Abstract:
A system for controlling access to a secured building area can include a programmable logic controller that is used to interpret data encoded on cards presented to a card reader at a locked door. The logic controller has one processor for decoding input signals, and another processor for comparing decoded data with data in a database, for thus generating a door-unlock signal. The programmable logic controller determines the permissions associated with the data encoded on the card presented, and unlocks the door if such access is permitted. Ancillary systems are easily integrated into the control system due to the modularity of a programmable logic controller-based system. Fire alarm override, burglar alarm systems, and infant security systems may be integrated into the system disclosed.

Description:
BACKGROUND 
     This invention relates to a security system for controlling access to a building or secured area. Security systems for buildings are typically available in a variety of types and complexity. Generally, most modern security systems utilize an identification card or badge having encoded data therein. The identification card or badge acts as the “key” to unlock doors. One seeking to gain access through a locked door presents the identification card or badge to a card reader. If the bearer of the card or badge is granted permission, the door is unlocked. 
     A security system using electronically detectable identification cards or badges requires a control system that can decode the data encoded in the identification card or badge, and determine the access permission before signalling the actuation of the door lock. A computer-controlled system is typically used. A central computer having a database of access permissions for all active identification cards or badges is employed. These computer-based systems are readily available and are in common use today. 
     The problem presented to the use of the prior art security systems is the expansion of the system to accommodate growth, and the integration of the security with ancillary systems that would enhance the operation and administration of security within the building or secured area. A security system in a building having public access, for example, may employ a conventional computer-based access control system. To incorporate a fire alarm system to allow for emergency egress, and override the electronic door locks is difficult to perform while still retaining any logic functions in the security system. The typical override in a conventionally integrated system is to shut down the security system, and unlock all doors. This condition, though certainly effective in the event of a fire, may constitute a breach of security in a false alarm situation. 
     A security system in a hospital may utilize an infant protection system that triggers an alarm when an infant is moved in an unauthorized manner to an exit to the maternity ward. Typically, the infant wears an unobtrusive transmitting unit on its ankle, wrist, or umbilical cord, that is detected by monitors installed at the ward exits. An alarm condition may be used for a signal to lock the door, thereby thwarting any attempted abduction of the infant. While these systems allow for override when an authorized staff member relocates a protected infant, the system and its override control is administered separately from a centralized building control system. 
     Additionally, integration of a separate infant control system to a door locking security system and a fire alarm system, is logistically difficult to achieve while maintaining any centralized administration. One attempting to abduct an infant need only trigger the fire alarm to create a distraction, and override the door locking functions, to facilitate his misdeeds. Preferably, a system that integrates the fire alarm, infant protection, and door locking system would retain operation in selected areas, allowing for authorized, and controlled, exit at all times. 
     The invention described herein addresses the need for a flexible and easily adaptable system for controlling the areas of ingress and egress to, from, and within a building or secured area. The use of a programmable logic controller in place of a conventional computer-based central processing unit allows for this needed expandability, modularity, while providing for ease of programming. 
     Programmable logic controllers are traditionally used in process control applications in manufacturing and industrial environments. They are particularly adapted to controlling steps that occur at specific times and in a specified sequence according to various parameters, or steps that occur in response to specific events. 
     The programmable logic controller is a computerized relay bank; for a given or expected input, an output signal is generated in response. The logic incorporated into the programmable logic controller may be depicted in the form of a ladder logic diagram. The programmable logic controller steps through the ladder in a scan of its input ports, changing the state of the output ports accordingly. 
     A programmable logic controller is inherently expandable due to its modular design. Additional ports may be added by merely plugging in a new input-output module into the controller. Additionally, program changes and additions may be readily implemented as a result of the intuitive ladder logic program structure. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is directed to an apparatus that satisfies the need for a modular and flexible control system for an access and control system for a building or secured area. The use of a programmable logic controller in place of a conventional computer-based central processing unit allows for expandability, modularity, and ease of programming. Ancillary systems may be readily interfaced by coupling to an input port, without having to reconfigure the entire system. 
     In summary, and in accordance with the above discussion, the foregoing objectives are achieved in the following embodiments. 
