Abstract:
The present invention discloses an automatic door systems related to a fail safe method of controlling an automatic door operating system. One aspect of the present invention provides a method for controlling an electric motor of an automatic door system, the motor being operatively connected to a door panel to enable the motor to perform a door moving operation wherein the motor moves the door panel between the open and closed positions thereof using an electric power signal delivered to the motor from an electric power supply. Another aspect of the present invention provides a machine readable medium encoded with a plurality of machine executable instruction sequences for performing a method for controlling an electric motor of an automatic door system. Another aspect of the invention provides a control system for an automatic door system, the automatic door system including a door panel mounted for movement during a door moving operation between open and closed positions.

Description:
[0001]    The present application claims priority to U.S. Provisional Application of Anthony Ranaudo, Application No. 60/266,454, filed Feb. 6, 2001, the entirety of which is hereby incorporated into the present application by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention is generally related to automatic door systems and more particularly related to a fail safe method of controlling an automatic door operating system.  
         BACKGROUND AND SUMMARY OF THE INVENTION  
         [0003]    Automatic door operating systems are frequently used in commercial, industrial, and residential settings for power operated opening and closing of interior or exterior door panels. A door operating system may include an electric motor that is operatively connected to a door panel of a door assembly by a linkage assembly. Door panel movement in opening and closing directions may be affected by energizing the electric motor to drive the same in a selected direction and at a selected speed. A control system may be included in the automatic door operating system to control the electric motor and thereby control door panel movement.  
           [0004]    The control system monitors door panel movement and stops the door panel movement when the control system detects a predetermined condition. A predetermined condition may occur when a door panel reaches an end of its travel cycle (that is, when it is fully open or fully closed) or when the door panel encounters an obstruction. The control system stops door panel movement by de-energizing the electric motor. Because door panels are often operated automatically to allow persons to pass through the associated doorway, it is important that the door panel stop when the control system attempts to de-energize the electric motor.  
           [0005]    To ensure that the door panel stops during an attempt to de-energize the motor, one aspect of the present invention provides a method for controlling an electric motor of an automatic door system, the motor being operatively connected to a door panel to enable the motor to perform a door moving operation wherein the motor moves the door panel between the open and closed positions thereof using an electric power signal delivered to the motor from an electric power supply. The motor is communicated to a motor controller that controls the electric power signal delivered to the motor to control the door moving operation. The door system includes a switch connected between the motor and the motor controller, the switch being movable between (a) an open position disabling the delivery of the electric power signal from the motor controller to the motor and (b) a closed position enabling the delivery of the electric power signal from the motor controller to the motor. The method comprises (1) while the motor controller is delivering the electric power signal to the motor to affect the door moving operation, monitoring the door moving operation for an occurrence of a predetermined condition and (2) responsive to detecting the occurrence of the predetermined condition, (a) instructing the motor controller to terminate the delivery of the electric power signal from the electric power supply to the door operator and (b) affecting movement of the switch from the closed position thereof to the open position thereof to ensure termination of the delivery of the electric power signal in the event the electric power signal is not terminated by the controller. These acts (a) and (b) may be performed simultaneously or in any order.  
           [0006]    The method may be carried out using a computer processor. The processor may be programmed with computer code that includes instructions for controlling and monitoring door panel movement. Accordingly, another aspect of the present invention provides a machine readable medium encoded with a plurality of machine executable instruction sequences for performing a method for controlling an electric motor of an automatic door system. The motor is operatively connected to a door panel to enable the motor to perform a door moving operation wherein the motor moves the door panel between the open and closed positions thereof using an electric power signal delivered to the motor from an electric power supply. The motor is communicated to a motor controller that controls the electric power signal delivered to the motor to control the door moving operation. The door system includes a switch connected between the motor and the motor controller, the switch being movable between (a) an open position disabling the delivery of the electric power signal from the motor controller to the motor and (b) a closed position enabling the delivery of the electric power signal from the motor controller to the motor. The automatic door system further includes a processor communicated to the motor controller. The processor is adapted to execute the instruction sequences. The instruction sequences comprise (1) while the motor controller is delivering the electric power signal to the motor to affect the door moving operation, monitoring the door moving operation for an occurrence of a predetermined condition and (2) responsive to detecting the occurrence of the predetermined condition, (a) instructing the motor controller to terminate the delivery of the electric power signal from the electric power supply to the door operator and (b) affecting movement of the switch from the closed position thereof to the open position thereof to ensure termination of the delivery of electric power signal in the event the electric power signal is not terminated by the controller. The executable instructions may be provided so that the acts (a) and (b) are performed simultaneously or in any order.  
