GB2490725A

GB2490725A - Sensor arrangement for a vehicle security system

Info

Publication number: GB2490725A
Application number: GB201107986A
Authority: GB
Inventors: Martin Banks; Neil Savage
Original assignee: Nissan Motor Manufacturing UK Ltd
Current assignee: Nissan Motor Manufacturing UK Ltd
Priority date: 2011-05-13
Filing date: 2011-05-13
Publication date: 2012-11-14
Also published as: GB201107986D0

Abstract

A sensor arrangement 10 is provided for a vehicle security / alarm system, comprising: a sensor controller 13; a volumetric intrusion sensor 14; an accelerometer 15; and a mounting (310, Fig. 4), wherein the sensor controller is arranged to generate an output in dependence on a comparison between the output from the volumetric intrusion sensor and the output from the accelerometer. The mounting may be arranged to secure both the volumetric intrusion sensor and the accelerometer together to a vehicle such that the accelerometer measures movement directly adjacent the volumetric intrusion sensor. The accelerometer is used to detect and to cancel out false alarm signals from the volumetric intrusion sensor, with the latter possibly comprising one or more ultrasonic transducers. The sensor arrangement may be mounted in an interior light unit (350, Fig. 4). A method of using such a sensor arrangement is also described.

Description

SENSOR ARRANGEMENT

Field of the invention

The present invention relates to a sensor arrangement and particularly, but not exclusively, to an improved sensor arrangement for a vehicle security system such as a car alarm. Aspects of the invention relate to a sensor arrangement, to an interior light assembly, to a vehicle security system, to a method for securing a vehicle, and to a vehicle.

Background of the invention

Vehicle security systems are becoming increasingly sophisticated in order to secure against criminals seeking to steal vehicles or their contents. One technology that has become almost standard equipment for vehicles sold in Europe is the car alarm; typically comprising a sensor for detecting unauthorised entry into the passenger and! or luggage compartment, and a siren for emitting an audible alarm.

Many such car alarms include so-called volumetric intrusion sensors (VIS), typically located within an enclosed volume to be monitored, such as an occupant compartment or a luggage area. Volumetric intrusion sensors often employ ultrasonic transducer technology in which ultrasonic frequency pulses are emitted by a transmitter, reflected back from surfaces defining the interior of the enclosed space and received by a receiver. Once activated, the sensor continues to emit ultrasonic frequency pulses into the compartment and looks for any change in the pattern of pulses reflected back to the transducer. If the occupant compartment or luggage area remains closed there will be no change in the pattern of pulses reflected back to the transducer and thus the siren of the vehicle alarm will not be activated. However, if certain characteristics of the compartment change, for example if a door is opened or if a window is smashed, the resulting change in the pattern of pulses reflected back to the transducer will trigger the vehicle alarm to activate the siren.

A known limitation of these volumetric intrusion sensors is that they can be confused by pressure changes caused by events that are entirely innocent in nature, giving rise to false alarms. Vibration caused by nearby movement of heavy vehicles such as trucks or trains can cause parts within the cabin to vibrate, causing a pressure change in the vehicle sufficient to trigger a false alarm. It has also been known for thunder storms and even low flying jets to trigger false alarms.

Such susceptibility to false alarms is undesirable for several reasons: it causes an unnecessary disturbance; it leads to the public becoming complacent about car alarms which are often ignored; and repeated activation of the siren can, over time, drain the vehicle battery or the siren primary battery, where fitted.

Vehicles with large interior volumes, large exterior body panels such as roofs or large trim pieces such as headliners are particularly prone to such false alarms.

These large surfaces are more prone to vibration caused by pressure changes and this movement is detected by the volumetric intrusion sensor and falsely interpreted as an attempted break-in.

It is against this background that the present invention has been conceived. It is an aim of the present invention to address the problem of false alarms in vehicle security systems based on volumetric intrusion sensors. Embodiments of the invention may provide a sensor arrangement, a light assembly, a security system, a method or a vehicle which improves the reliability of intrusion detection and reduces false alarms. Other embodiments of the invention may enable self diagnosis of a sensor array in a vehicle security apparatus in use. This approach greatly improves the reliability and effectiveness of the vehicle security system whilst keeping assembly time and cost to a minimum. Other aims and advantages of the invention will become apparent from the following description, claims and drawings.

Summary of the invention

Aspects of the present invention therefore provide a arrangement, an assembly, a system, a method and a vehicle as claimed in the appended claims.