     A programmable logic controller, having a database of personnel information resident in its memory is used to control access through a door to a secured area. The programmable logic controller has a basic module for co-processing functions, and an input-output module. A card reader is placed at the secured door location, and is coupled to the basic module of the programmable logic controller. An electronically actuated door lock that secures the door in a locked state is coupled to an output port of the input-output module. An encoded identification badge is presented to the card reader by one seeking access through the secured door. The encoded identification number from the badge is decoded by the basic module, and compared to the authorization and permissions associated with the identification number in the database. If the permissions associated with the identification number permits access, the door is unlocked by changing the state of the output port coupled to the door lock at the secured door. 
     In accordance with an aspect of this invention, there is provided the ability to condition the actuation of the door lock through the signalling of an alarm from an ancillary system coupled to an input port of the input-output module. Alarm signals from additional ancillary systems may, in combination, further condition the actuation of the door lock. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is schematic view of the Access Control System, constructed according to the present invention. 
     FIG. 2 is a flowchart schematic of the system operation. 
     FIG. 3 is a ladder logic diagram depicting a portion of the operation of the card reading function of the system. 
     FIG. 4 is a flowchart of the system with an ancillary alarm input. 
     FIG. 5 is a schematic view of an infant protection system using the Access Control System, constructed according to the present invention. 
     FIG. 6 is a flowchart of the system with multiple ancillary alarm inputs. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring particularly to FIGS. 1 through 6 thereof, there is shown an access and control system for controlling access to, from, and within a secured building or area. 
     FIG. 1 is a schematic view of the Access Control System  10 . The heart of the system comprises a programmable logic controller  11 , a basic module  12 , and at least one input-output module  13 . Typically, multiple input-output modules  13  will be mounted in a rack  14 . 
     An Allen-Bradley 580e PLC, or equivalent, has been successfully used as the basis of a security system for the programmable logic controller  11  according to the present embodiments. The system includes power supply modules for converting available power to meet the requirements of the programmable logic controller  11 . The system also includes memory for retaining the programming logic, and a first processor for performing logic functions. 
     In the most basic embodiment, according to FIG. 1, the system must also include a card reader  15 , a door lock  16 , a door  17 , and an identification badge  19  that may be worn by a person  18 . The identification badge  19  is a commonly known and used credit-card sized badge that may be encoded with an identification code using a bar code printed on the surface, a magnetic stripe placed on the surface, and/or a proximity emitting device embedded therein. The card reader  15  must be matched to detect any or all of the data encoding methods, i.e., magnetic stripe, bar code, and/or proximity sensing. Presenting the encoded identification card  19  to the card reader allows the system to determine that a person seeks access to the area secured by the locked door  17 . Presumably, alternative means can be employed to uniquely identify a person to a detecting equivalent of a card reader  15 . Retinal scan, fingerprint detection, and voiceprint are such alternatives. 
     The door lock  16  must be capable of being actuated from an electrical signal source. It may physically engage a bar  16   a  into the door  17  that may be extracted when actuated in a solenoid fashion. Similarly, an electronically actuated latch plate may be used for the door lock  16 . Alternatively, the door lock  16  may constitute a magnetically actuated element that creates a magnetic field when locked, thereby attracting a metal plate secured to the door  17 . The magnetic attraction of the plate on the door  17  to magnetically actuated door lock  16  creates resistance to opening that effectively locks the door  17  from ingress or egress. 
     The door lock  16  is coupled to an output port of the input-output module  13  of programmable logic controller  11 . The programmable logic controller  11  may set the state of the output port coupled to the door lock  16  through a door lock signal cable  23 , thereby locking or unlocking the door  17 . Low voltage direct current is typically used, though nearly any signalling requirements may be accommodated through conversion adapters. The door lock may be configured as normally open, or normally closed, depending upon the security impact in the event of power failure. Safety concerns may dictate that a complete power failure must allow for personnel to exit safely through the door secured by door lock  16 . 
