WO2011057727A1 - Procédé et unité de détection de position - Google Patents

Procédé et unité de détection de position Download PDF

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Publication number
WO2011057727A1
WO2011057727A1 PCT/EP2010/006652 EP2010006652W WO2011057727A1 WO 2011057727 A1 WO2011057727 A1 WO 2011057727A1 EP 2010006652 W EP2010006652 W EP 2010006652W WO 2011057727 A1 WO2011057727 A1 WO 2011057727A1
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WO
WIPO (PCT)
Prior art keywords
encoder
magnetic
rings
magnetic encoder
ring
Prior art date
Application number
PCT/EP2010/006652
Other languages
English (en)
Inventor
Jan Jansen Doornenbal
Original Assignee
Ab Skf
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 Ab Skf filed Critical Ab Skf
Publication of WO2011057727A1 publication Critical patent/WO2011057727A1/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
    • G01D5/244—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains
    • G01D5/24471—Error correction
    • G01D5/24485—Error correction using other sensors

Definitions

  • the invention concerns position encoders and is more particularly directed to rotary position encoders, especially for electrical motors, such as brushless DC motors.
  • a brushed DC motor conventionally comprises a rotor and a stator.
  • the stator comprises a plurality of magnets, such as permanent magnets.
  • the rotor comprises armature coil windings.
  • brushes make a mechanical contact with a commutator to make an electrical connection between the armature coil windings of the rotor and a DC electrical source.
  • the stationary brushes come into contact with different sections of the rotating commutator.
  • the different sections of the commutator are coupled to an armature coil winding in such a way that a current is switched to always flows through the armature coil winding closest to the stationary stator magnets.
  • the magnets and the armature coil windings have switched places.
  • the rotor comprises a plurality of magnets, preferably permanent magnets
  • the stator comprises the armature coil windings.
  • Brushless DC motors most commonly use an electronic controller instead of the brush commutator system.
  • Brushless DC motors offer several advantages over brushed DC motors, including higher efficiency and reliability, reduced noise, longer service life due to elimination of brush erosion. Additionally ionizing sparks from the commutator are eliminated and there is an overall reduction of electromagnetic interference. Since the windings are part of the stator instead of the rotor, they are not subjected to centrifugal forces. Additionally since the windings are located around the perimeter, they can be cooled by conduction to the motor casing requiring no airflow inside the casing for cooling. This in turn means that the motor can be entirely enclosed and protected from dirt or other foreign matter.
  • An object of the invention is to define a method and a unit of electronically aligning magnetic encoder rings with each other.
  • a further object of the invention is to define a unit and a method of reducing manufacturing costs of rotary position encoders comprising two or more magnetic encoder rings.
  • a unit and a method that determines and electronically compensating for a physical misalignment between two or more magnet encoder rings.
  • the magnetic encoder rings having a known magnetic relationship when physically aligned.
  • the sensor output of each magnet encoder ring is measured.
  • the measurements are then related to expected values in relation to one or more predetermined angular positions.
  • the outcome determines if one or both of the sensor outputs needs to receive an offset to thereby with the offset function as if the magnet encoder rings were physically aligned.
  • a magnetic encoder ring misalignment correction unit arranged to correct a physical misalignment between two magnetic encoder rings of a rotary position encoder comprising at least two magnetic encoder rings.
  • Each magnetic encoder ring comprises multiple magnetic pole-pairs arranged in such a way that the magnet rings have a known and desired relationship between the magnetic pole-pairs between the magnetic rings when physically aligned.
  • the rotary position encoder comprises sensor means in relation to each magnetic encoder ring, the sensor means measures the magnetic fields of the magnetic encoder rings and provides output signals proportional to the measured magnetic fields, the output signals are of a sinusoidal nature.
  • the magnetic encoder ring misalignment correction unit further comprises calculation means, comparison means, determining means and correction means.
  • the calculation means is arranged to calculate an expected first output signal of a first sensor means of a first magnetic encoder ring by means of a measured second output signal of a second sensor means of a second magnetic encoder ring using the known and desired relationship.
  • the comparison means is arranged to compare the expected first output signal with a measured first output signal of the first magnetic encoder ring.
