Abstract:
A method and apparatus for controlling a barrier movement operator comprising a controller that dynamically controls barrier operator braking to electronically slow, stop or reverse the motor in the barrier operator controller. The apparatus includes a source of electrical power for providing the necessary power to operate the apparatus, a converter for supplying power to a DC motor, and a controller for enabling dynamic braking of the movable barrier operator using electronic braking of the electric motor. The dynamic braking of the motor gradually slows movement of the barrier operator, thereby reducing forces acting on the motor and on the barrier.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates generally to dynamic braking of D.C. motors and, more particularly, to a motor control system for dynamically braking a motor in a barrier movement operator. 
   Most generally available barrier operators when stopped in mid-travel come to a halt very abruptly. This is most easily observable, for example, when a garage door opener is moving a door from an opened to closed position and is reversed or stopped, such as when infrared sensors detect an obstruction or when a control button for stopping or reversing the barrier operator is depressed. The garage door, which can weigh upwards of 250 pounds, can be seen to shudder to a stop. During a reversal operation, the barrier jitters and bounces, causing the chain track and the entire housing of the barrier operator to shake in its moorings. The sheer weigh and velocity of the door, combined with having to reverse or stop suddenly, puts a strain on the entire system. 
   The above phenomenon is caused by the manner in which the barrier movement operator is controlled. Common DC control arrangements consist of a relay or other switching apparatus to control the applied DC potential, and some form of power regulator to connect portions of power from a DC supply to the motor. The variable power connection may consist of something as simple as a rheostat or something more complex such as a semiconductor switching arrangement. Although the power couplers may vary in sophistication, the system is basically a source of DC power coupled by a regulator to the motor or other power using device. 
   Referring to  FIG. 1 , a typical barrier movement operator is illustrated. As shown, the operator includes an AC line source  10  for providing power to the system. The AC voltage from the AC line source  10  is filtered by a filter  12  then converted into DC voltage by a rectifier  14  for use by a load, such as a DC motor  16 . The barrier operator is slowed to a stop at the limit by a controller  18  that pulses transistor Q 1   20 . Transistor Q 1   20 , as used herein is a N-channel field effect transistor (FET). However, other types of transistors may also be used with appropriate circuit modifications performed by those skilled in the art. Relay 1   22  and Relay 2   24  control the direction of the motor. Pulsing transistor Q 1   20  causes the voltage being applied to the motor to be turned off and on and has the effect of reducing the supply voltage. Once supply voltage is reduced or eliminated, the friction in the system stops the door travel. A particular disadvantage of such a system is that the barrier operator is stopped at a desired position only when the rate of frictional stopping is greater than the desired electrical stopping. 
   Turning now to  FIG. 2 , the operator is shown wherein the rate of frictional stopping is greater than the desired electrical stopping. The line voltage  30  supplied by the AC line source  10  ( FIG. 1 ) is passed through the full wave rectifier  14  to produce a fully rectified signal  32  for use by the motor  16 . When the operator  110  is commanded to stop, the controller  18  pulses the power  34  being supplied to the motor  16 , thereby reducing the voltage to the motor and causing the motor to stop. The frictional rate of stopping is adequate because the voltage  36  across the motor  16 , when the motor is acting as a generator, is lower than the peak voltage  38  of the power supplied from the rectifier  14 . Thus, the door comes to a stop in the desired position. 
   In contrast, referring to  FIG. 3 , it can be seen that problems arise in those instances where the inertia of the barrier operator is so high that the rate of frictional stopping is slower than intended. As above, the rectified voltage  32  is supplied to the motor  16 . When the operator  110  receives a stop command, the controller  18  provides a pulsed voltage  34  to the motor  16 , thereby having the effect of reducing the supply voltage. However, in this instance, the frictional rate is inadequate because the voltage  40  generated by the motor  16 , which is now acting as a generator, is greater than the peak voltage  42  of the power supplied by the rectifier  14 . Thus, the barrier is unable to be stopped at the desired rate and the operator  110  cannot be stopped simply by pulsing the transistors. As such, in those instances where the barrier operator is unable to slow the movement of the barrier, stopping the operator in a panic situation must be accomplished by shorting the motor, or allowing the barrier to strike a physical limit, resulting in a very sudden stop. Unfortunately, such abrupt stops create high forces acting on the door and the operator, as described above, which result in undue wear and tear on the operator and high stresses on the barrier. 
   What is needed, therefore, is an operator controller for softening the deceleration of the operator and the door. 
   SUMMARY OF THE INVENTION 
   A method and apparatus for controlling an operator is described herein and provides a controller that dynamically controls barrier operator braking using one of several different methods to electronically slow, stop or reverse the motor. In one form, the apparatus includes a source of electrical power for providing the necessary power to operate the apparatus, a converter for supplying power to a DC motor, and a controller for enabling dynamic braking of the movable barrier operator using electronic braking of the electric motor to gradually slow movement of the barrier operator, thereby reducing forces acting on the motor. 