According to an aspect of the present invention for which protection is sought, there is provided a sensor arrangement for a vehicle security system, the sensor arrangement comprising a sensor controller; a volumetric intrusion sensor; an accelerometer; and mounting means arranged to rigidly support the volumetric intrusion sensor and accelerometer together within a vehicle, wherein the sensor controller is arranged to generate an output in dependence on a comparison between the output from the volumetric intrusion sensor and the output from the accelerometer.

In an example, the sensor arrangement further comprises communication means for communicating the output from the sensor controller to a vehicle alarm and/or immobiliser.

Advantageously, rigidly mounting the volumetric intrusion sensor and the accelerometer together to the vehicle allows a vehicle security system to use the acceleration data to verify the output from the volumetric intrusion sensor and to increase robustness against false alarms. By mounting the accelerometer and the volumetric intrusion sensor in this way, an output from the volumetric intrusion sensor will only result in an alarm signal being generated if the accelerometer output suggests that the volumetric intrusion sensor output was due to a detected intrusion into the vehicle; and not just to a vibration of the entire vehicle.

According to another aspect of the present invention for which protection is sought, there is provided an interior light assembly for a vehicle, the light assembly comprising a sensor arrangement according to any preceding paragraph, a body, and a light, wherein the body is arranged to rigidly support the mounting means of the sensor arrangement and to secure the interior light assembly to a vehicle structure.

According to a further aspect of the present invention for which protection is sought, there is provided a security apparatus having a sensor arrangement according to any preceding paragraph and further comprising a control means and a memory, wherein the control means is arranged to monitor the output from the volumetric intrusion sensor and from the accelerometer of the sensor arrangement and to compare the frequency and the magnitude of the measured acceleration with acceleration threshold data stored in the memory, and to compare the output from the volumetric intrusion sensor with threshold data stored in the memory, and to issue an alarm signal in dependence on one or more predetermined threshold(s) being exceeded.

In an embodiment, the security apparatus further comprises a sound emitter means such as a siren, wherein the alarm signal issued by the control means is arranged to activate said sound emitter means.

According to yet another aspect of the present invention for which protection is sought, there is provided a method for securing a vehicle, the method comprising the steps of monitoring the output of a volumetric intrusion sensor; monitoring the output of an accelerometer; and upon detecting a change in the output from the volumetric intrusion sensor, and said change exceeding a predetermined threshold, comparing the output from the accelerometer with predetermined thresholds for frequency and magnitude, and in dependence on the magnitude exceeding a predetermined threshold, activating a vehicle security device.

Advantageously, this method is more robust against false alarms caused by environmental phenomena such as thunderstorms and low flying aircraft than known volumetric intrusion sensor based systems.

The accelerometer can also be used to act as a tilt sensor. This offers a cost saving where a tilt sensor is required, or greater capability for the same cost.

Fitment of a tilt sensor can sometimes lower the insurance group rating of a vehicle.

Within the scope of this application it is envisaged that the various aspects, embodiments, examples, features and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings may be taken independently or in any combination thereof. In particular, features described in connection with one embodiment are applicable to other embodiments, except where there is an incompatibility of features.

Brief Description of the Drawings

The present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a schematic view of a known vehicle security system; Figure 2 shows two views of the location of a known ultrasonic module or volumetric intrusion sensor arrangement within the vehicle of Figure 1; Figure 3 shows a schematic view of a sensor arrangement embodying one form of the present invention; Figure 4 shows a perspective view of the inside of an interior light assembly embodying another form of the present invention; and Figure 5 shows an example of a method of securing a vehicle embodying a further form of the present invention.

While the examples given below relate to security systems for passenger vehicles, it will be appreciated by one skilled in the art that there are potentially other uses for the present invention with non-vehicle applications such as warehouse security systems and with vehicles not intended for carrying passengers, such as trucks or other such commercial vehicles.

Figure 1 shows a schematic view of a known vehicle 1 fitted with a typical vehicle security system 100. The security system 100 comprises alarm means, in the form of a siren 2, for emitting an audible alarm, and sensor means, in the form of one or more volumetric intrusion sensors (VIS) 4, arranged to monitor the change in pressure in a vehicle occupant compartment 105. The VIS 4 is mounted to the inside of a roof panel 101 so as to be able to monitor the entire occupant compartment 105. Mounting the VIS 4 substantially centrally above the occupant compartment is also advantageous as it is inherently difficult for the would-be thief to tamper with the sensors without triggering the vehicle security system alarm.

