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[Industrial field of application] The present invention is mounted on a robot or various industrial
devices, and measures the distance to a target object at a relatively short distance, or recognizes
the size and shape of the target object. The present invention relates to an array-type ultrasonic
proximity sensor used in 2. Description of the Related Art In recent years, inexpensive and highperformance microcomputers have become widespread, and automation or robotization is being
promoted in various industrial fields by using them. However, robots or automatic devices that
are currently put to practical use can only lift and carry objects of a certain shape, a certain size,
or a certain weight, or work such as processing 1 assembly only by means of a certain program.
The current situation is that it can not be done. On the other hand, diversification of the
consumer segment has made the trend of high-mix low-volume production stronger, and the
development of automation technology called FMS (Flexible Manufacturing System) has been
called for. In such a flow of automation, it is necessary to equip a robot or an automatic machine
with various sensors replacing human sense organs and to perform appropriate control based on
such information. Assuming that the robot lifts an object, first the object is found by the visual
sensor, then it approaches the object with the help of the proximity sensor, and finally the
hardness and the object of the object by the tactile sensor Measure the repulsive force etc. when
grabbing an object, and move the object while controlling the grasping power. Among the
sensors that assist these tasks, the proximity sensor is considered to have a role such as
measurement of distance information which is difficult with a visual sensor and high-speed
object capture. Although various types of proximity sensors have been proposed so far,
ultrasonic sensors are considered to be superior in -C. [Problems to be Solved by the Invention]
As an example of the ultrasonic sensor, there is an array type ultrasonic sensor described in
Japanese Patent Application No. 60-289290 as shown in FIG. 4 (a) is a plan view of the array
type ultrasonic sensor, and FIG. 4 (b) is a sectional view taken along the line AB. The structure of
the sensor unit of this array type ultrasonic sensor is simple, and an organic material such as a
polyester film or the like in which metal 405 is vapor deposited on one side on electrodes 403
arranged in an array on silicon substrate 401 via silicon oxide film 402 It is a simple structure in
which a film 404 is attached. In such an array type ultrasonic sensor in which a plurality of
ultrasonic elements are arranged in an array, the air layer trapped between the arrayed
electrodes 403 and the organic film 404 is vibrated by electrostatic force to It can transmit
sound waves.
Further, the ultrasonic waves propagated in the air vibrate the organic film 404 and can detect
ultrasonic waves by detecting a change in volume with the array electrode 403. Driving an
ultrasonic sensor of this type requires an AC signal with a large voltage during ultrasonic wave
transmission, while capturing very minute membrane vibration during ultrasonic wave reception
and amplifying it to a level necessary for signal processing A high sensitivity amplifier with less
noise is needed. Conventionally, in order to perform such an operation with one array type
ultrasonic sensor, as shown in FIG. 5, the transmitting side signal processing circuit 501 and the
receiving side signal processing circuit 502 for each ultrasonic element 504 And switchably
connect these signal processing circuits to the ultrasonic element 504 via the switch 503,
connect each transmission side signal processing circuit 501 to the signal source 505, and add
each reception side signal processing circuit 502. The transmission side signal processing circuit
501 and the reception side signal processing circuit 502 are used by switching between
transmission and reception. In this type of array type ultrasonic sensor, a large amplitude AC
signal at the time of ultrasonic wave transmission leaks into the wave receiving circuit, and in
order to avoid it, a sufficient time margin for switching between the wave transmission time and
the wave reception time It is necessary to have it, and there is also a time delay for switching of
the switch, which has impeded the improvement of the near distance measurement performance
of the array type ultrasonic sensor. For example, when five sine waves with a frequency of 100
kHz (wavelength 3.4 mm) were emitted and distance measurement was performed, the distance
could be measured only up to about 100 mm to the object. An object of the present invention is
to provide an array-type ultrasonic proximity sensor capable of eliminating the above-mentioned
conventional drawbacks and improving the near distance measurement performance. [Means for
Solving the Problems] The present invention relates to an array-type ultrasonic proximity sensor
capable of transmitting and receiving ultrasonic waves, in which some of the ultrasonic elements
constituting the array are connected to the output unit. It is characterized in that a source
follower circuit is built in, the part of the ultrasonic elements is dedicated to receiving ultrasonic
waves, and the other ultrasonic elements are dedicated to transmitting waves. [Operation]
According to the principle of the present invention, the ultrasonic wave transmitting element and
the ultrasonic wave receiving element are shared by the large number of ultrasonic elements
constituting the array type ultrasonic proximity sensor, and the ultrasonic wave receiving
element is used as the wave receiving element. Is that the source follower circuit is built in the
output part. As a result, it becomes possible to connect a drive circuit for generating an AC signal
of large amplitude to the transmitting element without interference between the elements, and to
connect a low noise high sensitivity amplifier to the receiving element. . That is, since the circuits
of the ultrasonic wave transmitter and receiver are completely separated, the drive signal does
not leak into the signal amplifier circuit, and both circuits can be driven at the same time. It is
possible to measure a short distance in a short time before receiving a reflected wave.
