WO2019130233A1 - Transducteur de position linéaire sans contact - Google Patents

Transducteur de position linéaire sans contact Download PDF

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Publication number
WO2019130233A1
WO2019130233A1 PCT/IB2018/060645 IB2018060645W WO2019130233A1 WO 2019130233 A1 WO2019130233 A1 WO 2019130233A1 IB 2018060645 W IB2018060645 W IB 2018060645W WO 2019130233 A1 WO2019130233 A1 WO 2019130233A1
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WO
WIPO (PCT)
Prior art keywords
magnetic
magnet
axis
magnetic field
development
Prior art date
Application number
PCT/IB2018/060645
Other languages
English (en)
Inventor
Damiano Crescini
Aldo ALGHISI
Davide ALGHISI
Original Assignee
Gefran S.P.A.
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 Gefran S.P.A. filed Critical Gefran S.P.A.
Priority to DE212018000387.4U priority Critical patent/DE212018000387U1/de
Publication of WO2019130233A1 publication Critical patent/WO2019130233A1/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
    • G01D5/12—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
    • G01D5/14—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 the magnitude of a current or voltage
    • G01D5/142—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 the magnitude of a current or voltage using Hall-effect devices
    • G01D5/145—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 the magnitude of a current or voltage using Hall-effect devices influenced by the relative movement between the Hall device and magnetic fields

