Linear actuator system with integrated transverse flux motor
An integrated motor linear actuator system includes one or more stator stages inside a housing. The stator stages have a winding and a stator core disposed about a common longitudinal axis, with a plurality of stator teeth configured to guide magnetic flux generated by the winding. A rotor is disposed along the longitudinal axis, within the stator stages, with a plurality of magnetic poles distributed circumferentially about the outer surface, adjacent the stator teeth, so that the stator stages are configured to drive the rotor into rotational motion about the longitudinal axis via the magnetic flux. A thrust tube and screw assembly are operationally coupled to the rotor, and configured to convert the rotational motion into linear motion of the thrust tube.
1 . An integrated motor linear actuator system comprising:
a stator comprising a plurality of stator stages disposed along an axial extent within a housing, each stator stage having a winding and a stator core disposed about a common longitudinal axis, with a plurality of stator teeth configured to guide magnetic flux generated by the winding;
a rotor disposed along the longitudinal axis with a plurality of magnetic poles disposed circumferentially about the rotor, adjacent the stator teeth, wherein the stator stages are configured to drive the rotor into rotational motion about the longitudinal axis, via the magnetic flux;
a nut and screw assembly operationally coupled to the rotor; and
a thrust tube coupled to the nut, wherein the nut and screw assembly is configured to convert the rotational motion of the rotor about the longitudinal axis into linear motion of the thrust tube along the longitudinal axis;
wherein the magnetic flux is generated in response to current loops induced in the respective windings, the current loops extending about the rotor, transverse to the longitudinal axis;
wherein the rotor comprises a hollow core rotor body disposed coaxially about the nut and screw assembly, extending longitudinally from a first end adjacent a rotor hub proximate a back end of the housing to a second end proximate a front end of the housing, with the nut disposed within the hollow core rotor body; and
a plurality of permanent magnets defining the magnetic poles in an alternating arrangement disposed along an outer surface of the hollow core rotor body, extending along the axial extent of the stator, adjacent the stator teeth across an air gap.
2 . The system of claim 1 , wherein:
each current loop defines a ring or annulus oriented about the rotor, substantially perpendicular to the longitudinal axis;
the current loop induced in each respective winding is disposed between the stator teeth and an outer radius of an annular body portion of the respective stator core; and/or
the stator teeth are disposed between the current loop induced in the respective winding and the magnetic poles disposed circumferentially about the rotor, across the air gap.
3 . The system of claim 1 , wherein the magnetic flux defines a flux path extending radially along the respective stator core and axially along alternating pairs of the stator teeth, in which the flux path is defined parallel and antiparallel to the longitudinal axis, respectively.
4 . The system of claim 1 , wherein alternating pairs of the stator teeth are disposed along opposing sides of each respective winding, extending in opposing directions along the longitudinal axis, adjacent the rotor, with the windings disposed between the alternating pairs of the stator teeth.
5 . The system of claim 4 , wherein the alternating pairs of the stator teeth define radial gaps on opposing sides of each respective winding, and further comprising a nonmagnetic fill material or potting compound disposed in the radial gaps, between the windings and the respective stator teeth, or between the windings and the annular body portions of the respective stator cores, or a combination thereof.
6 . The system of claim 1 , wherein the stator cores are formed of or comprise a polymer-based or composite material having lower density than iron, with magnetic properties selected for guiding the magnetic flux through the respective stator teeth, along a flux path oriented along the longitudinal axis adjacent the rotor, substantially parallel to one or more of the magnetic poles.
7 . The system of claim 1 , wherein the stator cores each comprise first and second axially engaged annular body portions with first and second alternating sets of the stator teeth extending in opposing directions therefrom, wherein the windings are engaged between the respective annual body portions and alternating sets of stator teeth.
8 . The system of claim 1 , further comprising a conductive or convective cooling system configured to dissipate heat generated by the stator stages to the housing, wherein a temperature of the system is maintained within a desired range for operation of the nut and screw assembly and thrust tube, absent active cooling of the respective windings or stator cores.
9 . The system of claim 1 , further comprising a heat pipe configured for convective flow of a thermally conductive fluid between one or more of the stator stages and the housing.
