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WO2018197752A1 - Agencement de mesure de mouvement - Google Patents

Agencement de mesure de mouvement Download PDF

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Publication number
WO2018197752A1
WO2018197752A1 PCT/FI2018/050300 FI2018050300W WO2018197752A1 WO 2018197752 A1 WO2018197752 A1 WO 2018197752A1 FI 2018050300 W FI2018050300 W FI 2018050300W WO 2018197752 A1 WO2018197752 A1 WO 2018197752A1
Authority
WO
WIPO (PCT)
Prior art keywords
movable element
markings
sensor
microcontroller
marking
Prior art date
Application number
PCT/FI2018/050300
Other languages
English (en)
Inventor
Edward STENMAN
Original Assignee
Mikronix Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mikronix Oy filed Critical Mikronix Oy
Publication of WO2018197752A1 publication Critical patent/WO2018197752A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/347—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells using displacement encoding scales
    • G01D5/34746—Linear encoders
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/347—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells using displacement encoding scales
    • G01D5/34776—Absolute encoders with analogue or digital scales
    • G01D5/34792—Absolute encoders with analogue or digital scales with only digital scales or both digital and incremental scales
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
    • G01P3/36—Devices characterised by the use of optical means, e.g. using infrared, visible, or ultraviolet light
    • G01P3/38—Devices characterised by the use of optical means, e.g. using infrared, visible, or ultraviolet light using photographic means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
    • G01P3/64—Devices characterised by the determination of the time taken to traverse a fixed distance
    • G01P3/68—Devices characterised by the determination of the time taken to traverse a fixed distance using optical means, i.e. using infrared, visible, or ultraviolet light
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66B—ELEVATORS; ESCALATORS OR MOVING WALKWAYS
    • B66B1/00—Control systems of elevators in general
    • B66B1/34—Details, e.g. call counting devices, data transmission from car to control system, devices giving information to the control system
    • B66B1/3492—Position or motion detectors or driving means for the detector
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/244—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains
    • G01D5/246—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains by varying the duration of individual pulses
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/36—Forming the light into pulses
    • G01D5/366—Particular pulse shapes

Definitions

  • the present invention relates to tracking and measuring movement in a piston- type arrangement present in many applications, such as in heavy machinery, trac- tors, and industrial machines, for instance.
  • Accelerometers are a type of the possible device which is able to determine the speed or rotational movement based on acceleration affecting the element.
  • One type of measuring the presence or non-presence of an element in a given spot and thus, also the movement of an element is to use several reflection-type transmission-reception elements.
  • the transmitted signal e.g. light
  • the transmitted signal reflects from an element by e.g. measuring the propagation time until the reflected signal is received, it is possible to determine whether the signal has reflected from a given surface or not (in case the surface of the element is movable in a non-parallel direction to the transmitted signal, for instance).
  • Optical arrangements may be used in general for tracking a location even for a more complex movement than just within a single direction. These arrangements can be called camera-based optical navigation sensors.
  • One example of tracking the location and movement within a two-dimension flat horizontal surface is implemented in a traditional optical mouse used in connection with a regular PC. It uses a light source, such as a light emitting diode (LED), and a light detector in a form of photodetectors. Also a laser diode, which emits infrared (IR) light, can be used.
  • the sensor system generally comprises a low resolution camera, the light source, some simple optics and a controller.
  • the principle of the optical mouse is to take 1000 or even more images (e.g.
  • the rod moves within a cylinder and a sensor is mounted to the side of the cylinder for reading the coding. It seems that the Parker's Intellinder may use four different widths in the coding bars where the coding bars are each marked directly on the whole outer circumference of the rod. The position of the rod is communicated continually to the controller. Many applications are discussed, such as forklifts, forestry vehicles, gantry cranes, trucks or tractors (lift or tilt cylinders) or in door systems. According to the information available from the Parker's Intellinder, it uses a camera (optical sensor "30") and a bar where the latter is applied in "Kilpinen” (US 5,539,993) as well.