   According to a particular embodiment, an AC input signal is full wave rectified and supplied to gating circuitry coupled to the converter. The rectified signal is also used to provide power to a motor used in the movable barrier operator. The voltage applied to the motor is regulated through the use of software. The software controls the controller such that the controller, upon receiving a command to stop or reverse, reverses the direction of the power supply and pulses the power from the power supply to the motor at a predetermined rate. This results in a controlled stop or reversal of the barrier. 
   In another aspect, soft stopping and reversing of the barrier movement operator is achieved by adding electrical resistance to the motor. The electrical resistance may be present during all operation stages of the operator or may be configured such that the electrical resistance is active only when the barrier movement operator is given a stop or reverse command. 
   In still another aspect, a power amplifier is used to control the motor speed to enable soft stopping or reversal of the barrier movement operator. The power amplifier normally provides power to the motor as required during its normal operation of moving up or down. However, when the operator receives a stop or reverse command, the power amplifier absorbs the energy from the motor, reproduces it at a higher potential power and uses the stored power then to slow or stop the barrier operator in a controlled manner. 
   The invention as described, in any of its various aspects, reduces the abrupt stops and high forces acting on the door and the operator, thereby also reducing the wear and tear on the operator and barrier. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which: 
       FIG. 1  is a schematic view of a prior art movable barrier operator controller; 
       FIG. 2  is a graph illustrating the voltages in the barrier operator of  FIG. 1  in a first operating mode; 
       FIG. 3  is a graph illustrating the voltages in the barrier operator of  FIG. 1  in a second operating mode; 
     FIG.  4 . Is a perspective view of a movable barrier operator using the motor controller described herein; 
       FIG. 5  is a block diagram of a novel method for controlling the barrier operator of  FIG. 1 ; 
       FIG. 6  is a schematic diagram of a resistor based barrier operator controller in a particular aspect of the invention; 
       FIG. 7  is a schematic diagram of the resistor based barrier operator controller of  FIG. 5  in another aspect; 
       FIG. 8  is a schematic diagram of a power amplifier based barrier operator controller in another embodiment of the invention; and 
       FIG. 9  is a schematic diagram of a transistor based barrier operator controller in another embodiment of the invention. 
   

   While the invention will be described in connection with a preferred embodiment, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. 
   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to the drawings and especially to  FIG. 4 , a movable barrier operator embodying the present invention is generally shown therein and identified by reference numeral  110 . The movable barrier operator  110  includes a head unit  112  mounted within a garage  114  and is employed for controlling the opening and closing of the garage  114 . More specifically, the head unit  112  is mounted to the ceiling  116  of the garage  114  and includes a motor  16  ( FIG. 5 ) and a controller  18  ( FIG. 5 ) for controlling how power is supplied to the motor  16 . Extending from the head unit  112  is a rail  118  having a releasable trolley  120  attached thereto and an arm  122  extending from the trolley  120  to a multiple paneled garage door  124  positioned for movement along a pair of door rails  126  and  128 . The movable barrier operator  110  transfers the garage door  124  between the closed position illustrated in FIG.  4  and an open or raised position, allowing access to and from the garage  114 . The moveable barrier operator  110  may be a garage door operator as shown in  FIG. 4 , a gate operator, a tubular motor operator, etc. 
   The system of  FIG. 4  includes a hand-held transmitter unit  130  adapted to send signals to an antenna  132  positioned on or extending from the head unit  112  and coupled to a receiver (not shown) located within the head unit  112 . An external control pad  134  is positioned on the outside of the garage  114  having a plurality of buttons  135  thereon and communicates via radio frequency transmission with the antenna  132  and receiver of the head unit  112 . A switch module  139  is mounted on a wall of the garage  114 . The switch module  139  is connected to the head unit  112  by a pair of wires  139   a . The switch module  139  includes a learn switch  139   b , a light switch  139   c , a lock switch  139   d  and a command switch  139   e . Alternatively, the switch wired to the head unit  112  could be a simple on/off switch used to activate or stop the operation of the movable barrier. In addition, a barrier movement sensor, such as a motor RPM detector as described in U.S. Pat. No. 6,025,785 and incorporated by reference herein, may be monitored by the controller  18  to identify the speed and position of the motor and connected barrier. 
   An optical emitter  142  and an optical detector  146  are coupled to the head unit  112  by a pair of wires  144  and  148 , respectively. The emitter  142  and detector  146  are used to satisfy the requirements of Underwriter&#39;s Laboratories, the Consumer Product Safety Commission and the like that require that garage door operators sold in the United States must, when in a closing mode and contacting an obstruction having a height of more than one inch, reverse and open the door in order to prevent damage to property and injury to persons. The controller  18  ( FIG. 5 ) for the movable barrier operator  110  responds to the various inputs by starting and stopping the motor  16  (FIG.  5 ), which is used to move the door. 