Definitions

  • the present invention relates to a contactless linear position transducer.
  • the movable part of the electric actuators is connected to the slider of the linear position sensor, which resides outside the actuator.
  • the sensors arranged outside the actuator may be inconvenient because the mobile members of the machinery may have multiple degrees of freedom.
  • the sensor fitted on the outside of the drive risks being damaged if it is not duly protected. For this reason, all the linear position sensors which may be mounted directly inside the hydraulic or pneumatic cylinder, or more in general inside the drive, are particularly attractive.
  • Resistive sensors are known, such as the one described in Patent US 4,386,552, which use a potentiometric resistance sensor as primary element of a linear position transducer inside a cylinder.
  • This type of sensor consists of a slider, which includes a sliding electric contact and a circular resistive track on which the slider runs. The slider moves in circular motion and, by sliding, modifies the electric path of the track, thus determining a variation of the equivalent resistance between the two terminals of the resistive track.
  • the main limitations of this measuring technique concern the wear of the resistive track by the sliding contact.
  • the resistive potentiometric sensor in order to transduce the position of the cylinder rod, the resistive potentiometric sensor must be housed together with the piston coupling mechanism in the oil compartment, thus exposing the resistive track to the corrosive effects of the oil and of the impurities it contains. Finally, following a malfunction, the potentiometric sensor cannot be easily extracted to be replaced except by removing the fixed end of the cylinder in which it is housed.
  • an armature is an integral part of the piston, while the other armature may be removed only after having removed the fixed end of the hydraulic cylinder.
  • Patents US 6,234,061 and US 7,290,476 use a Linear Variable Displacement Transducer - LVDT - as primary element to determine the position of the piston rod which runs inside a hydraulic cylinder.
  • the transducer is made by means of a pipe consisting of three windings arranged with parallel axes and with a movable ferromagnetic cylindrical core inside, which is mechanically connected to the piston rod.
  • the central winding is to be considered as the primary of a transformer, which couples differently to the two secondary windings as a function of the position of the ferromagnetic core.
  • the variation of reluctance between the windings of the transformer is proportional to the displacement of the core.
  • the mechanical coupling between the ferromagnetic core and the piston rod is achieved by means of a system included inside the cylinder and consisting of a wire, fixed by one end to the tip of the rod, and by the other end to a drum provided with return spring.
  • a worm screw mechanism By means of a worm screw mechanism, the rotation of the drum is converted into the translation of a pin which, with a cam system, insists on the ferromagnetic core of the inductive displacement transducer.
  • This contactless measuring technique preserves the primary elements which form the transducer from mechanical wear.
  • the inductive sensor in order to detect the position of the piston rod, the inductive sensor must be housed inside the oil compartment, thus being subjected to its corrosive effects.
  • this transduction technique is relatively robust to the variations of the working temperature of the oil, it may suffer from the influence of the impurities present in it, such as dirt and water, which may generate an undesired variation of the reluctance, such as, if not compensated, may be erroneously interpreted as the variation of the position of the cylinder rod.
  • Magnetoresistance sensors such as those described in Patent JP 62229003A in which a magnetic displacement sensor based on magnetoresistors (Giant Magnetoresistance - GMR) is used as primary element in order to determine the position of the piston rod which runs inside a hydraulic cylinder, are known.
  • the transducer consists of one or more pairs of magnets placed inside the hydraulic cylinder and by a magnetic field intensity sensor, made by four magnetoresistors arranged as a Wheatstone bridge and positioned inside the cylinder, fixed to the piston rod.
  • the magnets of each pair are positioned in diagrammatically opposite manner with respect to the cylinder axis, thus generating a magnetic field orthogonal to the direction of displacement of the piston axis.
  • the field generated by the magnet pairs extends for its entire length.
  • the magnetoresistors can thus move within a magnetic field with intensity which is as a function of the position of the piston rod.
  • This transducer technique is contactless, so the sensing element is not subject to mechanical wear. Furthermore, although the magnetic field intensity sensor is arranged in the oil compartment, it may be duly coated with non ferromagnetic passivating material to be immune from possible corrosive effects of the oil.
  • the magnetoresistors are particularly sensing to working temperature variations. Furthermore, being positioned on the movable part of the hydraulic cylinder, they require a specific anti-twisting wiring system to be able to return the electrical signal into the mechanical apparatus by means of the appropriate connector.
  • Magnetostrictive sensors to the family of which the sensor presented in Patent EP 1571425 belongs, are a typical solution for obtaining an accurate measurement of the linear position of a movable member of a mechanical system.
  • the magnetostrictive technique is based on measuring the flight time of an acoustic wave transmitted along a magnetostrictive material wire, which is reflected back near the choke induced by a magnetic ring which runs along the wave guide.
  • This contactless technique makes it possible to obtain high measurement resolutions, but to the detriment of high costs, high susceptibility to variations of temperature, vibrations and external magnetic fields. Mechanical knocks accidentally applied to the rod containing the wave guide must compromise sensor calibration, even damaging it beyond repair.
  • Magnetic sensors are known, like those described in Patents US 8,829,893 and US 9,062,694; in said patents, an array of magnetic sensors arranged for the entire length of the fixed part of a hydraulic cylinder, coupled to one or more magnets housed in the piston rod, is used. Both in the case of magnetoresistive elements or Hall effect elements arranged in a bridge, the measuring principle is contactless, and so the primary sensing element is free from mechanical wear and its degree of protection may be increased by means of traditional passivating techniques, such as resin coating.
  • Magnetic sensors detect the intensity of the magnetic field. By querying each sensor and combining the respective outputs, it is possible to determine the rod position.
  • the merit of this solution is that the array of magnetic sensors may be positioned outside the hydraulic cylinder, thus being easily accessible for maintenance and protected from the typical mechanical and thermal stresses of the oil compartment.
  • the structure of the cylinder itself may attenuate the magnetic field produced by the movable magnets inside it, forcing the sensor array to work in conditions of poor sensitivity.
  • the sensor array is exposed to possible interferences generated by metallic or magnetic components which move near the cylinder.
  • Patent US 9,062,694 suggests to house the sensor array on a magnetic polarized support, which on one hand screens from interferences and on the other makes the magnetic field intensity measurement more robust.
  • the complexity and the cost of such transducer are directly proportional to the maximum measurable travel: the greater the length of the piston rod, the greater is the number of magnetic sensors to be arranged and the more complex become the wiring, the routing and the management of each sensing element.
  • Patent WO 2016046537 suggests the use of a sensor array, connected to the fixed end of the cylinder, which may run inside the piston rod, which is hollow.
  • a magnet also hollow, specifically worked to generate a magnetic field in its cavity with intensity which linearly varies according to its position, is included in the piston rod.
  • the position of the rod can be determined by combining the measurement of the magnetic field intensity of each sensor of the array.
  • the particular geometry of the magnet ensures an increase of the intensity of the magnetic field along the movement axis of the piston rod with respect to the preceding solutions, allowing a more dispersed positioning of the sensors which form the array.
  • the effects deriving from electromagnetic interference sources are reduced, despite being obliged to immerse the sensor electronics in the oil compartment, with all the problems of difficult accessibility in case of maintenance which derive therefrom.
  • Patents US 7,956,606 and US 9,341,266 use a single magnetic rotary sensor as primary element to determine the position of a rod which runs inside a cylindric cylinder.
  • the sensing element faces and is aligned with the center of a magnet, which rotates according to the movement of the piston rod.
  • the angular position of the polarization vector of the magnet is thus transduced by the sensing element into an electric signal.
  • the electronic board and the magnetic system, which couples the linear movement of the piston rod to the rotary movement of the magnet reside in two separate housings. This solution makes it possible to screen the magnetic sensor with respect to the interferences coming from the environment outside the cylinder. Replacing the primary sensing element following a malfunction is instead more complicated than in the system suggested in Patent US 8,829,893, because the fixed end of the hydraulic cylinder in which the electronics are housed must be removed.
  • figure 1 shows a contactless linear position transducer according to the first embodiment of the invention
  • figures 2-7 show various steps of operation of the transducer in figure i ;
  • figure 8a shows a chart of the variation of the linear displacement d as a function of the angle a
  • figure 8b shows the electronic board which can be used in the linear position transducer in figure 1;
  • figure 9 shows a linear position transducer according to a variant of the first embodiment of the present invention.
  • figures 10-1 la show a linear position transducer according to another variant of the first embodiment of the present invention.
  • figure 1 lb shows the electronic board which can be used in the linear position transducer in figure 10;
  • figures 12-15 show various steps of operation of the transducer in figure 10;
  • figure 16 shows a contactless linear position transducer according to the second embodiment of the invention.
  • figures 17-20 show various steps of operation of the transducer in figure 16;
  • figures 21, 22 and 23 show a cross section of a linear position transducer according to different embodiments
  • figures 24a-24e show steps of operation of a linear position transducer according to an embodiment
  • figure 25 shows the trend along the linear displacement d of detectable quantities during the steps of operation illustrated in figures 24a-24e;
  • figure 26 shows a table indicating quantities which can be detected and determined during steps of operation in figures 24a-24e;
  • figures 27a-27d show steps of operation of a linear position transducer according to an embodiment
  • figures 28a-28d show in table form detectable quantities during the steps of operation in figures 27a-27d;
  • figure 29 shows the trend along the linear displacement d of a detectable quantity during the steps of operation illustrated in figures 27a-27d;
  • figures 30a-30d show steps of operation of a linear position transducer according to an embodiment
  • figure 31 shows the trend along the linear displacement d of detectable quantities during the steps of operation illustrated in figures 30a-30d;
  • figures 32a-32d show steps of operation of a linear position transducer according to an embodiment
  • figure 33 shows the trend along the linear displacement d of detectable quantities during the steps of operation illustrated in figures 32a-32d;
  • figures 34a-34d show steps of operation of a linear position transducer according to an embodiment
  • figure 35 shows the trend along the linear displacement d of detectable quantities during the steps of operation illustrated in figures 34a-34d;
