FR2795121A1 - CONTROL DEVICE, IN PARTICULAR VEHICLE ACCESS CONTROL DEVICE OR IMMOBILIZER DEVICE AND METHOD FOR SUCH A DEVICE - Google Patents

Abstract

As a safety measure to protect against unauthorized remote interrogation, a transponder (1) is equipped with a motion detector (2) and, upon receipt of an interrogation code signal, it does not returns its response code signal only if it has been tossed within a certain time interval preceding the clearance check.

Description

The invention relates to a control device, preferably a

  motor vehicle control device comprising a control device mounted on the motor vehicle, in particular for the access control and / or immobilizer function, which, before the execution of the function to be controlled, performs an authorization check with an identity transmitter (hereinafter called transponder) which is delivered to the authorized user. In general, during the verification of the authorization, an interrogation code signal is sent to the transponder, a signal to which the latter responds with a response code signal, the accuracy of which is verified by the control unit placed at on board the vehicle. The range of transmission signals is usually relatively small, so that data communication can only take place in the immediate vicinity of the motor vehicle. However, theoretically, an unauthorized remote interrogation (also called full duplex attack) can be considered possible, in which the signal

  interrogation code is fraudulently received and analyzed.

  Document DE 44 09 167 Cl discloses a control device of this kind, in particular a motor vehicle control device comprising a control device, in particular a control device for controlling access and / or anti blocking. -starting, and a portable transponder serving as an identity transmitter, which presents a control assembly and communicates wirelessly with the control device intended for the verification of the authorization, by emitting an identity code, in which , the portable transponder has a distance detection device and in which the communication is immediately interrupted if the distance between

  the control unit and the transponder is too large.

  Document DE 196 04 206 A1 discloses a similar motor vehicle control device in which a user enters the identity code (PIN)

  using a transponder keyboard.

  Document GB 2 279 479 A discloses an alarm device incorporated in a fixed position for a vehicle, in which a compass is used as

displacement sensor.

  Document DE 94 14 476 Ul discloses a device for monitoring a stopped vehicle which is placed in the stopped vehicle and comprises, between

  others, a tilt sensor.

  The object of the invention is to further reduce the

  possibility of such unauthorized interrogation.

  According to the invention, this problem is solved by the fact that the transponder is equipped with a motion detector and by the fact that the control unit verifies, during a verification of authorization, whether the transponder has been stirred within the limits of a determined time interval before the verification of the authorization, and that it releases the emission of the identity code only when

this criterion is satisfied.

  Furthermore, with the invention, a method is created for controlling the progress of the authorization verification or for carrying out an authorization verification between a control device and a portable transponder, which communicates without wire with the control unit, characterized in that during the execution of an authorization check, it is additionally checked whether the transponder has been moved or has not been moved during an interval of predetermined time preceding the execution of the verification of the authorization, and the transponder then transmits its identity code only if, during the predetermined time interval, it has been detected a movement of the

  transponder that exceeds a certain threshold.

  In the invention, during the verification of the authorization, it is verified, as an additional criterion, whether the transponder has been moved within the limits of a short time interval, of 10 to 30 seconds for example, before the verification of empowerment. The invention takes advantage of the fact that in general an authorized user has walked to the vehicle immediately before the execution of the verification of authorization, or sat immediately before in the seat of the vehicle, so that user-carried transponder has been exposed to large movements, accelerations and jolts. If, on the contrary, an unauthorized remote interrogation was attempted, it is very likely that the transponder was not moved immediately before the authorization interrogation because, for example, the authorized user sat for a long time on an office chair or put the bag containing the transponder or hung the corresponding piece of clothing, for example his jacket. It is only when this additional criterion of displacement of the transponder immediately before is satisfied that the control unit releases the emission of the correct response code signal. This additional safety criterion can be achieved in a simple way since only the transponder has to be equipped with an additional motion detector and a rhythm generator or another chronology circuit. No intervention in the components of the control device located on board the vehicle is necessary. In this way, even the already existing devices can be very simply upgraded by replacing the transponder. The motion detector can be produced in the form of a mechanical displacement switch or also in the form of a mechanical oscillation element, and it acts on a circuit with an output signal which varies as a function of time, in a continuous mode, stepwise or abruptly. The chronology circuit can have various configurations and be constituted, for example, by an RC element with a large discharge time constant or by

a time counter.

  The invention can be applied in control devices of all kinds, that is to say also for the control of functions other than an access control and / or a immobilizer, for example for verification of the authorization to use a

  safe, cash machine or the like.

  According to other advantageous features of the invention: - a rhythm generator circuit produces an output signal varying as a function of time and is used to determine the flow of the predetermined time interval; - the motion detector is a mechanical movement switch which is inserted in the charging circuit of a capacitor provided with a discharge circuit, the output voltage of the capacitor representing a measure of the time that has elapsed from the last movement of the transponder which led to the closing of the mechanical movement switch; - the motion detector is a mechanical resonator comprising a solid body suspended elastically which continues to oscillate in a damped manner after being excited by a movement; - a counter counts a cycle signal and the potential of its reset input is controlled by the motion detector so that after the predetermined time interval has elapsed without receiving a signal at the input of reset, the counter has counted to a determined counting state and applies a corresponding announcement signal to the control unit; - the counter is implemented in the form of

  software and is part of the control package.

