JP6261699B1 - Ultrasonic encoder and position detection method using the same - Google Patents

Abstract

An ultrasonic encoder capable of eliminating an error caused by a position conversion device, reducing a calculation load, and detecting a position of an object with high accuracy and a position detection method using the same are provided. A guide rail, a plurality of ultrasonic elements, and a calculation device are provided. The guide rail 12 has a detection surface 12a extending along the moving direction A of the object W, and an ultrasonic wave reflection source 13 positioned at a predetermined depth from the detection surface 12a. The plurality of ultrasonic elements 14 are configured to be fixed to the object W and movable in contact with the detection surface 12a. The calculation device 16 receives the reflected echoes from the ultrasonic reflection source 13 by vertical flaw detection by the plurality of ultrasonic elements 14 and calculates the position of the object W from the plurality of half paths Z of the reflected echoes. [Selection] Figure 1

Description

  The present invention relates to an ultrasonic encoder that detects the position of an object using ultrasonic waves, and a position detection method using the ultrasonic encoder.

  Position detection encoders (linear encoders and rotary encoders) are widely known as devices for detecting the position of an object. These position detection encoders are composed of a scale (scale) that serves as a reference for the position and a head (detector) that detects position information from the scale. These position detection encoders include an optical type that uses light for detection and a magnetic type that uses magnetism. There are an absolute type that performs absolute position measurement and an incremental type that measures relative position.

  A conventional rotary encoder is disclosed in Patent Document 1, for example.

  On the other hand, a position detection encoder using ultrasonic waves is disclosed in Patent Document 2.

  In the configuration disclosed in Patent Document 1, an ultrasonic probe for inspecting a workpiece is rotated via a gear train (power gear, intermediate gear, and circumferential rotation gear), and the rotation detection encoder rotates the intermediate gear. Is detected to obtain the rotational position of the ultrasonic probe.

  The “one-dimensional transducer array” disclosed in Patent Document 2 is different for each of two or more orthogonal codes so that ultrasonic waves from one one-dimensional transducer array are focused on two or more planes. This adds a transmission delay.

JP 2001-74712 A JP 2013-255806 A

  At present, phased array UT inspection (UPA) and advanced UT technology are required to acquire position information at the same time as inspection, and to acquire data that makes the inspection result and position information correspond one-to-one.

In order to satisfy this demand, the above-described optical or magnetic position detection encoder (hereinafter, “conventional position detection encoder”) is generally used.
However, a conventional position detection encoder includes a scale having a precisely formed pattern and a head that optically or magnetically detects the pattern, and it is necessary to accurately move the head along the scale.
Therefore, these position detection encoders are configured as devices including a guide mechanism for accurately moving the head with respect to the scale.
When detecting the position of an object using such a position detection encoder, it is necessary to prepare a position conversion device that fixes a guide mechanism including a scale to a fixed portion and converts the movement of the object into movement of the head. is there.

Such a position conversion device includes, for example, a gear train disclosed in Patent Document 1, a link mechanism, a wire and a pulley, or the like. Therefore, it is difficult to accurately convert the movement of the object into the movement of the head, and errors due to backlash, backlash, wire elongation, and the like occur.
In addition, such a position conversion device is usually large, and may be difficult or substantially impossible to apply, for example, when a circumferential weld of a small diameter pipe is inspected by ultrasonic waves.

On the other hand, in the case of the “one-dimensional transducer array” disclosed in Patent Literature 2, focusing is performed by electronically switching or steering an ultrasonic beam using generally 64 to 256 transducer array elements. .
However, with this means, a large number of transducer array elements are driven simultaneously, so that the driving load is large, and the data to be simultaneously processed is heavy, so the calculation load is large and the calculation time is long. Moreover, the range that can be acquired is only the effective range of the probe, and a wide range cannot be covered. In order to acquire a wide range of layers, it is necessary to acquire data in accordance with the amount of movement of the object by an encoder or the like.

  The present invention has been developed to solve the above-described problems. That is, an object of the present invention is to provide an ultrasonic encoder that can eliminate an error caused by the position conversion device, reduce a calculation load, and can detect the position of an object with high accuracy, and a position detection method using the same. There is.