  • figures 36a-36d show steps of operation of a linear position transducer according to an embodiment
  • figure 37 shows the trend along the linear displacement d of detectable quantities during the steps of operation illustrated in figures 36a-36d;
  • figures 38a-38d show steps of operation of a linear position transducer according to an embodiment
  • figure 39 shows the trend along the linear displacement d of detectable quantities during the steps of operation illustrated in figures 38a-38d;
  • figure 40 shows a linear position transducer according to a further embodiment
  • figures 41 and 42 show, respectively in a perspective view and a longitudinal section view, a linear position transducer according to a further embodiment
  • figure 43 shows a linear position transducer according to a further embodiment
  • figure 44 shows a linear position transducer according to a further embodiment
  • figures 45, 46 and 47 show, in respective operating conditions, a linear position transducer according to a further embodiment.
  • the linear position transducer comprises two subsystems, one mechanical and one electronic.
  • the mechanical subsystem converts the linear movement of a magnetic slider into the rotation of a magnetic induction vector.
  • the electronic subsystem detects the angular position of the magnetic induction vector and encodes it in output proportionally to the linear position of the magnetic slider.
  • the linear position transducer comprises a magnet 9, 6, sensing means 81, 82 not in contact with said magnet and magnetically coupled to said magnet and means 2, 2a, 2b electrically connected to said sensing means and configured to output OUT, OUT’ said linear position.
  • the magnet is a helical development magnet about a respective axis of development M.
  • the magnet and/or said sensing means are configured to move linearly along the axis of development M and are fixable to an element, the position d of which it is desired to detect.
  • the sensing means 81, 82 are adapted to measure the angle of rotation a of the magnetic induction vector B, B’ produced by the magnet 9 due to the mutual linear displacement d between said sensing means and said helical development magnet and are configured to output said linear position d in response to said measurement.
  • the linear position transducer 1 of the first embodiment of the invention shown in figures 1-8 comprises a helical development magnet 9 about an axis of development M.
  • the magnet 9 preferably comprises at least one magnetic bar 6, polarized along the thickness, twisted so as to develop a hollow magnetic helix-shaped spiral of length L about the axis of development M of the position transducer 1.
  • Such length L represents the measurement full-scale of the transducer.
  • the magnetic bar 6 is twisted so as to form a single helix spiral.
  • the polarization of the magnetic bar 6 may occur with axial longitudinal magnetization using two poles (as shown in figure 21), or with axial magnetization along the thickness using four poles (as shown in figure 22) or with axial magnetization along the thickness using two poles (as shown in figure 23).
  • the polarization of the two magnetic bars 6 can occur with axial magnetization along the thickness (as shown in figures 3, 5 and 7).
  • the magnetic bars 6 can be made, for example, of anisotropic magnetic ferrite or neodymium iron boron rubber, or of injection molded plasto- ferrite.
  • the magnet 9 can be made using a hollow cylinder of magnetic material, obtained by sintering NdFeB and SmCo or AlNiCo powders by using the following techniques, for example: injection molding of NdFeB and SmCo or AlNiCo composites bound with plastic materials; compression molding of NdFeB and SmCo or AlNiCo composites bound with plastic materials; the element is then appropriately magnetized with helix profile.
  • the linear position transducer 1 of the first embodiment of the invention shown in figures 1-8 comprises a magnetic field sensor 81, with sensing axes x, y, z, of center O and orthogonal to one another; the sensor 81 is arranged along the axis M of development of the magnet, which is also the axis of the linear position transducer 1.
  • the principle of operation of the magnetic field sensor 81 can be, for example, Hall effect, giant magnetoresistance, or magnetoresistive tunnel effect.
  • the sensor 81 is carried by a hollow rod 5 arranged inside the magnet 9 along the axis of development M of the magnet.
  • the sensor 81 is arranged at the top of the hollow rod 5; an electronic board 8 which supports the magnetic field sensor 81 is arranged on the same top of the hollow rod 5.
  • the rod 5 can be made of paramagnetic material, such as aluminum or AISI 316 stainless steel.
  • the linear position transducer 1 further comprises a tubular casing 7, coaxial with and external to the at least one magnetic bar 6 wound as a spiral but preferably external to the magnetic bars 6 wound as a double helix spiral, made of ferromagnetic material and adapted to concentrate the magnetic field generated by at least one magnetic bar 6 inside the spiral and in particular on the sensor 81.
  • the sensing means 81, 82 transversally to the axis of development M are advantageously aligned with a portion of the helical development magnet 9, 6 and with a portion of the tubular casing 7.
  • sensing means 81, 82 are adapted to measure the vector components of the magnetic field generated by the helical development magnet 9, 6, such sensing means 81, 82 are working in optimal conditions, i.e. in screening conditions ensured by the portion of the tubular casing 7 with which they are aligned transversely to the longitudinal axis M. [00086].
  • tubular casing 7 made of ferromagnetic material is advantageously adapted to screen the magnetic field sensor 81 from external electromagnetic interference.
  • the tubular casing 7 can be made, for example, of AISI 400 stainless steel.
  • the length of the tubular casing 7 is either greater than or equal to the length L of the magnet 9 so as to contain the magnet 9 and the tubular casing is preferably adjacent to the magnet 9.
  • the tubular casing 7 with the magnet 9 form a magnetic slider 90 adapted to move linearly with respect to the sensor 81.
  • a sliding bearing 71 is provided for the sliding of the magnetic slider 90 along the axis M of the transducer.
  • the magnetic slider 90 has a length L developed along the axis of the transducer M and has transverse axis N orthogonal to M and passing through the middle point L/2.
  • the position transducer detects the position d between the axis N of the magnetic slider 90 with respect to the center O of the magnetic field sensor 81.
  • the magnetic slider 90 can be fixed to an element the position of which is desired to be detected.
  • a main electronic board 2 connected to the electronic board 8 by means of the electrical connection cable 4 which slides inside the rod 5, processes the components x, y, z of the magnetic induction vector B generated by at least one magnetic bar 6 to derive the magnetic angle a.
  • the electronic board 2 comprises a logic control unit 21, a power management circuit 22 and an output signal conditioning circuit 23; the electronic board 2 is arranged in a housing 24.
  • a connector 3 is present for the electrical connection to an external element.
  • the magnetic angle a is calculated by means of the vector measurement of the two magnetic induction vector components B (By, Bz), according to the formula:
  • the linear displacement of the magnetic slider 90 along the axis of the transducer M corresponds to a rotation of the magnetic induction vector B of magnetic angle a according to the geometric development of the at least one magnetic bar 6 wound as a helix-shaped spiral.
  • the graph in figure 8a shows the variation of the linear displacement d as a function of the angle of rotation a.
  • the development of the magnetic bar 6 being known, it is possible to obtain the position d of the magnetic slider 90 with respect to the magnetic field sensor 81 from the magnetic angle a.
  • the distance d can be calculated using the following formula: a ⁇ deg]
  • the position is measured without any mechanical contact between the sensing element, the magnetic field sensor 81, and the magnetic slider 9. Being free of mechanical wear, the metrological characteristics of the transducer do not decay over time related to its use. Such decay characterizes other linear widely used transducers, such as those based on resistive track and slider with sliding electrical contacts.
  • the sensing element, the magnetic field sensor 81 and all the electronic subsystems needed for conditioning, processing and presenting the measurement, the logic control unit 21, the power management circuit 22, the output signal conditioning circuit 23 are contained inside the housing of the transducer 24 and in the rod of the transducer 5. Because they do not include moving parts, such casings can be filled with resin, whereby ensuring the highest level of protection of the transducer (IP69) against the intrusion of solid particles, such as parts of the body and dust, and access of liquids.
  • IP69 highest level of protection of the transducer
  • the pitch of the magnetic helix-shaped spiral 6 In order to increase the resolution of the transducer, it is sufficient to change the pitch of the magnetic helix-shaped spiral 6. For example, if the pitch was L/2, during the exploration of the entire full-scale L of the transducer by the magnetic slider 90, the magnetic induction vector B would make two complete rotations about the axis of the transducer M, consequently the magnetic angle a would go from 0° to 720°.
  • the power management circuit 22 includes two auxiliary energy units, a rechargeable one 221, e.g. a super capacitor, and a non-rechargeable one 222, e.g. a battery.
  • the supply management circuit 22 ensures, even in absence of external power supply Vin of the transducer from the input IN of the transducer connector 3, the continuous powering of the magnetic field sensor 81, made for example with a low power consumption device based on magnetoresistive tunnel effect, and of the control logic unit 21, made by a low consumption microcontroller.
  • the preferential auxiliary unit will be the rechargeable one 221 and, only when discharged, the power management circuit 22 will switch via a switch 223 onto the non-rechargeable auxiliary unit 222.
  • the rechargeable unit 221 is recharged when the external power supply of the sensor is available.
  • the logic control unit 21 receives the detection from the sensor 81 and comprises a section 212 adapted to measure the angle of rotation a of the magnetic induction vector B and a revolution counting section 211, which interprets the signal coming from the magnetic field sensor 81 and detects the number of revolutions made by the magnetic induction vector B, saving such count in memory.
  • the signal relating to the components By and Bz of the magnetic induction vector B may be squared by threshold comparators and converted into a quadrature signal AB typical of encoders.
  • the revolution count is obtained by counting the quadrature pulses AB.
  • the memory in which the revolution count value is stored can be volatile (RAM) buffered or non volatile (Flash, FRAM).
  • the control logic unit 21 also comprises a section which interprets the signal coming from the magnetic field sensor 81 and implements the trigonometric formulas given above to calculate the magnetic angle a, by applying specific calibration functions, such as for example linearization of the characteristic curve a, d shown in figures 2-7, to increase the metrological performance of the transducer.
  • Such section controls the output signal conditioning circuit 23 which transmits the measurement performed by the transducer onto the output OUT of the connector 3.
  • the linear position transducer comprises, in addition to the linear position transducer of figures 1-8, a sliding guide 72 for the magnetic slider 9 made on the rod 5 and an anti-rotation dowel 73 to prevent the rotation of the magnetic slider 9 on the rod 5.
  • the linear position transducer comprises a second magnetic field sensor 82 which makes it possible to implement a position measurement redundant inside the transducer, in addition to the linear position transducer of figures 1-8. In this manner, it is possible to use the suggested transducer in applications with high functional safety requirements.
  • the helical development magnet 9 is preferably made using a hollow cylinder of magnetic material, obtained by sintering NdFeB and SmCo or AlNiCo powders or by using the following techniques, for example: injection molding of NdFeB and SmCo or AlNiCo composites bound with plastic materials; compression molding of NdFeB and SmCo or AlNiCo composites bound with plastic materials; the cylinder is appropriately magnetized with helical profile, as shown greater detail in figure 1 la.
