WO2019091512A1 - Procédé et dispositif de détermination de la position d'un piston d'un cylindre hydraulique d'une machine-outil - Google Patents

Procédé et dispositif de détermination de la position d'un piston d'un cylindre hydraulique d'une machine-outil Download PDF

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Publication number
WO2019091512A1
WO2019091512A1 PCT/DE2018/100875 DE2018100875W WO2019091512A1 WO 2019091512 A1 WO2019091512 A1 WO 2019091512A1 DE 2018100875 W DE2018100875 W DE 2018100875W WO 2019091512 A1 WO2019091512 A1 WO 2019091512A1
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WO
WIPO (PCT)
Prior art keywords
piston
signal
hydraulic cylinder
reference signal
cylinder
Prior art date
Application number
PCT/DE2018/100875
Other languages
German (de)
English (en)
Inventor
Herbert Wieser
Matthias Streller
Robert Schmidt
Original Assignee
Grob-Werke Gmbh & Co. Kg
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 Grob-Werke Gmbh & Co. Kg filed Critical Grob-Werke Gmbh & Co. Kg
Publication of WO2019091512A1 publication Critical patent/WO2019091512A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/88—Sonar systems specially adapted for specific applications
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
    • B23Q3/00—Devices holding, supporting, or positioning work or tools, of a kind normally removable from the machine
    • B23Q3/02—Devices holding, supporting, or positioning work or tools, of a kind normally removable from the machine for mounting on a work-table, tool-slide, or analogous part
    • B23Q3/06—Work-clamping means
    • B23Q3/08—Work-clamping means other than mechanically-actuated
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/20—Other details, e.g. assembly with regulating devices
    • F15B15/28—Means for indicating the position, e.g. end of stroke
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/20—Other details, e.g. assembly with regulating devices
    • F15B15/28—Means for indicating the position, e.g. end of stroke
    • F15B15/2815—Position sensing, i.e. means for continuous measurement of position, e.g. LVDT
    • F15B15/2884—Position sensing, i.e. means for continuous measurement of position, e.g. LVDT using sound, e.g. ultrasound
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B17/00—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/02—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems using reflection of acoustic waves
    • G01S15/06—Systems determining the position data of a target
    • G01S15/08—Systems for measuring distance only
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/52004—Means for monitoring or calibrating
    • G01S7/52006—Means for monitoring or calibrating with provision for compensating the effects of temperature
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
    • B23Q3/00—Devices holding, supporting, or positioning work or tools, of a kind normally removable from the machine
    • B23Q3/02—Devices holding, supporting, or positioning work or tools, of a kind normally removable from the machine for mounting on a work-table, tool-slide, or analogous part
    • B23Q3/06—Work-clamping means
    • B23Q3/08—Work-clamping means other than mechanically-actuated
    • B23Q3/082—Work-clamping means other than mechanically-actuated hydraulically actuated
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/52004—Means for monitoring or calibrating
    • G01S2007/52014—Means for monitoring or calibrating involving a reference reflector integrated in the sensor or transducer configuration

Definitions

  • the invention relates to a method for determining the position of a piston of a hydraulic cylinder of a machine tool. Furthermore, the invention relates to a device for determining the position of a piston of a
  • Hydraulic cylinder for a machine tool. Furthermore, the invention relates to a hydraulic cylinder unit for a machine tool with such
  • the invention relates to a computer program product with a computer program for loading into a computer system connected to a hydraulic cylinder power tool to the piston positioning method at the
  • the invention is in the field of machine tools and in particular in the field of machine tools with hydraulic cylinders.
  • hydraulic tensioning cylinders of machine tools in particular workpieces such as e.g. Cylinder blocks or cylinder heads of internal combustion engines,
  • Cylinder walls should be as stable as possible and weak points such as windows or
  • Recesses are undesirable. In addition, the operating temperatures vary greatly.
  • a volume flow of the hydraulic fluid in the inflow or outflow of the clamping cylinder is measured.
  • Hydraulic clamping cylinder suitable for machine tools all of which provide windows or at least recesses on the cylinder wall, not for as high pressures, such as occur in hydraulic cylinders for machine tools, are suitable and at such operating temperature fluctuations and at such small adjustment ranges as hydraulic clamping cylinder of
  • Machine tools occur to deliver no usable signals.
  • the invention has for its object to provide a method and an apparatus with which the position of a piston of a hydraulic cylinder of a machine tool can be determined more accurately.
