Abstract:
A wireless linear motor comprising: a stationary stator having permanent magnets; a movable stage having coils and a controller with a transceiver for wirelessly communicating with an external data processing system, the controller adapted to energize the coils to position the stage over the stator in response to control signals from the external system; and, a frame having first and second electrically conductive linear guides for slideably mounting the stage over the stator, wherein each linear guide has a stage portion attached to the stage through a first electrical insulator, a frame portion attached to the frame through a second electrical insulator, a plurality of ball bearings disposed between and electrically coupling the stage and frame portions, and a conductor coupling the stage portion to the controller for providing electrical power from an external power supply to the controller through the frame portion of each guide.

Description:
[0001]    This application claims priority from Canadian Patent Application No. 2,422,341, filed Mar. 17, 2003, and incorporated herein by reference.  
         FIELD OF THE INVENTION  
         [0002]    The invention relates to the field of linear motors, and more specifically to linear motors without power or control wiring between stator and movable stage.  
         BACKGROUND OF THE INVENTION  
         [0003]    Linear motors having stationary armatures containing coils and movable stages containing magnets are well known in the art. Also known are linear motors having stationary magnets and moving coils. One type of such linear motors is disclosed in U.S. Pat. No. 4,749,921 to Chitayat. The linear motor disclosed in this patent has a series of armature windings mounted to a base plate and a stage having a series of magnets that is free to move on the base plate. The stage is urged in the desired direction by applying AC or DC excitation to the coils. When such a linear motor is used in a positioning system, the relationship between the location of the stage and locations of the coils must be accounted for. In another linear motor, commutator contacts are pendant from the stage. The contacts contact one or more power rails, and one or more coil contacts. As the stage moves along the armature, the location of the stage, relative to the armature is automatically accounted for by applying power to the stationary armature windings through the commutator contacts. In yet other linear motors, it is conventional to employ a service loop of wires between the moving stage and the stationary elements.  
           [0004]    Typically, the location of the stage is updated using a magnetic or optical position encoder on the stage which senses markings on an encoder tape stationary alongside the path of the stage. The location is transferred by the service loop to a stationary motor controller. Generally, the important location information is the phase of the stage relative to the phase of the armature. For example, in a three-phase armature, the windings are disposed in repeating sets of three for phases U, V and W. If the center of the U phase winding is arbitrarily defined as 0 degrees, then the centers of the V and W windings are defined as 120 and 240 degrees. There may be two, three or more sets of windings as required for the travel distance of the stage. Normally, all U phase windings are connected in parallel. The same is true of all V and W phase windings. Thus, when the location of the stage requires a certain voltage configuration on the particular windings within the influence of the magnets on the stage, besides powering these windings, all of the other windings in the armature are also powered. The maximum force obtainable from a linear motor is limited by the allowable temperature rise in the armature windings. When all windings are powered, whether they contribute to motor force or not, more armature heating occurs than is strictly necessary for performing the motor functions. Some linear motors in the prior art have responded to this heating problem using switches that are closed only to the armature windings actually within the influence of the magnets.  
           [0005]    For reference, FIG. 1 is a side view of a linear motor  100  in accordance with the prior art. The linear motor  100  includes a stage (or mover)  110  and a stator  120 . The stage (here, the armature)  110  includes coils  130  and the stator (here, the field)  120  includes magnets  140 . The linear motor  100  is controlled by an external driver/controller  150  that is connected to the linear motor  100  by umbilical wires  190 . The umbilical wires  190  include: three wires for U, V, and W signals  160  from the stage  110 ; five wires for power, ground, and U, V and W signals from the Hall Effect sensor  170 ; and, five wires for power, ground, and A, B and Z signals from the position sensor  180  on the stage  110 . The Hall Effect sensor  170  is used for detecting magnetic poles for commutation purposes.  
