GB2280527A - Vehicle security system - Google Patents

Abstract

A vehicle security system including a displacement detector, preferably in the form of a vehicle locator, and an immobiliser. The system is armed by setting the immobiliser and if triggered by displacement of the vehicle by greater than a predetermined distance broadcasts an alarm signal which preferably identifies the vehicle and its location.

Description

VEHICLE SECURITY SYSTEM The present invention relates to vehicle security systems and particularly to one with which the location of a stolen vehicle can be detected.

Many security systems for cars are known but they suffer from various drawbacks. Audible alarms are frequently set off accidentally and because of this are often ignored. Vehicle immobilisers can often be by-passed by the thief and thereafter are ineffective.

The present invention therefore aims to provide an improved security system in which the number of false alarms is reduced and which can be of assistance in tracing a stolen vehicle.

The present invention provides a vehicle security system comprising: arming means for arming said system; displacement detecting means for detecting displacement of said vehicle; and alarm means for issuing an alarm signal when said system is armed and said displacement detecting means detects displacement of said vehicle by greater than a predetermined distance.

Preferably the system also includes an immobiliser in which case the arming means should arm the system when the immobiliser is set.

Preferably the system includes means for detecting a physical attack on the vehicle such as: a motion sensor to detect rocking of the vehicle or a person getting in; an ultrasonic sensor for detecting the opening of a door or the breaking of a window; a sensor for detecting an attempt to by-pass an immobiliser; a switch or switches for detecting the opening of a door, bonnet (hood) or boot (trunk) lid or any other suitable detector.

The means for detecting displacement of the vehicle may be an accelerometer based system or one responding to external reference signals (beacons).

The alarm signal may be a locally audible or visible signal (e.g. a siren or flashing light) or may be a radio signal. In the latter case the signal may contain information indicating at least one of: its location, its speed, the direction of travel, the cause of the alarm and the status of the vehicle.

The requirement for both the system to have been armed by setting an immobiliser and displacement of the vehicle before an alarm is issued reduces false alarms; e.g. when the vehicle is moved by its owner or when a motion sensor is set off by a passing vehicle or pedestrian leaning on the vehicle. The additional optional requirement for a physical attack on the vehicle can prevent false alarms when the vehicle is being carried by, for example, a ferry or train.

The predetermined distance that the vehicle must move may be set according to the sensitivity of the detector and possible causes of false alarms that are to be avoided.

The invention will be further described hereinafter with reference to the following description of exemplary embodiments and the accompanying description, in which: Fig 1 shows a car to which an embodiment of the invention is fitted; Fig 2 is a schematic diagram of a first embodiment of the invention; Fig 3 is a schematic diagram of a second embodiment of the invention, and Fig 4 is a schematic diagram of a third embodiment of the invention.

In the figures like parts are indicated by like reference numerals.

Fig 1 shows a car 1 to which an embodiment of the invention has been fitted. The only external visible sign of the security system is an external aerial 2 though this may be covert or an already existing aerial may be employed.

Fig 2 shows a basic vehicle security system which consists of a primary vehicle immobilisation system (immobiliser) 3a integrated with a vehicle location and tracking device (locator) 4. The immobiliser functions as a primary theft deterrent device, isolating up to three major electrical circuits within the vehicle. It also serves as an arming system for the vehicle locator, which under normal driving conditions remains completely dormant.

As shown in Fig 3 the security system may be connected to several different devices 3a - 3f for detecting a physical attack on the vehicle. In this case, an interface 5 may be provided between the sensors and locator.

The locator unit 4 is fitted with an integral motion sensor 4a which becomes active when the vehicle is immobilised. Any movement of the vehicle which triggers the motion sensor will cause the locator to "wake up" and begin a local transmission diagnosis. If the locator unit detects a certain number of grid reference co-ordinate changes within a short period of time, i.e. the vehicle is physically moving either under its own power or otherwise, then it begins its alarm transmission which is picked up at a monitoring bureau via the data network.

The alarm transmission may be made during a timeslot reserved for this type of system in an existing monitoring system or in random ones of said timeslots.

The internal diagnostic check means that false alarms are impossible as the system must receive varying positional data to justify an alarm transmission and therefore rocking or vibration of the vehicle will only cause the locator to wake, not transmit, an alarm signal.

The vehicle location and reporting system enables vehicle controllers to monitor, in real time, the position and status of all vehicles (mobiles) under their control during actual theft in progress situations.

Under such alarm conditions the locator unit computes the vehicle position from radio signals received from a network of 'navigation transmitting stations' for example the Datatrak (RTM) system. The position is then transmitted, approximately every 17 seconds, from the vehicle and received at a number of 'base stations' in the vicinity of the vehicle. From the base stations the data is sent by telephone lines to a 'data centre', where the incident is monitored and reacted to, or the incident data is then distributed to subscribers. At the subscriber's premises the vehicle data is displayed on a PC based computer system running display programme software.

