JPS6353514B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic moving object detection device, and its purpose is to have an accurate moving object detection setting distance, detect only moving objects within the set distance, and detect stationary objects. The purpose is to prevent malfunctions.

Conventional ultrasonic detection devices can be roughly divided into pulse type devices that emit ultrasonic pulses and detect the presence of an object based on the presence or absence of reflection, and those that emit continuous waves where the ultrasonic waves are subjected to the Doppler effect by moving objects. There are two types: a moving object detection method that detects changes in frequency and detects the movement of objects. In the case of the former pulse method, when detecting objects such as people or vehicles, if there are other objects such as trees or walls within the detection setting distance, these will be detected, so it cannot be used in such places. Furthermore, in the case of the latter moving object detection method, since continuous waves are used, the detection distance is not clear, and moving objects outside the detection distance are also detected. In addition, with conventional pulsed Doppler ultrasonic moving object detection devices, distance setting is not precise due to the influence of reflection from stationary objects, and
This has the disadvantage that there is a large possibility of erroneous movement.

The present invention has been made in view of this point, and will be explained in detail below with reference to Examples.

In FIG. 1, 1 is a periodic oscillator, 2 is a distance gate, and distance gate 2 is for setting the detection distance of a moving object. 3 is the input gate, the transmission period,
This is used to set the wave reception period and mixer input period. 4 is an oscillator, 5 is a switch that controls the oscillation output, 6 is an amplifier, and 7 is a transmitter that emits ultrasonic waves. 8 is a receiver, 9 is an amplifier for amplifying the received wave output, and 10 is a switch for controlling the received wave output.
A mixer 11 mixes the oscillation output and the received wave amplification output. Reference numeral 12 is a detector for detecting the mixer output, and reference numeral 13 is a band amplifier, which amplifies only the detected output in a certain frequency range. 14
is a level comparator that detects the output level of the band amplifier 13, 15 is an integrating circuit, and 16 is a first AND circuit that connects the output of distance gate 2 and input gate 3.
A gate signal is generated during the signal processing period using the output. 17 is a differentiating circuit, the first AND circuit 1
A signal at the start of signal processing is generated by the output of 6. 18
is a second AND circuit which generates a first signal processing execution determination signal from the output of the integrating circuit 15 and the output of the differentiating circuit 17. A flip-flop 19 holds the output of the second AND circuit 18 during signal processing, and a third AND circuit 20 connects the output of the integrating circuit 15 and the flip-flop 1.
The output of 9 is used to generate a second signal processing execution determination signal. A switch 21 controls the signal processing circuit 22 based on the output of the AND circuit 20.

The periodic oscillator 1 is an oscillator for creating the distance gate 2 and the input gate 3, and is shown in Fig. 2a or Fig. 3a.
Create a repetition period OP of ultrasonic pulse radiation.
The distance gate 2 is a gate that sets the time it takes for the ultrasonic wave to reach a set distance and return, as shown in Figure 2a or Figure 3a, that is, the time it takes for the ultrasonic wave to travel a distance twice the detection distance. . The input gate 3 is a gate that determines the wave transmission period, the wave reception period, and the input period of the oscillation output to the mixer 11, as shown in FIG. 2b or 3b.

First, when the oscillator 4 oscillates an output with a frequency corresponding to the ultrasonic frequency, the output is passed through the switch 5 only during the ON period of the input gate 3.
The signal is amplified by the amplifier 6, and the transmitted wave output as shown in FIG. 2c or 3c is radiated into the air from the transmitter 7.
The emitted ultrasonic waves are reflected by an object and sent to a receiver 8.
The received wave is received by the amplifier 9, amplified by the amplifier 9, and the received wave output is obtained by the switch 10, which passes only during the ON period of the input gate 3, as shown in FIG. 2d or 3d. On the other hand, the oscillation output controlled by switch 5 is
The mixer 11 mixes the received wave with the amplified signal to obtain a mixed wave output as shown in FIG. 2e or 3e, and this output is detected by the detector 12. Since the received amplified signal is out of phase even if it is not affected by the Doppler effect, the detected output changes smoothly at the rising and falling parts as shown in Figure 2 f, and within the set distance. If there is a stationary object, the phase shift caused by the stationary object will result in a prominent waveform as shown at point A in FIG. 2f.

If only a stationary object exists within the detection set distance, the output of the detector 12 will be as shown in FIG. 2f, as described above, and the output of the band amplifier 13 will be as shown in FIG. 2g. The band amplifier 13 amplifies only the Doppler frequency fd in the desired range expressed by the following equation.

fd=fo×2V/C However, fo: Transmission (oscillation) frequency V: Speed of moving object C: Speed of sound If a stationary object and a moving object exist within the detection setting range, the output of the detector 12 is The output of the band amplifier 13 is as shown in FIG. 3(f), and the output of the band amplifier 13 is as shown in FIG. 3(g). The output of the band amplifier 13 is judged by a level comparator 14 as to whether its level is above a certain level V _A , below a certain level V _B , or somewhere in between. Figure h
Or as shown in Figure 3h. Since the level of this output changes instantaneously when the output of the band amplifier 13 moves from the crest to the trough or from the trough to the crest of the wave, the level is maintained by the integrating circuit 15 to compensate for this. to obtain an output as shown in FIG. 2 i or 3 i. That is, the output of the integrating circuit 15 is H.
At the level, the Doppler effect is caused by the moving object, but there is a phase shift in the reflected waves.