10 . The system of claim 1 , wherein the nut and screw assembly comprises a roller nut coupled to a proximal end of the thrust tube and a threaded screw shaft rotationally coupled to the rotor, the roller nut being engaged with the threaded screw shaft to convert the rotational motion of the rotor such that a distal end of the thrust tube reciprocates along the longitudinal axis, opposite the proximal end and outside the actuator housing.
11 . The system of claim 1 , wherein the stator stages comprise a plurality of sequentially ordered, modular stator stages with the stator teeth clocked about the longitudinal axis by an angle to define three different phases, and wherein the magnetic poles extend axially along a set of at least three of the sequentially ordered, modular stator stages, having the three different phases.
12 . The system of claim 1 , wherein the nut is wholly disposed within the hollow core rotor body, with the rotor coaxially disposed within the stator cores.
13 . The system of claim 1 , wherein the thrust tube is configured to prevent rotation during the linear motion of the thrust tube along the longitudinal axis.
14 . A method for operating an integrated motor linear actuator system, the method comprising:
inducing current in a stator comprising a plurality of stator stages disposed along an axial extent within a housing, wherein the stator stages comprise a plurality of windings, each of the windings extending about a longitudinal axis within a stator core;
guiding magnetic flux through the stator cores responsive to the current, wherein the magnetic flux defines a flux path extending radially from each stator core to a plurality of stator teeth distributed circumferentially about the longitudinal axis, and axially along the stator teeth, along the longitudinal axis at an inner diameter of the respective stator core;
driving a rotor having a hollow core rotor body into rotation about the longitudinal axis responsive to the magnetic flux, wherein the rotor comprises a plurality of magnets defining magnetic poles distributed circumferentially about an outer surface of the hollow core rotor body, extending along the axial extent of the stator, adjacent the stator teeth across an air gap; and
converting the rotation of the rotor into linear motion of a thrust tube, wherein the thrust tube translates along the longitudinal axis in response to the rotation of the rotor;
wherein inducing the current comprises defining a plurality of current loops extending circumferentially about the rotor in the windings, transverse to the longitudinal axis; and
wherein converting the rotation of the rotor to the linear motion of the thrust tube comprises:
rotationally engaging the rotor with a nut and screw assembly operationally coupled to the rotor, wherein the hollow core rotor body is disposed coaxially about the nut and screw assembly, extending longitudinally from a first end adjacent a rotor hub proximate a back end of the housing to a second end proximate a front end of the housing, with the nut disposed within the hollow core rotor body along the longitudinal axis, and
operationally coupling the nut with the thrust tube such that the thrust tube translates in one or more opposing directions along the longitudinal axis, in response to the rotation of the rotor in one or more opposing directions about the longitudinal axis.
15 . The method of claim 14 , wherein guiding the magnetic flux comprises defining a flux path along alternating, circumferentially adjacent pairs of the stator teeth, the alternating, circumferentially adjacent pairs of stator teeth extending radially on opposing sides of each of the windings and axially in the opposing directions along the longitudinal axis, between the respective windings and the outer surface of the rotor.
16 . The method of claim 15 , wherein driving the rotor comprises coupling the alternating, circumferentially adjacent pairs of stator teeth with alternating, adjacent pairs of the magnetic poles distributed circumferentially about the outer surface of the hollow core rotor body, via the flux path extending across the air gap.
17 . The method of claim 14 , further comprising inducing the current in the plurality of windings extending within a series of such stator cores distributed along the longitudinal axis, wherein the respective stator teeth are clocked about the longitudinal axis by an electrical angle selected to define three different phases, and wherein the magnetic poles distributed about the outer surface of the hollow core rotor body extend axially along at least three of the stator cores, having each of the three different phases.
18 . The method of claim 14 , further comprising:
convective cooling the stator cores with a heat pipe system configured to transport heat from the stator cores to a stator housing disposed about the stator cores; and/or
conducting heat generated by the windings to a stator housing disposed about the respective stator cores via a nonmagnetic fill material or potting compound disposed between the windings and the stator teeth, or between the windings and an annular body portion of the respective stator cores, or a combination thereof.
19 . The method of claim 14 , wherein the nut is wholly disposed within the hollow core rotor body, with the rotor coaxially disposed within the stator cores.
20 . The method of claim 14 , wherein the thrust tube is configured to prevent rotation when the thrust tube translates along the longitudinal axis.
