GB2405513A - Personnel detection within vehicles - Google Patents

Abstract

To detect stowaways in the trailer of a trailer tractor combination a respiratory carbon dioxide (CO2) 11 detector is provided within the cargo bay of the trailer. The detector is coupled through a microprocessor 12 to a CAN (Controller Area Network) controller 14. The controller 14 is connected to dc power cables 15 so that encoded data signals using a standard CAN protocol can be sent to a second CAN controller 16 in the tractor unit. The second controller 16 is coupled through a second microprocessor 17 to an interpretative display 18. The display may be powered by a standard cigarette lighter power outlet. The CO2 detector is preferably a Non-Dispersive Infra Red (NDIR) sensor.

Description

24055 1 3 On Board Vehicle Detection & Monitoring {Personnel Detection

from Respiratory Carbon Dioxide} This invention relates to on-board (road) vehicle or vessel 'condition' defection and monitoring and is particularly, but not exclusively, concerned with personnel detection from respiratory carbon dioxide (C 2)

Background

The UK government has introduced legislation, to the effect that every illegal immigrant stowaway found on board a truck entering the UK attracts a 2000 fine per person for the driver.

Thus, between April and December 2000 UK, hauliers paid out some 7 million in fines.

Up to 500 stowaways are caught every month entering the UK via the Channel Tunnel alone.

This puts an extra burden on the haulage industry that it cannot afford.

The vast majority of the truck drivers are innocent victims and are unaware of stowaways until a customs search - by which time it is too late.

Carbon dioxide (CO2) detectors are known per se and have been applied to personnel detection.

However, if all trailers had a detector fitted, the driver could be alerted to the presence of stowaways before arriving at UK customs.

A difficulty arises when a trailer is attached to a different tractor unit.

If a detector and reporting function were outside the trailer, they could be a target for vandalism.

A driver would also need to get out of the truck to investigate.

At all times a driver needs to know, from within the cab, the status of the CO2 detector in a cargo bay.

... ..: : : : . .

Prior Art

Diverse earlier proposals for freight vehicle tractor trailer on-board data transfer include: US2002/01 67398A1 Strasser contemplates data transfer along a vehicle power line carrier - albeit with primitive encoding vision and no recognition of noise interference and attendant data corruption.

A prime consideration of Strasser is retro-fit of proximity detection technology for cars to trailer combinations (Heavy Duty Tractor-Trailer Unit HDTTU) with attendant driver blind spots.

Vehicle construction and use regulations are not addressed and the potential multiple discrete warning indications could prove a driver distraction.

Practical problems include the need to retro-fit older vehicles which may not have an existing data route, without supplementary wiring.

For contemporary vehicles with some data routing provision for internal vehicle operations additional condition data must conform to existing standards or protocols, without degrading original functionality.

Statement of Invention

Principle considerations of the invention include: Routing relay of warning detection indication to driver cab audio-visual display; use of power supply (eg tail light) circuitry for data relay;

filtering to address problem of background

noise inherent in power supplies; Encoding encoding of data - conformity with established standard data transfer protocol; ::. e. ... .:e ee. e.

Compatibility compatibility with vehicle wiring systems both with and without dedicated data lines.

According to one aspect of the invention, a remote condition sensing system, such as for road vehicle operation, comprises a condition sensor or detector, to produce an output signal according to condition; a microprocessor for receiving detector output; and a controller for modulating signals for a communications channel.

In a particular implementation, a personnel detector comprises: a respiratory gas sensor for monitoring gas levels in a closed environment; a controller to determine gas levels reaching a predetermined threshold; and a warning indicator, responsive to controller determination, for producing a warning of personnel occupancy of monitored environment.

Detector sensitivity is modelled to embrace a worst case of a single individual in an otherwise empty trailer environment.

A detector may be coupled to an indictor through a vehicle power supply for supply modulation according to condition data, or through a dedicated data link.

Data Relay over Power Line Absent an existing data path, data representing selected criteria can be relayed over a power supply line by digital encoding through an isolating interface or buffer.

That said, an existing data line, such as one employing an appropriate CAN protocol, may be employed.

Such data may represent a condition detected - and measured or quantified - by a remote sensor.

Freight Vehicle Context A particular context is a road freight vehicle whether ::. ë . c:. ë *e . . rigid bodied, or an articulated configuration of close coupled tractor unit and trailer.

