JPS6138478A - System for detecting object by ultrasonic wave - Google Patents

Abstract

PURPOSE:To make it possible to detect only a moving object with high sensitivity, by comparing the phase change of the reference wave from an oscillation circuit and a reflected wave with a reference level. CONSTITUTION:The signal S3 and reference wave signal S1 from an oscillation circuit 1 are respectively sent to an ultrasonic transducer 2 and a phase change detection circuit 7 and the signal of a receiving transducer 3 receiving the reflected wave from an object is amplified by an amplifying circuit 4 while the signal S4 thereof is sent to the circuit 7 and an amplitude level detection circuit 5. Further, when the signal of the circuit 5 is equal to or more than a predetermined level, alarm output S6 is generated from a comparing circuit 6 and the circuit 7 receives said signal S6 to detect and process the phase difference of the signals S1, S4 while the output S7 thereof is outputted to a memory circuit 8 and differential amplifying circuit 10, and successive phase change and the reference level thereof are respectively stored in the circuit 8. The difference between the reference level and the signal S7 is amplified by the circuit 10 to output a signal S9 and, when said signal S9 is larger than a definite level, a comparing circuit 11 outputs the alarm output S10 only of the moving object.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an object detection method for detecting stationary objects and moving objects using ultrasonic waves.

In this type of conventional method, ultrasonic waves are transmitted for a short period of time (for example, about 1 msec) A
By transmitting ultrasonic waves in a circular pattern and receiving the reflected waves reflected by an object, and processing the amplitude level of the reflected waves and the time from when the ultrasonic waves are sent until they are reflected back, the ultrasonic waves can be transmitted over a predetermined distance. Detects the presence or absence of an object within.

However, in the above conventional method, reflected waves are received whether the object is stationary or moving, making it difficult to distinguish between stationary and moving objects. In other words, when trying to detect a moving object by changing the amplitude level of the reflected wave, the amplitude level remains 1 and does not change depending on the moving direction of the moving object (such as when moving horizontally with respect to the receiver). In some cases, it is difficult to detect only moving objects.

The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional technology.In an object detection method using ultrasonic waves, the present invention adds not only amplitude information of reflections and waves but also phase information. The purpose of the present invention is to provide a detection method that can detect a moving object more reliably and with higher sensitivity than with just one piece of information by signal processing.

Embodiments of the present invention will be described below with reference to the drawings.

In Fig. 1, 1 is an oscillation circuit, 2 is a transmitting transducer, and 3 is a receiving transducer. -, 4 is an amplifier circuit, 5
1 is an amplitude level detection circuit, 6 is a comparison circuit, 7 is a phase change detection circuit, 8 is a storage circuit, 9 is a control pulse generation circuit, 10
1) is a differential amplifier circuit, and 1) is a ratio 1-bit circuit.

Next, the operation of the above configuration will be explained using the time chart of FIG. 2. The oscillation circuit 1 oscillates a reference signal SI, outputs this signal S to the phase change detection circuit 7, and controls the signal S2 to synchronize the transmission and control A/response. It outputs to the generation circuit 9, and also outputs a signal Ss for transmitting pulsed sound waves to the wave transmitting transducer 2.

In this case, the oscillation circuit 1 includes a counter circuit, a one-shot multivibrator circuit, a switching circuit, etc., and generates and outputs signals St and Ss from the signal S. The transmitting transducer 2 receives a signal S3 from the oscillation circuit 1).
Emit pulsed sound waves into space.

The sound waves sent out in a υnolus shape by the transmission transducer 2 will be reflected by stationary or moving objects if these objects exist within the sensing area, and the sound waves will travel back and forth between the objects after being sent out. The signal is received by the reception transducer 3 after a period of time. After this received signal is amplified by the amplifier circuit 4,
The signal S4 is output to the amplitude level detection circuit 5 and the phase change detection circuit 7. The amplitude level detection circuit 5 detects the amplitude level of the received signal S, and outputs the signal S to the comparison circuit 6. The comparison circuit 6 compares the amplitude level to a certain level (threshold level), and if the amplitude level is higher than the certain level, the comparison circuit 6 informs that an object (a stationary object or a moving object) is present. °↑The information output S6 is generated. On the other hand, the phase change detection circuit 7 operates upon receiving the output -3a of the comparison circuit 6, and receives the reference wave signal S oscillated by the oscillation circuit 1 and the received wave signals S4 and f: first, the waveform changes from a sine wave to a square wave. By converting and performing the ANDJ of the logic circuit, the phase difference between the reference wave signal S and the received signal S4 is detected,
Further, this phase difference is subjected to a ripple conversion by analog processing or digital processing, only the change is extracted, and the output S7 is outputted to the storage circuit 8 and the differential amplifier circuit 10. This change in phase difference is stable with almost no change in a stationary object, but changes rapidly in a moving object. Therefore, stationary objects and moving objects can be detected by signal processing this phase change. Detection of a moving object based on this phase change has a much larger amount of change than signal processing of changes in amplitude level, and can be detected with high sensitivity. Although the output S7 of the phase change detection circuit 7 shown in FIG. 2 is analog-processed, it may be a digital amount obtained by digital processing.