           [0006]    Now, linear motors are increasingly being employed in manufacturing equipment. In such equipment, nominal increases in the speed of operation translate into significant savings in the cost of production. It is particularly desirable to produce as much force and acceleration as possible in a given linear motor. An increase in force generated requires either an increase in magnetic field intensity or an increase in current applied to coils of the armature. In a permanent magnet linear motor, the available magnetic field intensity is limited by the field strength of available motor magnets. Power dissipated in the coils increases at a rate equal the square of the current. Attendant heat generation limits the force that may be achieved without exceeding the maximum armature temperature. Therefore, improvements in the power dissipation capacity of linear motors provide for increases in their utility.  
           [0007]    In typical manufacturing equipment, a linear motor may be employed for driving a positioning table along an axis. For example, positioning tables are commonly used for moving a work object such as an electronic device in a precise path for performing an operation or inspection on the work object. Desirable characteristics of such positioning tables include precision, compactness, the maximum speed at which the table can be driven and the accuracy with which the table may be positioned. U.S. Pat. No. 4,151,447 to von der Heide, et al., discloses a linear DC motor having rows of pairs of vertically standing permanent magnets between which flat coils are arranged to travel. The polarity of DC power to the flat coils is switched by a magnetic field or electro-optical sensor at predetermined points in the travel of the flat coils. The apparatus in this patent employs trailing cables for feeding power to the coils.  
           [0008]    U.S. Pat. No. 4,761,573 to Chitayat discloses a linear DC motor suitable for driving a positioning table. This linear DC motor includes a linear toothed structure including coils wound around the individual teeth to form a repeating line pattern of electrically produced magnetic poles facing a corresponding parallel array of magnets arranged with alternating magnetic polarity having their broad faces closest to the toothed assembly. A brush assembly is provided on the movable element for contacting a linear slip ring assembly on the stationary element for switching the polarity of voltage applied to energizing coils of the motor. Linear power pickup rails are used in conjunction with brushes and linear slip rings for feeding and controlling power to energizing coils. Furthermore, a brush and power pickup brush assembly is disclosed for feeding first and second electrical polarities to energizing coils which employs two identical comb-like structures for both picking up power from linear power pickup rails and for feeding power to the coils through a linear slip ring.  
           [0009]    Another brush and rail power pick-up arrangement is disclosed in U.S. Pat. No. 4,789,815 to Kobayashi, et al. This patent discloses a movable stage having control and driver means for supplying electric power to coils in the movable stage. The electric power is delivered to the control and driver means through brushes which make contact with rails mounted on the frame. The direction and position of the movable stage are controlled through the supply of power to the rails (i.e. on, off, and polarity). The linear motor thus disclosed is directed toward the control of curtains in vehicles.  
           [0010]    Thus, there is a growing commercial use of high performance, linear motors in various manufacturing and other applications. One recognized disadvantage of prior art linear motors is the cumbersome umbilical wires that connect the moving armature or stage to the controller and power source. For example, the umbilical for a prior art three-phase, brushless motor may have three power lines, five signal lines for the armature commutating signals, and eight signal lines for armature position signals. The need for a cable loop connecting moving and stationary elements is inconvenient and limits the flexibility with which a system can be designed. The wiring harness requires additional clearance from the linear motor to prevent entanglement between the motor and any equipment or items that may be adjacent to the linear motor path. In addition, the wiring harness adds additional weight to the moving element of the linear motor. Furthermore, manufacturing of a linear motor employing a wiring harness incurs additional cost of material and assembly labour. Therefore, it would be desirable to eliminate the use of a wiring harness in a linear motor to decrease the cost of assembly, decrease the overall weight of the moving element, and to eliminate the clearance restrictions on the linear motor&#39;s utility. Another recognized disadvantage is the need to remove heat from the moving stage (i.e. armature). Where a coolant is used, the umbilical includes, in addition to the wires, a tube to carry the coolant to a coolant coil embedded in the armature and a tube to carry the coolant from the coil. The result is a heavy, cumbersome, umbilical of wires and tubes, festooned along the path over which the stage moves.  