According to the present invention, an ultrasonic encoder that detects the position of an object using ultrasonic waves,
A guide rail having a detection surface extending along the moving direction of the object, and an ultrasonic wave reflection source positioned at a predetermined depth from the detection surface;
A plurality of ultrasonic elements fixed to the object and movable in contact with the detection surface;
Receiving reflected echoes from the ultrasound reflection source by vertical flaw detection by a plurality of the ultrasonic elements, respectively, and an arithmetic device that calculates the position of the object from a plurality of half paths of the reflected echo ,
A plurality of the ultrasonic reflection sources are positioned at a first interval in the moving direction;
The ultrasonic encoders are arranged in a range of a second distance exceeding the first interval along the moving direction, and spaced apart from each other by a pitch smaller than the first interval by one digit or more. Provided.

An ultrasonic array element having a plurality of the ultrasonic elements;
The position of the object is calculated by aperture synthesis of a plurality of reflected echoes.

  A detection holder is provided that is fixed to the object, holds the ultrasonic array element, and is movable along the guide rail.

  The plurality of ultrasonic reflection sources are linear reflection sources extending in parallel with the detection surface in a plane orthogonal to the moving direction.

  The guide rail is a linear member extending linearly in the moving direction.

  The guide rail is an arc member extending in an arc shape in the moving direction.

According to the present invention, there is provided a position detection method for detecting the position of the object using the ultrasonic encoder described above,
(A) positioning a plurality of the ultrasonic elements in contact with the detection surface of the guide rail;
(B) Receiving reflected echoes from the ultrasonic reflection source by vertical flaw detection using a plurality of the ultrasonic elements,
(C) detecting a plurality of the half paths of each ultrasonic element from the reflected echo,
Calculate the intersection coordinates of a plurality of circles centered on the ultrasonic incident point of each ultrasonic element and having the half path as a radius,
A position detection method is provided in which the position of the object is calculated by detecting the largest number of coordinates in the movement direction among the calculated intersection coordinates .

Preparing an ultrasonic array element having a plurality of the ultrasonic elements;
In (C), the position of the object is calculated by aperture synthesis of the plurality of reflected echoes.

In the above (C),
Detecting a plurality of the half paths of each ultrasonic element from the reflected echo;
Calculate the intersection coordinates of a plurality of circles centered on the ultrasonic incident point of each ultrasonic element and having the half path as a radius,
Among the calculated intersection coordinates, the largest number of coordinates in the moving direction is detected.

According to the present invention, the guide rail has the detection surface extending along the moving direction of the object, and the ultrasonic wave reflection source positioned at a predetermined depth from the detection surface. In addition, a plurality of ultrasonic elements are fixed to the object, and are configured to be movable in contact with the detection surface.
Therefore, since the plurality of ultrasonic elements are fixed to the object, a position conversion device (for example, a gear train) that converts the movement of the object into the movement of the plurality of ultrasonic elements is unnecessary. Errors can be eliminated.

In addition, according to the present invention, there is provided an arithmetic device that receives reflected echoes from an ultrasonic wave reflection source by vertical flaw detection using a plurality of ultrasonic elements, and calculates the position of an object from a plurality of half paths of the reflected echoes.
Accordingly, since the arithmetic device sequentially drives the plurality of ultrasonic elements and receives the reflected echoes, the arithmetic load can be reduced and the arithmetic time can be shortened.

  Furthermore, according to the present invention, since aperture synthesis of a plurality of reflected echoes can be applied, the position of the object can be detected with high accuracy using ultrasonic waves.

1 is an overall configuration diagram of an ultrasonic encoder according to a first embodiment of the present invention. It is a figure which shows the principal part of FIG. FIG. 3 is a principle diagram of the present invention and is a partially enlarged view of FIG. 2. It is a figure which shows an example of a reflective echo. It is a figure which shows the relationship between an element position and a half pass. It is explanatory drawing of aperture synthesis. It is a whole block diagram of the ultrasonic encoder of 2nd Embodiment by this invention. It is a whole flowchart of the position detection method by this invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In each figure, common portions are denoted by the same reference numerals, and redundant description is omitted.