  The invention is described in more detail about

  of exemplary embodiments and with reference to the drawings.

  Figure 1 shows a transponder for a control device, Figure 2 shows an embodiment of a circuit used for the detection of a movement and for the allocation of a time, Figure 3 shows an embodiment modification of a motion detector comprising a connected control circuit and FIG. 4 shows an embodiment

including a cycle counter.

  In Figure 1, there is shown schematically the construction of an identity transmitter constituted by a transponder 1, which is here produced in the form of a smart card but which can also have any other configuration, by example the shape of a key. The transponder 1 contains a motion detector 2 and a chronology circuit 3 connected to this detector, and which is in turn connected to a control or analysis assembly or circuit 4 (for example a microprocessor or a microcontroller). The control and analysis circuit 4 is equipped with a transmitting antenna 5 intended to send signals to a control device, not shown, which is used to control, for example, the access control device or the communication device. immobilizer blocking of a motor vehicle, and of a reception circuit 6 intended to receive interrogation code signals arriving from the control apparatus. The components present on the vehicle may have a known construction and be constructed, for example, so that, when a door handle or an engine starter button is actuated, an interrogation signal code either transmitted by the control device, via its transmit antenna, signal that the transponder 1 receives via its receive circuit 6 and applies to the control and analysis circuit 4. The circuit 4 checks whether the interrogation code signal is intended for it and, when this is the case, it sends back to the control unit, via the transmitting antenna 5, a response code signal which is checked for correctness in the control unit, for example by comparison with an expected set code signal. When the response code signal received is correct, the control unit controls the corresponding function, by the fact that, for example,

it unlocks the doors.

  The motion detector 2 can be constituted for example, by an acceleration detector comprising a mechanical displacement element, for example constructed on the basis of a semiconductor or in another way, it responds to vibrations, vibrations and accelerations generated during movements of the person carrying the transponder, and it produces an analog output signal or an output signal that jumps between two or more levels depending on the current magnitude of the acceleration. Since the motion detector here is not primarily intended for the absolute measurement of the magnitude of the movement or the acceleration, but on the contrary it only has to distinguish between a state of rest and significant movements, it suffices a detector having a simple construction which can only distinguish between the two states "acceleration below a certain threshold" and "acceleration above the threshold" and which produces, by

  for example, a digital signal of level "zero" or "one".

  Since the wearer's walking movements are usually linked to accelerations in the three directions of space coordinates, it suffices to use an acceleration detector which is sensitive only in one direction. However, of course, one can also use acceleration sensors which are sensitive in two or in three directions of

space coordinates.

  The chronology circuit 3 is attacked by the motion detector 2, or even powered by an inversion of the output signal level of the motion detector 2, each time the latter detects a

  displacement that is above the predetermined threshold.

  The timing circuit 3 is set to a fixed time interval of 5 to 30 seconds, for example, preferably 5 to 10 seconds and, during this period, it produces, each time that the motion detector 2 has detected a movement , an output signal which is applied to the control and analysis circuit 4, for example, a signal having a high logic level. The control and analysis circuit 4 therefore receives, in the presence of a high level of the output signal from the chronology circuit 3, the information consisting in the fact that the last movement sensed by the movement detector 2 is less recent than an instant in the predetermined time interval. In this case, the control and analysis circuit 4 responds to an interrogation code signal

  received by producing a response code signal 5.

  Otherwise, that is to say in the case where the displacement of the transponder 1 dates from longer than an instant situated in the predetermined time interval and the output signal of the chronology circuit 3 has therefore fallen, the control and analysis circuit 4 suppresses the production of the response code signal, even if it has received a correct interrogation code signal, so that the function to be controlled by the

  command placed on board the vehicle is not executed.

  In FIGS. 2 to 4, various more detailed embodiments of the movement detector 2 and of the chronology circuit 3 have been shown. FIG. 2 shows a circuit in which the movement detector is constituted by a mechanical movement switch 7, 7 'which, when a certain acceleration value is exceeded, pushes the switch 7 back to the closed position. The component 7 ′ can be a mass which, due to its inertia, cannot rapidly follow the movements and, consequently, pushes the switch 7 back into the closed position. The chronology circuit comprises a capacitor 8, one plate of which is set to ground potential and the other connection of which is connected to the supply voltage potential Vs when the switch 7 is closed. In parallel with the capacitor 8 is connected a discharge resistance 9 of a high ohmic value through which the capacitor 8 which charges when the switch 7 is opened discharges again with a large time constant. The voltage of the capacitor is applied to an input of a voltage comparator 10, the other comparison input of which is supplied with a reference potential Vref. The output of the voltage comparator 10 is connected to an input of the control circuit 4. During the movements of the transponder, the capacitor 8 is charged by the supply voltage with a low time constant through the switch 7 which closes repetitively, while in the absence of movements when, as a result, the switch 7 remains open for a long time, it discharges according to an exponential law. The discharge time constant and the comparison voltage Vref are adjusted so that the voltage of the capacitor 8 drops to the comparison voltage Vref when the predetermined time interval has elapsed, so that in this case , the output signal of the voltage comparator 10 is inverted and that, under this effect, the passage of the predetermined time interval without

  movement is signaled to the control circuit 4.

  In another embodiment, a low-damping mechanical resonator which continues to oscillate for some time after the onset of movement is used as the motion detection detector. The amplitude of the oscillation is then the basis of the decision. In Figure 3 there is shown schematically an embodiment of this type. The acceleration detector 11 comprises a housing 12 in the internal cavity of which a solid body 13 is stretched symmetrically between two springs 14 so that after excitations generated by an acceleration, it continues to oscillate relatively long with a decreasing amplitude. Against an interior wall of the housing, is disposed, opposite the rest position of the solid body 13, a switch 15, for example a microswitch which, if the solid body oscillates with an amplitude of oscillation greater than one certain value, is actuated periodically by the solid body 13. The control circuit 14 periodically interrogates the switching state of the switch 15 and it detects, on the basis of its periodic actuation, the presence of oscillations of the solid body 13 , i.e. the fact that the motion detector 11 has been exposed to sufficiently strong accelerations for less time than the predetermined time interval. If, on the contrary, the control circuit 4 finds that the switch 15 is not (no longer) actuated, this represents an indication of the fact that the oscillations are already damped, that is to say that there was a long period of no transponder movement, with the consequence that the interrogation code signals arriving at the

  orders no longer receive a response.

  FIG. 4 shows an embodiment comprising a rhythm generator constituted by a counter 16 which counts a synchronization signal which occurs with a fixed frequency and which, when a counting state corresponding to a determined duration has been reached, transmits an output signal to the control circuit 4. The counter reset input is connected to a high potential Vs by means of the motion detector constituted in the form of a motion switch or mechanical acceleration switch , so that the counter 16 is reset to zero each time the motion detector responds and therefore starts counting again. It is only when the motion detector has not been moved at least for the predetermined period and that, therefore, no reset pulse has been applied to the reset input, that the counter 16 counts in the ascending direction until a predetermined counting state and then durably transmits an output signal to the control circuit 4. As soon as, thereafter, new movements are detected, the counter 16 is reset and thus signals to the control circuit that the last movement was shorter than the predetermined time interval and that the incoming interrogation code signals can therefore receive a response consisting of the response code signal. The counter 16 can be constituted by a counter implemented in the form of software and it can therefore be integrated in the form of a part of the control circuit 4, which guarantees a very compact construction,

  saves current and is reliable in operation.

Claims (7)

  1. Control device, in particular motor vehicle control device comprising a control device, in particular an access control and / or immobilizer control device, and a portable transponder (1) serving as a transmitter identity, which has a control assembly (4) and communicates wirelessly with the control device intended for the verification of authorization, by issuing an identity code, characterized in that the transponder (1) is equipped with a motion detector (2, 7, 7 ', 11.17) and in that the control unit (4) checks, during an authorization check, whether the transponder has been moved in the limits of a time interval determined before the verification of the authorization, and that it does not release the emission of the identity code until this criterion is met.   2. Control device according to claim 1, characterized by a rhythm generator circuit (3; 8, 9, 10; 16) which produces an output signal varying as a function of time and which serves to determine the flow of   the predetermined time interval.   3. Control device according to claim 1 or 2, characterized in that the movement detector is a mechanical movement switch (7, 7 ') which is interposed in the charging circuit of a capacitor (8) provided with a discharge circuit (9), the output voltage of the capacitor (8) representing a measure of the time that has elapsed from the last movement of the transponder (1) which has led to a closure of   the mechanical movement switch (7, 7 ').   4. Control device according to claim 1 or 2, characterized in that the motion detector (11) is a mechanical resonator comprising a solid body (13) elastically suspended which continues to oscillate from   cushioned after being excited by movement.   5. Control device according to claim 1 or 2, characterized by a counter (16) which counts a cycle signal and whose potential of the reset input is controlled by the motion detector (17) so that after the predetermined time has elapsed without receiving a signal at the reset input, the counter has counted to a determined counting state and applies to the control assembly   (4) a corresponding announcement signal.   6. Control device according to claim 5, characterized in that the counter is implemented in the form of software and is part of the control assembly (4). 7. Method for carrying out an authorization check between a control device and a portable transponder (1) which communicates wirelessly with the control device, characterized in that during the execution of an authorization check, it is additionally checked whether the transponder (1) has been moved or has not been moved during a predetermined period of time which precedes the execution of the authorization check, and the transponder then transmits its identity code only if, during the predetermined time interval, it has been detected a movement of the   transponder that exceeds a certain threshold.