           [0007]    Other aspects of the invention provide an automatic door system comprising a door panel mounted for movement between open and closed positions and an electric motor. The motor is operatively interconnected to the door panel to enable the motor to perform a door moving operation wherein the motor moves the door panel between the open and closed positions thereof using an electric power signal delivered to the motor from an electric power supply. A control system comprises (1) a motor controller is communicated to the motor, the motor controller being operable to control the delivery of the electric power signal to the motor to control the door moving operation and (2) a switch is connected between the motor and the controller, the switch being movable between (a) an open position disabling the delivery of the electric power signal from the motor controller to the motor and (b) a closed position enabling the delivery of the electric power signal from the motor controller to the motor. The control system is operable to (1) monitor the door moving operation to detect the occurrence of a predetermined condition while the motor controller is delivering the electric power signal to the motor to affect the door moving operation and (2) in response to detecting the occurrence of the predetermined condition, (a) instruct the motor controller to terminate the delivery of the electric power signal from the power supply to the motor and (b) affect movement of the switch from the closed position thereof to the open position thereof to ensure termination of the delivery of the electric power signal to the motor in the event the electric power signal is not terminated by the controller.  
           [0008]    Another aspect of the invention provides a control system for an automatic door system, the automatic door system including a door panel mounted for movement during a door moving operation between open and closed positions. The control system comprises an electric motor operatively connected to the door panel to enable the motor to perform the door moving operation wherein the motor drives the door panel between the open and closed positions thereof using an electric power signal delivered to the motor from an electric power supply. The control system further comprises a motor controller electrically communicated to the motor and to the power supply, the motor controller being operable to control the electric power signal delivered to the motor and thereby control operation of the motor. The control system further includes a switch connected between the motor and the motor controller. The switch is movable between (a) an open position disabling the delivery of the electric power signal from the motor controller to the motor and (b) a closed position enabling the delivery of the electric power signal from the motor controller to the motor. The control system is operable to (1) monitor the door moving operation to detect the occurrence of a predetermined condition while the motor controller is delivering the electric power signal to the motor to affect the door moving operation and, (2) in response to detecting the occurrence of the predetermined condition, (a) instruct the motor controller to terminate the delivery of the electric power signal from the power supply to the motor and (b) affect movement of the switch from the closed position thereof to the open position thereof to ensure termination of the delivery of the electric power signal to the motor in the event the electric power signal is not terminated by the controller.  
           [0009]    Other objects, features, and advantages of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 shows a door assembly mounted on a building wall shown in fragmentary view and an automatic door operating system operatively mounted between a door panel and a door frame of the door assembly;  
         [0011]    [0011]FIG. 2 shows an enlarged fragmentary view of the door assembly with the door panel thereof in a partially open position and showing the power assembly with a cover structure thereof removed and not shown to show the structure thereof;  
         [0012]    [0012]FIG. 3 shows a schematic representation of a control circuit and the power supply for the automatic door operating system;  
         [0013]    [0013]FIG. 4 shows a schematic representation of a shaft encoder of an electric motor;  
         [0014]    [0014]FIGS. 5 and 6 show a flowchart for a control system for the automatic door operating system; and  
         [0015]    [0015]FIGS. 7 through 10 show a circuit diagram for implementing control circuitry for the automatic door operating system. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    [0016]FIG. 1 shows a door assembly  10  and a control system  12  operatively engaged with the door assembly  10 . The door assembly  10  includes a door frame  14  and a door panel  16 . The door frame  14  is mounted around the periphery of a door opening  18  formed in a building wall  20 . The exemplary door panel  16  is mounted to the door frame  14  by hinges  22  for swinging movement with respect to the door frame  14  between open and closed positions. Together, the control system  12  and the door assembly  10  may be considered an automatic door system.  
         [0017]    The illustrated door assembly  10  is of the type typically found on either an interior or exterior wall of a commercial, industrial, or residential building and the illustrated door control system  12  is attached to the door assembly  10  as a retro-fit door control system. Alternatively, the principles of the present invention could be applied to a system in which the control system  12  is incorporated into the door assembly  10 , such as is commonly found in the automatic door systems used in commercial storefronts and other commercial locations. The overall construction of the automatic door system, and whether it is of a retrofit or fully packaged type are not particularly important to the present invention. Instead, the present invention is primarily concerned with the method of controlling the system&#39;s motor, the machine executable instructions for controlling the system&#39;s motor, and the overall system itself. It can also be appreciated that although the exemplary door assembly shown in FIGS. 1 and 2 is of the swinging type, this illustration is not intended to limit the scope of the invention. It is contemplated to configure the control system  12  for installation on and for use in controlling slidably mounted door panels (such as, for example, door panels slidably mounted for rectilinear movement between open and closed positions with respect to the associated door frame), revolving door panels (that is, door panels mounted for movement in a revolving type door), bi-fold door systems, or any other type of door system.  