  • the invention provides a method with the steps of claim 1 and an apparatus having the features of claim 7.
  • the invention provides, according to a first aspect thereof, a method for determining the position of a piston of a hydraulic cylinder
  • Machine tool comprising:
  • Reference position located piston and detecting an echo signal as
  • piezoelectric transducer takes place, which is attached to the outside of the cylinder wall formed entirely of metal.
  • the sound transducer in particular piezo transducer, can be arranged directly on the cylinder wall. But it can also intermediate layers between the cylinder wall and the
  • the transducer can be part of a
  • a first sound transducer for generating the sound waves transmitter
  • a second sound transducer for Converting the received sound waves into electrical signals
  • a cylinder bottom extending transversely to the direction of movement of the piston is selected.
  • step c) comprises forming a difference signal from the measurement signal and the reference signal.
  • step a) comprises:
  • step a) comprises:
  • step a) comprises:
  • step a) selecting one of the end positions of the piston as the reference position. It is preferred that step a) comprises:
  • step a) comprises:
  • step a) comprises:
  • step a) comprises:
  • step a) comprises:
  • Reference signal is dissimilar.
  • step a) comprises:
  • the position of the piston on a hydraulic cylinder at a pressure of above 10 bar, in particular above 50 bar and more in particular in a pressure range of 10 bar to 150 bar, is determined.
  • the position of the piston on a hydraulic cylinder is determined with a piston stroke in the range of 0 to 100 mm, more preferably 0 to 50.0 mm.
  • the position of the piston on a hydraulic cylinder is determined with a distance of a sound transmission and reception position to the piston of less than 200 mm, in particular less than 100 mm and in particular in a range of 1 mm to 50 mm.
  • the method further comprises:
  • the invention provides a device for
  • Machine tool comprising:
  • Sound transmission and reception device for transmitting and receiving acoustic signals through the cylinder wall in the direction of the piston and a control and evaluation device for the sound transmission and reception device
  • control and evaluation device is designed:
  • the sound transmission and reception means for driving the sound transmission and reception means for transmitting an acoustic signal through the cylinder wall of the hydraulic cylinder to the piston located at a reference position and for recording thereupon a sound transmitted and received by the sound transmission and reception means
  • the sound transmission and reception device for driving the sound transmission and reception device for transmitting the acoustic signal through the cylinder wall to the piston located in the position to be measured and for detecting the subsequently received echo signal as a measurement signal
  • a first and a second piston for determining the transit time from the comparison signal to determine from the transit time the position of the piston.
  • the device may also be configured to detect the position of more than one piston. For example, a first and a second piston
  • Hydraulic cylinder be provided, for which the position of a piston can be determined by a common control and evaluation.
  • a hydraulic cylinder unit with several pistons may also be provided, e.g.
  • the sound transmission and reception device has a particular piezoelectric sound transducer.
  • control and evaluation device is designed to be a difference signal from the measurement signal and the
  • control and evaluation device is designed to generate the reference signal several times in the course of the operation of the
  • control and evaluation device is designed for moving the hydraulic cylinder into the reference position.
  • control and evaluation device is designed to select one of the end positions of the piston as the reference position.
  • control and evaluation device is designed to select that position of the piston which causes the greatest transit time for the echo signal as the reference position.
  • control and evaluation device is designed to store the reference signal or a plurality of reference signals detected at different times or different operating conditions in a memory. It is preferred that the control and evaluation device is designed to detect a plurality of reference signals for different operating temperatures.
  • control and evaluation device is designed to store the reference signal together with information about at least one present during the detection of the reference signal
  • control and evaluation device is designed to detect the reference signal, compare the detected reference signal with at least one previously stored further reference signal, use the stored or a stored reference signal, if this is the same or similar to the detected, and use and store the detected reference signal when it is dissimilar to the at least one stored reference signal.
  • control and evaluation device is designed to detect the reference signal before each movement of the piston to a position to be measured towards or before or after a predetermined number of position determinations or after a predetermined period of time since the last reference value determination or since the last Position determination or depending on a change of an operating parameter of
  • the invention provides a hydraulic cylinder unit for a machine tool comprising:
  • a hydraulic cylinder in particular clamping cylinder, with a cylinder whose cylinder walls are formed entirely of a metal, and a piston movable in the cylinder;
  • the sound transmitting and receiving device is mounted externally on the cylinder wall.
  • the hydraulic cylinder is designed for a pressure range from 10 bar to 100 bar, in particular 10 bar to 150 bar.
