CN104964652B - Battery winding production detection method and device based on machine vision - Google Patents

Abstract

The invention discloses a battery winding production detection method based on machine vision, which comprises the following steps: (1) the method comprises the following steps of arranging battery winding production equipment, arranging a machine vision system, a rotary table, a detection device and an absolute coordinate system step device on the battery winding production equipment, wherein the detection device comprises a first detection assembly, and the first detection assembly comprises a first pressing block, first diaphragm paper and a first camera; (2) presetting a standard average distance value and a standard distance difference value between the first diaphragm paper and the first pressing block; (3) carrying out initial absolute coordinate origin calibration on the first camera; (4) judging whether the calibration of the absolute coordinate origin needs to be carried out again; (5) starting up and calibrating the first camera; (6) detecting the distance between the first pressing block and the first diaphragm paper; (7) and (5) repeating the steps (4), (5) and (6) to finish the continuity detection of the winding distance and the distance difference between the first pressing block and the first diaphragm paper at different time points. A battery winding apparatus is also disclosed.

Description

A battery winding production detection method and equipment based on machine vision

technical field

The invention relates to battery winding equipment, in particular to a machine vision-based battery winding production inspection method and equipment.

Background technique

In recent years, the application of machine vision has become more and more extensive, and it has been widely used in various aspects of quality inspection. At present, machine vision systems have been applied to turntable battery winding equipment. A battery winding equipment needs three cameras to observe three stations. The functions of these three stations are: (1) to detect whether the distance between the diaphragm paper and the pressing block is qualified; (2) to detect the negative electrode sheet and the diaphragm paper (3) Check whether the distance between the positive plate and the separator paper is qualified. The machine vision system can be used to assist in judging whether the relative position of the film is within the specification. This detection method mainly uses the video observed by the camera as the absolute coordinates to adjust the position of the pressing block, thereby determining the relative position to the diaphragm paper, and then using the relative position of the diaphragm paper to adjust the relative position of the negative electrode and the positive electrode.

And the above-mentioned detection method has the following disadvantages in practical application: (1) the detection method is complicated, and the measurement of the distance is inaccurate, resulting in inaccurate adjustment of the relative position of the film; (2) due to vibration or human factors The impact caused the position of the camera to shift relative to the entire equipment, making the coordinates that should be "absolute" not absolute; (3) The pressing block is often changed due to maintenance, which brings many difficulties to machine adjustment and daily production; (4) Continuous monitoring is not possible, and regular inspection (usually one week) to control the movement of the camera causes a greater risk in production; (5) The operability of using the vision system to correct the position of the briquetting block is low, and the adjustment cycle is long, which affects production.

Contents of the invention

In view of the above deficiencies, the purpose of the present invention is to provide a battery winding production detection method and equipment based on machine vision, which has high detection accuracy, reduces the risk of misjudgment, and does not require continuous monitoring. The position adjustment is easy and the production efficiency is improved.

The technical scheme that the present invention adopts for achieving the above object is:

A machine vision-based battery winding production detection method, characterized in that it comprises the following steps:

(1) Set up a battery winding production equipment, on which a machine vision system, a turntable, and a detection device and an absolute coordinate system step device respectively arranged on the edge of the turntable are arranged on the battery winding production equipment, and the detection device includes a first A detection component, the first detection component includes a first pressing block, a first diaphragm paper arranged on the first pressing block and a first camera arranged above the side of the first diaphragm paper, and a vision system is integrated in the machine vision system System software, and it is respectively connected with the first camera and the absolute coordinate system step device;

(2) preset a standard average distance value A and a standard distance difference B between the first separator paper and the first briquetting block through the machine vision system;

(3) Carry out initial absolute coordinate origin calibration to the first camera:

(3.1) Turn on the battery winding equipment, rotate the step device of the absolute coordinate system to directly below the first camera through the turntable, and the first camera collects image information, and generates the initial absolute coordinate origin (p, q), and the calibration value of the initial absolute coordinate origin is generated in the csv file of the vision system software;

(3.2) For the abscissa x and y coordinate y of the generated initial absolute coordinate origin (p, q), a preset allowable value range is: p-m≤x≤p+m, and q-n≤y≤q+n;

(4) Before using the first camera, judge whether it is necessary to re-calibrate the origin of the absolute coordinates of the first camera, if necessary, repeat step (3); if not, proceed to step (5);

