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BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related to movable barrier operators and more particularly, to the control of a motor for driving a movable barrier such as a garage door. 
     2. Background Description 
     Movable barrier operators and, more particularly, garage door operators are well known and have become very sophisticated to provide users with increased convenience and security. Such barrier movement operators may move barriers such as gates and garage doors which have a relatively large mass which brings into play a relatively large inertia. In order to overcome such inertia electric motors of significant power are used to move the barrier. Thus, a system exists in which an object of relatively large inertia is being powered by a motor of relatively large power. Barrier operator safety is achieved by providing a plurality of sensors to the operation of the barrier and a control method which stop or reverse barrier movement according to the condition sensed. 
     It is common for barrier operators to employ A.C. induction motors to power barrier movement. Such motors include some arrangement of switched start windings and/or switched capacitors to urge the motor into rotation in a selected direction. When a barrier is being moved in a first direction and a safety condition is sensed, known arrangements rapidly enable the starting of motor rotation to reverse direction of the barrier. Such enabling may be constant or it may be pulsed to first slow the barrier then cause it to reverse direction. 
     Reversing the direction of barrier movement by beginning a reverse motor starting process creates noise and vibration from the motor. The noise, by itself is an annoyance to those nearby while the vibration may shorten the life of the barrier and operator system. A need exists for improved methods and apparatus for reversing the direction of barrier travel in a barrier operator system. 
     The present invention provides a plurality of motor reversal algorithms and selects one of the algorithms for use depending on the type of reversal need sensed. The actual rotation speed of the motor may be sensed and be used to decide which algorithm to use and/or how a selected algorithm is to be employed. For example, when the sensed need indicates that the barrier may be contacting an obstruction, a relatively rapid reversal may be attempted. For protection of property and other reasons, the increased vibrations may be tolerated. The rapid reversal may be moderated by the sensed RPM during the reversal process. Also, for example, when a sensed reversal condition does not indicate actual contact (called non-contact) a second algorithm which allows a longer time to complete the reversal may be used. The second algorithm reduces the noise and harmful vibrations of immediate reversal and may also be moderated by sensed motor RPM during the reversal process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other objects, aspects and advantages will be better understood from the following detailed preferred embodiment description with reference to the drawings, in which: 
         FIG. 1  illustrates a barrier movement operator connected to move a garage door; 
         FIG. 2  is an example of a controller for a barrier movement operator; 
         FIG. 3  shows a preferred embodiment of drive motor according to the present invention; 
         FIG. 4  is a generalized block diagram of a motor and motor control apparatus; and 
         FIG. 5  is a flow diagram of the processes of control for motor reversal. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, and more particularly,  FIG. 1  shows an example of a movable barrier operator or garage door operator (GDO) according to the present invention, generally referred to by numeral  100 . The preferred GDO  100  includes a preferred embodiment drive motor  150  ( FIG. 2 ) and a control circuit  208  ( FIG. 2 ) controlling GDO operation in a head unit  102  that is mounted to the ceiling of a garage  104 . A rail  106  extends from the head unit  102 . A trolley  108  is releasably attached to the rail  106  and includes an arm  110  extending to a multiple paneled garage door  112  positioned for movement along a pair of door rails  114  and  116 . The GDO system  100  includes at least one hand-held remote control transmitter unit  118  adapted to send signals to an antenna  120  on the head unit  102 . Signals from the antenna  120  are provided to the control circuit in the head unit  102 . An external remote control pad  122  is positioned on the outside of the garage and includes multiple buttons thereon for communicating via radio frequency transmission with the control circuit in the head unit  102 . A wall switch module  124  is mounted on a wall of the garage. The wall switch module  124  is a wired remote control connected to the control circuit in the head unit  102  by a wire  126 . The wall switch module  124  may include a light switch  130 , a lock switch  132  and a command switch  134 . An optical emitter  138 , preferably emitting an infrared (IR) beam, is connected via a power and signal line  140  to the control circuit in the head unit  102 . An optical detector  142 , disposed opposite the optical emitter  138  and receiving the IR beam, also is connected by a wire  144  to the control circuit in the head unit  102 . The optical transmitter/detector  138  and  142  serve to sense if an obstruction is present in the barrier opening. A door edge detector  117  is also deployed on the leading edge (bottom) of door  112  to detect contact of the door with an obstruction. Door edge detector  117  may communicate wirelessly with an edge detector receiver  231  of the barrier movement controller. As illustrated the barrier movement operator of  FIG. 1  also includes a motion sensor  119  which communicates with the controller of the head end unit  102  via a path  121 . 
