Abstract:
Apparatus for connecting a motor controller to an electrical motor, said apparatus comprising:
       a motor interface board;   a mounting mechanism for mechanically connecting said motor interface board to the electrical motor;   at least one input lead for electrically connecting said motor interface board to at least one of an electrical power source and an electrical signal source;   at least one output lead for electrically connecting said motor interface board to the electrical motor; and   at least one connector for mechanically and electrically connecting said motor interface board to the motor controller.

Description:
REFERENCE TO PENDING PRIOR PATENT APPLICATION 
       [0001]    This patent application claims benefit of pending prior U.S. Provisional Patent Application Ser. No. 61/911,558, filed Dec. 4, 2013 by Barrett Technology, Inc. and Brian Zenowich et al. for MEANS TO CREATE AN ULTRAMINIATURE MOTOR AMPLIFIER WITH INTEGRATED POSITION SENSING (P3) (Attorney&#39;s Docket No. BARRETT-4 PROV), which patent application is hereby incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to electrical motors in general, controllers for electrical motors, and methods and apparatus for connecting controllers to electrical motors. 
       BACKGROUND OF THE INVENTION 
       [0003]    Barrett Technology, Inc. of Newton, Mass., USA has developed an ultracompact, high-performance motor controller (UCHPMC) which provides rotor-position sensing, electronic commutation and motor-current amplifiers with precise current sensing in a cylindrical module measuring only 19 mm (diameter)×8 mm (tall), roughly matching the diameter of the smallest ultracompact, high-performance brushless DC motors. See, for example, U.S. Pat. Nos. 7,511,443; 7,854,631; and 7,893,644. 
         [0004]    This small size UCHPMC is especially difficult to achieve with low cost because the need for affordability dictates that only conventional printed circuit board (PCB) techniques be used (i.e., no hidden or blind vias or microvias); and the silicon integrated circuits (ICs) must be conventionally packaged (e.g., no flip-chip techniques with special wire bonding), although moderate layer counts (e.g., 6 layers) are possible. 
         [0005]    The UCHPMCs of Barrett Technology, Inc. are especially convenient because the motor controller and the means for sensing the instantaneous motor position are included in the same module, thereby eliminating a large number of electrical conductors and electrical connectors. Furthermore, the small size of the UCHPMCs allows them to be mounted to the back (i.e., body) of a brushless DC motor in the volume of space normally reserved for just the rotor-position sensing feature, hovering just above a tiny magnetic or optical target that spins with the rotor of the motor (it is the detection of the tiny magnetic or optical target which provides the rotor-position sensing feature of the UCHPMC). 
         [0006]    The UCHPMCs of Barrett Technology, Inc. provide a significant advance in the field of motor controllers. However, even with the UCHPMCs of Barrett Technology, Inc., there remain several problems with the application of the UCHPMC modules. For one thing, the UCHPMC modules require a rigid and robust mechanical connection between the UCHPMC body and the body of the motor in order to permit effective rotor-position sensing. For another thing, the scheme for (1) making robust electrical connections between the UCHPMC and the motor windings (and any thermistors or redundant Hall position sensors) coming from the motor body, and (2) making robust electrical connections between the UCHPMC and the bussed power and bussed serial communications, require a large amount of hand soldering. The manual nature of these solder connections allows occasional cold solder joints, which can result in inconsistent quality control. Furthermore, where electrical connection failures occur, these failures often occur in the field after the systems have been tested and shipped to the customer. At that point, the electrical connection failures can be difficult and time-consuming to remedy. In addition, where the UCHPMC fails in the field, replacing the UCHPMC requires that the UCHPMC module be disconnected (both mechanically and electrically) from the back (i.e., body) of the motor. This can be inconvenient and time-consuming to effect, particularly when the motor and UCHPMC module are positioned deep within a larger assembly (e.g., within the interior of a robot or robot limb). 
         [0007]    Thus there is a need for a new method and apparatus for connecting an ultracompact, high-performance motor controller (UCHPMC) to an ultracompact, high-performance brushless DC motor which provides reliable mechanical and electrical connections between the UCHPMC and the motor, and which allows the UCHPMC to be quickly and easily “swapped out” in the event that the UCHPMC needs to be replaced. 
