WO2016075571A1 - Actionneur magnétique bistable - Google Patents

Actionneur magnétique bistable Download PDF

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Publication number
WO2016075571A1
WO2016075571A1 PCT/IB2015/058069 IB2015058069W WO2016075571A1 WO 2016075571 A1 WO2016075571 A1 WO 2016075571A1 IB 2015058069 W IB2015058069 W IB 2015058069W WO 2016075571 A1 WO2016075571 A1 WO 2016075571A1
Authority
WO
WIPO (PCT)
Prior art keywords
magnets
magnet
soft magnet
bistable actuator
actuator
Prior art date
Application number
PCT/IB2015/058069
Other languages
English (en)
Inventor
Sreedhar Babu GOLLAPUDI
Rajamani Bhaskar MARIMANUKUPPAM
Satyanarayana Raju CHETLAPALLI
Original Assignee
Director General, Defence Research & Development Organisation (Drdo)
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 Director General, Defence Research & Development Organisation (Drdo) filed Critical Director General, Defence Research & Development Organisation (Drdo)
Publication of WO2016075571A1 publication Critical patent/WO2016075571A1/fr

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F7/00—Magnets
    • H01F7/06—Electromagnets; Actuators including electromagnets
    • H01F7/08—Electromagnets; Actuators including electromagnets with armatures
    • H01F7/16—Rectilinearly-movable armatures
    • H01F7/1638—Armatures not entering the winding
    • H01F7/1646—Armatures or stationary parts of magnetic circuit having permanent magnet
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F7/00—Magnets
    • H01F7/06—Electromagnets; Actuators including electromagnets
    • H01F7/08—Electromagnets; Actuators including electromagnets with armatures
    • H01F7/16—Rectilinearly-movable armatures
    • H01F2007/1669—Armatures actuated by current pulse, e.g. bistable actuators

