Abstract:
A system for controlling the speed of a brushless repulsion motor having a series of switches mounted on a rotating armature for shorting circumferentially spaced armature coils comprising first stationary signaling means and a plurality of rotating detectors for activating said switches; second stationary signaling means for speed control; a plurality of markers on the rotating armature; a speed detector for detecting the speed of the rotating markers and generating a speed feedback signal; means for generating a speed command signal; an error calculator for comparing the speed feedback and speed command signals and generating an error signal; and a controller for controlling the signaling means based on the error signal.

Description:
This application claims priority from U.S. Provisional Application Ser. No. 60/517,256, filed on Nov. 4, 2003. 

   FIELD OF THE INVENTION 
   The present invention relates generally to brushless repulsion motors and, more particularly, to an improved system for controlling the speed of a brushless repulsion motor. 
   INCORPORATION BY REFERENCE 
   A brushless repulsion (BLR) motor generally includes a series of armature-mounted switches for selectively shorting circumferentially spaced armature coils when the coils reach a particular angle with respect to the flux of the stator. Normally, each coil includes a detector for shorting the coils at the predetermined angular position. Such a motor is shown in Haner, U.S. Pat. No. 5,686,805, which is incorporated by reference herein. Details of the operation of the brushless repulsion motor are known in the art and disclosed in this U.S. patent. 
   Haner, U.S. Pat. No. 5,424,625, teaches how to construct a BLR motor and how to regulate its speed by closing armature switches in appropriate rotational positions. Two other Haner patents, U.S. Pat. Nos. 6,049,187 and 6,108,488, teach means of setting and maintaining the speed when load or other conditions change by using a counter mounted on the armature (or rotor) to open and close switches at a set frequency. These three Haner patents are also incorporated by reference herein. 
   BACKGROUND OF THE INVENTION 
   As described in U.S. Pat. No. 5,424,625, for example, the BLR motor is constructed almost like a universal motor used in hand drills, etc. Its stator consists of one or more salient poles whose copper windings are connected directly to the two legs of a single phase, AC line, just like a universal motor. A BLR motor with three pairs of stator poles runs on three-phase power. The armature consists of slotted steel laminations stacked on a shaft. Copper wire is wound into each slot, over the stack end and back into the slot on the opposite side. The number of turns and the wire size vary with the performance desired. The two ends of each coil are connected by a switch, such as a triac or pair of transistors, thus forming an electric circuit. 
   When the stator windings are connected to an AC line, magnetic flux builds up and collapses with the line current. This flux passes directly through the armature and induces a voltage potential on each armature coil. When a coil&#39;s switch is closed, the current flows in that coil as a result of the applied voltage. This produces opposing magnetic flux and thus torque and rotation. When the switch is open current cannot flow and no torque is produced. 
   In a two-pole BLR motor, torque is produced in a clockwise direction when a coil is “on” in a 90 degree sector on one side of a stator pole (the positive torque sector). When turned on in the negative torque sector on the other side of the pole, torque is produced in the opposite direction. So, in a two-pole motor, each coil passes through two positive and two negative torque sectors per revolution. Of course, only the positive torque or the negative torque sectors are activated at any one time. 
   The switches can be opened or closed at will by stationary signal means. The signals can be RF, magnetic, sonic, light, etc. For example, an inexpensive and reliable means is a curved array of infrared light emitting diodes (LEDs) mounted on the motor end-bell. These can be illuminated individually or together. On the rotating armature there is a photo-detector associated with every coil. When a detector “sees” an illuminated LED it closes its switch, which produces current in the coil and flux and torque. By lighting the LEDs in the negative torque sector, reverse rotation can be achieved. 
   When rotating clockwise, lighting only a single LED when the coil has almost completed its arc in the positive torque sector produces little torque and speed. By lighting the entire array, each switch is turned on during its full arc and therefore develops maximum power and speed. Current in an armature coil is highest when the coil is aligned with the stator pole and cuts the maximum number of flux lines. It falls to zero as the coil rotates 90 degrees and leaves that sector. Therefore, switches are generally turned off at or near the end of a sector in order to break minimum current and achieve the maximum efficiency. 
   However, when the coil is thus aligned, all the force is directed along the line from one pole to the other and produces no rotational torque. As the coil rotates it begins to produce torque and reaches its most effective torque producing position at 90 degrees, exactly where the current is zero. The actual torque produced at each rotational angle by the combination of these phenomena and other factors is an asymmetrical curve. It rises sharply from zero at the high current-low torque position (hard neutral) to a peak and then decreases more gradually as it moves 90 degrees toward the end of the positive torque sector (soft neutral), where it again becomes zero. 
