Patent Publication Number: US-2022216733-A1

Title: Method and System for Contactless Power Transfer in a Linear Drive System

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of and claims priority to U.S. application Ser. No. 16/794,520, filed Feb. 19, 2020, which, in turn, is a continuation of and claims priority to U.S. application Ser. No. 15/719,021, filed Sep. 28, 2017, which issued as U.S. Pat. No. 10,608,469 on Mar. 31, 2020, the entire contents of each referenced application is incorporated herein by reference. 
    
    
     BACKGROUND INFORMATION 
     The present invention relates to motion control systems and, more specifically, to power transfer to an independent mover as it travels along a track in a motion control system incorporating multiple movers propelled along the track using a linear drive system. 
     Motion control systems utilizing movers and linear motors can be used in a wide variety of processes (e.g. packaging, manufacturing, and machining) and can provide an advantage over conventional conveyor belt systems with enhanced flexibility, extremely high speed movement, and mechanical simplicity. The motion control system includes a set of independently controlled “movers” each supported on a track for motion along the track. The track is made up of a number of track segments, and a linear drive system controls operation of the movers, causing the movers to travel along the track. Sensors may be spaced at fixed positions along the track and/or on the movers to provide information about the position and speed of the movers. 
     Each of the movers may be independently moved and positioned along the track in response to an electromagnetic field generated by the linear drive system. In a typical system, the track forms a closed path over which each mover repeatedly travels. At certain positions along the track other actuators may interact with each mover. For example, the mover may be stopped at a loading station at which a first actuator places a product on the mover. The mover may then be moved along a process segment of the track where various other actuators may fill, machine, position, or otherwise interact with the product on the mover. The mover may be programmed to stop at various locations or to move at a controlled speed past each of the other actuators. After the various processes are performed, the mover may pass or stop at an unloading station at which the product is removed from the mover. The mover then completes a cycle along the closed path by returning to the loading station to receive another unit of the product. 
     In certain applications, it may be desirable to provide an actuator or a sensor on the mover to interact with the product on the mover. For example, a clamp may actuate to secure the product to the mover or a sensor may detect the presence of the product on the mover. However, the actuator or sensor requires an energy source to operate. For electric actuators or sensors, the energy source may be a battery. For a hydraulic or pneumatic actuator, the energy source may be a pressurized tank. The energy source adds weight and takes up space on the mover. Further, the energy source needs to be periodically recharged. 
     One solution for providing energy to a mover is to provide a dedicated location along the track at which the energy is supplied. The mover stops at the dedicated location where a temporary connection to an energy source may be established. A first actuator external to the mover may engage the mover and establish an electrical, pneumatic, or hydraulic connection to the mover. A second actuator on the mover may perform the desired task, and the first actuator supplying power may subsequently disengage from the mover. This process, however, requires the mover to come to a stop at the dedicated location, wait for power to be connected, perform the desired action, and wait for the power to be disconnected before resuming motion. The additional steps required to supply power reduce the throughput of the system and the dedicated locations limit the ability of actuators or sensors present on a mover to operate. 
     Thus, it would be desirable to provide an improved system for supplying power to independent movers on a track in a motion control system. 
     Another solution for providing energy to a mover is to provide a fixed connection to the mover. The fixed connection may be, for example, an electrical conductor or a hydraulic or pneumatic hose. A fixed connection, however, is not without certain drawbacks. The motion of the mover is typically restricted to limit the required length of the electrical conductor or hose. The number of movers must be limited and/or the motion of the mover is limited to a reciprocal motion to avoid tangling the conductors or hoses between movers. 
     Thus, it would be desirable to provide a method and apparatus for transmitting power to an independent mover as in travels along a track in a motion control system which eliminates a fixed connection between the mover and a power source. 
     Historically, the linear drive system has included multiple coils spaced along the track and magnets mounted to each of the movers. The magnets on the movers may include multiple magnet segments with alternating north and south poles oriented to face the track. Each pair of north and south poles corresponds to a pole pair in the linear drive system. The coils along the track are sequentially energized with an alternating current which establishes an electromagnetic field around the coil. The electromagnetic field interacts with the magnetic field generated by the pole pairs on the movers and is controlled to drive the movers along the track. This arrangement, however, requires power converters corresponding to the coils spaced along the track to control the current through each coil. The linear drive system may require twice as many power converters as movers present on the track and include a significant portion of idle time while no mover is present over a coil controlled by the power converter. 
     Thus, it would be desirable to provide a system for transmitting sufficient power to each mover to supply power to coils on the mover which, in turn, interact with magnets mounted along the track to control operation of each mover. 
     BRIEF DESCRIPTION 
     The subject matter disclosed herein describes a system and method for providing power to independent movers traveling along a track without requiring a fixed or removable connection to each mover. A power converter on the mover may regulate the power supplied to the mover to control an electrical device, such as an actuator or a sensor mounted on the mover. The power converter on the mover may also be configured to activate drive coils mounted on the mover to interact with magnets mounted along the track and, thereby, control motion of each mover. In one embodiment, a sliding transformer transfers power between the track and each mover. In another embodiment, an optical transmitter transfers power between the track and an optical receiver mounted on each mover. In yet another embodiment, a generator includes a drive wheel engaging the track as each mover travels along the track. A power converter on the mover receives the power generated on and/or transmitted to the mover to control an actuator or a sensor mounted on the mover or to activate drive coils mounted on the mover to interact with magnets mounted along the track and, thereby, control motion of each mover. 
     In one embodiment of the invention, a transport system includes a mover, a rail for guiding the mover, and a linear drive system for driving the mover along the rail. The linear drive system includes a stator and a rotor, where the stator is arranged along at least one track segment and the rotor is arranged on the mover. A system for contactless power transmission includes a single primary coil or multiple primary coils arranged along the at least one track segment, and a single secondary coil or multiple secondary coils arranged on the mover. The single or multiple secondary coils are configured to be inductively coupled to the single or multiple primary coils. A controller is configured to control a power converter for supplying power to the single or multiple primary coils for contactless power transmission via inductive coupling between the single or multiple primary coils and the single or multiple secondary coils. 
     According to one aspect of the invention, a method of operating the transport system includes controlling the power converter by the controller to provide a controlled AC voltage to at least one of the single or multiple primary coils and transmitting power without contact to the single or multiple secondary coils via inductive coupling from the single or multiple primary coils which are receiving the controlled AC voltage. 
     According to another embodiment of the invention, a contactless power transmission system for a linear drive system is disclosed. The linear drive system includes a stator and a rotor, where the stator is arranged along at least one track segment and the rotor is arranged on a mover configured to travel along the at least one track segment. The contactless power transmission system includes a single primary coil or multiple primary coils arranged along a length of the at least one track segment in a stationary manner, and a single secondary coil or multiple secondary coils arranged on the mover, where the single or multiple secondary coils are configured to be inductively coupled to the single or multiple primary coils. A controller is configured to control a power converter for supplying power to the single or multiple primary coils for contactless power transmission via inductive coupling between the single or multiple primary coils and the single or multiple secondary coils 
     These and other advantages and features of the invention will become apparent to those skilled in the art from the detailed description and the accompanying drawings. It should be understood, however, that the detailed description and accompanying drawings, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various exemplary embodiments of the subject matter disclosed herein are illustrated in the accompanying drawings in which like reference numerals represent like parts throughout, and in which: 
         FIG. 1  is an isometric view of an exemplary transport system incorporating multiple movers travelling along a closed curvilinear track according to one embodiment of the present invention; 
         FIG. 2  is a partial side elevation view of one segment of one embodiment of the transport system of  FIG. 1  illustrating activation coils distributed along one surface of the track segment; 
         FIG. 3  is an isometric view of a mover from the transport system of  FIG. 2 ; 
         FIG. 4  is a partial sectional view of the transport system of  FIG. 1 ; 
         FIG. 5  is an exemplary schematic representation of a sliding transformer incorporated into the transport system of  FIG. 4 ; 
         FIG. 6  is a block diagram representation of the mover illustrated in  FIG. 3 ; 
         FIG. 7  is a partial top plan view of a track segment illustrating a primary winding for one embodiment of a sliding transformer mounted along the track segment; 
         FIG. 8  is a partial sectional view of a mover illustrating a secondary winding for the sliding transformer of  FIG. 7  mounted along the lower surface of the top member of the mover; 
         FIG. 9  is a schematic representation of one embodiment of a power converter supplying power to a sliding transformer according to one embodiment of the present invention; 
         FIG. 10  is a schematic representation of one embodiment of a power converter mounted on the mover to regulate power from a sliding transformer according to one embodiment of the present invention; 
         FIG. 11  is a partial side elevation view of one segment of another embodiment of the transport system of  FIG. 1  illustrating driving magnets distributed along one surface of the track segment; 
         FIG. 12  is an isometric view of a mover from the transport system of  FIG. 11 ; 
         FIG. 13  is a block diagram representation of the mover illustrated in  FIG. 12 ; 
         FIG. 14  is a schematic representation of a motor drive mounted on the mover to regulate power from a sliding transformer to drive coils on the mover according to one embodiment of the invention; 
         FIG. 15  is a partial sectional view of another embodiment of the transport system; 
         FIG. 16  is a block diagram representation of one embodiment of the mover illustrated in  FIG. 15 ; 
         FIG. 17  is a block diagram representation of an embodiment of the mover including motor coils on the mover as used with the transport system illustrated in  FIG. 15 ; 
         FIG. 18  is a schematic representation of one embodiment of a power converter mounted on the mover to regulate power from a generator mounted on the mover according to one embodiment of the present invention; 
         FIG. 19  is a partial sectional view of another embodiment of the transport system; 
         FIG. 20  is a block diagram representation of one embodiment of the mover illustrated in  FIG. 19 ; 
         FIG. 21  is a block diagram representation of an embodiment of the mover including motor coils on the mover as used with the transport system illustrated in  FIG. 19 ; and 
         FIG. 22  is a schematic representation of one embodiment of a power converter mounted on the mover to regulate power from an optical transmitter according to one embodiment of the present invention. 
     