Personnel Detection Some form of (unauthorized) personnel detection say, through environmental change consequent upon space occupancy - is needed for freight transport and storage. 1 0

Low Voltage Power Supply A vehicle power supply is typically low (12 or 24Volt) do voltage and certain aspects of the invention are concerned with digitising and encoding data for relay over do power lines through a coupling interface.

Power Circuit Noise Power circuits are inherently noisy - not least given connection to electrical power generators, such as alternators, for battery charging - with potential for random and spurious interference.

Filter & Data Encoding Some form of filter and/or robust encoding and decoding allows discrimination between data line voltage and supply voltage.

A typical power supply circuit would be to on-board vehicle lighting.

CO2 Sensing In a particular sensing mode, CO2 levels within a vehicle (truck or trailer cargo bay) are monitored by on-board sensors or detectors and relayed through vehicle electrical power supply cables to a warning control unit.

Operationally, other diagnostic or environmental condition data may also be relayed in this way.

Conveniently, a self-contained portable display module could plug into a standard driver cab cigarette lighter power outlet socket.

e ee. ce. a. ee i.e. Embodiment

There now follows a description of a particular

embodiment of the invention - specifically a personnel detector for a cargo truck - by way of example only, with reference to the accompanying schematic and diagrammatic drawings.

An inter-coupled discrete tractor and trailer combination is depicted severability and separation of elements being a consideration.

That said, the invention is applicable to a unitary truck with integral cargo bay and driver cab. 1 5

Personnel detection is by respiratory gas - in particular (low level) CO2 sensing - in a closed environment.

In the drawings: Figure 1 A shows a block schematic of a transmitter and receiver interconnected by a power supply line in this case an umbilical harness coupling between freight transport vehicle tractor and trailer units; Figure 1 B shows a side elevation of a tractor and trailer combination fitted with one or more remote condition detectors of Figure 1A; Figure 2 shows a'top level' overall operational software flow chart for condition detector signal recognition and relay, with intervening sleep shut down mode, in the system of Figures 1 A and 1 B; Figures 3A through 3C show command encoding tables for the system of Figures 1 A through 2; More specifically; Figure 3A shows a message matrix of identity code, message nature, detector and display mode; Figure 3B shows a message data table of identity (ID) code allocation, significance and line state; Figure 3C shows a transmit / receive data byte

conversion table;

Figure 4 shows a circuit diagram of detector amplifiers used in the system of Figures 1A through 3C; :.e hi. . .. .:e.e Figure 5 shows a circuit diagram of detector connectors; Figure 6 shows a circuit diagram of a detector lamp; Figure 7 shows a circuit diagram of a detector modem; Figure 8 shows a circuit diagram of a detector power supply; Figure 9 shows a circuit diagram of a detector processor; 1 5 Figure 10 shows a circuit diagram of a detector pump drive; Figure 11 shows a circuit diagram of a detector sub board; Figure 12 shows a top level schematic of a detector; Figure 13 shows a circuit diagram of a display processor; Figure 14 shows a circuit diagram of a display power supply; Figure 15 shows a circuit diagram of a display modem; Figure 16 shows a circuit diagram of display connectors; Figure 17 shows a top level schematic of a display; Figures 18A through 18C depict graphically percentage concentration c(t) of CO2 plotted against time, for a notional stowaway in a given volume of air; More specifically, Figure 18A illustrates change in CO2 concentration in a 15m3 void; Figure 18B illustrates change in CO2 concentration in a 66.24m3 void (equivalent to an empty trailer); Figure 18C shows the two plots of Figures 18A and 1 8B on the same graph - for comparison between ::e.e ë.e ee:e.e *.e different volumes; Figure 19 shows the construction of a message in CAN 2.0a Standard Format.

Referring to the drawings A cargo bay (sensor - detector) module 20 and cab (control) module 30 are interconnected by vehicle electrical power supply cables 15.

The cargo bay module 20 incorporates one or more sensors or detectors 11 coupled through a microprocessor 12 to a controller 14.

Controller 14 is connected through an interface or buffer 13 to power cables 15.

Interface 13 effectively isolates module 20 from adverse' power supply effects, such as inherent noise, but allows encoded data signals to be relayed intact and unadulterated.