(5) Perform power-on calibration on the first camera: judge whether it is necessary to perform power-on calibration on the first camera, if not, proceed to step (6); otherwise, re-rotate the absolute coordinate system step device through the turntable Directly below the first camera, the first camera collects image information, the machine vision system generates the coordinate value of the coordinate origin, and compares this coordinate value with the allowable value range of the horizontal and vertical coordinates of the absolute coordinate origin, if Within the value range, then proceed to step (6), otherwise, the machine vision system prompts an alarm message, then finds the reason, and recalibrates the position of the first camera;

(6) Distance detection between the first briquetting block and the first diaphragm paper:

(6.1) The first camera collects the image information of the first briquetting block and the first diaphragm paper, and the distances between the upper edge and the lower edge of the first diaphragm paper can be obtained by the machine vision system as a, b respectively, and the first diaphragm paper The distances between the upper and lower edges of a compact are c and d respectively;

(6.2) The machine vision system calculates the distance A ₁ between the first briquetting block and the first diaphragm paper, and the calculation formula of A ₁ is: The distance difference B ₁ between the first compact and the first diaphragm paper, the calculation formula of B ₁ is: B ₁ =(db)-(ca);

(6.3) The machine vision system calculates the calculated distance A ₁ between the first briquetting block and the first diaphragm paper, and the distance difference B ₁ between the first briquetting block and the first diaphragm paper, respectively with the preset Compare the standard average distance value A and the standard distance difference B, and continuously judge whether the winding distance and the distance difference between the first diaphragm paper and the first briquetting block are qualified;

(7) Steps (4), (5), and (6) are repeated to complete the continuous detection of the winding distance and distance difference between the first compact and the first separator paper at different time points.

As a further improvement of the present invention, in the step (1), the detection device further includes a second detection component and a third detection component, wherein the second detection component includes a second camera, a second pressure block, And the second diaphragm paper and the negative electrode sheet arranged on the second pressing block in sequence, the third detection component includes the third camera, the third pressing block, and the third diaphragm paper and the positive electrode successively arranged on the third pressing block piece.

As a further improvement of the present invention, when repeating the steps (4) and (5), it also includes the step of performing power-on calibration on the second camera and the third camera respectively.

As a further improvement of the present invention, it also includes step (8): the machine vision system adjusts the distance between the negative electrode sheet and the second separator paper, the positive electrode sheet and the first separator paper according to the relative position between the first pressing block and the first separator paper The relative position between the third diaphragm paper.

As a further improvement of the present invention, in the step (1), the absolute coordinate system step device is fixed on the edge of the turntable to provide a fixed absolute coordinate system for the turntable.

As a further improvement of the present invention, in the step (6.3), the calculated B1 is a positive value indicating that the first compact is inclined counterclockwise relative to the first diaphragm paper, and a negative value of B1 indicates that the first compact is inclined relative to the first diaphragm paper. A separator paper is inclined clockwise.

The battery winding equipment based on machine vision for implementing the above detection method is characterized in that it includes a machine vision system, a turntable, a detection device and an absolute coordinate system step device respectively arranged on the edge of the turntable; wherein the detection device includes a first detection Components, the first detection component includes a first pressing block, a first diaphragm paper arranged on the first pressing block and a first camera arranged above the side of the first diaphragm paper; the vision system software is integrated in the machine vision system , and they are respectively connected with the first camera and the absolute coordinate system step device.

As a further improvement of the present invention, the detection device further includes a second detection component and a third detection component, wherein the second detection component includes a second camera, a second pressing block, and a second pressing block arranged in sequence The second diaphragm paper and the negative electrode sheet, the third detection assembly includes a third camera, a third pressing block, and a third diaphragm paper and the positive electrode sheet sequentially arranged on the third pressing block.

As a further improvement of the present invention, the absolute coordinate system step device is fixed on the edge of the turntable to provide a fixed absolute coordinate system for the turntable.

As a further improvement of the present invention, the overall appearance of the absolute coordinate system step device is in an "L" shape.