    
    
     In describing the various embodiments of the invention which are illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, it is not intended that the invention be limited to the specific terms so selected and it is understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. For example, the word “connected,” “attached,” or terms similar thereto are often used. They are not limited to direct connection but include connection through other elements where such connection is recognized as being equivalent by those skilled in the art. 
     DETAILED DESCRIPTION 
     The various features and advantageous details of the subject matter disclosed herein are explained more fully with reference to the non-limiting embodiments described in detail in the following description. 
     Turning initially to  FIG. 1 , an exemplary transport system for moving articles or products includes a track  10  made up of multiple segments  12 ,  14 . According to the illustrated embodiment, the segments define a generally closed loop supporting a set of movers  100  movable along the track  10 . The track  10  is oriented in a horizontal plane and supported above the ground by a base  15  extending vertically downward from the track  10 . According to the illustrated embodiment, the base  15  includes a pair of generally planar support plates  17 , located on opposite sides of the track  10 , with mounting feet  19  on each support plate  17  to secure the track  10  to a surface. The illustrated track  10  includes four straight segments  12 , with two straight segments  12  located along each side of the track and spaced apart from the other pair. The track  10  also includes four curved segments  14  where a pair of curved segments  14  is located at each end of the track  10  to connect the pairs of straight segments  12 . The four straight segments  12  and the four curved segments  14  form a generally oval track and define a closed surface over which each of the movers  100  may travel. It is understood that track segments of various sizes, lengths, and shapes may be connected together to form a track  10  without deviating from the scope of the invention. 
     For convenience, the horizontal orientation of the track  10  shown in  FIG. 1  will be discussed herein. Terms such as upper, lower, inner, and outer will be used with respect to the illustrated track orientation. These terms are relational with respect to the illustrated track and are not intended to be limiting. It is understood that the track may be installed in different orientations, such as sloped or vertical, and include different shaped segments including, but not limited to, straight segments, inward bends, outward bends, up slopes, down slopes and various combinations thereof. Further, each track segment  12 ,  14  is shown in a generally horizontal orientation. The track segments  12 ,  14  may also be oriented in a generally vertical orientation and the width of the track  10  may be greater in either the horizontal or vertical direction according to application requirements. The movers  100  will travel along the track and take various orientations according to the configuration of the track  10  and the relationships discussed herein may vary accordingly. 
     Each track segment  12 ,  14  includes a number of independently attached rails  20  on which each mover  100  runs. According to the illustrated embodiment, rails  20  extend generally along the outer periphery of the track  10 . A first rail  20  extends along an upper surface  11  of each segment and a second rail  20  extends along a lower surface  13  of each segment. It is contemplated that each rail  20  may be a singular, molded or extruded member or formed from multiple members. It is also contemplated that the cross section of the rails  20  may be circular, square, rectangular, or any other desired cross-sectional shape without deviating from the scope of the invention. The rails  20  generally conform to the curvature of the track  10  thus extending in a straight path along the straight track segments  12  and in a curved path along the curved track segments  14 . The rails  20  may be thin with respect to the width of the track  10  and span only a partial width of the surface of the track  10  on which it is attached. According to the illustrated embodiment, each rail  20  includes a base portion  22  mounted to the track segment and a track portion  24  along which the mover  100  runs. Each mover  100  includes complementary rollers  110  to engage the track portion  24  of the rail  20  for movement along the track  10 . 
     One or more movers  100  are mounted to and movable along the rails  20  on the track  10 . With reference next to  FIG. 3 , an exemplary mover  100  is illustrated. Each mover  100  includes a side member  102 , a top member  104 , and a bottom member  106 . The side member  102  extends for a height at least spanning a distance between the rail  20  on the top surface  11  of the track  10  and the rail  20  on the bottom surface  13  of the track  10  and is oriented generally parallel to a side surface  21  when mounted to the track  10 . The top member  104  extends generally orthogonal to the side member  102  at a top end of the side member  102  and extends across the rail  20  on the top surface  11  of the track  10 . The top member  104  includes a first segment  103 , extending orthogonally from the side member  102  for the width of the rail  20 , which is generally the same width as the side member  102 . A set of rollers  110  are mounted on the lower side of the first segment  103  and are configured to engage the track portion  24  of the rail  20  mounted to the upper surface  11  of the track segment. According to the illustrated embodiment two pairs of rollers  110  are mounted to the lower side of the first segment  103  with a first pair located along a first edge of the track portion  24  of the rail and a second pair located along a second edge of the track portion  24  of the rail  20 . The first and second edges and, therefore, the first and second pairs of rollers  110  are on opposite sides of the rail  20  and positively retain the mover  100  to the rail  20 . The bottom member  106  extends generally orthogonal to the side member  102  at a bottom end of the side member  102  and extends for a distance sufficient to receive a third pair of rollers  110  along the bottom of the mover  100 . The third pair of rollers  110  engage an outer edge of the track portion  24  of the rail  20  mounted to the lower surface  13  of the track segment. Thus, the mover  100  rides along the rails  20  on the rollers  110  mounted to both the top member  104  and the bottom member  106  of each mover  100 . The top member  104  also includes a second segment  120  which protrudes from the first segment  103  an additional distance beyond the rail  20  and is configured to hold a position magnet  130 . According to the illustrated embodiment, the second segment  120  of the top member  104  includes a first portion  122  extending generally parallel to the rail  20  and tapering to a smaller width than the first segment  103  of the top member  104 . The second segment  120  also includes a second portion  124  extending downward from and generally orthogonal to the first portion  122 . The second portion  124  extends downward a distance less than the distance to the upper surface  11  of the track segment but of sufficient distance to have the position magnet  130  mounted thereto. According to the illustrated embodiment, a position magnet  130  is mounted within a recess  126  on the second portion  124  and is configured to align with a sensor  150  mounted within the top surface  11  of the track segment. 
     A linear drive system is incorporated in part on each mover  100  and in part within each track segment  12 ,  14  to control motion of each mover  100  along the segment. According to one embodiment of the invention shown in  FIG. 2 , the linear drive system includes drive magnets  140  mounted to the side member  102 . According to the illustrated embodiment, the drive magnets  140  are arranged in a block along an inner surface of the side member  102  with separate magnet segments alternately having a north pole, N, and south pole, S, pole facing the track segment  12 . The drive magnets  140  are typically permanent magnets, and two adjacent magnet segments including a north pole and a south pole may be considered a pole-pair. The drive magnets  140  are mounted on the inner surface of the side member  102  and when mounted to the track  10  are spaced apart from a series of coils  50  extending along the track  10 . As shown in  FIG. 4 , an air gap  141  is provided between each set of drive magnets  140  and the coils  50  along the track  10 . On the track  10 , the linear drive system includes a series of parallel coils  50  spaced along each track segment  12  as shown in  FIG. 2 . According to the illustrated embodiment, each coil  50  is placed in a channel  23  extending longitudinally along one surface of the track segment  12 . The electromagnetic field generated by each coil  50  spans the air gap  141  and interacts with the drive magnets  140  mounted to the mover  100  to control operation of the mover  100 . 
     According to another embodiment of the invention shown in  FIGS. 11-12 , the linear drive system includes drive magnets  255  mounted along the track. With reference also to  FIG. 4 , the drive magnets  255  may be mounted in the channel  23  extending longitudinally along one surface of the track segment  12 . A set of drive coils  250  is mounted to each mover  100 . The drive coils  250  are mounted to the side member  102  and spaced apart from the drive magnets  255  such that an air gap  141  is defined between each set of drive coils  250  and the drive magnets  255  along the track. The drive magnets  255  are preferably arranged with consecutive magnet segments alternately having a north pole, N, and south pole, S, pole facing the mover  100 . The mover  100  further includes a motor drive  200  mounted to the side member  102  and, as illustrated, is positioned between the side member  102  and the drive coils  250 . As will be discussed in more detail below, the motor drive  200  receives power from a power source located off the mover  100  and delivers the power to the drive coils  250 . The motor drive  200  controls the voltage and/or current provided to each drive coil  250  such that an electromagnetic field generated by each drive coil  250  on the mover  100  interacts with the drive magnets  255  mounted along the track  10  to control motion of the mover  100  along the track. Mounting the motor drive  200  along the side member  102  allows the side member to serve as a heat sink for the motor drive  200 . However, it is contemplated that the motor drive  200  may be mounted in other locations on the mover  100  without deviating from the scope of the invention. 
     According to one embodiment of the invention, a sliding transformer is provided to transfer power between the track and each mover. The sliding transformer includes a primary winding extending along the track and a secondary winding mounted to each mover. The primary winding may be a single coil or multiple coils. If formed as a single coil, the primary winding may include a pair of bus bars extending along the track where one bus bar defines a forward conduction path and the other bus bar defines a return conduction path. If the primary winding is formed of multiple coils, a conductor may be wound along the track in the direction of travel to define the forward and reverse conduction paths or, optionally, multiple traces on a printed circuit board may be formed. It is contemplated that the primary winding may be formed of a number of closed loops extending along a portion of the track. The track, for example, may include multiple track segments and a single primary winding may extend along the surface of each track segment. The secondary winding may similarly be a single coil or multiple coils. If formed as a single coil, the secondary winding may include a pair of bus bars extending along the mover in the direction of travel where one bus bar defines a forward conduction path and the other bus bar defines a return conduction path. If the secondary winding is formed of multiple coils, a conductor may be wound along the mover in the direction of travel to define the forward and reverse conduction paths or, optionally, multiple traces on a printed circuit board may be formed. Each mover includes a single secondary winding and multiple movers travel along the track. The primary and secondary windings are generally aligned with each other and extend along the track and along the mover in the direction of travel with an air gap present between the windings. 