The locator unit fitted to the vehicle continuously tracks the vehicle position, direction and speed - data is only transmitted to the base stations at predetermined intervals which are specified during installation. If transmission capacity is available the speed and direction of movement may be transmitted. If not, they may be calculated from successive positions of the vehicle. The reporting interval for alarm data may be every few seconds but for additional customer requested services it may be up to 28 minutes, and it can be different for individual vehicles.

One or more "Panic Buttons may be provided in the vehicle for operation by the driver if attacked or if the vehicle breaks down.

Although the system is completely integrated, it may be viewed as consisting of two linked sub-systems. The 'positioning subsystem', which consists of the network of low frequency (LF) navigation stations with their related infrastructure, and the 'reporting sub-system', which consists of the network of UHF base stations, the Regional Computer Centre and the individual user control centres.

The locator units fitted to the vehicles then act as an overlap between both sub-systems since they use the signals from the navigation transmitting station network to establish their position, and then transmit this position back to their control centres via the base stations and Regional Computer Centres.

Fig 4 shows a further embodiment of the invention in greater detail. In this embodiment an immobiliser 3a and a trembler 3b are used. The locator power supply 41 is turned on for a two hour period either by motion of the vehicle detected by trembler 3b or because the immobiliser 3a has not been operated. This will ensure that the locator is always powered in normal use and will remain powered up in the event that the vehicle is stolen when the immobiliser is not used. In this state it may respond to a 'where are you' command over the LF network. Power will be set on for 2 hours from either last movement detected or immobiliser activated (which ever is received last).

The internal displacement sensor (4a) is an output from the navigation section 42 of the locator. Care must be taken to prevent navigation aberrations, caused by distortions in the received signal, being detected as vehicle movement. The output of the navigation section 42 is fed to an AND gate 43 along with outputs from the trembler 3b and the immobiliser 3a (via an inverter 44). With this arrangement the trembler must detect movement for an alarm to be triggered, however, due to the unpredictable nature of such devices, the alarm should be enabled if the confidence of movement is very high.

An output from AND gate 43 sets bistable 45 which remains high for 5 minutes from after the output of AND gate 43 goes low. A receiver 47 detects a "where are you" command over the LF network and sets bistable 46 high for 1 hour. The outputs of bistables 45 and 46 are passed to OR gate 48 which enables transmitter 45 which generates the appropriate alarm message for broadcast with aerial 2.

With this arrangement, the unit broadcasts an alarm if the immobiliser is set (to immobilise the vehicle), the trembler detects motion of the vehicle and the displacement sensor detects displacement of the vehicle. If the immobiliser is turned off, i.e. normal driving position, no alarm is generated on movement of the vehicle but the unit is powered up so that it can respond to a "where are you" command. This enables the vehicle to be located should it be stolen when the driver had failed to set the immobiliser but prevents alarms while the vehicle is being driven normally.

The connection between location and immobiliser is arranged so that only a short between the two wires, not a short to earth or +12V, will disable the immobiliser.

Claims (13)

1. A vehicle security system comprising: arming means for arming said system; displacement detecting means for detecting displacement of said vehicle; and alarm means for issuing an alarm signal when said system is armed and said displacement detecting means detects displacement of said vehicle by greater than a predetermined distance.

2. A system according to claim 1 further comprising an immobiliser for immobilising said vehicle and wherein said arming means arms said system when said immobiliser is set to immobilise the vehicle.

3. A system according to claim 1 or 2 further comprising sensor means for detecting a physical attack on said vehicle and wherein said alarm means generates an alarm when said sensor means detects an attack, said system is armed and said displacement means detects displacement of said vehicle by greater than a predetermined distance.

4. A system according to claim 3 wherein said sensor means includes at least one trembler for detecting vibration or rocking of said vehicle.

5. A system according to claim 3 or 4 wherein said sensor means includes at least one ultrasonic detector in a compartment of said vehicle.

6. A system according to claim 3, 4 or 5 wherein said sensor means includes at least one door switch.

7. A system according to any one of the preceding claims further comprising broadcast means for broadcasting said alarm signal over a radio frequency.

8. A system according to any one of the preceding claims wherein said displacement detector means comprises locator means for determining the location of said vehicle.

9. A system according to claim 7 wherein said alarm signal includes information indicating the location of said vehicle.

10. A system according to any one of the preceding claims further comprising receiver means for receiving an external command and issuing said alarm signal or another signal in response thereto.

11. A system according to any one of the preceding claims wherein said alarm signal includes information identifying said vehicle.

12. A vehicle security system constructed and arranged to operate substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

13. A vehicle including a security system according any one of the preceding claims