The vehicle 1 includes a body control module (BCM) 3, in the form of a microprocessor or the like, arranged to communicate with a plurality of electrical systems within the vehicle, via a controlled area network bus (CAN bus) or other suitable means. For example, the BCM 3 is arranged to communicate with a central locking system 5 of the vehicle which is arranged to lock and unlock the vehicle doors in dependence on a locking command from the user. In the example shown, the BCM 3, the central locking system 5, the VIS 4 and the siren 2 are each powered by one or more batteries 6. It should be noted that the BCM 3 is shown in an entirely figurative location for ease of illustration.

The vehicle security system 100 is controlled by the BCM 3 or by another dedicated system controller (not shown), for example located in the siren 2, and is activated when the vehicle ignition is switched off and the doors are locked via the central locking system 5. Once activated, the vehicle security system 100 monitors pressure fluctuations within the occupant compartment 105 by means of the VIS 4.

The VIS 4 generally comprises one or more ultrasonic transducers arranged to emit ultrasonic frequency pulses and to receive the pulses reflected back from surfaces defining the occupant compartment 105. Once activated, the VIS 4 continues to emit ultrasonic frequency pulses into the occupant compartment 105 and looks for any sudden changes in the pattern of pulses reflected back.

As the occupant compartment 105 is effectively a closed volume, any sudden variation in pressure is interpreted as an attempted break-in. If the occupant compartment 105 remains closed, the interior pressure will remain constant and there will be no change in the pattern of pulses reflected back to the VIS 4. In this case, no alarm will be activated.

However, if certain characteristics of the occupant compartment 105 change, for example if a door is opened or if a window is smashed, the change in the pattern of pulses reflected back to the VIS 4 will result in the activation of the siren. Upon detection of such an event, the vehicle security system 100 is arranged to emit a loud audible alarm by means of the siren 2 to attract attention and to deter the intruders.

Figure 2a illustrates the location of a known volumetric intrusion sensor arrangement, or ultrasonic transducer module (104, Fig. 2b), mounted within a headliner trim lOla covering the roof 101 of the vehicle 1 of Figure 1. For clarity, in Figure 2a the ultrasonic transducer module 104 has been removed from its mounting 102 in the headlining but is shown in detail in Figure 2b. From the Figure it may be seen that the ultrasonic transducer module 104 is located substantially in-line with the longitudinal centreline of the vehicle, just rearward of a pair of sun-visors lOis which are shown in a stowed position, folded flat against the headliner trim lOla. Locating the ultrasonic transducer module 104 in this position facilitates optimal coverage for the volumetric intrusion sensors in the ultrasonic transducer module 104 within the occupant compartment (105, Fig. 1) as a whole.

Figure 2b shows the ultrasonic transducer module 104 in isolation from the mounting (102, Fig. 2a). The ultrasonic transducer module 104 communicates with the other components of the vehicle security system (100, Fig. 1) via a harness shown generally at 106. The harness 106 is provided with detachable connectors 103 arranged to cooperate with corresponding connectors integrated within the ultrasonic transducer module 104 and with other components of the vehicle security system 100.

As the ultrasonic transducer module 104 is mounted directly to the headliner trim lOla or to the vehicle roof 101 via the mounting 102, any significant vibration of the roof 101 or headliner trim lOla may cause the ultrasonic transducer module 104 to move relative to the occupant compartment 105. Any relative movement between the sensors within the ultrasonic transducer module and the vehicle may be interpreted as an attempted break-in and give rise to a false alarm. As the roof panel is one of the largest simply-supported panels within the vehicle, it is particularly prone to vibration caused by commonly occurring external forces such as a heavy vehicle moving past the alarmed vehicle, a sudden heavy downpour of rain or hail, or even a sufficiently loud clap of thunder. Any such event may cause the roof 101, with its relatively large surface area, to vibrate and confuse the volumetric intrusion sensors of the vehicle security system 100, triggering an alarm unnecessarily.

Figure 3 shows a schematic view of an example of a sensor arrangement 10 embodying one aspect of the present invention. The sensor arrangement 10 comprises at least one sensor 14 in the form of an ultrasonic transducer arranged to provide volumetric intrusion sensing, a sensor controller 1 3, an accelerometer and mounting means in the form of a body 11 arranged to rigidly support the sensor 14 and accelerometer 15 together within a vehicle 1. The sensor controller 13 is arranged to compare the output from sensor 14 and accelerometer 15, and to generate an output in dependence thereon. This comparison advantageously acts to filter out erroneous data, and thus reduces the chance of false alarms.