     The card reader  15  is coupled to the basic module  12  of the programmable logic controller  11 , as shown in FIG. 1 by a communications cable  22 . When an identification badge is presented to the card reader  15 , the encoded identification number is transmitted to the programmable logic controller  11  through communications cable  22 . In the present embodiment, an RS-485 data highway bus has been found to be successful for the communications cable  22 . Up to 32 card readers may be connected to a single RS-485 bus, over a total distance of up to 4,000 feet. The modular connection of subsequent card readers  15  allows for expansion of the system as facility growth requires. 
     The function of the basic module  12  is to co-process the identification of the encoded card data from identification card  19  so that the processor of the programmable logic controller  11  is not overloaded, so that processing scan times are minimized. An Allen Bradley SLC-504 has been selected for use in the present embodiment to perform this function. The basic module  12  contains a second processor with memory, and is coupled directly to the memory and processor of the programmable logic controller  11 . The basic module  12  receives the data read by card reader  15 , and decodes the data to a format that can be compared to the access permissions list in the database resident in the programmable logic controller  11 . A table containing a list of identification numbers of cards set up in the system resides in the memory of the programmable logic controller  11 , and the associated personal identification number, typically, the social security number unique to each employee or person requiring access. A table lookup function is performed by the basic module  12 , and using a block transfer mode, passes the personal identification number to the main processor in the programmable logic controller  11 . 
     FIG. 2 depicts a flowchart for the operation of the basic embodiment of the Access Control System. A first step  25  determines if there is data to be read by card reader  15 . if there is no data, i.e., there is no person seeking access, the program continues to loop. If data is present, the data is read at second step  26 , and converted through a table lookup function at step  27 . The programmable logic controller  11  compares the data read and converted to the list of permissions and associated identification numbers at step  28 . If the person seeking access does not have the permissions necessary to gain access, the program continues its loop and any subsequent door unlocking routines are not run, as depicted in step  29 . If access is authorized, the programmable logic controller  11  then sets an output port state to unlock the door where access is sought at step  30 . A delay at step  31  may be executed to pause while the door is opened. The programmable logic controller then sets the output port state to lock the door at step  32 , and resets the card reader to allow more data to be read at last step  33 . 
     Additional secured sites may be added to the system by adding a card reader  15  to the communications cable  22 , and connecting another door lock  16  to another output port of the input-output module  13  of the programmable logic controller  11 . Both the new card reader  15  and door lock  16 , and any subsequent sites, must be within range of the RS-485 communications requirements, or equivalent, using the communications cable  22  and the door lock signal cable  23 . 
     A remote processing unit may be configured to extend the range and number of secured sites by adding an additional basic module  12  and additional input-output modules  13  in a remotely placed rack  14 . These units may be remotely placed, while coupled to the programmable logic controller  11  through the communications cable  22 . 
     The flowchart depicted in FIG. 2 is then subsequently performed for each site in sequence by the programmable logic controller  11 . The system is programmed through the use of a ladder logic, a portion of which is depicted in FIG.  3 . The complex decision making process is reduced to a series of boolean operations that are performed sequentially. 
     The programmable logic controller  11  scans sequentially through the ladder structure. At rung  47 , normally open switch  41  is closed if there is new data presented at the card reader  15 . The. coil  42   a  is then turned on, which signals a transfer of data from the card reader  15  to the basic module  12 . Upon completion of the data transfer, normally open switch  42   b  is closed. When switch  42   b  is closed, coil  43   a  is turned on, which triggers. the next step in the process. The programmable logic controller  11  scans rapidly through the entire ladder structure continuously, so that there is no delay or apparent pause in the processing of any one step. 
     The ladder structure may be programmed into the programmable logic controller using known methods and commercially available control program software packages; RS-Logics being one example. A personal computer  35  coupled to the programmable logic controller  11  through a network cable  36  allows for programming, and database administration from the remote personal computer  35 . Commercially available software, such as RS-Links, may be used to facilitate communication between the programmable logic controller  11  and the personal computer  35 . 
     The database resident in the programmable logic controller  11  may be synchronized with a central personnel database for the facility, so that changes in staff or authorization may be kept current. The synchronization may be performed at regular intervals, or manually initiated upon demand. The central database may reside in most commercially available database management systems, including MS-Access, and Oracle. The database need only be accessible through the network coupled to the programmable logic controller  11  through network cable  36 , and capable of exchanging records dynamically. 