         [0018]    The control system  12  includes a door power assembly  24  and a control module  25  (see FIG. 2). The door power assembly  24  is mounted on the door panel  16  and operatively connected with the door frame  14  by a linkage assembly  26 . The structure of the door power assembly  24  can be understood from FIG. 2 which shows an enlarged view of the power assembly  24  (with a cover structure  28  of the control system  12  removed and not shown in FIG. 2) mounted on the door panel  16  (shown in a partially open position). The power assembly  24  includes an axial operator  30  mounted on the door panel  16  by a door panel mounting structure  32 . The axial operator  30  includes an electric motor  34  that is operatively coupled to the linkage assembly  26  by a planet gear reduction transmission  38 . The output shaft of the axial operator  30  may be connected directly to the linkage assembly  26  or, as shown in FIG. 2, the axial operator  30  may be connected to the linkage assembly  26  through a clutch assembly  35 . The clutch assembly  35  is optional and is not required by the invention. The linkage assembly  26  includes a wall mounting structure  40  mounted on the door frame  14  and a linkage structure  42  operatively engaged between the wall mounting structure  40  and an output shaft of the axial operator  30 .  
         [0019]    The motor  34  acts through the transmission  38  and the linking assembly  26  to move the door panel  16  between its open and closed positions. The details of the structure of the door assembly  10  and the structure and operation of the power assembly  24  and the manner in which the power assembly  24  is operatively connected through the linkage assembly  26  with the door assembly  10  will not be considered in detail. These details are disclosed in commonly assigned Patent Application Serial No. 60/230,433 entitled RETROFIT POWER DOOR ASSEMBLY which application is hereby incorporated by reference in its entirety into the present application for all material disclosed therein.  
         [0020]    The operation and control of the electric motor  34  is generally affected by control circuitry  50  (generally contained within the control module  25  shown mounted on the door panel  16  in FIG. 2 and shown schematically in FIG. 3) and an electric power supply  52  (also shown schematically in FIG. 3). The control circuitry  50  includes a central processing unit  54 , a motor controller  56  and a switch assembly  58 . The motor  34  (shown schematically in FIG. 3) is electrically communicated to the motor controller  56 . The motor controller  56  generally operates to control the transmission of an electric power signal from the power supply  52  to the motor  34 . The switch assembly  58  is connected between the motor controller  56  and the motor  34 .  
         [0021]    The CPU  54  may be a programmable general purpose microprocessor or any other type of processor capable of controlling the motor controller  56 , irrespective of whether it is programmed by software, whether it is hardwired, or whether it is chip driven to perform its processing function. The motor controller  56  may be a pulse width modulator and the switch assembly  58  may be a relay. The pulse width modulator may be realized by an H-Bridge configuration of switches and a motor drive control module or “chip” which operates the H-Bridge. The power supply signal from the power source  52  is communicated to the motor  34  through the H-Bridge configuration of the motor controller  56 . The motor control module of the motor controller  56  operates the H-Bridge configuration to produce a pulse width modulated power signal that is communicated to the motor  34 . The motor drive control module is, in turn, communicated to and controlled by the CPU  54  such that the CPU  54  acting through the motor control module of the motor controller  56  controls the flow of power to the motor  34 . The motor controller  56  need not be a pulse width modulator and, instead, may be any other suitable device for controlling the motor  34 .  
         [0022]    In the illustrated embodiment, the relay includes a switch element and an inductive coil, but any type of switch suitable for achieving the present invention may be used. The switch element is electrically communicated in series between the motor  34  and the H-Bridge configuration of the motor controller  56 . The switch element is movable between (a) an open position disabling the delivery of the electric power signal from the motor controller  56  to the motor  34  and (b) a closed position enabling the delivery of the electric power signal from the motor controller  56  to the motor  34 . The inductive coil is communicated to and controlled by the CPU  54 . The CPU  54 , by controlling a flow of current through the inductive coil, controls the movement of the switching element between open and closed positions and thereby controls the transmission of the electrical power signal from the power supply  52  to the motor  34 . Specifically, the switch element is made of a magnetizeable material and applying an electric signal (as controlled by the CPU) creates a magnetic field that attracts the switch element to its closed position thereof. The switching element is normally biased to its open position, and thus automatically returns to its open position upon removal of the electric signal applied to the inductive coil. The CPU  54  is therefore operable to control the movement of the switching element between closed and open positions to enable and disable, respectively, the delivery of the electric power signal to the motor as aforesaid.  
         [0023]    The CPU  54  is programmed with a series of executable instructions to control the operation of the pulse width modulator and thereby control the speed and/or direction of the motor  34  (and therefore the speed and direction of door panel  16  movement). As explained in greater detail below, while the motor controller  56  is delivering the electric power signal to the motor  34  to affect a door moving operation, the CPU  54  monitors the door movement for the occurrence of one or more predetermined conditions (such as improper motor speed or motor current). For example, the CPU  54  may monitor the motor speed and/or motor current through motor speed encoder circuitry and motor current feedback circuitry  60  and  62  (see FIG. 3), respectively, during a door moving operation and, if a predetermined condition is detected (such as if the speed of the door panel is higher or lower than expected and/or the motor current is higher than expected during a door moving operation), the CPU  54  responds by (a) instructing (or commanding) the motor controller  56  to terminate delivery of the electric power signal from the power supply  52  to the motor  34  and (b) moving the switch element in the switch assembly  58  from its closed position to its open position to ensure termination of the delivery of the electric power signal to the motor  34  in the event the electric power signal from the motor controller  56  is not terminated by the command sent from the CPU  54  to the motor controller  56 .  