  • the piston has a stroke measured by a
  • Cylinder bottom, on the outside of the sound transmitting and receiving device is mounted in a range between 0 mm and 100 mm, more preferably between 0 mm and 50.0 mm.
  • a first reflection region for reflecting the acoustic signal and a second reflection region for reflecting the acoustic signal is provided such that the reflection regions have a defined distance from each other in the running direction of the acoustic signal, and that the control and evaluation device is formed is for determining a transit time difference between an echo signal from the first one
  • Reflection area and an echo signal from the second reflection area are Reflection area and an echo signal from the second reflection area.
  • the invention provides a machine tool comprising a hydraulic cylinder unit according to one or more of the previously discussed embodiments.
  • the invention provides a
  • a computer program product or computer readable computer program medium comprising control instructions for carrying out the steps of the method for determining the position of a piston of a computer
  • Embodiments when loaded into a computer when loaded into a computer.
  • a machine tool such as a machining center
  • the safe operation of hydraulic cylinders can be achieved by determining the piston position in the hydraulic cylinder.
  • the current piston position is also reported during a piston movement.
  • Particularly preferred embodiments of the invention relate to a method and a device for determining the position of the piston in hydraulic cylinders made of metal, in particular steel, in machining centers based on acoustic
  • Preferred embodiments of the invention use ultrasound, pulse-echo method, reference formation and / or transit time measurement.
  • the invention is based on the basic idea of measuring the position of the piston directly acoustically, in particular by means of ultrasound.
  • Machine tools the problem that as possible no interference with the cylinder and in particular no interference with the formation of the cylinder wall should be made and also the cylinder wall is formed of solid metallic materials.
  • windows or breakthroughs - as provided in the method according to [2] to [1 1] - are avoided.
  • Preferred embodiments of the invention therefore go the way to perform the measurement through a cylinder wall.
  • Hydraulic fluid to an impedance jump leads to reflections. With only very small adjustment can be at the transition between
  • preferred embodiments of the invention provide a Generation of a reference signal, which is a kind of fingerprint for the hydraulic cylinder to be measured and can be used in a comparative measurement to obtain the actual measurement signal.
  • the sensor is referenced via the fingerprint procedure; e.g. in which
  • the sensor element may e.g. be attached externally to the cylinder wall, in particular to the cylinder bottom, e.g.
  • the sensor can be connected directly to an actuator for actuating the cylinder
  • Pistons of hydraulic cylinders of machine tools see, for example, [1]
  • the position value of the piston is detected much faster and reported to the controller - thus can achieve a cycle time reduction for the machine tool.
  • FIG. 1 is a highly schematic representation of a machine tool with a clamping device, the hydraulic cylinder units for clamping a workpiece with hydraulic cylinders and a device for determining the position of the piston of the hydraulic cylinder has;
  • Fig. 2 shows another embodiment of the hydraulic cylinder unit for the
  • Fig. 3 is a schematic representation of a hydraulic cylinder for a
  • Hydraulic cylinder unit together with a sensor element of a device for determining the position of the piston
  • FIG. 4 shows an enlarged representation of a part from FIG. 3 for explaining a method for determining the position of the piston by means of acoustic signals
  • FIG. 6 is a representation comparable to FIG. 4 in another
  • Embodiment of the hydraulic cylinder unit for explaining a further embodiment of the method for determining the position of the piston.
  • FIG. 1 an embodiment of a machine tool 10 is shown very schematically.
  • the machine tool 10 is designed, for example, for machining a workpiece 12 and has a tool spindle 14, which is shown in a highly schematized manner, with a tool carrier on which a plurality of e.g. from a tool magazine 16 selectable and automatically replaceable tools 18 are attached, and a clamping device 20 for clamping the workpiece 12.
  • Tool spindle 14 are movable relative to each other to perform the machining. Furthermore, a control device 22 for controlling the machine tool 10 is provided.
  • the machine tool 10 can be designed, for example, as a machining center or as part of a machining center, as described and shown, for example, in one of the following references [12] to [19], to which reference is expressly made for further details of the machine tool 10:
  • the workpiece 12 may be, for example, an engine block of an internal combustion engine whose cylinder is machined, e.g. are produced by milling or to edit. According to the forces occurring during such machining and the desired precision, the workpiece 12 must be clamped very firmly and very precisely positioned.
  • the clamping device 12 has at least one hydraulic cylinder unit 24, which has at least one hydraulic cylinder 26 and a device 28 for determining the position of a piston 30 of the piston
  • Hydraulic cylinder 26 has.