           [0011]    To overcome some of these disadvantages, wireless or semi-wireless linear motors have been developed and have been disclosed, for example, in U.S. Pat. Nos. 5,936,319 to Chitayat and 6,005,310 to Mosciatti, et al. U.S. Pat. No. 5,936,319 discloses a communications device on a movable stage which wirelessly informs a motor controller about the position and/or incremental motion of the movable stage. The movable stage includes a position encoder and any wireless transmission system may be used including radio and infrared. However, the movable stage includes permanent magnets while the fixed path includes armature coils. U.S. Pat. No. 6,005,310 discloses a movable stage with a wireless transmitter (e.g. radio frequency or infrared) for transmitting commutating and position signals to an external motor controller. However, while the movable stage includes coils, the motor controller is connected to the movable stage by an umbilical cord.  
           [0012]    A need therefore exists for an improved wireless linear motor which overcomes at least some of the drawbacks of the prior art. Accordingly, it is an object of the present invention to provide such a linear motor.  
         SUMMARY OF THE INVENTION  
         [0013]    According to one aspect of the invention, there is provided a wireless linear motor comprising: a stationary stator having permanent magnets; a movable stage having coils and a controller with a transceiver for wirelessly communicating with an external data processing system, the controller adapted to energize the coils to position the stage over the stator in response to control signals from the external system; and, a frame having first and second electrically conductive linear guides for slideably mounting the stage over the stator, wherein each linear guide has a stage portion attached to the stage through a first electrical insulator, a frame portion attached to the frame through a second electrical insulator, a plurality of ball bearings disposed between and electrically coupling the stage and frame portions, and a conductor coupling the stage portion to the controller for providing electrical power from an external power supply to the controller through the frame portion of each guide.  
           [0014]    Preferably, the stator is incorporated in the frame. Preferably, a linear recess is defined in the stage portion for receiving the frame portion. Preferably, the wireless linear motor further includes position sensors coupled to the controller for providing position signals for the stage to the external system for generating the control signals. Preferably, the wireless linear motor further includes magnetic sensors mounted on the stage and coupled to the controller for providing magnetic pole signals indicative of the location of the stage relative to the permanent magnets of the stator. Preferably, the magnetic sensors are Hall Effect sensors. Preferably, the wireless linear motor further includes a battery mounted on the stage and coupled to the controller for delivering supplemental power to the controller.  
           [0015]    According to another aspect of the invention, there is provided a wireless linear motor comprising: a stationary stator having permanent magnets; a movable stage having coils and a controller with a transceiver for wirelessly communicating with an external data processing system, the controller adapted to energize the coils to position the stage over the stator in response to control signals from the external system; and, a frame having first and second magnetically permeable linear guides for slideably mounting the stage over the stator to form a magnetic circuit linking the frame and stage, wherein each linear guide has a stage portion attached to the stage and wound with a stage coil, a frame portion attached to the frame and wound with a frame coil, a plurality of ball bearings disposed between and magnetically coupling the stage and frame portions, electric conductors coupling the frame coil to an external power supply for generating a magnetic flux in the frame portion, and electric conductors coupling the stage coil to the controller for providing electrical power induced in the stage coil by the magnetic flux.  
           [0016]    Preferably, the stator is incorporated in the frame. Preferably, a linear recess is defined in the stage portion for receiving the frame portion. Preferably, the wireless linear motor further includes position sensors coupled to the controller for providing position signals for the stage to the external system for generating the control signals. Preferably, the wireless linear motor further includes magnetic sensors mounted on the stage and coupled to the controller for providing magnetic pole signals indicative of the location of the stage relative to the permanent magnets of the stator. Preferably, the magnetic sensors are Hall Effect sensors. Preferably, the wireless linear motor further includes a battery mounted on the stage and coupled to the controller for delivering supplemental power to the controller.  