FIG. 1 is an overall configuration diagram of an ultrasonic encoder 10 according to a first embodiment of the present invention, where (A) is a side view and (B) is a BB cross-sectional view of (A).
The ultrasonic encoder 10 of the present invention is a position detection encoder that detects the position of the object W using ultrasonic waves.

  In FIG. 1, the ultrasonic encoder 10 of the present invention includes a guide rail 12, a plurality of ultrasonic elements 14, and a calculation device 16.

  The guide rail 12 has a detection surface 12a extending along the moving direction A of the object W, and an ultrasonic wave reflection source 13 positioned at a predetermined depth from the detection surface 12a.

  The object W is an ultrasonic device for ultrasonically inspecting, for example, a welded part of a workpiece (not shown). Note that the object W is not limited to the ultrasonic apparatus, and may be other inspection equipment.

  In FIG. 1, the guide rail 12 is a linear member that extends linearly in the moving direction A of the object W. The guide rail 12 is not limited to a linear member, and may be an arc member extending in an arc shape in the moving direction A.

In FIG. 1, the cross-sectional shape of the guide rail 12 is a rectangle, and has a detection surface 12a and a bottom surface 12b in the vertical direction in FIG. In this example, the detection surface 12a and the bottom surface 12b are configured to be parallel to each other.
Hereinafter, the moving direction A of the object W is defined as the X axis, and the thickness direction orthogonal to the X axis in FIG.

In this example, the plurality of ultrasonic reflection sources 13 are positioned at a first interval L1 in the moving direction A of the object W.
Further, the ultrasonic reflection source 13 of the present invention is not limited to a plurality, and may be a single.

  The ultrasonic reflection source 13 is a circular through-hole in this example, but the present invention is not limited to this, and may be another form, for example, a different material as long as the ultrasonic wave can be reflected. The diameter of the ultrasonic wave reflection source 13 is, for example, 2 to 3 mm, but may be 2 mm or less as long as the ultrasonic wave can be reflected.

In this example, the plurality of ultrasonic reflection sources 13 are linear reflection sources extending in parallel to the detection surface 12 a in a plane orthogonal to the movement direction A. The ultrasonic reflection source 13 is provided between the detection surface 12a and the bottom surface 12b.
The guide rail 12 has a preset origin O in the movement direction A, and the position (X coordinate) of each ultrasonic reflection source 13 from the origin O is accurately set in advance.

  The plurality of ultrasonic elements 14 are configured to be fixed to the object W and movable in contact with the detection surface 12a. The ultrasonic element 14 should just be at least 2 or more.

In this example, an ultrasonic array element 15 having a plurality of ultrasonic elements 14 is provided.
The ultrasonic array element 15 is fixed to the object W and is configured to be movable in contact with the detection surface 12 a of the guide rail 12.

  In this example, the ultrasonic encoder 10 of the present invention further includes a detection holder 18. The detection holder 18 is fixed to the object W, holds the ultrasonic array element 15, and is configured to be movable in the movement direction A along the guide rail 12.

In this example, the detection holder 18 has a guide surface 18 a that fits with the outer surface of the guide rail 12, and guides the object W and the ultrasonic array element 15 along the outer surface of the guide rail 12.
The detection holder 18 has a preset reference position G in the moving direction A, and the object W and the ultrasonic array element 15 are accurately positioned in advance with respect to the reference position G.

  The computing device 16 is, for example, a computer (PC), receives the reflected echoes from the ultrasonic reflection source 13 by vertical flaw detection by the plurality of ultrasonic elements 14, and positions the object W from the plurality of half paths Z of the reflected echoes. Is calculated.

FIG. 2 is a diagram showing a main part of FIG.
In this figure, a plurality of ultrasonic elements 14 (hereinafter referred to as elements 14) are arranged in a range of a second distance L2 exceeding the first distance L1 along the moving direction A, and one digit from the first distance L1. The small pitches P are separated from each other.
With this configuration, since the second distance L <b>2> the first interval L <b> 1, at least one element 14 among the plurality of elements 14 is positioned closest to one of the ultrasonic reflection sources 13.