In an embodiment, the sensor arrangement 10 comprises part of a vehicle security system 210, which may further comprise a central locking system 214, alarm means in the form of a siren 212 or the like, and control means in the form of a body control module 213.

The vehicle security system 210 is activated whenever the central locking system 214 is in a locked state and the body control module 213 determines that the vehicle I is switched off. The on-off state of the vehicle I may be determined when a signal from a vehicle ignition line (IGN) received by the BCM 213 is indicative that the vehicle ignition is in an inactive state.

In the activated state of the security system 210, the sensor 14 is arranged to substantially continuously transmit ultrasonic signals into the vehicle cabin and to receive the reflected pulses. Simultaneously, the accelerometer 15 is arranged to monitor movement of the vehicle and/or of the panel to which the sensor arrangement is mounted.

The sensor controller 13 is arranged to constantly monitor the output from both the accelerometer 15 and the sensor 14 and to communicate with the BCM 213. The sensor controller 13 compares the output from the sensor 14 with that of the accelerometer 15 to verify whether the sensor 14 has detected an attempted break-in or is confused by environmental stimuli such as a thunderstorm. This comparison is shown in Figure 5 and will be described in further detail shortly.

If it is determined by the sensor controller 13 that a break-in has been or is being attempted, the sensor controller 13 generates an alert signal to the BCM 213 which then activates the siren 212 to emit the audible signal.

Figure 4 shows an example of an interior light assembly 350 for a vehicle 1, according to another aspect of the present invention. The light assembly 350 comprises a light source 351, such as an incandescent bulb or a light emitting diode (LED), a light switch 370, and a light reflector 360 arranged to direct light into the occupant compartment 105 in use. The light may be activated automatically in dependence on a signal from the BCM indicating that a vehicle door has been opened, or alternatively may be operated manually via the switch 370.

The light source 351 is mounted to a body 311 arranged for substantially rigidly mounting the light assembly 350 to the roof of a vehicle. In the example shown, a sensor arrangement 310, which may be substantially identical to the sensor arrangement 10 of Figure 3, is mounted to the body 311 such that both the light 351 and the sensors of the sensor arrangement 310 are situated together in a location arranged for optimal coverage of the occupant compartment 105.

In the example shown in the Figure, the sensor arrangement 310 is shown with two ultrasonic transducer modules 314 and an accelerometer module 315, mounted to or integrated with the body 311. By sharing the same rigid mounting, provided by the shared body 311, any vibration affecting the ultrasonic transducer modules 314 will be detected by the accelerometer module 315. In this way, the sensor controller 313 can compare any alarm signal generated by the ultrasonic transducer modules 314 and compare it with the output from the accelerometer 315 so as to determine the validity of the alarm signal.

The ultrasonic transducer modules 314 are arranged to provide the vehicle security system with a robust means to sense volumetric intrusion into the vehicle occupant compartment 105. The accelerometer in the accelerometer module 315 is arranged to provide the sensor controller 313 with a means to filter out potential false alarms that may be generated by the ultrasonic transducer modules 314, improving reliability and minimising the risk of false alarms in use.

Figure 4 also shows an electrical harness 306 arranged to connect the interior light assembly 350 and integrated sensor arrangement 310 to the vehicle 1 via connector 303. The electrical harness 306 is arranged both to supply power to the electrical components within the interior light assembly 350 and to communicate data between the sensor arrangement 310 and other vehicle based electrical systems such as the vehicle central locking system 214 and/or the BCM 213.

Figure 5 shows an example of a method of operation of the system of Figures 3 and 4. In particular, it is shown how the BCU 213 may interpret the output from the sensor arrangement 310 of the present invention to secure a vehicle 1. The logic table illustrates how data received from the volumetric intrusion sensors 314 is compared with that of the accelerometer 315 to distinguish between an attempted unauthorized access to the vehicle interior, and a false alarm caused by vibration etc. In the example shown, the logic table has three columns: the first column contains the output from the ultrasonic transducer modules 314. The second column contains the output of the accelerometer module 315. The third column indicates the response actioned by the BCU 213 in dependence on the data in the first two columns.

The logic table of Figure 5 shows a suitable response to four conditions, The sensor controller 313 is arranged to compare the output from the sensors 314 with the output from the accelerometer 315.