Cab module 30 incorporates an 'interpretive' condition display 18, coupled through a microprocessor 17 to a controller 16.

Controller 16 is connected - through an interface or buffer 19 - to power cables 15.

Protocol Controllers 14 and 16 adopt a predetermined - in this case a socalled CAN (Controller Area Network) standard communications protocol for data transfer.

Cargo bay module 20 can be fitted covertly or discretely at a strategic location in a trailer 40.

At a minimum, module 20 can house an individual detector 11, as depicted.

A single sensitive detector can respond to modest change in ambient CO2 levels through individual respiration in a relatively large enclosed volume.

That said, supplementary remote detectors 11 (per Figure 1 B) can be connected (say, in series) to increase effectiveness of cover.

a.. a.

Cab module 30 is fitted to a vehicle driver cab 50.

Personnel Detection - Respiratory Effect Respiration of CO2 in the cargo bay 40 affects the containment volume condition - with progressively raised CO2 levels - sensed as a basis for personnel detection in the present case.

1 0 CO2 Detection A small CO2 detector 11 is fitted unobtrusively at a low point in cargo bay 40 in order to obscure it from vision. 1 5

Notwithstanding CO2 being a heavier gas than air, tests have shown that concentration levels of CO2 tend to be greater above floor levels.

However, detector concealment from any illegal occupants is an overriding consideration.

Minimal detector intrusion into cargo space is desirable, consistent with taking a representative internal air sample.

The detector measures CO2 concentration within the cargo bay confines.

In practice, air is sampled not merely by passive interaction with the immediate environment, but by remote sampling using a forced air flow created by a pump sampling from one or more intake locations.

Detector Sensitivity Model A detector sensitivity model, described later, is employed to embrace a worst case scenario of a single individual in an otherwise empty cargo hold.

Measurement Measurement methodology is NDIR (Non-Dispersive Infra Red).

CO2 molecules absorb light at a specific (characteristic) wavelength of some 4.26 m.

This wavelength is in the infra-red (JR) range.

in.. e.. .e.:.

Preferably, gas molecules are actively pumped from a cargo bay into the detector.

However, in certain applications molecules may simply diffuse from the immediate environment into a sensing chamber.

IR light is directed through a sensing chamber toward an IR detector. 1 0

The detector is prefaced by a dual (mode) filter.

One filter eliminates all light except the 4.26 him wavelength that CO2 molecules can absorb; and another allows full IR intensity as a reference channel.

Since other gas molecules do not absorb light at this wavelength, only CO2 molecules affect the amount of light reaching the measured channel.

The intensity of light, at 4.26 him wavelength, that reaches a detector 11 is inversely related to CO2 concentration in the sensing chamber.

When CO2 concentration in the chamber is zero, the detector will 'see' full light intensity.

As CO2 concentration increases, the intensity of light striking the detector decreases.

The precise relationship between IR light intensity and CO2 concentration is determined when the detector is calibrated, using: pure nitrogen (0 ppm CO2); and a known concentration of CO2, such as 1000 or 5000 ppm.

Beer's Law defines intensity of light striking the detector: I = 10e-kP Where: I = Intensity of light striking the detector.

lo = Measured reference of 0 (zero) ppm CO2 ece e

C C

C ' ' C- k = Attenuation coefficient P = Concentration of CO2 Data Processing Operationally, CO2 concentration measured by IR detector 11 is expressed as an output voltage to microprocessor 12.

Thus voltage level is dependent upon - and reflects CO2 concentration.

Microprocessor 11 converts this voltage into a standardised - in this case so-called CAN (Controller Area Network) - message data format or protocol that communications link 15 (addressed through interface 13) can use.

Trailer to Cab Communications Data collected by the CO2 detector is: processed into CAN (Controller Area Network) messages; and modulated, using ASK (Amplitude Shift Keying), at a baud rate of 1 Okbits / sec.

The medium for transmitting CAN messages is do power cables 15 that supply trailer electrical power.

An example would be a (trailer side and rear) lighting circuit.

Data is received by a display module 18 that can: plug directly - as an aHer-market accessory into a standard cigarette lighter power supply outlet fitted in a driver cab.

integrate with a driver information systems, if offered by the tractor unit OEM as a factory fitted cab option.

Fleet Capability A truck (tractor) fleet with such message receiving equipment could monitor CO2 levels in any trailer fitted with CO2 detection.

