SE2251275A1

SE2251275A1 - A displacement measuring method and a device for measuring a displacement of an object to be measured

Info

Publication number: SE2251275A1
Application number: SE2251275A
Authority: SE
Inventors: Daniel Granlund; John Karbin
Original assignee: Optiload Tech Ab
Priority date: 2022-11-01
Filing date: 2022-11-01
Publication date: 2024-05-02

Abstract

ABSTRACT The present invention relates to a displacement measuring method. The method comprises the following steps: locating an image capturing device at a distance from an object to be measured, locating a target having an information-containing pattern at a position of the object to be measured such that the pattern is in a displacement measuring direction relative the image capturing device, capturing a reference image of the pattern with the image capturing device and converting the reference image to a numeric reference value, capturing a measuring image of the pattern with the image capturing device and converting the measuring image to a numeric measuring value, ca|cu|ating the deviation between the different numeric values, and determining the displacement of the measured object. The invention also relates to a device for carrying out the displacement measuring method.

Description

Technical field

[0001] The present invention relates to a displacement measuring method of measuring of an object to be measured, such as a roof truss subjected to a snow load. The invention also relates to a displacement measuring device.

Background art

[0002] ln prior art, the bending that occurs on a roof truss when snow covers a roof, is measured with a measuring device, such as a ruler between the rooftruss and a solid object. The distance between the truss and the solid object is measured first before snovvfall, for example in the autumn, and after a snowfall once or several times during winter. This method may require personnel to enter hard-to-reach locations every time the measuring needs to be carried out and is also depending on which measuring points that are used. This means that the measuring may be inaccurate due to handling and that different rulers may be used by different people.

[0003] Another method is described in US2018/0164093. This method includes a projector which directs a laser or other trackable beam from an origin having a fixed location relative to the structure of a target surface configured to be fixed to the structural component. The beam strikes the target surface to produce a trackable spot at a location on the target surface. A camera coupled to the target surface tracks the position of the spot as it moves on the target surface over time in response to relative movement between the structural component and the origin. A computer processor receives data from the camera and calculates the magnitude of movement of the structural component relative to the origin.

[0004] This method needs proper environment to measure a movement of the structure to be measured. lt also comprises several devices to accomplish the measurement, such as a laser, a camera, and a computer. Furthermore, the target needs to be aligned with the laser beam, since the camera is attached to the {F1o} target, to be able to receive the projected laser beam. A camera is attached to the target, which means that two connections must be established, one with the laser and one with the camera in the target. This results in a complicated arrangement that needs calibration and alignment of the laser, the target, and the camera.

[0005] There are needs to conduct displacement measurement when measuring an object, such as a roof truss subjected to a snow load, that can be accomplished in an easier, more reliable, and secure way.

Summary of invention

[0006] The present invention provides a method and a device for measuring movement and displacement of an object or a structural component of a structure relative to another location of the structure. The method utilizes an image capturing device which is fixed or othen/vise coupled to the structure or a location adjacent the structure, a target attached to the object or structural component to be measured, the target containing information regarding the target as well as the object or structural component to be measured, and a converting and calculating component of the image capturing device to convert the captured images to numeric values and calculate the relative displacement.

[0007] The image capturing device can be fixed or othen/vise coupled to the structure at a point within the measuring area which will be expected to move less than the object to be measured or the structural component. ln the case of a roof truss, the fixed point can be a mount attached to a wall of a building. Alternatively, the fixed point can be located on a separate structure, such as the foundation of the building or other point expected to move less than the object to be measured. The image capturing device includes an invisible light illumination source, a filter for only capturing images in a specific wavelength and a wide-angle lens to capture images of several targets on different locations within the measuring area.

[0008] The target can be a patch, a sticker, or sticky note with an adhesive backside to be attached to the surface of the object to be measured. The visible {F1o} side, front side, of the sticker is an information-containing pattern in terms of a two- dimensional code such as an asymmetric two-dimensional code. The asymmetric two-dimensional code contains information such as identification of the target, orientation of the target and rotation relative to the image capturing device. The code can be printed, cut, etched, or otherwise applied to the sticker.

