JPH0449076B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an ultrasonic object detector that detects objects using ultrasonic waves.

[Background Art] This type of ultrasonic object detector transmits ultrasonic pulses and receives reflected waves from objects existing in the detection area of the ultrasonic pulses.
From the presence or absence of reflected waves, or the time delay from the time the ultrasonic pulse is transmitted until the reflected waves are received,
There are devices that detect the presence of an object or the distance to the object. In this pulse type ultrasonic object detector, when noise having the same frequency as the ultrasonic pulse is received, it is not possible to distinguish whether the received signal is a reflection or noise.

Therefore, regarding noise that is periodically received by the receiving circuit, we measure the repetition period and duration of the noise from the received waveform pattern of the noise, and output a transmitting pulse when it is predicted that there is no noise. A method was adopted to do so. However, with this method, malfunctions due to noise can be prevented when the repetition period and duration of the noise are constant, but malfunctions due to noise can be prevented when the period or duration of the noise changes. There was a problem that I couldn't do.

[Object of the Invention] The present invention has been made in view of the above-mentioned points, and its purpose is to provide an ultrasonic object detection system that does not malfunction even in response to noise that changes in repetition period and duration. It is about providing the equipment.

[Disclosure of the Invention] (Structure) The present invention provides a method for reducing noise, which is a period in which an ultrasonic pulse is not transmitted from a wave transmitting circuit and is not received by a receiving circuit. Storage means for determining and storing the duration time and repetition period of each noise when at least three noise outputs are obtained in the reception circuit during the monitoring period; and the storage means a comparison means for comparing the duration time and repetition period of each of the above-mentioned noises given by the above-mentioned means to detect a state of change in the duration time of the noise and the repetition period, respectively; The time and period of occurrence of noise after the above-mentioned noise monitoring period are predicted from the data regarding the respective change states of the period, duration, and repetition period, and the time period during which the noise is predicted to be absent and objects can be detected is predicted. Equipped with a signal processing means that transmits ultrasonic pulses from a wave transmitting circuit, it is possible to detect objects without noise by predicting the time and period of occurrence of noise whose repetition period and duration change. Object detection is performed during a certain period of time.

(Embodiment) FIGS. 1 and 2 show an embodiment of the present invention, and this embodiment includes a wave transmitting circuit 2 that drives an ultrasonic transducer 1 to transmit ultrasonic pulses, A wave receiving circuit 3 that amplifies the ultrasonic wave received by the ultrasonic transducer 1, an amplification and detection circuit 7 that further amplifies and detects the output of this wave reception circuit 3, and a wave that is received by the output of this amplification and detection circuit 7. an object exists within the detection area when the received signal is received within a predetermined period (reception gate period) from the time when the ultrasonic pulse was transmitted;
Alternatively, there is a detection circuit 8 that detects the distance to the object based on the time delay between the transmission of the ultrasonic pulse and the reception of the reflected wave, and this detection circuit 8 displays the presence of the object or the distance to the object. The display device 9 is equipped with a display device 9. Note that each of the above-mentioned parts is the basic configuration of the ultrasonic object detector, and the configuration also includes a wave receiving circuit.

Next, the characteristic configuration of this embodiment will be explained. In addition to the circuits described above, this embodiment includes the following configuration for detecting changes in the repetition period or duration of noise. In other words, during the noise monitoring period, which is a period in which no ultrasonic pulses are transmitted from the transmitting circuit 2 and no ultrasonic pulses from the transmitting circuit 2 are received by the receiving circuit, the receiving circuit 2 When at least three noise outputs, which are received wave outputs at that time, are obtained, a memory circuit 4 for determining and storing the duration and repetition period of each noise; and a memory circuit 4 for determining and storing the duration and repetition period of each noise; a comparison circuit 5 that compares the noise duration and repetition period to detect changes in the noise duration and repetition period, and the noise duration and repetition period given from each of the circuits 4 and 5; Then, the time point and period of occurrence of the noise after the above-mentioned noise monitoring period are predicted from the data regarding the change state of duration and repetition period, and the data is transmitted during the period when it is predicted that there is no noise and object detection is possible. A signal processing circuit 2 that transmits ultrasonic pulses from a wave circuit 2 is provided. Note that the signal processing circuit 6 is a circuit that also includes a normal ultrasonic object detector, and the present embodiment is characterized in that it has a function of predicting the time point at which noise occurs and the period during which it occurs. Moreover, this signal processing circuit 6
The reception gate period for object detection by the detection circuit 8 is set.

