Patent Publication Number: US-6982628-B1

Title: Mechanism for assigning an actuator to a device

Description:
BACKGROUND OF THE INVENTON 
     FIELD OF THE INVENTION 
     The present invention relates to a mechanism for assigning an actuator to a device mechanism of this type, in the form of an access control system, is known from European Patent Application No. 285 419. The mechanism described enables an interrogation unit to unambiguously identify an assigned transponder from a group of multiple transponders located at the same time within access range of the interrogation unit through step-by-step interrogation of the transponder codes. The latter are designed in the form of multi-digit binary words. During the first interrogation step, the interrogation unit checks whether the first digit in the binary code word corresponds to the first digit of a reference code word provided in the interrogation unit. The transponders for which this check has a negative result are ignored for the remainder of the check. In a second interrogation step, the interrogation unit checks the remaining transponders to see whether the second digit in their binary code words correspond to the second digit of the reference code word in the interrogation unit. This process is repeated until only one transponder remains whose entire binary code corresponds to the reference code in the interrogation unit. To unambiguously identify one of 2n transponders, at least n such interrogation steps are needed. Selecting a specific transponder from a number of transponders in this manner qualifies the known mechanism for access protection applications, especially for situations in which an adequate amount of time is available for performing the identification process. In practice, however, the assignment of an actuator to a corresponding device must frequently be done as quickly as possible, for example in access systems for locking and unlocking doors. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide an assignment mechanism which makes an unambiguous assignment quickly, at the same time guaranteeing adequate security. 
     This object is achieved by a mechanism with the features of the main claim. According to the present invention enables one or more actuators from a group of actuators to be clearly identified in just one interrogation-response step. To provide security for the assignment made, this step is suitably followed by an exchange of changing, encrypted codes between the participating elements. The mechanism according to the present invention makes it possible to assign multiple authorized actuators to a single device. After being interrogated by a scanning signal emitted by the device, each actuator responds at the end of a period of time that is characteristic for that specific actuator. In a preferred application in doors, the transmission of a scanning signal by the device, for example the door locking mechanism, is suitably triggered when the door handle is pressed. In one advantageous embodiment, the mechanism according to the present invention makes it possible to train the new actuators to the corresponding device. For this, it is useful for one of the actuators to be specially marked, and a training of new actuators is possible only if the specially marked actuator is located within the communication range of the device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a block diagram of an assignment mechanism. 
         FIG. 2  shows a flowchart illustrating the mechanism&#39;s operation. 
         FIG. 3  shows the relationship between the entry time of a contact signal and an actuator. 
         FIG. 4  shows a flowchart illustrating the operation of the assignment mechanism when it is taught to sense new actuators. 
         FIG. 5  shows the structure of a scanning signal. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1 , a device  10  may be, e.g., an access control system for a motor vehicle or a building, a computer, or other consumer goods. An actuator  20  may be functionally assigned to device  10 . The actuator  20  can be, for example, a transponder. Device  10  contains a transceiver  11  for sending and receiving contactlessly transmittable signals via a radio link  30 . Connected to its output is a decoder  12 , which receives the encrypted signals received by transceiver  11  for decoding. To encrypt the signals, a memory  31  containing the necessary information, in particular in the form of a cryptic key code, is assigned to decoder  12 . The decrypted signals are supplied to a downstream microprocessor  13 , which analyzes them and initiates subsequent actions depending on the analysis result. In particular, it controls the transmission of signals via transceiver  11 . Microprocessor  13  is also assigned a memory  15 , which contains, among other things, a serial number  16 , a manufacturer code  17 , and a directory  18  containing the group numbers of actuators  20  assigned to device  10 . Manufacturer code  17  is assigned by the device manufacturer, unambiguously identifying it. Serial number  16  is characteristic of devices  10  and actuators  20  assigned to each other, while the group numbers are used to distinguish between actuators  20  having the same serial numbers and assigned to a common device  10 . Signals to be transmitted via transceiver  11  are usually encrypted. An encoder  14 , which is also connected to memory  31 , is connected for this purpose between microprocessor  13  and transceiver  11  for encoding the signals. Device  10  also has an input device  19 , allowing a user to access microprocessor  13 . Input device  19  can be, for example, a keypad, as indicated in  FIG. 1 ; other embodiments are also possible. 
