JP7394699B2 - mechanical equipment - Google Patents

Description

The present invention relates to a mechanical device that detects the presence or absence of an object.

Conventionally, photoelectric switches have been widely used to detect the presence or absence of an object (see, for example, Patent Document 1). By attaching this photoelectric switch to the tip of the arm portion of the robot arm, the robot arm can detect objects that are present in front of it.

Japanese Patent Application Publication No. 10-154450

However, since the photoelectric switch has a narrow light irradiation range (optical path range), the range in which it can detect objects is also narrow. Therefore, in conventional robot arms, errors in detecting objects are likely to occur due to vibration of the arm portion, and improvements are required.

Note that this problem is not only a problem that exists only in the robot arm as described above, but also a problem that similarly exists in other mechanical devices (for example, a transfer device) having an arm portion to which a photoelectric switch is attached.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to provide a mechanical device that can reduce detection errors of objects compared to the conventional configuration.

The mechanical device according to the present invention includes an arm portion and a plurality of linearly arranged vibrations on the distal end surface of the arm portion in a direction perpendicular to a direction in which main vibrations are expected to occur on the distal end side of the arm portion. The transmitting/receiving unit includes a transmitting/receiving unit having an ultrasonic element, and an object detecting unit that detects the presence or absence of an object based on the results of transmission and reception by the transmitting/receiving unit. It is characterized by forming a two-dimensional circular wave in a plane including the direction in which vibration is expected to occur.

According to the present invention, with the above configuration, it is possible to reduce object detection errors compared to the conventional configuration.

1 is a diagram showing a configuration example of a robot arm according to Embodiment 1. FIG. 1 is a diagram showing a configuration example of an ultrasonic sensor in Embodiment 1. FIG. 3A and 3B are diagrams showing a configuration example of the ultrasonic element (PMUT) in Embodiment 1, in which FIG. 3A is a top view and FIG. 3B is a cross-sectional view taken along the line AA. 5 is a flowchart showing an example of the operation of the ultrasonic sensor in the first embodiment. 5A and 5B are diagrams showing an example of ultrasonic waves transmitted by the ultrasonic sensor in Embodiment 1, in which FIG. 5A is an XZ plan view and FIG. 5B is a YZ plan view. 6A and 6B are diagrams illustrating the effects of the robot arm according to the first embodiment, FIG. 6A is a diagram illustrating an example of an object detectable range in a conventional robot arm, and FIG. 6B is a diagram illustrating the effect of the robot arm according to the first embodiment. FIG. 3 is a diagram showing an example of an object detectable range in the robot arm according to the first embodiment. 7A and 7B are diagrams showing other examples of ultrasonic waves transmitted by the ultrasonic sensor in Embodiment 1, in which FIG. 7A is an XZ plan view and FIG. 7B is a YZ plan view. 7 is a diagram showing a configuration example of an ultrasonic sensor in Embodiment 2. FIG. FIG. 7 is a diagram showing a configuration example of an ultrasonic sensor in Embodiment 3.

Embodiments of the present invention will be described in detail below with reference to the drawings.
Embodiment 1.
FIG. 1 is a diagram showing an example of the configuration of a robot arm according to the first embodiment.
The robot arm (mechanical device) includes an arm portion 1 and an ultrasonic sensor 2, as shown in FIG. In FIG. 1, only an ultrasonic element 211, which will be described later, of the configuration of the ultrasonic sensor 2 is shown.

The arm section 1 moves according to control by a control section (not shown). Note that in FIG. 1, only the tip portion of the arm portion 1 included in the robot arm is illustrated. In addition, vibrations occur on the distal end side of the arm portion 1 due to movement or the like.

The ultrasonic sensor 2 detects an object present in front of the arm section 1. As shown in FIG. 2, the ultrasonic sensor 2 includes a transmitting/receiving section 21 and an object detecting section 22.

The transmitting/receiving section 21 transmits and receives ultrasonic waves to and from the front of the arm section 1 . The transmitting/receiving section 21 includes a plurality of ultrasonic elements 211, as shown in FIG. The plurality of ultrasonic elements 211 are arranged linearly on the distal end surface of the arm portion 1 . At this time, the plurality of ultrasonic elements 211 are arranged in a direction perpendicular to the direction in which main vibrations are expected to occur on the distal end side of the arm portion 1. FIG. 1 shows a case where it is assumed that main vibration occurs in the Y-axis direction at the tip side of the arm part 1, and two ultrasonic elements 211 (ultrasonic elements 211a, 211b) are arranged in the X-axis direction. There is.

