JPH04250388A - Ultrasonic object detector - Google Patents

Abstract

PURPOSE:To inhibit the erroneous operation due to noise, and to reduce the delay in detection time to a minimum level. CONSTITUTION:A plurality of sensor parts A for transmitting and inputting an ultrasonic pulse are provided. Only when a target is detected continuously by a predetermined number, it is judged by a control circuit that there is a target, respectively for each sensor part A. A noise surveillance period is provided before a point where an ultrasonic pulse is transmitted by each sensor part A. When there is a noise in a certain sensor part A, the number of judgement for the existence of the target related to the sensor part A is increased by the control circuit 4. The probability of erroneous operation due to noise is reduced by increasing the number of judgement for a sensor part A where the noise condition is bad. Since the number of judgement is not increased for a sensor part A where the noise condition is not bad, the judgement for the existence of the object is carried out promptly.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention includes a plurality of sensor units that transmit and receive ultrasonic waves, and each sensor unit transmits ultrasonic pulses and receives reflected waves from an object, and continuously transmits ultrasonic pulses a predetermined number of times. The present invention relates to an ultrasonic object detector that individually determines the presence of an object for each sensor section only when the object is detected.

0002

[Prior Art] Ultrasonic object detectors that detect objects using ultrasonic waves transmit ultrasonic pulses and receive reflected waves from objects. There are devices that detect the presence of objects within the detection area by searching for
It has the advantage of being able to measure the distance to an object relatively easily.

This type of ultrasonic object detector is used as an obstacle detection device (clearance sonar) for vehicles, and has sensor units that transmit and receive ultrasonic waves arranged at both ends of the front and rear bumpers of the vehicle. There are some that use each sensor section to detect obstacles near the bumper.

0004

[Problems to be Solved by the Invention] Conventional ultrasonic object detectors of this type may malfunction due to noise, resulting in a false detection output indicating the presence of an object even though no object is present, or noise. There is a problem that the distance to the object may be detected incorrectly. Therefore, ultrasonic object detectors have been developed that employ a multiple-time continuous detection method that prevents malfunctions due to noise by determining that an object exists only when the object is detected a predetermined number of times in succession.

However, in the ultrasonic object detector of the multiple continuous detection method described above, the probability of malfunction decreases as the number of times the presence of an object is determined increases; There is a problem that causes time delays. The present invention has been made in view of the above points, and its purpose is to provide an ultrasonic object detector that has a low probability of malfunction and can minimize detection time delays. .

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a noise monitoring period for monitoring the presence of noise before transmitting ultrasonic pulses from each sensor section, and eliminates the noise. When determining the presence of an object with respect to a sensor unit in which the presence of noise has been detected during the monitoring period, the signal processing means increases the number of times the presence of the object is determined.

[0007]

[Operation] By configuring the present invention as described above,
The noise condition of each sensor section is monitored, and the number of object presence judgments for the sensor section with poor noise condition is increased to reduce the probability of malfunction due to noise, and the sensor section with good noise condition is The existence of an object related to a part can be determined quickly.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an ultrasonic object detector according to an embodiment of the present invention. The ultrasonic object detector of this embodiment is used, for example, in an obstacle detection device for a vehicle, and includes a plurality of sensor sections A that transmit and receive ultrasonic waves, and a plurality of sensor sections A that transmit and receive ultrasonic waves from these sensor sections A. The main body part B performs object detection processing to detect the presence of an object from the received output of the reflected wave from the object of each sensor part A.

[0009] Each sensor section A is equipped with an ultrasonic transducer 1 for both transmitting and receiving waves, and is installed at four locations, for example, at the front right, front left, rear right, and rear left (hereinafter referred to as FR, FL, RR, and RL). is set up. However, it goes without saying that the sensor part A may be installed at a location other than the above-mentioned location, and the sensor part A may be provided with an ultrasonic transducer for each wave transmission and reception.

The main body B includes a transmitting circuit 2 for transmitting ultrasonic pulses from the ultrasonic transducer 1, a receiving circuit 3 for detecting reflected waves from an object from the received wave output of the ultrasonic transducer 1, C which operates the wave transmitting circuit 2 intermittently and determines whether an object exists in the detection area from the output of the wave receiving circuit 3.
It includes a control circuit 4 made up of a PU, and an output circuit 7 that drives a display or an alarm according to the output of the control circuit 4 when the presence of an object is detected. Here, a plurality of wave transmitting circuits 2 and wave receiving circuits 3 may be provided for each sensor section A as shown in FIG. 4, but in order to simplify the circuit configuration,
In this embodiment, each of the wave transmitting circuits 2 and the wave receiving circuits 3 are connected to one sensor section A in a selective manner using a switching circuit 8. A switching control signal is given from