     Actuator  20  has a transceiver  21  corresponding to the transceiver on the device side for receiving signals transmitted by device  10  or sending contactlessly transmittable signals to device  10 . Like in the device, a decoder  22  for encrypting encoded signals is connected downstream from transceiver  21 . To decode the signals, the decoder is also connected to a memory  31 , whose contents correspond to those of memory  31  on-the device side, and in which, in particular, the cryptic key code used for signal encryption in device  10  is stored. Also connected to decoder  22  is a microprocessor  24 , which processes the signals received via transceiver  21  and encoder  22  and initiates subsequent actions depending on the result. Microprocessor  24  controls, in particular, the transmission of signals to device  10  via transceiver  21 . Transmission is usually encrypted to prevent monitoring or emulation. For this purpose, an encoder  23 , which is also connected to memory  31 , is connected between microprocessor  24  and transceiver  21  (just like in the device) in order to carry out the encoding function. Microprocessor  24  is also assigned a storage device  25 . It includes, in particular, a storage space  16  for storing a serial number, a storage space  26  for storing a group number, and a storage space  27  for storing a manufacturer code. The latter code is assigned by the manufacturer of actuator  20  and unambiguously identifies the latter. The serial number is a code that is characteristic of the overall mechanism composed of device  10  and actuator  20 . It is suitably defined by the manufacturer or possibly by the user of the overall mechanism and is identical to serial number  16  provided in device  10 . The group number is used to distinguish between multiple actuators  20  having the same serial number. It is defined by the user when the mechanism is used. Memory  25  also contains usage information  28  for defining the range of functions of corresponding actuator  20 . If used in a vehicle, for example, usage information  28  can limit the valid action radius of an actuator  20  to a specific value. In an alternative embodiment, usage information  28  can also be stored in the memory of device  10 . 
     A radio link  30  for sending contactlessly transmittable signals between transceiver  11  on the device side and receiver  21  on the actuator side is located between device  10  and actuator  20 . Signals emitted by transceiver  11  on the device side simultaneously reach all actuators  20  located within their range. Infrared signals or high-frequency signals are suitably used as signals. 
     The mode of operation of the mechanism illustrated in  FIG. 1  is explained below on the basis of the flowchart in FIG.  2 . Letters G and B provided in each process step show whether that step takes place in device  10 (G) or in actuator  20 (B). The assignment process is usually initiated by a user operating a mechanical, electrical, or electro-optical trigger mechanism (not shown), which is labeled Step  100 . If used in conjunction with the door of a motor vehicle, the trigger mechanism can involve, for example, pressing the door handle. Based on the subsequently transmitted signal, microprocessor  13  in device  10  transmits a scanning signal via transceiver  11  (Step  102 ). As indicated in  FIG. 5 , the scanning signal essentially includes a start sequence  35 , preferably in the form of a start bit, as well as serial number  16  stored in memory  15 . The signal is suitably not encrypted. The scanning signal transmitted by device  10  is received by transceivers  21  of all actuators  20  located within the range of radio link  30 . After the signal is transferred by decoder  22 , it is checked by microprocessors  24  of all actuators  20  to see if the serial number transmitted with the scanning signal corresponds to serial number  16  stored in memory  25  and serving as the reference signal (Step  104 ). Start bit  25 , which is also transmitted, is used to synchronize microprocessor  24  to the received scanning signal. If the check performed in actuator  20  during step  104  reveals that reference serial number  16  located in memory  25  does not match the serial number transmitted with the scanning signal, actuator  20  switches to a sleep mode (Step  101 ). It no longer participates in subsequent communication with device  10 . 
     If the check performed in Step  104  reveals that the received serial number corresponds to stored serial number  16 , microprocessor  24  prepares a response in the form of a contact signal. The contact signal is a short, simple signal, for example group number  26  of corresponding actuator  20  in bit-encoded form. Like the scanning signal, it is not encrypted. Processor  24  transmits it at the end of a period of time after receiving the scanning signal that is characteristic for actuator  20 . The contact signal is then transmitted in a time window of a predetermined length (Step  105 ). The length of the time window is set so that the contact signal can be reliably assigned by both actuator  20  and the device. 