     Turning to  FIGS. 4 and 5 , a sliding transformer  170  providing power to the mover  100  from a power source located off the mover is illustrated. The sliding transformer  170  provides wireless power transfer between the track  10  and a mover  100 . According to the illustrated embodiment, a primary winding  172  is provided on the track  10  and a secondary winding  182  is provided on the mover  100 . The primary winding  172  includes a forward conduction path  173  and a reverse conduction path  175  extending longitudinally along the track  10 . According to one embodiment of the invention, the forward and reverse conduction paths  173 ,  175  may span multiple track segments  12 ,  14 . An electrical connector may be provided between track segments  12 ,  14  to establish a continuous electrical connection between segments  12 ,  14 . In certain applications, such as a short oval, a single primary winding may be provided. One end for each of the forward and reverse conduction paths is connected to a power source and the other end for each of the forward and reverse conduction paths is electrical connected to each other to establish a conductive loop. In other applications, for example, due to an extended track length, it may be desirable to provide multiple primary windings  172 , where each primary winding extends for a portion of the length of the track  10 . According to one embodiment of the invention, each track segment  12 ,  14  includes a separate primary winding  172  extending the length of the track segment. 
     The forward and reverse conduction paths  173 ,  175  for the primary winding  172  may include either a single conductor or multiple conductors. With reference to  FIG. 5 , a first bus bar  174  is provided in the forward conduction path  173  and a second bus bar  176  is provided in the reverse conduction path  175 . If a separate primary winding  172  is present on each track segment, one end of each bus bar  174 ,  176  is connected to a power source and the other end of each bus bar may include an end cap joining the two bus bars and establishing a conductive loop. If the primary winding  172  spans multiple track segments, then an electrical connector may be provided between track segments to join adjacent bus bars. With reference to  FIG. 7 , the primary winding  172  may also include multiple conductors in each of the forward and reverse conduction paths  173 ,  175 . According to one embodiment of the invention, a single conductor may be wound along the length of the track segment  12  to form a coil. According to another embodiment of the invention, a printed circuit board (PCB) may be mounted along the length of the track segment  12  and a number of traces may be defined along the PCB to define the coil. In either embodiment, a first portion of the conductors define the forward conduction path  173  and a second portion of the conductors define the reverse conduction path  175 . 
     The secondary winding  182  includes a forward conduction path  183  and a reverse conduction path  185  extending in the direction of motion of the mover  100 . It is contemplated that each mover  100  will include a single secondary winding  182 . However, in some embodiments, multiple secondary windings  182  may be mounted on a mover  100  with each secondary winding  182  receiving power from the primary winding  172 . One end for each of the forward and reverse conduction paths is electrically connected to each other to establish a conductive loop and the other end supplies power to an electrical load on the mover  100 . It is contemplated that the electrical load may be an electrical device  300  such as an actuator or a sensor, which may be energized by either an alternating current (AC) voltage or a direct current (DC) voltage. A power converter  260  is provided to regulate the power flow received from the secondary winding  182  to the electrical load. 
     The forward and reverse conduction paths  183 ,  185  for the secondary winding  182  may include either a single conductor or multiple conductors. With reference to  FIG. 5 , a first bus bar  184  is provided in the forward conduction path  183  and a second bus bar  186  is provided in the reverse conduction path  185 . One end of each bus bar  184 ,  186  is connected to the electrical load on the mover  100  and the other end of each bus bar may include an end cap joining the two bus bars and establishing a conductive loop. With reference to  FIG. 8 , the secondary winding  182  may also include multiple conductors in each of the forward and reverse conduction paths  183 ,  185 . According to one embodiment of the invention, a single conductor may be wound along the mover  100  in the direction of travel of the mover  100  to form a coil. According to another embodiment of the invention, a printed circuit board (PCB) may be mounted to the mover  100  and a number of traces may be defined along the PCB to define the coil. In either embodiment, a first portion of the conductors define the forward conduction path  183  and a second portion of the conductors define the reverse conduction path  185 . 
     Turning next to  FIG. 9 , an exemplary power converter  350  for supplying power to the primary winding  172  is illustrated. The power converter  350  is configured to receive a three-phase AC voltage  352  at an input  354  of the power converter. The three-phase AC voltage  352  is, in turn, provided to a rectifier section  356  of the power converter  350 . The rectifier section  356  may include any electronic device suitable for passive or active rectification as is understood in the art. According to the illustrated embodiment, the rectifier section  356  includes a set of diodes  358  forming a diode bridge that rectifies the three-phase AC voltage to a DC voltage on the DC bus  362 . Optionally, the rectifier section  356  may include other solid-state devices including, but not limited to, thyristors, silicon controlled rectifiers (SCRs), or transistors to convert the input voltage  352  to a DC voltage for the DC bus  362 . The DC voltage is present between a positive rail  364  and a negative rail  366  of the DC bus  362 . A DC bus capacitor  368  is connected between the positive and negative rails,  364  and  366 , to reduce the magnitude of the ripple voltage resulting from converting the AC voltage to a DC voltage. It is understood that the DC bus capacitor  368  may be a single capacitor or multiple capacitors connected in parallel, in series, or a combination thereof. The magnitude of the DC voltage between the positive and negative rails,  364  and  366 , is generally equal to the magnitude of the peak of the AC input voltage. 
     The DC bus  362  is connected in series between the rectifier section  356  and an inverter section  370 . The inverter section  370  consists of a number of switches  372 . Each switch  372  is preferably a solid-state switching element, such as a transistor, thyristor, or SCR as is known in the art. The switching element may also include a free-wheeling diode connected across the switching element. Each of the switches  372  receives a switching signal, sometimes referred to as a gating signal,  374  to selectively enable the switch  372  and to convert the DC voltage from the DC bus  362  into a controlled AC voltage at an output  376  of the inverter section  370 . When enabled, each switch  372  connects the respective rail  364 ,  366  of the DC bus  362  to an output terminal. The primary winding  172  is connected to the output  376  of the inverter section to receive the controlled AC voltage as a power source for transmitting power from the track  10  to the movers  100 . 
     One or more modules are used to control operation of the power converter  350 . The modules may be stored programs executed on one or more processors, logic circuits, or a combination thereof. According to the illustrated embodiment, the power converter  350  includes a controller  351  and a memory device  353  in communication with the controller  351 . The controller  351  may be implemented, for example, in a microprocessor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), or other such customizable device. The memory device  353  may include transitory memory, non-transitory memory or a combination thereof. The memory device  353  may be configured to store data and programs, which include a series of instructions executable by the controller  351 . It is contemplated that the memory device  353  may be a single device, multiple devices, or incorporated, for example, as a portion of another device such as an application specific integrated circuit (ASIC). The controller  351  is in communication with the memory  353  to read the instructions and data as required to control operation of the power converter  350 . 
     The controller  351  also receives feedback signals indicating the current operation of the power converter  350 . The power converter  350  may include a voltage sensor  380  and/or a current sensor  382  on the DC bus  362  generating a feedback signal corresponding to the magnitude of voltage and/or current present on the DC bus  362 . The power converter  350  may also include a voltage sensor  384  and/or a current sensor  386  generating a feedback signal corresponding to the magnitude of voltage and/or current present at the output  376  of the inverter section  370 . The controller  351  utilizes the feedback signals to generate the switching signals  374  to control operation of the inverter section  370  and to generate an output voltage having a desired magnitude and frequency for the primary winding  172 . 
     It is contemplated that impedance matching circuits may be provided on one or both sided of the sliding transformer. A first impedance matching circuit  177  is illustrated between the utility power supply  171  and the primary winding  172 , and a second impedance matching circuit  187  is illustrated between the secondary winding  182  and the power converter  260 . The impedance matching circuit  177  may include one or more reactive components, such as an inductor and/or a capacitor, and resistors may be connected in series or parallel to create a resonant circuit. The frequency of the resonant circuit is selected to amplify a magnitude of voltage and/or current present on the windings to maximize power transfer across the sliding transformer. 
     With reference also to  FIG. 6 , the secondary winding  182  is spaced apart from the primary winding  172  by an air gap  180 . The current conducted in the primary winding  172  establishes an electromagnetic field along the forward and reverse conduction paths  173 ,  175 . The forward and reverse conduction paths  183 ,  185  of the secondary winding  182  are generally aligned with the forward and reverse conduction paths  173 ,  175  of the primary winding  172  and separated by the air gap  180 . In order for a current to be induced within the secondary winding  182  by the electromagnetic field generated by the primary winding  172 , the secondary winding  182  must be located within the field. Thus, the air gap  180  is small and may be, for example, less than 1.5 millimeters wide and, preferably, is less than 0.75 millimeters wide. In one embodiment of the invention, it is contemplated that the air gap  180  is about 0.5 millimeters wide. 