  • a plurality of hydraulic cylinders 26 are provided, each bounded by a cylinder walls 32
  • Hydraulic chambers 36, 38 are formed. With valves 40, 42 provided
  • Hydraulic lines 44, 46 are from a hydraulic system 48, the
  • Hydraulic fluid 50 at high pressure delivers, led to the hydraulic chambers 36, 38.
  • Actuation of the valves 40, 42 are moved and set for clamping under pressure.
  • the hydraulic cylinder unit 24 is provided with the device 28 for determining the position of the piston.
  • Device 28 for determining the position of the piston has, as a sensor element 52 an externally attachable to a cylinder wall 32 of the hydraulic cylinder 26 sound transmitting and receiving device 54 for transmitting and receiving acoustic signals through the cylinder wall 32 in the direction of the piston 30 and a control and Evaluation device 56 for the sound transmission and reception device 54 on.
  • the latter is shown in Fig. 1 as part of the control device 22 and for simultaneously controlling and evaluating a plurality of sound transmission and
  • Receiving devices 54 designed different hydraulic cylinders 26, may be formed in other embodiments, as indicated in Fig. 2, but also separately and for example on each hydraulic cylinder 26, e.g. be arranged on the valves 40, 42.
  • Hydraulic cylinder 26 is formed such that by extending the piston 30, the workpiece 12 is clamped against abutment devices 58. Presently more preferred is the embodiment shown in FIG.
  • Clamping device 20 in which the workpiece 12 is tensioned by retraction of the piston 30 against an abutment device 58.
  • Hydraulic cylinder 26 the device 28 for determining the position of
  • FIG. 3 is a schematic representation of the hydraulic cylinder 26 with piston 30, a piezo element, hydraulic fluid 50 and cylinder walls 32.
  • FIG. 4 is a detailed illustration of acoustic paths and the relevant interfaces 68, 76 between cylinder wall 32 and hydraulic fluid 50 and between pistons 30, in particular Piston head 72, and hydraulic fluid 50.
  • the hydraulic cylinder 26 has cylindrical walls 32 made of metal and more
  • the pressure range of the hydraulic cylinder 26 is 10 to 150 bar.
  • the stroke of the piston 30 is e.g. 0 to 50.0 mm.
  • the wall thickness of the cylinder walls 32 is e.g. 3 mm to 20 mm.
  • Piston 30 without modification of the hydraulic cylinder 26 and without intervention in the same very accurately.
  • the sensor element 52 is externally applied to the cylinder bottom 62 in the illustrated embodiments, in particular adhesively bonded.
  • the sensor element 52 includes the sound transmitting and receiving device 54, the one or more sound transducer 66, in particular designed as
  • a sound transducer 66 is provided, which is designed both for transmitting sound, insbesondre a sound pulse, more particularly an ultrasonic pulse, as well as for receiving an echo, which is generated by the sound at interfaces. For others, not shown here
  • the mechanical structure of the system includes the components cylinder housing 65 - with the cylinder walls 32 - piston 30 and a sound-generating piezoelectric element, short sound transducer 66th
  • the cylinder housing 65 is made of a metallic material such as
  • a hydraulic fluid 50 Inside the cylinder housing 65 is a hydraulic fluid 50.
  • the generation of an acoustic signal in the form of a compression wave 64 is effected by a sound transducer 66.
  • Sound transducer 66 via a permanent non-positive connection, such as adhesive bonding, with the cylinder bottom 62nd
  • Deflection may propagate as a compression shaft 64 in the cylinder bottom 62 at a typical material speed.
  • Interface 68 cylinder bottom / hydraulic fluid in the hydraulic fluid 50 is transmitted, in which also a sound wave or compression wave 64 can propagate. This is after passage of the hydraulic fluid 50 am
  • Piston floor 72 reflects and reaches again after passing through the first interface 68 cylinder bottom / hydraulic fluid and the cylinder bottom 62 also the transducer 66. This represents the echo signal 74 of the piston 30, which is used for position determination.
  • a referencing method is used, which is referred to below as the fingerprint method.
  • a fingerprint sets the unique for the used cylinder configuration acoustic echo signal of the entire cylinder, i. in particular all immobile parts in the cylinder, which also includes the multiple reflections 70 of the sound wave in the cylinder bottom 62.