Next, a signal processing period gate signal as shown in FIG. 2j or 3j is created from the output of the distance gate 2 and the output of the input gate 3 by the first AND circuit 16. At this time, specifically, as shown in FIG. 4, the output of the distance gate 2 is inputted to the first AND circuit via the inverter 23. The output of this first AND circuit 16 is differentiated by a differentiating circuit 17 to obtain a second
A signal at the start of signal processing as shown in FIG. k or FIG. 3 k is created. That is, at the start of signal processing (point B), whether or not to perform signal processing is determined depending on whether the output of the integrating circuit 15 is at H level or L level.
Make the next decision. In other words, when there is a moving object within the detection set distance, the output of the second AND circuit 18 which receives the output of the integrating circuit 15 and the differentiating circuit 17 becomes H level as shown in FIG. A first order signal is created for the purpose. or,
When there is only a stationary object within the detection distance or when there is a moving object beyond the detection distance, the integration circuit 15
Since the output of the second AND circuit 18 is at the L level, the output of the second AND circuit 18 remains at the L level as shown in FIG. 2l, and no signal processing is performed. The output of the second AND circuit 18 is transferred to the third
As shown in Figure m, this output is held for the signal processing period, and the output of the third AND circuit 20, which receives this output and the output of the integrating circuit 15 as input, as shown in Figure 3N, is used to determine whether to perform the second signal processing. Let's do it. That is, even if a stationary object exists at the position of the detection setting distance, the first signal processing execution judgment signal is output, but since the output of the integrating circuit 15 only momentarily becomes H level, the second signal processing execution judgment signal is output. The next signal processing execution determination signal will be output only for a very short period of time compared to the signal processing period. The operation of the signal processing circuit 22 can be controlled by controlling the switch 21 using the signal processing execution determination signal obtained as described above, that is, the output of the third AND circuit 20.

The present invention is configured as described above, and is a pulse Doppler type ultrasonic moving object detection device provided with a distance gate, in which a signal processing period gate is set from the rear end of the distance gate, and the distance gate and Ultrasonic pulses are emitted for a certain period of time by an input gate including a signal processing period gate, and depending on whether a Doppler output (integrator circuit output) is obtained at the front end of the signal processing period gate (rear end of the distance gate). It is determined whether or not a moving object exists within the distance gate, and if a Doppler output is obtained, it is assumed that a moving object exists and the first signal processing execution judgment signal is output. It has the effect of being able to accurately determine whether the object exists within the set distance, and when the first signal processing execution judgment signal is obtained, signal processing is performed only during the period when Doppler output is obtained. A second signal processing execution judgment signal (third AND circuit output) that operates the circuit is output, and the signal processing circuit executes signal processing of the Doppler output to perform a moving object detection operation. This has the effect of reliably preventing malfunctions caused by stationary objects within the set distance and malfunctions caused by moving objects beyond the set distance.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram of an embodiment of the present invention.
Figures 2 a to n are operation time charts when only a stationary object is present, Figures 3 a to n are operation time charts when a stationary object and a moving body are present, and Figure 4 is an operation time chart of the present invention. FIG. 2... Distance gate, 3... Input gate, 4...
Oscillator, 7... Transmitter, 8... Receiver, 11...
mixer, 12...detector, 13...bandwidth amplifier, 14...level comparator, 15...integrator circuit,
16...first AND circuit, 17...differentiation circuit,
18...Second AND circuit, 19...Flip-flop, 20...Third AND circuit, 22...Signal processing circuit.

Claims (1)

[Claims] 1 The output from the oscillator is emitted as an ultrasonic pulse from the transmitter for a certain period of time, the reflected wave from the object is received, this received wave output is mixed with the oscillation output in a mixer, and this mixed output is detected. This is a pulsed Doppler type ultrasonic moving object detection device that detects the movement of an object by extracting the frequency change component by detecting the movement of an object. , and an output of an input gate that sets a mixer input period, and outputs a signal processing period gate signal;
a differentiation circuit that differentiates the output of the first AND circuit to create a signal at the start of signal processing; and a level comparator that determines the level of the output obtained by band-amplifying the detection output obtained by detecting the mixed output from the mixer. , an integrating circuit that integrates the output of the level comparator; a second AND circuit that receives the output of the integrating circuit and the output of the differentiating circuit and outputs a first signal processing execution determination signal; A third AND circuit receives the output of the AND circuit held by a flip-flop and the output of the integrating circuit and outputs a second signal processing execution determination signal, and the output of the third AND circuit A pulse Doppler type ultrasonic moving object detection device characterized in that it is configured by controlling a signal processing circuit.