[0009] The target can be a plate or a sign which is g|ued or attached with screws or nails to the object to be measured. The asymmetric two-dimensional code is printed, cut, etched, or otherwise applied to the plate or sign.

[0010] When in use, the image capturing device can be configured to detect and record the target image and the two-dimensional code attached to it. A converting and calculating unit within the image capturing device comprises software that can read the pattern on the target and algorithms to calculate the position of the target at configurable time intervals. The intervals depending on outer circumstances, such as weather conditions. The position of the target derived from the converter, converted into numeric values, and calculated by the calculator of the image capturing device with algorithms that can be used to accurately detect movement or deflection of the measured object. The image capturing device will remain fixed, and as the structure with the target attached moves or deflects due to environmental or physical load, the image capturing device captures images of the target and converts the images to numeric values. The image capturing device will detect the target position referenced against time. The difference in values related to the position of the target will be compared over time to a reference target position value. The differences in the values of the target in three dimensions in relation to the image capturing device will be directly proportional to the movement of the object to be measured. Using the position of the fixed point of the image capturing device, absolute movement or deflection of a structural member can be determined.

[0011] The software of the image-to-numeric converter detects each target in the captured image. The two-dimensional asymmetric code of the target may be square in shape and has well defined corners and known size. Measuring values {F1o} of each corner, the mutual distance between the corners, and the asymmetric pattern is retrieved and calculated to define the exact position and orientation of the target. The orientation is established by defining an absolute vertical line in space, and the deviation between the different corner values in relation to the vertical line defines the deviation in angles in relation to the image capturing device. These angles and deviations are converted into numerical values calculated by the calculator to define the displacement.

[0012] The information, such as displacement, calculated values and identification can be recorded and stored or sent through a wireless or directly wired communications interface to a computing device, local or remote, for further analysis and/or trigging an alarm. The displacement measuring device can be used in connection with other sensors such as strain gauges, temperature, wind indicators and other sensors, or a building surveillance system. The data from all the sensors can be factored into the calculation and analysis of displacement. Multiple targets can also be used together to give a more detailed measurement of how the entire structure is behaving during operation.

[0013] ln a first aspect of the present invention, a method for measuring displacement of an object to be measured comprises steps of locating an image capturing device at a distance from an object to be measured, locating a target having an information-containing pattern at a position of an object to be measured of the measuring object such that the pattern is in a displacement measuring direction relative the image capturing device, capturing a reference image of the pattern with the image capturing device and converting the reference image to numeric reference values describing the exact position in three dimensions, capturing a measuring image of the pattern with the image capturing device and converting the measuring image to a numeric measurement value describing displaced position, calculating the deviation between the different numeric values, and determine the displacement of the target position and thereby displacement of the measured object.

{F1o}

[0014] The image capturing device may be attached to a location on the structure, such as a building, or may be attached at a location remote and isolated from the structure, such as the foundation of the building being measured. By isolated, it is meant that the remote location will be free from most external influences which directly affect the structure being monitored. ln most cases, the location of the image capturing device is more resistant to movement than the structural component, such as a roof truss, which is being measured. For example, when the structure is a building, the image capturing device may be attached to one of the walls of the building which is subjected to less displacement than for example a roof truss.

[0015] ln some cases, the image capturing device can include components which compensates for both intended and unintended motion of the device. lntended motion means that the image capturing device may be arranged to a moveable or rotatable stand. Unintended motion means subsidence or other movement of the ground, causing movement of the structure to which the image capturing device is attached to. For example, an accelerometer, preferably a three-axis accelerometer or an inclinometer can be mounted on or coupled to the image capturing device, its housing or to its mount, to detect any motion of the image capturing device, both when capturing images and between images. By detecting the direction and magnitude of such motion, the displacement calculation of the target can be corrected to remove any deficiencies that results from movement of the image capturing device. The motion detection component coupled to the image capturing device will produce a digital or other signal which can be processed by the image capturing device or transmitted to the computer processor that is calculating displacement data for the target.