         [0008]    There is also a need for a new method and apparatus for connecting other motor controllers to electrical motors which provide reliable mechanical and electrical connections between the motor controller and the electrical motor, and which allows the motor controller to be quickly and easily “swapped out” in the event that the motor controller needs to be replaced. 
         [0009]    There is also a need for a new method and apparatus for interfacing a given motor controller, such as a specific UCHPMC, to a large family of different motors without requiring changes to the UCHPMC component itself. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention comprises the provision and use of a novel method and apparatus for connecting an ultracompact, high-performance motor controller (UCHPMC) to an ultracompact, high-performance brushless DC motor which provides reliable mechanical and electrical connections between the UCHPMC and the motor, and which allows the UCHPMC to be quickly and easily swapped out in the event that the UCHPMC needs to be replaced. 
         [0011]    The present invention also comprises the provision and use of a novel method and apparatus for connecting other motor controllers to electrical motors which provide reliable mechanical and electrical connections between the motor controller and the electrical motor, and which allows the motor controller to be quickly and easily swapped out in the event that the motor controller needs to be replaced. 
         [0012]    The present invention also comprises a new method and apparatus for interfacing a given motor controller, such as a specific UCHPMC, to a large family of different motors without requiring changes to the UCHPMC component itself. 
         [0013]    In one preferred form of the present invention, there is provided apparatus for connecting a motor controller to an electrical motor, said apparatus comprising: 
         [0014]    a motor interface board; 
         [0015]    a mounting mechanism for mechanically connecting said motor interface board to the electrical motor; 
         [0016]    at least one input lead for electrically connecting said motor interface board to at least one of an electrical power source and an electrical signal source; 
         [0017]    at least one output lead for electrically connecting said motor interface board to the electrical motor; and 
         [0018]    at least one connector for mechanically and electrically connecting said motor interface board to the motor controller. 
         [0019]    In another preferred form of the present invention, there is provided apparatus comprising: 
         [0020]    an electrical motor; and 
         [0021]    apparatus for connecting a motor controller to said electrical motor, said apparatus comprising:
       a motor interface board;   a mounting mechanism for mechanically connecting said motor interface board to said electrical motor;   at least one input lead for electrically connecting said motor interface board to at least one of an electrical power source and an electrical signal source;   at least one output lead for electrically connecting said motor interface board to said electrical motor; and   at least one connector for mechanically and electrically connecting said motor interface board to the motor controller.       
 
         [0027]    In another preferred form of the present invention, there is provided a method for connecting a motor controller to an electrical motor, said method comprising: 
         [0028]    mechanically mounting a motor interface board to the electrical motor; 
         [0029]    electrically connecting at least one input lead of said motor interface board to at least one of an electrical power source and an electrical signal source; 
         [0030]    electrically connecting at least one output lead of said motor interface board to the electrical motor; and 
         [0031]    mechanically and electrically connecting said motor interface board to the motor controller using at least one connector. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]    These and other objects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts, and further wherein: 
           [0033]      FIG. 1  is a schematic view showing a motor interface board (MIB) connecting an ultracompact, high-performance motor controller (UCHPMC) to an ultracompact, high-performance brushless DC motor; 
           [0034]      FIG. 2  is a schematic view like that of  FIG. 1 , except showing the UCHPMC removed from the MIB; 
           [0035]      FIG. 3  is a schematic view showing how a single MIB may be used to connect multiple UCHPMCs to multiple motors; 
           [0036]      FIG. 4  is a schematic view like that of  FIG. 3 , except showing that the MIB may comprise multiple stiff board segments connected by flexible board segments; and 
           [0037]      FIG. 5  is a schematic view showing how the MIB can mount different motor controllers to different motors. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0038]    The present invention comprises the provision and use of a novel method and apparatus for connecting an ultracompact, high-performance motor controller (UCHPMC) to an ultracompact, high-performance brushless DC motor which provides reliable mechanical and electrical connections between the UCHPMC and the motor, and which allows the UCHPMC to be quickly and easily swapped out in the event that the UCHPMC needs to be replaced. 