The beneficial effects of the present invention are as follows: the absolute coordinate origin calibration and power-on calibration of the camera are carried out by the step device of the absolute coordinate system, so that the video of the camera has an absolute coordinate system, and the risk of misjudgment caused by the movement of the camera to the detection process is reduced, thereby Improve the detection accuracy; start-up calibration is performed before each detection, without continuous monitoring, and regularly detect and control whether the camera moves; the detection method is simple, accurate, high-precision, and the position adjustment is convenient and accurate; through the "absolute coordinate system" calibration function of the vision The system software can uniformly adjust the position of the briquetting block, which is easy to adjust and improves production efficiency.

The foregoing is an overview of the technical solution of the invention, and the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Description of drawings

FIG. 1 is a schematic structural view of a battery winding device according to an embodiment of the present invention;

Fig. 2 is a flowchart of an embodiment of the present invention.

detailed description

In order to further illustrate the technical means and functions adopted by the present invention to achieve the intended purpose, the specific implementation modes of the present invention will be described in detail below in conjunction with the accompanying drawings and preferred embodiments.

Embodiment one

Please refer to Fig. 1 and Fig. 2, Embodiment 1 of the present invention discloses a battery winding production detection method based on machine vision, which includes the following steps:

(1) Set up a battery winding production equipment, on which a machine vision system, a turntable 1, and a detection device and an absolute coordinate system step device 2 respectively arranged on the edge of the turntable 1 are arranged on the battery winding production equipment, and the detection device Including the first detection component 3, the first detection component 3 includes a first pressure block 31, a first diaphragm paper 32 arranged on the first pressure block 31 and a first camera 33 arranged above the first diaphragm paper 32 side , the vision system software is integrated in the machine vision system, and it is connected with the first camera 33 and the absolute coordinate system step device 2 respectively;

(2) preset a standard average distance value A and a standard distance difference B between the first diaphragm paper 32 and the first pressing block 31 through the machine vision system;

(3) Carry out initial absolute coordinate origin calibration to described first camera 33:

(3.1) Turn on the battery winding equipment, and rotate the absolute coordinate system step device 2 directly below the first camera 33 through the turntable 1, and the first camera 33 collects image information, and generates initial absolute coordinates through the machine vision system The origin (p, q), and the calibration value of the initial absolute coordinate origin is generated in the csv file of the vision system software;

(3.2) For the abscissa x and y coordinate y of the generated initial absolute coordinate origin (p, q), a preset allowable value range is: p-m≤x≤p+m, and q-n≤y≤q+n;

(4) Before using the first camera 33, judge whether it is necessary to redo the calibration of the absolute coordinate origin of the first camera 33, if necessary, repeat step (3); if not, proceed to step (5) ;

(5) Carry out power-on calibration to the first camera 33: judge whether it is necessary to carry out the power-on calibration of the first camera 33, if not, proceed to step (6); otherwise, reset the absolute coordinate system step device 2 Rotate the turntable 1 to directly below the first camera 33, the first camera 33 collects image information, the machine vision system generates the coordinate value of the coordinate origin, and compares this coordinate value with the allowable acquisition of the horizontal and vertical coordinates of the absolute coordinate origin Value range is compared, if within the value range, then carry out step (6), otherwise, described machine vision system prompts alarm message, then finds reason, recalibrates the position of first camera 33;

(6) Distance detection between the first briquetting block 31 and the first diaphragm paper 32:

(6.1) The first camera 33 collects the image information of the first briquetting block 31 and the first diaphragm paper 32, and the distances between the upper edge and the lower edge of the first diaphragm paper 32 can be obtained by the machine vision system as a, b respectively , the distances between the upper edge and the lower edge of the first pressing block 31 are c, d respectively;

(6.2) The machine vision system calculates the distance A ₁ between the first briquetting block 31 and the first diaphragm paper 32, and the calculation formula of A ₁ is: The distance difference B ₁ between the first pressure block 31 and the first diaphragm paper 32, the calculation formula of B ₁ is: B ₁ =(db)-(ca);

(6.3) The machine vision system will calculate the distance A ₁ between the first pressing block 31 and the first diaphragm paper 32, and the distance difference B ₁ between the first pressing block 31 and the first diaphragm paper 32, Comparing with the preset standard average distance value A and the standard distance difference value B respectively, and continuously judging whether the winding distance and the distance difference between the first separator paper 32 and the first pressing block 31 are qualified;

(7) Repeat steps (4), (5), and (6) to complete the continuity detection of the winding distance and distance difference between the first compact 31 and the first diaphragm paper 32 at different time points .