  • the linear position transducer according to said another variant comprises the sliding guide 72 for the magnetic slider 90 made on the rod 5 and the anti -rotation dowel 73.
  • Figures 12-14 show various steps of operation of the linear position transducer in figure 10.
  • the second magnetic field sensor 82 has sensing axes x’, y’, z’ of center O’ orthogonal to each other.
  • the principle of operation of the magnetic field sensor 82 can be, for example, Hall effect, giant magnetoresistance, or magnetoresistive tunnel effect.
  • a main electronic board 2 (figure 1 lb), connected to the electronic board 8 via the electrical connection cable 4 which slides inside the rod 5, processes the components x, y, z of the magnetic induction vector B generated by the magnet 9 with reference to the sensor 81 in order to obtain the magnetic angle a and redundantly processes the components x’, y’, z’, of the magnetic induction vector B’ generated by the magnet 9 with reference to the sensor 82 again to derive the magnetic angle a.
  • the magnetic angle a is calculated with vector B’ in the same manner as it is calculated with vector B.
  • the electronic board 2 comprises logic control units 21, 2lb, power management circuits 22 and output signal conditioning circuits 23, 23b for the respective sensors 81, 82; the electronic board 2 is arranged in a housing 24.
  • a connector 3 is present for the electrical connection to an external element.
  • the power management circuits 22, 22b each include two auxiliary energy units, a rechargeable one 221, 22 lb e.g. a super capacitor, and a non- rechargeable one 222, 222b, e.g. a battery.
  • the supply management circuits 22 ensure, even in the absence of external power supply Vin of the transducer from the inputs IN, IN’ of the transducer connector 3, the continuous powering of the magnetic field sensor 81, made for example with a low power consumption device based on magnetoresistive tunnel effect, and of the control logic units 21, 2 lb made with a low consumption microcontroller.
  • the preferential auxiliary unit will be the rechargeable one 221, 22 lb and, only when discharged, the power management circuits 22, 22b will switch via switches 223, 223b onto the non-rechargeable auxiliary unit 222, 222b.
  • the rechargeable unit 221, 22lb is recharged when the external power supply of the sensor is available.
  • the logic control units 21, 2lb receive the detection from the sensors 81, 82 and comprise a section 212, 2l2b adapted to measure the angle of rotation a of the magnetic induction vector B, B’ and a revolution counting section 211, 21 lb, which interprets the signal coming from the magnetic field sensors 81, 82 and detects the number of revolutions performed by the magnetic induction vectors B, B’ saving such count in memory.
  • the signal related to the By and Bz components of the magnetic induction vector B or the signal related to the components By’ and Bz’ of the magnetic induction vector B’ may be squared by threshold comparators and converted into a quadrature signal AB typical of encoders. The revolution is obtained by counting the quadrature pulses AB.
  • the memory in which the revolution count value is stored can be volatile (RAM) buffered or non-volatile (FLASH, FRAM).
  • the control logic units 21, 2 lb further comprise a section which interprets the signal coming from the magnetic field sensors 81, 82 and implement the trigonometric formulas given above to calculate the magnetic angle a, by applying specific calibration functions, such as, for example, linearization of the characteristic curve a, d shown in figures 12-15, to increase the metrological performance of the transducer.
  • Such section controls the output signal conditioning circuit 23, 23b which transmits the measurement performed by the transducer onto the output OUT, OUT’ of the connector 3.
  • the linear position transducer comprises a helical development magnet 9 about an axis M.
  • the magnet 9 preferably comprises at least one magnetic bar 61, polarized along the thickness (S and N), twisted so as to develop a hollow magnetic helix-shaped spiral of length L about the axis of development M of the position transducer 1.
  • Such length L represents the measurement full-scale of the transducer.
  • the magnetic bar 61 is included in a tubular sliding support 74.
  • the magnet 9 can be made using a full cylinder of magnetic material, obtained by sintering NdFeB and SmCo or MNiCo powders by using the following techniques, for example: injection molding of NdFeB and SmCo or AlNiCo composites bound with plastic materials; compression molding of NdFeB and SmCo or AlNiCo composites bound with plastic materials; the element is then appropriately magnetized with helix profile.
  • the contactless linear position transducer of the second embodiment of the present invention comprises a housing 100 hollow in the middle of the ring type; the helical development magnet 9 included in the support 74 can slide in the middle of the housing.
  • the housing 100 is shown divided into two parts, an upper part 101 and lower part 102, which are assembled by means of screws or bolts.
  • the housing 100 and the sliding support 74 for the magnet 9 can be made of paramagnetic material, such as aluminum or stainless steel 316 or plastic.
  • the transducer has an instrumented slider.
  • a ferromagnetic material ring 75 is included inside the housing 100, with the aim of concentrating the magnetic field generated by the magnetic bar 61 inside the housing 100 itself and of protecting the magnetic field sensor 81 from possible external electromagnetic interference.
  • a magnetic field sensor 81 with sensing axes x, y, z of center O and orthogonal to each other is provided; the sensor 81 is arranged along an axis parallel to the axis of development M of the magnet 9 which is also the axis of the linear position transducer.
  • the principle of operation of the magnetic field sensor 81 can be, for example, Hall effect, giant magnetoresistance, or magnetoresistive tunnel effect.
  • the magnetic field sensor 81 resides on the main electronic board 2a inside the housing 100.
  • a second magnetic field sensor 82 is provided, arranged along an axis parallel to the axis of the development M of the magnet 9, which resides on the respective electronic board 2b and which may be accommodated inside the same housing 100 as the transducer to provide a position measurement redundant with the transducer itself.
  • the principle of operation of the magnetic field sensor 82 can be, for example, Hall effect, giant magnetoresistance, or magnetoresistive tunnel effect.
  • the boards 2a and 2b have the same components as the board 2 of the first embodiment of the present invention.
  • the magnetic angle a is calculated by means of the vector measurement of the two magnetic induction vector components B (By, Bz), according to the formula:
  • the linear displacement of the sensor 81 along an axis parallel to axis M corresponds to a rotation of the magnetic induction vector B of magnetic angle a according to the geometric development of the magnetic bar 61.
  • the development of the magnetic bar 6 being known, it is possible to obtain the position d of sensor 81 with respect to the transverse axis N, orthogonal to M and passing through the mean point L/2 of the magnet 9 from the magnetic angle a.
  • the distance d can be calculated using the following formula: a ⁇ deg]
  • the position is measured without any mechanical contact between the sensing element, the magnetic field sensor 81 and the magnet 9. Being free of mechanical wear, the metrological characteristics of the transducer do not decay over time related to its use. Such decay characterizes other linear widely used transducers, such as those based on resistive track and slider with sliding electrical contacts.
  • the sensing element, the magnetic field sensor 81 and all the electronic subsystems needed for conditioning, processing and presenting the measurement, the logic control unit 21, the power management circuit 22, the output signal conditioning circuit 23 are contained inside the housing 100 of the transducer 1. Because they do not include moving parts, such casing may be filled with resin, whereby ensuring the highest level of protection of the transducer (IP69) against the intrusion of solid particles, such as parts of the body and dust, and access of liquids.
  • IP69 highest level of protection of the transducer
  • the pitch of the magnetic helix-shaped spiral 61 In order to increase the resolution of the transducer, it is sufficient to change the pitch of the magnetic helix-shaped spiral 61. For example, if the pitch was L/2, during the exploration of the entire full-scale L of the sensor 81, the magnetic induction vector B would make two complete rotations about the axis of the transducer M, consequently the magnetic angle a should be from 0° to 720°.
  • the main electronic board 2a processes the components x, y, z of the magnetic induction vector B generated by the magnet 9 with reference to the sensor 81 in order to obtain the magnetic angle a, while the board 2b redundantly processes the components x’, y’, z’ of the magnetic induction vector B’ generated by the magnet 9 with reference to the sensor 82 again to derive the magnetic angle a.
  • the magnetic angle a is calculated with vector B’ in the same manner as it is calculated with vector B.
  • the electronic boards 2a, 2b each comprise the components of the board 2 of the transducer of the first embodiment of the invention, i.e. logic control units 21, 2lb, power management circuits 22, 22b and output signal conditioning circuits 23, 23b for the respective sensors 81, 82; the electronic board 2 is arranged in a housing 24.
  • a connector 3 is present for the electrical connection to an external element.
  • the sensing means of the transducer 1 of the linear position comprise a magnetic field sensor 81, already described above.
  • the magnet 9 comprises at least one magnetic bar 6 which, being wound as a spiral, generates a helix adapted to perform more than one revolution along the axis of development M. Therefore, the pitch P of the helix is smaller than the length L of the spiral.
  • the linear position transducer 1 further comprises at least one magnetic switch Dl (or D2) arranged along the axis of development M of the magnet 9.
  • the at least one magnetic switch Dl (or D2) is carried by a hollow rod 5 arranged inside the magnet 9 along the axis of development M of the magnet.
  • the at least one magnetic switch Dl (or D2) is arranged on the electronic board 8 which supports the magnetic field sensor 81.
  • the linear position transducer 1 can comprise a housing 100 hollow in the middle of the ring type; the magnet 9 can slide in the middle of the casing.
  • the at least one magnetic switch Dl can be taken inside the housing 100, in the middle of which the magnet 9 can slide. Again in this case, the at least one magnetic switch Dl (or D2) can be arranged on the electronic board 2 which also supports the magnetic field sensor 81.
  • At least one magnetic switch Dl (or D2) is arranged along the axis of development M of the magnet 9 so that:
  • the distance between the at least one magnetic switch Dl (or D2) with respect to the magnetic field sensor 81 is smaller than P;
  • the at least one magnetic switch Dl (or D2) is supplied by the power management circuit 22 which ensures power continuity by virtue of the two auxiliary energy units, described previously.
  • the at least one magnetic switch Dl (or D2) is adapted to provide an electrical output digital, 0/1, uDl (or uD2) for each sensing axis with which is equipped.
  • Such electrical digital output (0/1) is adapted to switch as a function of the fact that the intensity of the magnetic induction vector component BD1
  • the electrical digital output uDl (or uD2) is connected via the electrical connection cable 4 to the main electronic board 2, in particular to the revolution counting section 211 of the logic control unit 21.
  • the linear displacement of the magnetic slider 90 linearly movable with respect to said sensing means 81, 82, represented by the tubular casing 7 and by the magnet 9, along the axis of development M of the magnet for the whole length L corresponds to a rotation of the magnetic induction vector B which will perform more than one revolution. In particular, it will make L/P revolutions.
  • the electrical digital output uDl (or uD2) of at least one magnetic switch Dl (or D2) can be decoded with the traditional quadrature signals standard, typical of incremental encoders, to count the revolution.