[0016] The target surface is usually planar but could be curved, concave, convex, or have other geometries. The target surface can have a printed two- dimensional asymmetric code, containing information describing the orientation, location, and identification.

{F1o}

[0017] ln specific embodiments of the method herein, a plurality of targets with different information-containing pattern are located within a measuring area. The image capturing device can capture images from each of the targets, individually or in series, thereby measuring displacement of more than one structural component, such as several roof trusses.

[0018] ln another specific embodiment, two or more image capturing devices can be located in different positions within the measuring area, to cover the whole measuring area. ln the case where the measuring area is a building, all roof trusses may not be visible from only one spot, and by utilizing several image capturing devices together with several targets, all roof trusses can be measured. Multiple image capturing devices may share the same set of targets to improve the accuracy and minimize measurement errors.

[0019] When the image capturing device is mounted in the measuring area, and the targets are located on the structural components to be measured, an image is captured of each of the targets and converted into numeric values as reference values defining the origin position of the targets. These origin positions are stored in a memory of the image capturing device as comparison positions, for comparing later captured images to detect displacement of the targets.

[0020] ln a second aspect of the present invention, a device for measuring displacement comprises at least one target arranged with an information- containing pattern. The target is attached to an object to be measured, such as a roof truss. An image capturing device is arranged on a distance from the target on a location in a measuring area, such as a wall of a building. The image capturing device may be provided with a light source emitting a light for illuminating the target when capturing the image.

[0021] ln one embodiment, the light source is emitting a light that is outside the human visible spectrum, such as infrared light or ultra-violet light.

[0022] ln another specific embodiment of the device, the image capturing device may have an image-to-numeric converter. The image-to-numeric converter {F1o} may have the pattern information stored in a memory as well as origin position of the targets. The captured image is converted into numeric information regarding the position of the target. The image-to-numeric converter may further have a comparator to compare the reference image numeric information with the measured image numeric information. lf a displacement has occurred, the numeric information will deviate from the previous captured values.

[0023] ln one embodiment, the image capturing device may have a wide-angle lens. The wide-angle lens is arranged to capture images of targets that are not aligned with the image capturing device.

Brief description of drawinqs

[0024] The invention is now described, by way of examples, with reference to the accompanying drawings, in which: Fig. 1 shows an object measuring device installed in a building, Fig. 2 shows a view of a building with several targets, Fig. 3 shows a view of an image capturing device, Fig. 4 shows another view of an image capturing device, Fig. 5 shows an overview of the inside of an image capturing device, and Fig. 6 shows an example of a pattern arranged on a target.

Description of embodiments

[0025] All building structures are subjected to various loads depending on season, climate, and precipitation. ln the winter, snow falling on the roof of a building may quickly build up a heavy load, affecting one or several of the roof trusses of the roof. Other heavy loads can occur, for example if equipment is lifted on the roof for retrofitting fan systems or air conditioning systems, equipment for maintenance, subsidence or other movement of the ground, or other loads. This {F1o} may result in a displacement of the roof truss, such as bending or warping of one or several components of the roof truss. The method and device of the present invention provide a measurement of the displacement that is both accurate and cost efficient.

[0026] ln the following, a detailed description of a method according to the present invention is described. Fig.1 depicts the main components of an exemplified device mounted inside a building 1, seen in section, with an object to be measured A.1 - A.n, such as a roof truss 2 carrying a roof 3. An image capturing device 4 is attached to a stable part of the building, such as a wall 5 or a rotatable/movable stand or mount 5A. The image capturing device 4 may be attached either temporarily for single or short-term use or permanently for long- term continuous or periodic measurements of the roof trusses 2. The image capturing device 4 is attached directly to the wall 5 or attached to a console 6 which in turn is attached to the wall 5. The image capturing device 4 may be attached to other structures suitable for the purpose, such as the foundation 7 of the building 1 or another structure separate from the building but within the measuring area 8. Depending on the building construction, several image capturing devices 4 can be attached to different locations in the building 1, directed in different directions.