   At higher speeds the dynamic interaction between the rotating and stationary magnetic fields tends to shift both the optimum turn-on and turn-off points. As a result, the positive torque sector extends to beyond the 90 degree static limit. This means that a lighted LED at the end of a sector may, under different conditions, produce either positive or negative torque. Therefore, to produce optimum torque and efficiency a speed control scheme must have the flexibility to handle this shift. 
   Thus, there is a need for a system that improves the performance, reliability and cost of a speed-controlled BLR motor. Such improvements include an internal speed and position sensor, mechanical refinements and electronic control means based on timing. 
   BRIEF DESCRIPTION 
   In accordance with one embodiment of the present invention, there is provided a system for controlling the speed of a brushless repulsion motor having a series of switches mounted on a rotating armature for shorting circumferentially spaced armature coils. The system comprise first stationary signaling means and a plurality of rotating detectors for activating said switches; second stationary signaling means for speed control; a plurality of markers on the rotating armature; a speed detector for detecting the speed of the rotating markers and generating a speed feedback signal; means for generating a speed command signal; an error calculator for comparing the speed feedback and speed command signals and generating an error signal; and a controller for controlling the signaling means based on the error signal. 
   In accordance with another embodiment of the present invention, there is provided a system for controlling the speed of a brushless repulsion motor having a series of switches mounted on a rotating armature for shorting circumferentially spaced armature coils. The system comprises a controller mounted on the armature for controlling the switches; a plurality of stationary markers on the stator of the motor; and signaling means and corresponding detecting means on the armature for providing a speed feedback signal to the controller. 
   In accordance with another embodiment of the present invention, there is provided a system for controlling the speed of a brushless repulsion motor having a stator and a series of switches mounted on a rotating armature for shorting circumferentially spaced armature coils. The system comprises a plurality of markers on the armature; a signaling source directed to the markers; a detector for detecting the markers and generating a speed feedback signal; and a controller for controlling the switches. 
   In accordance with another embodiment of the present invention, there is provided a speed control system for a brushless repulsion motor having a stator, an armature, and a series of coil switches for shorting a succession of armature coils. The speed control system comprises a position marker on the armature for determining armature coil position; first signaling means; a position detector for detecting the armature coil position marker via the first signaling means; a plurality of markers on the armature for determining armature speed; second signaling means; a speed detector for detecting the speed of the armature via the second signaling means; and a timer for controlling the speed of the armature and the desired speed of the motor at the precise time as determined by the position of one of the armature coils. 
   In yet another embodiment of the present invention, there is provided a system for controlling the speed of a brushless repulsion motor having a series of switches mounted on a rotating armature for shorting circumferentially spaced armature coils. The system comprises first stationary signaling means and a plurality of rotating detectors for activating said switches; an encoder for detecting the speed and position of the coil switches and generating a speed feedback signal and a position feedback signal; generating means for generating a speed command signal; an error calculator for comparing the speed feedback and speed command signals and generating an error signal; and a timer for controlling the signaling means based on the error signal. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagrammatical view of a two-pole brushless repulsion motor with a speed control system constructed in accordance with the present invention. 
       FIG. 2  is a view similar to  FIG. 1  showing a different speed control system. 
       FIG. 3  is a diagrammatical view of a two-pole brushless repulsion motor featuring the cone of light from an LED. 
       FIG. 4  is a view similar to  FIG. 3  showing an array of LEDs and overlapping cones. 
       FIG. 5  is a diagrammatical view of a two-pole brushless repulsion motor with an alternative speed control system constructed in accordance with the present invention. 
       FIG. 6  is a diagrammatical view of a two-pole brushless repulsion motor showing a variation of the speed control system in  FIG. 6 . 
       FIG. 7  is a diagrammatical view of a two-pole brushless repulsion motor with a speed control system based on concentric rings. 
       FIG. 8  is a diagrammatical view of a two-pole brushless repulsion motor with an alternative speed control system constructed in accordance with the present invention. 
       FIG. 9  is a diagrammatical view of a two-pole brushless repulsion motor showing a variation of the speed control system in  FIG. 9 . 
       FIG. 10  is a diagrammatical view of a two-pole brushless repulsion motor showing a variation of the speed control system in  FIG. 9 . 