  • the sensing means of the linear position transducer 1 comprise a magnetic field sensor 81, already described previously.
  • the magnet 9 comprises at least one magnetic bar 6 which, being wound as a spiral, generates a helix adapted to perform more than one revolution along the axis of development M. Therefore, the pitch P of the helix is smaller than the length L of the spiral.
  • the linear position transducer 1 comprises at least one first magnetic switch Dl and at last one second magnetic switch D2 arranged along the axis of development M of the magnet 9.
  • the at least one magnetic switch Dl and the at least one second magnetic switch D2 are carried by a hollow rod 5 arranged inside the magnet 9 along the axis of development M of the magnet.
  • the at least one magnetic switch Dl and the at least one second magnetic switch D2 are arranged on the electronic board 8 which supports the magnetic field sensor 81.
  • the at least one first magnetic switch Dl and at least one second magnetic switch D2 are arranged along the axis of development M of the magnet 9 so that:
  • the at least one first magnetic switch Dl and the at least one second magnetic switch D2 have at least one respective sensing axis yDl, yD2 which lies on the plane orthogonal to the axis of development M of the magnet;
  • the distance between the at least one switch Dl and the at least one second electromagnetic switch D2 with respect to the magnetic field sensor 81 is smaller than the pitch P;
  • the distance between the at least one switch Dl and the at least one second electromagnetic switch D2 is smaller than the pitch P, i.e. P/2;
  • the at least one first magnetic switch Dl and the at least one second magnetic switch D2 are aligned with a portion of the magnet 9, transversally to the axis of development M of the magnet 9.
  • the at least one magnetic switch Dl and the at least one magnetic switch D2 are supplied by the power management circuit 22 which ensures power continuity by virtue of the two auxiliary energy units, described previously.
  • the at least one first magnetic switch Dl and at least one second magnetic switch D2 are adapted to provide a first electrical digital output, 0/1, uDl and a second electrical digital output, 0/1, uD2, respectively, for each sensing axis with which they are equipped.
  • the first electrical digital output uDl and the second digital output uD2 are adapted to switch as a function of the fact that the intensity of the respective magnetic induction vector component BD1 and BD2, along the respective sensing axis, exceeds a respective threshold of operation of the at least one first magnetic switch Dl and of the at least one second magnetic switch D2.
  • the first electrical digital output uDl and the second electrical digital output uD2 are connected via the electrical connection cable 4 to the main electronic board 2, in particular to the revolution counting section 211 of the logic control unit 21.
  • the linear displacement of the magnetic slider 90 linearly movable with respect to said sensing means 81, 82, represented by the tubular casing 7 and by the magnet 9, along the axis of development M of the magnet for the whole length L corresponds to a rotation of the magnetic induction vector B which will perform more than one revolution. In particular, it will make L/P revolutions.
  • the first electrical digital output uDl of at least one first magnetic switch Dl and the second electrical digital output uD2 of at least one second magnetic switch D2 can be decoded with the traditional quadrature signals standard, typical of incremental encoders, to count the revolution.
  • the first magnetic switch Dl and the second magnetic switch D2 have only one respective sensing axis, indicated respectively by yDl and yD2.
  • first magnetic switch Dl and the second magnetic switch D2 are not configured to measure the angle of rotation a of the magnetic induction vector B, but only its intensity, in the component along the sensing axes.
  • figure 25 indeed shows the magnetic induction vector component B measured by the first magnetic switch Dl along the respective sensing axis yDl indicated by reference BD1 and the magnetic induction vector component B measured by the second magnetic switch D2 along the respective sensing axis yD2 is indicated by reference BD2.
  • first magnetic switch Dl and the second magnetic switch D2 are very common electronic devices used as limit stops or mechanical component passage counters.
  • the first magnetic switch Dl and the second magnetic switch D2 are totally different electronic devices from the magnetic field sensor
  • the at least one magnetic bar 6 is wound as a spiral developing a helix which makes about 4 revolutions.
  • the first magnetic switch Dl generates a first signal uDl (on the first electrical output uDl) and the second magnetic switch D2 is adapted to generate a second signal uD2.
  • a single revolution of the magnetic induction vector B is divided into four sectors, which can be represented with logic states of the first signal uDl and of the second signal uD2, as shown in the table of figure 26.
  • the sensing means of the transducer 1 of the linear position comprise a magnetic field sensor 81, already described previously.
  • the magnet 9 comprises at least one magnetic bar 6 which, being wound as a spiral, generates a helix adapted to perform more than one revolution along the axis of development M.
  • the pitch P of the helix is smaller than the length L of the spiral.
  • the linear position transducer 1 further comprises a plurality of magnetic switches D arranged along the axis of development M of the magnet 9.
  • the plurality of magnetic switches D is carried by a hollow rod 5 arranged inside the magnet 9 along the axis of development M of the magnet 9.
  • the plurality of magnetic switches D is arranged on the electronic board 8 which supports the magnetic field sensor 81.
  • the linear position transducer 1 can comprise a housing 100 hollow in the middle of the ring type; the magnet 9 can slide in the middle of the housing.
  • the plurality of magnetic switches D can be brought inside the housing 100, in the middle of which the magnet 9 can slide. Also in this case, the plurality of magnetic switches D can be arranged on the electronic board 2 which also supports the magnetic field sensor 81.
  • each magnetic switch of the plurality of magnetic switches D has at least two sensing axes orthogonal to each other (indicated by references xDl- xD8, yDl-yD8 in the figures, respectively) which lie on the plane orthogonal to the axis of development M.
  • At least two magnetic switches of the plurality of magnetic switches D are arranged for each portion of length P of the length L of the spiral.
  • the plurality of magnetic switches D is arranged along the axis of development M of the magnet 9 so that the magnetic switches are preferably distributed evenly within of each portion of the length P of the length L of the spiral.
  • Each magnetic switch of the plurality of magnetic switches D is adapted to detect the presence of the magnetic field in the respective surrounding, in this case the presence of the magnetic slider 90 linearly movable with respect to said sensing means 81, 82, represented by the tubular casing 7 and by the magnet 9.
  • each magnetic switch of the plurality of magnetic switches D is equipped with at least two sensing axes (as mentioned above) and is adapted to provide a respective electrical digital output, 0/1, uDl-UD8 for each sensing axis with which they are equipped.
  • Such electrical output is adapted to switch as a function of the fact that the intensity of the magnetic induction vector component B along the respective sensing axis exceeds a respective threshold of operation of the magnetic switch or not. [000197].
  • the at least two electrical digital outputs of each magnetic switch of the plurality of magnetic switches D are connected by means of the electrical connection cable 4 to the main electronic board 2, in particular to the logic control unit 21.
  • the logic control unit 21 is adapted to perform an OR logic operation of the outputs of each magnetic switch of the plurality of magnetic switches D.
  • the sensing means of the linear position transducer comprise a magnetic field sensor 81, already described previously.
  • the magnet 9 comprises at least one magnetic bar 6 which, being wound as a spiral, generates a helix adapted to perform more than one revolution along the axis of development M.
  • the pitch P of the helix is smaller than the length L of the spiral.
  • the linear position transducer 1 further comprises a plurality of magnetic switches D arranged along the axis of development M of the magnet 9.
  • the plurality of magnetic switches D is carried by a hollow rod 5 arranged inside the magnet 9 along the axis of development M of the magnet.
  • the plurality of electromagnetic switches D is arranged on the electronic board 8 which supports the magnetic field sensor 81.
  • the plurality of magnetic switches D is arranged along the axis of development M of the magnet 9 so that:
  • each magnetic switch of the plurality of magnetic switches D has at least one sensing axis (indicated in the figures by references yDl-yD8) which lies on the plane orthogonal to the axis of development M;
  • four magnetic switches of the plurality of magnetic switches D are distributed for each portion of length equal to the pitch P of the length L of the spiral, uniformly distributed within each portion of length P of the length L of the spiral with a distance equal to one quarter of the pitch P (P/4) from one another.
  • Each magnetic switch of the plurality of magnetic switches D is adapted to detect the presence of the magnetic field in the respective surrounding, in this case the presence of the magnetic slider 90 linearly movable with respect to said sensing means 81, 82, represented by the tubular casing 7 and by the magnet 9.
  • each magnetic switch of the plurality of magnetic switches D is equipped with at least one sensing axis (as mentioned above) and is adapted to provide a respective electrical digital output, 0/1, uDl-UD8 for each sensing axis with which they are equipped.
  • Such electrical digital output is adapted to switch as a function of the fact that the intensity of the magnetic induction vector component B along the respective sensing axis exceeds a respective threshold of operation of the magnetic switch or not.
  • the logic control unit 21 is adapted to perform an OR logic operation of the electrical digital outputs of each magnetic switch of the plurality of magnetic switches D.
  • the plurality of magnetic switches D comprises eight magnetic switches, D1-D8, each with two sensing axes, yDl-yD8 and zDl-zD8, respectively.
  • each axis zDl-zD8 is orthogonal to the plane of the drawing section and so for the sake of clarity of the figure is not shown.
  • the magnetic switches of the plurality of magnetic switches are not configured to measure the angle of rotation a of the magnetic induction vector B, but only its intensity, in the component along the sensing axes.
  • the at least one magnetic bar 6 is wound as a spiral developing a helix which performs about four revolutions.
  • a magnetic switch the first from left, indicated by D8, does not detect the presence of magnetic slider 90 (table in figure 28b) and the magnetic field sensor 81 works in the first half of the first revolution (from 0° to 180°), as shown in figure 29.
  • the linear position transducer 1 being able to determine the revolution number of the spiral in which the magnetic field sensor 81 is working, is advantageously able to provide a reliable measurement without the aid of the battery which would be needed to keep the linear position transducer 1 on to prevent losing the count of the numbers of revolutions.
  • the sensing means of the linear position transducer 1 comprise a magnetic field sensor 81, already described above.
  • the magnetic field sensor 81 is configured to measure the two vector components Bz, By of the magnetic induction vector B and to calculate the magnetic field intensity
  • the magnet 9 comprises at least one magnetic bar 6 which is wound as a spiral, whereby generating a helix which performs more than one revolution, so the pitch P of the helix is less than the length L of the spiral.
  • the intensity of the magnetic induction vector B is not homogeneous, i.e. is not constant, for the entire length L of the spiral.
  • the non-homogeneity of the intensity value of magnetic field of the magnetic induction vector B is obtained by composing the magnet 9 with various magnetic bars 6, each with different remanence properties, obtained either by different magnetic material composition or by a different magnetization field intensity.