           [0017]    According to another aspect of the invention, there is provided a wireless linear motor comprising: a stationary stator having permanent magnets; a movable stage having coils and a controller with a transceiver for wirelessly communicating with an external data processing system, the controller adapted to energize the coils to position the stage over the stator in response to control signals from the external system; and, a frame having first and second electrically conductive linear guides for slideably mounting the stage over the stator, wherein each linear guide has a stage portion attached to the stage through a first electrical insulator, a frame portion attached to the frame through a second electrical insulator, a plurality of ball bearings disposed between and electrically coupling the stage and frame portions, a brush mounted on the stage portion and contacting the frame portion, and a conductor coupling the brush to the controller for providing electrical power from an external power supply to the controller through the frame portion of each guide.  
           [0018]    Preferably, the stator is incorporated in the frame. Preferably, a linear recess is defined in the stage portion for receiving the frame portion. Preferably, the wireless linear motor further includes position sensors coupled to the controller for providing position signals for the stage to the external system for generating the control signals. Preferably, the wireless linear motor further includes magnetic sensors mounted on the stage and coupled to the controller for providing magnetic pole signals indicative of the location of the stage relative to the permanent magnets of the stator. Preferably, the magnetic sensors are Hall Effect sensors. Preferably, the wireless linear motor further includes a battery mounted on the stage and coupled to the controller for delivering supplemental power to the controller. Preferably, the brush is spring mounted on the stage.  
           [0019]    According to another aspect of the invention, there is provided a power supply circuit for a linear motor, the motor having a stationary stator including permanent magnets, a movable stage including coils and a controller for communicating with an external data processing system and adapted to energize the coils to position the movable stage over the stationary stator in response to control signals from the external system, the circuit comprising: first and second electrically conductive linear guides mounted on a frame and for slideably mounting the stage over the stator, wherein each linear guide has a stage portion attached to the stage through a first electrical insulator, a frame portion attached to the frame through a second electrical insulator, a plurality of ball bearings disposed between and electrically coupling the stage and frame portions, and a conductor coupling the stage portion to the controller for providing electrical power from an external power supply to the controller through the frame portion of each guide. Preferably, the power supply circuit further includes a battery mounted on the stage and coupled to the controller for delivering supplemental power to the controller.  
           [0020]    According to another aspect of the invention, there is provided a power supply circuit for a linear motor, the motor having a stationary stator including permanent magnets, a movable stage including coils and a controller for communicating with an external data processing system and adapted to energize the coils to position the movable stage over the stationary stator in response to control signals from the external system, the circuit comprising: first and second magnetically permeable linear guides mounted on a frame and for slideably mounting the stage over the stator to form a magnetic circuit linking the frame and stage, wherein each linear guide has a stage portion attached to the stage and wound with a stage coil, a frame portion attached to the frame and wound with a frame coil, a plurality of ball bearings disposed between and magnetically coupling the stage and frame portions, electric conductors coupling the frame coil to an external power supply for generating a magnetic flux in the frame portion, and electric conductors coupling the stage coil to the controller for providing electrical power induced in the stage coil by the magnetic flux. Preferably, the power supply circuit further includes a battery mounted on the stage and coupled to the controller for delivering supplemental power to the controller.  
           [0021]    According to another aspect of the invention, there is provided a power supply circuit for a linear motor, the motor having a stationary stator including permanent magnets, a movable stage including coils and a controller for communicating with an external data processing system and adapted to energize the coils to position the movable stage over the stationary stator in response to control signals from the external system, the circuit comprising: first and second electrically conductive linear guides mounted on a frame and for slideably mounting the stage over the stator, wherein each linear guide has a stage portion attached to the stage through a first electrical insulator, a frame portion attached to the frame through a second electrical insulator, a plurality of ball bearings disposed between and electrically coupling the stage and frame portions, a brush mounted on the stage portion and contacting the frame portion, and a conductor coupling the brush to the controller for providing electrical power from an external power supply to the controller through the frame portion of each guide. Preferably, the brush is spring mounted on the stage. Preferably, the power supply circuit further includes a battery mounted on the stage and coupled to the controller for delivering supplemental power to the controller.  