     Referring again to  FIG. 9 , the illustrated mover includes a rectifier section  262  with a set of diodes  264  to convert the AC voltage induced in the secondary winding  182  to a DC voltage present on a DC bus  261 . A DC bus capacitor  266  is connected between the positive and negative rails,  263  and  265 , to reduce the magnitude of the ripple voltage resulting from converting the AC voltage to a DC voltage. An electrical load  300  may is applied to the DC bus  261 . The power converter  350  on the track  10  is configured to regulate the voltage and/or current supplied to the primary winding  172  to, in turn, provide a desired power level to the electrical load  300 . 
     According to another embodiment of the invention, shown in  FIG. 10 , the mover  100  may also include a power converter  260  to regulate power flow on the mover  100 . The power converter  260  is configured to receive the AC voltage from the secondary winding  182  at an input  259  of the power converter. It is contemplated that impedance matching circuits may be provided on one or both sided of the sliding transformer. A first impedance matching circuit  177  is illustrated between the utility power supply  171  and the primary winding  172 , and a second impedance matching circuit  187  is illustrated between the secondary winding  182  and the power converter  260 . The AC voltage from either the secondary winding  182  or the impedance matching circuit  187 , if provided, is, in turn, provided to a rectifier section  262  of the power converter  260 . The rectifier section  262  may include any electronic device suitable for passive or active rectification as is understood in the art. According to the illustrated embodiment, the rectifier section  262  includes a set of diodes  264  forming a diode bridge that rectifies the AC voltage to a DC voltage on the DC bus  261 . Optionally, the rectifier section  262  may include other solid-state devices including, but not limited to, thyristors, silicon controlled rectifiers (SCRs), or transistors to convert the input voltage to a DC voltage for the DC bus  261 . The DC voltage is present between a positive rail  263  and a negative rail  265  of the DC bus  261 . A DC bus capacitor  266  is connected between the positive and negative rails,  263  and  265 , to reduce the magnitude of the ripple voltage resulting from converting the AC voltage to a DC voltage. It is understood that the DC bus capacitor  266  may be a single capacitor or multiple capacitors connected in parallel, in series, or a combination thereof. The magnitude of the DC voltage between the positive and negative rails,  263  and  265 , is generally equal to the magnitude of the peak of the AC input voltage. 
     The DC bus  261  is connected in series between the rectifier section  262  and a switching section  270 . It is contemplated that the switching section  270  may be configured to provide either an AC voltage output or a DC voltage output. The DC voltage output may be at a different voltage potential than the DC voltage potential present on the DC bus  261 . According to the illustrated embodiment, the switching section  270  is arranged as an inverter to provide an AC voltage output. The switching section  270  consists of a number of switches  272 . Each switch  272  is preferably a solid-state switching element, such as a transistor, thyristor, or SCR as is known in the art. The switching element may also include a free-wheeling diode connected across the switching element. Each of the switches  272  receives a switching signal, sometimes referred to as a gating signal,  274  to selectively enable the switch  272  and to convert the DC voltage from the DC bus  261  into a controlled AC voltage at an output  276  of the switching section  270 . When enabled, each switch  272  connects the respective rail  263 ,  265  of the DC bus  261  to an output terminal. One or more electrical loads  300  are connected to the output  276  of the inverter section to receive the controlled AC voltage as a power source to enable operation of the device on the mover  100 . 
     One or more modules are used to control operation of the power converter  260 . The modules may be stored programs executed on one or more processors, logic circuits, or a combination thereof. According to the illustrated embodiment, the power converter  260  includes a controller  271  and a memory device  273  in communication with the controller  271 . The controller  271  may be implemented, for example, in a microprocessor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), or other such customizable device. The memory device  273  may include transitory memory, non-transitory memory or a combination thereof. The memory device  273  may be configured to store data and programs, which include a series of instructions executable by the controller  271 . It is contemplated that the memory device  273  may be a single device, multiple devices, or incorporated, for example, as a portion of another device such as an application specific integrated circuit (ASIC). The controller  271  is in communication with the memory  273  to read the instructions and data as required to control operation of the power converter  260 . 
     The power converter  260  also receives feedback signals indicating the current operation of the power converter  260 . The power converter  260  may include a voltage sensor  280  and/or a current sensor  282  on the DC bus  261  generating a feedback signal corresponding to the magnitude of voltage and/or current present on the DC bus  261 . The power converter  260  may also include a voltage sensor  284  and/or a current sensor  286  generating a feedback signal corresponding to the magnitude of voltage and/or current present at the output  276  of the switching section  270 . The controller  271  utilizes the feedback signals to generate the switching signals  274  to control operation of the switching section  270  and to generate a desired output voltage for the load  300  present on the mover  100 . 
     Turning next to  FIGS. 15-18 , a generator  402  may be mounted to the mover  100  to provide power for use on the mover  100 . The generator  402  includes a drive shaft  404  connected to a drive wheel  406 . The drive wheel  406  may be, for example, a friction wheel, aligned with a side of a rail  20  or with a side surface  21  of the track segment  12 . As the mover  100  is commanded to travel along the track, the drive wheel  406  engages the side of the rail  20 , causing the drive wheel  406  to turn. The drive wheel  406 , in turn, rotates the drive shaft  404  causing a rotor within the generator to turn. As would be understood by one skilled in the art, rotation of the rotor generates power at an output of the generator due, for example, to rotation of permanent magnets mounted to the rotor, generating a magnetic field within the generator that induces a voltage and/or current on a stator coil within the generator. A cable  408  connects the output of the generator to a power converter  410  mounted on the mover  100 . 
     The power converter  410 , as shown in more detail in  FIG. 18 , may be configured to receive an AC voltage from the generator  402  and convert the AC voltage to a desired AC or DC voltage for use by an electronic device on the mover  100 . The illustrated power converter  410  receives the AC voltage from the generator  402  at an input  424  of the power converter. The AC voltage is, in turn, provided to a rectifier section  426  of the power converter  410 . The rectifier section  426  may include any electronic device suitable for passive or active rectification as is understood in the art. According to the illustrated embodiment, the rectifier section  426  includes a set of diodes  428  forming a diode bridge that rectifies the three-phase AC voltage to a DC voltage on the DC bus  432 . Optionally, the rectifier section  426  may include other solid-state devices including, but not limited to, thyristors, silicon controlled rectifiers (SCRs), or transistors to convert the input voltage to a DC voltage for the DC bus  432 . The DC voltage is present between a positive rail  436  and a negative rail  436  of the DC bus  432 . A DC bus capacitor  438  is connected between the positive and negative rails,  434  and  436 , to reduce the magnitude of the ripple voltage resulting from converting the AC voltage to a DC voltage. It is understood that the DC bus capacitor  438  may be a single capacitor or multiple capacitors connected in parallel, in series, or a combination thereof. The magnitude of the DC voltage between the positive and negative rails,  434  and  436 , is generally equal to the magnitude of the peak of the AC input voltage. 
     According to the illustrated embodiment, the DC bus  432  is connected in series between the rectifier section  426  and an inverter section  440 . The inverter section  440  consists of a number of switches  4422 . Each switch  442  is preferably a solid-state switching element, such as a transistor, thyristor, or SCR as is known in the art. The switching element may also include a free-wheeling diode connected across the switching element. Each of the switches  442  receives a switching signal, sometimes referred to as a gating signal,  444  to selectively enable the switch  442  and to convert the DC voltage from the DC bus  432  into a controlled AC voltage at an output  446  of the inverter section  440 . When enabled, each switch  442  connects the respective rail  434 ,  436  of the DC bus  432  to an output terminal. The AC voltage present at the output  446  of the power converter  410  may be supplied to and provide power for AC electrical devices  300  present on the mover  100 . 
     Optionally, the power converter  410  may be configured to supply a DC voltage to an electrical device  300  on the mover. Rather than having an inverter section  440  as shown in  FIG. 18 , the power converter may include a DC-to-DC power converter that converts the voltage present on the DC bus  432  to another DC voltage suitable for powering the DC electrical device  300 . Optionally, the AC voltage from the generator  402  may be converted directly to the desired DC voltage desired to power a DC electrical device  300  and the device  300  may be connected directly to the DC bus  432 . As further illustrated in  FIG. 18 , an energy storage device  418  such as a battery or a super-capacitor may be mounted to the mover  100 . An energy regulator  415  may be provided to charge the energy storage device  418  when excess electrical energy is being generated by the generator  402 , and the energy regulator  415  may supply the stored energy from the energy storage device  418  to the DC bus  432  when the energy demanded from the electrical devices  300  exceed the energy being generated by the generator  402 . It is further contemplated that the energy regulator  415  may be incorporated within the power converter  410  such that the controller  421  for the power converter  410  also controls the energy regulator  415 . 
     One or more modules are used to control operation of the power converter  410 . The modules may be stored programs executed on one or more processors, logic circuits, or a combination thereof. According to the illustrated embodiment, the power converter  410  includes a controller  421  and a memory device  423  in communication with the controller  421 . The controller  421  may be implemented, for example, in a microprocessor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), or other such customizable device. The memory device  423  may include transitory memory, non-transitory memory or a combination thereof. The memory device  423  may be configured to store data and programs, which include a series of instructions executable by the controller  421 . It is contemplated that the memory device  423  may be a single device, multiple devices, or incorporated, for example, as a portion of another device such as an application specific integrated circuit (ASIC). The controller  421  is in communication with the memory  423  to read the instructions and data as required to control operation of the power converter  410 . 