In the first scenario, the output from both ultrasonic sensors 314 and accelerometer 315 is below predetermined threshold limits.. Such a situation is often associated with the vehicle being rocked on its suspension by a gust of wind, or when parked in the hold of a ferry for example. In this instance, it would not be appropriate to activate the siren 212 and so no such alarm signal is generated by the vehicle security system. Such events are a known cause of false alarms with existing vehicle security systems, and can prove a nuisance to those within earshot of the vehicle alarm.

In the second scenario, the output from the accelerometer 315 is below a predetermined threshold for frequency but has a significant magnitude. Such a situation may be caused by acts of theft against the vehicle (for example, vehile towaway or wheel theft), and as such the alarm signal is not suppressed as it was in the first scenario, resulting in the activation of the siren 212 by the BCU 213.

In the third scenario, the output from the accelerometer 315 is above a predetermined threshold for frequency but has insignificant magnitude. Such a situation may be caused by natural events such as heavy rain or hailstorms, where raindrops or hailstones repeatedly strike the roof and other panels of the vehicle body and as such, the alarm signal is suppressed as it was in the first scenario and the siren 212 is not activated.

In the fourth scenario, there is little or no output from the accelerometer, but the output from the intrusion sensor is above a predetermined threshold. Such a situation may be caused by acts of vandalism or attempted theft of the vehicle or its contents, such as when a vehicle window glass is smashed; and as such, an alarm signal is generated and the siren is activated.

It may be seen from the description above, that naturally occurring events such as wind or hailstorms, which are known causes of false alarms in traditional vehicle security systems, are effectively filtered out by the use of the sensor arrangement of the present invention.

The sensor arrangement 310 addresses the known causes of false alarms by providing a means to identify whether the volumetric intrusion sensor 314 is moving relative to the vehicle occupant compartment 105, or whether an object or person has entered occupant compartment 105. The present invention thus seeks to reduce the susceptibility of volumetric intrusion sensor based security systems to false alarms caused by vibration whilst at the same time reducing vehicle assembly time and improving perceived vehicle quality.

Other advantages will be apparent to one skilled in the art and the present examples and embodiments are to be considered illustrative and not restrictive.

The invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.

Claims

CLAIMS1. A sensor arrangement for a vehicle security system, the sensor arrangement comprising: at least one volumetric intrusion sensor; an accelerometer; and control means arranged to compare an output from the at least one volumetric intrusion sensor and an output from the accelerometer and to generate an output in dependence thereon.
2. A sensor arrangement as claimed in claim 1, comprising mounting means for substantially rigidly supporting the volumetric intrusion sensor and accelerometer adjacent each other within a vehicle.
3. A sensor arrangement as claimed in claim I or claim 2, comprising communication means for communicating the output from the control means to a vehicle alarm and/or immobiliser.
4. A sensor arrangement as claimed in any preceding claim, wherein the output from the accelerometer comprises vibration frequency and magnitude data and wherein the control means is arranged to compare the output from the volumetric intrusion sensor with first threshold data and to compare the vibration frequency and magnitude data with second threshold data and to output an alarm activation signal in dependence on one or more predetermined thresholds being exceeded.
5. An interior light assembly for a vehicle, comprising: a light; a sensor arrangement as claimed in any preceding claim; and a body arranged to rigidly support the light and the sensor arrangement and to secure them to a vehicle.
6. A security system for a vehicle comprising a sensor arrangement as claimed in any of claims ito 4.
7. A security system as claimed in claim 6, comprising alarm means for generating an audible alarm in dependence on the output from the control means.
8. A method comprising: monitoring the output of a volumetric intrusion sensor fitted to a vehicle; measuring the vibration of the volumetric intrusion sensor with an accelerometer; monitoring the output of the accelerometer; and upon detecting a change in the output from the volumetric intrusion sensor that exceeds a predetermined threshold: comparing the output from the accelerometer with predetermined thresholds for vibration frequency and magnitude; and activating a vehicle security device in dependence on the vibration frequency and/or magnitude exceeding a predetermined threshold.
9. A vehicle comprising a sensor arrangement as claimed in any of claims I to 4.
10. A vehicle comprising an interior light assembly as claimed in claim 5.
11. A vehicle comprising a security system as claimed in claim 6 or claim 7.
12. A sensor arrangement, light assembly, security system, method or vehicle constructed and/or arranged substantially as described herein with reference to Figures 3 to 5 of the accompanying drawings.