         [0039]    The present invention also comprises the provision and use of a novel method and apparatus for connecting other motor controllers to electrical motors which provide reliable mechanical and electrical connections between the motor controller and the electrical motor, and which allows the motor controller to be quickly and easily swapped out in the event that the motor controller needs to be replaced. 
         [0040]    The present invention also comprises a new method and apparatus for interfacing a given motor controller, such as a specific UCHPMC, to a large family of different motors without requiring changes to the UCHPMC component itself. 
         [0041]    More particularly, in one preferred form of the present invention, the invention comprises the provision and use of a motor interface board (MIB) which permits an ultracompact, high-performance motor controller (UCHPMC) to be mechanically and electrically interfaced with a large number of commercially available electrical motors—the MIB acts as both a mechanical and electrical interface between the UCHPMC and the electrical motor, in a very small space, using the motor manufacturer&#39;s (or original equipment manufacturer&#39;s) choice of electrical connectors, wire gauges, sensors, I/O, and mechanical mounts. 
         [0042]    Thus, the motor interface board (MIB) provides a fast, easy and inexpensive solution to the task of providing mechanical and electrical connections between the UCHPMC and the electrical motor, and can be used in substantially any situation where a motor controller is to be attached directly to a motor body. 
         [0043]    Integrated circuits and other active electronic elements contained in a UCHPMC module are eventually prone to failure. While it is generally not practical to repair a damaged UCHPMC, it is of great benefit to allow the user to replace a damaged UCHPMC module easily with a spare in the field. The MIB has, itself, no active electronics (i.e., it is essentially a printed circuit board with electrical traces and electrical and mechanical connectors) and so the MIB can be permanently attached (mechanically and electrically) to the body of a motor at low cost, without fear of component failure and subsequent need for replacement. At the same time, however, in the event that the UCHPMC module needs replacement, the MIB permits the replacement UCHPMC to be quickly and easily connected, both mechanically and electrically, to the motor. 
         [0044]    More particularly, and looking now at  FIGS. 1 and 2 , there is shown a motor interface board (MIB)  5  formed in accordance with the present invention. MIB  5  is intended to connect an ultracompact, high-performance motor controller (UCHPMC)  10  to a motor  15  (preferably an ultracompact, high-performance brushless DC motor), whereby to provide mechanical and electrical connections between the two components. In one preferred form of the invention, MIB  5  comprises a printed circuit board which is mechanically mounted to motor  15  via a mount  20 , with mount  20  being secured to motor  15  via screws  25  and with MIB  5  being secured to mount  20  via screws  30 . Wires  35  connect the traces (not shown) of MIB  5  to bus power supplies and CANbus communications, and wires  40  connect the traces (not shown) of MIB  5  to the motor phase leads and ground on the motor chassis. A connector  45  (which is connected to the traces, not shown, of MIB  5 ) mates with a counterpart connector  50  on UCHPMC  10  (e.g., so as to establish a high power electrical connection between MIB  5  and UCHPMC  10 ), and a connector  55  (which is connected to the traces, not shown, of MIB  5 ) mates with a counterpart connector  60  on UCHPMC  10  (e.g., so as to establish a low power electrical connection between MIB  5  and UCHPMC  10 ). Preferably connector  45  on MIB  5  and counterpart connector  50  on UCHPMC  10  comprise a plug-type (e.g., female-male) connection, and preferably connector  55  on MIB  5  and counterpart connector  60  on UCHPMC  10  comprise a plug-type (e.g., male-female) connection, whereby to provide robust mechanical and electrical connections between the elements. An opening  65  in MIB  5  exposes the rotary shaft  70  of motor  15 , such that the rotational disposition of motor shaft  70  may be read by a reader  75  provided on UCHPMC  10 . By way of example but not limitation, a magnet  80  may be attached to shaft  70  and read by an appropriate magnetic reader  75  on UCHPMC  10 . Alternatively, an optical pattern may be attached to shaft  70  and read by an appropriate optical reader on UCHPMC  10 . 
