GB2308708A - Vehicle anti-theft protection - Google Patents

Description

VEHICLE ANTI-THEFT PROTECTION The present invention relates to the protection of vehicles against theft.

Various systems have been proposed to immobilise a vehicle in order to prevent theft by interfering in some way with the engine management system so that the engine will not start unless a code is received. The code may be generated by a transponder incorporated in the ignition key as used in certain passive anti-theft system, or by a separate electronic key. The interference may take the form of preventing the ignition circuit or the engine fuelling from operating until the code is received. When such code detection is built into the engine management computer, it is extremely difficult for the vehicle to be driven away by the casual thief.

It is however more difficult to protect a vehicle against the more determined thief who is prepared to replace the engine management computer. Currently, such computers are capable of learning the access code when they are first installed and replacing the computer by a totally new one will automatically circumvent the security system and permit the thief to render the vehicle operational.

With a view to avoiding this problem, the present invention provides a method of protecting against theft of a vehicle having a computerised engine management system, the method comprising measuring and storing within the engine management computer a set of environment variables to enable the computer to detect a change of operating environment and preventing operation of the engine in the event that the measured environment variables do not match the environment variables previously stored in the computer.

The present invention aims to prevent an engine management computer from being transferred by unauthorised persons from vehicle to vehicle and to avoid a security system being bypassed by the installation of a brand new computer.

An environment variable may be any measurable parameter that is available within the vehicle and that may vary from one vehicle or driver to another. It is not essential for each individual signal to be distinctive because by measuring several individual variables one can build up a signature which becomes more and more distinctive as the number of variables is increased.

The environment variables may be characteristic of the engine, of the vehicle or of the driving style of the driver. Examples of engine related environment variables are ignition timing, running temperature, idling speed, oil pressure, variations between cylinders in timing and fuelling and so on. Examples of vehicle related environment variables are wiring harness configuration as sensed by resistance, capacitance and inductance measurement and frequencies at which the angine and bodyshell resonate to produce noise or vibration. Driver related environment variables may include throttle opening, acceleration rates, braking rates, cornering speeds, engine speed during gear changes and so on.

The invention relies on the use of a set of environment variables to establish a "signature" that is characteristic of the vehicle and/or its driver. Even if the individual signals have a wide tolerance there will only be a low probability of a signature match if a computer is transferred from one vehicle to another and no probability at all of a match when the computer is first installed with the environment variables missing from its memory.

Because of the wide tolerance in the individual signals, the security system will not be affected by normal changes occurring through wear and tear. The signatures can be reset by authorised persons during engine servicing or the computer may be programmed to permit the individual variables to be adapted gradually to accommodate minor changes.

In any security coded computer, whether is detects a key code or a signature indicative of its operating environment, it is important to ensure that only authorised persons can modify the data stored in the engine management computer. To this end, it is important that only the internal micro-processor of the computer should be capable of accessing the memory for reading and writing operations, thereby avoiding the possibility of direct copying of read only memories. The microprocessor is preferably security encoded so that it can only be accessed by a service computer operated by a skilled service engineer having the official access codes.

To prevent a thief from using the service computer, it is preferred to retain part of the security code required to permit the data stored in the vehicle engine management computer to be over-written by the service computer, on a central computer operated by the vehicle manufacturer. A service engineer would be then required to log on to the manufacturer's central computer and to identify himself and the vehicle before a unique security code is released to permit the engine management system to be reprogrammed. In this way, only an authorised dealer with access to a service computer and to the manufacturer's central computer will be able to install a new engine management system or to modify the security data in the engine management system after a major repair or transfer to a new driver.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic representation of an electronic engine controller, and Figure 2 shows an installation for permitting data to be written to the internal memory of an engine controller.

In Figure 1, an electronic engine controller (EEC) 10 comprises a microprocessor 12 connected to random access memory 14 and electrically erasable read only memory 16.

The microprocessor 12 is also connected to various circuits in the vehicle through an input and output interface (I/O) circuit 18.

Various sensors 20a, 20b, 20c such as a crankshaft position sensor, a throttle position sensor, a manifold vacuum sensor, etc. supply input signals to the EEC 10 to enable it to determine such parameters as the correct quantity of fuel to be injected into the engine, the spark timing and so on that are essential for correct operation of the engine. After the necessary processing of the input data, the EEC 10 sends output signals to an ignition circuit 22, a fuelling circuit 24 and a fuel pump 26 to control the operation of the engine. As so far described, the illustrated system is conventional and does not therefore require detailed explanation. The invention can in practice be applied to any vehicle fitted with an engine management computer.

It will clear that correct operation of the EEC is essential to the operation of the vehicle and that it therefore provides an excellent way of immobilising a vehicle to prevent it from being stolen.

