Hybrid motor

A multi-phase motor including a rotor and a stator including at least one core. The stator includes a plurality of phase sections. Each phase section is configured to provide a phase of the multi-phase motor. Each phase section includes at least one of the core(s), at least two ring magnets having polarity facing in a substantially same direction, and a winding between the at least two ring magnets. The winding is configured to be energized to direct flux through the at least one core at a first portion associated with a first one of the ring magnets, and to be differently energized to direct flux through the at least one core at a second portion associated with a second one of the ring magnets.

BACKGROUND

1. Technical Field

The exemplary and non-limiting embodiments relate generally to a motor and, more particularly, to a multi-phase motor.

2. Brief Description of Prior Developments

U.S. Pat. No. 6,246,561, which is hereby incorporated by reference in its entirety, discloses controlling a path of magnetic flux from a permanent magnet.

SUMMARY

In accordance with one aspect, an example embodiment comprises a multi-phase motor including a rotor and a stator including at least one core. The stator includes a plurality of phase sections. Each phase section is configured to provide a phase of the multi-phase motor. Each phase section includes at least one of the core(s), at least two ring magnets having polarity facing in a substantially same direction, and a winding between the at least two ring magnets. The winding is configured to be energized to direct flux through the at least one core at a first portion associated with a first one of the ring magnets, and to be differently energized to direct flux through the at least one core at a second portion associated with a second one of the ring magnets.

In accordance with another aspect, an example method of assembly comprises locating a winding between two ring magnets to form an assembly, where the ring magnets have polarity facing in a substantially same direction; locating a plurality of the winding and ring magnet assembly in at least one core to form a motor stator; and locating the motor stator around a rotor.

In accordance with another aspect, an example embodiment comprises a substrate transport apparatus comprising a substrate transport arm; and a drive connected to the substrate transport arm. The drive comprises a multi-phase motor. The motor comprises a rotor and a stator. The stator comprises phase sections each including a core, two ring permanent magnets having polarity facing in a substantially same direction, and a winding between the two magnets. The winding is configured to be energized to direct flux through a first portion of the core associated with a first one of the magnets and to be differently energized to direct flux through a second portion of the core associated with a second one of the magnets.

DETAILED DESCRIPTION OF EMBODIMENTS

Referring toFIG. 1, there is shown a schematic top plan view of an example substrate processing apparatus1having a substrate transport apparatus or robot system2. Although the present invention will be described with reference to the embodiments shown in the drawings, it should be understood that the present invention may be embodied in many forms of alternative embodiments. In addition, any suitable size, shape or type of materials or elements could be used.

In addition to the substrate transport apparatus2, in this example embodiment the substrate processing apparatus1includes multiple substrate processing chambers4and substrate cassette elevators6connected to a vacuum chamber5. The transport apparatus10is located, at least partially, in the chamber5and is adapted to transport planar substrates, such as semiconductor wafers or flat panel displays, between and/or among the chambers4and elevators6. In alternate embodiments, the transport apparatus2could be used in any suitable type of substrate processing apparatus. A controller3may be connected to the transport apparatus2and chambers4,6to control the various devices.

A conventional vacuum environment robotic manipulator typically includes a drive unit which houses all active components of the robotic manipulator, e.g., actuators and sensors, and one or more arms driven by the drive unit. The arm(s) are typically passive mechanisms, i.e., they do not include any active components, such as actuators and sensors. This is primarily due to difficulties with out-gassing, power distribution and heat removal in vacuum environments.

In a conventional vacuum environment robotic manipulator, since the arm(s) of the robotic manipulators are passive mechanisms, the number of independently driven links is limited to the number of motion axes provided by the drive unit and further constrained by the complexity of transmission of the actuation torques to the individual links of the arm(s). This may limit the arm configurations used in practice, which in turn may limit the reach and throughput performance of the existing vacuum environment robotic manipulators.

Referring also toFIG. 2, in this example embodiment the robot system or substrate transport apparatus2includes a drive unit1012and a substrate transport arm1014. The drive unit1012may enable a plurality of rotary motion axes and vertical lift motion axes and one or more arm assemblies, e.g., arm assembly1014driven by the drive unit1012. Drive unit chassis1016may be suspended from mounting arrangement1018. The arrangement1018may be a chamber, such as the vacuum chamber5. Alternatively, the mounting arrangement may be on the side, at the bottom, or the drive unit may be mounted in any other suitable manner. Drive unit1012may include one or more vertical rails1020with linear bearings1022,1024to provide guidance to movable housing1026vertically driven by screw1028rotated by motor1030. Ball assembly1032is fixed to housing1026and is driven by screw1028. In this example, only one guide rail1020is shown for simplicity. Motor1030, screw1028, and ball assembly1032may form the Z-axis drive for housing1026.