         [0045]    In one construction, UCHPMC  10  may comprise two printed circuit boards  85 ,  90 , where board  85  is a “high power” board and board  90  is a “signals” board, with boards  85 ,  90  having appropriate connections therebetween as is known in the art. 
         [0046]    In one preferred manner of use, MIB  5  is mechanically and electrically connected to motor  15 , and then UCHPMC  10  is mechanically and electrically connected to MIB  5 . 
         [0047]    The component cost of the MIB  5  is driven primarily by the low-cost connectors (e.g., connectors  45  and  55 ) that are mounted to MIB  5 . As noted above, connectors  45 ,  55  mate with connectors  50 ,  60 , respectively on UCHPMC  10 . Note that MIB connectors  45 ,  55  are strategically positioned on MIB  5  in orientations that perfectly align the UCHPMC module  10  to MIB  5  and hence appropriately align the UCHPMC  10  to motor  15 , i.e., so that reader  75  is properly disposed relative to motor shaft  70 . Note also that any number of connectors may be used to mechanically and electrically connect UCHPMC  10  to MIB  5 , as long as the connectors are correctly geometrically placed to ensure appropriate mechanical and electrical connection between UCHPMC  10  and MIB  5 , including appropriate positioning of reader  75  of UCHPMC  10  relative to motor shaft  70  of electrical motor  15 . It will be appreciated that having at least a pair of connectors  45 ,  55 , spread apart from each other in the manner shown, gives the mechanical connection between UCHPMC  10  and MIB  5  better stability. In the case of only two MIB connectors  45 ,  55 , it can be desirable to have one of the connectors  45 ,  55  be relatively long (e.g., approximately ½ the diameter of MIB  5 ) for good mechanical stability. Alternatively, if using short connectors, it can be desirable to use at least three connectors, which may be disposed near the periphery of MIB  5 . For example, three connectors can be placed 120-degrees apart, forming a tripod, again for good mechanical stability. In one preferred embodiment, connector  45  of MIB  5  comprises a female connector and connector  50  of UCHPMC  10  comprises a male connector, and serves to provide power-level connections, and connector  55  of MIB  5  comprises a male connector and connector  60  of UCHPMC  10  comprises a female connector, and serves to provide signal-level connections. 
         [0048]    The compact nature of the UCHPMC  10  makes the MIB concept even more valuable because its mass (2.5 grams for Barrett Technology&#39;s newest UCHPMC) is significantly less than the pull-out strength of the connectors  45 ,  50  and  55 ,  60 . In the present reduction to practice, the UCHPMC weighs 2.5 grams and the pull-out strength of the connectors  45 ,  50  and  55 ,  60  is more than 250 grams. Under these circumstances, it would take in excess of 100 g&#39;s of shock loading, acting in a worst-case direction, to cause the UCHPMC  10  to become unintentionally separated from the MIB  5 . However, intentional separation is well within a human&#39;s finger strength. It will be appreciated that the pull-out strength of the connectors used to mechanically and electrically connect UCHPMC  10  to MIB  5  will vary in accordance with the configuration (e.g., construction and number) of the connectors. In general, it is believed that, for most applications, it will be adequate if the connectors are capable of withstanding shock loading on a given motor controller of 10 g&#39;s or more. 
         [0049]      FIGS. 1 and 2  show how MIB  5  is used to mechanically and electrically connect the UCHPMC module  10  with a motor  15 . In one preferred form of the invention, the motor&#39;s manufacturer (or the original equipment manufacturer) creates a motor-specific MIB  5  which is mechanically and electrically connected to a motor, as shown in  FIGS. 1 and 2 . 