This transmitting/receiving unit 21 is constructed by emitting ultrasonic waves from the plurality of ultrasonic elements 211 to form one plane in three-dimensional space (a plane including the direction in which main vibration is expected to occur on the tip side of the arm unit 1). A two-dimensional circular wave is formed at In FIG. 1, the transmitter/receiver 21 forms a two-dimensional circular wave in the YZ plane.

As the ultrasonic element 211, for example, MUT (Micromachined Ultrasonic Transducers) is used. The MUT is a minute ultrasonic element constructed using MEMS (Micro Electro Mechanical Systems) semiconductor manufacturing technology.
MUTs include PMUTs (Piezoelectric Micromachined Ultrasonic Transducers) and CMUTs (Capacitive Micromachined Ultrasonic Transducers). FIG. 3 shows a configuration example of a PMUT as an example of the ultrasonic element 211.

PMUT is a piezoelectric ultrasonic element. As shown in FIG. 3, this PMUT includes a semiconductor substrate 2111, a piezoelectric element (piezoelectric film) 2112, an electrode 2113, and an electrode 2114.

A groove is provided in a part of the lower surface of the semiconductor substrate 2111, so that a diaphragm 2115, which is a thin film, is formed.
The piezoelectric element 2112 is stacked on the diaphragm 2115 on the semiconductor substrate 2111.
The electrode 2113 is connected to the upper surface of the piezoelectric element 2112 (the surface opposite to the diaphragm 2115 side).
The electrode 2114 is connected to the lower surface of the piezoelectric element 2112 (the surface on the diaphragm 2115 side).

In the PMUT configured in this way, when a voltage is applied to the piezoelectric element 2112 by the electrodes 2113 and 2114, the piezoelectric element 2112 expands and contracts, the diaphragm 2115 vibrates accordingly, and the diaphragm 2115 is displaced. Ultrasonic waves are transmitted due to the pressure difference created by the
Furthermore, when an ultrasonic wave arrives from the outside, the PMUT vibrates the diaphragm 2115 due to the ultrasonic wave, which causes a potential difference between the electrodes of the piezoelectric element 2112, and receives the ultrasonic wave by detecting this potential difference. .

On the other hand, CMUT is an electrostatic type ultrasonic element. This CMUT is different from the PMUT in that it uses electrostatic attraction as a drive method and uses a capacitor as an output method, but the basic operating principle using a diaphragm is the same.

The object detection unit 22 detects the presence or absence of an object in front of the robot arm based on the results of transmission and reception by the transmission and reception unit 21.
In addition to the above object detection function, the object detection section 22 has a function of detecting the distance from the robot arm (the tip of the arm section 1) to the object when the object is within the detectable range. You can leave it there. In this case, when the object detection section 22 determines that there is an object within the detectable range, the object detection section 22 detects the object based on the time from when the transmitter/receiver section 21 transmits the ultrasonic wave until it receives the ultrasonic wave reflected by the object. to detect the distance to the object.

Note that the object detection unit 22 is realized by a processing circuit such as a system LSI (Large Scale Integration), or a CPU (Central Processing Unit) that executes a program stored in a memory or the like.

Next, an example of the operation of the ultrasonic sensor 2 in the first embodiment shown in FIG. 2 will be described with reference to FIG. 4.
In the operation example of the ultrasonic sensor 2 in the first embodiment shown in FIG. 2, first, the transmitter/receiver 21 transmits ultrasonic waves to the front of the arm portion 1 (step ST401). At this time, in the transmitting/receiving unit 21, the plurality of ultrasonic elements 211 emit ultrasonic waves, so that one surface in three-dimensional space (including the direction in which the main vibration is assumed to occur on the tip side of the arm part 1) A two-dimensional circular wave is formed in the plane).

In FIG. 5, two ultrasonic elements 211 (ultrasonic elements 211a, 211b) are arranged on the X-axis, and the two ultrasonic elements 211 simultaneously emit ultrasonic waves (spherical waves) in the Z-axis direction. It shows. In this case, as shown in FIG. 5A, on the XZ plane, the ultrasound waves interfere on the center line of the two ultrasound elements 211, and an ultrasound beam is formed. On the other hand, as shown in FIG. 5B, a two-dimensional circular wave is formed on the YZ plane. In FIG. 5, reference numeral 501 indicates an ultrasonic beam, and reference numeral 502 indicates a two-dimensional circular wave.