Housing1026, itself, may incorporate two rotary motion axes. The first rotary motion axis of housing1026may comprise a motor,1034(e.g., a stator/rotor pair), and a position encoder, including, for example, encoder read-head1038and encoder disk1040for shaft1042. The second rotary motion axis incorporated into the housing may include another motor1036and a position encoder, comprising, for example, encoder read-head1044and encoder disk1046for shaft1048.

Housing1026of the drive unit1012may have an internal motor configuration (rotors internal to stators) and a radial position encoder configuration (encoder read-heads arranged radially with respect to encoder disks). Although motors and one arm are shown, more may be provided. In alternate aspects, the various motor and encoder arrangements used in housing1026may employ external motor configurations (see for example U.S. Pat. No. 6,363,808 which is hereby incorporated by reference in its entirety). In addition, as a feature of one or more embodiments of the robot system with independent arms, the motors in each housing, whether configured in an internal or external arrangement, may be located coaxially or in a parallel configuration in the same plane (as opposed to being stacked). The stators may be located in vacuum, and a separation wall between the stators and rotors may be used, magnetic couplers or feed through(s) may be employed or another sealing arrangement may be used.

In the example shown, two rotary motion axes, one vertical lift axes, and one arm is shown. However, in other examples, any number of rotary motion axes, vertical lift axes, and arms may be used.

In one aspect, bellows1050may be used to accommodate motion of housing1026along rail(s)1020separating the environment where motor rotors and encoder disks operate, for example, in a vacuum from the outside environment, e.g., the atmosphere. Although the drive unit1012has been described in detail above, it should be understood that features as described herein may be used with any suitable drive.

Motor1034may drive hollow shaft1042which may be connected to first link1060of arm assembly1014. Similarly, motor1036may be connected to coaxial inner shaft1048which may be coupled (via a belt drive comprising, for example, pulley1062, belt1064and pulley1066) to second link1068. Alternately, motor36and encoder1044,1046may be packaged in the first link1060directly or indirectly driving the second link1068.

In this example embodiment the substrate transport arm has an end-effector1070at an end of the second link1068. A shaft1080incorporated into the first link1060, and the wrist1082are connected to the end-effector1070, where the wrist1082is rotatable on second link1068by a bearing1084coupling the wrist1082to the second link1068. The first link1060and the second link1068may be coupled via bearings or rotary joint1086. The second link1068and the end-effector1070may be coupled through rotary joint1084. The end-effector1070may carry payload1088, for example, a semiconductor substrate or other suitable substrate or payload. The description of the substrate transport arm1014is merely an example. Features as described herein may be used with other types of substrate transport arms, and other types of robots.

Features as described herein generally relate to a hybrid motor and, more particularly, to a hybrid motor having ring magnets. Referring also toFIG. 3, there is shown a schematic plan view of an example hybrid motor10. The motor10may be one or both of the motors1034,1036for example. Although features will be described with reference to the embodiments shown in the drawings, it should be understood that the present invention may be embodied in many forms of alternative embodiments. In addition, any suitable size, shape or type of materials or elements could be used.

InFIG. 3, the hybrid motor10is shown having a stator12and a rotor14. The rotor14is shown having teeth20. The rotor14may be configured as a rotor of material, solid or otherwise, that may be a highly permeable material suitable for use in electric motors. Such material may be laminated, solid or formed of a soft magnetic composite (SMC) material or by any suitable method. By way of example, a suitable SMC material may be as described in US 2013/0004359 which is hereby incorporated by reference in its entirety. In alternate aspects, any suitable soft magnetic material or suitable material may be provided. In alternate aspects, more or less teeth may be provided or no teeth may be provided. As will be described, in this example embodiment the stator12has a solid core, for example stator cores22and24as will be described. Further, the stator12may have two or more ring magnets substantially disposed within the cores. Examples are described in alternate example configurations below. Further, the stator12may have one or more windings substantially disposed within the cores. Examples are described in alternate configurations below. In the embodiment shown, the stator12is shown having alternating claw poles26-36, each having teeth38. Thus, in this example the motor is a claw pole motor. In alternate aspects, more or less teeth may be provided or no teeth may be provided. Although six claw poles are shown, more or less than six claw poles may be provided.