The operation of this embodiment will be explained below. In the following description, a case will be described in which this embodiment is used as an obstacle detector for a vehicle. There are various types of noise that can be a problem when used as such an obstacle detector, but examples of typical acoustic noise in urban areas include noise emitted from the engines of cars and motorcycles. It will be done. This noise periodically emits tone burst-like pulse noise, and includes an ultrasonic component that becomes the noise of the obstacle detector. This kind of noise is
When a car or motorcycle is running at a constant speed,
As shown in Figure 2a, there is no change in the repetition period or duration of the noise, but when accelerating or decelerating a car, etc., the repetition period or duration of the noise changes as shown in Figure 2b. .

The following explanation will now be given assuming that the noise shown in FIG. 3 is present. Here, the period t shown in FIG.
In this case, the ultrasonic pulse is not transmitted from the wave transmitting circuit 2,
And the ultrasonic pulse from the transmitting circuit 2 is transmitted to the receiving circuit 3.
This indicates the noise monitoring period, which is a period during which no signal is received. In the case of this type of vehicle obstacle detector, the noise monitoring period t is a period from immediately before to the time when the ultrasonic pulse is transmitted by the transmitter circuit 2, and when the transmitter circuit It is preferable that the period is such that the ultrasonic pulses transmitted from the wave receiving circuit 3 are not received by the wave receiving circuit 3.

The noise received by the reception circuit 3 during this noise monitoring period t is stored in the storage circuit 4. Here, the memory circuit 4 stores the duration of the noise and its repetition period. Now, when the noise N ₁ in FIG. 3 is received, the memory circuit ₄ at that time
Detect and store by counting the duration of the period. Then, the time from the time when the noise _N1 is received until the next noise _N2 is received is detected and stored. Thereafter, the above operation is repeated every time a noise is received, and the duration and repetition period of each noise are memorized.

Then, at the time when the noise N ₂ is received and its duration and repetition period are detected (the repetition period is determined at the time when the noise N ₃ is received),
The data of the noise N _{2 as well as the previous noise N 1 are} given to the comparator circuit 5 . In this comparison circuit 5,
The amount of change in the duration and repetition period of each of the noises N ₁ and N ₂ is determined, and data indicating the amount of change is provided to the signal processing circuit 6 together with the data on the duration and repetition period. Note that data regarding the duration and repetition period may be provided from the storage circuit 4 to the signal processing circuit.

The signal processing circuit 6 supplied with these data determines the next noise occurrence point (in the case of FIG. 3, the noise N ₄ ) and the occurrence period (in this case, the noise N ₃ ) from the duration, repetition period, and state of change. (including the period of occurrence)
Predict.

A prediction method in the simplest case will be explained based on FIG. 3. As shown in FIG. 3, since the noise N ₃ is received within the noise monitoring period t, the signal processing circuit 6 determines the point of occurrence of the noise N ₃ from the output of the reception circuit 3 or the memory circuit 4. can. The period of occurrence of this noise N ₃ and the time of occurrence of the next noise N ₄ are different from those of other noises N ₁ and N ₂
This can be determined from the data on Here, the noise
The duration of N ₁ is 50 msec, and the repetition period is
100msec, and the duration of noise _N2 is 45msec,
Assuming that the repetition period is 90 msec, the noise is N ₃
The duration of the noise N ₃ is predicted to be 40 msec, and the repetition period of the noise N 3 is predicted to be 80 msec, so the generation time of the noise N ₄ is predicted to be 80 msec after the generation time of the noise N ₃ .

However, in the case of this embodiment, in order to detect both the time point of noise occurrence and the period of its occurrence, at least three noises exist within the noise monitoring period t, and the duration and repetition of at least two noises are detected. It is necessary that the period can be detected within the noise monitoring period t.