  • This echo signal is from the
  • the fingerprint of the hydraulic cylinder 26 is received in the fully extended piston 30 state. After changing the position, the fingerprint is subtracted from the current measurement signal. While this subtraction reduces the echoes 70 of the cylinder bottom 62 to an amplitude value of zero, the echo signals 74 are retained by the piston crown 72 since these are dependent on the position of the piston 30. Since the method is referencing, it is susceptible to changes in the
  • Hydraulic cylinder 26 is performed, as shown in Fig. 5.
  • FIG. 5 shows a flow chart of the fingerprint method with continuous re-referencing and describes the following sequence of steps S1 to S7 using the example of a hydraulic cylinder 26 of the configuration of a clamping device 22 shown in FIG. 2:
  • Reference signal which takes into account the configuration and parameters of the hydraulic cylinder, the piston 30 moved to a reference position.
  • the method for determining the position of a piston 30 of a hydraulic cylinder 26 of a machine tool 10 accordingly comprises the steps:
  • control and evaluation device 56 The steps for sending and evaluating are controlled in particular by the control and evaluation device 56.
  • a preferred embodiment of the method including control and evaluation and in particular of the algorithms used therein will be explained in more detail below.
  • Embodiment is an FPGA 78 (Field Programmable Gate Array), which is an embodiment of a central processing unit of the control and
  • Evaluation device 56 represents.
  • a two-fold square burst signal with a frequency of 2 MHz is generated in the FPGA 78. This is pre-amplified, and the
  • Sound transducer 66 is excited with it. Due to the inverse piezoelectric effect, the sound transducer 66 is set in oscillation at the excited frequency. Since the transducer 66 is frictionally coupled to the cylinder bottom 62, so a sound wave - compression wave 64 - is generated in this, which passes through the cylinder bottom 62 and coupled into the hydraulic fluid 50 of the hydraulic cylinder 26.
  • the sound wave - compression wave 64 - passes through the hydraulic fluid 50, is reflected at the piston head 72 of the corresponding piston 30 and finally converted in the transducer 66 back into an electrical signal.
  • the actual position of the piston 30 corresponds to the transit time of the signal through the hydraulic fluid 50.
  • the electrical signal thus generated is processed on the central electronics by means of various filter and amplifier stages, digitized in an analog-to-digital converter and the FPGA 78 for further processing made available.
  • the sampling of the signal happens eg at 50 MHz.
  • the signal is stored in the FPGA 78 as an array of several thousand samples, eg with a width of 12 bits each.
  • the fingerprint method is preferably a
  • the actual fingerprint is measured when the piston is fully extended, e.g. in the embodiment of Fig. 2 in the relaxed state, recorded and stored.
  • the resulting difference signal has a unique maximum, which corresponds to the position of the piston 30 in
  • Hydraulic cylinder 26 corresponds.
  • a regular update of the fingerprint is provided to compensate for any existing temperature drift of the mechanical total system. As the temperature of the hydraulic fluid changes, so does the speed of sound in it. If the temperature change is too great, the difference formation leads to defects in the
  • the storage of the fingerprint together with information about an operating parameter, e.g. the time of the recording or one of them
  • the currently used fingerprint is filled with the currently available signal
  • the current fingerprint is classified as invalid, but remains in memory 80.
  • the present signal when fully extended piston 30 is compared with other fingerprints that may already be present in the memory 80. If a fingerprint matching the current signal is found, it will be used. If this is not the case, the current signal becomes the new current fingerprint. In this way arises in the course of the operating time of the system a number of
  • Fingerprints that have been recorded at different temperatures and can compensate for a possible temperature drift of the system.
  • a constant re-referencing prior to each clamping operation i. explained before each movement of the piston 30.
  • previously stored reference signals can be used.
  • the recording of new reference signals can be done as needed. It is also conceivable to perform a new referencing after a certain number of piston movements or after a certain time has elapsed since the last reference signal formation. Also conceivable is parameter-dependent re-referencing, e.g. making a new one
  • the piston 30 is shown with a flat piston crown 72, wherein the second interface 76 formed thereon constitutes a uniform reflection region for forming the echo signal 74.
  • FIG. 6 shows a further embodiment of the hydraulic cylinder unit 22 with hydraulic cylinder 26, piston 30 and sensor element 52-externally mounted sound transducer 66-in which defined, different transit time paths are provided.
  • the piston 30, for example on the piston head 72 has a first reflection region 82 and a second reflection region 84.
  • the second reflection region 84 can be formed, for example, by a groove or a bore 86 in the piston bottom.