A:: . :: ::.. A:: ::.

Receiver / Display As described, a receiver of CO2 detector messages could couple directly to a vehicle electrical power distribution network.

A display could be a simple set of intuitive icon imagery and/or warning lights.

Icons and/or simple warning lights - with optional audio sound - would alert a driver to increased CO2 levels to a level indicative of respiratory discharge.

This would allow a driver to notify appropriate authorities, without having to inspect the cargo space - and risk confrontation with, or escape by, unauthorized occupants.

Sensitivity - Trigger Threshold A trigger threshold could be predetermined for prompt detection of even a minimal personnel presence.

2 5 Detector tamper, or power loss could also trigger an alert.

Generally, electronic system detection of increased levels of carbon dioxide utilises detection and information units.

A detection unit samples air from the area that a stowaway may hide in to determine increased levels of carbon dioxide (CO2).

The detection unit continuously measures the concentration of CO7 and converts the measured data into CAN (version 2.0a) format and 'broadcasts' formatted data over vehicle DC power cables.

The information unit interprets the broadcast data and displays CO2 concentration to the user.

As the data is present on the DC power cables, the system is extremely flexible - in that the data can be read from both inside and outside the vehicle.

In the case of tractor and trailer trucks, this allows data to be read from any tractor and trailer combination. 1 1

A: <: : A: :. . : a'.

.e: CO2 Detection Carbon dioxide CO2 detection has been proposed, but sensitivity and operating threshold problems arise in detecting a stowaway in a closed environment.

Proprietary CO2 detectors currently available are precision instruments and able to detect very high concentrations of CO2 - but at levels that would be fatal to humans.

Thus, typical commercially available detectors have sensitivity ranges of O - 2% or 0 - 10%. 1 5

Concentration effects are summarised as follows: 0.04% CO2 Concentration No adverse effect - as this reflects normal atmospheric carbon dioxide concentration.

0.5% CO2 Concentration Lung ventilation increases by 5 percent.

This is the maximum safe working level recommended for an 8 hour working day in industry (Australian Standard).

1.0% CO2 Concentration Symptoms may begin to occur, such as feeling hot and clammy, lack of attention to details, fatigue, anxiety, clumsiness and loss of energy - commonly first noticed as a weakness in the knees (jelly legs).

2.0% CO2 Concentration Lung ventilation increases by 50 percent, headache after several hours of exposure.

Accumulation of carbon dioxide in the body after prolonged breathing of air containing around 2% or greater will disturb body function, by causing the tissue fluids to become too acidic.

This will result in loss of energy and feeling run down even after leaving a confined enclosure.

It may take several days in a good environment for the body metabolism to return to normal.

::. :e::- A e as.

ë' 'e' *' 3.0% CO2 Concentration Lung ventilation increases by 100 percent, with panting after exertion.

Symptoms may include headaches, dizziness and possible vision disturbance such as speckled stars.

5 - 10% CO2 Concentration Violent panting and fatigue - to a point of exhaustion merely from respiration, along with severe headache.

Prolonged exposure at 5% could result in irreversible (adverse) effects to health.

Prolonged exposure at > 6% could result in unconsciousness and death.

10 - 15% CO2 Concentration Intolerable panting, severe headaches and rapid exhaustion.

A few minutes exposure results in unconsciousness and suffocation, without warning.

25% to 30% CO2 Concentration Extremely high concentrations cause coma and convulsions within one minute of exposure - and an outcome of certain death.

From the foregoing data, a very narrow sensitivity range is required to detect a person hiding in a confined cargo area.

The Applicants have developed a mathematical model to determine this range and bespoke circuitry for reliable detection without spurious alarm.

Mathematical Model - Small Void A notional stowaway is hiding in a truck or trailer cargo area with a void am long, 2 m wide and 2.5 m high.

Stowaway breathing rate depends linearly upon carbon dioxide amount (or level) in ambient air.

When air has its usual 0.04% carbon dioxide level, respiratory rate is some 0.015 me per minute.

However, when carbon dioxide level increases to 3.0%, rate of breathing doubles.

:. . ad'.: i: Air breathed out (expired / exhaled) contains about 4.0 percent more CO2 than air breathed in (inhaled / inspired).

Rate of breathing 'r' depends linearly upon CO2 concentration level'c'.