     Controller  208  reviews the many inputs and identifies whether a moving barrier should be reversed. For example, the motion detector  119  may detect motion in the garage or the obstacle detector  214  may detect an obstacle in the door opening, signaling a possible unsafe condition if the door  112  is allowed to continue closing. These detected conditions are examples of non-contact conditions, in response to which the direction of travel of the door should be reversed. They are referred to as non-contact because although they raise safety concerns, there is no indication that the moving barrier has struck or contacted an obstruction. Other inputs to controller such as the tachometer  226  input and the door edge detector  231  input signals which are called contact conditions because they may represent actual contact of the moving barrier with an obstacle. The contact conditions may represent a more immediate safety concerns than non-contact conditions and different arrangements to those of non-contact conditions for barrier reversal are provided for them. 
       FIG. 2  is an example of a controller  200  controlling a drive motor  150  such as in  FIG. 3 . The controller  200  is powered by a power supply  202  that converts alternating current from a line alternating current source, such as 110 volt AC, to required levels of DC voltage. The controller  200  is mounted in the head unit, e.g., head unit  102  of  FIG. 1 , with antenna  120  attached to receiver  204  which is coupled via a line  206  to supply demodulated digital signals to a microcontroller  208 . The microcontroller  208  is also coupled by a bus  210  to a non-volatile memory  212 , which stores user codes, and other digital data related to the operation of the control unit  200 . Emitter  138  and infrared detector  142  form an obstacle detector  214  and power and signal lines  140 ,  144  form an obstacle detector bus  218  connected to microcontroller  208 . The obstacle detector bus  218  includes lines  140  and  144 . The wall switch module  124  is connected via wire  126  to the microcontroller  208 . The microcontroller  208 , in response to switch closures and received codes, sends signals over a relay logic line  220  to a relay logic module  222  connected to drive motor  150  which has a power take-off shaft  216  from the rotor coupled to the transmission of the garage door operator  100  of  FIG. 1 . A tachometer  226  is coupled to the drive motor  150  and provides an RPM signal on a tachometer line  228  to the microcontroller  208 ; the tachometer signal provides an indication of the speed at which the door is being driven. The apparatus also includes up and down limit switches  230 , respectively sensing when the door  112  is fully open or fully closed. The limit switches  230  are connected to microcontroller  208  by leads  232 . A light  234  is controlled by microcontroller  208  through logic module  222 . Edge detector receiver  231  detects contact of the barrier with an obstruction, as sensed by door edge  117 , and communicates such with controller  208  via a bus  233 . Similarly, motion detector  119  may detect motion in the garage and communicate such to controller  208 . 
       FIG. 3  shows an embodiment of drive motor  150  which acts a switched capacitor start single phase motor the control for which comes from controller  208 . The motor  150  includes two coils or windings  152 ,  154  in the stator. The common connection of the two windings  152  and  154  is connected to ground or a neutral reference voltage terminal  151  of common 110 VAC household line. Capacitor  158  connected across terminals at the opposite ends of the two windings  152 ,  154  by a start relay  184  the state of which is set by controller  208  acting through relay controls  155 . Line current  153  is provided through a power relay  166  to a direction relay  168  which selectively passes line current directly to either side of capacitor  158  and one of windings  152 ,  154 . In this embodiment providing line current to winding  152  drives the garage door operator in the up direction and providing line current to winding  154  drives the operator in the down direction. 
     When the garage door operator is activated to drive the door down, e.g., by pressing a button on a remote; the controller  208  acting through relay control  155  closes power relay  166  and controls direction relay  168  to connect line current to coil  154  at capacitor  158 . To start the motor, relay  184  is closed and capacitor  158  passes a current out of phase with the line current to coil  152 . As a result, the motor  150  drives the garage door down. In normal operation controller  208  opens relay  184  after a predetermined period of time. When the garage door operator is activated, again, the control circuit closes power relay  166  and direction relay  168  switches to connect power to coil  152 . As before, relay  184  is closed for a predetermined period of time to start the motor  150 . 