         [0024]    Because the CPU  54  responds to the detection of one or more predetermined conditions during a door moving operation by commanding the motor controller  56  to stop delivering power to the motor  34  and to open the switch  58  between the motor controller  56  and the motor  34 , the motor controller  56  and the switch  58  provide a redundant system for shutting off the supply of power to the motor  34  in the event a fault is detected and thereby provides fail safe operation of the control system  12 .  
       Operation of the Automatic Door System  
       [0025]    Generally, the door control system  12  operates by detecting an input signal generated by the actions of a person (hereafter, the “operator”) operating the door system and, in response to the detected input signal, energizing the motor  34  to initiate a door opening (or door closing) operation, moving the door panel to its open (or closed) position and then de-energizing the motor  34 . The CPU  54  may be programmed to respond to a variety of operator-initiated input signals by generating appropriate output signals to control operation of door panel movement, to monitor door system operation during door panel movement and to take corrective actions if a predetermined fault condition is detected during door panel movement.  
         [0026]    Operator-initiated input signals may be provided from a variety of devices including a variety of devices that are hardwired to the CPU  54  (that is, communicated to the CPU directly from an input device such as a switch through electrical conducting members such as conventional electrical wires), such as infrared, Doppler, or microwave motion and/or presence detectors, and a variety of wireless devices, such as wireless devices that transmit signals through the use of infrared light and devices that transmit signals using higher (or lower) frequency electromagnetic radiation such as radio frequency electromagnetic radiation.  
         [0027]    The CPU  54  may monitor door movement indirectly by monitoring the rotation of the motor shaft of the electric motor  34  using, for example, a shaft encoder that may be provided as part of the motor  34 . The shaft encoder may form part of the feedback circuit  60  of FIG. 3. An example of a shaft encoder  68  is shown schematically in FIG. 4. FIG. 4 shows a portion of a motor shaft  70  and a magnetic material  72  mounted within a portion of the shaft  70 . A pair of magnetic field detectors  74 ,  76  (which may be, for example, a pair of Hall effect sensors) are mounted adjacent the shaft  70  and electrically communicated to the CPU  54  through conductors  78 ,  80 . During the rotation of the shaft  70 , movement of the magnetic material  72  past a detector  74  or  76  causes that detector  74  or  76  to generate an electrical pulse. Each pulse is communicated to the CPU  54  through conductors  78 ,  80 .  
         [0028]    The conductors  78 ,  80  may comprise the A and B channels, respectively, of a shaft encoder that send a series of pulses to the CPU  54  during rotational movement of the shaft  70  with respect to the detectors  74 ,  76 . The pulses provide the CPU  54  with information about shaft  70  movement. The CPU  54  may use the pulses received on the A and B channels to determine (1) the speed at which the door panel  16  is moving, (2) the direction in which the door panel  16  is moving and (3) the angular distance the door panel has moved from either its open or its closed position. Specifically, the CPU  54  may be programmed to calculate the angular speed of the motor shaft  70  by, for example, measuring the time period between successive pulses on a particular channel and to use this data to calculate the angular speed of the door panel  16 . The CPU  54  may be programmed to determine the direction of door panel movement by calculating the time intervals between the pulses received from the A and B channels. The CPU  54  may be programmed to determine the angular distance the door panel  16  has moved from either its open or closed position based on the total number of revolutions of the shaft  70  in either its opening or closing direction (which can be calculated by counting the total number of pulses received on either the A or the B channel) and to use this data to control door panel operation as a function of door panel position. Circuitry  62  may also be provided between the motor  34  in the CPU  54  to enable the CPU  54  to monitor the magnitude or amplitude of a current within the motor  34 . The CPU  54  may be programmed to use the magnitude of the motor current in conjunction with other data to ensure that the door control system  12  operates safely.  
         [0029]    Any device suitable for monitoring the door panel operation may be employed in place of the encoder arrangement disclosed. Thus, the invention is not intended to be limited to the exemplary encoder-type monitoring device disclosed.  
       Exemplary Computer Program for Fail Safe Automatic Door System Operation  
       [0030]    [0030]FIGS. 5 and 6 show a block diagram for an exemplary computer program that utilizes feedback data from the encoder  68  and motor current data to provide fail safe operation of the door control system  12 . The program comprises a series of instructions executable by the CPU  54  and may be provided on an EPROM chip or stored in a non—volatile memory of the processor  54 . Alternatively, the program may be permanently embedded in the processor as a part of its circuitry. With respect to FIG. 5, the program begins at title block  90 . The motor  34  is in its off condition (so the door panel  16  is not moving) and the door panel  16  may be either fully open or fully closed at block  90 . The CPU  54  waits for an operator input signal at  92 . When a signal is received (from a wireless device such as a remote control key fob, for example) the CPU  54 , in response, sends control signals to the motor controller  56  (which may be, for example, a pulse width modulator) and to the switch  58  (which may be, for example, a relay) at  94 . These control signals cause the pulse width modulator  56  to generate a power signal to drive the same at a selected speed and in a selected direction (as determined by the CPU  54 ) and may cause the switch element in the relay  58  to close, thereby enabling the power signal generated by the pulse width modulator  56  to be communicated to the motor  34 .  