  • Patent publication "Kilpinen” discloses an optical reading sensor for reading a location scale. Kilpinen applies bar coding, where there are two different bar widths. Other vertical edge of the subsequent bars seems to locate in places with fixed distance gaps. In an embodiment, the above fixed distance gap is three units of length, the width of the thicker bar is two units of length and the narrower bar has a width of one unit of length.
  • a disad- vantage of Kilpinen is that it requires heavy processing power for the image recognition performed by the camera. This results in an expensive solution. The same applies for the Parker's Intellinder as well where a same type of bar is used.
  • both Hartzell and Kilpinen require that the whole length of the rod has the markings.
  • the marking length is a fixed one.
  • the sensor needs to be a longer one as well in Kilpinen (many light receivers with different detection areas). This makes the size of the sensor hard to be fit in a regular cylinder used in industrial applications.
  • Patent publication "Norcross” discusses a chain code on a rod or cylinder type of a movable member which is applicable in hydraulic cylinders, gan- try cranes, drawbridges, canal locks, elevators, conveyer belt systems, systems with robotics, computer controlled painting devices and shock absorbers for cars.
  • the bar code can be manufactured on the member by laser photo absorption, or by etching on an aluminum surface.
  • the bar code may have four different types (bar code, line bar code, binary code, gapped binary code) and the detector de- tects a part of the code in one instant and possibly the whole code during the movement of the member. A signal is created based on the detected code.
  • German publication "Leuze”, DE 10014194 discloses a piston rod position determination arrangement where the rod surface has an alternating pattern comprising black lines. The markings are scanned with an optical transmitter beam as the piston moves, through the reflected light. The black parts are interpreted as “1 " and white parts as "0", and based on these values, a binary valued voltage signal U1 is obtained. U2 is obtained by delaying U1 by the propagation time spent along the width of the thinner line.
  • Reed switches do not work properly with the hydraulic cylinders because the piston would require a magnet and it would not work properly with an iron-made cylinder tube. Furthermore, reed switches output just an on/off-kind of data, suitable e.g. as a proximity switch for a burglar alarm; i.e. the position data information is obtained for a singular location only. This means that reed switches are not well suited for situations where continuous position data is required. Summary of the invention
  • the present invention discloses an arrangement for measuring a position of a movable element in relation to a stationary element or surface, wherein the arrangement comprises:
  • a sensor for sensing optically a section of a surface of a movable element; and - a microcontroller configured to control the arrangement, and to save obtained measurement results, and to send forward obtained information at least partially.
  • each marking comprises a bar code wherein each different bar code corresponds to a dedicated symbol
  • the microcontroller configured to determine the symbol from the optically sensed bar code
  • the microcontroller is configured to determine a position of the movable element in view of the sensor by taking the determined symbol and/or incremental move- ment data between the markings into account.
  • the width of the each marking is taken into account in the position determination.
  • a single bar code comprises thin bars, wide bars, thin spacings and/or wide spacings between the bars, as parts of the bar code.
  • a bar code represents a 3-bit symbol where two bars and a single spacing each correspond to a bit in a consequential fashion.
  • the wide part corresponds to bit “1 " and a thin part corresponds to bit "0".
  • a bar code represents a 5-bit symbol where three bars and two spacings each correspond to a bit in a consequential fashion.
  • the symbol in case all the sensed parts are of equal width, the symbol is determined to be all zeros.
  • the markings are manufactured on the movable element by etching or laser carving.
  • all markings are manufactured on the movable element with uniform spaces between subsequent markings.
  • the wider part is over two times wider than the thinner part.
  • the microcontroller it is configured to compare subsequent parts of the marking and if a width ratio of a first part and a second part is over 1 , and a width ratio of a halved first part with a second part is also over 1 , it is determined that the first part is "1 " and the second part is "0".
  • the microcontroller in the microcontroller, it is configured to com- pare subsequent parts of the marking and if a width ratio of a first part and a second part is over 1 , and a width ratio of a halved first part with a second part is less than 1 , it is determined that the first part and the second part have same bit values.