The storage circuit 8 is controlled by the control pulse signal 'S8 generated by the control pulse generation circuit 9, and consists of a part that stores successive phase changes and a part that stores the reference level of the phase change. 5a(t.

Reading and writing are controlled by n pulses that can be arbitrarily set (t2...tx...ty...tn). The reference level of phase change is in this example -
The phase difference before the cycle is used as the reference level, but in order to slowly respond to environmental changes, the next phase change is calculated by an arithmetic circuit (not shown) and follows the successive phase changes with a certain time constant. You may change it as follows. The differential amplifier circuit 10 amplifies the difference between the reference level of the phase change in the storage circuit 8 and the successive phase changes from the phase change detection circuit 7, and outputs this amplified signal S. so(tx) indicates a phase change of a stationary object, and 5o(ty) indicates a moving object axis phase change.

Furthermore, in the comparison cycle r51), it is compared with a constant level (threno-should level) and output as a small fJ report output 310 of only the moving object.

It should be noted that the circuit 41 may be formed by analog circuits, or may be formed by digital circuits since signal processing and the like can be performed by digital circuits.

As described above, in the present invention, a moving object is detected when the phase of the reference liquid and the reflected wave, . When detecting a moving object by
rJ, depending on the direction of movement (such as when moving horizontally with respect to the receiver), the amplitude level may not change much and it may be difficult to detect only a moving object, but even in such cases the phase is reliable. Therefore, there is no extreme difference in sensitivity depending on the direction of movement, and a moving object can be detected reliably. In addition, the shorter the wavelength of the transmitted wave, the more the phase change will change with respect to the movement of the object, so sensitivity can be increased by increasing the transmitting frequency, and it is more sensitive than the conventional method due to changes in the amplitude level. can do. Furthermore, by detecting changes in amplitude level together with phase changes, it is possible to detect not only moving objects but also stationary objects. Furthermore, by measuring the time from when the ultrasonic wave is sent until it is reflected back, it is possible to obtain distance information about stationary and moving objects, and perform highly sensitive signal processing using multi-h'f information. can improve reliability.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are a block diagram and a time chart, respectively, of an object detection device according to the present invention. 1... Oscillation circuit, 2... Transmission transducer, 3
... Receiving transducer, 4... Amplification circuit, 5.
...Amplitude level detection circuit, 6.1)...Comparison circuit, 7
... Phase change detection circuit, 8... Memory circuit, 10...
・Differential amplifier circuit.

Claims (2)

[Claims] (1) An oscillator circuit that generates a reference wave, a transmitter transducer that generates ultrasonic pulses according to the output of the oscillator circuit, a receiver transducer that receives reflected waves of the ultrasonic pulses, and a reference wave and reflected waves. A phase change detection circuit that detects a phase change between the two and a memory circuit that stores this phase change,
An object detection method using ultrasonic waves, characterized in that a reference level generated by a memory circuit is compared with an output of a phase change detection circuit, and a moving object is detected when the difference is greater than a predetermined value. (2) An oscillator circuit that generates a reference wave, a transmitter transducer that generates ultrasonic pulses according to the output of the oscillator circuit, a receiver transducer that receives reflected waves of the ultrasonic pulses, and a reference wave and reflected waves. a phase change detection circuit for detecting a phase change between
An object is detected when the amplitude level is greater than a predetermined value, and a moving object is detected when the reference level generated by the memory circuit and the output of the phase change detection circuit are compared and the difference is greater than a predetermined value. Features an object detection method using ultrasonic waves.