2
The signal received at 1 passes through the receiving section m22, so that
As shown in FIG. 4(c), the ultrasonic wave is output as a pulse having a time width equal to the time during which the ultrasonic wave is being received by the delivery device 21. As shown in FIG. 4 (1), the detection gate circuit 23 is designed to pass a signal for a predetermined time width after a predetermined time after the pulsed ultrasonic wave is sent out from the transmitter 13, and to receive the signal. When the pulse output from the circuit 22 is output within this time, it is passed through the determination circuit 24 and the pulse output as shown in FIG.
As shown in e), a detection signal is output.

However, in this object detection device, if any signal is received by the delivery device 21 within the time period during which the detection gate circuit 23 allows the signal to pass, it is determined that an object exists. There is a problem in that it cannot be distinguished from the waves and can cause false alarms due to noise. In addition, when multiple object detection devices are placed in the same space, there is a problem that mutual interference occurs and false alarms are generated due to ultrasonic waves from other object detection devices. l; When arranging object detection devices, it is necessary to synchronize the object detection devices.

[-Objective of the Invention] The present invention has been made in view of the above-mentioned points, and its main purpose is to measure the distance measured in response to one pulsed ultrasonic wave, The distance measured in response to the previous pulsed ultrasound is compared, and a detection signal is output only when the difference is within a predetermined value, making it asynchronous with the transmitted ultrasound. It is an object of the present invention to provide a distance measuring type object detection device that prevents false alarms from occurring due to external noises etc.

[Disclosure of the Invention 1 (Examples) Examples of the present invention will be described below based on the drawings. 1st
As shown in the figure, it includes a transmitting section 10 that transmits ultrasonic waves, and a receiving section 20 that receives reflected waves of the ultrasonic waves transmitted from the transmitting section 10 by an object.

The transmitter 10 includes a transmission interval setting circuit 11, an oscillation circuit 12, and a transmitter 13. The transmission interval setting circuit 11 generates pulses with a relatively long period, and the oscillation circuit 1
In step 2, electric vibrations having a frequency substantially equal to the frequency of the ultrasonic waves sent out from the wave transmitter 13 are generated. The oscillation circuit 12 oscillates intermittently using pulses that are the output of the wave transmission interval setting circuit 11, and the output of the oscillation circuit 12 is transmitted to the wave transmitter 13.
The pulsed ultrasonic waves are intermittently transmitted from the transmitter 13.

The receiving section 20 includes a transfer device 21, a receiving circuit 22, a detection gate circuit 23, and a delay time measuring circuit 25.

The ultrasonic waves received by the transfer device 21 are amplified by a receiving circuit 22, noise is removed through a bandpass filter, etc., and further detected, and a pulsed signal is input to a detection gate circuit 23. The detection gate circuit 23 detects a predetermined time after the rise of the output of the wave transmission interval setting circuit 11.
The gate is opened at a predetermined time interval, and only signals input within the time range in which the gate is open are allowed to pass through. The signal that has passed through the detection gate circuit 23 is input to the delay time measurement circuit 25, which measures the time from when the ultrasonic wave is sent out from the transmitter 10 to when the ultrasonic wave is reflected by an object and received by the receiver 20. be measured. That is, the delay time measuring circuit 25 is reset at the rising edge of the output of the pulse generated by the transmission interval setting circuit 11 of the transmitter 10, and is composed of a counter that counts the number of output pulses from the built-in reference oscillation circuit. The output value of the counter at the time when the received signal passing through the detection gate circuit 23 is input is set as the output of the delay time measuring circuit 25.

The output of the delay time measurement circuit l1125 is input to the first storage circuit 26, and the output value is stored in the first storage circuit 26. Then, when a pulsed ultrasonic wave is generated next and its reflected wave is received, the delay time is stored in the first storage circuit 26, and the previous delay stored in the first storage circuit 26 is stored. The time is stored in the second storage circuit 27. Therefore, the delay times corresponding to the two pulsed ultrasound waves are stored in the first memory circuit 26 and the second memory circuit 27. Memory value of first memory circuit 26 and second memory circuit 27
The comparison and judgment circuit 21N calculates the difference between the two stored values, and when this difference is smaller than a predetermined value preset in the comparison and judgment circuit 28, the comparison and judgment circuit 28 outputs a detection signal. It is now output.