  • the determining means is arranged to determine a degree of physical misalignment between the first and the second magnetic encoder rings based on the comparison done by the comparison means. In some embodiments there is also an averaging means that multiple comparisons of multiple calculated expected first output signals, and feeds this to the determining means.
  • the correction means is arranged to offset the measured first output signal of the first sensor means based on the determined degree of physical misalignment.
  • a rotary position encoder that according to the invention comprises a magnetic encoder ring misalignment correction unit as described above.
  • the sensor means are surface mounted on a common carrier to improve accuracy even further.
  • the different enhancements of the invention can be combined in any desired manner as long as no conflicting features are combined.
  • the aforementioned objects are also achieved according to the invention by a method of correcting a physical misalignment of magnetic encoder rings of a rotary position encoder comprising at least two magnetic encoder rings.
  • Each magnetic encoder ring comprises multiple magnetic pole-pairs arranged in such a way that the magnet rings have a known and desired relationship of the magnetic pole-pairs between the magnetic rings when physically aligned.
  • the rotary position encoder comprises sensor means in relation to each magnetic encoder ring, the sensor means measures the magnetic fields of the magnetic encoder rings and provides output signals proportional to the measured magnetic fields.
  • the output signals are of a sinusoidal nature.
  • the method comprises a plurality of steps.
  • an expected first output signal of a first sensor means of a first magnetic encoder ring is calculated by means of a measured second output signal of a second sensor means of a second magnetic encoder ring using the known and desired relationship.
  • the expected first output signal is compared with a measured first output signal of the first magnetic encoder ring.
  • a degree of physical misalignment between the first and the second magnetic encoder rings is determined based on the comparison done by the second step.
  • the measured first output signal of the first sensor means is corrected by an offset based on the determined degree of physical misalignment.
  • a primary purpose of the invention is to provide an improved accuracy of rotational position encoders utilizing two or more magnetic encoder rings.
  • Fig. 1 illustrates a typical control system application of the invention, illustrates a typical position encoder setup application according to the invention, illustrates a side view of a position encoder setup according to the invention, where encoder magnet rings are arranged at radially different distances and preferably in a same plane
  • Fig. 3B illustrates a top view of a position encoder setup according to
  • Figure 3A illustrates a side view of an alternative position encoder setup according to the invention, where encoder magnet rings are arranged along an axle at axially different locations, preferably at a same radial distance from the axle, illustrates a flow chart of a method according to the invention of electronically aligning a first and a second encoder ring such that the first and second magnetic encoder rings together with their corresponding sensor units produce a known phase shift difference, such as zero, between them related to a common reference position of the axle.
  • the invention relates to position encoders and especially position encoders used to determine the relative rotational position between a rotor and a stator of an electric motor, especially a brushless DC motor.
  • the relative rotationa! position between the rotor and stator is used by the control electronics to correctly drive the motor. It is especially important to accurately know the relative rotational position between the stator and rotor to be able to control the motor efficiently from standstill and at low speeds.
  • the invention thus relates to increasing the accuracy of rotary position encoders, especially rotary position encoders comprising two or more encoder magnet rings.
  • Such encoders can for example be using two or more multi-pole magnetic rings/discs and hall effect sensors, where each multi-pole magnetic disc has a different number of magnetic pole-pairs.
  • a basic concept of the invention is to electronically rotationally align the magnet rings in relation to any mechanical rotational misalignment.
  • the invention thus puts the magnet rings in an electronically known relationship to each other. This will increase the accuracy of the rotary position encoder. Further it turns out that it is not important for the control electronics to know a relative rotational position between the stator and the rotor over a full turn, but only the relative rotational position of the rotor and stator between two poles of the motor.
  • the invention is also very suitable for absolute positional encoders divided into as many parts as poles of an attached electrical motor.
  • absolute rotational position encoders only for the rotational angle of 2 ⁇ radians divided by the number of poles (or 360 degrees divided by the number of poles) of an electrical motor to which it is to be attached. Certain embodiments of the invention are thus based on not having a requirement of knowing an absolute rotational position for a full turn. By having a rotational position encoder that provides absolute rotational position values that repeat a multiple of times during a full turn, it is possible to manufacture a more accurate encoder than if it would have to provide unique absolute rotational position values for a full turn.