       FIG. 3  shows a graphical representation of the function of actuator  20  following the check performed in step  104 . In this illustration, the abscissa represents a time axis t, which is divided, for example, into eight time windows F 0  to F 7  and begins upon receipt of the scanning signal by the actuators. The ordinate shows characteristic group number  26  of corresponding actuator  20 . In the example of  FIG. 3 , eight actuators  20  with group numbers  0  through  7  are assigned to device  10 . Let us assume that, of this number, actuators  20  having group numbers  2  and  6  lie within the active range of a scanning signal when the scanning signal is transmitted by device  10 . Both actuators  2  and  6  present respond to the scanning signal by transmitting a contact signal according to Step  106 . In the underlying example, the time of contact signal transmission, i.e., the ordinal number of the selected time window, corresponds to the group number of the corresponding actuator. Actuator  2  therefore transmits its contact signal at the end of time delay T 1  (i.e., time windows F 0  and F 1 ) in time window F 2 , while actuator number  6  transmits its signal at the end of time delay T 6  (i.e., time windows F 0  to F 5 ) in time window F 6 . Receiver  11  of device  10  subsequently receives two offset contact signals, which appear in windows F 2  and F 6  and directly indicate which actuators  20  are located within the range of radio link  30 . 
     Microprocessor  13  now detects actuators  20  that are present by checking time windows F 0  to F 7  in which contact signals were received (Step  106 ). By repeating this process m times, it checks the maximum number (m) of time windows to which actuators can be assigned (Step  107 ). Actuators  20  present are noted by making entries in memory  15  (Step  103 ). If no actuators ( 20 ) are detected, a cancel signal is generated (Steps  108 ,  111 ). Once actuators  20  present have been detected, the mode is set (Step  109 ); the possible modes are assign and teach, as well as additional functions such as delete, block, enable, and the like. For this purpose, microprocessor  13  checks whether a command exists for selecting teach mode. If so, it continues by executing step  200  as explained below. If this command does not exist, microprocessor  13  reaches a decision as to which of existing actuators  20  should participate in the rest of the assignment communication process (Step  110 ). This decision can be reached, for example, by ranking actuators  20 , with somewhat different ranges of functions being assigned to actuators  20 . For applications in motor vehicles, for example, specific actuators  20  can be assigned a limited geographical area within which the vehicle can be operated with the actuator. Microprocessor  13  identifies the actuator selected from among actuators  20  present by transmitting its group number. All other actuators  20  present that have different group numbers no longer participate in the remainder of the communication process. 
     Device  10  then subjects selected actuator  20  to an assignment verification check. In the example, this is done using the known challenge-response method. Via its transceiver  11 , device  10  transmits an encrypted challenge signal which is destined for selected actuator  20  and is executed only by the latter (Step  112 ). At the same time, microprocessor  13  on the device side detects an expected response signal. This signal is calculated from the challenge signal according to a predetermined algorithm, using the cryptic key stored in memory  31  and manufacturer code  17  provided in memory  15 . This ensures the uniqueness of the response signal and thus the ability to distinguish between actuators within the group. Meanwhile, the challenge signal is received by transceiver  21  in actuator  20 , decoded in decoder  22  with the help of cryptic key  31 , and supplied to microprocessor  24 . The latter derives a response signal from the received challenge signal in the same manner as microprocessor  13  on the device side and sends it back to device  10  (Step  114 ). There the signal is received by transceiver  1 , decoded in decoder  12 , and supplied to microprocessor  13 . The latter compares it to the previously generated expected response signal (Step  116 ). If the two signals do not match, device  10  and actuator  20  do not belong to each other. Processor  13  then initiates a suitable follow-up action, for example it disables device  10  so that it cannot be used (Step  117 ). In addition, it can be useful to alert the user that an assignment was not made, for example using optical or acoustic indicators. 
     Further follow-up actions can also be provided, for example repetition of the assignment process, starting with Step  112  or Step  102 . If, as the result of the check and Step  116 , the response signal returned by actuator  20  does match the previously generated expected response signal, a confirmation that the assignment is correct is issued. It can be useful for this to take place in a form that can be perceived visually or acoustically by the user, and to cause device  10  to be enabled, for example (Step  118 ). 
