JPH0827342B2 - Obstacle detection device for automated guided vehicles - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an obstacle detection device for an automated guided vehicle that detects an obstacle in front of the traveling direction by using ultrasonic waves.

[Conventional technology]

In order to ensure safety while the automatic guided vehicle is in progress, an obstacle detection device that detects an obstacle in front of the traveling direction is provided, and ultrasonic waves are usually used for detection. An ultrasonic wave is oscillated forward from the ultrasonic wave oscillating means, and the ultrasonic wave reflected by the obstacle is received to decelerate or stop the automatic guided vehicle.
The ultrasonic wave oscillating means and the receiving means are usually shared by one ultrasonic wave sensor.

In a factory, many noises in a frequency band close to the oscillation frequency of the ultrasonic sensor may be generated. For example, an acoustic blower using compressed air produces acoustic noise in a frequency band close to that of the ultrasonic sensor.
If such noise is generated, a malfunction occurs in reception of the ultrasonic sensor, and a situation occurs in which the automated guided vehicle cannot operate normally. As shown in FIG. 3 by the reception level, the obstacle detection state when the ultrasonic sensor is operating normally,
If there is no noise, obstacles are normally detected by the receiving units A ₁ , A ₂ , A ₃ , but if noise B is present as shown in FIG. And it becomes difficult to judge whether the received signal is due to an obstacle or noise,
It causes malfunction.

In order to prevent the above malfunction, the device disclosed in Japanese Patent Publication No. 55-21315 is known. This device is
As shown in the figure, the normal reflection pulse C and the noise D reflected from the obstacle are respectively shaped into waveforms, and the gate circuit processing for a certain period of time ignores the noise in the short pulse receiving period, and Only the signal of the long normal reflection pulse C is detected.

[Problems to be solved by the invention]

However, the device disclosed in Japanese Examined Patent Publication No. 55-21315 can distinguish noise having a short generation period from a reflected signal due to an obstacle, but cannot cope with continuous noise due to an air blow device or the like. There is a problem.

It is an object of the present invention to provide an obstacle detection device for an automated guided vehicle, which can prevent malfunction due to noise generated in, for example, a factory.

[Means for solving problems]

An obstacle detection device for an automated guided vehicle of the present invention that achieves the above object is as follows.

An ultrasonic wave oscillating means for oscillating ultrasonic waves toward the front of the automatic guided vehicle, and an ultrasonic wave receiving means for receiving the ultrasonic waves oscillated by the ultrasonic wave oscillating means returning to the obstacles, Time gate creating means for creating a plurality of continuous time gates corresponding to a detection area formed by virtually dividing the space in front of the automated guided vehicle into a plurality of times, and a plurality of time gates created by the time gate creating means Noise presence determining means for determining whether or not the received signal contains noise by the number of time gates to which the received signal received by the ultrasonic receiving means is input, and the received signal is the plurality of times. Obstacle detection in an automated guided vehicle, which comprises detection area determination means for determining from which detection area the reflected ultrasonic wave reception signal is received depending on which time of the gates is input Location.

[Operation] In the above-mentioned device of the present invention, the obstacle is detected as an ultrasonic wave reflection signal from within several detection areas. Acoustic noise due to an air blower or the like is usually detected simultaneously from many detection areas. Therefore, it is possible to clearly discriminate between a signal due to an obstacle and a signal due to noise, and when it is judged as noise, its output is ignored, and only when it is due to an obstacle, it is correctly outputted and malfunction is prevented.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

1 and 2 show an obstacle detection device for an automated guided vehicle according to an embodiment of the present invention. In FIG. 2, 1
Indicates an automatic guided vehicle used in a factory or the like. Ultrasonic oscillating means for oscillating ultrasonic waves forward in the traveling direction and ultrasonic waves oscillated by the ultrasonic oscillating means are reflected and returned to the front obstacle 3 at the front part of the automatic guided vehicle 1. A transmitter / receiver oscillator 2 having an ultrasonic wave reception interruption that receives an ultrasonic wave and generates a weak current is provided.

Reference numeral 4 in FIG. 1 denotes a transmission frequency generation circuit, in which a signal having a wavelength determined by the circuit 4 is transmitted / received by a transmission drive circuit 6 at a cycle determined by an oscillation cycle generation circuit 5. The ultrasonic waves are transmitted to the child 2, and ultrasonic waves are oscillated in the air from the vibrator 2. The ultrasonic waves reflected from the obstacle 3
The signal is again received by the transmitter / receiver vibrator 2, and a weak current is generated. This weak current is shaped by the filter 7 and the amplifier 8
Is amplified by and transmitted to the detection area determination circuit (detection area determination means) 9 as a reception signal. On the other hand, the reference gate creating circuit 10 creates and transmits a reference signal to the time gate creating circuit (time gate creating means) 11. On the basis of this reference signal, the time gate creating circuit 11 detects a detection area m ₁ to m _{m formed} by virtually dividing the space in front of the automatic guided vehicle into a plurality of areas.
A plurality of continuous time gate signals of n ₁ to n _m corresponding to are generated and sent to the detection area determination circuit 9. The detection area judgment circuit 9 judges which time gate, n ₁ to n _m , has received the received signal from the amplifier 8 and, as shown in FIGS. 1 and 2, in the forward direction of the automatic guided vehicle. It is divided into a plurality, detection area M (m ₁ corresponding to the time gate n ₁ ... n _m ...
It is determined in which detection area (m _m ) the obstacle exists.