           [0022]    Advantageously, no umbilical wires are used to connect the stage or controller to the frame or data processing system. In addition, the linear guides facilitate effective heat dissipation from the stage while providing improved power transfer to the stage. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]    Embodiments of the invention may best be understood by referring to the following description and accompanying drawings. In the description and drawings, like numerals refer to like structures or processes. In the drawings:  
         [0024]    [0024]FIG. 1 is a side view of a linear motor in accordance with the prior art;  
         [0025]    [0025]FIG. 2 is a side view of an integrated linear motor in accordance with an embodiment of the invention;  
         [0026]    [0026]FIG. 3 is a block diagram illustrating an exemplary data processing system adapted for implementing an embodiment of the invention;  
         [0027]    [0027]FIG. 4 is a schematic diagram illustrating a linear motor having its driver/controller powered through brushes and collector rails in accordance with an embodiment of the invention;  
         [0028]    [0028]FIG. 5 is a front view of a linear motor having its driver/controller powered through insulated linear guides in accordance with an embodiment of the invention;  
         [0029]    [0029]FIG. 6A is a front view of a linear motor having its driver/controller powered by magnetic induction in accordance with an embodiment of the invention; and,  
         [0030]    [0030]FIG. 6B is a perspective view of the coils and cores for use in the embodiment of FIG. 6A in accordance with an embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    In the following description, numerous specific details are set forth to provide a thorough understanding of the invention. However, it is understood that the invention may be practiced without these specific details. In other instances, well-known software, circuits, structures and techniques have not been described or shown in detail in order not to obscure the invention. The term “data processing system” is used herein to refer to any machine for processing data, including the computer systems and network arrangements described herein.  
         [0032]    [0032]FIG. 2 is a side view of an integrated linear motor  200  in accordance with an embodiment of the invention. The integrated linear motor  200  includes a stage  210  slideably mounted over a stator  220 . The stage  210  includes coils  230  and the stator  220  includes permanent magnets  240 . The stage  210  is adapted to move back and forth over the stator  220  which may be incorporated in or form a frame  220  for the motor  200 . The stage  210  is mechanically supported on the frame  220  by linear guides  510 ,  520  (see FIG. 5). The stage  210  may also be supported on the frame  220  by similar structures.  
         [0033]    The linear motor  200  is controlled by a driver/controller  250  that is mounted on the stage  210 . The driver/controller  250  includes a central processing unit or CPU, memory, a transceiver or transceiver interface, and I/O interfaces. The CPU may include dedicated coprocessors and memory devices. The memory may include RAM, ROM, databases, or disk devices. The transceiver or transceiver interface may include radio frequency, infrared, and power-line carrier transceivers or transceiver interfaces, respectively. And, the I/O interfaces may include interfaces for sensor inputs and coil outputs. In addition, the drive/controller  250  may support detachable input and display devices. The detachable input device may include a keyboard, mouse, trackball, or similar device. The detachable display may include a computer screen or terminal device. The driver/controller  250  has stored therein data representing sequences of instructions which when executed cause the operations described herein to be performed. Of course, the driver/controller  250  may contain additional software and hardware a description of which is not necessary for understanding the invention.  
         [0034]    The drive/controller  250  is in wireless data communication with a remote data processing system  300  (see FIG. 3). This wireless data communication is supported by a first transceiver  290  mounted on the stage  210  and coupled to or incorporated in the driver/controller  250  and a second transceiver  350  (see FIG. 3) associated with the data processing system  300 . The transceivers can include radio frequency (“RF”), infrared (“IR”), and power-line carrier (high frequency modulation) transceivers and various communication protocols can be supported including the Bluetooth, wireless local area network (“LAN”), and asymmetric digital subscriber line (“ADSL”) protocols.  