FIG. 3 is a principle diagram of the present invention and is a partially enlarged view of FIG.
In this figure, the thickness T (for example, 10 mm) of the guide rail 12 and the distance y1 (for example, 6 mm) from the detection surface 12a of the ultrasonic wave reflection source 13 are known.
Hereinafter, for convenience of explanation, the seven elements 14 in this figure are a, b, c, d, e, f, and g in order from the left.

The arithmetic device 16 receives reflected echoes from the ultrasonic reflection source 13 by vertical flaw detection by the plurality of elements 14 constituting the ultrasonic array element 15.
The vertical flaw detection is a method of performing flaw detection by making an ultrasonic wave perpendicular to the detection surface 12a. Due to the vertical flaw detection, the ultrasonic wave incident from the detection surface 12a of the guide rail 12 propagates while spreading in the thickness direction, is reflected by the ultrasonic reflection source 13 and the bottom surface 12b of the guide rail 12, and is the same element 14 as a reflection echo. Is detected.

FIG. 4 is a diagram illustrating an example of a reflected echo. In this figure, the horizontal axis represents the half path Z and the vertical axis represents the intensity of the reflected echo.
The “half path” represents a propagation distance obtained by calculating the acquisition time from the incidence of an ultrasonic wave until acquisition of a reflected echo at the speed of sound. That is, the half path Z is a distance obtained from the incident point to the reflection point in consideration of reflection from the round-trip time (acquisition time) from the ultrasonic incident point to the ultrasonic reflection point.
In this case, the reflection points are the ultrasonic reflection source 13 and the bottom surface 12 b of the guide rail 12.

In FIG. 4, since the thickness T of the guide rail 12 and the depth y1 from the detection surface 12a of the ultrasonic reflection source 13 are known, the reflected echo from the ultrasonic reflection source 13 is reflected by the half path Z. It can be seen that it is in the vicinity of the depth of the source 13. In this example, it can be said that the half pass Z is in the range of 5 to 7 mm, for example.
Therefore, in this range, the half path Z at the position where the intensity of the reflected echo is maximum (indicated by the arrow B) corresponds to the distance between the element 14 and the ultrasonic reflection source 13.

FIG. 3 shows the half paths Z of the ultrasonic wave reflection source 13 detected by the elements a, b, c by broken double arrows a ′, b ′, c ′, respectively.
In this figure, the element b is closest to the left ultrasonic reflection source 13, and then the elements a and c are located close to each other.
By vertical flaw detection using a plurality of elements 14 (elements a, b, and c in this example), half paths a ′, b ′, and c ′ (that is, distances) from the elements a, b, and c to the ultrasonic reflection source 13 are calculated. can do.

  Accordingly, the ultrasonic array element 15 held by the detection holder 18 is moved in the X direction from the origin O provided on the guide rail 12 to detect the plurality of ultrasonic reflection sources 13 in order, thereby detecting the ultrasonic array. It can be seen which ultrasonic reflection source 13 the element 15 is currently detecting.

  Further, it is possible to detect from the size of the half path Z which element 14 is closest to the currently detected ultrasonic reflection source 13. Therefore, the position (ie, the object W) of the ultrasonic array element 15 can be detected with an accuracy (pitch P) that is one digit or more smaller than the first interval L1 by the arithmetic device 16 of the present invention.

When there are two elements 14, two circles having radii of the half paths Z1 and Z2 can be expressed by Equations (1) and (2) of Formula 1. Here, the positions of the two elements 14 are (x1, y1) and (x2, y2). X and Y are points on two circles.
The center of the two circles and the Y coordinate of the two elements 14 are the same, and if this is 0 (reference), the X coordinate of the intersection of the two circles can be expressed by equation (3).
Therefore, from the X coordinates of the two elements 14 and the half paths Z1 and Z2, the X coordinate of the ultrasonic reflection source 13 with respect to the element 14 can be obtained by Expression (3).

  Equations (1) to (3) are cases where the detection surface 12a of the guide rail 12 is a flat surface. In other cases, the X coordinate of the ultrasonic reflection source 13 with respect to the element 14 is obtained as an intersection of circles. be able to.