  • Figure 1 illustrates a typical application of the invention, where a brushless DC motor 100 is driven/controlled by a motor controller 120 with the help of a position encoder, suitably an absolute position encoder 110.
  • the position encoder 110 is coupled to the motor axle 102 of the motor 100.
  • the position encoder provides the motor controller 120 with a position signal 115 that represents the rotary position of the motor axle 102 and thus the positional relationship between a stator and a rotor of the motor.
  • the motor controller 120 can convert a supplied power 125 into correct power signals 105 to feed to the motor.
  • FIG 2 illustrates a position encoder 210 setup.
  • the position encoder 210 will detect a rotational 203 position of an axle 202 and transform/encode this physical position into an electrical position signal 215.
  • the position encoder is preferably an absolute rotary position encoder 210 as this enables a motor controller to immediately know the relationship between rotor and stator even from power off, without having to rotate past a reference point. This is important to enable a smooth start up of the motor.
  • the invention is from a practical point of view intended to be used in conjunction with absolute rotational position encoders.
  • An absolute rotational position encoder will provide a relevant position signal when turned-on even though for example a motor axle has been physically rotated when the encoder was tumed-off. This in contrast with an incremental position encoder that will start from zero each time it is turned on until it has possibly rotated past a synchronization mark. Thus, an incremental position encoder will not detect at power-on that for example an axle has rotated during the encoder's tumed-off period.
  • an absolute rotary position encoder For an absolute rotary position encoder to accurately be abie to give a representation of the rotational position of an axle, such as an axle of a brushless DC motor, it needs to be very accurately mounted directly on or coupled to the axle in question. Such a mounting is difficult and takes time. It is not sure that the attained results are those desired, due to for example a misalignment between axle and rotor.
  • a rotary position encoder such as an absolute rotary position encoder, coupled to for example an axle, is electronically aligned with the axle.
  • An electronic alignment device further has the possibility to further adjust a possible offset between the axle and for example a brushless DC motor's rotor.
  • Figure 3A illustrates a side view of a position encoder setup according to the invention, where encoder magnet rings 340, 345 are arranged at radially different distances and preferably in a same plane.
  • Figure 3B illustrates a top view. Reference is made to both Figure 3A and 3B.
  • the encoder magnet rings 340, 345 are typically mounted in a same plane about a rotatable 303 axle 302.
  • Each encoder magnet ring 340, 345 will comprise a plurality of magnetic pole-pairs. With a sufficient number of magnetic pole-pairs around an encoder magnet ring 340, 345 a corresponding sensor unit 350, 355 will produce a sine wave output.
  • the outputs from the sensor units 350, 355 are read and one or possibly both outputs are automatically adjusted in such a way as if the encoder magnet rings were mechanically aligned.
  • the magnet rings are electronically aligned to attain the known relationship that the magnet rings should have when they are physically aligned.
  • the adjustment can be done in the encoder itself, be part of/executed by a motor controller or executed by a separate unit between the encoder and the motor controller. The method will be described in detail below.
  • a further aspect of the invention to improve the accuracy of the encoder is to surface mount the sensor units 350, 355 on a common carrier 359.
  • Surface mounting today is able to attain a very high mechanical accuracy thus ensuring that the spatial relationship between the sensor units 350, 355 is well defined.
  • any spatial relationship between subcomponents/sensor elements of each sensor unit 350, 355, if they comprise subcomponents such as multiple sensor elements, will also be well defined.
  • Figure 4 illustrates a side view of an alternative position encoder setup according to the invention, where encoder magnet rings 440, 445 are arranged along an axle at axially different locations, preferably at a same radial distance from a rotating 403 axle 402.
  • This embodiment also comprises corresponding sensor units 450, 455 mounted on a carrier 459.
  • Figure 5 illustrates a flow chart of a method according to the invention of electronically aligning a first and a second encoder ring such that the first and second magnetic encoder rings together with their corresponding sensor units produce a known phase shift difference, such as zero, between them related to one or more common reference position(s) of a rotating axle.