         [0035]    [0035]FIG. 4 is a schematic diagram illustrating a linear motor  200  having its driver/controller  250  powered through brushes and collector rails in accordance with an embodiment of the invention. The driver/controller  250  receives electrical power from a power source  450  through power or collector rails  430 ,  440  mounted on the frame  220  which are in contact with brushes  410 ,  420  mounted on the stage  210 . The power or collector rails  430 ,  440  may be linear guides  510 ,  520  (see FIG. 5). To improve conductance, the brushes may be mounted on springs  460 ,  470 . On the stage  210 , power from the brushes  410 ,  420  is distributed to the driver/controller  250  and other stage mounted devices. Similarly, a collector ring arrangement (not shown) typical of subway trains and the like may be used to supply power to the stage  210 .  
         [0036]    [0036]FIG. 5 is a front view of a linear motor  200  having its driver/controller  250  powered through insulated linear guides  510 ,  520  in accordance with an embodiment of the invention. In this embodiment, the rail or frame portion  511 ,  521  of each linear guide  510 ,  520  is connected to the power source  450 . The rail or frame portion  511 ,  521  is generally insulated from the frame  220  by first insulators  530 ,  540 . The stage portion  512 ,  522  of each linear guide  510 ,  520  is connected to the stage  210  upon which is mounted the driver/controller  250 . The stage portion  512 ,  522  is generally insulated from the stage  210  by second insulators  550 ,  560 . The insulated linear guides  510 ,  520  function to both support and provide power to the stage  210 . Ball bearings  570 ,  580  provide the points of electrical contact between the rail or frame  511 ,  521  and stage  512 ,  522  portions of the linear guides  510 ,  520 .  
         [0037]    [0037]FIG. 6A is a front view of a linear motor  200  having its driver/controller  250  powered by magnetic induction in accordance with an embodiment of the invention; and, FIG. 6B is a perspective view of the coils  611 ,  621  and cores  610 ,  620  for use in the embodiment of FIG. 6A in accordance with an embodiment of the invention. In this embodiment, the stage  210  and frame  220  have associated coils  611 ,  621  wound on respective cores  610 ,  620 . The rail or frame coil  621  is connected to a power source  450 . When energized, the frame coil  621  causes a magnetic flux to link the stage core  610  and coil  611  and hence induce a voltage across the stage coil terminals. The stage coil terminals are connected to the driver/controller  250  and provide it with electric power. The stage and frame coils  611 ,  621  and cores  610 ,  620  may be integrated with the linear guides  510 ,  520  and/or stage  210  and frame  220 .  
         [0038]    According to another embodiment of the invention, the stage  210  may be powered by a rechargeable battery (not shown) alone or with a rechargeable battery in combination with one or more of the linear guide based power delivery means described above.  
         [0039]    Referring again to FIG. 2, the stage  210  generally includes a metal or cast resin armature plate (not shown) in which the armature coils  230  are embedded. For a three phase motor, typically six coils are used three of which are shown in FIG. 2, in a non-overlapping arrangement, but, as will be appreciated by those skilled in the art, they could be disposed in an overlapping position. The armature plate is formed with a suitable thermally conductive metal or resin. A heat sink (not shown), made of a suitable thermally conductive material (e.g. aluminium) is attached by a heat conductive epoxy to the armature plate. Thermally conductive pins (not shown) can be used to help conduct heat from the armature coils  230  to the heat sink and also help secure the heat sink to the armature plate. One or more fans (not shown) can be attached to the heat sink to move air across the heat sink to help cool it and thereby aid in heat transfer away from the armature coils  230 . The heat sink typically includes fins (not shown) to aid in heat removal by providing an additional surface area over which air may pass. The linear guides  510 ,  520  are also effective in transferring heat from the stage  210  to the frame  220  by conduction.  
         [0040]    Sensors  270  (e.g. Hall Effect sensors), attached to the stage  210 , generate commutating signals indicating the position of the armature coils  230  relative to the stator permanent magnets  240 . As will be appreciated by those skilled in the art, these commutating signals are used to control sequential switching of power to the armature coils  230  by the driver/controller  250 . In a three-phase embodiment of the invention, three commutation position sensors  270  (e.g. three Hall Effect sensors) may be used. In addition, an armature position encoding sensor  280  is attached to stage  210 . The armature position encoder  280  may be, for example, an optical encoder. The use of Hall Effect sensors  270  is optional.  