   Referring to  FIGS. 1 and 5 , in a particular aspect of the present invention, a low cost method for electronically slowing the motor  16  is described. Instead of pulsing the power to the motor  16  and relying on friction to bring the operator  110  to a stop, a software program, during the slowdown and the slowdown and reverse functions, reverses the power supply direction and ramps up or increases the width of applied pulses of voltage. 
   Referring first to  FIG. 1 , the operator  110  includes an AC line power source  10 , a filter  12  for filtering the AC line power and a rectifier  14  for providing a DC voltage to the motor  16 . Relay 1   22  and Relay 2   24  operate under the control of controller  18  and are provided to change the rotational direction of the motor  16  by effectively reversing the power supply direction. For example, closing Relay 2   24  and opening Relay 1   22  causes the motor  16  to operate in a first direction. Closing Relay 1   22  and opening Relay 2   24  causes the motor to turn in the opposite direction, since the current flow through the motor armature  26 ,  28  is reversed. It is to be noted that when the power supply direction is reversed, the motor  16  does not suddenly and immediately reverse directions. Rather, the rotation of the motor  16  in the first direction gradually slows, stops and then reverses direction at an increasing speed. In contrast, shorting the motor armature  26 ,  28  results in an undesirable instantaneous and jarring stop. 
   As described above, the operator  110  shown in  FIG. 1  in normal operation is slowed to a stop at the limit by the controller  18 , which pulses transistor Q 1   20 . The pulsing of transistor Q 1   20  causes the power being applied to the motor  16  to be turned off and on. This has the effect of reducing the supply voltage to the operator  110 , thereby causing the motor  16  to slow to a stop. As mentioned above, however, this type of stopping is not effective in all situation, such as when the rate of frictional stopping is inadequate to stop the door at a desired position. 
   As particularly shown in  FIG. 5 , software control is used to softly slow or stop the operator. Step  180  is the entry point for the controller software. In step  182 , the operator  110  determines whether a stop command has been received. The stop command may be received from a variety of sources, such as from the hand held transmitter  130 , the control pad  134  or the switch module  139 . When a stop command is received, the controller  18  reverses the power supply direction in step  184  by changing the sate of Relay 1   22  and Relay 2   24  and ramps up the pulse width in step  186  via transistor  20 . In step  188 , the operator  110  determines whether the garage door  124  has stopped by reading the motor RPM sensor. If the garage door  124  has not stopped, then the program returns to step  186  and continues to ramp up the pulse width as the garage door  124  continues to move. However, if the garage door  124  is stopped in step  188 , the controller  18  removes power to the motor  16  in step  190 . The program then ends in step  192 . 
   If in step  182  a stop command was not received, then in step  194  the operator  110  determines whether a reverse command was received. The reverse command may be sent from any of the sources that are able to send a stop command (as described above), or if the garage door  124  encounters an obstacle when closing. If a reverse command is received, then in step  196  the barrier operator  110  reverses the power supply direction using Relay 1   22  and Relay 2   24 . The controller  18  ramps up the pulse width in step  198 . In step  200  the operator  110  determines whether the garage door has reached a maximum desired travel limit. If the limit has not been reached, the controller  18  continues to ramp up the pulse width as the garage door  124  continues moving. If, however, in step  200  the door limit has been reached, then the program jumps to step  184  and executes the remainder of the program, as described above. A particular advantage of the described control system is the low cost of implementation, since hardware modifications do not need to be made to the barrier movement operator. 
   Turning now to  FIG. 6 , in another aspect, the barrier movement operator  110  of the present invention is implemented using a dynamic braking resistor to electrically increase the resistance to movement on the motor  16  to enable the barrier movement operator  110  to slow to a stop. The operator  110  includes an AC line power source  10 , a filter  12  for filtering the AC line power, a rectifier  14  for converting the filtered then power into a DC voltage for use by the motor  16  and Relay 1   22  and Relay 2   24  for controlling motor direction. Dynamic braking resistor R 1   150  is added across the armatures  26 ,  28  of the motor  16 . When the operator  110  receives a command to stop, the controller  18  turns off transistor Q 1   20 . By doing so, supply voltage from the rectifier  14  does not reach the motor  16 . At that point, voltage generated by the motor  16  during its rotation acts through resistor R 1   150 , which behaves like an increase in the friction of the system, thereby causing the motor  16  to come to a controlled stop. The value of resistor R 1   150  is chosen to have a rate of frictional stopping faster than the rate of electrical stopping to enable the door to stop at the desired position. A particular advantage of such a system is its low cost and ease of implementation. 