In this way, when the signal processing circuit 6 predicts the time point and period of noise occurrence, the signal processing circuit 6
In this case, it is possible to determine the period in which there is no noise and object detection is possible. For example, in the case of FIG. 3, the signal processing circuit 6 determines the period from the time when this noise _N3 disappears to the time when the next noise _N4 is received from the duration and repetition period of the noise _N3 . . Note that, at this time, it is also determined at the same time whether the period is longer than the period required for the object detection operation (for example, about 10 msec). Assuming that this judgment operation ends at time A in FIG. 3, if object detection is possible at this time A, the ultrasonic pulse is transmitted from the wave transmitting circuit 2. However, in the case of Fig. 3, the time point A is not the period during which the object can be detected.
No ultrasound pulses are transmitted. And the noise N ₃
The transmitting circuit 2 is driven to transmit an ultrasonic pulse at an appropriate point in the period from the time when the noise N ₄ disappears to the time when the next noise N 4 is received, at time B in the case of FIG. In this way, object detection can be performed during a period when no noise is present, and malfunctions due to noise can be prevented.

Here, if the period from the time when the noise N ₃ disappears to the time when the next noise N ₄ is received is shorter than, for example, the period during which object detection is performed, the ultrasonic pulse is not transmitted, Continue the above noise monitoring operation. Then, object detection is performed when the noise condition becomes such that object detection can be performed normally.

Additionally, the above explanation was for a vehicle object detector, but it can also be used for other object detectors in an environment where there is noise whose duration or repetition period changes periodically. In the object detector that is used, the duration of the noise during the period in which the ultrasonic pulse is not transmitted from the wave transmitting circuit 2 and the ultrasonic pulse from the wave transmitting circuit 2 is not received by the wave receiving circuit 3. By monitoring the noise generation period and the repetition period and predicting the noise generation period using the signal processing circuit 5, it is possible to similarly perform object detection without malfunction. Furthermore, although the above explanation describes the simplest case, even when the duration of the noise and the repetition period are complex changes such as so-called oscillating motion where the repeating period repeats long and short states, if a sufficient amount of data is obtained, It is possible to make predictions using the signal processing circuit 6.

[Effects of the Invention] As described above, the present invention provides a period during which no ultrasonic pulses are transmitted from the wave transmitting circuit and no ultrasonic pulses from the wave transmitting circuit are received by the wave receiving circuit. a storage means for determining and storing the duration time and repetition period of each noise when at least three noise outputs are obtained in the reception circuit during the noise monitoring period; Comparison means for comparing the duration of each of the noises given by the means with the repetition period to detect a state of change in the duration of the noise and the repetition period, and the duration of the noise given by each of the above means. , the time point and period of occurrence of the noise after the above-mentioned noise monitoring period are predicted from the data regarding the repetition period and the state of change between the duration and the repetition period, and it is predicted that there is no noise and the object can be detected. Since it is equipped with a signal processing means that transmits ultrasonic pulses from a wave transmitting circuit during a period of time, it is possible to predict the time and period of occurrence of noise whose repetition period and duration change, and to detect the presence of noise. Object detection can be performed during a period in which objects can be detected, and therefore malfunctions are less likely to occur even due to noise whose repetition period or duration changes.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of an embodiment of the present invention, Fig. 2 a and b are explanatory diagrams of noise that occurs in a fixed period and noise whose period is variable, and Fig. 3 is an explanatory diagram of the same operation. It is. 2 is a wave transmitting circuit, 3 is a wave receiving circuit, 4 is a memory circuit,
5 is a comparison circuit, and 6 is a signal processing circuit.

Claims (1)

[Claims] 1 In an ultrasonic object detector that detects the presence of an object or the distance to the object by intermittently transmitting ultrasonic pulses from a transmitting circuit and receiving reflected waves from the object in a receiving circuit, the above-mentioned During the noise monitoring period, which is a period in which no ultrasonic pulses are transmitted from the transmitter circuit and no ultrasonic pulses from the transmitter circuit are received by the receiver circuit, the receiver circuit When at least three noise outputs that are wave outputs are obtained, a storage means for determining and storing the duration and repetition period of each noise, and the duration and repetition of each of the noises given from the storage means. Comparison means for detecting changes in the duration time and repetition period of the noise by comparing the period, and the duration time and repetition period of the noise given by each of the above means, and the respective changes in the duration time and the repetition period. A signal that predicts the time and period of noise occurrence after the above-mentioned noise monitoring period from the data regarding the state, and causes the transmitter circuit to transmit ultrasonic pulses during the period when it is predicted that there is no noise and object detection is possible. An ultrasonic object detector comprising processing means.