In this ultrasonic object detector, the output of the wave transmitting circuit 2 is sent to the ultrasonic vibrator 1 via the reverberation absorption circuit 5.
The received wave output from the ultrasonic transducer 1 is input to the receiving circuit 3 via the amplifier circuit 6. It is installed in one piece. First, the basic operation of the ultrasonic object detector of this embodiment will be explained. The control circuit 4 sends a control signal to the wave transmitting circuit 2 at regular intervals to cause the wave transmitting circuit 2 to drive the ultrasonic transducer 1. As a result, the ultrasonic pulse P shown in FIG. 2(a) is transmitted. Note that when the ultrasonic transducer 1 is driven in this manner, reverberation Z is generated in the ultrasonic transducer 1, so a reverberation absorption circuit 5 for absorbing this reverberation Z is provided. If an object is present, the ultrasound transducer 1 receives the reflected wave from the object. The received signal waveform at this time is shown by R in FIG. 2(a). This received signal R is amplified by the amplifier circuit 6 and input to the receiving circuit 3, and the receiving circuit 3 detects the received signal R (envelope detection) and
Low-level noise components (e.g. white noise)
(this noise component is removed using the threshold value Vth shown in FIG. 2(a)), and the detected received signal R is waveform-shaped as shown by S2 in FIG. 2(b). and outputs it to the control circuit 4. Note that S1 in FIG. 2(b) indicates a signal waveform obtained by shaping the ultrasonic pulse P. Control circuit 4
Then, based on the output S2 of the wave receiving circuit 3, it is determined whether the wave reflected by the object is from an object within the detection area. This determination is performed during the receiving gate period corresponding to the distance of the detection area (for example, G
), and it is determined whether an object exists within the detection area based on whether the output S2 of the wave receiving circuit 3 is within the wave receiving gate period G. Note that the period T following the reception gate period G in FIG. 3A indicates a signal processing period for determining the presence or absence of an object and calculating the distance.

By the way, in this ultrasonic object detector, the control circuit 4 does not immediately determine that an object exists in the object detection operation described above, but only when an object is detected a predetermined number of times (for example, three times) in a row. It uses a multiple-time continuous detection method that determines that an object is present for the first time. In other words, in the ultrasonic object detector of this embodiment, the FR shown in FIG.
When one object detection operation using the sensor unit A of FL is completed, the switching circuit 8 connects the FL sensor unit A to the wave transmitting circuit 2 and the wave receiving circuit 3 under the control of the control circuit 4, and the above-mentioned In the same manner as in the case, the object detection operation is performed as shown in FIG. and the wave receiving circuit 3 to perform an object detection operation. When an object is detected in each of the three object detection operations for each sensor section A, the control circuit 4 determines that an object exists for that sensor section A, and takes actions such as issuing an alarm through the output circuit 7. Let it happen.

By the way, if it is determined that an object exists when object detection is performed three times in a row as described above, the detection time can be detected in a state where there is little delay and there is not a lot of noise. This has the advantage of being able to prevent malfunctions caused by noise. However, when the noise increases, the probability of malfunction increases, which poses a problem in preventing malfunction.

Therefore, in this embodiment, as shown in FIG. 3(a), a noise monitoring period M for monitoring noise is provided before the sending of the transmission pulse P by each sensor section A, and each sensor The noise state is detected before performing the object detection operation in section A. In other words, during this noise monitoring period M, the received signal received by the ultrasonic transducer 1 is transmitted to the control circuit 4.
detects the noise and determines the state of the noise. Note that during the noise monitoring period M, it is set so that the reflected waves of the ultrasonic pulses transmitted from the ultrasonic transducer 1 by objects are not received, so the signal components detected during this noise monitoring period M are as follows. All can be considered noise. If noise is detected during the noise monitoring period M in each sensor section A, the control circuit 4 increases the number of times of determination for that sensor section A to determine the presence of an object. For example, the number of times it is determined that an object exists is changed from 3 times to 10 times. In this way, the probability of malfunction due to noise can be reduced with respect to the sensor section A, which has a poor noise condition, and the reliability of object detection can be increased. Moreover, since the number of determinations is increased only for the sensor section A in which noise has been detected during the noise monitoring period M, there is no detection time delay in object detection for other sensor sections A.

In the above case, the number of determinations is uniformly increased depending on the presence or absence of noise, but of course the control circuit 4 can control the duration, the number of detections, or the level of noise from the detection output of the wave receiving circuit 3. It is also possible to make it possible to detect the noise level and the type (differences such as continuous noise or intermittent noise), and change the number of determinations depending on the noise state and the nature of the noise. Here, the appropriate number of times of determination according to the above-mentioned noise state and nature of the noise may be determined in advance, for example, by actual measurement under the actual usage environment, and stored in advance as a table in the built-in memory of the control circuit 4. Furthermore, the present invention provides a wave transmitting circuit 2 and a wave receiving circuit 3 for each sensor section A as shown in FIG.
It can also be applied to ultrasonic object detectors equipped with

[0016]

[Effects of the Invention] As described above, the present invention provides a noise monitoring period for monitoring the presence of noise before transmitting ultrasonic pulses from each sensor section, and detects the presence of noise during this noise monitoring period. Since the signal processing means increases the number of object presence determinations when determining the presence of an object with respect to a sensor section that has been Presence determination can increase the number of times the presence of an object is determined and reduce the probability of malfunctions due to noise. Moreover, since the number of times of determination is increased for each sensor section individually according to the noise state, the presence of an object can be quickly determined for sensor sections whose noise state is not bad.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a circuit configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an object detection operation same as the above.

FIG. 3 is an explanatory diagram of the noise monitoring operation same as above.

FIG. 4 is a block diagram showing a circuit configuration of another embodiment.

[Explanation of symbols]

A Sensor part 4 Control circuit

Claims (1)

[Claims] [Claim 1] A device comprising a plurality of sensor units that transmit and receive ultrasonic waves, each sensor unit transmits ultrasonic pulses and receives reflected waves from an object, and the object is detected a predetermined number of times in succession. In an ultrasonic object detector equipped with a signal processing means that individually determines the presence of an object for each sensor section for the first time, the presence of noise is monitored before the ultrasonic pulse is transmitted from each sensor section. An ultrasonic object characterized in that a noise monitoring period is provided, and the signal processing means increases the number of times the object presence is judged when determining the presence of the object with respect to a sensor unit in which the presence of noise is detected during the noise monitoring period. Detector.