Definitions

  • Embodiment of the present disclosure relates to a bi-stable magnetic actuator. More particularly, embodiments of the disclosure relate to an electro magnet for the transition phase and permanent magnet for holding phase in a bi-stable magnetic actuator.
  • electro-permanent magnet which is a device that can have its external magnetic field switched ON and OFF by an electrical pulse, and retains its magnetic state with zero power.
  • the electro-permanent magnets are strong, low-power devices at small scales, because their switching energy scales with volume, while their holding force scales with area.
  • heat from I 2 R (Ohmic losses) losses in the electromagnets has been a major limit on performance, manifesting itself either as destructive temperature rise, high power requirements, or low force capability. This can be by overcome by using pulse-driven electro-permanent magnets.
  • an electro-permanent magnet's external magnetic field can be modulated by an electrical pulse. Thereafter, no electrical power is required to maintain the field. Power is required only during mechanical working or changing the device's state.
  • the electro permanent magnets as shown in Figure 1 comprises two magnetic materials, a magnetically hard (NIB) and a semi-hard (Alnico) material, capped at both ends with a magnetically soft material (Iron) and wrapped with a coil.
  • the passing of current pulse diverts some part of flux or entire flux to circulate inside the device, thereby reducing the external magnetic flux.
  • the method of passing the pulse of current through the coil in one direction magnetizes the material in the same direction. In this state, the flux exits the device and exerts a holding force.
  • the passing of a pulse of current through the device in the opposite direction reverses the magnetization of the lower coercivity magnet but leaves the high coercivity magnet unchanged. In this state, the two magnets are oppositely magnetized and so the magnetic flux only circulates inside the device and there is no holding force.
  • EPM electro-permanent magnet
  • series EPM series EPM
  • parallel EPM electro-permanent magnet
  • the monostable EPM are made by temporarily reversible permanent magnets based on flux cancellation or flux switching principle.
  • flux cancellation principle the EPM is constructed by wrapping a permanent magnet with a coil. When the coil is switched off, the permanent magnet holds a load. The switching ON of the magnets, releases the load and when the coil is switched OFF, the field returns.
  • flux switching principle it is constructed by placing a permanent magnet and a coil in parallel between two Ferro magnetic pole pieces. When the coil is OFF, the permanent magnet exerts a holding force on nearby object. When the coil is turned on, the flux from the permanent magnet is shunted through the coil and the holding force switches OFF. When the coil is turned OFF, the holding force resumes.
  • a row of permanent magnets alternatively made from high coercivity materials and low coercivity materials are used. Initially, all the magnets are magnetized together and their flux passes through the bottom member. Coils surround the low coercivity magnet. Passing a momentary pulse of current through the coils reverses their magnetization. Now the net field across the bottom is zero so that no flux flows through it. Rather, the flux from each magnet exits the plate separately through the top, holding down the work piece.
  • the parallel EPMs comprise two types of permanent magnetic materials, a high coercivity (NIB) and a lower coercivity (AINiCo). The two materials are place in parallel and surrounded by a coil.
  • bi-stable actuators similar to parallel EPM with two stable positions, one being held by spring and the other with permanent magnet. The switching is performed with a solenoid coil.
  • a bi-stable actuator uses mutual magnetic repulsion for actuation.
  • the bi-stable actuator comprises two permanent magnets members, which act in master, slave roles to achieve the two stable states.
  • a mono- stable actuator by magnetic means uses an additional kinematic motion assembly to make it bi-stable actuator.
  • an electro-magnetic actuator consists of two permanent magnets arranged along polar axis with proximal poles with same polarity.
  • the present disclosure provides a bistable actuator comprising at least two magnets (7) interconnected through a central rod (5), said central rod (5) acts as a plunger connecting the at least two magnets and moves the at least two magnets as a single body, wherein surfaces of the two magnets facing each other are configured to have same polarity.
  • the bistable actuator also comprises at least one soft magnet (6) configured around the central rod (5) between the two magnets (7), wherein the at least one soft magnet (6) is of bobbin shape.
  • the bistable actuator comprises a copper coil (11), wound around the at least one bobbin shaped soft magnet, the copper coil magnetizes the at least one soft magnet to a polarity based on an applied electric pulse.
  • the at least one soft magnet (6) is attracted to one of the two magnets (7) based on the applied electric pulse, which is instantaneous.
  • Figure 1 shows an electro permanent magnet, in accordance with a prior art
  • Figure 2 shows a cross sectional view of a bistable actuator in accordance with an embodiment of the present system.