To this end, it has already been proposed to store in the memory 16 a digital code that matches a code supplied by a passive anti-theft system integrated into the ignition lock. Such a passive system relies on a small circuit in the ignition key which, when interrogated by a circuit in the ignition lock, supplies a unique digital code to the EEC.

Until such time as the EEC receives this code, it is programmed not to operate. The vehicle cannot therefore be started, not even by so-called "hot wiring".

A problem that remains however is that new EEC's need to be able to be programmed to recognise the digital code supplied by the vehicle passive anti-theft system. Thus a new EEC may be programmed to store the first digital code to which it is connected. If therefore a would be thief replaces the EEC with a brand new one, then he can effectively bypass the vehicle security system.

The invention is intended to allow replacement of an engine management computer only by authorised personnel. To this end, the EEC is programmed to store in its internal memory 16 certain environment variables that vary from one vehicle to another or indeed from one driver to another. If the management computer determines that its operating environment has changed, then it is programmed to cease correct operation and to prevent the engine from being restarted.

The environment variables may be characteristic of the engine, of the vehicle or of the driving style of the driver. Examples of engine related environment variables are ignition timing, running temperature, idling speed, oil pressure, variations between cylinders in timing and fuelling and so on. Examples of vehicle related environment variables are wiring harness configuration as sensed by resistance, capacitance and inductance measurement. A further example of vehicle related environment variables are the frequencies at which the engine and bodyshell resonate to produce noise and vibration. There frequencies are detected in Figure 1 by the resonance detector 28 that is a form of spectrum analayser recording the noise and vibration levels at different engine and road speeds.Driver related environment variables may include throttle opening, acceleration rates, braking rates, cornering speeds, engine speed during gear changes and so on.

If a wide tolerance is allowed for any one match between a sensed variable and its stored value, then immobilisation will not occur accidentally in the interval between servicing but it is possible alternatively for the EEC to be programmed to adapt to a slow and gradual change in any environment variable. In the event of a serious mismatch, however, the engine will be immobilised until it is repaired by an authorised service centre.

The memory in which the environment variables are stored is preferably internal to the EEC module and inaccessible directly. Thus it is not possible to modify the contents of the memory without using the programs stored in the EEC. Only using a dedicated service computer capable of communicating with the internal microprocessor of the EEC module 10 will it be possible to instruct the microprocessor to store in the memory the prevailing values of the environment variables.

The fact that a computer with a dedicated program needs to be used to reprogram the EEC module is in itself fairly safe but as a further safeguard, it is preferred that the service computer 40 be connected, in the manner shown in Figure 2, by a modem 42 and a telephone line 44 to a central computer 44, operated by the vehicle manufacturer. Security coding can be built into the program in the service computer to prevent the service computer from being accessed by unauthorised persons and in this way the central computer can keep track of all newly fitted EEC modules so that if a car should ever be stolen, the identity of the service operator who reprogrammed the EEC would be known.

Claims (12)

1. A method of protecting a vehicle having a computerised engine management system against theft, the method comprising measuring and storing within the engine management computer a set of environment variables to enable the computer to detect a change of operating environment and preventing operation of the engine in the event that the measured environment variables do not match the environment variables previously stored in the computer.

2. A method as claimed in claim 1, wherein the environment variables are characteristic of the engine.

3. A method as claimed in claim 2, wherein the environment variables comprise at least one of the ignition timing, engine running temperature, idling speed, oil pressure, and variations between cylinders in timing and fuelling.

4. A method as claimed in claim 1, wherein the environment variables are characteristic of the vehicle.

5. A method as claimed in claimed in claims 4, wherein the environment variables include the wiring harness configuration as sensed by resistance, capacitance or inductance measurements.

6. A method as claimed in claim 4 or 5, wherein the environment variables include the values of resonance frequencies of the engine and bodyshell at which noise and vibration are accentuated.

7. A method as claimed in claim 1, wherein the environment variables are characteristic of the authorised driver of the vehicle.

8. A method as claimed in claimed in claims 7, wherein the environment variables include at least one of the throttle opening, acceleration rates, braking rates, cornering speeds and engine speed during gear changes.

9. A method as claimed in any preceding claim, wherein the stored values of the environment variables are adaptively modified during authorised use of the vehicle to take into account gradual changes in the variables.

10. A method as claimed in any preceding claim, in which the stored values of the environment variables may be modified by the use of a service computer.

11. A method as claimed in claim 10, in which the service computer must obtain a security code from a central computer before it may modify the stored values of the environment variables.

12. A method of protecting a vehicle against theft, substantially as herein described with reference to and as illustrated in the accompanying drawings.