  • a first step 510 signals received from sensor units of a first and a second encoder magnet ring are conditioned for further processing.
  • a first position angle of the first encoder magnet ring and a second position angle of the second encoder magnet ring, both in relation to a preferably common predetermined axle position are calculated/determined by means of the conditioned signals.
  • an expected second (alternatively expected first) position angle is determined/calculated from the first (alternatively second) position angle.
  • the expected second (alternatively expected first) position angle would be identical to the second (alternatively first) position angle if the first and second encoder magnet rings were physically aligned. In some embodiments there can be several expected second position angles. In these cases the expected second position angle that is closest to the calculated/determined second position angle of the second step 520 is chosen as the expected second position angle.
  • a fourth step 540 after the third step 530, an alignment angle is determined/calculated by at least a comparison of the expected second (alternatively expected first) position angle with the second (alternatively first) position angle, the alignment angle giving an indication of the physical misalignment of the first and second encoder magnet rings.
  • a first optional step 550 optionally after the fourth step 540, the alignment angle is averaged with previously determined/calculated alignment angles. Suitably unrealistic values are rejected.
  • a fifth step 560 either after the fourth step 540 or after the first optional step 550, further deterrninaiions/caicuiations of the second position angle (alternatively the first position angle) are adjusted with the alignment angle.
  • a continued averaging should be made, and in such a case the process continues with the first step 510, otherwise the process is closed.
  • the method of the invention can be implemented in direct connection with the sensor units, thereby allowing the position encoder to be completely self calibrating.
  • the method according to the invention can be implemented in a motor controller unit.
  • the method according to the invention can be implemented in a separate unit that can be connected between a position encoder and a motor controller.
  • input means are required to be able to sample/read the output from the sensor units of the two or more magnetic encoder rings.
  • Processing means together with memory means, are required to process the received signals from the sensor units, to thereby calculate what the physical angular offset between the two magnet rings is and suitably correct one or both of the sensor unit signals and provide this to output means.
  • the memory means being used to save the offset and possibly to support calculating for example running averages of the offset.
  • FIGURE 1 - illustrates a typical control system application of the invention
  • FIGURE 2 - illustrates a typical position encoder setup application according to the invention
  • FIGURE 3A illustrates a side view of a position encoder setup according to the invention, where encoder magnet rings are arranged at radially different distances and preferably in a same plane,
  • FIGURE 3B illustrates a top view of a position encoder setup according to
  • Figure 3A, 302 an axle
  • FIGURE 4 illustrates a side view of an alternative position encoder setup according to the invention, where encoder magnet rings are arranged along an axle at axially different locations, preferably at a same radial distance from the axle,
  • FIGURE 5 illustrates a flow chart of a method according to the invention of electronically aligning a first and a second encoder ring such that the first and second magnetic encoder rings together with their corresponding sensor units produce a known phase shift difference, such as zero, between them related to a common reference position of the axle,
  • signals received from sensor units of a first and a second encoder magnet ring are conditioned for further processing
  • a first position angle of the first encoder magnet ring and a second position angle of the second encoder magnet ring, both in relation to a preferably common predetermined axle position are calculated/determined by means of the conditioned signals
  • a third step after the second step 520, an expected second (alternatively expected first) position angle is determined/calculated from the first (alternatively second) position angle, the expected second (alternatively expected first) position angle would be identical to the second (alternatively first) position angle if the first and second encoder magnet rings were physically aligned
  • an alignment angle is determined/calculated by at least a comparison of the expected second (alternatively expected first) position angle with the second (alternatively first) position angle, the alignment angle giving an indication of the physical misalignment of the first and second encoder magnet rings,
  • the alignment angle is averaged with previously determined/calculated alignment angles
  • a fifth step either after the fourth step 540 or after the first optional step 550, further determinaiions/caicuiations of the second position angle (alternatively the first position angle) are adjusted with the alignment angle,