Depending upon the direction of current in the winding, magnetic flux is selectively directed from one claw pole, through the rotor, and to an adjacent claw pole. Further, depending upon the direction of current in the winding, magnetic flux is selectively directed from different sides of a given stator (where the teeth may be phased with respect to an adjacent side) through the rotor and to the different sides as will be described.

The stator12may have multiple stator portions having different respective phases interacting with rotor14as will be shown by way of the examples below. In this example embodiment, two or more stator portions with windings may be stacked and phased to interact with the rotor14. In alternate aspects, multiple windings, for example, two or more, may be segmented within a single stator (as will be described with respect toFIG. 4by way of example). Further, in alternate aspects, instead of claw poles, stacked (axially, radially or otherwise) stator solid rotor portions may interact with rotor14, for example, two or more, as will be described with respect toFIG. 4by way of example. Accordingly, all such combinations may be provided either alone or in combination.

InFIG. 4, hybrid motor10′ is shown having stator12′ and rotor14. Rotor14is shown having teeth20and may be configured as a rotor such as shown inFIG. 3. As will be described, stator12′ has a solid core of one or more components, stacked or otherwise. Further, stator12′ may have two or more ring magnets substantially disposed within the cores as will be described in alternate configurations. Further, stator12′ may have one or more windings substantially disposed within the cores as will be described in alternate configurations. In the embodiment shown, stator12′ is shown having two sets of teeth52,54corresponding to embedded windings56,58respectively. In alternate aspects, more or less teeth may be provided or no teeth may be provided. Although two windings are shown, more or less windings may be provided. In this example the two sets of teeth52,54are 90 degrees different (compare the alignment of the teeth52relative to the rotor teeth20at the bottom of the figure versus the alignment of the teeth54relative to the rotor teeth20at the top of the figure. Thus, the motor may have a single stack of the two windings56,58at the stator, and provide a 2-phase device. Thus, two stacks of windings, such as shown inFIGS. 5-6for example, are not necessary.

Depending upon the direction of current in the winding56,58, magnetic flux may be selectively directed from different sides of a given stator (where the teeth may be phased with respect to an adjacent side) and selectively directed from different segments of a given stator (corresponding to windings56,58and respectively phased teeth52,54) through the rotor and to the different sides and segments. Although two segments are shown, more or less may be provided. Stator12′ may have multiple stator portions having different respective phases interacting with rotor14′ as will be shown by way of example. In this example embodiment, two or more stator portions with windings may be stacked and phased to interact with rotor14′ and/or multiple windings, for example, two or more, may be segmented within a single stator. Further, in alternate aspects, combinations of axially, radially or otherwise stator solid rotor portions may interact with rotor14, for example, two or more. Accordingly, all such combinations may be provided either alone or in combination.

InFIG. 5, an exemplary hybrid claw pole stepping motor100is shown. Although a two phase example is shown, alternately any suitable number of phases (such as three or more) may be provided. Solid rotor102has equally spaced teeth that direct between stator members110,112. In this example embodiment, stator members110,112may be similar and phased with respect to each other as shown. Stator member110has inner toothed member114and outer toothed members116,118. In this example embodiment, outer toothed members116,118may be phased 0 and 180 degrees with respect to the teeth on rotor102and where inner member114has two sets of teeth similarly phased to correspond to those on outer members116,118. Similarly stator member112has teeth phased at 90 and 270 degrees respectively. Stator member110further has winding124that may be wound similar to a bobbin with radially magnetized ring permanent magnets126,128.

Depending upon the magnitude and direction of current in winding124, flux is selectively directed in the direction of stator portion116and118, and through the teeth on rotor102, and back through the teeth on inner portion114of stator110similar to the Flux arrows F shown inFIG. 3for a claw pole motor. In this example embodiment, flux may selectively be directed between teeth on two inner stator members and teeth on the four outer stator members. In this example embodiment, the outer stator members may be substantially identical (and may be separate or integrally formed) with claw poles while the inner stator members have two interleaved and opposing sets of claw poles having teeth 180 degrees out of phase as shown. In this example embodiment, each outer stator member may be phased 90 and 180 degrees with respect to the others as shown where a simple coil winding is provided for each stator set as shown and having two ring magnets that direct flux in the same direction. Energizing each winding either positively or negatively selectively directs flux to one or the other outer stator for each of the two phases.