  • the senor is configured to optically take a first image of an area on the surface of the movable element, then to take a second image after a given period of time and after a possible movement of the movable element in relation to the sensor, then to compare locations of the components visible in both taken images, and the microcontroller is configured to obtain a movement speed for the movable element based on the obtained change of the location of the components.
  • the microcontroller is configured to calculate a reference location point at the start or end of each sensed marking, and to calculate a position of the movable element in relation to the previously calculated reference location point.
  • the arrangement is configured to automatically change the shutter speed after every sampled image has been taken, in order to compensate different lighting conditions, and shiny and black areas on the surface of the movable element.
  • the markings are configured to be manufactured in relatively thick intervals along the given range of the movable or stationary element.
  • the inventive idea also comprises a use of an arrangement for measuring a position of a movable element in relation to a stationary element or surface, corre- sponding to the above arrangement.
  • the use is characterized in that the arrangement is applied in hydraulic or pneumatic cylinders, industrial machines, vehicles, robotic arms, training devices, in medical or rehabilitation testing devices or in academic testing devices.
  • the inventive idea also comprises a corresponding method for measuring a posi- tion of a movable element in relation to a stationary element or surface, wherein the method comprises the steps of
  • the method is characterized in that - at least one optically visible marking has been manufactured on or in the movable element, where each marking comprises a bar code wherein each different bar code corresponds to a dedicated symbol; wherein the method further comprises the steps of - determining the symbol from the optically sensed bar code by the microcontroller; and
  • Figure 1 a illustrates the sensor mounted on a cylinder with etched markings, as a photograph showing an embodiment of the product
  • Figure 1 b illustrates a close-up of the etched markings shown in Figure 1 a
  • Figure 2 illustrates an example illustrating certain bar code markings and their di- mensions along a cylinder
  • Figure 3 illustrates a coding system example represented with two vertical bars (left column), and another coding system example represented with three vertical bars (two right-most columns),
  • Figure 4a illustrates an example of the possible dimensions applicable in the bar codes, in this example for the symbol representing "4",
  • Figure 4b illustrates an example of a mark, which is a two-bar marking representing "1 ", showing also some characteristics of the marking used in the determination logic of the symbol, and
  • Figure 5 illustrates a cylinder integrated sensor in an embodiment of the arrange- ment.
  • the present invention introduces a position tracking sensor for various different applications, uses and devices.
  • a position tracking sensor for various different applications, uses and devices.
  • such a sensor can be applied in hydraulic or pneumatic cylinders usable in strength training devices, gym devices or medical testing devices, or in academic testing environments.
  • the sensor can also be applied in industrial manufacturing environments, or in vehicles or working tools, such as in robotic arms, in tractors, or in pneumatic lifts, for instance.
  • the position tracking sensor is applicable in any environment where a physi- cal member is movable in a single direction in reference to another member or fixed structure.
  • the present invention applies markings which are visible on the movable element.
  • the markings can be manufactured with many various methods and examples of these are the laser engraved markings and markings made with etching.
  • One physical aspect of the markings is that the marking itself should not increase the gasket wear or make any audible sounds in the situation where the rod slides against the gasket.
  • An embodiment showing an etched cylinder is illustrated in Figure 1 a and a close-up of the marking is illustrated in Figure 1 b.
  • Laser marking is a highly useful way to perform the markings on the cylinder because the surface smoothness will not suffer after the laser marking has been added. Laser carving will make a deep color change in the metal surface, and therefore it will not wear off in regular use situations of the moving cylinder.
  • the laser carvings can be made with a fiber laser source having a wavelength of 1062 nm, power selection of 70 % of the available maximum, the input power of the laser source is 1 kW at its maximum and the marking speed obtained with this device is about 3000 mm/s. It is emphasized that this is merely a single example, and also many other parameter values of the laser source can be found useful in the context of the present application.
  • the position tracking sensor applies certain kinds of coding in the preferred em- bodiment of the present invention.