     Additionally, the access control system  10  may be monitored graphically through the personal computer  35 . Commercially available software, such as RS-View permits administrators to view the programmable logic controller  11  functions using simulation techniques. Monitoring of the system, though not required for system operation, allows for system design, troubleshooting, and optimization. 
     One of the key features of the access control system  10  is the ability to integrate ancillary systems into the overall building protection system. Logic determining access permissions may be conditioned upon a signal of a superseding event. For example, a door normally unlocked may be locked in an alarm condition, though one with access permissions may present their card to the card reader at the locked door, and be granted access. 
     An ancillary system  20  is coupled to an input port of the input-output module  13  of the programmable logic controller  11  through input cable  24 . The ancillary system  20  signals the alarm condition through input cable  24  by changing the state detected at the input port of input-output module  13 . This ancillary system  20  may be a fire alarm, burglar alarm, broken window sensor, infant security system, motion detector, panic button, or any subsystem within a building that when signalling an alarm may impact the decision to lock (or unlock) a door. 
     The ancillary system  20  is typically coupled to the input port of input-output module  13  in a normally closed fashion so that tampering, or failure of the subsystem, results in an alarm condition. 
     Multiple ancillary systems  20  may be integrated into the access control system  10  through the availability of, or expanded availability of, additional input ports in the input-output module  13  of the programmable logic controller  11 . The ladder logic in the memory of the programmable logic controller  11  must then accommodate the ancillary system, though it would be treated as just another step its continuous scan during operation. 
     FIG. 4 depicts a flowchart for the operation of the access control system  10  with an ancillary system installed. The flowchart depicts the situation for a normally open door to be locked in an alarm condition, though granting access to those having permissions assigned in the database resident in the programmable logic controller  11 . 
     During the continuous scan of the ladder logic structure, an alarm condition will be observed when an input port of input-output module  13  assigned to the alarm is switched (e.g., by opening a normally closed circuit). A first step  50  determines if an alarm condition exists; if no alarm is observed, the scan continues. If an alarm is observed, the output port of input-output module  13  assigned to the door  17  to be secured is set to lock, as shown in step  51 . With the door  17  now locked, access to the secured area is controlled through the permissions associated with an identification card  19  presented to the card reader  15  at the secured door  17 . 
     Step  50  determines if there is data to be read by card reader  15 . If there is no data, i.e., there is no person seeking access, the program continues to loop. If data is present, the data is read at step  53 , and converted through a table lookup function at step  54 . The programmable logic controller  11  compares the data read and converted to the list of permissions and associated identification numbers at step  55 . If the person seeking access does not have the permissions necessary to gain access in the alarm condition, the program continues its loop and any subsequent door unlocking routines are not run, as depicted in step  56 . The database may be configured to allow access during no alarm condition, while restricting access during the alarm. 
     If access is authorized, the programmable logic controller  11  then sets the state of the output port assigned to door lock  16  at locked door  17  to unlock the door where access is sought at step  57 . A delay at step  58  may be executed to pause while the door is opened. The programmable logic controller  11  then sets the state of the output port to again lock the door at step  59 , and resets the card reader to allow more data to be read at last step  60 . 
     During any subsequent scan, if the alarm state has. ended (e.g., by closing the normally closed circuit to the ancillary system  20 ), the locked door will be unlocked at step  61 . The programmable logic controller  11  is instructed to set the state of the output port assigned to the door lock  16  of the locked door  17  to be unlocked. 
     The process depicted in FIG. 4 may be exemplified through an embodiment of the invention installed in a hospital having a maternity ward with infant protection as shown in FIG.  5 . High traffic and a desire for public access dictates the need for normally unlocked doors, that automatically lock when an infant is being removed in an unauthorized fashion. Infant protection systems typically comprise a transmitting device  65  affixed to the ankle or clothing of an infant  66 , and a proximity receiving device  67  mounted near a door  17  or exit. Asportation of the infant  66  wearing the transmitting device  65  towards the door  17  near the receiving device  67  triggers an alarm. The alarm condition may be used to signal the locking of the door, thereby thwarting abduction of the infant. 