  • the first reflection region 82 and the second reflection region 84 have a defined distance A from each other.
  • Air bubbles in the hydraulic fluid 50 occur.
  • the above is a fingerprint or subtraction method for
  • Piston position determination in cylinders of machine tools 10 explained.
  • the method can be carried out in a correspondingly programmed computer system, which is connected to the hydraulic cylinder 26 and a sensor element 52 attached thereto.
  • a sensor element 52 attached thereto.
  • an electronics made of adapted standard elements can be used. The in the tax and
  • the evaluation device and / or the control device 22 for carrying out the piston position determination method control instructions may be present as software that may be stored in a computer program product or a computer program medium.
  • a sound transducer 66 one or more piezo elements can be used, as they are already known in principle. It can to that extent on the
  • the sound transducer 66 may be soldered or glued on a circuit board in some embodiments. In some embodiments, parts of analog electronics may already be present in the immediate vicinity of the sound transducer 66, eg a preamplifier. As mentioned above, separate transducers 66 can be used for transmission and reception.
  • the sound transmitting and receiving device 54 which has the one or more of the sound transducer 66 and electronic parts and possibly a circuit board, in a housing (not shown) and screwed to the cylinder base 62.
  • Sensor element 52 / transducer 66 is required, and the emission takes place only on one side from the bottom to the piston.
  • two sound transducers 66 are mounted on the cylinder wall 32, in particular on the cylinder bottom 65, namely a sound transducer for generating the sound waves (transmitter) and a second transducer for converting the received sound waves into electrical signals (ie Receiver), instead of doing so in just one transducer 66, which is the transmitter and receiver at the same time.
  • An additional reference running path with a defined length A can be attached to the piston head 72, e.g. by introducing a groove or bore 86. Then the acoustic signal - e.g. the compression shaft 64, in particular formed as an ultrasonic signal - from the piston head 72 due to the additional transit time through the reference running distance A at different times reflected (i.e., once from the unchanged piston crown 72 - first
  • Reflection area 82 and another reflection from the groove o. second reflection area 84). This creates an additional sound running distance with a defined length (2 times A).
  • Duration difference between the two positions ie running time at reflection from the normal piston crown and running time at reflection from the groove, etc.
  • properties of the hydraulic fluid esp. Aging, temperature, air bubbles
  • Air bubbles can be a major problem with hydraulic cylinders used as tension cylinders; therefore, a detection is eg by means of the additional reference run for the planned

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  • Computer Networks & Wireless Communication (AREA)
  • Mechanical Engineering (AREA)
  • Fluid Mechanics (AREA)
  • General Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
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Abstract

L'invention concerne un procédé et un dispositif (28) destinés à déterminer la position d'un piston (30) d'un cylindre hydraulique (26) d'une machine-outil (10). Afin de permettre une détection de position plus précise, en particulier pour surveiller la fonction du cylindre hydraulique (26) pendant le fonctionnement de la machine-outil (10), le procédé comprend les étapes suivantes : a) générer un signal de référence par émission d'un signal acoustique à travers une paroi (32) du cylindre hydraulique (26) sur le piston (30) se trouvant dans une position de référence et détecter un signal écho comme signal de référence et b) envoyer le signal acoustique à travers la paroi de cylindre (32) sur le piston (30) pour déterminer la position de celui-ci et détecter le signal écho comme signal de mesure et c) générer un signal de comparaison à partir du signal de mesure et du signal de référence et d) déterminer le temps de propagation à partir du signal de comparaison afin de déterminer la position du piston (30) à partir du temps de propagation. Le dispositif (28) est conçu de manière correspondante pour mettre en œuvre le procédé. En outre, l'invention concerne une unité de cylindre hydraulique (24) munie du dispositif, ainsi qu'une machine-outil (10) munie de celle-ci.
PCT/DE2018/100875 2017-11-10 2018-10-26 Procédé et dispositif de détermination de la position d'un piston d'un cylindre hydraulique d'une machine-outil WO2019091512A1 (fr)

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DE102017126494.9 2017-11-10
DE102017129445.7 2017-12-11
DE102017129445.7A DE102017129445A1 (de) 2017-11-10 2017-12-11 Verfahren und Vorrichtung zur Bestimmung der Position eines Kolbens eines Hydraulikzylinders einer Werkzeugmaschine

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DE102020113272A1 (de) * 2020-05-15 2021-11-18 Weber-Hydraulik Gmbh Schwingungsbasierte Wegmessung für lineare Aktuatoren

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