         [0031]    The CPU  54  measures the encoder pulses on channels A and B at  96  and  98 , respectively. At  100 , the CPU  54  determines if a pulse has been detected on channel A. If there has not been a detected pulse (that is, if there has been no change in signal level on channel A), the CPU  54  determines whether or not there has been a detected pulse within the past half second (the CPU  54  may be programmed so that this time period is variable) at  104 . If there has been no change in signal level on channel A but less than half of second has passed since the last detected signal level or since door opening (or closing) movement has been initiated, program execution proceeds to  102  to determine whether or not there has been a detected change in signal level on channel B. If there has been a detected change in signal level on channel B at  102 , program execution proceeds to block  113  (FIG. 6). If there has been no change in signal level on channel B at  102 , program execution proceeds to  106  to determine whether less than half of second has passed since the last detected signal level or since door opening (or closing) has been initiated. If a half second has not elapsed since the last detected signal on channel B (or since door movement was initiated), program execution proceeds to block  113  (FIG. 6). If there is no detected change in signal level on channel A and/or channel B for a half second or more, the CPU  54  instructs the pulse width modulator to terminate delivery of the electric power signal to the motor  34  and affects movement of the switch to its open position at  108  and  110 , respectively. Blocks  96 - 106  in effect operate to ensure that the motor shaft begins rotation after a power-on event is commanded by an operator at block  92  and to ensure that the motor shaft rotation continues until the door is fully open (or closed). For example, if no motor shaft  70  movement is detected after a half second following the receipt of a power-on command from an operator at  92 , the CPU  54  shuts down the door control system  12  because such a condition is indicative of an obstruction being present which prevents the door panel  16  from moving or for some other reason.  
         [0032]    Block  113  is a title block. The CPU  54  measures the motor current at  114  and compares the measured motor current with the expected motor current at block  116 . The expected motor current level may be a function of both door panel  16  position and of the commanded motor speed. If the CPU  54  determines at  116  that the measured motor current is above the expected value or limit, this may indicate that the door has encountered an obstruction or that an attempt is being made to move the door panel  16  manually, and the CPU  54  may respond by (1) commanding the pulse width modulator to terminate delivery of its electric power signal to the motor  34  and (2) by opening the relay switch at  118  and  120 , respectively.  
         [0033]    The CPU  54  compares the actual motor speed with the commanded motor speed at blocks  122 - 130 . Blocked  122  is a title block. The CPU  54  may be programmed to measure the actual motor speed at  124  based on, for example, the widths of the pulses received from either the A channel or the B channel. The CPU  54  compares the measured motor speed with the target or commanded motor speed at  126 . If the measured speed is greater than the commanded speed, the CPU  54  may be programmed to (1) command the pulse width modulator  56  to stop sending a power signal to the motor  34  and (2) to open the relay switch  58  (and thereby open the transmission path of the electric power signal from the motor controller  56  to the motor  34 ) at  128  and  130 , respectively. If the measured speed is greater than the commanded speed, this may indicate that a person is attempting to manually move the door panel  16  (in the same direction in which the motor  34  is moving it) or that the pulse width modulator  56  has malfunctioned, thus causing the door panel  16  to move faster than its commanded speed. If the measured speed is not greater than the commanded speed, program control goes back to block  94 . As explained below, when the pulse width modulator is shut down and/or the relay is open, the door panel  16  is in manual mode. In manual mode, the door panel  16  is no longer being driven by the motor  34  and the door panel  16  can be moved to manually. Blocks  94 - 130  continue to be executed as a loop at a relatively higher rate of speed (typically many times per second depending upon several factors which may include, for example, the clock speed of the processor, the total number of instructions required to execute blocks  94 - 130  and the number of clock cycles required per instruction) while the door panel  16  is moving.  
         [0034]    If the door panel  16  is allowed to move to its fully open or fully closed position, it will encounter the door frame  14  (in its closed position) or a door stop or wall (in its fully open position) which will stop door panel movement. This will result in the cessation of pulse signals on the A and B channels and/or an increase in motor current. The CPU  54  may be programmed to shut off the door control system  12  either at blocks  108  and  110  or at blocks  118  and  120  as a result. The CPU  54  may be programmed, for example, to count the total number of revolutions of the motor shaft  70  that have occurred (by counting pulses on the A channel, for example)and the CPU  54  may use this information to determine whether or not door panel movement is stopping as a result of a normal end of cycle movement of the door panel  16  against a stopping structure (such as a door frame or a door stop) or whether door panel movement is stopping because the door panel  16  has encountered an unexpected object in the middle of its range or cycle of movement. If the CPU  54  determines that the door panel is at the end of a cycle, the CPU may be programmed to ignore the rise in motor current and weight for the full half second (or other predetermined time period) before shutting down the control system  12  (to allow re-latching of the door panel in the presence of a door seal, for example).  