Alternately, two or more segments may be provided, for example as seen inFIG. 4with additional ring magnets to selectively direct flux through rotor102. Alternately, any suitable combination may be provided. In alternate aspects, more or less teeth or no teeth may be provided, additional or less claw poles, two sided solid rotor or other modifications such as further overlapping tooth structure or otherwise may be provided. Further, two or three phases may be placed in a single stack with 180 degree or 120 degree winding sets respectively. Claw poles need not be used in the event of offset poles. A combination of radial or axial flux paths may be provided. Accordingly, all such combinations may be provided.

InFIG. 6, an exemplary hybrid motor200is shown. Although a two phase example is shown, alternately any suitable number of phases (such as three or more) may be provided. In this example, the teeth of the stator and the rotor are similar to that shown with the teeth20,52,54inFIG. 4. Solid rotor202has equally spaced teeth that direct between stator members210,212. In this example embodiment, stator members210,212may be similar and phased with respect to each other as shown. Stator member210has inner toothed member214and outer toothed members216,218. In this example embodiment, outer toothed members216,218may be phased 0 and 180 degrees with respect to the teeth on rotor202and where inner member214has two sets of teeth similarly phased to correspond to those on outer members216,218. Similarly stator member212has teeth phased at 90 and 270 degrees respectively. Stator member210further has winding224that may be wound similar to a bobbin with radially magnetized ring permanent magnets226,228.

Depending upon the magnitude and direction of current in winding224, flux is selectively directed in the direction of either of stator portion216and218and through the teeth on rotor202and back through the teeth on inner portion214of stator210. In this example embodiment, flux may selectively be directed between teeth on two inner stator members and teeth on four outer stator members. In this example embodiment, the outer stator members may be substantially identical (and may be separate or integrally formed) having teeth 180 degrees out of phase as shown. In this example embodiment, each outer stator member may be phased 90 and 180 degrees with respect to the others as shown where a simple coil winding is provided for each stator set as shown and having two ring magnets that direct flux in the same direction. This is illustrated inFIGS. 6A and 6Bfor example.

As illustrated inFIG. 6A, when the coil or winding224is energized in a first direction, flux F+ flows in the direction of the top stator portion218, through the teeth on rotor202, and back through the teeth on inner portion214. As illustrated inFIG. 6B, when the coil or winding224is energized in a second different direction, flux F− flows in the direction of the bottom stator portion216, through the teeth on rotor202, and back through the teeth on inner portion214. In one type of alternate example embodiment, the teeth of the rotor and/or stator could comprise a combination of different types of teeth, such as the axially longer height claw pole teeth shown inFIG. 3, and the axially shorter height teeth shown inFIG. 4.

Energizing each winding either positively or negatively selectively directs flux to one or the other outer stator for each of the two phases. Alternately, two or more segments may be provided, for example as seen inFIG. 4with additional ring magnets and/or windings to selectively direct flux through rotor202. Alternately, any suitable combination may be provided. In alternate aspects, more or less teeth or no teeth may be provided, with claw poles, two sided solid rotor or other modifications such as overlapping tooth structure or otherwise may be provided. Further, two or three phases may be placed in a single stack with 180 degree or 120 degree winding sets respectively. Claw poles need not be used in the event of offset poles as seen. A combination of radial or axial flux paths may be provided. Although the permanent magnets are shown with radial flux in the same direction, opposite directions for all or a subset of the magnets may be provided. Accordingly, all such combinations may be provided with respect to any of the disclosed embodiments.

InFIG. 7, an exemplary axial flux hybrid motor300is shown. Although a two phase example is shown, alternately any suitable number of phases (such as three or more) may be provided. Solid rotor302has axially opposing equally spaced teeth304that direct flux between opposing axial sides of stator members310,312. In this example embodiment, stator members310,312may be similar and phased with respect to each other as shown (either by relative position of the stators teeth or by relative position of the rotors teeth304or a combination of the two). Stator member310has toothed members316,318. In this example embodiment, axially opposing sides of toothed members316,318may be phased 0 and 180 degrees with respect to the teeth on rotor302(or opposing teeth304on rotor may instead be so phased). Similarly stator member312may have teeth phased at 90 and 270 degrees respectively. Stator member310further has winding324that may be wound similar to a bobbin with radially magnetized ring permanent magnets326,328.