       FIG. 11  is a diagrammatical view of a two-pole brushless repulsion motor with an alternative speed control system constructed in accordance with the present invention. 
       FIG. 12  is a diagrammatical view of a two-pole brushless repulsion motor with an alternative speed control system constructed in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals to like elements throughout. 
   A BLR motor  10  with an improved speed control system is illustrated in  FIG. 1 , shown in a view looking axially from an electronic commutator end. The BLR motor  10  in the illustrated example is a single-phase two-pole repulsion motor. A motor stator  12  comprises a pair of diametrically opposed magnetic poles  14  having field windings  16  that typically are connected to 60 HZ single-phase utility power and produce a magnetic field. The stator  12  can be constructed in essentially the same manner as in a conventional universal series motor or a repulsion motor. A rotor (or armature)  18  of the BLR motor  10  can be constructed essentially in the same manner as a conventional universal series motor with certain exceptions or modifications discussed below. The rotor  18  is supported for rotation about a central axis  20  by axially spaced bearings mounted on opposite ends of the stator  12  in a conventional manner. The rotor  18  has a plurality of axial or longitudinal slots (not shown) on its periphery into which are fitted a plurality of generally longitudinal coils  21  terminated on commutator segments or bars. Electrical brushes found in conventional repulsion motors or in universal series motors are eliminated from the construction of the BLR motor  10 . Rather, the BLR motor  10  includes electronic means on the rotor  18  to short the ends of the rotor winding coils  21 , eliminating the need for conventional electrical brushes to do the same. 
   The commutator segments are typically arranged in diametrically opposed pairs. Associated with each pair of segments is an electronic switch circuit  22  mounted on a printed circuit board  24  on the rotor  18 . At appropriate times in the rotation of the rotor  18 , the electronic switches  22  will be individually closed or rendered conductive to short, i.e. electrically connect their respective segments together. With the field windings  16  energized and appropriate commutator segments shorted, the effect is to develop torque and rotation between the rotor  18  and stator  12 . A typical electronic switch  22  comprises a pair of power MOSFET transistors and a triggering device (or detector)  26  such as a phototransistor. When the detector  26  is illuminated by a suitable light source  28 , such as an array of LEDs, it switches on and, in turn, switches on the power transistors through their gates, placing them in a conductive state. 
   The electronic switch  22  is replicated for each pair of segments, but for clarity in the drawings, this replication is not shown. It will be understood that the electronic switches  22  and related energizing circuitry for all of the segment pairs are suitably fixed to the circuit board  24  of the rotor  18  so that the same rotates in unison with the rotor  18 . For heat transfer or other reasons, the components of the electronic switch  22  can be carried on the rotor  18  outside of the stator  12  by interconnecting the same to the segments with wires that run along the rotor shaft, in a slot or central hole, through the associated conventional shaft bearing. 
   When speed begins to deviate from the desired value due to changes in the load or line voltage, heating etc., a speed sensor and a closed-loop speed feedback system can automatically reset the turn-on point to maintain set speed as described below. 
   Thus, in this embodiment, the BLR motor  10  includes an improved speed control system in accordance with the present invention. The speed control system is essentially an inexpensive internal feedback means, as shown in  FIG. 1 . Instead of using a separate, externally mounted and wired tachometer, resolver or encoder, the BLR motor&#39;s unique rotating electronic printed circuit board  24  is used to sense speed and position inexpensively. A stationary magnetic pickup or photo-transmitter speed detector  30  is used to sense an array of markers  32  on the rotating PC board  24 . These markers  32  can be magnets or alternate reflective and non-reflective bars, and they can be placed either flat on the rotating and stationary surfaces or on the peripheries, which eliminates the effect of spacing variations due to end-play of the rotor  18  and wobble of the circuit board  24 . Although not shown, the markers  32  can also be mounted in an upright position circumferentially around the printed circuit board  24  with the detector  30  mounted on the printed circuit board  24  within the periphery of the markers  32 . 
   A speed feedback signal  34  from the speed detector  30  can then be compared with a speed command signal  36  by means of an error calculator  38 , and the difference (or error signal)  40  may be used by a standard LED controller  42  to turn on more or fewer LEDs  28  in the positive torque sector to correct the speed. Of course, the switches  22  are opened or closed by the LEDs  28  as described in the Haner patents described above, for example. Thus, when a detector  26  “sees” an illuminated LED  28  it closes its corresponding switch  22 , which produces current in the coil  21 , along with flux and torque. And by lighting the LEDs  28  in the negative torque sector, reverse rotation can be achieved. 