Next, the transmitter/receiver 21 receives ultrasonic waves (step ST402).

Next, the object detection section 22 detects the presence or absence of an object based on the results of transmission and reception by the transmission and reception section 21 (step ST403). Furthermore, when the object detection section 22 determines that there is an object within the detectable range, the object detection section 22 performs a The distance to the object may also be detected.

Here, in the robot arm, vibration at the tip of the arm section 1 is unavoidable due to the shape and elasticity of the arm section 1. This vibration of the arm portion 1 is one of the causes of object detection errors. Therefore, in the robot arm according to the first embodiment, by using a two-dimensional circular wave, the detectable range is expanded in the direction in which main vibrations are expected to occur in the arm section 1, compared to the conventional configuration. (See Figure 6). As a result, this robot arm can reduce object detection errors due to vibrations of the arm section 1, compared to conventional robot arms. In FIG. 6, reference numeral 601 indicates an object existing in front of the robot arm, reference numeral 602 indicates a photoelectric switch, reference numeral 603 indicates the detectable range of an object in a conventional robot arm, and reference numeral 604 indicates an object existing in front of the robot arm. 2 shows the detectable range of objects in the robot arm according to the invention.

Note that the robot arm according to the first embodiment uses two-dimensional circular waves to expand the detectable range of objects, but the accuracy of the two-dimensional circular waves depends on the accuracy of the installation location of each ultrasonic element 211. affect. On the other hand, in the MUT, each ultrasonic element 211 can be arranged with high precision by photolithography. Therefore, by using the MUT as the ultrasonic element 211 included in the robot arm according to the first embodiment, it becomes possible to transmit highly accurate two-dimensional circular waves.

Although FIG. 5 shows a case where the minimum number of ultrasonic elements 211 is two, the number is not limited to this, and the number of ultrasonic elements 211 may be three or more. In FIG. 7, four ultrasonic elements 211 (ultrasonic elements 211a to 211d) are arranged on the X-axis, and the four ultrasonic elements 211 simultaneously emit ultrasonic waves (spherical waves) in the Z-axis direction. It shows. Although FIG. 7 shows a case in which four ultrasonic elements 211 simultaneously emit ultrasonic waves, the present invention is not limited to this. For example, first, two outer ultrasonic elements 211 (ultrasonic elements 211a, 211d) simultaneously emit Ultrasonic waves may be emitted, and then the two inner ultrasonic elements 211 (ultrasonic elements 211b, 211c) may simultaneously emit ultrasonic waves. In this case, as shown in FIG. 7A, on the XZ plane, the ultrasonic waves interfere on the center lines of the four ultrasonic elements 211, and an ultrasonic beam is formed. On the other hand, as shown in FIG. 7B, a two-dimensional circular wave is formed on the YZ plane. Note that, in general, increasing the number of ultrasonic elements 211 increases the amplitude of the ultrasonic waves, thereby improving the S/N. In FIG. 7, reference numeral 701 indicates an ultrasonic beam, and reference numeral 702 indicates a two-dimensional circular wave.

As described above, according to the first embodiment, the robot arm has the arm section 1 and the distal end surface of the arm section 1 in the direction in which the main vibration is assumed to occur on the distal end side of the arm section 1. is equipped with a transmitting/receiving section 21 having a plurality of ultrasonic elements 211 arranged in a straight line in a vertical direction, and an object detecting section 22 that detects the presence or absence of an object based on the results of transmission and reception by the transmitting/receiving section 21. When the ultrasonic element 211 emits ultrasonic waves, the section 21 forms a two-dimensional circular wave in a plane including the direction in which main vibrations are expected to occur. As a result, the robot arm according to the first embodiment can reduce object detection errors compared to the conventional configuration.

Embodiment 2.
FIG. 8 is a diagram showing a configuration example of the ultrasonic sensor 2 in the second embodiment. The ultrasonic sensor 2 according to the second embodiment shown in FIG. 8 has a signal detection section 23 and a vibration presence/absence estimation section 24 added to the ultrasonic sensor 2 according to the first embodiment shown in FIG. The rest of the configuration is the same as the robot arm according to the first embodiment, and only the different parts will be explained using the same reference numerals. Note that the ultrasonic element 211 is an MUT.

The signal detection unit 23 detects a signal having a frequency other than the drive frequency of the ultrasound emitted by the ultrasound element 211 based on the results of transmission and reception by the transmission and reception unit 21 . Note that the driving frequency of the ultrasonic wave is the resonance frequency of the ultrasonic element 211, and is, for example, 500 kHz.
The vibration presence/absence estimation section 24 estimates the presence or absence of vibration in the arm section 1 based on the signal detected by the signal detection section 23 .