   Referring now to  FIG. 7 , the embodiment of  FIG. 6  is extended using a more efficient design. As shown in  FIG. 6 , resistor R 1   150  is present in the circuit at all times and generates heat even when the operator  110  is operating in its normal mode of operation. As a result, the drive circuit for motor  16  must supply power in its normal mode of operation to drive the motor and generate heat through resistor R 1   150 . As shown in  FIG. 7 , however, transistor Q 2   154 , which may be a P-channel FET among others, is used to eliminate the increased power consumption and heat generation by applying resistor R 1   150  only when the barrier movement operator  110  is commanded to stop or reverse. 
   The barrier operator  110  includes the AC line power  10 , filter  12 , rectifier  14 , motor  16  having armatures  26 ,  28  and Relay 1   22  and Relay 2   24  as described above. In this case, however, when the barrier movement operator  110  is in its normal mode of operation, and the motor  16  is operating to move the barrier up or down, transistor Q 2   154  is on and transistor Q 1   152  is off. This renders resistor R 1   150  effectively inactive. Therefore, there is no heat generated through resistor R 1   150  when the motor  16  is operating in a normal powered mode. 
   When the operator  110  receives a stop command, the controller  18  turns on transistor Q 1   152 . This prevents the motor  16  from receiving voltage from the rectifier  14 . At the same time, when the controller  18  turns on Q 1   152 , it also turns off transistor Q 2   154 . As a result, transistor Q 2   154  applies resistor R 1   150  across the armature  26 ,  28  of the motor  16 . This causes the motor  16  to slow to a soft, controlled stop due to the increased electrical friction as described above. Thus, a particular advantage of the present aspect of the invention is the ability of the system to generate electrical friction to help the barrier movement operator slow to a stop, while at the same time decreasing the heat generated by resistor R 1   150  in all operating modes of the operator  110  and decreasing the power consumption of the system when the motor  16  is being powered. 
   Referring to  FIG. 8 , another aspect of the dynamic braking system of the barrier operator  110  is shown wherein the greatest amount of control over the operation of the barrier movement operator  110  may be exerted. This aspect of the invention, much like the embodiment described above, includes a barrier operator  110  having AC line power  10 , filter  12 , rectifier  14 , Relay 1   22  and Relay 2   24  and motor  16 . In addition, a power amplifier  156  is provided to control the voltage being supplied to the motor  16 . The power amplifier  156  receives voltage from the rectifier  14  and supplies voltage to the motor  16  during the barrier movement operator&#39;s normal mode of operation. During a stop or reversal operation, the controller  18  reverses Relay 1   22  and Relay 2   24  and drives up the voltage from the power amplifier  156 . Current flow from the motor, which is now acting as a generator, opposes the positive supply voltage from the rectifier  14 , thereby reducing the supply current. Thus, better control of motor speed is achieved and the motor  16  is brought to a controlled stop 
   Referring now to  FIG. 9 , in another aspect of the present invention, motor direction and braking is fully controlled by electronic means through the use of multiple control systems and transistors acting on the motor armatures  26 ,  28 . As described above, the barrier operator  110  includes the AC line power supply  10 , filter  12 , rectifier  14  and motor  16 , which has armatures  26 ,  28 . In the present embodiment, the armature  26  is connected to the voltage source through transistor Q 4   164 , when the barrier is to be moved. Transistor Q 4   164  is individually controlled by a controller  172 . The motor armature  26  may also be connected to ground through transistor Q 1   158 . Transistor Q 1   158  is also individually controlled by a controller  166 . Similarly, motor armature  28  is connected to the voltage supply through transistor Q 2   160 . The controller  168  controls the state of transistor Q 2   160 . The motor armature  28  may also be connected to ground through transistor Q 3   162 . Once again, a controller  170  is used to individually control transistor Q 3   162 . It is to be noted that although multiple controllers have been described for purposes of the foregoing example, similar control function may be achieved using a single controller, such as controller  18 , and multiple control lines. 
   In operation, the controller  166  and the controller  168  turn on transistors Q 1   158  and Q 2   160 , thereby causing the motor  16  to turn in a first direction. If the motor  16  needs to be braked, transistors Q 1   158  and Q 3   162  or, alternatively, transistors Q 4   164  and Q 2   160 , can be turned on by their respective controllers. In addition, the controller  170  and the controller  172  may turn on transistors Q 3   162  and Q 4   164  to cause the motor  16  to turn in a second direction. A second braking system using pulsed shorting of the motor also may be implemented by turning on one of the four transistors and using a diode in the opposite leg to clamp the generator action/speed of the motor. 
   Thus, it is apparent that there has been provided, in accordance with the invention, a power controller that fully satisfies the objects, aims, and advantages set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.