The detection output from the detection area determination circuit 9 is the calculation CPU
(Determination means). The determining means includes a noise presence / absence determining means for determining whether the ultrasonic waves received by the transmitter / receiver oscillator are reflected by an obstacle or due to noise, and the obstacle relatively approaches the automatic guided vehicle. It is equipped with obstacle relative movement direction determination means for determining whether the vehicle is moving or moving away. The output signal of the determination means is sent to, for example, the wheel 12 driving motor 13, and the automatic guided vehicle is responsive to the output signal. 1 is decelerated or stopped.

Normally, when there is an obstacle 3 in front of the automated guided vehicle 1, depending on the distance to the obstacle 3, several (for example, 1 to 2) areas in a plurality of detection areas are detected and output, As the time gate, one or two time gates are input. Many in the case of noise (for example, 3 or more)
Is detected and output, and as time gates, a large number (for example, three or more) of time gates are input. The reception pattern when there is no noise is as shown in FIG. 3 described above, and the detection area determination circuit 9 clearly detects in which detection area an obstacle is present. However, when there is noise, for example, when there is acoustic noise due to an air blower or the like, the noise has a high sound pressure level and is received as a signal from a large number of detection areas as shown in FIG. Therefore, when input as signals from many detection areas, it is judged as noise, and this output is ignored for a certain period of time.
The malfunction of the automated guided vehicle due to noise is prevented. Therefore, the noise presence / absence determining means is configured to determine whether or not the received signal includes noise, based on the number of time gates input. Further, when there are a plurality of obstacles, the ultrasonic wave is reflected by the closest obstacle, so detection and output are performed only for the closest obstacle.

Moreover, since the detection area is divided into a plurality of areas and the detection of the obstacle is repeated, the detected obstacle 3 is the second one.
Is it an obstacle approaching as shown in (a) to (b)?
Alternatively, it can be easily determined whether the obstacle is moving away. Then, like the noise described above, obstacles that are moving away are ignored, and a command signal is issued only for obstacles that are approaching, and the automated guided vehicle 1 is decelerated or stopped based on the command signal. The obstacles that are moving away are those that do not have the risk of colliding with the automated guided vehicle, and are not actually obstacles to the automated guided vehicle. Can be operated, and speedy transportation is possible.

[Advantages of the Invention] According to the obstacle detection device for the automatic guided vehicle of the present invention, since it is provided with the ultrasonic oscillating means, the ultrasonic receiving means, the time gate creating means, the noise presence / absence determining means, and the detection area determining means. It is possible to determine whether the received signal is due to reflected ultrasonic waves or noise due to the number of time gates to which the received signal is input, prevent malfunction due to noise, and correctly detect only obstacles.

[Brief description of drawings]

FIG. 1 is a block diagram of an obstacle detection device for an automated guided vehicle according to an embodiment of the present invention, and FIGS. 2 (a) and 2 (b) are schematic views showing a state where the automated guided vehicle according to the present invention approaches an obstacle. FIG. 3 is a side view, FIG. 3 is a chart of a reception signal when a reflected ultrasonic wave from an obstacle is normally received, FIG. 4 is a chart of a reception signal when air blow noise is mixed, and FIG. 5 is a Japanese patent publication No. 55-21315. FIG. 4 is a waveform diagram showing the concept of signal processing in the device disclosed in the publication. 1 ... Automated guided vehicle 2 ... Transmission / reception oscillator 3 ... Obstacle 4 ... Transmission frequency creation circuit 5 ... Oscillation cycle creation circuit 6 ... Transmission drive circuit 7 ... Filter 8 ... Amplifier 9 ... … Detection area judgment circuit 10 …… Reference gate creation circuit 11 …… Time gate creation circuit 12 …… Wheels 13 …… Motor n ₁ … n _m … Time gate M, m ₁ … m _m … Detection area

Claims (1)

[Claims] 1. An ultrasonic wave oscillating means for oscillating an ultrasonic wave forward of an automated guided vehicle, and an ultrasonic wave oscillated by the ultrasonic wave oscillating means is reflected by an obstacle and returned. Ultrasonic wave reception means, time gate creation means for creating a plurality of consecutive time gates corresponding to a detection area formed by virtually dividing the space in front of the automated guided vehicle into a plurality, and created by the time gate creation means Noise presence / absence determining means for determining whether or not the received signal includes noise according to the number of time gates to which the received signal received by the ultrasonic wave receiving means of the plurality of time gates is input, An unmanned conveyance comprising: a detection area determining unit that determines from which detection area the received signal of the reflected ultrasonic wave is based on which time gate of the plurality of time gates is input. Of obstacle detection devices.