   Another single position marker  44 , or one at each coil  21 , can be designated to indicate the exact coil position, which is useful for many speed control approaches. In particular, a position detector  46  senses the position marker  44  on the rotating board  24  and sends a position feedback signal  48  to the LED controller  42  to help maintain the set speed. 
   Reference is now made to  FIG. 2  where a BLR motor  50  having an armature-mounted speed control system is shown. The BLR motor  50  is similar in arrangement to that described in connection with  FIG. 1 . However, in this embodiment, the BLR motor  50  is constructed with an array of stationary markers  52 , such as magnets or alternate reflective and non-reflective bars, on the stator  12 . Light from a signaling source  54  such as an LED is reflected back by the markers  52  and detected by a magnetic pickup or photo-transmitter detector  56  mounted on the rotor  18 . The detector  56 , in turn, provides a feedback signal  58  to armature-mounted control  60 , which controls the switch  22 , such as in the approaches described in the Haner patents cited earlier and incorporated by reference. It is to be understood, however, that other types of signaling methods could be used including RF signals. 
   It is to be appreciated by those skilled in the art that this novel concept can also be employed with other types of speed control for the BLR motor, such as varying the input voltage to the field or pulsing the LEDs in phase with the line frequency. 
   While LEDs are generally reliable and inexpensive in controlling the speed of BLR motors, their small size, variable characteristics, as well as other factors may limit their use for precise speed control in some cases. Given their small size (only ⅛″), only about 16 LEDs can be inserted in the 90 degree positive torque sector in a 4″ diameter two-pole motor. Of these, only 12 are used to control speed, as the others are reserved to produce peak torque for short periods of overload. In a four-pole motor with a 45 degree positive torque sector, this is reduced to 8 and 6 devices, respectively. Therefore, the speed can be set only in coarse steps rather than being continuously variable, which is the standard for adjustable speed drives. 
   Reference is now made  FIGS. 3 and 4 , where a conventional BLR motor  70  having a speed control system with a number of LEDs  72  as a light source is shown. Each LED  72  produces a cone of light  74  that may create some additional problems. For instance, each LED  72  is spaced a distance A from a detector  76 , and each cone  74  has a width B. And, as best seen in  FIG. 4 , the LEDs  72  must be spread apart to prevent overlap of the cones  74 , further reducing the number of speed settings available. Also, the width B of the cone  74  varies with voltage, temperature, time in service and with the distance from the stationary LED  72  to the rotating photo-detector  76 . A wider cone  74  would permit the detector  76  to “see” the LED  72  before the coil  78  has rotated to the intended position, thus causing the motor  70  to speed up, while a narrow cone  74  acts in reverse. This problem is accentuated by the fact that each detector  76  also has its own variable cone (not shown). The combination of these factors may make it difficult to achieve accuracy or even repeatability over time using discrete LEDs for position control, even when placed on the periphery to eliminate longitudinal variations. Even with using a closed-loop speed control system such as the one described above, the above limitations may still apply. 
   However, illuminating alternate LEDs  72  can alleviate the speed precision problem. For example, turning on the #5 LED for the first coil and then the #4 and #5 LEDs for the next three coils will produce an average speed as if an LED #4.25 were available. This will be satisfactory for many applications but the cone variability is still present. 
   These limitations of resolution and accuracy can be further improved by various mechanical and electronic means. For example, the use of a timer inexpensively eliminates many of the above limitations imposed by use of discrete LEDs to control the speed of a BLR motor. A timer-based speed control system operates by turning on and off signaling means (e.g., LED, RF or other suitable means), thus closing and opening the switches at the precise time when each coil is in exactly the proper position. Therefore, it provides a more accurate control at every switching cycle than that of position control with coarser resolution. The desired spot can be determined using a standard external encoder or the internal device (rotating markers) described above and a timer to determine location. In such a timer-based speed control system, each switch can be turned off either when its photo-detector passes out of the lighted sector or by the position sensor for maximum flexibility, as described more fully below. 