  • a specific barcode is applied in these multiple positions along the rod or cylinder in an embodiment of the invention.
  • FIG. 2 An example illustrating certain bar code markings along a cylinder is shown in Figure 2.
  • the markings 9 can be manufactured on the cylinder or rod 8 with uniform spaces between one another.
  • the distance between markings 9 is 50 mm but it is notable that all values in Figure 2 show just a single embodiment of the invention.
  • the example shows a total cylinder 8 length of 200 mm with four different bar code markings 9 along this length, and an option of having a shorter cylinder length of 160 mm with first three markings 9. Still, even a non-uniform space profile is possible between the applied markings 9.
  • Figure 2 applies a certain pattern of bar codes where the markings 9 represent numbers "0, 1 , 2, 3" in their running order, in this example.
  • Figure 3 illustrates an example of a possible bar code system which may apply either two bars or three bars.
  • a single bar code corresponds to a single marking 9.
  • eighteen markings 9 are shown in Figure 3 illustrating the logic behind the coding in this embodiment of the invention.
  • the two-bar system is shown in the column on the left, while the three-bar system is shown in the two rightmost columns of Figure 3.
  • the two-bar coding system can define seven different symbols which can be named as natural numbers in their running order, as [0, 1 , 2, 3, 4, 5, 6], for instance.
  • the bar widths are here constructed so that the maximum width of a single symbol (“6") is six units of length in this embodiment of the bar code system.
  • FIG 4a An example of the possible dimensions applicable in the bar codes is shown in Figure 4a.
  • This illustration shows a two-bar marking 9 and some selected widths and other dimensions in one embodiment of the coding used in the present invention. This corresponds to the symbol "4" in the two-bar coding example above in Figure 3.
  • the wider bar may have a width of 2,5 units of length and the narrower bar has a width of 1 (one) unit of length.
  • the spacing within a single marking 9, between the two bars is also 1 (one) unit of length.
  • the space from the left edge of the marking 9 to a previous marking (the right edge of the previous marking) is 2,5 units of length.
  • the above factor 2,5 can be replaced with some other value which is larger than 2,5.
  • the width of the bar can be measured by measuring the movement from when the shutter value has passed a predefined threshold until it returns to normal. If there are two or more bars within the same symbol, the gap width between the bars can be measured in the same way.
  • the ratio between wide and thin bars is fixed, and absolute width values can be selected based on the usual movement speeds present in the used application. This means that in case the cylinder moves in a rapid speed, the markings 9 have to be longer, i.e. wider, in order to detect them properly.
  • the sensor can be used with different resolutions and with different surfaces, in addition to different movement speeds of the moving element.
  • both bars and spacings are used to represent an odd-bit binary number for the different positions on the rod (or cylinder). Possible numbers of different codes in relation to the number of bars can be theoretically expressed with equation (1 ) and the maximal code length can be expressed with equation (2):
  • Ncoaes _ 1 ( 1 )
  • L max (N bar * 2 - 2) * Ew thick + Ew thin (2) where Ewthick equals the width of the wider bar and Ewthin equals the width of the thinner bar.
  • FIG. 4b shows an example of a marking 9, which is a two-bar marking representing "1 ", as in Figure 3 (second marking from the top).
  • the code is supposed to move from right to left under the sensor, and the controller of the sensing system is aware that each code has only two bars and the direction of movement.
  • the sensor encounters the start of the thin black bar ("e2" in Figure 4b)
  • the sensor measures how long distance it has to travel until the thin bar ends.
  • the length of the following spacing (“e1 ") will be measured.
  • the wide bar (“eO") is encountered after the spacing, its length is measured as well .
  • length in the movement direction we mean the horizontally directed width of the bar.
  • the start of the first bar is detected.
  • the sensor measures the length along the bar until the bar ends. Then the bar width is obtained and it can be right away stored in a memory. The following spacing is measured until a start for the second bar is detected. Then, the spacing width is obtained and it can be stored in the memory. Furthermore, along the movement across the second bar, when its end (the rightmost edge) is reached, the system obtains the width of the second bar and this value is stored to the memory as well. Now the system knows the widths of all three parts of a single marking 9.