         [0041]    Commutation signals from the sensors  270  and armature position signals from the armature position encoder  280  are coupled to the driver/controller  250 . The armature position signals, which indicate the position of the stage  210 , and the commutation signals, are decoded as necessary by the driver/controller  250  and used to control the supply of power to the armature coils  230 . Alternatively or additionally, the armature position and commutation signals may be received by the driver/controller  250  and transmitted via the coupled stage mounted transceiver  290  to the data processing system  300 .  
         [0042]    [0042]FIG. 3 is a block diagram of an exemplary data processing system  300  adapted for implementing an embodiment of the invention. The data processing system is suitable for controlling and/or monitoring one or more integrated linear motors  200  in conjunction with a graphical user interface (“GUI”). The data processing system  300  includes an input device  310 , a central processing unit or CPU  320 , memory  330 , a display  340 , and a transceiver  350 . The input device  310  may include a keyboard, mouse, trackball, or similar device. The CPU  320  may include dedicated coprocessors and memory devices. The memory  330  may include RAM, ROM, databases, or disk devices. The display  340  may include a computer screen or terminal device. And, the transceiver  350  may include RF, IR, and power-line carrier transceivers. The data processing system  300  has stored therein data representing sequences of instructions which when executed cause the operations described herein to be performed. Of course, the data processing system  300  may contain additional software and hardware a description of which is not necessary for understanding the invention.  
         [0043]    In operation, the driver/controller  250  receives an instruction set from the data processing system  300  via the stage mounted transceiver  290  and data processing system transceiver  350 . The instruction set specifies the position or path the stage  210  is to move to or over, respectively. The driver/controller  250  receives position and commutation signals from the position and commutation sensors  270 ,  280 , respectively. From the received position signals, commutation signals, and instructions, the driver/controller  250  computes the drive signals to be provided to the armature coils  230  to complete the repositioning or movement specified by the instruction set. Using power provided by the frame mounted power rail, for example, the driver/controller  250  generates the necessary drive signals and provides these to the armature coils  230 . The driver/controller  250  continues to monitor the position and commutation sensors  270 ,  280  during movement of the stage  210 . After the stage  210  has been repositioned or moved in accordance with the instruction set, the driver/controller  250  reports instruction set completion and the new location of the stage  210  to the data processing system  300  and awaits a new instruction set. The driver/controller  210  may continually report stage position and other parameters (e.g. power consumption, temperature, etc.) to the data processing system  300  or these parameters may be reported upon request by the data processing system  300 .  
         [0044]    The sequences of instructions which when executed cause the operations described herein to be performed by the driver/controller  250  and/or data processing system  300  can be contained in a data carrier product according to an embodiment of the invention. This data carrier product can be loaded into and run by the driver/controller  250  and/or data processing system  300 . In addition, the sequences of instructions which when executed cause the operations described herein to be performed by the driver/controller  250  and/or data processing system  300  can be contained in a computer software product according to an embodiment of the invention. This computer software product can be loaded into and run by the driver/controller  250  and/or data processing system  300 . Furthermore, The sequences of instructions which when executed cause the operations described herein to be performed by the driver/controller  250  and/or data processing system  300  can be contained in an integrated circuit product including a coprocessor or memory according to an embodiment of the invention. This integrated circuit product can be installed in the driver/controller  250  and/or data processing system  300 .  
         [0045]    Advantageously, no umbilical wires  190  are used to connect the stage  210  or driver/controller  250  to the frame  220  or data processing system  300 . In addition, the linear guides  510 ,  520  facilitate effective heat dissipation from the stage  210  while providing improved power transfer to the stage  210 .  
         [0046]    Although preferred embodiments of the invention have been described herein, it will be understood by those skilled in the art that variations may be made thereto without departing from the spirit of the invention or the scope of the appended claims.