         [0035]    It is understood that the control system  12  operation described in FIGS. 5 and 6 is exemplary only and not intended to limit the scope of the invention. FIGS. 5 and 6 are intended to illustrate by way of example one way in which the CPU  54  may be programmed to stop the door panel  16  from moving by commanding the pulse width modulator  56  to de-energize the motor  34  and by opening the relay  58 . It can also be understood that this procedure for de-energizing the control system  12  provides fail safe door panel operation and shuts down the system  12  in the event the door panel encounters an obstruction while moving or in the event that the door panel reaches its fully open (or closed) position.  
         [0036]    It is also contemplated to programmed the CPU  54  to shut down the door control system  12  in the event that a second or subsequent input signal is sent from the operator while the door panel  16  is moving. The CPU  54  may be programmed, for example, to stop power operated door panel  16  movement in an opening or closing direction if an operator-initiated input signal is received that requests door panel movement in the opposite direction from the direction in which the door panel is then moving. For example, if the door panel is opening and the user sends a “closed door panel” request to the CPU  54 , the CPU  54  may be programmed to respond by stopping power operated door panel movement so that the door panel  16  goes into manual mode.  
       Exemplary Circuit for Fail Safe Automatic Door System Operation  
       [0037]    FIGS.  7 - 10  show an exemplary electrical circuit for implementing the fail safe door control system  12 . Most of the circuitry shown in the FIGS.  7 - 10  may be included within the control module  25  mounted on the door panel  16  (see FIG. 2). FIG. 7 shows power supply circuitry  140  for the door control system  12 . The power supply circuitry  140  includes a power source  142 , a step-down transformer  144 , a bridge rectifier  146  and filtering circuitry  148 . A power source  142  (shown schematically in FIG. 7) may be provided by a conventional 120 volt household electrical outlet  149  (see FIG. 1) and the transformer  144  (shown schematically in FIG. 7) may be a 120 volt to a 24 volt wall mounted transformer (see FIG. 1) that is electrically communicated to the control module  25  through an electrical line  151  (FIG. 1). The rectifier  146  (FIG. 7) may be operated to rectify the AC (alternating current) power signal from the transformer  144 . The filtering circuitry  148  includes a plurality of capacitors generally designated  150  and a pair of voltage regulators  152 ,  154  and may be operated to provide DC (direct current) voltages to power the door control system  12 . For example, the circuitry  148  may provide 24 volt, 15 volt and 5 volt DC at  156 ,  158  and  160 , respectively.  
         [0038]    A receiver circuit  162  is shown (enclosed within dashed lines) in FIG. 8. The receiver circuit  162  may receive a signal from an operator controlled wireless remote control device such as a key fob  164  (shown schematically in FIG. 8). An operator-initiated door control signal may be received by an antenna  166  of the receiver circuit  162 , processed and amplified by circuitry within the receiver  162  and sent to an associated decoder microcontroller  168  which may be electrically communicated to the receiver circuit  162  through signal line  170 . Microcontroller  168  may be programmed and operated to decode the information in the received signal from the key fob  164 . The signal sent from the key fob  164  may contain encoded information that includes the desired door panel moving operation requested by the operator and various control and security information. The control and security information may include a manufacturers code for the particular key fob, a unique serial number assigned to the key fob and a random code generated and emitted by each key fob transmitter which may be used to assure secure operation of the door control system  12  to prevent unauthorized users from operating the door system  12 . Electrical lines  174 ,  176 , respectively, may be communicated from the decoder microcontroller  168  to a central processing unit (CPU)  172  (see FIG. 9) of control circuitry to communicate timing (or clock) data and control data to the CPU  172 .  
         [0039]    The control circuitry is shown in FIGS. 9 and 10 and includes the CPU  172 , a motor drive control module or motor driver  180 , an H-Bridge circuit  182  and a switch assembly in the form of a relay  184 . The CPU  172  may be programmed and operated to control and monitor the door control system  12  to open and close the door panel  16  and provide fail safe door operation. The CPU  172  is communicated to a plurality of electrical circuits and circuit components including a dip switch block  186 , a clock frequency generating circuit  188  which may include a crystal  190 , a programming interface  192  and an LED status indicator light  194 .  
         [0040]    The control circuitry can best be understood through an example of how the circuitry can be operated to control and provide fail safe operation for a door panel. For the purposes of illustration, it will be assumed initially that the door panel is closed and that it encounters no obstructions while opening. Generally, to open the door panel, an operator sends a door open command signal to the CPU  172  either through a wireless device such as key fob  164  or through a hardwired device  196 , such as infrared, Doppler or microwave motion and/or presence detector. If the key fob  164  is used, the door open command signal from the key fob  164  is received, decoded and communicated to the CPU  172  through the receiver circuit  162 , the decoder microcontroller  168  and electrical line  176 . If the hardwired device  196  is used, the open command signal is sent to the CPU through an electrical conductor  198  of a ribbon header  200  which may be used to electrically communicate a wide range of devices to the control circuit including the hardwired device  196 .  