In the step (1), the absolute coordinate system step device is fixed on the edge of the turntable to provide a fixed absolute coordinate system for the turntable.

In the step (6.3), the calculated B1 is a positive value indicating that the first compact is inclined counterclockwise relative to the first diaphragm paper, and a negative value of B1 represents that the first compact is clockwise relative to the first diaphragm paper tilt.

Meanwhile, in this embodiment, the first camera is suspended above the edge of the turntable through other components in the device.

This embodiment also discloses a machine vision-based battery winding device for implementing the above method, which includes a machine vision system, a turntable 1, a detection device and an absolute coordinate system step device 2 respectively arranged on the edge of the turntable 1, wherein the detection The device includes a first detection assembly 3, which includes a first pressing block 31, a first diaphragm paper 32 arranged on the first pressing block 31, and a first camera 33 arranged above the side of the first diaphragm paper 32 , the vision system software is integrated in the machine vision system, and it is respectively connected with the first camera 33 and the absolute coordinate system step device 2 . The absolute coordinate system step device 2 is fixed on the edge of the turntable 1 to provide a fixed absolute coordinate system for the turntable 1 . The overall appearance of the absolute coordinate system step device 2 is "L".

This embodiment introduces the absolute coordinate system step device 2, so that an "absolute coordinate system" is embedded in the battery winding equipment. Before using the first camera 33 for the first time, an initial absolute coordinate origin calibration is performed. In the subsequent actual use process, it is artificially judged whether it is necessary to re-calibrate the absolute coordinate origin. If re-calibration is not required, the initial absolute coordinate origin is used for power-on calibration in the subsequent power-on calibration; The re-calibrated coordinate origin is used for subsequent power-on calibration.

In actual use, if the first camera 33 is shifted, power-on calibration is required to determine whether the regenerated coordinate origin is within the value range of the absolute coordinate origin horizontal and vertical coordinates, if not within this range, the described The machine vision system prompts the alarm information, then finds the cause, and recalibrates the position of the first camera 33 until the regenerated coordinate origin is within the value range of the absolute coordinate origin horizontal and vertical coordinates; otherwise, directly carry out the first briquetting block 31 and the first Distance detection between diaphragm paper 32.

It has been verified that in the process of use, after the power-on calibration is performed through the absolute coordinate system step device 2, the accuracy of the position of the first camera 33 relative to the entire equipment turntable meets the definition of "absolute" in the equipment process, and the horizontal axis of the regenerated coordinate origin The vertical coordinates are all within the value range of the horizontal and vertical coordinates of the absolute coordinate origin. Therefore, when the distance between the first pressing block 31 and the first separator paper 32 is detected by the first camera 33 , the detected distance is more accurate and the precision is higher.

Embodiment two

The main difference between the second embodiment and the first embodiment is that in the step (1), the detection device further includes a second detection component 4 and a third detection component 5, wherein the second detection component 4 includes the first Two cameras 41, a second pressing block 42, and the second diaphragm paper 43 and the negative electrode sheet 44 arranged on the second pressing block 42 in sequence, the third detection assembly 5 includes a third camera 51, a third pressing block 52, And the third diaphragm paper 53 and the positive electrode sheet 54 that are arranged on the third pressing block 52 in turn; repeat the steps (4), (5), and also include the steps of power-on calibration of the second camera 41 and the third camera 51 respectively Step; Simultaneously, also comprise step (8), described machine vision system adjusts between the negative electrode sheet 44 and the second diaphragm paper 43, positive electrode sheet 54 according to the relative position between the first briquetting block 31 and the first diaphragm paper 32 The relative position between the third septum paper 53.

At the same time, the detection device in the battery winding equipment based on machine vision also includes a second detection component 4 and a third detection component 5, wherein the second detection component 4 includes a second camera 41, a second pressing block 42 , and the second separator paper 43 and the negative electrode sheet 44 that are sequentially arranged on the second pressing block 42, the third detection component 5 includes a third camera 51, a third pressing block 52, and are sequentially arranged on the third pressing block 52 The third separator paper 53 and the positive electrode sheet 54 on it. Other steps and components are the same as those in Embodiment 1, and will not be repeated here.