  • each portion of length P of the length L of the spiral comprises at least two magnetic bars 6 with different remanence value.
  • the at least magnetic bars 6 are arranged to compose the magnet 9 with ascending or descending remanence.
  • the at least two magnetic bars 6 wound as a spiral develop a helix which makes about 4 revolutions.
  • the magnetic slider 90 linearly movable with respect to said sensing means 81, 82, represented by the tubular casing 7 and from the magnet 9 comprise, for example, nine segments of magnetic bar with different remanence values, indicated in the figures by references 11-19.
  • of the magnetic induction vector B generated by the magnet 9 varies according to a step pattern (figure 31), so as to facilitate discriminating the measurement of the position d of the magnetic slider 90 by means of the measurement of the intensity value of magnetic field
  • of the magnetic induction vector B in a first segment il is lower than the value of the magnetic field intensity
  • the magnetic field sensor 81 is working in the second half of the first revolution (the angle of rotation a varies from 0° to 180°) and the intensity value of magnetic field
  • the magnetic field sensor 81 is working in the first half of the second revolution (the angle of rotation a varies from -180° to 0°) and the intensity value of magnetic field
  • the magnetic field sensor 81 is working in the second half of the second revolution (the angle of rotation a varies from 0° to 180°) and the intensity value of magnetic field
  • the linear position transducer 1 being able to determine the revolution number of the spiral in which the magnetic field sensor 81 is working, is advantageously able to provide a reliable measurement without the aid of the battery which would be needed to keep the linear position transducer 1 on to prevent losing the count of the numbers of revolutions.
  • the sensing means of the linear position transducer 1 comprise a magnetic field sensor 81, already described above.
  • the magnetic field sensor 81 is configured to calculate, from the measure the two vector components By, Bz of the magnetic induction vector B and to calculate the magnetic field intensity
  • the magnet 9 comprises at least one magnetic bar 6 which is wound as a spiral, whereby generating a helix which performs more than one revolution, so the pitch P of the helix is less than the length L of the spiral.
  • the intensity of the magnetic induction vector B is not homogeneous, is not constant, for the entire length L of the spiral.
  • the non-homogeneity of the value of the magnetic field intensity of the magnetic induction vector B is obtained by varying the rolling radius of at least one magnetic bar 6.
  • the rolling radius is made to vary continuously with respect to the length L of the spiral, so as to generate a monotonous variation of the intensity value of magnetic field
  • the at least two magnetic bars 6 wound as a spiral develop a helix which makes about 4 revolutions.
  • the rolling radius of the two magnetic bars 6 varies along the length L of the spiral.
  • of the magnetic induction vector B generated by the magnet 9 is maximum
  • with the magnetic slider 90 all inside (D 0), while it is minimum
  • varies continuously and monotonously along the length L of the spiral from a maximum value
  • the magnetic field sensor 81 is working in the first half of the first revolution, so the angle of rotation a varies from -180° to 0° and the intensity value of magnetic field
  • the magnetic field sensor 81 is working in the second half of the first revolution, so the angle of rotation a varies from 0° to 180°, as shown in figure 33. [000278].
  • the magnetic slider 90 has been extracted to measure a distance d substantially equal to P.
  • the magnetic field sensor 81 is working in the first half of the second revolution (the angle of rotation a varies from -180° to 0°), as shown in figure 33.
  • the magnetic field sensor 81 is working in the first half of the fourth revolution (the angle of rotation a varies from -180° to 0°) and the intensity value of magnetic field
  • the linear position transducer 1 being able to determine the revolution number of the spiral in which the magnetic field sensor 81 is working, is advantageously able to provide a reliable measurement without the aid of the battery which would be needed to keep the linear position transducer on to prevent losing the count of the numbers of revolutions.
  • the sensing means of the linear position transducer 1 comprise a magnetic field sensor 81, already described above.
  • the magnetic field sensor 81 is configured to calculate, from the measure the two vector components By, Bz of the magnetic induction vector B and to calculate the magnetic field intensity
  • the magnet 9 comprises at least one magnetic bar 6 which is wound as a spiral, whereby generating a helix which performs more than one turn, so the pitch of the helix P is less than the L.
  • the intensity of the magnetic induction vector B is not homogeneous, i.e. is not constant, for its entire length L of the spiral. [000288].
  • the non-homogeneity of the value of the magnetic field intensity of the magnetic induction vector B is obtained by varying the thickness of the tubular casing 7.
  • the air gap can be varied by acting on the thickness of the tubular casing 7.
  • the air gap is made to vary continuously with respect to the length L of the spiral, so as to generate a monotonous variation of the intensity value of magnetic field
  • the at least two magnetic bars 6 wound as a spiral develop a helix which makes about 4 revolutions.
  • the air gap between the two magnetic bars 6 and the tubular casing 7 varies for the length L of the spiral.
  • the intensity value of the magnetic induction vector B generated by the magnet 9 is minimum
  • with the magnetic slider 90 all inside (d 0), while it is maximum
  • the magnetic field sensor 81 is working in the first half of the first revolution, so the angle of rotation a varies from -180° to 0° and the intensity value of magnetic field
  • the magnetic field sensor 81 is working in the second half of the first revolution, so the angle of rotation a varies from 0° to 180°, as shown in figure 35.
  • the magnetic field sensor 81 is working in the first half of the second revolution (the angle of rotation a varies from -180° to 0°), as shown in figure 35.
  • the linear position transducer 1 being able to determine the revolution number of the spiral in which the magnetic field sensor 81 is working, is advantageously able to provide a reliable measurement without the aid of the battery which would be needed to keep the linear position transducer 1 on to prevent losing the count of the numbers of revolutions.
  • the sensing means of the linear position transducer 1 comprise a magnetic field sensor 81, already described above.
  • the magnetic field sensor 81 is configured to calculate, from the measure of the two vector components By, Bz of the magnetic induction vector B, the intensity value of magnetic field
  • the magnet 9 comprises at least one magnetic bar 6 which is wound as a spiral, whereby generating a helix which performs more than one turn, so the pitch of the helix P is less than the L.
  • the intensity of the magnetic induction vector B is not homogeneous, i.e. is not constant, for its entire length L of the spiral.
  • the non-homogeneity of the intensity value of magnetic field is obtained by composing the magnet 9 with one or more magnetic bars 6 configured to obtain an overall combination with different thickness.
  • the magnet 9 can be composed of several magnetic bars 6, each with different thickness.
  • the different thickness can be obtained by combining multiple sections of the same magnetic bar 6 with the same thickness, superimposing the sections on the other.
  • the same magnetic bar 6 may have non-uniform thickness along its length.
  • Each portion of the length P of the length L of the spiral comprises at least two magnetic bars 6. [000318].
  • the magnetic bars 6 are arranged to compose the magnet 9 with increasing or descending thickness.
  • a plurality of magnetic bars 6 wound as a spiral develop a helix which performs about 4 revolutions.
  • the tubular casing 7 and the magnet 9 represent a magnetic slider 90 linearly movable with respect to said sensing means 81, 82.
  • the magnetic slider 90 comprises nine segments of magnetic bar with different thicknesses, indicated in the figures by references sl-s9.
  • the intensity value of magnetic field B of the magnetic induction vector B generated by the magnet 9 varies according to a step pattern
  • of the magnetic induction vector B in a first segment sl is higher than the intensity value of magnetic field
  • the magnetic field sensor 81 is working in the second half of the first revolution (the angle of rotation a varies from 0° to 180°) and the intensity value of magnetic field
  • the magnetic field sensor 81 is working in the first half of the second revolution (the angle of rotation a varies from -180° to 0°) and the intensity value of magnetic field
  • the magnetic field sensor 81 is working in the second half of the second revolution (the angle of rotation a varies from 0° to 180°) and the intensity value of magnetic field
  • the linear position transducer 1 being able to determine the revolution number of the spiral in which the magnetic field sensor 81 is working, is advantageously able to provide a reliable measurement without the aid of the battery which would be needed to keep the linear position transducer 1 on to prevent losing the count of the numbers of revolutions.
  • the linear position transducer 1 comprises a first magnet 9 arranged inside a magnetic slider 90 linearly movable with respect to said sensing means 81, 82, represented by the tubular casing 7 and by the first magnet 9, comprising at least one first magnetic bar 6 which is wound as a spiral, generating a helix which performs more than one revolution. [000337]. Therefore, the pitch P of the helix defined by at least one first magnetic bar 6 is smaller than the length L of the spiral.
  • portions L/P of length equal to the pitch P of the helix on the length L of the spiral, which coincide with the revolutions performed by the helix, are identifiable on the first magnet 9.
  • the linear position transducer 1 further comprises a second magnet 9’ arranged outside the magnetic slider 90, comprising at least one second magnetic bar 6’ which is wound as a spiral, generating a helix which performs one revolution at most.
  • the pitch P of the helix defined by at least one second magnetic bar 9’ is higher than the length L of the spiral.
  • first magnet 9 and the second magnet 9’ are mutually separated by the tubular casing 7 made of ferromagnetic material.
  • the sensing means of the linear position transducer 1 comprise a first magnetic field sensor 81 arranged inside the magnetic slider 90.
  • the first magnetic field sensor 81 is arranged along the axis of development M of the first magnet 9 so that, during the linear movement along the axis of development M, transversally to the axis of development M, it is aligned with a portion of the first magnet 9.
  • the first magnetic field sensor 81 is configured to detect a first angle of rotation a of the magnetic induction vector B generated by the first magnet 9.
  • the linear position transducer 1 further comprises a second magnetic field sensor 82 arranged outside the magnetic slider 90.
  • the second magnetic field sensor 82 is arranged along the axis of development M of the first magnet 9 so that, during the linear movement along the axis of development (M), transversally to the axis of development (M), it is aligned with a portion of the second magnet 9.
  • the second magnetic field sensor 82 is configured to detect a second angle of rotation a’ of the magnetic induction vector B generated by the second magnet 9.
  • a measurement of the first angle of rotation a is non-univocally related to the distance d because the helix of the second magnet 9 performs more than one revolution.
  • a second magnetic bar 9’ wound as a spiral to develop a helix which performs just less than one revolution, is arranged outside the magnetic slider 90.
  • the first magnetic bar 6 and the second magnetic bar 6’ are separated by the tubular casing 7 made of ferromagnetic material.
  • the linear position transducer 1 further comprises a second tubular casing 75 made of ferromagnetic material adapted to envelop the second magnetic field sensor 82 placed outside the magnetic slider 90. [000357].