Thus, when: 1 0 c=0.04%, r=0.015m3;and c=3%, r=0.03m3.

Thus, the slope is [1 1] ( 3 0 0 04)= 0 005068 Therefore the line is (r-0.015)=0.005068 (c-0.04) or [1.2] r = 0.005068c + 0.0148 This gives the breathing rate (in cubic metres per time), as a function of percentage carbon dioxide concentration.

The only way carbon dioxide concentration in the void can increase is with carbon dioxide in expired air.

Since expired air contains about 4% carbon dioxide, the rate of additional CO2 added to the cargo area = 0.04 x'r' (rate of respiration).

Rate of respiration 'r' itself depends on the amount of carbon dioxide in the air.

This was expressed above in terms of percentage CO2 in a cargo area.

The rate of change of CO2 in the air through respiration can be expressed, knowing the amount of CO2 in the air.

Let Q(t) be the amount of carbon dioxide in the void at time 'I'.

I. . ,, 1,., Then, [1 3] dQ=0 04, r= 0.04x(0.005068c + 0.0148) This reflects that the rate of change of CO2 in the air is 4% of the air moved through respiration.

The percentage concentration c(t) can be expressed in terms of quantity Q(t) - knowing cargo area void volume. Thus,

c= Q x100= Q x100 Volume (3x2x2.5) = Q5 x 100= 20Q [1.4] Q= 20 c Thus, 23 ddc = 0.04x(0.005068c + ().0148) [1 5] ddc = 0.001352c + 0.00395 Solving for c(t), [1.6] c(t)=07e . ls21 -().661 Figure 18A shows a graph of change in CO2 concentration in a 15m3 void.

This graph shows that it takes: 2.5 hours for CO2 concentration in a 1 5m3 void to rise to 0.2%; and over 5 hours before CO2 concentration reaches 0.4%.

. . . . X397.PO4028 en. -he c . . . C. Mathematical Model - Empty Trailer A worst case scenario, from a detection perspective, is an empty trailer with a single person inside.

However, this scenario is unlikely to occur very often, as haulage companies try to avoid making trips without any load, to maximise cost efficiency.

This scenario is modelled as above, in order to determine how sensitive the detector needs to be and is based on a 66m3 trailer (12m x 2.3m x 2. 4m).

The model is the same as before - with the exception of void volume - so performing the calculations again from Equation [1.4]: c= Q x100= Q x100 Volume ( 1 2x2.3x2.4) = 66Q24 x100= IOOQ [1 7] . Q= 66 24 c Thus, 66 24 dc = 0 04x(0.005068c + 0.0148) [1.8] ddC=3.062xlO 4c+8.9372x10-4 Solving for c(t), [1.9] c(t) = 2.96e3 Ox lo 2.92 Figure 1 8B shows a graph of change in CO2 concentration in a 66.24m3 void (empty trailer).

The two models are very similar.

The difference is shown in the graph of Figure 1 8C.

It can be concluded from these models that CO2 detector sensitivity should range from 0.04% to 0.5% concentration. . .

. . . . . The model is slightly inaccurate - in that it does not take into account any CO2 lost or replaced through natural ventilation.

Controlled vehicle tests are performed to assess and compensate for this.

Measurement Method The detector measures CO2 concentrations inside a void where detection is required.

The method of measurement is NDIR (Non Dispersive Infra Red). 1 5

CO2 molecules absorb light at a specific wavelength of 4.26 m.

This wavelength is in the infrared (JR) range.

Gas molecules are pumped into a sensing chamber.

IR light is directed through the sensing chamber towards the IR detector.

The detector has a dual filter in front of it.

One filter eliminates all light except the 4.26 him wavelength that CO2 molecules can absorb, as a 'Measure' charnel.

The other filter allows full intensity of infra red source, as a 'Reference' charnel.

Other gas molecules do not absorb light at 4.26pm wavelength, so only CO2 molecules affect the amount of light reaching the IR detector measure channel.

The intensity of light, at 4.26 m, that reaches the detector measure channel is inversely related to the concentration of CO2 in the sensing chamber.

A differential arises between measure and reference channel outputs as CO2 concentration increases.

When chamber CO2 concentration is at ambient levels, there is zero differential between measure and reference channels.

. . . . . .. . ..

. . . . . ace . As CO2 concentration increases, intensity of light striking the measure channel decreases.