Depending upon the magnitude and direction of current in winding324, flux is selectively directed in the direction of either of magnets326,328and through the teeth on rotor302and linked with stator portions316,318. In this example embodiment, flux may selectively be directed to opposing teeth on the four stator members. Energizing each winding either positively or negatively selectively directs flux to one opposing side of the stator members for each of the two phases. Alternately, two or more segments may be provided, for example as seen inFIG. 2with additional ring magnets and/or windings to selectively direct flux through rotor302. Alternately, any suitable combination may be provided. In alternate aspects, more or less teeth or no teeth may be provided, with claw poles, two sided solid rotor or other modifications such as overlapping tooth structure or otherwise may be provided. Further, two or three phases may be placed in a single stack with 180 degree or 120 degree winding sets respectively. Claw poles need not be used in the event of offset poles as seen. A combination of radial or axial flux paths may be provided. Although the permanent magnets are shown with radial flux in the same direction, opposite directions for all or a subset of the magnets may be provided. Accordingly, all such combinations may be provided with respect to any of the disclosed embodiments.

InFIG. 8, an exemplary radial flux hybrid motor400is shown. Although a two phase example is shown, alternately any suitable number of phases (such as three or more for example) may be provided. Solid rotor402has radially opposing equally spaced teeth404that direct flux between opposing radial sides of stator members410,412. In this example embodiment, stator members410,412may be similar and phased with respect to each other as shown (either by relative position of the stators teeth or by relative position of the rotors teeth404or a combination of the two). Alternately, and with respect to the disclosed embodiments, any suitable combination of phasing may be used. Stator member410has toothed members416,418. In this example embodiment, radially opposing sides of toothed members416,418may be phased 0 and 180 degrees with respect to the teeth on rotor402(or opposing teeth404on rotor may instead be so phased). Similarly stator member412may have teeth phased at 90 and 270 degrees respectively. Stator member410further has winding424that may be wound similar to a bobbin with axially magnetized ring permanent magnets426,428. Alternately, windings may be segmented and teeth phased, for example, similar to that ofFIG. 2(or inFIG. 9with the coil orientation rotated 90 degrees) where each side of the view shown inFIG. 8has a single winding wound such that the two middle stator components form a core and the upper and lower stator components are separate.

Depending upon the magnitude and direction of current in winding424, flux is selectively radially directed in the direction of either of magnets426,428and through the teeth on rotor402and linked with stator portions416,418. In this example embodiment, flux may selectively be directed to opposing teeth on the four stator members. Energizing each winding either positively or negatively selectively directs flux to one opposing side of the stator members for each of the two phases. Alternately, two or more segments may be provided, for example as seen inFIG. 4with additional ring magnets and/or windings to selectively direct flux through rotor402. Alternately, any suitable combination may be provided. In alternate aspects, more or less teeth or no teeth may be provided, with claw poles, two sided solid rotor or other modifications such as overlapping tooth structure or otherwise may be provided. Further, two or three phases may be placed in a single stack with 180 degree or 120 degree winding sets respectively. Claw poles need not be used in the event of offset poles as seen. A combination of radial or axial flux paths may be provided. Although the permanent magnets are shown with axial flux in the same direction, opposite directions for all or a subset of the magnets may be provided. Accordingly, all such combinations may be provided with respect to any of the disclosed embodiments.

InFIG. 9, an exemplary axial flux hybrid motor500is shown. Although a two phase example is shown, alternately any suitable number of phases3,4or otherwise may be provided. Solid rotor502has equally spaced axially opposing teeth504that direct flux between stator members510,512. In this example embodiment, stator members510,512may be similar and phased with respect to each other as shown. Stator member510has inner toothed member514and outer toothed members516,518where outer toothed members516,518are radially surrounding member514as shown. In this example embodiment, axially opposing sides of outer toothed members516,518may be phased 0 and 180 degrees with respect to the teeth on rotor502and where inner member514has two sets of axially opposing teeth similarly phased to correspond to those on axially opposing sides of outer members516,518. Similarly stator member512has teeth phased at 90 and 270 degrees respectively. Stator member510further has winding524that may be wound similar as seen inFIG. 4with radially magnetized ring permanent magnets526,528.