     The controller  421  also receives feedback signals indicating the current operation of the power converter  410 . The power converter  410  may include a voltage sensor  450  and/or a current sensor  452  on the DC bus  432  generating a feedback signal corresponding to the magnitude of voltage and/or current present on the DC bus  432 . The power converter  410  may also include a voltage sensor  454  and/or a current sensor  456  generating a feedback signal corresponding to the magnitude of voltage and/or current present at the output  446  of the inverter section  440 . The controller  421  utilizes the feedback signals to generate the switching signals  444  to control operation of the inverter section  440  and to generate an output voltage having a desired magnitude and frequency for the electrical devices  300  present on the mover  100 . 
     With reference again to  FIG. 15 , the power converter  410  is illustrated as mounted on a circuit board  412  and stand-offs  414  on the upper surface of the mover  100 . An energy storage device  418  is similarly mounted to the upper surface of the mover  100  and connected to the power converter  410  via a cable  416 . The illustrated embodiment further includes a platform  420  mounted to the top surface of the mover  100  with stand-offs  422 . The platform  420  may be configured, for example, to receive a work piece, additional fixtures, or the electronic devices  300  to be powered by the generator  402 . The illustrated embodiment is intended to be exemplary and is not intended to be limiting. An alternate embodiment, for example, may include an enclosed module which includes the power converter  410  and/or the energy storage device  418 . The enclosed module may be mounted to the top, side, or bottom of the mover  100 . 
     Turning next to  FIGS. 19-22 , an optical transmitter  505  may be mounted to the track and be configured to transmit power to the mover  100  via a light beam  508 . According to the illustrated embodiment, a mounting fixture  501  extends down below the track segment  12  an is configured to receive the light from the optical transmitter  505 . The optical transmitter  505  may be, for example, one or more laser diodes  504  mounted within a housing  503  which is, in turn attached to the mounting fixture  501 . As shown in  FIG. 22 , the optical transmitter  505  may receive power from a utility supply  171 . The AC voltage from the utility may be converted to a DC voltage with a rectifier circuit  500 . It is contemplated that the utility voltage may be provided to each track segment  12  with separate rectifier circuits  500  similarly mounted on each track segment  12 . Optionally, one or more front-end rectifier units may receive the utility voltage and supply a DC voltage to the track or a portion of the track, and each track segment  12  receives the DC voltage from the front-end rectifier unit. Each rectifier circuit  500  or front-end rectifier unit may include any electronic device suitable for passive or active rectification as is understood in the art. According to the illustrated embodiment, the rectifier circuit  500  includes a set of diodes forming a diode bridge that rectifies the AC voltage from the utility supply  171  to a DC voltage for the driver circuit  502 . Optionally, the rectifier circuit  500  may include other solid-state devices including, but not limited to, thyristors, silicon controlled rectifiers (SCRs), or transistors to convert the input voltage to a DC voltage. The DC voltage is provided to a driver circuit  502 , which, in turn, enables one or more laser diodes  504 . Optionally, the driver circuit  502  may receive an AC voltage directly and incorporate a rectifier circuit or other power conversion circuit to supply a DC voltage to the laser diode  504 . Although illustrated as a single laser diode  504 , it is contemplated that multiple laser diodes  504  may be utilized. The optical transmitter  505  may also include one or more optical devices, such as filters, lenses, and the like to direct and focus the light emitted from each laser diode  504  toward a receiver mounted on the mover  100 . 
     The receiver  510  on the mover  100  includes one or more devices that convert light energy into electrical energy. According to the illustrated embodiment, the receiver  510  includes one or more photovoltaic modules and may form a photovoltaic array. Light incident on the photovoltaic array  510  is converted into electrical energy. Because the frequency of the light emitted from the optical transmitter  505  may be selected and/or is known, the construction of the photovoltaic array  510  may be selected to improve the efficiency of energy conversion between optical energy and electrical energy. 
     A power converter  520 , as shown in more detail in  FIG. 22 , may be configured to receive a DC voltage from the PV array  510  and convert the input DC voltage to either an AC voltage or a DC voltage of another amplitude for use by an electronic device on the mover  100 . The illustrated power converter  520  receives the DC voltage from the PV array  510  at an input  522  to the power converter  520 . The DC voltage is, in turn, provided to a voltage regulator  524 . As is understood, a PV array  510  typically outputs a DC voltage. The amplitude of the DC voltage may be different than an amplitude of a DC voltage needed to operate an electrical device  300  on the mover  100 . Similarly, the amplitude of the DC voltage may be different than an amplitude of a DC voltage needed to supply an AC voltage to an electrical device  300  on the mover  100 . The voltage regulator  524  may be configured as a buck converter or a boost converter to change the voltage level from a first amplitude supplied by the PV array  510  to a second amplitude required by other devices mounted on the mover  100 . The voltage regulator  524  may further include devices, such as capacitors and the like to reduce voltage ripple due to changes in the amount of light incident on the PV array  510  and to help maintain the voltage level at a desired voltage level. The DC voltage output from the voltage regulator is present between a positive rail  528  and a negative rail  530  of a DC bus  526 . A DC bus capacitor  532  is shown connected between the positive and negative rails,  528  and  530 , to reduce the magnitude of the ripple voltage present on the DC bus  526 . As previously indicated, it is contemplated that the DC bus capacitor  532  may be incorporated into the voltage regulator  425  and/or in the inverter section  534 . 
     According to the illustrated embodiment, the DC bus  526  is connected in series between the voltage regulator  524  and an inverter section  534 . The inverter section  534  is used to provide an AC voltage to electrical devices  300  mounted on the mover  100 . The inverter section  534  may consist of a number of switches, as discussed above in other inverter sections. Each switch is preferably a solid-state switching element, such as a transistor, thyristor, or SCR as is known in the art. The switching element may also include a free-wheeling diode connected across the switching element. Each of the switches receives a switching signal, sometimes referred to as a gating signal, to selectively enable the switch and to convert the DC voltage from the DC bus  526  into a controlled AC voltage at an output  536  of the inverter section  534 . The AC voltage present at the output  536  of the power converter  520  may be supplied to and provide power for AC electrical devices  300  present on the mover  100 . 
     Optionally, the power converter  520  may be configured to supply a DC voltage to an electrical device  300  on the mover. Each DC electrical device  300  may be connected directly to the DC bus  526 . Optionally, a separate DC-to-DC power converter may be provided to convert the voltage present on the DC bus  526  to another DC voltage suitable for powering the DC electrical device  300 . According to still another embodiment, the voltage regulator  524  may be configured to output multiple DC voltages including, for example, positive or negative five volts (+/−5 VDC) or positive or negative twenty-four volts (+/−24 VDC). 
     As further illustrated in  FIG. 19 , an energy storage device  518  such as a battery or a super-capacitor may be mounted to the mover  100 . The energy storage device  518  may include a dedicated energy regulator to charge the energy storage device  518  when excess electrical energy is being generated by the photovoltaic array  510  and to draw the stored energy from the energy storage device  518  to the DC bus  526  when the energy demanded from the electrical devices  300  exceed the energy being generated by the photovoltaic array  510 . Optionally, the energy storage device  518  may be connected directly to the DC bus  526 . It is further contemplated that an energy regulator for the energy storage device  518  may be incorporated within the voltage regulator  524  such that the controller  533  for the power converter  520  also controls the energy regulator. 
     One or more modules are used to control operation of the power converter  520 . The modules may be stored programs executed on one or more processors, logic circuits, or a combination thereof. According to the illustrated embodiment, the power converter  520  includes a controller  533  and a memory device  531  in communication with the controller  533 . The controller  533  may be implemented, for example, in a microprocessor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), or other such customizable device. The memory device  531  may include transitory memory, non-transitory memory or a combination thereof. The memory device  531  may be configured to store data and programs, which include a series of instructions executable by the controller  533 . It is contemplated that the memory device  531  may be a single device, multiple devices, or incorporated, for example, as a portion of another device such as an application specific integrated circuit (ASIC). The controller  533  is in communication with the memory  531  to read the instructions and data as required to control operation of the power converter  520 . 
     The controller  533  also receives feedback signals indicating the current operation of the power converter  520 . The power converter  520  may include a voltage sensor  540  and/or a current sensor  542  on the DC bus  526  generating a feedback signal corresponding to the magnitude of voltage and/or current present on the DC bus  526 . The power converter  520  may also include a voltage sensor  544  and/or a current sensor  546  generating a feedback signal corresponding to the magnitude of voltage and/or current present at the output  536  of the inverter section  534 . The controller  533  utilizes the feedback signals to generate the switching signals to control operation of the inverter section  534  and to generate an output voltage having a desired magnitude and frequency for the electrical devices  300  present on the mover  100 . The controller  533  may additionally receive additional feedback signals from the voltage regulator  524  and may utilize the feedback signals to regulate the voltage level on the DC bus  526  and/or to supply various levels of DC voltage for use by the electrical devices  300  present on the mover  100 . 