[0027] A first target 9 is attached to a roof truss 2 which can deflect and move in response to heavy loads, and other conditions. The first target 9 contains a pattern 10, a two-dimensional code, with information such as identification of the target. Preferably the two-dimensional code is asymmetric and contains both identification information and orientation information of the target 9. The target can be a patch, a sticker, or sticky note with an adhesive backside to be attached to the surface of the object to be measured. The visible side, front side, of the sticker is an information-containing pattern 10 in terms of a two-dimensional code such as an asymmetric two-dimensional code. The asymmetric two-dimensional code contains information such as identification of the target 9, orientation of the target 9 and rotation of target 9 relative to the image capturing device 4. The pattern 10 can be printed, cut, etched, or otherwise applied to the target 9. ln another {F1o} embodiment the target can be a plate 26 or a sign which is glued or attached with screws 27 or nails to the object to be measured A. The asymmetric two- dimensional pattern 10 is printed, cut, etched, or othen/vise applied to the plate 26 or sign. Motion of the roof truss 2 relative to the building 1 will cause the target 9 to mOVe.

[0028] ln a preferred embodiment, shown in Fig 2, several targets 9.1 - 9.n are attached to the roof trusses 2. One truss 2 can be provided with several targets 9.1 - 9.n, for example if the truss 2 is large and constructed in such way that some components 2a of the truss 2 is more effected by the load on the roof 3 than other components of the truss. Several targets 9.1 - 9.n can be attached to several roof trusses 2 to be able to measure different movement on different truss components 2a.

[0029] An image capturing device can be seen in Fig 3. lt comprises a housing 11, a mount 12, openings 13, 13a, 13b through which light is transmitted, and a filter 14 for filtering incoming unwanted light. Fig. 4 shows a different view of the housing 11. Several connecting sockets 16.a - 16.d may be arranged on one of the sides of the housing 11. The connecting sockets may be a socket for power 16.a for powering the device with electric energy, a connection to a local computer 16.b, a software update connector 16.c and a connector for connecting the device to the lnternet 16.d.

[0030] lnside the housing, as can be seen in Fig 5, is arranged a circuit board 17 providing an image capturing unit 4A, image-to-numeric converter 18, a calculator 19, a comparator 20, a transmitter 20a, and an illuminating source 21 emitting light outside the human visible spectrum, e.g. infrared light or ultra-violet light. A back-up battery 15 may be configured to power the image capturing device 4 during power failure and other connection failures. The image-to-numeric converter 18 includes software programmed to convert the information from the captured image into a set of numeric values. The numeric values define the absolute location of the target 9 at the moment the image was captured. The numeric values are then compared by the calculator 19 and the comparator 20 {F1o} with a reference value, which reference value is stored in a memory of the Calculator and acquired from a reference picture during installation of the device in the building 1. From the comparator 20 a value of the displacement is established. This displacement is also established even if the target shows no displacement, so called zero-displacement. This zero-displacement is a confirmation that the roof truss 2 can withstand the load affecting the roof 3, and the roof truss 2 is unaffected.

[0031] The software of the image-to-numeric converter 18 detects each target 9.1 - 9.n in the captured image. The information-containing pattern 10 of the target 9.1 - 9.n may be square in shape and has well defined corners 10a and known size. Measuring values of each corner 10a - 10d, the mutual distance between the corners 10a - 10d, and the asymmetric pattern 10 are retrieved and calculated to define the exact position and orientation of each target 9. The orientation is established by defining an absolute vertical line in space, and the deviation between the different corner values in relation to the vertical line defines the deviation in angles in relation to the image capturing device 4. These angles and deviations are converted into numerical values calculated by the calculator 19 to define the displacement.

[0032] A method is schematically presented in Fig.4. The image capturing device 4 is positioned to a wall 5 of the building 1, with view over the measuring area 8. lf it is impossible to get a view over the complete measuring area with only one image capturing device, two or more image capturing devices can be positioned on different locations in the building.

[0033] A target 9 is positioned on the object to be measured A, in this case a roof truss 2. lf the truss construction or the building design demands, several targets 9.1 - 9.n are positioned on different positions throughout the measuring area 8. Then the image capturing device 4 capture a first reference image of the target and a point of origin numeric value is established. This point of origin numeric value is preferably established during unaffected load conditions, for example during summer.