21 . An integrated motor actuator comprising:
a stator comprising a plurality of stator stages disposed along an axial extent within a housing, each stator stage having a winding and a stator core disposed about a common longitudinal axis, with a plurality of stator teeth configured to guide magnetic flux generated by the winding; and
a rotor disposed along the longitudinal axis, within the plurality of stator stages, the rotor having a plurality of magnetic poles distributed circumferentially about an outer surface, adjacent the stator teeth;
wherein each winding defines a current loop disposed about the rotor when current is induced in the winding, transverse to the longitudinal axis;
wherein alternating pairs of the stator teeth extend on opposing sides of the current loops induced in the respective windings, the alternating pairs of stator teeth configured to drive the rotor into rotational motion about the longitudinal axis via coupling with the magnetic flux;
and further comprising:
a nut and screw assembly operationally coupled to the rotor; and
a thrust tube coupled to the nut, wherein the nut and screw assembly is configured to convert the rotational motion of the rotor about the longitudinal axis into linear motion of the thrust tube along the longitudinal axis;
wherein the rotor comprises a hollow core rotor body disposed coaxially about the nut and screw assembly, extending longitudinally from a first end adjacent a rotor hub proximate a back end of the housing to a second end proximate a front end of the housing, with the nut disposed within the hollow core rotor body; and
further comprising a plurality of surface-mounted permanent magnets circumferentially disposed about the outer surface of the hollow core rotor body, extending along the axial extent of the stator, wherein the surface-mounted permanent magnets define the magnetic poles.
22 . The integrated motor actuator of claim 21 , wherein the magnetic flux defines a flux path extending radially along the alternating pairs of the stator teeth in each stator stage, on the opposing sides of the current loops induced in the respective windings, and:
wherein the flux paths extend axially between the current loops induced in the respective windings and the outer surface of the rotor, in the opposing directions along the longitudinal axis; and/or
wherein the flux path defines the alternating pairs of stator teeth with opposite polarity, adapted to couple with an adjacent pair of the magnetic poles disposed about the outer surface of the hollow core rotor body, adjacent the respective stator teeth across an air gap.
23 . The integrated motor actuator of claim 21 , further comprising:
a convective cooling fluid loop disposed in thermal contact with the stator cores and configured to transport heat from the respective windings to the housing;
a heat pipe system configured to transport heat from the stator cores to the housing; and/or
a nonmagnetic fill material or potting compound disposed between the windings and the respective stator teeth, or between the windings and annular body portions of the respective stator cores, or a combination thereof, wherein the nonmagnetic fill material or potting compound is configured to conduct heat from the windings to the respective stator cores.
24 . The integrated motor actuator of claim 21 , wherein the stator cores are formed of a polymer-based or composite material having lower density than iron, with magnetic properties selected for guiding the magnetic flux generated by the respective windings.
25 . The integrated motor actuator of claim 21 , wherein:
the alternating pairs of stator teeth extend in the opposing directions along the longitudinal axis between the respective winding and the outer surface of the rotor, to respective radial gaps on the opposing sides of each current loop; and/or
the alternating pairs of stator teeth are circumferentially adjacent about the longitudinal axis, one tooth in each pair having a leg portion extending radially on a first side of the respective winding and an axial portion extending from the leg portion to the open end on a second side of the respective winding, opposite the first side, and another tooth in each pair having a leg portion extending radially on the second side of the respective winding and an axial portion extending from the leg portion to an open end on the first side of the respective winding, opposite the second side.
26 . The integrated motor actuator of claim 21 , further comprising:
at least three of the plurality stator stages being disposed along the longitudinal axis in sequential order, wherein the at least three stator stages are clocked about the longitudinal axis by an angle to define three different phases, in the sequential order; and
wherein the magnetic poles distributed about the outer surface of the hollow core rotor body extend axially along the at least three stator stages defining the three different electrical phases, in sequential order.
27 . The integrated motor actuator of claim 21 , wherein the nut is wholly disposed within the hollow core rotor body, with the rotor coaxially disposed within the stator cores.
28 . The integrated motor actuator of claim 21 , wherein the thrust tube is configured to prevent rotation during the linear motion of the thrust tube along the longitudinal axis.