  • Figures 3a and 3b illustrate principle of operation in initial position of the magnets and change in position of the magnets on application of electrical pulse in accordance with an embodiment of the present disclosure
  • Figure 4 shows a perspective view of a bistable actuator, in accordance with an embodiment of the present disclosure.
  • FIG. 5 shows force generation in the bistable actuator, in accordance with an embodiment of the present disclosure
  • FIG. 5 shows force generation in the bistable actuator, in accordance with an embodiment of the present disclosure
  • the figures depict embodiments of the disclosure for purposes of illustration only.
  • One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
  • An exemplary embodiment of the present disclosure provides a bistable actuator comprising two magnets (7) interconnected through a central rod (5), which acts as a plunger connecting the at least two magnets and moves the at least two magnets as a single body.
  • the surfaces of the two magnets facing each other have same polarity.
  • the bistable actuator comprises at least one soft magnet (6) configured around the central rod (5) between the two magnets (7).
  • the at least one soft magnet (6) is of bobbin shape.
  • the bistable actuator comprises a copper coil (11), wound around the at least one bobbin shaped soft magnet, the copper coil magnetizes the at least one soft magnet to a polarity based on an applied electric pulse.
  • the at least one soft magnet (6) is attracted to one of the two magnets (7) based on the applied electric pulse, which is instantaneous.
  • One embodiment of the present disclosure is a device capable of operating in two states, referred as bi-stable, with respect to its last known position by changing the direction of the coil current in the field windings.
  • the holding in both states is without any electrical power, i.e. by permanent magnets only.
  • the device has at least one of the additional features such as, but not limited to, compact, simple, light weight, low shock, faster response, safe to use and maintain with minimum number of components.
  • the peak power current may be required only during transition state and holding in state with no power.
  • a secondary aerospace actuation mechanisms uses pyro based systems, solenoids and shape memory alloy based systems.
  • the pyro systems have limitations in terms of single shot operation, not testable, can't be reset on-board, high pyro shock etc.
  • the shape memory alloy based systems also have limitations like costly, sluggish, not resettable on-board etc.
  • the solenoid systems are very popular but have limitations like bulky, needs large amount of copper, continuous power during operation, sluggish and can cater for only smaller strokes.
  • the present disclosure aims at compact, high bandwidth, low power, and high speed bi-stable actuator with larger strokes.
  • the present invention addresses all the above issues.
  • the bi-stable actuators claimed in invention are based on Electro permanent magnets. They require instantaneous power for a few milliseconds. They are compact, low weight, less copper windings, low cost, cater for larger strokes, less shock, faster operation and high bandwidth systems which replaces the conventional aerospace actuation systems.
  • FIG. 2 shows an exemplary cross sectional view of a bistable actuator in accordance with an embodiment of the present system.
  • the bistable actuator comprises two permanent magnets or hard magnets (7), which are inter connected to each other using a central rod/ shaft arrangement or central rod/ shaft (5).
  • the central rod (5) facilitates the motion of the two permanent magnets (7) as a single unit.
  • these permanent magnets are referred as hard magnets.
  • the central rod/ shaft (5) configured in the bistable actuator, to which both the hard magnets are fastened at the ends, functions as a plunger connecting the two hard magnets (7) and making them to move as a single body.
  • the bistable actuator also comprises a soft magnetic material or magnet (6), which is in the form of a bobbin and with a provision to wind a copper coil (11) around the bobbin.
  • the soft magnetic (6) hereinafter is referred as a bobbin.
  • the copper coil (11) enclosing the bobbin acts as magnetizer during the small duration of electric pulse and magnetizes the bobbin with proper polarity to switch between the two stable states.
  • the bobbin acts as a core of electro magnet during transition stage, and acts as an iron for the permanent magnet during holding stage in both extreme stable states.
  • the soft magnet (6) is configured to be held in a middle position of an assembly by fixing it to the body (2) of the bistable actuator, using a spacer arrangement.
  • the bobbin (6) comprises a central hole through which a shaft or a rod, here it is the central rod (5) connecting the two permanent magnets, moves.
  • the bobbin is fixed to the body (2) of the bistable actuator.
  • the movement of central rod (5) makes the permanent magnets to contact the bobbin surface, which is based on the movement of the central rod (5).
  • the permanent magnets are arranged to have same polarity on their surfaces facing each other.
  • a bistable actuator comprises of coaxial armature, which requires a single electrical coil with minimum copper, two high power permanent magnets, which can provide large holding force at both stable positions and during the transition both the permanent magnets provide the required motion with synergy, minimum degradation of force during the transition phase, resulting in a very compact, low weight and high speed secondary actuation system for aerospace systems.
