JPH04250390A - Ultrasonic object detector - Google Patents

Abstract

PURPOSE:To reduce a random number sequence to be stored. CONSTITUTION:A plurality of sensor parts A for transmitting and inputting an ultrasonic pulse are provided. Ultrasonic wave are continuously transmitted from the sensor part A by a main body part B. A target detection process for detecting the existence of the object from the receiving wave output of the reflecting wave caused by the object of each sensor part A is carried out in time series for each sensor part A by the main body part B. One random number sequence is stored in a ROM 9 by the main body part B. An ultrasonic pulse is randomly transmitted from each sensor part A according to the random number sequence of the ROM 9. By using one random number sequence in common for the wave transmission of each sensor part A, the random number sequence to be stored is reduced.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention includes a plurality of sensor units that transmit and receive ultrasonic waves, and the ultrasonic waves are transmitted from these sensor units, and an object is detected from the received output of the reflected wave from the object of each sensor unit. The present invention relates to an ultrasonic object detector that includes a main body that detects the presence of an object, and the main body sequentially transmits ultrasonic waves from each sensor section to perform object detection processing for each sensor section in chronological order.

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. , a main body section that performs object detection processing that transmits ultrasonic waves from these sensor sections and detects the presence of an object from the received output of the reflected wave from the object of each sensor section, and the main body section sequentially moves from each sensor section. Some devices detect obstacles near the bumper by transmitting ultrasonic waves and performing object detection processing in each sensor section in chronological order.

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, the special application 1986-2
No. 28763 adopts 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, and also reduces the transmission interval of ultrasonic pulses. A random ultrasonic object detector has been proposed. According to this ultrasonic object detector, the probability of false detection due to noise can be significantly reduced.

In the above-mentioned ultrasonic object detector, a series of random numbers such as normal random numbers or uniform random numbers is stored in advance in a memory such as ROM or RAM, and when a random number request signal is generated, it is By specifying which one to output, a random number can be obtained, and the transmission interval of the ultrasonic pulses is thereby set at random. However, in ultrasonic object detectors that include multiple sensor units, such as the above-mentioned obstacle detection device for vehicles, random number sequences are required for the number of sensor units, so there is a problem that the storage capacity of the memory increases. Ta.

The present invention has been made in view of the above points, and its purpose is to reduce the capacity of a memory for storing a random number sequence for randomizing the transmission interval of ultrasonic pulses. An object of the present invention is to provide an ultrasonic object detector that can perform

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a storage means for storing one random number sequence;
The main body section is provided with wave transmission control means for reading random numbers from the storage means and randomly transmitting ultrasonic waves from the respective sensor sections.

[0008]

[Operation] By configuring the present invention as described above,
This eliminates the need for the main body to store a random number sequence for each sensor unit, thereby reducing the memory capacity for storing the random number sequence.

[0009]

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.

[0010] 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. 5, 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. 4(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. 4(a). This received signal R is amplified by the amplifier circuit 6 and inputted to the receiving circuit 3, which 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. 4(a)), and the detected received signal R is waveform-shaped as shown by S2 in FIG. 4(b). and outputs it to the control circuit 4. Note that S1 in FIG. 4(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 made by setting a reception gate period corresponding to the distance of the detection area, and by setting the reception gate period corresponding to the distance of the detection area, and
It is determined whether an object exists within the detection area based on whether or not it is within the reception gate period.

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 succession. It uses a multiple-time continuous detection method that determines that an object is present for the first time. That is, in the ultrasonic object detector of this embodiment, when one object detection operation using the FR sensor section A is completed, the switching circuit 8 switches the FL sensor section A under the control of the control circuit 4. is connected to the wave transmitting circuit 2 and the wave receiving circuit 3, the object detection operation is performed in the same way as in the case described above, and then each sensor is switched cyclically from RR, RL, and then from FR by the switching circuit 8. Part A is connected to the wave transmitting circuit 2 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.

Furthermore, in this embodiment, the transmission timing of the ultrasonic pulses is made random to reduce the probability of malfunction due to periodically generated noise. By the way, conventionally, as shown in FIG. 2(a), a random number sequence consisting of n pieces is stored in the ROM 9 of the control circuit 4 for each sensor section A (the total number of elements is 4n), and this random number sequence is read out. As a result, the wave transmission timing was set randomly as shown in FIG. 3(a). For this reason, a large-capacity ROM 9 is required, and for example, a one-chip microcomputer with a built-in ROM or RAM used as the control circuit 4 of this type of ultrasonic object detector has the problem of insufficient storage capacity. there were.

Therefore, in this embodiment, a random number sequence of n elements shown in FIG. 2(b) is stored in the ROM 9 of the control circuit 4, and this random number sequence is commonly used for each sensor section A. be. Then, a random number is output from the position indicated by the pointer, and the value of the pointer is incremented every time an ultrasonic pulse is transmitted, and the ultrasonic pulse is sequentially sent from the sensor part A according to the random number sequence as shown in FIG. 3(b). We will send waves. When the nth position of the random number sequence is reached, the value of the pointer is reset and random numbers are read from the first position. In this way, the sensor unit A can randomly transmit ultrasonic pulses using the same random number sequence as one. Moreover, since the number of elements of the random number sequence stored in the ROM 9 is reduced, the random number sequence can be sufficiently stored even in the built-in ROM of, for example, a one-chip microcomputer.

In the above case, the transmission interval was varied each time an ultrasonic pulse was transmitted by each sensor section A, but for example, as shown in FIG. 3(c), Each of the sensor units A transmits ultrasonic pulses at the same transmission interval,
The transmission interval may be changed every time the wave goes around. Further, as shown in FIG. 5, an ultrasonic object detector is provided with a wave transmitting circuit 2 and a wave receiving circuit 3 for each sensor section A, and the ultrasonic pulses are sequentially transmitted from each sensor section A. It goes without saying that the present invention can also be applied.

[0017]

Effects of the Invention As described above, the present invention includes a storage means for storing one random number sequence, and a wave transmission control means for reading random numbers from the storage means and randomly transmitting ultrasonic waves from each sensor section. is provided in the main body, the main body does not need to store a random number sequence for each sensor unit, and the capacity of the memory for storing the random number sequence can be reduced.

[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 comparing the random number sequence storage method of this embodiment with the conventional method. (a) is an explanatory diagram showing a conventional method of storing a random number sequence. (b) is an explanatory diagram showing a method of storing a random number sequence in this embodiment.

FIG. 3 is an operation explanatory diagram when comparing the ultrasonic pulse transmission interval setting method of this embodiment with the conventional method. (a) is an explanatory diagram showing a conventional transmission interval setting method. (b) is an explanatory diagram showing a method of setting a transmission interval according to the present embodiment. (c) is an explanatory diagram showing another transmission interval setting method.

FIG. 4 is an explanatory diagram of an object detection operation same as the above.

FIG. 5 is a block diagram showing a circuit configuration of another embodiment.

[Explanation of symbols]

A Sensor part B Main body 4 Control circuit 9 ROM

Claims (1)

[Claims] 1. A plurality of sensor sections that transmit and receive ultrasonic waves, and a main body section that transmits ultrasonic waves from these sensor sections and detects the presence of an object from the received output of the reflected wave from the object of each sensor section. In an ultrasonic object detector in which the main body sequentially transmits ultrasonic waves from each sensor section and executes object detection processing of each sensor section in chronological order, a storage means for storing one random number sequence. and a wave transmission control means for reading a random number from the storage means and transmitting ultrasonic waves randomly from each sensor section.