     With reference again to  FIG. 19 , the power converter  520  is illustrated as mounted on a circuit board  514  and stand-offs  516  on the upper surface of the mover  100 . An energy storage device  518  is similarly mounted to the upper surface of the mover  100  and connected to the power converter  520  via a cable  517 . The illustrated embodiment further includes a platform  490  mounted to the top surface of the mover  100  with stand-offs  492 . The platform  490  may be configured, for example, to receive a work piece, additional fixtures, or the electronic devices  300  to be powered by the optical source  505 . The illustrated embodiment is intended to be exemplary and is not intended to be limiting. An alternate embodiment, for example, may include an enclosed module which includes the power converter  520  and/or the energy storage device  518 . The enclosed module may be mounted to the top, side, or bottom of the mover  100 . 
     As previously indicated, one embodiment of the linear drive system includes drive magnets  255  arranged along the track  10  and drive coils  250  mounted to each mover. With reference then to  FIGS. 11-14 , one arrangement of a controller for this embodiment of the linear drive system is illustrated. A sliding transformer is provided between the track  10  and each mover  100  in the manner discussed above. Optionally, other methods of providing power to the mover  100  as it travels along the track may be utilized. The power may be supplied by the generator  402  mounted to the mover  100 , as shown in  FIG. 17 , or by the optical source  505 , as shown in  FIG. 21 . The power sources may further include an energy storage device (e.g.,  418  or  518 ) to supplement power when the power source is not supplying power or not supplying sufficient power to energize the drive coils. Each mover  100  further includes a motor drive  200  configured to receive power from power source on the mover  100 , such as the secondary winding  182 , the generator  402 , or the optical source  505 . 
     With reference to  FIG. 14 , the motor drive  200  may be configured to receive an AC voltage from the secondary winding  182  at an input  202  of the motor drive. The AC voltage is, in turn, provided to a rectifier section  204  of the motor drive  200 . The rectifier section  204  may include any electronic device suitable for passive or active rectification as is understood in the art. According to the illustrated embodiment, the rectifier section  204  includes a set of diodes  206  forming a diode bridge that rectifies the three-phase AC voltage to a DC voltage on the DC bus  208 . Optionally, the rectifier section  204  may include other solid-state devices including, but not limited to, thyristors, silicon controlled rectifiers (SCRs), or transistors to convert the input voltage to a DC voltage for the DC bus  208 . The DC voltage is present between a positive rail  210  and a negative rail  212  of the DC bus  208 . A DC bus capacitor  214  is connected between the positive and negative rails,  210  and  212 , to reduce the magnitude of the ripple voltage resulting from converting the AC voltage to a DC voltage. It is understood that the DC bus capacitor  214  may be a single capacitor or multiple capacitors connected in parallel, in series, or a combination thereof. The magnitude of the DC voltage between the positive and negative rails,  210  and  212 , is generally equal to the magnitude of the peak of the AC input voltage. 
     Optionally, the AC voltage may be supplied to the input of the motor drive  200  from the generator  402 . When the mover  100  is travelling, the generator  402  may be configured to generate sufficient energy to propel the mover along the track. In addition, a portion of the energy produced by the generator  402  may be stored in the energy storage device  418 . It is contemplated that the power converter  410  shown in  FIG. 17  may be a separate power converter from the motor drive  200  or incorporated with the motor drive  200 . The AC voltage output from the generator  402 , for example may be supplied to a common DC bus, where the common DC bus acts as the DC bus in both the motor drive  200  and the power converter  410 . Further, the energy storage device  418  may be connected directly to the shared DC bus as well with the regulator  415  connected between the shared DC bus and the energy storage device  418 . The level of charge on the energy storage device is preferably maintained at a sufficient level to supply power to the motor drive  200  to start motion of the mover  100 . Subs 
     According to still another embodiment, the motor drive  200  may be powered directly from the DC bus  526  of the power converter  520  configured to receive power from the optical source  505 . It is contemplated that the power converter  520  discussed above with respect to the optical source  505  may be combined with or replace the motor drive  200 . The power supplied by the optical source  505  may be utilized directly to energize motor coils  250 . Optionally, a common DC bus may be utilized by both the motor drive  200  and the power converter  520 , where the inverter section  220  of the motor drive  200  supplies power to the drive coils  250  and the inverter section  534  of the power converter  520  supplies power to AC electronic devices  300  mounted to the mover  100 . 
     The DC bus  208  is connected in series between the rectifier section  204  and an inverter section  220 . The inverter section  220  consists of a number of switches  222 . Each switch  222  is preferably a solid-state switching element, such as a transistor, thyristor, or SCR as is known in the art. The switching element may also include a free-wheeling diode connected across the switching element. Each of the switches  222  receives a switching signal, sometimes referred to as a gating signal,  224  to selectively enable the switch  222  and to convert the DC voltage from the DC bus  208  into a controlled AC voltage at an output  226  of the inverter section  220 . When enabled, each switch  222  connects the respective rail  210 ,  212  of the DC bus  208  to an output terminal. The drive coils  250  are connected to the output  226  of the inverter section to receive the controlled AC voltage to establish an electromagnetic field to interact with the drive magnets  255  and control motion of the corresponding mover  100 . 
     One or more modules are used to control operation of the motor drive  200 . The modules may be stored programs executed on one or more processors, logic circuits, or a combination thereof. According to the illustrated embodiment, the motor drive  200  includes a controller  230  and a memory device  232  in communication with the controller  230 . The controller  230  may be implemented, for example, in a microprocessor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), or other such customizable device. The memory device  232  may include transitory memory, non-transitory memory or a combination thereof. The memory device  232  may be configured to store data and programs, which include a series of instructions executable by the controller  230 . It is contemplated that the memory device  232  may be a single device, multiple devices, or incorporated, for example, as a portion of another device such as an application specific integrated circuit (ASIC). The controller  230  is in communication with the memory  232  to read the instructions and data as required to control operation of the motor drive  200 . 
     The motor drive  200  also receives feedback signals indicating the current operation of the motor drive  200 . The motor drive  200  may include a voltage sensor  236  and/or a current sensor  238  on the DC bus  208  generating a feedback signal corresponding to the magnitude of voltage and/or current present on the DC bus  208 . The motor drive  200  may also include a voltage sensor  240  and/or a current sensor  242  generating a feedback signal corresponding to the magnitude of voltage and/or current present at the output  226  of the inverter section  220 . The controller  230  utilizes the feedback signals to generate the switching signals  224  to control operation of the inverter section  220  and to generate a desired output voltage for each drive coil  250  present on the mover  100 . 
     It is further contemplated that a mover  100  with a motor drive  200  may also include one or more electronic devices mounted to the mover  100 . As illustrated, a load  300  is powered by a power converter  260 , separate from the motor drive  200 , also mounted to the mover  100 . The illustrated power converter  260  includes only a switching section  270  as described above with respect to  FIG. 10 . The DC bus of the power converter  260  illustrated in  FIG. 14  is connected directly to the DC bus  208  of the motor drive  200 . Optionally, the power converter  260  may include an input receiving power from the source in parallel with the motor drive  200 . 
     In operation, a power source provides power to each mover  100  travelling along the track  10  without requiring a fixed connection to the mover  100 . According to one embodiment of the invention, the sliding transformer wirelessly provides power from the track  10  to each mover  100  travelling along the track  10 . According to the embodiment illustrated in  FIG. 10 , a utility power supply  171  is connected to the primary winding  172 . The utility power supply  171  provides power at a fixed voltage and frequency and the power converter  260  on each mover  100  regulates power drawn from the secondary winding  182 . Optionally, a power converter  350  may be connected between a utility power supply and the primary winding  172 , as shown in  FIG. 9 . The power converter  350  may be controlled to provide a voltage to the primary winding  172  with a variable voltage and/or a variable frequency. If the primary winding  172  spans multiple track segments, a single connection to the power supply is provided for each primary winding and suitable connectors are provided between segments to join the forward and reverse conduction paths. If a separate primary winding  172  is provided for each track segment  12 , a separate power converter  350  may be provided on each track segment to convert power from an input power source to a modulated voltage for the primary winding  172 . 
     At a fixed voltage level, for example, 110 VAC, the frequency of the voltage applied to the primary winding  172  impacts the amount of power transferred between the primary and secondary windings and also impacts the level of voltage ripple present at the secondary winding. With a utility power supply  171 , voltage is provided, for example, at 110 VAC and 60 Hz. With a power converter  350  supplying power to the primary winding  172 , the output may be modulated to provide voltage at a higher frequency, ranging, for example, from 60-2000 Hz. According to one embodiment of the invention, the voltage is provided with a frequency in a range of 250-1000 Hz. 
     Increasing the frequency of the voltage supplied to the primary winding, impacts voltage coupling between the primary winding  172  and the secondary winding  182 . As the frequency of the voltage increases, the ripple on the voltage present on the secondary winding  182  decreases. As a result, the capacitance value for the DC bus capacitor  266  present on the mover  100  can be decreased. However, as the frequency increases, the amplitude of the voltage present on the secondary winding decreases and, therefore, the total power transferred similarly decreases. A comparison of the voltages and power present on the secondary winding of an exemplary sliding transformer is presented in Table 1 below. The amplitude of input voltage is constant at 110 VAC and the number of turns on the secondary winding is constant at sixty turns. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Evaluation of different frequencies of voltage provided to 
               