  • the wider part of this pair of parts is eO, and this width is divided by two (i.e. halved).
  • the width of eO/2 is bigger than the width of e1 .
  • This calculation logic is also in line with the embodiment showing the dimensions in Figure 4a. Still, some other values for the widths and spac- ings can still be used so that the above calculation logic still obtains the correct results.
  • the system can decode the binary sequence to be "0 0 1 " in this case, which in decimal system means number "1 ".
  • the thin bar or spacing represents a binary value "0”
  • the wide bar or spacing represents a binary value "1 ". This is formulated as plain data without any preamble or checksum.
  • the width sum of the all the parts present within a single marking 9 or symbol can be used to compensate the marking width in the determination of the correct and accurate position.
  • the system uses a complete marking 9 as a new reference point, and when determining the travelled distance by the sensor, it takes the travelled distance between the markings 9 in the account and also the width of a single marking 9 from its left edge to its right edge. This way the correct and accurate positioning information is obtained.
  • the present invention can be implemented even so that the number of bits used in the coding is freely selectable; meaning that more than just two- or three-bar coding schemes can be applied in situations where a vast number of different markings 9 along a long rod is required.
  • the rod does not need to be very long but the required accuracy of the movement lengths requires the markings 9 to locate very close to one another.
  • the coding scheme may thus have N bars (either thin or wide) and "N-1 " spacings (either thin or wide) between these bars. The position tracking system and its controller need to be aware of the coding scheme applied in the used application.
  • Figure 5 illustrates a sensor integrated within a cylinder acting with compressed air.
  • the cylinder can be manufactured from e.g. metal or hard plastic.
  • the same principle can alternatively be implemented with a hydraulic cylinder as well, as one possible embodiment.
  • Figure 5 shows a vertical cross-section through the arrangement.
  • a piston assembly 1 is shown in the left-hand side of the figure as a vertically placed object within a barrel 1 1 , and where the piston assembly 1 is placed and fixed in an orthogonal direction with a piston rod 8.
  • the fixing can be made with a selected fixing means such as by screw-type fastening means (as indicated in the figure).
  • the piston rod 8 is depicted as a horizontal cylinder-shaped element which has laser engraved markings 9 (with two symbols shown) on its surface with given intervals along the piston rod 8.
  • the optical sensor 3 locates in- side the front cover 6, and it faces the surface of the piston rod 8.
  • the optical sensor 3 is secured to the front cover 6 of the housing or frame by a lock ring 4 and by an O-ring 5.
  • On the other side of the barrel 1 1 i.e.
  • connection cable 2 connecting the sensor to a main controller of the system or to a data acquisition device.
  • the sensor may comprise a microcontroller so that these two parts of the arrangement are integrated together.
  • the optical sensor 3 it is in one embodiment based on a high speed and low resolution camera. As discussed earlier, the principle of the camera is to take pictures consequentially, and to compare these pictures in the sequence in order to determine, how the current image and its characteristics are situated compared to the previous image. Based on the determined directional change, the system is able to determine how much the sensor has moved in relation to the sur- face locating underneath it.
  • the sensor system thus needs at least some pattern on the surface of the cylinder which is e.g. made from metal.
  • the surface of the cylinder which is e.g. made from metal.
  • almost all applicable materials and their surfaces have such a pattern, as such, without any further action required in the surface of the cylinder, other than the symbol markings, of course. This applies even for shiny metallic piston rods.
  • the main principle is to output incremental movement data which is sampled in a microcontroller on the sensor itself, in one embodiment. This principle can be called as incremental tracking.
  • the movement data can then be added to an inter- nal variable representing the position.
  • the movement data can also be used to measure the relative speed of the surface in relation to the sensor.
  • the sensor output data can be adjusted within a preselected range of 100 ... 8200 counts per inch (or "CPI").