Depending upon the magnitude and direction of current in winding524, flux is selectively directed axially to one axial side or the other axial side with respect to stator portions516and518and through the teeth on rotor502and back through the teeth on inner portion514of stator510. In this example embodiment, flux may selectively be directed between teeth on two inner stator members and teeth on four outer stator members of stators510,512. Alternately, two or more segments may be provided with additional ring magnets and/or windings to selectively direct flux through rotor502. Alternately, any suitable combination may be provided. In alternate aspects, more or less teeth or no teeth may be provided, with claw poles, two sided solid rotor or other modifications such as overlapping tooth structure or otherwise may be provided. Further, two or three phases may be placed in a single stack with 180 degree or 120 degree winding sets respectively. Claw poles need not be used in the event of offset poles as seen. A combination of radial or axial flux paths may be provided. Although the permanent magnets are shown with radial flux in the same direction, opposite directions for all or a subset of the magnets may be provided. Accordingly, all such combinations may be provided with respect to any of the disclosed embodiments.

In one example embodiment a multi-phase motor comprises a rotor; and a stator comprising at least one core, where the stator comprises a plurality of phase sections, where each phase section is configured to provide a phase of the multi-phase motor, where each phase section comprises at least one of the core(s), at least two ring magnets having polarity facing in a substantially same direction, and a winding between the at least two ring magnets, where the winding is configured to be energized to direct flux through the at least one core at a first portion associated with a first one of the ring magnets and to be differently energized to direct flux through the at least one core at a second portion associated with a second one of the ring magnets.

The at least one core may comprise a soft magnetic composite (SMC) material. The stator may comprise first and second stator members, where the each stator member comprises an inner toothed member and two outer toothed members. Teeth of the outer toothed members of the first stator member may be phased zero (0) degrees and 180 degrees relative to teeth on the rotor. Teeth of the outer toothed members of the second stator member may be phased 90 degrees and 270 degrees relative to teeth on the rotor. The inner toothed member of the first stator member may comprise two sets of teeth, where each set of teeth are phased to correspond to one of the phases of the teeth of the outer toothed members of the first stator member. The ring magnets may be permanent radially magnetized ring magnets. A first phase section may comprise inner and outer stator members, where the each stator member comprises a top toothed section and a bottom toothed section. A first phase section may comprise top and bottom stator members, where the each stator member comprises an inner toothed section and an outer toothed section. A first phase section may comprise a first stator member and a second stator member, where a second phase section comprises the second stator member and a third stator member, and where the each stator member comprises a top toothed section and a bottom toothed section.

One type of example method of assembly comprises locating a winding between two ring magnets to form an assembly, where the ring magnets have polarity facing in a substantially same direction; locating a plurality of the winding and ring magnet assembly in at least one core to form a motor stator; and locating the motor stator around a rotor.

The method may further comprise energizing the winding in a first direction to direct flux through the at least one core at a first portion of the at least one core associated with a first one of the ring magnets and energizing the winding in a second opposite direction to direct flux through the at least one core at a second portion of the at least one core associated with a second one of the ring magnets. The method may further comprise providing the at least one core as a soft magnetic composite (SMC) material. Locating the plurality of the winding and ring magnet assembly may comprise forming first and second stator members, where the each stator member comprises an inner toothed member and two outer toothed members. Teeth of the outer toothed members of the first stator member may be provided phased zero (0) degrees and 180 degrees relative no teeth on the rotor. Teeth of the outer toothed members of the second stator member may be provided phased 90 degrees and 270 degrees relative to teeth on the rotor. The inner toothed member of the first stator member may be provided as two sets of teeth, where each set of teeth are phased to correspond to one of the phases of the teeth of the outer toothed members of the first stator member. The ring magnets may be provided as permanent radially magnetized ring magnets. The stator may be provided with a first phase section comprising inner and outer stator members, where the each stator member comprises a top toothed section and a bottom toothed section.

An example embodiment may comprise a substrate transport apparatus comprising a substrate transport arm; and a drive connected to the substrate transport arm, where the drive comprises a multi-phase motor, where the motor comprises a rotor and a stator, where the stator comprises phase sections each including a core, two ring permanent magnets having polarity facing in a substantially same direction, and a winding between the two magnets, where the winding is configured to be energized to direct flux through a first portion of the core associated with a first one of the magnets and to be differently energized to direct flux through a second portion of the core associated with a second one of the magnets.