  • the first magnetic field sensor 81 measures a first angle of rotation a of the magnetic induction vector B present in the first revolution of the helix of the first magnet 9, while the second magnetic field sensor 82 univocally identifies the position of the magnetic slider 90 by measuring a second angle of rotation a’ of the magnetic induction vector B present in the second magnet 9’ (also see figure 39).
  • the first magnetic field sensor 81 measures the first angle of rotation a of the magnetic induction vector B present in the second revolution of the helix of the first magnet 9, while the second magnetic field sensor 82 univocally identifies the position of the magnetic slider 90 by measuring the second angle of rotation a’ of the magnetic induction vector B present in the second magnet 9’ (also see figure 39).
  • the first magnetic field sensor 81 measures the first angle of rotation a of the magnetic induction vector B present in the third revolution of the helix of the first magnet 9, while the second magnetic field sensor 82 univocally identifies the position of the magnetic slider 90 by measuring the second angle of rotation a’ of the magnetic induction vector present in the second magnet 9’ (also see figure 39).
  • the first magnetic field sensor 81 measures the first angle of rotation a of the magnetic induction vector B present in the fourth revolution of the helix of the first magnet 9, while the second magnetic field sensor 82 univocally identifies the position of the magnetic slider 90 by measuring the second angle of rotation a’ of the magnetic induction vector B present in the second magnet 9’ (also see figure 39).
  • the linear position transducer 1 being able to determine the revolution number of the spiral in which the magnetic field sensor 81 is working, is advantageously able to provide a reliable measurement without the aid of the battery which would be needed to keep the linear position transducer 1 on to prevent losing the count of the numbers of revolutions.
  • the magnet 9 comprises at least one magnetic bar 6 made of flexible magnetic material, e.g. magnetic rubber having a set flexibility or rigidity, e.g. in the order of 30-80 Shore D.
  • the rod 5 which supports the sensing means 81 may be made of a flexible material, having for example a flexibility or rigidity equal to 50 Shore D.
  • the rod 5 can be made by means of a flexible tube made of steel for fittings or by means of a steel cable for flexible transmissions.
  • the sensing means 81 are housed in a free end 5’ of said rod 5.
  • the rounded end 5’ can slide freely inside the magnetic slider 90 linearly movable with respect to said sensing means 81, 82, represented by the tubular casing 7 and by the magnet 9, adapting to follow any bending of the magnetic slider 90.
  • the linear position transducer 1 is advantageously capable of measuring the position of the sensing means 81 (e.g. of the magnetic field sensor 81) with respect to the magnetic slider 90 as if it were following a path which develops in three dimensions.
  • the hollow rod 5 is adapted to slide within a sliding bearing 71.
  • the rod 5 has a square cross section and the sliding bearing 71 is square and integral with respect to the magnetic slider 90, when the rod 5 is moved from the outside to explore the magnetic slider 90, the magnetic bearing 71 allows the rod 5 to move linearly and follow the curves of the magnetic slider 90, whereby preventing instead a relative rotation between the rod 5 which carries the sensing means 81 (magnetic field sensor 81) and the magnet 9.
  • the linear position transducer 1 actually comprises a flexible magnetic slider which allows its use in the cases in which it is necessary to follow curved profiles in which evidently a linear position transducer 1 with a rectilinear longitudinal development would not be applicable.
  • the magnetic slider 90 is linearly movable with respect to said sensing means 81, 82, represented by the tubular casing 7 and by the first magnet 9, comprises a lateral groove 83 parallel to the axis of development M of the magnet in which it is possible to house the sensing means 81 and make them slide along the axis of development M inside the magnetic slider 90.
  • the linear position transducer 1 comprises an electronic board 8, on which the sensing means 81 are mounted, which, after inserting the sensing means 81 inside the magnetic slider 90, has a portion on the outside of the lateral groove 83 to which an electrical connection cable 4 is connected.
  • the magnetic slider 90 comprises a first free end 92 and a second free end 93.
  • the magnetic slider 90 is configured to be rolled up to join the first free end 92 and the second free end 93.
  • the sensing means 81 can slide inside the magnetic slider 90 without discontinuity or mechanical jamming.
  • the linear position transducer 1 lends itself to measuring the angular position of large size rotating parts the rotation fulcrum of which is not easily accessed to install a conventional rotary sensor.
  • the wiring and the electronic processing of information of the linear position transducer 1 are operatively connected to the fixed part of the linear position transducer 1, e.g. a base, which can be fixed to an element with respect to which the position related to a slider it is desired to detect.
  • the magnetic slider 90 linearly movable with respect to said sensing means 81, 82, represented by the tubular casing 7 and by the first magnet 9 is fixed, while the sensing means 81 (magnetic field sensor 81), mounted on an electronic board 8, are included in a movable slider assembly 200 with respect to the linear position to be measured.
  • the magnetic slider 90 comprises a lateral recess 110 which allows the sliding of the movable slider assembly 200 on which the sensing means 81 are housed.
  • the magnetic slider 90 is free from recesses and the sensing means 81 (magnetic field sensor 81) are included in the movable slider assembly 200 adapted to slide outside the magnetic slider along the axis of development M of the magnet.
  • the linear position transducer 1 may comprise more than one movable slider assembly 200 adapted to slide with respect to the magnetic slider 90 itself.
  • the magnetic slider 90 comprises a first wireless data communication and power supply module 120, e.g. an antenna or a winding or any other equivalent means, arranged along the entire length of the magnetic slider 90.
  • a first wireless data communication and power supply module 120 e.g. an antenna or a winding or any other equivalent means, arranged along the entire length of the magnetic slider 90.
  • the first wireless data communication and power supply module 120 is connected via an electrical connection cable 4 to the main electronic board 2.
  • the magnetic slider 90 further comprises a housing 24 of the main electronic board 2.
  • the movable slider assembly 200 comprises a second wireless data communication and power supply module 130, e.g. an antenna or a winding or any other equivalent means, mounted on the electronic board 8.
  • a second wireless data communication and power supply module 130 e.g. an antenna or a winding or any other equivalent means, mounted on the electronic board 8.
  • the first wireless data communication and power supply module 120 being adapted to transmit the electric energy for operating the sensing means 81 (magnetic field sensor 81) to the second wireless data communication and power supply module 130.
  • the 130 is adapted to collect to the electrical energy transmitted by the first wireless data communication and power supply module 120 and to allow the data communication between the sensing means 81 and the main electronic board 2.
  • the first wireless data communication and power supply module 120 (primary element) and the second wireless data communication and power supply module 130 (secondary element) make a wireless connection previously obtainable by using a physical wiring (connection cable 4).
  • the linear position transducer 1 comprises a hollow magnetic slider 90 linearly movable with respect to said sensing means 81, 82, comprising:
  • a first inner magnet 9, comprising at least one first magnetic bar 6 which is wound in a spiral as a helix along the axis of development M;
  • a second outer magnet 9’ comprising at least one second rectilinear magnetic bar 6’ arranged parallel to the axis of development M;
  • tubular casing 7 made of ferromagnetic material interposed between the first magnet 9 and the second magnet 9’ so as to mutually separate the first magnet 9 and the second magnet 9’ .
  • the sensing means 81, 82 comprise a first magnetic field sensor 81 arranged inside the first magnetic slider 90 so that, during the linear movement along the axis of development M, transversally to the axis of development M, it is aligned with a portion of the first magnet 9.
  • the first magnetic field sensor 81 is configured to detect a first angle of rotation a of the magnetic induction vector B generated by the at least one first magnetic bar 6
  • the sensing means 81, 82 comprise a second magnetic field sensor 82 arranged outside the magnetic slider 90 so that, during the linear movement along the axis of development M, transversally to the axis of development M, it is aligned with a portion of the second magnet 9’.
  • the second magnetic field sensor 82 is configured to detect a second angle of rotation a’ of the magnetic induction vector B generated by the at least one second magnetic bar 6’.
  • the first magnetic field sensor 81 and the second magnetic field sensor 82 are electrically connected to a main electronic board configured to apply noise cancellation algorithms related to the rotation of the magnetic slider 90 about the axis of development M to the detected values.
  • the second angle of rotation a’ is univocally related to the first angle of rotation a about the axis of development M because the at least one second magnetic bar 6’ is arranged in rectilinear manner parallel to the axis of development M and is not wound in a helix. In this manner, the measurement of the second angle of rotation a’ about the axis of development M of the magnetic slider 90 is independent from the position d of the magnetic slider 90.
  • the first angle of rotation a is instead related both to position d of the magnetic slider 90 and to the second angle of rotation a’ because the at least one first magnetic bar 6 is wound as a helix.
  • the signal related to the second angle of rotation a’ can be, in turn, output from the linear position transducer 1 as a further process variable useful for the user.
  • This embodiment advantageously makes it possible to compensate for the possible radial clearance which may arise when the magnetic slider 90 slides on the hollow rod 5 which carries the sensing means 81, 82.
  • the presence of a guide 72 has indeed been defined for the sliding of the magnetic slider 90 made on the rod 5 and the presence of an anti-rotation dowel 73 to prevent the rotation of the magnetic slider 90 on the rod 5.
  • linear position transducer 1 of the linear position may need to be installed in conditions which do not allow the use of the aforementioned anti-rotation elements and that the rotation of the magnetic slider 90 with respect to the rod 5 is provided and necessary, instead.
  • the sensing means 81 in the preferred embodiments described heretofore cannot discriminate the rotation of the magnetic slider 90 about the axis of development M with respect to its linear translation, because both movements cause a variation of the angle of rotation a of the magnetic induction vector B.
  • Figure 45 shows an example of geometry of the magnetic slider 90 at rest.
  • At least one first magnetic bar 6 and at least one second magnetic bar 6’ is present, in which the at least one first magnetic bar 6 is wound as a helix inside the magnetic slider 90, while the at least one second magnetic bar 6 is rectilinear and parallel to the axis of development M, outside the magnetic slider.
  • the at least one first magnetic bar 6 and at least one second magnetic bar 6’ are separated from the tubular casing 7 made of ferromagnetic material.
  • the sensing means 81, 82 are configured to measure a first angle of rotation a and a second angle of rotation a’, respectively.
  • first angle of rotation a varies as a function of the new reached linear position, while the second angle of rotation a’ did not vary because the magnetic slider 90 was not subject to any rotation about the axis of development M.
  • the contactless linear position transducer according to the invention can be used as a position sensor in hydraulic or pneumatic cylinders, as a position sensor for suspension or steering systems, as a position sensor for computerized numerical control machines or as a level sensor (fuel, e.g. LPG/methane, gas, oxygen etc.).
  • a level sensor fuel, e.g. LPG/methane, gas, oxygen etc.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)