   Referring now to  FIG. 5 , there is shown an alternative BLR motor  90  constructed with the timer-based speed control system. The motor  90  is similar in arrangement to that described in connection with  FIG. 1  as it pertains to a stator  12  and rotor  18 . The speed control system includes a 1024-line encoder  92  mounted on the rotor  18 . The encoder  92  provides 256 control points in a 90 degree positive torque sector, which is 16 times the resolution of speed setting achievable with discrete LEDs (an angular precision of 0.35 degrees vs. 5.62 degrees). This scheme requires only one signaling device  94 , such as a continuous arc of light, per sector, but an LED array still works. A speed feedback signal  96  from the encoder  92  can then be compared with a speed command signal  98  by means of an error calculator  100 , and the difference (or error signal)  102  may be used by a timer  104  to turn on the signaling source  94  in the positive torque sector earlier or later to correct the speed at the correct time. Additionally, the encoder  92  may provide a position feedback signal  106  to the timer  104 . By using the encoder  92  to sense both actual speed and coil position, a closed loop control can then advance or delay the actual turn-on point in the positive torque sector required to maintain a set speed with changing load or other conditions. 
   If greater precision is required or if it is less expensive to use a coarser encoder, then the desired turn-on point can be extrapolated, based on the measured speed at the last encoder marker (or the average of the last several markers). That is, the timer  104  calculates, based on the set and actual speeds, how far in distance and time beyond the latest encoder pulse the turn-on should occur. It then waits the number of microseconds until the coil  21  has moved precisely to that point when it activates the signaling means. This can provide a 10:1 or even a 100:1 refinement in resolution. For practical purposes, this provides an infinitely variable speed alignment. 
     FIG. 6  shows an alternative BLR motor  110 . The motor  90  is similar in arrangement to that described in connection with  FIG. 6 , except that in this embodiment, a stationary magnetic pickup or photo-transmitter speed detector  112  is used to sense an array of markers  114  on the rotating board  24 . A speed feedback signal  116  from the speed detector  112  can then be compared with a speed command signal  118  by means of an error calculator  120 , and the error signal  122  may be used by the timer  104  to turn on the signaling source  94  in the positive torque sector earlier or later to correct the speed at the correct time. Another single position marker  124 , or one at each coil  21 , can be designated to indicate the exact coil position. In particular, a position detector  126  senses the position marker  124  on the rotating board  24  and sends a position feedback signal  128  to the timer  104 . The timer  104 , in turn, sends a control signal  130  to the signaling source  94 , which activates the switches  22  via the detectors  26 . 
   The above timing schemes are described as if only one coil were activated at a time. However, in order to achieve maximum power and optimum efficiency, multiple coils must be turned on simultaneously. For example, each coil-end of a four coil rotor spans 45 degrees, so three coils can be on and producing torque at once in the 90 degree or greater positive torque sector in a two-pole motor. 
   This can be achieved in several ways, including by using separate light sources, such as concentric LED rings. Referring now to  FIG. 7  where an alternative BLR motor  140  is shown. The motor  140  is constructed with concentric LED rings  142   a–d , one for each coil. These concentric LED rings  142   a–d  can give flexible, independent control over 360 degrees. 
   Reference is now made  FIG. 8  where an alternative BLR motor  150  is shown. The motor  150  is similar in arrangement to that described in connection with  FIG. 1  as it pertains to a stator  12  and rotor  18 . More particularly, a multi-coil controller  152  generates coded signals  154  which are transmitted from the stator  12  by an RF transmitter  156  or other means in the form of pulses or distinct frequencies can be received by an RF receiver  158  and decoded by a decoder  160  on the rotor  18 . The decoded signals are sent to an armature-mounted control  162  to control the switches  22  as desired. A first signal can cause one of the switches  22  to turn and latch on and the second signal will turn the switch  22  off any desired time/point, thus providing the ability to optimize performance under shifting dynamic conditions. 
   Reference is now made  FIG. 9  where an alternative BLR motor  170  is shown. The motor  170  is similar in arrangement to that described in connection with  FIG. 8  except that the coded signals  154  are received and decoded by a tuned receiving coil  172  on the rotor  18 . Again, the decoded signals are sent to the armature-mounted control  162  to control the switches  21 , as desired. 
   Reference is now made  FIG. 10  where an alternative BLR motor  180  is shown. The motor  180  is similar in arrangement to that described in connection with  FIG. 9 . However, in this embodiment, each switch  22  has a corresponding tuned receiving coil  182  on the rotor  18 . Thus, the coded signals  154  are received and decoded by the tuned receiving coils  182 . 