  FIG. 5 is a diagram showing the relationship between the element position and the half pass Z. In this figure, the horizontal axis represents the position of the element 14 constituting the ultrasonic array element 15, and the vertical axis represents the half path Z. In addition, white circles (◯) in the figure indicate the half paths Z of each element 14.

In this example, the ultrasonic array element 15 has 32 elements 14, and each element 14 has a second distance L <b> 2 (= 12.4 mm) exceeding the first interval L <b> 1 along the movement direction A. Has been placed. The elements 14 are spaced apart from each other by a pitch P (= 0.4 mm) that is one digit or more smaller than the first interval L1.
In this example, in the moving direction A, one of the ultrasonic reflection sources 13 and the element 14 at the element position 6 mm coincide.

  FIG. 6 is an explanatory diagram of aperture synthesis. As described above, the half path Z shown in FIG. 5 corresponds to the distance from each element to the ultrasonic reflection source 13.

The arithmetic device 16 of the present invention calculates the position of the ultrasonic array element 15 (that is, the object W) with respect to the guide rail 12 by aperture synthesis of the plurality of received reflection echoes.
That is, as shown in FIG. 6, the intersection coordinates of a plurality of circles having a radius of the half path Z of each element 14 are calculated, and among the calculated intersection coordinates, the coordinates in the movement direction A that are the largest (white circles (○ ) Is detected, the position of the ultrasonic array element 15 can be calculated.

FIG. 7 is an overall configuration diagram of the ultrasonic encoder 10 according to the second embodiment of the present invention.
In this example, the guide rail 12 has a hollow cylindrical shape, and is coaxially and detachably fixed to the outer peripheral surface 1 a of the hollow tube 1. That is, the guide rail 12 is an arc member extending in an arc shape in the moving direction A (the circumferential direction of the hollow tube 1).
The plurality of ultrasonic reflection sources 13 are linear reflection sources that extend in parallel to the detection surface 12a in a plane orthogonal to the moving direction A (in a radial plane).

In this example, the object W is a phased array probe, is fixed to the detection holder 18, and ultrasonically inspects a welded portion that is present near the surface of the hollow tube 1.
The ultrasonic array element 15 is fixed to a target object W (phased array probe) via a detection holder 18 and is configured to be movable in contact with the detection surface 12 a of the guide rail 12.
Other configurations are the same as those of the first embodiment.

  In this example, the ultrasonic array element 15 and the object W (phased array probe) are obtained by branching the same phased array probe. Further, the control cable 19a of the ultrasonic array element 15 and the control cable 19b of the object W are obtained by branching a single control cable 19 from the middle.

With this configuration, a single control cable 19 is connected to the same arithmetic unit 16, and the welded portion existing near the surface of the hollow tube 1 is ultrasonically inspected by the phased array probe, and at the same time, the inspection is performed. The location (the circumferential position in this example) can be detected by the ultrasonic encoder 10 of the present invention.
Therefore, the position information can be acquired by the ultrasonic encoder 10 simultaneously with the inspection by the phased array probe, and the inspection result and the position information can be made to correspond one-to-one.

FIG. 8 is an overall flowchart of the position detection method according to the present invention.
In this figure, the position detection method of the present invention comprises steps (steps) S1 to S3.
In step S <b> 1, the plurality of ultrasonic elements 14 (elements 14) are positioned in contact with the detection surface 12 a of the guide rail 12.
In step S <b> 2, reflected echoes from the ultrasonic reflection source 13 are received by vertical flaw detection by the plurality of elements 14.
In step S3, the position of the object W is calculated from a plurality of half paths Z of a plurality of reflected echoes.

  In step S3, it is preferable to prepare an ultrasonic array element 15 having a plurality of elements 14 and calculate the position of the object W by aperture synthesis of a plurality of reflected echoes.

That is, in FIG. 8, step S3 is composed of steps (processes) T1 to T3.
In step T1, a plurality of half paths Z of each element 14 are detected from the reflected echo.
In step T2, the intersection coordinates of a plurality of circles centered on the ultrasonic incident point of each element 14 and having a radius of the half path Z are calculated.
In step T3, the coordinate in the moving direction A that is the largest among the calculated intersection coordinates is detected.