               
                 a primary winding with a secondary winding having 60 turns 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Frequency 
                 60 Hz 
                 250 Hz 
                 1000 Hz 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 V avg  (V) 
                 80 
                 79 
                 62 
               
               
                   
                 V ripple  (V pk-pk ) 
                 30 
                 6 
                 1 
               
               
                   
                 P avg  (W) 
                 713 
                 629 
                 386 
               
               
                   
                   
               
            
           
         
       
     
     The power transferred between the primary winding  172  and the secondary winding  182  is further influenced by the number of turns present in the secondary winding. According to one embodiment of the invention, the number of turns present in the primary winding matches the number of turns present in the secondary winding to provide a 1:1 turns ratio. It is contemplated that various other turns ratios may be utilized without deviating from the scope of the invention. As the number of turns in the secondary winding  182  increases, the voltage level on the secondary winding decreases. However, as the number of turns in the secondary winding  182  increases, the magnitude of voltage ripple also decreases. Thus, to increase the power transferred between the primary and secondary windings, it is preferable to have a lower number of turns on the secondary winding. A comparison of the voltages and power present on the secondary winding of an exemplary sliding transformer as a result of different numbers of turns on the secondary winding is presented in Table 2 below. The amplitude of input voltage is constant at 110 VAC and the frequency of the input voltage is constant at sixty Hertz. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Evaluation of different numbers of turns on a secondary winding 
               
               
                 with a constant frequency supplied to a primary winding 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Secondary Turns 
                 60 
                 40 
                 20 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 V avg  (V) 
                 80 
                 81 
                 82 
               
               
                   
                 V ripple  (V pk-pk ) 
                 30 
                 37 
                 38 
               
               
                   
                 P avg  (W) 
                 713 
                 705 
                 745 
               
               
                   
                   
               
            
           
         
       
     
     In addition, the present inventors have identified that the effect of increasing the frequency of the voltage supplied to the primary winding  172  has less impact on the voltage drop when the number of turns of the secondary winding  182  is decreased. For example, when the number of turns on the secondary winding is twenty turns, the average voltage remains about constant as the frequency of the voltage supplied to the primary winding increases. In fact, the average voltage increases slightly as the voltage ripple decreases providing an improved voltage on the secondary winding. A comparison of the voltages and power present on the secondary winding of another exemplary sliding transformer is presented in Table 3 below. The amplitude of input voltage is constant at 110 VAC and the number of turns on the secondary winding is constant at twenty turns. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Evaluation of different frequencies of voltage provided to 
               
               
                 a primary winding with a secondary winding having 20 turns 
               
            
           
           
               
               
               
               
            
               
                   
                 Frequency 
                 60 Hz 
                 1000 Hz 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 V avg  (V) 
                 82 
                 88 
               
               
                   
                 V ripple  (V pk-pk ) 
                 38 
                 2 
               
               
                   
                 P avg  (W) 
                 745 
                 770 
               
               
                   
                   
               
            
           
         
       