         [0050]    However, the MIB  5  need not host only one motor. Rather, the tail ends (i.e., bodies) of two or more motors  15  (see  FIG. 3 ) can be ganged together as an array onto one large MIB  5 , where the MIB  5  carries appropriate connectors (e.g., connectors  45 ,  55 ) for each of the motors which is to be hosted by MIB  5  (i.e., so as to allow appropriate electrical and mechanical connection of a UCHPMC  10  to a motor  15  via the intervening large MIB  5 . As a result of this construction, the large MIB  5  will appropriately connect each of the motors  15  to a UCHPMC  10 , whereby to provide each of the motors  15  with appropriate electrical power and communications (CANbus, EtherCAT, or some other type) connections. In this case, the 4-, 5-, or 6-wire bus carrying power and communications need not generate a complex wiring harness, with many difficult-to-manufacture Y-junctions—instead, creating the necessary Y-junctions on a printed circuit board in the MIB  5  is trivial. In this case, one only needs to carry the 4-, 5-, or 6-wire bus to the edge of the single MIB  5 . 
         [0051]    Furthermore, for the case of two or more motors  15  being connected on one MIB  5 , the MIB  5  need not be a single stiff printed circuit board (e.g., such as is shown in  FIGS. 1-3 ), but can easily be made up of many stiff board segments connected together via flexible board (sandwiched Mylar and copper traces) segments. See  FIG. 4 , where MIB  5  comprises a plurality of stiff printed circuit boards  5 A connected together via flexible board segments  5 B. Creating this type of flex printed circuit board is a well-known and cost-effective technique. In the case of two or more motors  15  being mounted to a single MIB  5 , this flex-board technology allows the motors  15  to have any angular displacements relative to one another and allows relative motions among the motors. There are even cases where the motors remain fixed and parallel, but spread significantly far apart with obstacles and constraints between them, such that using a MIB  5  comprising a single rigid board would not be practical. In this case, forming MIB  5  with multiple stiff boards  5 A connected together by flex boards  5 B provides a good solution, since it allows the components of MIB  5  to “snake” among various obstacles and constraints. 
         [0052]    Once the MIB  5  is attached to the motor or motors  15 , then a UCHPMC module  10  literally plugs onto the MIB  5  at the tail-end (i.e., body) of each motor. 
         [0053]    In the preferred embodiment, the motor manufacturer (or the original equipment manufacturer) also bonds a tiny N-S “button” magnet  80  (e.g., 6 mm in diameter×2.5 mm in height) to the exposed tail end of the motor shaft  70  ( FIG. 2 ) that acts as a rotating target which an array of Hall sensors (i.e., magnetic reader  75 ) on the UCHPMC module  10  can track in real-time to determine the instantaneous rotor position, even at high velocities of several thousand RPM. This rotor-position signal, along with an externally-commanded motor torque, position, or velocity, is then used in calculations on the Digital Signal Processor (DSP) carried by the UCHPMC  10  that determines the correct instantaneous currents for each of the three motor phases of motor  15 . To read the rotor-position properly requires the design of the MIB  5  to align and center the magnetic reader  75  of UCHPMC module  10  on the motor axis at a specified offset distance from the face of the magnet  80 . This may be ensured by the use of appropriate connectors (such as the connectors  45 ,  50  and  55 ,  60 ) which are used to mechanically and electrically connect UCHPMC module  10  to MIB  5 . Fortunately, the tolerances of such rotor-position sensors are well within the tolerances of the connectors used to connect UCHPMC module  10  to MIB  5 . 
         [0054]    The MIB concept discussed above is applicable with both large and small motors. To operate the larger motor shown in  FIG. 5  at its maximum capacity requires a motor controller more substantial than Barrett&#39;s existing UCHPMC. One can utilize a larger capacity motor controller module and plug it into an appropriate MIB. 
         [0055]    Alternatively, as show in  FIG. 5 , the UCHPMC  10  can be separated into two components (e.g., Power PCB  85  and Signal PCB  90 ), and use the existing Signal PCB  90  and attach it to a larger “combined MIB  5  and Power PCB  85 ” board  95  using similar UCHPMC-to-MIB connections. In other words, in this form of the invention, MIB  5  can be combined with Power PCB  85 . 
         [0056]    The larger board  95  can handle larger currents with larger connectors  100 ,  105  and larger MOSFETS  110 , while the existing UCHPMC Signal Board  90  remains identical across motor families. 
       Modifications 
       [0057]    It should be understood that many additional changes in the details, materials, steps and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the present invention, may be made by those skilled in the art while still remaining within the principles and scope of the invention.