         [0041]    The CPU  172  in response to receiving the open command may be programmed to respond by unlatching an electrically operated strike assembly  202  (shown schematically in FIG. 1) to unlatched the door panel  16  and then, a predetermined period of time later, close a switching element  204  in the relay  184  by causing an electrical current true flow through an inductor  206 . The CPU  172  is communicated to the inductor through a transistor  208  and may cause current to flow through the inductor  206  by causing the transistor  208  to be appropriately biased. The CPU  172  may be a PIC16C73B processing chip commercially available from Microchip Technology, Inc., 2355 West Chandler Blvd., Chandler, Ariz. 85224-6199.  
         [0042]    The CPU  172 , further in response to receiving the open door command from the key fob  164 , may be programmed to respond by causing control signals to be sent to the motor driver  180  over electrical lines  210 ,  212 . The motor driver  180  may be a motor control chip such as an HIP4081A Motor Control Chip commercially available from INTERSIL. The motor driver  180  is electrically communicated to the H-Bridge by electrical conductors  214 ,  216 ,  218 ,  220 . The motor driver  180  and the H-Bridge  182  together may comprise the motor controller electrically communicated between the CPU  172  and the electrical motor  34  and together may provide a pulse width modulated electrical power signal to the motor  34  to control motor speed and direction. It is understood, however, that this embodiment of the motor controller is exemplary only and not intended to limit the scope of the invention. The motor controller any type of device that is capable of controlling the operation (speed and direction) of the electrical motor. Motor speed and direction could be controlled, for example, by a CPU. In these embodiments, the CPU would, in effect, be considered the motor controller. The signals sent from the CPU  172  to the motor driver  180  in effect function as speed and direction reference signals for controlling the speed and rotational direction of a motor  34 . In response to these signals, the motor driver  180  operates to control the speed and direction of the motor  34  through the H-Bridge  184 . The H-Bridge  184  includes four transistors  226 ,  228 ,  230 ,  232  and associated circuitry and can be operated in a known manner to supply the pulse width modulated power signal. The H-Bridge  184  is electrically communicated to the motor  34  through electrical line  222  and through electrical line  224  from the relay  184 . The lines  222 ,  224  are connected to the motor  34  through a ribbon connector  226 .  
         [0043]    The control circuit includes a current overload amplifier circuit generally designated  238  which provides a feedback signal from the H-Bridge  184  to a disable input or pin  240  on the motor driver  180  through conductor  241 . The feedback circuit  238  operates to sample and amplify the current flowing between the H-Bridge  184  and the motor  34 . If the amplitude or magnitude of the current flowing from the H-Bridge  184  to the motor  34  rises above a predetermined level, the circuit  238  will disable the motor driver  180 , thereby protecting the motor driver  180 , the H-Bridge  184  and the associated circuitry. The circuitry  238  also provides an external amplifier circuit which protects the motor  34  by monitoring the voltage across a resistance in series with the motor  34  (and thereby monitors a motor current). This feedback signal is communicated to the CPU  172  through transmission line  242 . The detected voltage is amplified between 0 and 5 volts. The CPU  172  is programmed to evaluate the feedback voltage as a function of the position of the door panel  16  in its range of motion. This is because it is expected that there may be an increase in motor current when the door panel  16 , for example, initially starts movement (and therefore may have to “break” the seal with a door seal on the door jamb) and that there will be less motor current during unobstructed movement of the door through an intermediate portion of its range of movement.  
         [0044]    The CPU  172  may be programmed to move the door panel  16  between closed and open positions at a predetermined speed. The CPU  172  may monitor the actual speed of the motor  34  (and therefore of the door panel  16 ) through speed feedback signals received from the position encoder associated with the motor shaft of the motor  34 . The electrical lines  234 ,  236  carry signals from the A and B channels, respectively, of the shaft encoder of the motor  34  to the CPU  172 . The CPU  172  may be programmed to adjust the speed of the motor  34  in a closed loop fashion using an algorithm for a PID controller that may be included as part of the software program executed by the CPU  172  during door panel movement. The PID controller may generate an output pulse width modulated signal with a frequency of 20 kHz. The CPU  172  may be programmed to count the total number of rotations of the shaft of motor  34  and to use this data to calculate the position of the door within its range of movement between closed and open positions. The CPU  172  may further be programmed to utilize the door panel position information of the door panel to control the output of the motor  34  so that door panel speed is a function of door panel position. For example, when the door panel  16  has moved outwardly from the door jamb  14  in the opening direction more than 15 degrees, the CPU  172  may be programmed to limit the duty cycle of the motor  34  to approximately fifty percent of its maximum output.  