       FIG. 3  represents the control of a switched capacitor induction motor. Different types of motors such as a permanent split capacitor, DC motor etc. may be employed to achieve similar movement of a barrier.  FIG. 4  is a generalized block diagram representing that other types of A.C. induction motors may be employed provided that power and direction can selectively be controlled by controller  208  and that the start sequence may also be controlled by the controller. 
     During operation, the reversal of direction of barrier travel may be needed. The present system comprises different control algorithms for door reversal depending upon the type of reversal sensed by controller.  FIG. 5  is a flow diagram representing a plurality of door reversal algorithms. A primary distinguishing characteristic for selecting which algorithm to use is whether the triggering, sensed condition is of a contact type or a non-contact type. Although  FIG. 5  shows two distinct lines of flow it is possible that other implementations may include other lines of flow with different time delays based on different sensed conditions. 
     The motor reversal flow begins at a block  301  when controller  208  senses that a reversal is needed. Next, a block  303  is performed in which power is removed such as by opening relay  166  ( FIG. 3 ). A decision block  305 , is then performed to determine whether the sensed reversal condition is of a contact type or a non-contact type. When a contact type reversal is sensed, some urgency is implemented in reversing the barrier. Alternatively, when a non-contact type reversal is sensed less urgency in reversal is required and flow proceeds to a block  317  where a 1.5 second delay period is provided before moving to blocks  319  and  321  to set up a loop transition counter by setting a variable N to 1. Next, a decision  323  is performed to determine whether the unpowered motor as slowed to a predetermined amount or less. The predetermined speed for block  323  may be, for example, 50% of operation speed. When sufficient slowing is detected, flow proceeds to a block  329  where a start sequence for the reverse direction is begun. In terms of the example of  FIG. 3  the start sequence begins with the setting of relay  168  to the appropriate direction and the closing of power relay  166  and start relay  184 . After beginning the start sequence, a delay of 200 msec is implemented by block  331  and a check  333  is performed to see whether the motor has achieved a predetermined rate in the newly desired direction. The predetermined speed for block  333  may be, for example, 33% of operating speed. If such has been achieved, the start sequence is terminated at block  339  by opening start relay  184 . 
     When block  333  indicates that sufficient speed in the new direction (e.g.,  339  of operator speed) has not been achieved a conditional two second delay period is implemented by block  335 . During the two second delay period the motor speed is periodically checked to see if sufficient speed, 33% of operating speed, in the new direction. At the end of the two second delay period or when sufficient speed has been achieved the start relay  184  is opened. 
     When step  323  determines that the motor has not slowed sufficiently (e.g., 50% of operating speed), a loop consisting of blocks  321 , 323 , 325  and  327  is traversed to provide a maximum further delay of 1.5 seconds during which motor speed is checked at 0.5 second intervals. If the motor has not slowed sufficiently during the 1.5 second interval block  325  sends the flow to block  337  in which the start sequence is begun. Steps  333 , 335  and  339  are then performed as described above. 
     When block  305  determines that a contact type reversal need has been sensed reversal is performed with somewhat greater urgency. In this algorithm sequence a block  307  is performed to energize a start sequence for the reversed direction. Next, a 200 msec delay is inserted by operation of block  309 . Thereafter, a conditional two second delay period is performed by blocks  311  and  313 . During this two second delay the motor speed is frequently checked. The start sequence will be ended by a block  315  whenever the motor has achieved a predetermined speed e.g., 33% of operating speed, in the new direction or the full two seconds have elapsed. 
     The preceding examples show the operation of the present system for motor reversal. It should be recognized that although the examples are in terms of relay control of the motor, other types of control such as by triac could be employed. Further, other types of induction motors may be employed without departing from the scope of the invention.

Summary:
Methods and apparatus for reversing a drive motor for a barrier movement operator are disclosed. The operator senses the nature of a request for reversal and based on the nature of the sensed request performs one of a plurality of processes to reverse the motor.