  • CPI counts per inch
  • the material of the rod or cylinder can be e.g. metal, hard plastic, or ceramic substance, the surface quality can vary as well.
  • the mounting distance and the individual characteristics of the sensors the above value within the range can differ between installations. Therefore, it is beneficial to calibrate the sensor so that with a given position the sensor position information is accurately obtained, i.e. the sensor is calibrated in this regard.
  • the position reference point is accurately known, all the movement can be calculated in view of the obtained reference point.
  • the error occurring in the measured position is relative to the measured length from the reference point. For instance in an example, the error can be 1 % of the measured distance from the reference point. Therefore, in practice, the absolute value of the error increases when the measured position values increase from the reference position.
  • a so-called semi-absolute tracking can be applied instead of an incremental tracking.
  • This name is just derived for explaining purposes so therefore there is no accomplished meaning in this phrase.
  • the semi-absolute tracking we mean that there are plurality of fixed reference points, which are represented by the code bar markings. Thus, each marking is detected and when the marking is recognized, its position is marked as a reference point, such in the above incremental tracking principle discussed this matter.
  • the semi- absolute tracking when the whole cylinder length with markings has been gone through, there are obtained the same number of reference points for the location as there are markings on the cylinder or the rod. Therefore, all the positional information can be measured from the previous marking and not from the starting point of the rod (i.e. left end of the rod).
  • the positional error will then be e.g. 1 % of the distance to the previous marking which gives significantly better positional data compared to the incremental tracking method with a single reference point only.
  • the bar code markings are beneficially placed in uniform intervals along the cylindrical rod.
  • the marking is detected and recognized the following way.
  • the sensor chip will automatically change the shutter speed after every sampled image has been taken. This is done in order to compensate for different light conditions and in order to create a high contrast image for obtaining a better tracking performance.
  • the shutter values corresponding to various different lighting conditions and surface characteristics of the cylindrical rod can be saved to the sensor chip.
  • the microcontroller of the system is able to read these values and to pick the cor- rect shutter speed value for each location to be imaged.
  • the shutter value can of course be a relatively low value when a shiny rod is imaged.
  • a black area requires increasing of the shutter value.
  • the same logic applies preferably also to black areas of the bars and the spacings between the (black) bars. This makes the recognition of the bar and spacing widths more accurate and thus, more reliable.
  • either the cylinder or the optical sensor can move while the other one is stationary.
  • the cylinder with the markings moves along the axis defined by the cylinder itself, and the optical sensor in either an external fixed element, or placed e.g. on a jacket surrounding the cylinder.
  • the jacket we mean the external concentric element or pipe-type of a structure which surrounds the moving cylinder.
  • the optical sensor needs to of course locate on an inner surface of such a pipe-shaped jacket structure.
  • the absolute positioning in the hydraulic and pneumatic cylinders is a main application area.
  • the end dampening and stop sensors in the hydraulic cylinders can be implemented with the present invention.
  • the present invention has a great advantage because in prior art applications, even four individual sensors have been required, one close to each end indicating when to slow down the movement and one in each end to indicate full stop.
  • the present invention only a single position tracking sensor using only two markings is much more cost-effective solution for the same purpose.
  • the present invention is suitable for automated vehicle use as well, e.g. for autonomous forklifts.
  • the present invention is highly suitable for detecting intermediate exact positions in long travel machines, such as cranes, elevators, and automated warehouse systems.
  • long travel machines such as cranes, elevators, and automated warehouse systems.
  • the markings can be manufactured in the critical area or range of the moving cylinder.
  • the markings can also be manufactured in an irregular, but relatively thick manner along a certain important range along the moving cylinder, and in less thick fashion elsewhere along the cylinder. With thickness we mean the gaps between two subsequent symbols along the cylinder; the thicker manner means smaller gaps (i.e. more symbols per absolute length unit) in this context.
  • a further purpose for the present invention is to measure manufactured lengths of various bars, rods, sheets or otherwise shaped objects. Furthermore, two-dimensional movements are also trackable with the principle of the position tracking sensor.