{F1o} 11

[0034] After installation of the image capturing device 4 or devices and the target 9 or targets, a connection between the image capturing device and a computer or automation network, either by wire 23 or wireless, is established. The transmitter 20a of the image capturing device 4 is connected to a computing unit 24, such as a PC, PLC, or other computer, which may provide the Internet connection 25. The computing unit 24 is arranged with a computing program for creating a visual presentation of the displacement over time and storing the different values.

[0035] lt is to be understood that while the invention has been described in conjunction with the detailed description thereof, the foregoing description is intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims. Other aspects, advantages, and modifications are within the scope of the following claims.

[0036] Unless expressly described to the contrary, each of the preferred features described herein can be used in combination with any and all of the other herein described preferred features.

Claims

1. A displacement measuring method, comprising following steps: a) Iocating an image capturing device (4) at a distance from an object to be measured (A.1 -A.n), b) Iocating a target (9), having a two-dimensional, information-containing pattern (10) at a position of the object to be measured (A.1 - A.n) such that the pattern (10) is in a displacement measuring direction relative the image capturing device (4), c) capturing a reference image of the pattern (10) with the image capturing device (4) and converting the reference image to a numeric reference value, d) capturing a measuring image of the pattern (10) with the image capturing device (4) and converting the measuring image to a numeric measuring value, e) calculating the deviation between the different numeric values, and f) determining the displacement of the measured object (A.1 - A.n).

2. The displacement measuring method according to claim 1, wherein a plurality of targets (9.1 - 9.n) with different information-containing patterns (10) are located on objects to be measured (A.1 - A.n) within a measuring area (8), the image capturing device (4) capturing measuring images of the targets (9.1 - 9.n) in a series, converting the measuring images to numeric values, calculating the deviation between the values in the series, and determining the displacement of each of the measured objects (A.1 - A.n) within the measuring area (8). {F1o}3. The displacement measuring method according to any of previous claims, wherein the measuring images are captured at given time intervals with a configurable frequency.

4. The displacement measuring method according to any of previous claims, wherein the captured images are converted to numeric values by the image capturing device (4), and the numeric values are transferred to a computing unit (24) with a visualization computer program for creating a visual presentation of the displacement over time.

5. The displacement measuring method according to claim 4, wherein a displacement alarm is triggered by a trigger point defined in the computer program.

6. A displacement measuring device comprising a target (9) arranged with an information-containing pattern (10), the target (9) attached to an object to be measured (A), an image capturing device (4) arranged on a distance from the target (9) on location in a measuring area (8), the image capturing device (4) provided with an image capturing unit (4A), a light source (21) emitting a light for illuminating the target (9) when capturing the image, an image-to-numeric converter (18) converting the captured image to numeric values, and a transmitting device (20a) for transmitting the numeric values to a computing unit (24). {F1o}7. A displacement measuring device according to claim 6, wherein the object to be measured (A) is a rooftruss (2) in a building (1) and the image capturing device (4) is attached to a wall (5) of said building (1).

8. A displacement measuring device according to claim 6 and 7, wherein the information-containing pattern (10) comprises a two-dimensional asymmetric code with identification and orientation information.

9. A displacement measuring device according to claim any of claims 6 to 8, wherein the information-containing pattern (10) is printed on a plate (26), or a sign, attached with screws (27) or nails, or on an adhesive sheet to be adhesively attached to the roof truss (2).

10. A displacement measuring device according to any of claims 6 to 9, wherein the light source (21) is emitting light outside the human visible spectrum, such as infra-red or ultra-violet light.

12. A displacement measuring device according to any of claims 6 to 10, wherein the image-to-numeric converter (18) comprises a calculator (19) with a memory in which the identification information of the pattern (10) is stored, further comprising a comparator (20) to compare the image-to-numeric converted values.

13. A displacement measuring device according to any of claims 7 to 12, wherein the image capturing device (4) comprises a wide-angle lens (28). {F1o}

14. A displacement measuring device according to any of claims 7 to 13, wherein the displacement measuring device (4) comprises a back-up battery (15).