To explain this operation with reference to FIG. 2, first, the transmitter 1
As shown in Figure 2 (a), pulsed ultrasonic waves are intermittently transmitted from the transmitter 13, as shown in Figure 2 (b). Pulsed ultrasound waves are received as shown in .

Further, since a reflected wave is generated when an object 3 exists within the detection area, the reflected wave is received by the delivery device 21 after a time proportional to the distance from the object 3. The output of the receiver 21 is signal-processed by the receiver circuit 22 to obtain a pulse having a width equal to the time during which the ultrasonic wave t is being received by the receiver 21, as shown in FIG. 2(c). The detection date circuit 23 is the second
As shown in Figure (c), pulsed ultrasonic waves are transmitted to the transmitter 13.
After a predetermined period of time has passed, the signal is opened for a predetermined time width, and only the signals received within this open time pass through the detection gate circuit 23. As a result, only objects 3 existing within a predetermined distance range are detected, and the detection area is set by this open time and the zero-order detection data is used to prevent reception of unnecessary signals. ) The signal passing through the circuit 23 is measured by the delay time measuring circuit 25 to calculate the time t, ~t, required from sending out the ultrasonic wave to receiving the reflected wave.
is measured and its value is stored in the first storage circuit 26.

Furthermore, when a signal is extracted from the detection gate circuit 23 next time, the stored value stored in the first storage circuit 26 is transferred to the second storage circuit 27, and a new value is stored in the first storage circuit 26. The stored value of the first housing circuit 26 and the stored value of the second storage circuit 27 are compared in the comparison/determination circuit 28, and as shown in FIG. 2(e), the stored value of the first storage circuit 27 and the stored value of the second A detection signal is output only when the difference from the stored value in the memory circuit 128 is within a predetermined value ±α. As a result, detection signals are output for objects that are stationary or move slowly. In the case of noise that occurs irregularly, the time from when the pulsed ultrasonic waves are sent to when the received signal is received is also irregular, and the stored value in the first storage circuit 26 and the value stored in the second storage circuit 27 are different. Since the difference from the stored value becomes large, false alarms do not occur.

[Effect of the Invention 1] As described above, the present invention includes a first storage means for storing a delay time corresponding to one pulsed ultrasonic wave, and a first storage means for storing a delay time corresponding to the next pulsed ultrasonic wave. a second storage means for storing the delay time stored in the first storage means 1 when the first storage means 1 is used; and a delay time stored in the first storage means and a delay time stored in the second storage means. Since the distance measured corresponding to one pulsed ultrasonic wave and the distance measured corresponding to one pulsed ultrasonic wave, It compares the distance measured in response to the previous pulsed ultrasound and outputs a detection signal only when the difference is within a predetermined value. This has the advantage that false alarms due to noise etc. do not occur.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is an explanatory diagram of the same operation as above, and FIG. 3 is a block diagram showing a conventional example.
FIG. 4 is an explanatory diagram of the same operation as above. 10 is a transmitter, 20 is a receiver, 3 is an object, 11 is a transmission gap setting circuit, 12 is an oscillation circuit, 13 is a transmitter, 21 is a receiver, 22 is a receiver circuit, 23 is a detection gate circuit , 25 is a delay time measuring circuit, 26 is a first storage circuit, 27 is a second storage circuit, and 28 is a comparison judgment circuit.

Claims (1)

[Claims] (1) A transmitting means for intermittently transmitting pulsed ultrasonic waves, a receiving means for receiving reflected waves of the ultrasonic waves transmitted from the transmitting means by an object, and a receiving means after the ultrasonic waves are transmitted from the transmitting means. A distance measuring object detection device comprising a delay time measuring means for measuring a delay time until the signal is received by the object, and a detection gate means for extracting only those whose delay time falls within a predetermined time from among the reflected waves, A first storage means for storing a delay time corresponding to one pulsed ultrasound wave, and a delay time corresponding to the next pulsed ultrasound sound stored in the first storage means when the delay time corresponding to the next pulsed ultrasound wave is stored in the first storage means. the second storage means for storing the delay time stored in the first storage means, and the delay time stored in the first storage means and the delay time stored in the second storage means, and the difference between the two delay times is within a predetermined value. What is claimed is: 1. A distance-measuring object detection device, characterized in that it is provided with a comparison and determination means that sometimes outputs a detection signal.