  • the bistable actuator system does not require any springs or other arrangements for bistable actuation. This results in low friction during the actuation of the bistable actuation system.
  • the system response time is of the order of milli seconds and requires very less power consumption compared to the conventional available solenoids or any other conventionally known bistable actuators.
  • the assembly of the bistable actuator system is easier to fabricate and build a prototype.
  • the bistable actuator of the present disclosure uses a combination of soft and hard magnetic materials to create a bistable actuation system.
  • the bistable actuator based on electro permanent magnet operation uses only a short duration electric pulse of very high instantaneous power. The overall energy of almost zero is required for changing the state of the bistable actuator system. The holding force required for the two extreme stable states is achieved by the permanent magnets.
  • the bistable actuation assembly consists of soft magnetic material based central bobbin.
  • Figures 3a and 3b illustrate principle of operation in initial position of the magnets and change in position of the magnets on application of electrical pulse in accordance with an embodiment of the present disclosure.
  • initially the bobbin (6) is in contact with a permanent magnet on the left side with polarities North (N), on left side and South (S), on right side of the permanent magnet.
  • the permanent magnet pole south (S) attracts the bobbin pole surface north (N).
  • an electrical pulse is passed through the coil (11) to the bobbin (6), the bobbin surface poles are reversed.
  • FIG. 4 shows a perspective view of a bistable actuator, in accordance with an embodiment of the present disclosure.
  • the bistable actuator system comprises an extended rod to the central shaft at one end to ascertain the motion of the central shaft.
  • the bistable actuator system is tested with a pre-requisite power supply and the time of response is measured i.e. the movement of the central shaft is achieved within a time frame of 20 milli seconds.
  • the bistable actuator system draws the peak power (peak current) for 20 milli seconds during the operation of the actuation system.
  • Figure 5 shows force generation in the bistable actuator, in accordance with an embodiment of the present disclosure. As shown in the figure 5, it shows three different cases/ examples. In first case or case 1, a 10 mm thick hard or permanent magnet with one side soft magnet is used in the bistable actuator. In second case or case 2, a 6 mm thick hard or permanent magnet with one side soft magnet is used in the bistable actuator, and in third case or case 3, a 6 mm thick hard or permanent magnet with soft magnet on both sides. In one embodiment, the overall dimensions of all the magnets are 36 mm outer diameter, 10 mm internal diameter and 10 mm thickness. The magnet for the case 2 and case 3 has a thickness of 6 mm.
  • a plate required is of 25 kgf.
  • the same hard magnet material of 6 mm thickness needed is 14 kg, whereas the same magnet of 6mm thick, when to be separated from two parallel steel plates required is 46 kgf for separation.
  • the separation force depends on may parameters of both soft and hard magnets in terms of shape, size, material, saturation, Maximum flux density, temperature and thickness.
  • the central core is a soft magnetic material which may be supra
  • the thickness is maintained so that the soft magnet is not saturated when in contact with hard permanent magnet.
  • the hard magnet may be NdFeB rings with a proper polarity.
  • the coil (not shown in Figure 5) is wound around the soft magnet, which is of bobbin shape. The coil is configured to alter the polarity of the soft magnet by altering the current direction. Based on standard calculation, the force generated by the permanent magnet is given as
  • the force distance relation is used to obtain force acting at air gap intervals of 1mm.
  • pull load tests are conducted to obtain the actual pull force generated by the hard magnets with the soft magnet, these values are as shown in the figure 5.
  • One embodiment of the present disclosure provides the advantages of the bistable actuator such as faster operation compared to the conventional actuators or solenoid systems of similar type; the bistable actuator requires only instantaneous power for transition which lasts for a few mill seconds and no need of any power during the operation of the bistable actuator. Also, the amount of copper requirement for the actuator is very minimal compared to a solenoid of similar force generating actuator.
  • the coil heating problems does not exists in the of the bistable actuator of the present disclosure as compared to the conventional actuators and the overall energy consumption is minimal compared to similar solenoid based systems.
  • the polarity reversal is simple and sufficient to switch the states of the actuator.
  • the soft magnetic material works as electro magnet during transition phase and, as iron during long holding state. The total system is simple to operate easy to make, can generate more force compared to conventional or similar sized actuators and the system is able to stay in any of the stable states permanently.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Electromagnets (AREA)