Further, since the source follower circuit is built in the output part of the wave receiving element,
the signal subjected to impedance conversion is input to the amplifier circuit with a sufficient S /
N ratio. EXAMPLES The present invention will be described based on examples. FIG. 1 is a
schematic block diagram of an array-type ultrasonic proximity sensor for detailed explanation of
the present invention. A total of 32 elements are arranged on the p-type silicon substrate 101 by
alternately receiving 16 elements of the receiving side ultrasonic elements 102 and transmitting
side ultrasonic elements 103. Near the electrode output pads of the wave receiving ultrasonic
element 102, an impedance conversion circuit composed of MOS FETs as shown in FIGS. 2 (a)
and 2 (b) is formed. 2 (a) shows the configuration of the impedance conversion circuit unit, and
FIG. 2 (b) shows its equivalent circuit. In FIG. 2, the first transistor 201 is a depletion type MOS
FET that receives an ultrasonic wave reception signal with high impedance. On the other hand,
the second transistor 202 works as a load resistance. These transistors were first formed on a
silicon substrate in a standard manufacturing process, and then formed an ultrasonic sensor as
shown in FIG. However, the gate of the first transistor 201 was simultaneously formed after the
electrode formation of the receiving ultrasonic element. In FIG. 2A, reference numeral 203
denotes an ultrasonic wave receiving element electrode, and reference numeral 204 denotes an
output pad of the wave receiving side ultrasonic element. In FIG. 2 (b), reference numeral 205
denotes an output unit, and 206 denotes a receiving-side ultrasonic element. FIG. 3 is a final
block diagram of the array type ultrasonic proximity sensor obtained in this manner. In the
figure, reference numeral 301 denotes a transmission side ultrasonic element. A signal
processing circuit 302 on the transmission side is connected to each transmission side ultrasonic
element, and these signal processing circuits are connected to a signal source 303. A
programmable delay circuit is formed in the signal processing circuit 302 in order to operate the
array-type ultrasonic proximity sensor of this embodiment for the purpose of electronically
scanning the ultrasonic beam in a fan-shape. On the other hand, in the figure, 304 is a receiving
side ultrasonic element, and the impedance converting circuit 305 comprised of the MOSFET
described in FIG. 2 is connected to each receiving side ultrasonic element, and each impedance
converting circuit is connected. The signal processing circuit 306 on the receiving side is
connected, and these signal processing circuits are connected to the adder 307. The signal
processing circuit 306 comprises a low noise amplifier, a delay circuit and the like. The delay
circuit receives a signal returned from an ultrasonic scan beam by an electronic scan reflected
back to the object, and performs delay processing reverse to that at the time of transmission to
combine the signals from the respective ultrasound elements. is necessary.
An ultrasonic distance measurement experiment was conducted using the cisnum of FIG. The
signal frequency is 100kllz (wavelength 3.44mm) and five sine waves are emitted. First,
ultrasonic waves are transmitted with the same phase of all transmission side ultrasonic
elements, and the received signal is measured with an oscilloscope using the distance to the
object ahead I observed it. As a result, it became clear that even when the object is close to the
distance of 10 mm, it can be measured with a sufficient S / N ratio. It is apparent that a sufficient
drop is obtained as compared to the distance measurement method by the conventional
ultrasonic sensor. Next, the distance measurement experiment by fan-shaped scanning of the
ultrasonic beam was conducted by changing the phase of each transmission side ultrasonic
element. In the case of an electronic scan of about ▒ 30 degrees, the distance to a close object of
about 101 could be measured with the same result. Initially, it was feared that the reach of the
ultrasonic beam would be extremely deteriorated due to the decrease of the transmission power
by dividing the array type ultrasonic element into transmission and reception, but the influence is
about 10%, and the deterioration is It is also clear that the interference is reduced by the
transmission / reception ultrasonic elements and the S / N ratio at the time of reception is
improved by the cancellation. In the above embodiments, although the impedance conversion
circuit has been described as an example configured with a MOS type FET, it can be generally
configured with a MIS type FET. Moreover, it can also be comprised by FET of junction type
instead of MIS type. [Effects of the Invention] As described above, when the array type ultrasonic
proximity wedge sensor having the structure of the present invention is used, distance
measurement performance at a short distance can be improved. Also, since the S / N ratio at the
time of wave reception is improved, processing such as averaging becomes unnecessary in signal
processing after final waveform synthesis, that is, image processing such as detection of a twodimensional distance image, and overall processing The time shortening effect was also obtained.
In addition, the time and effort of providing a large number of switches at the time of assembly
also improved the reliability.
Brief description of the drawings
FIG. 1 is a schematic configuration view of an array type ultrasonic proximity sensor according to
an embodiment of the present invention, and FIG. 2 is a diagram showing an impedance
conversion circuit provided in the vicinity of an output portion of a receiving ultrasonic element.
3 shows a distance measurement system using the array type ultrasonic proximity sensor of
FIGS. 1 and 2, FIG. 4 shows a conventional array type ultrasonic proximity sensor, and FIG. 5
shows FIG. It is a figure which shows the ranging system using the array-type ultrasonic
proximity sensor of FIG.
102) 304: receiving side ultrasonic element 103, 301: transmitting side ultrasonic element 201:
first transistor 202: second transistor 302: transmitting Side signal processing circuit 303 ииииии
Signal source 305 ииииии Impedance conversion circuit 306 ииииии Reception side signal processing
circuit 307 иииииииии Adder
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14 Кб
jps63113380, description
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