Abstract

La présente invention concerne un transducteur de position linéaire (1) qui comprend : un aimant (9, 6, 61) ayant un développement hélicoïdal autour d'un axe de développement respectif (M), des moyens de détection (81, 82) qui ne sont pas en contact avec ledit aimant (9, 6, 61) couplés magnétiquement audit aimant (9, 6, 61), des moyens (2, 2a, 2b) raccordés électriquement auxdits moyens de détection (81, 82) et configurés de sorte à sortir (OUT, OUT') ladite position linéaire (d), ledit aimant (9, 6, 91) et/ou lesdits moyens de détection (81, 82) étant configurés de sorte à se déplacer linéairement le long de l'axe de développement (M) et à être fixés à un élément dont la position doit être détectée, lesdits moyens de détection (81, 82) étant conçus pour mesurer l'angle de rotation (a) du vecteur d'induction magnétique (B, B') produit par ledit aimant (9, 6, 91) et, en raison du déplacement linéaire réciproque (d) entre lesdits moyens de détection (81, 82) et ledit aimant de développement hélicoïdal (9, 6, 61), lesdits moyens étant configurés de sorte à sortir ladite position linéaire (d) à la suite de ladite mesure, un boîtier tubulaire (7, 75) composé d'un matériau ferromagnétique, coaxial audit aimant (9, 6, 91) et configuré de sorte à concentrer le champ magnétique sur lesdits moyens de détection (81, 82), pendant le mouvement linéaire le long de l'axe de développement (M), les moyens de détection (81, 82), transversalement à l'axe de développement (M), étant alignés sur une partie de l'aimant de développement hélicoïdal (9, 6, 61) et sur une partie du boîtier tubulaire (7, 75) composé d'un matériau ferromagnétique.
PCT/IB2018/060645 2017-12-27 2018-12-27 Transducteur de position linéaire sans contact WO2019130233A1 (fr)

Priority Applications (1)

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DE212018000387.4U DE212018000387U1 (de) 2017-12-27 2018-12-27 Kontaktloser linearer Wegaufnehmer

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IT102017000149962 2017-12-27
IT201700149962 2017-12-27

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WO2019130233A1 true WO2019130233A1 (fr) 2019-07-04

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SE2150788A1 (en) * 2021-06-18 2022-12-19 Regal Components Ab Linear position transducer
US20230311345A1 (en) * 2020-09-17 2023-10-05 Fanuc Corporation Balancer and robot system

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Publication number Priority date Publication date Assignee Title
DE102023132999A1 (de) 2023-11-27 2024-07-11 Schaeffler Technologies AG & Co. KG Sensoranordnung

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EP0979988A1 (fr) * 1998-08-13 2000-02-16 FESTO AG & Co Procédé de mesure des mouvements linéaires entre des aimants et des capteurs
US20020125884A1 (en) * 2001-02-23 2002-09-12 Matthias Wendt Device with a magnetic position sensor
US20040217757A1 (en) * 2000-09-29 2004-11-04 Tromblee Gerald A. Linear position sensor
US20130113469A1 (en) * 2010-04-30 2013-05-09 Continental Automotive Gmbh Magnetic length measuring system, length measuring method and method for producing a magnetic length measuring system
US20150247903A1 (en) * 2014-03-03 2015-09-03 Northrop Grumman Systems Corporation Linear positioning system utilizing helically polarized magnet

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EP0979988A1 (fr) * 1998-08-13 2000-02-16 FESTO AG & Co Procédé de mesure des mouvements linéaires entre des aimants et des capteurs
US20040217757A1 (en) * 2000-09-29 2004-11-04 Tromblee Gerald A. Linear position sensor
US20020125884A1 (en) * 2001-02-23 2002-09-12 Matthias Wendt Device with a magnetic position sensor
US20130113469A1 (en) * 2010-04-30 2013-05-09 Continental Automotive Gmbh Magnetic length measuring system, length measuring method and method for producing a magnetic length measuring system
US20150247903A1 (en) * 2014-03-03 2015-09-03 Northrop Grumman Systems Corporation Linear positioning system utilizing helically polarized magnet

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20230311345A1 (en) * 2020-09-17 2023-10-05 Fanuc Corporation Balancer and robot system
SE2150788A1 (en) * 2021-06-18 2022-12-19 Regal Components Ab Linear position transducer
WO2022265554A1 (fr) * 2021-06-18 2022-12-22 Regal Components Ab Capteur de position linéaire
SE545731C2 (en) * 2021-06-18 2023-12-27 Regal Components Ab Linear position transducer configured to provide signals representing at least two components, transverse to each other of a magnetic field

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