Abstract

La présente invention concerne, dans un mode de réalisation, un actionneur bistable comportant deux aimants (7) interconnectés par l'intermédiaire d'une tige centrale (5), qui fait fonction de poussoir reliant lesdits au moins deux aimants et qui déplace lesdits au moins deux aimants solidairement. Les surfaces des deux aimants qui se font face présentent la même polarité. Par ailleurs, l'actionneur bistable comporte au moins un aimant doux (6) configuré autour de la tige centrale (5) entre les deux aimants (7). L'aimant ou les aimants doux (6) présente la forme d'une canette. En outre, l'actionneur bistable comporte une bobine (11) en cuivre, enroulée autour de l'aimant ou des aimants doux en forme de canettes, la bobine en cuivre magnétisant l'aimant ou les aimants doux en leur conférant une polarité dépendant d'une impulsion électrique appliquée. L'aimant ou les aimants doux (6) sont attirés vers l'un des deux aimants (7) en fonction de l'impulsion électrique appliquée, qui est instantanée.
PCT/IB2015/058069 2014-11-13 2015-10-20 Actionneur magnétique bistable WO2016075571A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IN3280/DEL/2014 2014-11-13
IN3280DE2014 2014-11-13

Publications (1)

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WO2016075571A1 true WO2016075571A1 (fr) 2016-05-19

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019121000A1 (fr) * 2017-12-19 2019-06-27 Assa Abloy Ab Actionneur comprenant un aimant électropermanent et procédé

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4259653A (en) 1977-11-22 1981-03-31 Magnetic Laboratories, Inc. Electromagnetic reciprocating linear actuator with permanent magnet armature
JPS5932111A (ja) * 1982-08-16 1984-02-21 Kiyoshi Hama ロツク機構付き電磁石装置
JPS61220310A (ja) * 1985-03-26 1986-09-30 Shiyuukou Denshi Kk 双方向ソレノイド
US4758811A (en) 1987-02-13 1988-07-19 Lectron Products, Inc. Bistable solenoid actuator
EP0759625A1 (fr) * 1995-08-23 1997-02-26 Rockwell Light Vehicle Systems (UK) Limited Actionneurs magnétiques
US6040752A (en) 1997-04-22 2000-03-21 Fisher; Jack E. Fail-safe actuator with two permanent magnets
US6255934B1 (en) 1998-07-31 2001-07-03 Eltek S.P.A. Bistable actuation device
WO2001069613A1 (fr) 2000-03-16 2001-09-20 Quizix, Inc. Mecanisme actionneur a aimant permanent
US6512435B2 (en) 2001-04-25 2003-01-28 Charles Willard Bistable electro-magnetic mechanical actuator

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4259653A (en) 1977-11-22 1981-03-31 Magnetic Laboratories, Inc. Electromagnetic reciprocating linear actuator with permanent magnet armature
JPS5932111A (ja) * 1982-08-16 1984-02-21 Kiyoshi Hama ロツク機構付き電磁石装置
JPS61220310A (ja) * 1985-03-26 1986-09-30 Shiyuukou Denshi Kk 双方向ソレノイド
US4758811A (en) 1987-02-13 1988-07-19 Lectron Products, Inc. Bistable solenoid actuator
EP0759625A1 (fr) * 1995-08-23 1997-02-26 Rockwell Light Vehicle Systems (UK) Limited Actionneurs magnétiques
US6040752A (en) 1997-04-22 2000-03-21 Fisher; Jack E. Fail-safe actuator with two permanent magnets
US6255934B1 (en) 1998-07-31 2001-07-03 Eltek S.P.A. Bistable actuation device
WO2001069613A1 (fr) 2000-03-16 2001-09-20 Quizix, Inc. Mecanisme actionneur a aimant permanent
US6512435B2 (en) 2001-04-25 2003-01-28 Charles Willard Bistable electro-magnetic mechanical actuator

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
ARA NERSES KNAIAN: "Ph.D Thesis", June 2010, MIT, article "Electro permanent Magnetic Connectors and Actuators: Devices and Their Application in Programmable Matter"

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019121000A1 (fr) * 2017-12-19 2019-06-27 Assa Abloy Ab Actionneur comprenant un aimant électropermanent et procédé
CN111542901A (zh) * 2017-12-19 2020-08-14 亚萨合莱有限公司 包括电永磁体的致动器及方法
CN111542901B (zh) * 2017-12-19 2022-02-01 亚萨合莱有限公司 包括软磁体的致动器及方法
US11454049B2 (en) 2017-12-19 2022-09-27 Assa Abloy Ab Actuator comprising electro permanent magnet and method

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