Here, the MUT has a diaphragm due to its structure. Therefore, the MUT can receive not only ultrasonic waves but also signals other than the driving frequency of the ultrasonic waves, although weak, through this diaphragm. That is, when an MUT is used as the ultrasonic element 211, the ultrasonic element 211 can receive a signal due to vibrations generated in the arm section 1.
Therefore, when the ultrasonic element 211 is an MUT, the signal detection section 23 can detect a signal of a frequency other than the ultrasonic driving frequency, and the vibration presence/absence estimation section 24 can detect the presence or absence of the vibration in the arm section 1 based on the presence or absence of this signal. The possibility of the presence or absence of vibration can be detected.

Embodiment 3.
FIG. 9 is a diagram showing a configuration example of the ultrasonic sensor 2 in the third embodiment. The ultrasonic sensor 2 according to the third embodiment shown in FIG. 9 has a signal detection section 23 and a deterioration estimation section 25 added to the ultrasonic sensor 2 according to the first embodiment shown in FIG. The rest of the configuration is the same as the robot arm according to the first embodiment, and only the different parts will be explained using the same reference numerals. Note that the ultrasonic element 211 is an MUT.

The signal detection unit 23 detects a signal having a frequency other than the drive frequency of the ultrasound emitted by the ultrasound element 211 based on the results of transmission and reception by the transmission and reception unit 21 . This signal detection section 23 is the same as the signal detection section 23 in the second embodiment.
The deterioration estimation section 25 estimates the deterioration of the arm section 1 by monitoring the signal detected by the signal detection section 23. At this time, the deterioration estimation unit 25 estimates the deterioration using, for example, machine learning using past data.

Here, the arm portion 1 vibrates differently depending on whether it is in a new state or in a deteriorated state. Therefore, the deterioration estimation section 25 can diagnose the deterioration state of the arm section 1 by analyzing the vibration of the arm section 1 based on the signal detected by the signal detection section 23 using machine learning or the like.

Note that the above description shows a case in which the signal detection section 23 and the deterioration estimation section 25 are added to the ultrasonic sensor 2 in the first embodiment shown in FIG. However, the present invention is not limited to this, and a deterioration estimating section 25 may be added to the ultrasonic sensor 2 in the second embodiment shown in FIG.

Furthermore, in the first to third embodiments, the mechanical device is a robot arm. However, the present invention is not limited thereto, and the mechanical device may be any device as long as it has an arm portion 1 to which the ultrasonic sensor 2 is attached, and may be a transport device, for example.

Furthermore, within the scope of the invention, the present invention allows for free combinations of the embodiments, modification of any component of each embodiment, or omission of any component in each embodiment. be.

1 Arm section 2 Ultrasonic sensor 21 Transmission/reception section 22 Object detection section 23 Signal detection section 24 Vibration presence/absence estimation section 25 Deterioration estimation section 211 Ultrasonic element 2111 Semiconductor substrate 2112 Piezoelectric element 2113 Electrode 2114 Electrode 2115 Diaphragm

Claims (4)

The arm part and
a transmitting/receiving section having a plurality of ultrasonic elements arranged linearly in a direction perpendicular to a direction in which main vibrations are expected to occur on the distal end side of the arm section on the distal end surface of the arm section;
an object detection unit that detects the presence or absence of an object based on the transmission and reception results by the transmission and reception unit,
A mechanical device characterized in that the transmitting/receiving unit forms a two-dimensional circular wave in a plane including a direction in which the main vibration is assumed to occur, by the ultrasonic element emitting ultrasonic waves. The mechanical device according to claim 1, wherein the ultrasonic element is a MUT. a signal detection unit that detects a signal of a frequency other than the drive frequency of the ultrasound emitted by the ultrasonic element based on the transmission and reception results by the transmission and reception unit;
The mechanical device according to claim 2, further comprising a vibration presence/absence estimating section that estimates the presence or absence of vibration in the arm section based on the signal detected by the signal detection section. a signal detection unit that detects a signal of a frequency other than the drive frequency of the ultrasound emitted by the ultrasonic element based on the transmission and reception results by the transmission and reception unit;
The mechanical device according to claim 2 or 3, further comprising a deterioration estimating section that estimates deterioration of the arm section by monitoring the signal detected by the signal detecting section.

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