     
     According to one embodiment of the invention, each of the primary and secondary windings have the same number of turns and, therefore, have a 1:1 turns ratio. The primary winding  172  includes a first coil extending along the length of each track segment  12  and each mover  100  includes a secondary winding  182  having eighty or fewer turns and, preferably, between twenty and sixty turns. The primary winding is connected to a utility supply and, therefore, receives a fixed sixty hertz input voltage. Connecting the primary winding directly to the utility supply provides a reduced system cost by not requiring a power converter to supply a variable frequency voltage to each primary winding. 
     In alternate embodiments, however, it is contemplated that a power converter  350  is provided to supply a variable frequency voltage to the primary winding  172 . When a power converter is provided to supply voltage to the primary winding  172 , the frequency of the voltage may be supplied at 200 Hz or greater and, preferably at 1000 Hz or greater. It is further contemplated that the turns ratio between the primary and secondary windings may be varied. 
     It is further contemplated that the mover  100  may include an energy storage device to supplement operation of the motor drive  200  or power converter  260 . During, for example, periods of short term power loss, the energy storage device may allow the motor drive  200  or power converter  260  to continue operation. The energy storage device may be the DC bus capacitor  214 ,  366  present in the motor drive  200  or power converter  260 , respectively. The DC bus capacitor may be sized, for example, to include sufficient power to allow a mover  100  to traverse a gap between primary windings  172 . Such a gap may exist between track segments  12  if separate primary windings  172  are provided on each segment. Optionally, the energy storage device may include a larger capacity and may be, for example, a super capacitor or a battery, where the energy storage device may provide sufficient energy, for example, such that the mover  100  may traverse one or more track segments that do not include a primary winding. Thus, the mover  100  may receive power during one segment of the track and utilize the stored power along another segment of the track. 
     According to another embodiment of the invention, an optical transmitter  505  wirelessly provides power from the track  10  to each mover  100  travelling along the track  10 . According to the embodiment illustrated in  FIG. 22 , a utility power supply  171  is connected to the optical transmitter  505 . The optical transmitter  505  may include the rectifier circuit  500  and drive circuit  502  to convert the AC voltage from the utility power supply  171  to a desired DC voltage to power the laser diodes  504  in the transmitter  505 . One or more optical devices, such as filters and/or lenses may be mounted between the laser diode  504  and an opening  506  in the housing  503  through which the light  508  is emitted. The filters and/or lenses may remove unwanted components and orient or focus the light beams emitted from the laser diodes  504  prior to transmission. Although illustrated and discussed herein with respect to laser diodes  504 , it is contemplated that various other types of lasers may be mounted to the track  10  and emit light for transferring power to the movers  100 . The laser may be, but are not limited to, a gas laser, a solid-state laser, or a chemical laser. 
     The laser is selected such that a sufficient amount of power may be transmitted via the optical beam to each mover  100  according to the application requirements. An electronic actuator, for example, may energize intermittently and require only a few watts to tens of watts of power to activate. The light emitted 508 may only be required to transfer a corresponding level of power to the mover  100 . Further, if an energy storage device  518  is provided on the mover  100 , the light  508  may transmit a fraction of the required power on a continuous basis. When the actuator is not energized, the energy transmitted from the laser is stored in the energy storage device  518 . When the actuator is energized, the stored energy is delivered to the actuator to supplement the energy transmitted by the laser. Thus, the level of energy transmitted by the laser must only be sufficient to charge the energy storage device  518  between the intermittent activation of the actuator. In another embodiment, the drive coils  250  may be mounted to the mover  100  and sufficient power must be supplied to the mover  100  to energize the drive coils  250  to control travel of the mover  100  along the track  10 . It may be desirable to supply hundreds of watts or up to one kilowatt of power to the mover  100  to supply sufficient power to energize the drive coils  250 . 
     An optical receiver  510  is mounted to each mover  100  to receive the light  508  beam from the transmitter  505  as the mover  100  travels along the track  10 . The receiver is any device that converts light energy into electrical energy. According to the illustrated embodiment, the receiver  510  includes one or more photovoltaic modules and may form a photovoltaic array. As illustrated in  FIG. 19 , the optical transmitter  505  may be offset from the receiver  510  such that the receiver  510  does not mechanically interfere with the transmitter  505  as the mover  100  passes the transmitter  505 . The opening  506  in the housing  503  may be directed toward the receiver  510  such that the light  508  is emitted across the gap separating the transmitter  505  and the receiver  510 . As the mover  100  travels along the track, the distance between the transmitter  505  and receiver  510  will change and, therefore, the location on the receiver at which the light  508  is incident will change. When the mover  100  is distant from the transmitter  505 , the light  508  will fall on the portion of the mover  100  furthest from the track  10 , and when the mover  100  is proximate the transmitter  505 , the light  508  will fall on the portion of the mover  100  closest to the track  10 . Thus, the optical receiver  510  may extend along the width of the bottom member  106  of the mover  100  to provide the longest distance over which the receiver will receive the light  508 . The optical transmitter  505  and receiver  510  are preferably configured to allow the emitted light  508  to fall on the receiver  510  over the length of at least one track segment  12 . Thus, a separate transmitter  505  may be provided on each track segment  12  to provide power to each mover  100  traveling along the track segment  12 . 
     In the motion control system, multiple movers  100  may travel along a track segment  12 . In the illustrated embodiment, a first mover  100  located in front of a second mover  100  may cause interference between the optical transmitter  505  and the receiver  510  on the second mover  100 . Therefore, multiple transmitters  505  may be mounted on the track segment  12  to provide power to each mover  100  present on the segment  12 . The mounting fixture  501  may extend downward for a further distance and multiple transmitters  505  may be located one below the other along the mounting fixture  501 . The receivers  510  may similarly be offset below each other on successive movers  100  such that each transmitter  505  may emit light  508  to a different receiver  510 . The number of transmitters and locations of receivers  510  correspond to a maximum number of movers  100  supported by a track segment  12 . 
     As previously indicated, the mover  100  may include an energy storage device to supplement operation of the motor drive  200  or power converter  520 . During, for example, periods of short term power loss, the energy storage device may allow the motor drive  200  or power converter  520  to continue operation. The energy storage device may be the DC bus capacitor  214 ,  532  present in the motor drive  200  or power converter  520 , respectively. The DC bus capacitor may be sized, for example, to include sufficient power to allow a mover  100  to traverse a gap between track segments  12  during which no light  508  is incident on the optical receiver  510 . Optionally, the energy storage device may include a larger capacity and may be, for example, a super capacitor or a battery, where the energy storage device may provide sufficient energy, for example, such that the mover  100  may traverse one or more track segments that do not include an optical transmitter  505 . Thus, the mover  100  may receive power along one segment of the track and utilize the stored power along another segment of the track. 
     According to another embodiment of the invention, a generator  402  provides power the mover  100  while traveling along the track  10 . According to the embodiment illustrated in  FIGS. 15-18 , a drive wheel  406  is mounted to the mover  100  such that it engages a portion of the track  10  as the mover  100  travels along the track  10 . A drive shaft  404  extends between the drive wheel  406  and the generator  402 . The drive shaft  404  causes a rotor within the generator to turn. Permanent magnets mounted to the rotor generate a magnetic field which, in turn, induces a current and voltage in the stator of the generator  402 , thereby generating electric power due to rotation of the drive wheel  406 . As discussed above, the electric power is provided to a power converter  410  for use by electrical devices  300  or by a motor drive  200  mounted on the mover  100 . 
     Each generator  402  is configured to generate electrical power as the mover  100  travels. The amount of power is determined by the construction of the generator  402 , the speed of travel of the mover  100  and by the amount of travel performed by the mover  100 . The generator  402  may be selected such that a sufficient amount of power is generated on mover  100  to power one or more electronic devices  300  mounted to the mover  100 . An electronic actuator, for example, may energize intermittently and require only a few watts to tens of watts of power to activate. The generator  402  may only be required to output a corresponding level of power to the mover  100 . If the mover  100  is travelling during actuation, the generator  402  may supply power directly to the electronic device  300 . If actuation is required when the mover  100  is stopped, an energy storage device  418  may be provided on the mover  100 . The energy storage device  418  receives power output from the generator  402  while the mover  100  is moving. When the actuator is energized, the stored energy is delivered to the actuator. Thus, the level of energy output from the generator  402  must only be sufficient to charge the energy storage device  418  between the intermittent activation of the actuator. In another embodiment, the drive coils  250  may be mounted to the mover  100  and sufficient power must be supplied to the mover  100  to energize the drive coils  250  to control travel of the mover  100  along the track  10 . It may be desirable to supply hundreds of watts or up to one kilowatt of power to the mover  100  to supply sufficient power to energize the drive coils  250 . Initially sufficient energy must be stored in the energy storage device  418  to get the mover  100  started. Once the mover  100  is travelling, the power output from the generator is provided to the motor drive  200  for subsequent energization of the drive coils  250 . 
     It is contemplated that the generator  402  may be used in combination with either the sliding transformer or the optical transmitter  505  to supply power to the mover  100 . A portion of the electrical power required by the mover  100  may be output from the generator  402  and a portion of the electrical power may be transmitted to the mover via either the sliding transformer or the optical transmitter. Further, while separate power converters are illustrated, it is contemplated that portions of the power converters may be combined to reduce the number of components present on the mover  100 . For example, a common dc bus may be used with a generator, sliding transformer, motor drive, and an electronic device present on the mover  100 . The AC power supplied from either the generator or the sliding transformer may be provided via respective rectifier sections to the dc bus and the motor drive and the electronic device may receive power from the dc bus via respective inverter sections. 
     It should be understood that the invention is not limited in its application to the details of construction and arrangements of the components set forth herein. The invention is capable of other embodiments and of being practiced or carried out in various ways. Variations and modifications of the foregoing are within the scope of the present invention. It also being understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention.