WO1993015935A1

WO1993015935A1 - Motor vehicle anti-theft system

Info

Publication number: WO1993015935A1
Application number: PCT/GB1993/000225
Authority: WO
Inventors: Richard David Harwood
Original assignee: Fibre Optic Technologies Limited
Priority date: 1992-02-07
Filing date: 1993-02-03
Publication date: 1993-08-19
Also published as: AU3457893A

Abstract

In an anti-theft system for a motor vehicle having a battery supplying electrical power to enable the vehicle to operate, the battery has a built-in remotely-operable switch to interrupt or limit current flow between one of the battery terminals and the battery cells. The battery is of the conventional type comprising a casing (1) containing a plurality of electrical cells (2) and having external positive and negative terminals (3, 7). The battery cells (2) are connected to one of the terminals (3) directly and to the other terminal (7) through switching means (5) within the casing, the switching means (5) being arranged to close the circuit between the cells (2) and one of the terminals (7) in response to a control signal, a control means being provided outside the battery casing, and being operable to provide said control signal, for example as an infrared signal along an optical fibre cable.

Description

MOTOR VEHICLE ANTI-THEFT SYSTEM Field of the Invention

This invention relates to an anti-theft system for a motor vehicle, and to a battery for use in such a system. Background to the Invention

Anti-theft systems for vehicles conventionally fall into two categories: systems which generate an alarm when theft is attempted; and those that disable the vehicle, for example by adding a switch into the ignition circuit. While the location of the additional switch can be hidden, it is often possible for the thief to by-pass it once located. Summary of the Invention

In its broadest aspect, the invention provides an anti-theft system comprising a motor vehicle battery having a built-in remotely-operable switch to interrupt or limit current flow between one of the battery terminals and the battery cells.

A preferred embodiment of the invention provides an anti-theft system for a motor vehicle having a battery supplying electrical power to enable the vehicle to operate, the battery comprising a casing containing a plurality of electrical cells and having external positive and negative terminals, characterised in that the battery cells are connected to one of the terminals directly and to the other terminal through switching means within the casing, the switching means being arranged to close the circuit between the cells and said one terminal in response to a control signal, and in that a control means is provided outside the battery casing, the control means being operable to provide said control signal.

Preferably, the control means is located remotely from the battery and is connected thereto by a cable. The control means preferably sends a uniquely coded signal so that only the control means matching the battery can operate the switch. The cable may be an optical cable, the codeα signal being a modulated light signal. In this context "light" includes infra-red radiation.

Preferably, the control means is arranged to send coded signals only in response to the presence of a control token engaged with or inserted into the control means. The control token may be optically encoded, particularly where control signals are sent to the switching means in the battery by way of an optical cable. The optical encoding may take the form of appropriately aligned optical wave¬ guides, for example optical fibres, through the body of the token, so that only a token having optical waveguides which correctly align with those in the control means will permit the control means to operate.

In an alternative embodiment, the control token is an electronic circuit token, for example a so-called "smart card" . The token may be arranged to store an identifying code which can be read by the control means when the token is present thereon or therein. The code is sent to the switching means, where it is compared with a stored code. If the codes are the same, the switching means operates to close the circuit. Preferably, the switching means then generates a new code, for example by a random or pseudorandom number generator, which is stored in the switching means and transmitted to the control means to be stored in the token. The code is suitably a 7-digit number. In this way, the system code is changed each time the token is used, and thus has the advantage that all the tokens and switching means may initially be identical when manufactured, reducing manufacturing costs while affording a high level of security. In another embodiment of the invention, the control means is arranged to signal to the switching means only in response to receipt of a coded signal from a remote transmitter such as the key fob infra-red transmitter known for use in remotely-operated vehicle door-locking systems. The coding on the input signal from the control means may be in the form of a modulation of the signal by a pre-determined frequency, the switching means comprising a frequency discriminating circuit to provide an actuating signal to close a switch in response to the pre-determined frequency. In the case of an optical link between the control means and the switching means, the frequency dis¬ criminating circuit comprises a light sensitive element such as a photodiode to receive the control signal.

Preferably, a bypass line including current limiting means is provided around the switching means to permit the flow of a small amount of power to the terminal to operate devices in the motor vehicle which require a continuous supply of power, for example clocks and radio tuning memory. The bypass line may include a trip switch which opens the line if a current is drawn in excess of a pre-determined limit below that required to permit the motor vehicle to operate, thus preventing the vehicle from being started without the use of the battery.

The switching means may comprise an electro-mechanical relay, or one or more solid state switches, but preferably comprises a motor-operated mechanical switch where high switching currents are likely.

The system of the invention offers a high degree of security and is relatively straightforward to install either as original equipment in a motor vehicle or as a conversion by simple replacement of the battery and installation of the remotely situated control unit.

The invention also provides a battery having a remotely operable internal switch controlling current flow through one of the battery terminals .

Another aspect of the invention provides a security system, comprising a transmitter and a receiver, the transmitter being arranged to transmit a code string to the receiver, and the receiver being arranged to compare the received string with a code string stored therein and to provide an authorisation signal if the received string is identical to the stored string, characterised in that the transmitter is arranged to change the transmission frequency at least once during transmission of the code string and the receiver is arranged to change its operating frequency in response only if the stored code string includes a corresponding frequency change indication at the same position therein.

The receiver may be located within a vehicle battery, the authorisation signal causing a switch between one of the battery terminals and the battery cells to close. Brief Description of the Drawings

In the drawings, which illustrate preferred embodi¬ ments of the invention:

Figure 1 is a partially sectioned end elevation of a battery for use in a system according to one embodiment of the invention;

Figure 2 is a partially cut away perspective view of a control unit for use with the battery illustrated in Figure i;

Figure 3 is a circuit block diagram of an optical control unit in accordance with one embodiment of the in¬ vention;

Figure 4 is a block diagram of a switching unit of one embodiment of the invention;

Figure 5 is a block diagram of a control unit according to an alternative embodiment of the invention;

Figure 6 is a block diagram of the switching unit co-operable with the control unit of Figure 5;

Figure 7 is a diagrammatic perspective view of a system in accordance with another embodiment;

Figure 8 is a block diagram of yet another embodiment of the invention; and Figure 9 is a diagrammatic elevation of a motor-op¬ erated switch for use in the system of the invention. Detailed Description of the Illustrated Embodiments

Referring first to Figure 1, the battery is of the lead-acid type, having, in conventional manner, a sealed casing 1 containing a plurality of cells 2 connected electrically at one end of the casing to a negative terminal 3, and at the other end to a first conductive connector arm 4 extending from a switching unit 5 located within the free head space in the battery casing. A second conductive connector arm 6 extending from the switching unit 5 is in turn connected to the positive terminal 7 of the battery. The switching unit 5, whose components are described hereinafter in more detail with reference to Figure 4, is a sealed unit, for example being encapsulated in a resin or other material unaffected by the battery acid. A control lead 8 extends from the switching unit 5 through the casing 1 adjacent to its upper part, and is connected to a control unit, hereinafter described in more detail with reference to Figure 2. The lead 8 consists of a fibre optic cable, and two electrical conductors which provide electrical power for the control unit.

In response to a coded optical signal the switching unit makes the connection between the battery cells 2 and the positive terminal 7. In the absence of the signal, the connection will not be made, and the battery will not function. The switching device is preferably bypassed by a secondary conductor of lower capacity connected to a bypass circuit which is in turn connected to the terminal 7. The bypass circuit comprises a thermal cut-out to provide a very low current, suitable for operating an electronic clock or the memory circuits of the electronic tuner of a car radio, for example, but with a peak output of 0.5 amps for no more than 1.5 seconds, the circuit being tripped if this level is exceeded.

The control unit illustrated in Figure 2 is connected to the end of the lead 8 remote from the switching unit 5, for example on or near the vehicle dashboard. The control unit comprises a casing 20 having at its front end 21 a slot 22 for receiving a token (not shown) whose general shape and size is similar to a standard plastics credit card. The slot 22 leads into a compartment 23 dimensioned to receive the token and to hold it securely with a portion thereof extending through the slot 22, permitting its withdrawal. On the rear face 24 of the compartment 23 a microswitch 25 is provided to be actuated by the token when inserted into the slot 22. The microswitch causes the electronic circuitry located in a rear portion 26 of the casing to be activated. The rear face 24 also mounts a light source 27, suitably a light-emitting diode or laser diode, whose position corresponds to the position of the entry to an optical waveguide within the token. The token is constructed with an optical fibre accurately positioned within a plastics body so that one end of the optical fibre corresponds with the position of the light source 27, while the other end terminates along one edge of the token at a position corresponding to a location on the side wall 28 of the compartment 23 where a coupler 29 is located, the coupler 29 coupling the light signal into the optical fibre forming part of the lead 8.

It will be seen that, by varying the position of the coupler 29 and possibly also varying the position of the light source 27, and positioning the optical fibre within the token accordingly, a number of permutations of coding in the card itself can be achieved, so that only the correctly matching card will operate with the control unit permitting the necessary signal to be sent to the switching unit. Thus, only when the correct token is present in the slot 22 can the signal be sent to the battery to operate the switching unit closing the circuit between the cells and the positive terminal.

Referring now to Figure 3, the electrical circuit in the control unit as shown in Figure 2 comprises an oscillator 30 providing a pre-determined signal frequency which is then fed to a code generator 31 which modulates the signal with a pre-determined code. This code can be individually set during manufacture to any one of a plurality of different codes. The resulting signal is then used to control the output of the light-emitting diode or laser diode 27 which is then fed via the token 32 to the optical fibre forming part of the lead 8.

Figure 4 shows a block diagram of the circuit of the switching unit 5 of Figure 1. A phototranεistor 40 detects the light arriving in the optical fibre and outputs a signal to a bandpass filter (not shown) corresponding generally to the oscillator output. The filtered signal is amplified and then passed to a microprocessor 41 which detects the presence of the code generated in the code generator 31 (Figure 3). The control unit and the switching unit are manufactured as a matched pair, with the corresponding code being set in both. If the correct code is detected by the microprocessor 41, a control signal is sent to a servo motor 42 via a buffer 43, causing the motor to operate to close a switch between the battery cells and the positive terminal. The presence of the microprocessor in the battery permits other battery management functions to be incorpo¬ rated. For example, an impact sensor 44 may be used to detect a collision and to send a signal to the microprocessor 41 causing the switch to be opened, thus substantially reducing the risk of the electrical system in the vehicle causing a fire after a collision. A temperature sensor 45 may also be incorporated to protect the battery from the effects of overcharging causing heating of the battery and damage to the plates. An indication of an excessive tem¬ perature in the battery may be used to disconnect the battery, or it may simply be used to give an audible warning, for example via an external sounder 46, a visible warning, or both. The microprocessor may also be provided with a memory to store a record of temperature, the device being provided with a communication port permitting the data stored in the memory to be accessed by an external computer temporarily connected thereto. It would thus be possible to detect when a failed battery had been subjected to overheating as a result of excessive charging, possibly invalidating the manufacturer's warranty. The additional coding imposed by the code generator

31 and detected by the microprocessor 41 ensures that simple substitution of one control unit for another will not permit the switching unit to be operated; only a matching pair of units will function together. Figure 5 shows an alternative arrangement of the control unit in which, instead of an optical key card as described with reference to Figure 2, an electronic circuit card, for example a so-called "smart card", is used to control the basic oscillator frequency. The smart card 50 is individually set to control the oscillator 51 to output a selected frequency which is then passed to a coded bit stream generator 52 whose output passes via a conventional cable to the switching unit within the battery. The switching unit is illustrated by Figure 6 and comprises a decoder 60 set to detect the required frequency and to extract the code from the received signal to provide an output to an amplifier 61 which in turn operates a relay 62, or solid state switching devices, performing the switching function. Referring now to Figure 7, yet another alternative arrangement of the control unit is shown, which consists of a receiver unit 70, mountable for example via an adhesive pad on a vehicle dashboard and connected to the battery as hereinbefore described, preferably by means of an optical fibre cable 71. The receiver unit comprises an infra-red sensor 72 which can receive a coded infra-red signal from a sender unit 73, suitably in the form of a key fob and having a thumb-operable switch 74 by which it may be activated. The code transmitted by the sender unit 73 is unique to that unit and to its associated battery switching unit, whereby the receiver unit 70 relays the received code to the battery, where it is matched with a stored code as hereinbefore described. Figure 8 is a block diagram for yet another system.

An electronic circuit token or "smart card" is used to store a code, for example a 7 to 10 digit number, and to transmit this code to a card reader 80 comprising a card interface 81, a central processing unit 82, an amplifier, filter and modulator/demodulator stage 83 and an optical transmit¬ ter/receiver stage 84 connected to the optical fibre 85 which is in turn connected to the battery switching unit. The switching unit similarly comprises an optical receiv¬ er/transmitter stage 86, a modulator/demodulator, filter and amplifier stage 87, and central processor 88, which then controls switching stage 88. In use, the card is inserted into, or simply placed on, the reader 80, depending on the card type. This activates the central processor 82 and transmits to it the code, which is passed via modulator 83, optical transmitter 84 and optical fibre 85 to the battery switching unit where, after appropriate demodulation, filtering and ampli ication, the code is compared in the central processor 88 with a previously stored code. If the codes are the same, the switching unit is caused to operate to enable the battery to supply full power. At the same time, the processor 88 generates, by means of a random or at least pseudorandom number generation process, a new code which is stored in the processor memory (not shown separately) in place of the previous code, and also transmitted back to the reader unit and thence to the card, where it is also stored in place of the previous code. Thus, on every valid insertion of the card into the reader unit, a new random code is generated, increasing security and permitting all such systems to be identical in manu¬ facture. Figure 9 shows a possible configuration of servo driven switch to be used as the switching element within the battery. It comprises a servo motor 90 driving a worm gear 91 engaging a pinion gear 92 mounted on a shaft 93, the lower half of which is screw-threaded and carries a fruεto-conical electrically-conductive plug 94, which is prevented from rotation about the shaft by a longitudinal sliding guide (not shown). A first switch terminal 95 is connected to the external positive terminal 7 of the battery. as described hereinbefore with reference to Figure 1, and carries at its lower part a curved tapering contact 96 conforming with the external shape of the plug. A second switch terminal 97 is connected to the battery cells, again as described with reference to Figure 1, and carries a similar, opposed, tapering contact 98 spaced from the first. Rotation of the servo motor 90 drives the plug downwardly between and against the two contacts to close the circuit. Switching off of power to the motor may be controlled by limit switches, or by detecting the current increase re¬ sulting from stalling of the motor. Opening of the battery switch is achieved in the reverse way to lift the plug away from the contacts 96 and 98.

An alternative signal coding system according to an aspect of the invention provides a higher level of security, and is applicable to the system of the invention, and to other systems where a security code is sent between a transmitter and receiver. In an example of the coding system, the code consists of a serial digital stream co - prising 256 bits. Written into this serial stream are commands that instruct the transmitter and receiver microprocessors to modulate their transmission and reception frequencies respectively, to give a frequency modulated digital data stream. In this context, frequency is used in the sense that the bit stream is punctuated by clock code pulses that have the effect of either increasing or decreasing the rate of bit transfer. Each clock code pulse will be followedor precededby avalidationbit and a synchronisation bit. In this manner, the receiver may pick up the data stream at any point, synchronise itself, validate, decode and act on the instruction. The complexity of this bit plus frequency modulation system permits unique codes in excess of 1.2 x 10²⁴, far exceeding that of other coding systems suitable for such applications.

In use, for example, when the transmitter is activated, an EPROM containing the serial data is instructed to output the data stream to the microprocessor, and embedded commands within the data stream instruct the microprocessor to transmit the data stream at specific different frequencies for different sections of the data. The receiving micro¬ processor looks for the serial bit stream, and by comparing with a valid serial bit record contained in its non-volatile memory it determines which frequency it will accept for any part of the transmission.

For example, the microprocessors may be capable of running at two clock speeds, namely 2MHz and 4MHz. The transmission may thus take the form: DATA VALIDATION BITS SYNC BITS CHANGE

FREQUENCY COMMAND (to 2MHz) DATA VALIDATION BITS SYNC BITS CHANGE FREQUENCY COMMAND (to 4MHz)

DATA VALIDATION BITS SYNC BITS CHANGE FREQUENCY

COMMAND (to 2MHZ) DATA ETC...ETC The number of frequency changes, the length of data stream, and the transmission and reception frequencies used will vary according to the particular application of secure coded transmission. The use of such an approach reduces the likelihood of the code being broken by random trial and error, since it will be very much more difficult for anyone attempting to replicate the code and gain unauthorised access also to reproduce the correct frequency changes. If the code were copied and retransmitted, although the code (serial bit stream) may be correct, the frequencies are not, and the remote receiver could not pick it up because, at several points throughout the bit stream, it has been told to change its processor speed, and this effectively causes an in- compatible baud rate, causing the receiver to reject the code as incomplete.

Claims

1. An anti-theft system for a motor vehicle having a battery supplying electrical power to enable the vehicle to operate, the battery comprising a built-in remo- tely-operable switch to interrupt or limit current flow between one of the battery terminals and the battery cells.

2. An anti-theft system according to Claim 1, the battery comprising a casing containing a plurality of electrical cells and having external positive and" egative terminals, characterised in that the battery cells are connected to one of the terminals directly and to the other terminal through switching means within the casing, the switching means being arranged to close the circuit between the cells and said one terminal in response to a control 5 signal, and in that a control means is provided outside the battery casing, the control means being operable to provide said control signal.

3. An anti-theft systemaccording to Claim 2, wherein the control means is located remotely from the battery and o is connected thereto by a cable.

4. An anti-theft system according to Claim 3, wherein the cable is an optical cable.

5. An anti-theft system according to Claim 2, 3 or 4, wherein the control means sends a uniquely coded signal 5 whereby only the control means matching the battery can operate the switch.

6. An anti-theft system according to Claim 5, wherein the control means is arranged to send coded signals only in response to the presence of a control token engaged with or inserted into the control means.

7. An anti-theft system according to Claim 6, wherein the control token is optically encoded.

8. An anti-theft system according to Claim 7, wherein the optical encoding takes the form of at least one ap¬ propriately aligned optical waveguide through the body of ₀ the token, whereby only a token having an optical waveguide which correctly aligns with that in the control means will permit the control means to operate.

9. An anti-theft system according to Claim 8, wherein the or each optical waveguide is an optical fibre. 5

10. An anti-theft system according to Claim 6, wherein the control token is an electronic circuit token.

11. An anti-theft system according to Claim 10, wherein the token is arranged to store an identifying code which can be read by the control means when the token is

„₀ present thereon or therein.

12. An anti-theft system according to Claim 11, wherein the control means is arranged to send the code to the switching means, which is arranged to compare said code with a stored code, and to operate to close the circuit if

2 the codes are the same.

13. An anti-theft system according to Claim 12, wherein the switching means is arranged to generate a new code which is stored in the switching means and transmitted to the control means to be stored in the token.

14. An anti-theft system according to Claim 13, wherein the new code is generated by a random or pseudorandom number generator.

15. An anti-theft system according to Claim 5, wherein the control means is arranged to signal to the switching means only in response to receipt of a coded signal from a remote transmitter.

16. An anti-theft system according to Claim 15, wherein the remote transmitter is a key fob infra-red transmitter of the type known for use in remotely-operated vehicle door-locking systems.

17. An anti-theft system according to any preceding claim, wherein a bypass line including current limiting means is provided around the switching means to permit the flow of a small amount of power to the terminal to operate devices in the motor vehicle which require a continuous supply of power.

18. An anti-theft system according to Claim 17, wherein the bypass line includes a trip switch which opens the line if a current is drawn in excess of a pre-determined limit below that required to permit the motor vehicle to operate, thus preventing the vehicle from being started without the use of the battery.

19. A security system, comprising a transmitter and a receiver, the transmitter being arranged to transmit a code string to the receiver, and the receiver being arranged to compare the received string with a code string stored therein and to provide an authorisation signal if the received string is identical to the stored string, characterised in that the transmitter is arranged to change the transmission frequency at least once during transmission of the code string and the receiver is arranged to change its operating frequency in response only if the stored code string includes a corresponding frequency change indication at the same position therein.

20. A security system according to claim 19, wherein the receiver is located within a vehicle battery and the authorisation signal causes a switch between one of the battery terminals and the battery cells to close.

AMENDED CLAIMS

[received by the International Bureau on 22 July 1993 (22.07.93); original claims 1-4 replaced by amended claim 1; claims 5,6-18,19 and 20 replaced by amended claims 2,3-15,17 and 18; new claim 16 added (4 pages)]

1. An anti-theft system for a motor vehicle having a battery supplying electrical power to enable the vehicle to operate, the battery comprising a casing containing a plurality of electrical cells and having external positive and negative terminals, the battery cells being connected to one of the terminals directly and to the other terminal through switching means within the casing, the switching means being arranged to close the circuit between the cells and said one terminal in response to a control signal, and a control means being provided outside the battery casing, the control means being operable to provide said control signal, characterised in that the control signal is conveyed to the switching means the battery casing through an optical cable.

2. An anti-theft system according to Claim 1, wherein the control means sends a uniquely coded signal whereby only a control means matching the battery can operate the switch.

3. An anti-theft system according to Claim 2, wherein the control means is arranged to send coded signals only in response to the presence of a control token engaged with or inserted into the control means.

4. An anti-theft system according to Claim 3, wherein the control token is optically encoded.

5. An anti-theft system according to Claim 4, wherein the optical encoding takes the form of at least one appropriately aligned optical waveguide through the body of the token, whereby only a token having an optical waveguide which correctly aligns with that in the control means will permit the control means to operate.

6. An anti-theft system according to Claim 5, wherein the or each optical waveguide is an optical fibre.

7. An anti-theft system according to Claim 3, wherein the control token is an electronic circuit token.

8. An anti-theft system according to Claim 7, wherein the token is arranged to store an identifying code which can be read by the control means when the token is present thereon or therein.

9. An anti-theft system according to Claim 8, wherein the control means is arranged to send the code to the switching means, which is arranged to compare said code with a stored code, and to operate to close the circuit if the codes are the same.

10. An anti-theft system according to Claim 9, wherein the switching means is arranged to generate a new code which is stored in the switching means and transmitted to the control means to be stored in the token.

11. An anti-theft system according to Claim 10, wherein the new code is generated by a random or pseudorandom number generator.

12. An anti-theft system according to Claim 2, wherein the control means is arranged to signal to the switching means only in response to receipt of a coded signal from a remote transmitter. 13. An anti-theft system according to Claim 12, wherein the remote transmitter is a key fob infra-red transmitter of the type known for use in remotely-operated vehicle door-locking systems.

14. An anti-theft system according to any preceding claim, wherein a bypass line including current limiting means is provided around the switching means to permit the flow of a small amount of power to the terminal to operate devices in the motor vehicle which require a continuous supply of power.

15. An anti-theft system according to Claim 14, wherein the bypass line includes a trip switch which opens the line if a current is drawn in excess of a pre-determined limit below that required to permit the motor vehicle to operate, thus preventing the vehicle from being started without the use of the battery.

16. An anti-theft system according to Claim 2, comprising a receiver unit coupled to the battery by the optical cable, and a sender unit for sending a coded light control signal to be relayed by the receiver unit to the battery via the cable.

17. A security system, comprising a transmitter and a receiver, the transmitter being arranged to transmit a code string to the receiver, and the receiver being arranged to compare the received string with a code string stored therein and toprovide an authorisation signal if the received string is identical to the stored string, characterised in that the transmitter is arranged to change the transmission frequency at least once during transmission of the code string and the receiver is arranged to change its operating frequency in response only if the stored code string includes a corresponding frequency change indication at the same position therein.

18. A security system according to claim 17, wherein the receiver is located within a vehicle battery and the authorisation signal causes a switch between one of the battery terminals and the battery cells to close.