In actual production, a battery winding equipment needs three cameras to detect three stations, which are: (1) the distance between the diaphragm paper and the pressing block, (2) the distance between the negative electrode sheet and the diaphragm paper, and (3) The distance between the positive plate and the separator paper. The detection method provided in Embodiment 1 is to detect the distance between the separator paper and the briquetting block. In this embodiment, the relative position between the first briquetting block and the first separator paper obtained in Embodiment 1 is used to adjust the negative electrode sheet and the first separator paper. The relative position between the two diaphragm papers, between the positive electrode sheet and the third diaphragm paper, the method and embodiment 1 detection of the distance between the negative electrode sheet and the second diaphragm paper, the positive electrode sheet and the third diaphragm paper The method for the distance between the pressing block and the first diaphragm paper is the same. Through the above method, the absolute coordinate origin calibration and power-on calibration of the first camera, the second camera, and the third camera can be performed respectively, so as to ensure that the positions of the first camera, the second camera, and the third camera meet the requirements for using them for detection.

The vision system software is integrated in the machine vision system of the present invention. The software has an automatic memory function and can save the calibration results of the last startup. The calibration results continue to run, and the purpose of power-on calibration according to actual needs is truly achieved. At the same time, the value of each absolute coordinate origin calibration is generated in the csv file of the software, so each calibration value can be found in the csv file. The machine vision system is connected with the absolute coordinate system step device. The vision system software in the machine vision system has the "absolute coordinate system" calibration function. The "basic parameters" in the menu are very convenient for engineers to adjust the machine. The relative position of "/down" can uniformly adjust the position and inclination of several pressing blocks, which is easy to adjust, easy to operate, and improves production efficiency.

The focus of the present invention is mainly to perform absolute coordinate origin calibration and power-on calibration on the camera through the absolute coordinate system step device, so that the video of the camera has an absolute coordinate system, reducing the risk of misjudgment caused by the movement of the camera to the detection process, thereby Improve the detection accuracy; start-up calibration is performed before each detection, without continuous monitoring, and regularly detect and control whether the camera moves; the detection method is simple, accurate, high-precision, and the position adjustment is convenient and accurate; through the "absolute coordinate system" calibration function of the vision The system software can uniformly adjust the position of the briquetting block, which is easy to adjust and improves production efficiency.

The above is only a preferred embodiment of the present invention, and does not limit the technical scope of the present invention. Therefore, other battery rolls based on machine vision are obtained by adopting the same or similar technical features as the above-mentioned embodiments of the present invention. The production detection method and equipment are all within the protection scope of the present invention.

Claims (10)

1. a kind of battery winding production detection method based on machine vision, it is characterised in that comprise the following steps：

(1) set a battery winding production equipment, in the battery winding production equipment set NI Vision Builder for Automated Inspection, rotating disk, And the detection means and absolute coordinate system stairs device of disk edge are respectively arranged at, the detection means includes the first detection group Part, first detection components include the first briquetting, the first diaphragm paper being arranged on the first briquetting and are arranged at the first barrier film The first camera above paper side, is integrated with vision system software in the NI Vision Builder for Automated Inspection, and its respectively with the first shooting Head and the connection of absolute coordinate system stairs device；

(2) by the NI Vision Builder for Automated Inspection to a default standard average distance value A between the first diaphragm paper and the first briquetting, and One gauged distance difference B；

(3) initial absolute coordinate origin calibration is carried out to first camera：

(3.1) open battery winding equipment, by the absolute coordinate system stairs device by turntable rotation to the first camera just Lower section, the first camera collection image information, by the NI Vision Builder for Automated Inspection generate initial absolute coordinate origin (p, Q), and the initial absolute coordinate origin demarcation numerical generation in the csv documents of vision system software；

(3.2) span allowed the abscissa x and ordinate y default one of the initial absolute coordinate origin (p, q) of generation For：P-m≤x≤p+m, and q-n≤y≤q+n；

(4) before using first camera, judge whether to need to re-start the first camera absolute coordinate original The demarcation of point, if desired, then repeat step (3)；If need not, carry out step (5)；

(5) calibration is booted up to first camera：Judge whether to need to carry out the first camera start calibration, if Need not, then carry out step (6)；Otherwise, the absolute coordinate system stairs device is passed through into turntable rotation to the first shooting again Immediately below head, the first camera collection image information, the coordinate value of the NI Vision Builder for Automated Inspection generation origin of coordinates, and will This coordinate value, if in span, is carried out compared with the span that the transverse and longitudinal coordinate of absolute coordinate origin allows Step (6), otherwise, the NI Vision Builder for Automated Inspection prompt warning message, then search reason, recalibrate the position of the first camera Put；