         [0045]    The CPU  172  may be programmed to monitor the movement (i.e., speed, direction and position) of the door panel  16  as described above in connection with the diagrams of FIGS. 5 and 6. When the CPU  172  is so programmed, door panel  16  movement in the opening direction continues until the door panel  16  reaches the end of its travel path (because, for example, the door panel  16  encounters a doorstop). The CPU  172  may be programmed to shut off the door control system  12  according to the method of FIGS. 5 and 6. Thus, when the door panel  16  is fully opened and stopped against the door stop, the motor shaft will stop rotating (resulting in a cessation of signals on lines  234 ,  236 ) and the motor current may also rise. The CPU  172  may be programmed to respond to one of these events (cessation of the motor shaft rotation or increase in motor current) by (a) de-energizing the motor  34  and (b) opening the switch element  204  of the relay  184 . It can be understood, for example, that which of these two events the CPU  172  is programmed to respond to may vary, depending upon the particular door assembly the CPU is controlling. For example, if the door jamb includes a resilient weather seal, the CPU  172  may be programmed to allow the motor current to rise to a relatively high level (relative to the “normal” current level measured during unobstructed door panel movement) when the door panel has closed sufficiently to contact the door seal to allow compression of the seal and subsequent latching of the door panel in its closed position. In this instance, the CPU  172  may ignore the current rise and de-energize the door system  12  in response to the cessation of motor shaft rotation for a predetermined time period. It can also be understood that the particular event which causes the CPU  172  to de-energize the door control system  12  may vary depending upon the particular door assembly being operated and on choices made by the programmer programming the CPU  172 . Thus, this event is of secondary importance and it should be recalled that the focus of the present invention is the fail safe operation of the door operating system provided by the redundant actions of (1) commanding the pulse width modulator  180 ,  182  to stop transmitting and electrical power signal to the motor  34  and (2) opening the switch element  204  of the relay  184  to thereby open or “break” the transmission path for the energy signal between the motor controller (that is, in this particular instance between the H-Bridge) and the motor  34 .  
         [0046]    More specifically, the CPU  172  de-energizes the motor  34  by commanding the motor driver  180  of the motor controller through control lines  210 ,  212  to stop operating the H-Bridge  184  to drive the motor  34 . The CPU  172  further responses to stop door panel movement by switching off the current to the inductor  206  of the relay  184  to open the switching element  204 . It can be understood from FIGS. 9 and 10 that the switching element  204  is in series between the motor controller and the motor  34 .  
         [0047]    The fail safe nature of the door control system  12  is advantageous because, if the motor driver  180  of the motor controller fails to respond when the CPU  172  commands the same (through lines  210 ,  212 ) to de-energize the motor  34 , the motor  34  will still be shut off because the CPU  172  will stop the current flow through inductor  206  and thereby cause the switch element  204  to move from its closed position through its open position.  
         [0048]    Because the CPU  172  operates to monitor the position, direction of movement and speed of the door panel  16  and to monitor the motor current during a door panel moving operation, the CPU  172  can be adapted (either by software programming or hardwired programming) to respond to any predetermined condition that is indicative of an unsafe and/or abnormal condition that may arise during a door moving operation and thereby protect both the circuitry and any people who come in contact with the moving door panel  16 . Therefore, it can be understood that the fail safe operation of the shut-off mechanism for the door control system  12  provided by the relay  184  provides fail safe operation both during routine opening and closing of the door panel  16  and in emergency situations. For example, if the door panel encounters an unexpected obstruction, there may be no encoder pulses for a predetermined period of time (as for example a half a second as used in the example program described above). In this event, the CPU  172  may respond (according to the method of FIGS. 5 and 6, for example) by commanding the motor driver  180  of the motor controller to stop communicating a power signal through the motor  34  and by opening the switch element  204  of the relay  184 .  
         [0049]    When the CPU  172  de-energizes the motor  34 , the door panel  16  may go into manual mode. That is, the door control system  12  may go into manual mode by opening the switch element  204  of the relay  184  and by commanding the pulse width modulator  180 ,  182  to stop sending a power signal to the motor  34 . Thus, the door panel  16  may go into manual mode whenever the door panel  16  is fully open, fully closed, or when a failure occurs. When the switch element  204  of the relay  184  is open, there is no electrical load on the motor. The only load on the motor  34  is provided by the transmission  38  and any frictional resistance that is provided from the linkage assembly  26 . This has several advantages. For example, this reduces the resistance to door movement in manual mode making the door panel  16  easier to move manually. The opening of the switch element  204  of the relay  184  also prevents any electrical damage that may occur to the CPU  172 , to the motor driver  180  (both of which may be computer “chips”), or other components of the control circuitry which may otherwise be damaged from an induced current caused by back-driving of the electric motor while moving the door panel  16  in manual mode. The CPU  172  includes an emergency stop pin  252  that may accept a signal to stop door panel movement instantly and cause the automatic door operating system to go into manual mode.  
         [0050]    While the invention has been disclosed and described with reference with a limited number of embodiments, it will be apparent that variations and modifications may be made thereto without departure from the spirit and scope of the invention. Therefore, the following claims are intended to cover all such modifications, variations, and equivalents thereof in accordance with the principles and advantages noted herein.