     Mechanism  10 ,  20 ,  30  described above permits, through training, new, in particular factory-new actuators  20  to also be assigned to an existing device  10 . This type of new assignment is carried out as illustrated by the flowchart in FIG.  4 . The suffix added to each process step in the form of the letters B or G again reveals whether that process step takes place in device  10 (G) or in actuator  20 (B). The training of actuators  20  to be newly assigned initially takes place in the same manner as the assignment, illustrated in  FIG. 2 , of units already known to each other and begins by triggering an assignment communication process according to Step  100 . Actuators  20  located within the active range of device  10  are then detected according to Steps  102  to  108 . In Step  109 , however, teach mode is defined (Step  200 ). Switching between the assign and teach modes is suitably accomplished by the user with the aid of input device  17 . Microprocessor  13  then checks (Step  202 ) whether a specific actuator  20 , considered the main actuator, is present. The main actuator can be, for example, the actuator with group number  0  which returns a contact signal in first time window F 0  after receiving the scanning signal. If microprocessor  13  determines that main actuator  20  is not present, it cancels the teach mode. 
     If the check in Step  202  reveals that the main actuator is present, it is subjected to an assignment verification check (Step  203 ) according to Steps  102  to  118 . If the incorrect assignment was made, the teach mode is canceled (Step  201 ). If a correct assignment between the main actuator and the device is determined, microprocessor  13  checks, on the basis of directory  18 , whether there are any more available group numbers not yet assigned to an actuator and whether any further actuators  20  can be assigned to device  10  (Step  204 ). If not, it cancels the teach mode again (Step  201 ). If the answer is yes, microprocessor  13  transmits a null scanning signal (Step  205 ). The structure of the null scanning signal is identical to that of a scanning signal that is emitted during normal operation in Step  104  and is also not encrypted. The serial number, however, is replaced by a new serial number characteristic of brand-new actuators  20 . If binary serial numbers are used, they are composed, for example, of a simple sequence of zeros. Any brand-new actuators  20  located within the active range of radio link  30  receive the null scanning signal. Each of their microprocessors  24  then randomly selects a time window in which it sends a contact signal back to device  10  (Step  206 ). To do this, it links, for example, manufacturer code  27  provided in memory  25  to a random number generated by microprocessor  24 . Meanwhile, device  10  checks for receipt of contact signals following the transmission of the null scanning signal (Step  208 ). If microprocessor  13  determines that no contact signal was received, it cancels the teach mode (Step  201 ). However, if microprocessor  13  determines that a contact signal produced by a null scanning signal was received in a time window, it transmits a control signal (Step  210 ), which immediately switches any other existing actuators  20  to idle mode, including those which send a contact signal in a later time window. Microprocessor  13  then repeats Steps  205  to  210  with detected actuators  20  a specific number of times, i.e., k times, where k is an integer, in order to ensure that only one actuator  20  participates in the new assignment communication process even if multiple new actuators  20  to be assigned have responded in the same time window. When only one active actuator  20  to be taught remains within the range of radio link  30 , microprocessor  13  transmits serial number  16 , cryptic key code  31 , and a characteristic group number  26  to be assigned later on to actuator  20 . Actuator  20  transfers transmitted code information  16 ,  26 ,  31  to the spaces provided for them in memory  25 , which are still free at this point. After code information  16 ,  26 ,  31  has been successfully transmitted and stored, actuator  20  sends an acknowledgment signal to device  10 . This can be, for example, manufacturer number  27 . It is stored by microprocessor  13  on the device side and causes a disable command to be sent to actuator  20 . This command causes serial number  16  previously read to memory  26  and the cryptic code information stored in memory  31  to be read- and write-protected. Actuator  20  is then assigned to device  10 . In subsequent Step  220 , device  10  then sends a wake-up command, which is used to reactivate any additional actuators  20  that were placed in sleep mode. Device  10  can then be taught to respond to additional new actuators  20  to be assigned by repeating steps  202  and following. 
     The mechanism described above can be designed and modified in many different ways, at the same time retaining the basic idea of identifying actuators on the basis of the time at which they respond to a scanning signal. This applies, for example, to the structure of the device and actuators, to the layout and sequence of process steps, and possibly to the implementation of the access verification check or the form and structure of the code information exchanged via the radio link.