  • the position information from a hydraulic cylinder mounted on an excavator when taking the excavator's geometry into account, can be used to calculate the position of the bucket in relation to the center of the excavator. This information can later be used to inform the driver about the depth of the digging.
  • Another possible use on heavy machinery is to use the cylinder's speed data as feedback when controlling the movements of the cylinder, thus restricting excess flow when it is not needed. This results in energy savings.
  • the options and advantages of the present invention are thus various.
  • the measured position or distance information accompanied with pressure information in the cylinders allows calculating the power.
  • the information obtained from a gym device or a rehabilitation device after the exercising session performed by the user can be also shown directly to the user and/or saved to a database.
  • the saved information can be presented to a specialist, such as a doctor or a physiotherapist, either locally or via transferring the data to an external computer or even to a cloud service.
  • the examination by a specialist can also be performed immediately after the exercise or afterwards by examining the saved pieces of information e.g. in a medical center.
  • the present invention can be used e.g. in following up rehabilitation or detecting e.g. differences in strength of the left and right side muscles of the user.
  • the position information of the performed movement can be used in giving feedback or instructions to the user, whether a performed movement is correctly or sufficiently performed (regarding the magnitude of the movement). This is done in order to avoid any injuries after e.g. an operation.
  • This indication of feedback can be either visual or audible or both.
  • range limiters or other kinds of physical “barriers" can be used in the actuators in order to prevent movement over a predetermined location.
  • the present invention comprises also a corresponding method and use (i.e. application areas) for the presented method and apparatus.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Electromagnetism (AREA)
  • Power Engineering (AREA)
  • Length Measuring Devices With Unspecified Measuring Means (AREA)

Abstract

La présente invention concerne un procédé et un agencement de détermination de position d'un élément mobile (8) par rapport à un élément fixe. L'invention applique des marquages (9) sur l'élément mobile (8) formulés sous la forme de codes à barres dans des intervalles uniformes ou non uniformes le long d'un élément mobile en forme de barre ou de cylindre (8). Le codage utilise au moins deux barres et des espacements entre les barres, et les barres et les espacements peuvent présenter une largeur large ou fine. Par la comparaison des largeurs des parties et également par l'incorporation d'un partage en deux d'une partie dans les calculs, l'agencement permet de définir une séquence de bits pour un marquage détecté (9). Les marquages (9) peuvent être agencés en un nombre naturel croissant. Lorsque les symboles détectés derrière les marquages (9), les intervalles entre les marquages et les longueurs de chaque marquage sont connus, un positionnement précis le long de l'élément mobile (8) est obtenu. Dans un mode de réalisation, la partie plus large est de 2,5 fois plus large que la partie fine. Le capteur optique (3) peut appliquer un suivi incrémentiel dans la détermination des caractéristiques de l'image détectée lorsque l'élément mobile (8) se déplace en vue de l'élément fixe. Les zones d'application comprennent, par exemple, des cylindres hydrauliques et pneumatiques en général, des machines industrielles, des applications de véhicule et, en outre, des dispositifs de santé, de rééducation et de gymnastique pour divers utilisateurs et patients.
PCT/FI2018/050300 2017-04-27 2018-04-25 Agencement de mesure de mouvement WO2018197752A1 (fr)

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FI20175374A FI127477B (en) 2017-04-27 2017-04-27 Arrangement for measuring movement

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CN109920266A (zh) * 2019-02-20 2019-06-21 武汉理工大学 一种智能车辆定位方法
CN112408273A (zh) * 2020-12-03 2021-02-26 三一海洋重工有限公司 一种门架区域检测装置及堆高机
CN113447670A (zh) * 2021-06-25 2021-09-28 福州大学 一种单目线阵视觉追踪条纹编码标志的转速测量方法及系统

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CN118999403B (zh) * 2024-10-23 2025-01-24 临沂振铭机械有限公司 适用于大型齿轮自动化加工的齿轮轮廓标定方法

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