According to the present invention described above, the guide rail 12 has the detection surface 12a extending along the moving direction A of the object W, and the ultrasonic wave reflection source 13 positioned at a predetermined depth from the detection surface 12a. Further, the plurality of ultrasonic elements 14 are fixed to the object W and configured to be movable in contact with the detection surface 12a.
Therefore, since the plurality of ultrasonic elements 14 are fixed to the object W, a position conversion device (for example, a gear train) for converting the movement of the object W into the movement of the plurality of ultrasonic elements 14 is unnecessary. Errors due to the position conversion device can be eliminated.

In addition, according to the present invention, the arithmetic device that receives the reflected echoes from the ultrasonic reflection source 13 by the vertical flaw detection by the plural ultrasonic elements 14 and calculates the position of the object W from the plural half paths Z of the reflected echoes. 16.
Therefore, since the arithmetic unit 16 sequentially drives the plurality of ultrasonic elements 14 and receives the reflected echoes, the arithmetic load can be reduced and the arithmetic time can be shortened.

  Furthermore, according to the present invention, since aperture synthesis of a plurality of reflected echoes can be applied, the position of the object W can be detected with high accuracy using ultrasonic waves.

  In addition, this invention is not limited to embodiment mentioned above, Of course, it can change variously in the range which does not deviate from the summary of this invention.

A movement direction, L1 first interval, L2 second distance, O origin, P pitch,
W object, y1 depth, Z, Z1, Z2 half pass,
10 ultrasonic encoder, 12 guide rail, 12a detection surface,
12b bottom surface, 13 ultrasonic reflection source (linear reflection source),
14 ultrasonic elements (elements), 15 ultrasonic array elements,
16 arithmetic unit (computer), 18 detection holder, 18a guide surface,
19, 19a, 19b Control cable

Claims (7)

An ultrasonic encoder that detects the position of an object using ultrasonic waves,
A guide rail having a detection surface extending along the moving direction of the object, and an ultrasonic wave reflection source positioned at a predetermined depth from the detection surface;
A plurality of ultrasonic elements fixed to the object and movable in contact with the detection surface;
Receiving reflected echoes from the ultrasound reflection source by vertical flaw detection by a plurality of the ultrasonic elements, respectively, and an arithmetic device that calculates the position of the object from a plurality of half paths of the reflected echo ,
A plurality of the ultrasonic reflection sources are positioned at a first interval in the moving direction;
The ultrasonic encoder , wherein the plurality of ultrasonic elements are arranged in a range of a second distance that exceeds the first interval along the moving direction, and are separated from each other by a pitch that is one digit or more smaller than the first interval . An ultrasonic array element having a plurality of the ultrasonic elements;
The ultrasonic encoder according to claim 1, wherein the position of the object is calculated by aperture synthesis of the plurality of reflected echoes.   The ultrasonic encoder according to claim 2, further comprising a detection holder that is fixed to the object, holds the ultrasonic array element, and is movable along the guide rail.   The ultrasonic encoder according to claim 1, wherein the plurality of ultrasonic reflection sources are linear reflection sources extending in parallel to the detection surface in a plane orthogonal to the moving direction.   The ultrasonic encoder according to claim 1, wherein the guide rail is a linear member extending linearly in the movement direction.   The ultrasonic encoder according to claim 1, wherein the guide rail is an arc member extending in an arc shape in the movement direction. A position detection method for detecting the position of the object using the ultrasonic encoder according to claim 1,
(A) positioning a plurality of the ultrasonic elements in contact with the detection surface of the guide rail;
(B) Receiving reflected echoes from the ultrasonic reflection source by vertical flaw detection using a plurality of the ultrasonic elements,
(C) detecting a plurality of the half paths of each ultrasonic element from the reflected echo,
Calculate the intersection coordinates of a plurality of circles centered on the ultrasonic incident point of each ultrasonic element and having the half path as a radius,
A position detection method for calculating the position of the object by detecting the largest number of coordinates in the movement direction among the calculated intersection coordinates .

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