     Integration of the infant protection system into the Access Control System  10  may be facilitated through a coupling of the alarm signal from the receiving device  67  to an input port of input-output module  13  through input cable  24 . Hospital staff authorized to transport infants out of the maternity ward may then present the identification card or badge  19  to the card reader  15 . If the permissions in the database in the memory of the programmable logic controller  11  associated with the identification badge presented authorize the transfer of the infant  66 , then the door lock  16  will be released. 
     While a stand-alone infant security system is commonly known and used, its integration into an access control system having a common database with hospital staff records and authorizations is provided by the present invention. Additionally, enhancements to the operation of the system may be provided through logic applied to conditions external to the infant security system. 
     The ancillary system  20  exemplified as an infant security system may be further enhanced through the addition of a plurality of ancillary systems, all integrated in combination as a plurality of input signals to the input-output module  13  of the programmable logic controller  11 . For example, one attempting to abduct an infant may create a distraction by first triggering a fire alarm. A prior art access control system will, by default, be preempted by a fire alarm so that safety of personnel is not compromised in the event of fire. In the present invention, a fire alarm condition in the maternity ward need not default to unrestricted egress. FIG. 6 depicts a flowchart that describes the operation of the Access Control System with a plurality of alarm conditions. 
     During the continuous scan of the ladder logic structure, an alarm condition will be observed when an input port of input-output module  13  assigned to the alarm is switched (e.g., by opening a normally closed circuit). A first step  75  determines if an alarm condition exists; if no alarm is observed, the scan continues. The door, normally unlocked, remains accessible to all. If an alarm is observed, the output port of input-output module  13  assigned to the door  17  to be secured is set to lock, as shown in step  76 . A delay of thirty seconds occurs, during which time one authorized to egress may present his identification badge  19  to the card reader  15  to unlock the door  17 . 
     In the embodiment of the invention as it is deployed in an infant protection system, this counter-intuitive step to. lock all exit doors upon the initial trigger of a fire alarm for thirty seconds allows for the staff to ensure that there was no intentional false alarm to create a distraction to facilitate the abduction of an infant. 
     During the thirty second delay, a staff member may unlock any door to the area by presenting the identification badge  19  to the card reader  15 . Step  78  determines if there is data to be read by card reader  15 . If there is no data, i.e., there is no person seeking access, the program continues to loop. If data is present, the data is read at step  79 , and converted through a table lookup function at step  80 . The programmable logic controller  11  compares the data read and converted to the list of permissions and associated identification numbers at step  81 . If the person seeking access does not have the permissions necessary to gain access in the alarm condition, the program continues its loop and any subsequent door unlocking routines are not run, as depicted in step  82 . The database may be configured to allow access during no alarm condition, while restricting access during the alarm. 
     If access is authorized, the programmable logic controller  11  then sets the state of the output port assigned to door lock  16  at locked door  17  to unlock the door where access is sought at step  83 . A delay at step  84  may be executed to pause while the door is opened. The programmable logic controller  11  then sets the state of the output port to again lock the door at step  85 , and resets the card reader to allow more data to be read at last step  86 . 
     During any subsequent scan, if thirty second delay has completed, the alarm signal will be reset at step  87 , and the locked door will be unlocked at step  88 , thereby resuming normal operation. 
     The present invention, described above, relates to a system for controlling access to a secured area. Features of the present invention are recited in the appended claims. The drawings contained herein necessarily depict structural features and embodiments of the Access Control System, useful in the practice of the present invention. 
     However, it will be appreciated by those skilled in the arts pertaining thereto, that the present invention can be practiced in various alternate forms, proportions, and configurations. Further, the previous detailed description of the preferred embodiment of the present invention are presented for purposes of clarity of understanding only, and no unnecessary limitations should be implied therefrom. Finally, all appropriate mechanical and functional equivalents to the above, which may be obvious to those skilled in the arts pertaining thereto, are considered to be encompassed within the claims of the present invention.