(6) the distance between described first briquetting and the first diaphragm paper detect：

(6.1) first camera gathers the image information of the first briquetting and the first diaphragm paper, passes through the machine vision system The distance that system can obtain the first diaphragm paper top edge and lower edge is respectively a, b, the first briquetting top edge and lower edge Distance respectively c, d；

(6.2) NI Vision Builder for Automated Inspection calculates the distance between the first briquetting and the first diaphragm paper A₁, A₁Calculation formula be：The poor B of the distance between first briquetting and the first diaphragm paper₁, B₁Calculation formula be：B₁=(d-b)- (c-a)；

(6.3) NI Vision Builder for Automated Inspection is by the distance between the first briquetting calculated and the first diaphragm paper A₁, and the first briquetting The distance between first diaphragm paper poor B₁, compared respectively with default standard average distance value A and gauged distance difference B Compared with, continuously judge between first diaphragm paper and the first briquetting winding distance and distance difference it is whether qualified；

(7) repeat step (4), (5), (6), complete in different time points to the volume between first briquetting and the first diaphragm paper Enter Line Continuity detection around distance and distance difference.

2. the battery winding production detection method based on machine vision as claimed in claim 1, it is characterised in that in the step Suddenly in (1), the detection means also includes the second detection components and the 3rd detection components, wherein, the second detection components bag Include second camera, the second briquetting and the second diaphragm paper and negative plate being set in turn on the second briquetting, the 3rd detection Component includes the 3rd camera, the 3rd briquetting and the 3rd diaphragm paper and positive plate being set in turn on the 3rd briquetting.

3. the battery winding production detection method based on machine vision as claimed in claim 2, it is characterised in that described in repeating When step (4), (5), in addition to the step of boot up calibration to second camera and the 3rd camera respectively.

4. the battery winding production detection method based on machine vision as claimed in claim 3, it is characterised in that it also includes Step (8)：The NI Vision Builder for Automated Inspection adjusts negative plate and the according to the relative position between the first briquetting and the first diaphragm paper Relative position between two diaphragm papers, between positive plate and the 3rd diaphragm paper.

5. the battery winding production detection method based on machine vision as claimed in claim 1, it is characterised in that in the step Suddenly in (1), the absolute coordinate system stairs device is fixed on disk edge, and a fixed absolute coordinate is provided for the rotating disk System.

6. the battery winding production detection method based on machine vision as claimed in claim 1, it is characterised in that the step (6.3) in, for the B1 calculated to be to tilt counterclockwise on the occasion of representing the first briquetting relative to the first diaphragm paper, B1 is that negative value represents First briquetting is inclination clockwise relative to the first diaphragm paper.

7. implement the battery winding equipment based on machine vision of one of the claim 1-6 detection method, it is characterised in that It includes NI Vision Builder for Automated Inspection, rotating disk, the detection means for being respectively arranged at disk edge and absolute coordinate system stairs device；Wherein The detection means includes the first detection components, and first detection components include the first briquetting, be arranged on the first briquetting the One diaphragm paper and the first camera being arranged above the first diaphragm paper side；Vision system is integrated with the NI Vision Builder for Automated Inspection Software, and it is connected with the first camera and absolute coordinate system stairs device respectively.

8. the battery winding equipment based on machine vision as claimed in claim 7, it is characterised in that the detection means is also wrapped Include the second detection components and the 3rd detection components, wherein, second detection components include second camera, the second briquetting and The second diaphragm paper and the negative plate being set in turn on the second briquetting, the 3rd detection components include the 3rd camera, the 3rd Briquetting and the 3rd diaphragm paper and positive plate being set in turn on the 3rd briquetting.

9. the battery winding equipment based on machine vision as claimed in claim 7, it is characterised in that the absolute coordinate system platform Rank device is fixed on disk edge, and a fixed absolute coordinate system is provided for the rotating disk.

10. the battery winding equipment based on machine vision as claimed in claim 7, it is characterised in that the absolute coordinate system Stairs device bulk shape is L-shaped.