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Transmission And Conversion Of Sensor Element Output (AREA)

Abstract

La présente invention porte sur une unité et sur un procédé pour déterminer et compenser électroniquement un défaut d'alignement physique entre deux ou plusieurs bagues de codeur à aimant. La sortie de capteur de chaque bague de codeur à aimant est mesurée. Les mesures sont ensuite associées à des valeurs prévues par rapport à une ou plusieurs positions angulaires prédéterminées. Le résultat détermine alors si une des sorties de capteur ou si toutes les sorties de capteur doivent recevoir un décalage de façon à faire ainsi en sorte, avec la fonction de décalage, que les bagues de codeur à aimant paraissent physiquement alignées.
PCT/EP2010/006652 2009-11-13 2010-11-01 Procédé et unité de détection de position WO2011057727A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EPPCT/EP2009/008095 2009-11-13
EP2009008095 2009-11-13

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WO2011057727A1 true WO2011057727A1 (fr) 2011-05-19

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8835832B2 (en) 2012-01-17 2014-09-16 Avago Technologies General Ip (Singapore) Pte. Ltd. Optical encoder with signal offset correction system
JP2015114209A (ja) * 2013-12-12 2015-06-22 セイコーエプソン株式会社 エンコーダー及び電気機械装置
CN106774451A (zh) * 2016-12-31 2017-05-31 深圳市优必选科技有限公司 基于磁编码的多圈角度控制方法及装置

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19641035A1 (de) * 1996-10-04 1998-04-09 Heidenhain Gmbh Dr Johannes Vorrichtung und Verfahren zur Positionsmessung
WO2003004974A1 (fr) * 2001-07-05 2003-01-16 Robert Bosch Gmbh Procede et dispositif pour determiner un angle de rotation ou une course
DE102004001570A1 (de) * 2004-01-10 2005-12-29 AMK Arnold Müller GmbH & Co. KG Magnetische Messvorrichtung
DE102005035881A1 (de) * 2004-08-28 2006-03-02 Luk Lamellen Und Kupplungsbau Beteiligungs Kg Verfahren zum Bestimmen der Drehwinkellage der Nockenwelle einer Hubkolben-Verbrennungsmaschine relativ zur Kurbelwelle
US7170279B2 (en) * 2000-08-22 2007-01-30 Robert Bosch Gmbh Device and method for measuring angles
EP2073372A1 (fr) * 2007-12-19 2009-06-24 Vestas Wind Systems A/S Système de générateur avec un traitement intelligent de signal de position

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19641035A1 (de) * 1996-10-04 1998-04-09 Heidenhain Gmbh Dr Johannes Vorrichtung und Verfahren zur Positionsmessung
US7170279B2 (en) * 2000-08-22 2007-01-30 Robert Bosch Gmbh Device and method for measuring angles
WO2003004974A1 (fr) * 2001-07-05 2003-01-16 Robert Bosch Gmbh Procede et dispositif pour determiner un angle de rotation ou une course
DE102004001570A1 (de) * 2004-01-10 2005-12-29 AMK Arnold Müller GmbH & Co. KG Magnetische Messvorrichtung
DE102005035881A1 (de) * 2004-08-28 2006-03-02 Luk Lamellen Und Kupplungsbau Beteiligungs Kg Verfahren zum Bestimmen der Drehwinkellage der Nockenwelle einer Hubkolben-Verbrennungsmaschine relativ zur Kurbelwelle
EP2073372A1 (fr) * 2007-12-19 2009-06-24 Vestas Wind Systems A/S Système de générateur avec un traitement intelligent de signal de position

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8835832B2 (en) 2012-01-17 2014-09-16 Avago Technologies General Ip (Singapore) Pte. Ltd. Optical encoder with signal offset correction system
JP2015114209A (ja) * 2013-12-12 2015-06-22 セイコーエプソン株式会社 エンコーダー及び電気機械装置
CN106774451A (zh) * 2016-12-31 2017-05-31 深圳市优必选科技有限公司 基于磁编码的多圈角度控制方法及装置

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