   Referring now to  FIG. 11  where an alternative BLR motor  190  is shown. In this embodiment, multiple signaling zones in a sector, such as LED arrays A, B, and C provide independent control for the BLR motor  190 , which has four coils  192 . In such a four-coil motor, three zones, A, B, C, control three possible simultaneously activated coils  192 . Each zone may be 35 to 40 degrees to provide more than 90 degrees of control. For example, when minimum power is required, only zone A will be lit at the proper time and so only one coil  192  will be activated. Each activated coil  192  and, if appropriate, the zone A signaling source (i.e., the LEDS) will be turned off at the proper time point as determined by an encoder position sensor. 
   For more power, the LEDs in zone B will be lit at the proper time and turned off when its active coil (not shown) enters zone A, which will remain lit continuously. Two coils will be activated simultaneously for a period and the coil moving from zone B into A will remain on. To develop maximum power, torque must be applied in the entire positive torque sector. Thus, zone C will be lit to energize each switch  192  as it enters that zone and it will be kept on through the rest of the sector as zones B and A will remain lit all the time. 
   Reference is now made  FIG. 12  where an alternative BLR motor  200  is shown. The motor  200  is similar in arrangement to that described in connection with  FIG. 1  as it pertains to a stator  12  and rotor  18 . In this embodiment, timer control without speed feedback is used. This approach requires discrete signals to control each of several coils  21  as described above. The switches  22  are turned on and off by a timer control means  202  mounted on the rotor  18  at precisely the time interval that coincides with the rotational speed desired times the number of switches required per revolution. In a 2 pole-4 coil motor, this is 8 pulses/revolution, since each coil must be switched on at each pole. At 1800 rpm or 30 revolutions/second it would be 240 pulses/second. 
   Rotation rate is thus controlled with pulses like a quartz watch. Once the motor is operating at the set speed, it will self-correct without speed feedback if a change occurs. For example, if the load decreases or the voltage increases the motor  200  will tend to speed up. But this will cause the next coil  21  to have moved farther than intended into the positive torque sector by the time the turn-on is signaled. It will therefore be further down the torque-position curve and also in the positive torque sector for a shorter arc than intended, both of which produce less power and slow it down. Or it may actually enter the negative torque sector and produce reverse torque, which will decelerate it even faster. 
   If the load increases or the voltage drops, then the rotor  18  will momentarily be turning at less than set speed. The next coil  21  will then be turned on when it is less far into the positive torque sector and higher on the torque-position curve than intended and will thus speed up. 
   The motor  200  will also adjust its rotational rate in the same manner when the speed command is changed. Start-up occurs just like any other increase in set speed. Because the motor  200  may not be as responsive under all circumstances as one with speed feedback, it will be helpful to change commands on a ramped rather than a step basis. Also, although speed feedback is not required, providing position feedback will improve its performance. Knowing the rotor&#39;s rotational position enables the timer control means  202  to turn on coils  21  when they are favorably located and to adjust their turn-off to the variable soft neutral point to avoid breaking considerable current. 
   An accurate, responsive, flexible and inexpensive control can be achieved by modifying three elements described above. First, the timing control means  202  is mounted on the rotor  18  connected directly to all the switches  22  and can tune each one on and off as desired over an extended positive torque sector without the need for photo (or other) detectors associated with each switch  22 . 
   Second, a single transmitter-receiver system, such as an RF transmitter  204  and an RF receiver  206  can send a coded signal from a speed controller  208  on stator  12  to the rotor  18  with commands to the timer  202  to set the speed. It is to be appreciated by those skilled in the art that other transmitter-receiver systems could be used, including light, IR, or other similar systems. This eliminates the need for multiple LEDs and utilizes a very small bandwidth since it operates only when the speed command is changed. 
   Third, an encoder  210  with the markers on the stator  12  and an emitter-detector (not shown) on the rotor  18  can provide speed and position information to the closed-loop system on the rotor  18  that maintains desired speed. 
   It is to be appreciated that this approach can also be used without the speed sensor in the manner described above. 
   Thus, the embodiments of the invention described above provide improved performance, reliability and cost plus great flexibility in designing BLR motors to meet the needs of a wide range of applications. Implementing any of these embodiments with one or more microprocessors and software adds even greater versatility. 
   While the invention has been shown and described with respect to particular embodiments thereof, this is for the purpose of illustration rather than limitation, and other variations and modifications of the specific embodiments herein shown and described will be apparent to those skilled in the art all within the intended spirit and scope of the invention. Accordingly, the patent is not to be limited in scope and effect to the specific embodiments herein shown and described nor in any other way that is inconsistent with the extent to which the progress in the art has been advanced by the invention.