The difference between measure and reference channels increases as void CO2 concentration rises.

Air Sampling It is necessary to pump air from the void to be sampled directly into the measurement chamber, in order to reduce the time taken to detect a person hiding in that void.

The detection system has a small electric pump 1 5 fitted.

The pump draws air into the sensing chamber at a rate of some 0.86 to 2.6 litres/minute (depending upon situation).

This also aids positioning of the detection unit, by removing the need to locate it at a point close to potential hiding places and allows the installation of sampling tubing around an area to be sampled.

Pump motor current is measured - allowing diagnostic information to be gathered.

If any obstructions or other changes occur in the system, motor current will change - and this is indicated to the information unit.

CO2 Measurement NDIR detection relies upon an infra red source and a detecto r.

In practice, an infra red source can be contrived with a small incandescent bulb, rated at 1 2Vdc, but driven at 5Vdc.

For infra red energy emission the bulb needs to glow slightly - as too much light will affect the detector.

Driving the bulb slightly also increases its life expectancy.

The bulb is pulsed at 5Hz, also increasing its life expectancy.

This gives a corresponding pulsed output from the A: : ..e c- : e . ... .

. . detection channels.

The bulb is driven by a transistor, controlled by a microprocessor.

Bulb current is measured for diagnostic purposes.

Signal Amplification As described previously, concentration levels that can be measured by the present invention are very small (<5000ppm).

Consequently, CO2 detector measure and reference channels need to be amplified considerably.

An example detector is a proprietary LIM122 model, of Laser Components gmbh.

Detector output signals are ac coupled to a main amplifier stage by a small signal amplifier.

The main amplifier stage itself is a pair of do amplifiers, with roll off at about 1 OHz - see Figure 4.

Additionally care must be taken to ensure that the separate amplification circuits for both channels for the ac coupled small signal amplifiers are symmetrical, in order to maintain identical channel impedance see Figure 11.

Data Processing CO2 concentration measured by the infrared detector is in the form of two separate outputs from respective amplification stages.

These dual outputs are converted to digital signals by Analogue-toDigital Converter (ADC) inputs of the microprocessor (Figure 9).

The microprocessor performs a simple calculation, to determine CO2 concentration and converts this to CAN 2.0a format message data.

Formatted data is then passed to a modem circuit (Figure 7), via a series of logic gates, for the microprocessor to determine if the system is sending or receiving a message.

.e : ::: ee. c e. Modem

The modem circuit is the medium for transmitting and receiving messages between the detection and information units.

The modem consists of a protection network, a filter and a reception amplifier.

The protection network is designed to prevent low frequency and do levels from damaging the modem circuits.

In receive mode an analogue switch is enabled, which enables the receiving amplifier.

During transmission, the receiving amplifier is disabled, to prevent it from loading the filter during reception.

Power Supply The power supplies (Figures 8, 14) are configured to cope with a harsh automotive environment.

The detection unit requires dual (5Vdc and 12Vdc) voltages for different sections, derived from a 24Vdc (commercial vehicle battery) source.

A switching power supply is employed for 5Vdc circuits, to ensure maximum thermal efficiency.

A linear 12Vdc regulator has been used for 12Vdc circuits, to reduce costs. Low power consumption of 1 2Vdc circuits makes this implementation more

practical.

The information unit has a single 5Vdc switching power supply, as it only requires 5Vdc derived from the 24V vehicle supply voltage.

The power supply circuitry can accommodate a wide range of supply voltages, with minimal change.

Memory A separate memory IC (Integrated Circuit) records a number of samples, as a history of events.

The memory is non-volatile and will retain data even .: .: .-. eye: . . . ...

.. . . when it has been powered down.

The memory can store some 8 kbytes of data and is operated on a FIFO (First In First Out) basis.

Storage of data points is programmable e.g. every 10 minutes.

The memory will also log faults that occur on the 1 0 system.

Diagnostics The detection and information modules have built-in diagnostics, in case either develops a problem.

If a fault occurs, the user is alerted to the nature of the fault via the information module.

All faults are logged in the on-board memory.

Receiver/Display The receiver of CO2 detector messages couples directly to a vehicle electrical distribution network.

This is achieved by plugging the unit directly into a cab cigarette lighter power outlet, or is factory fitted to the cab by the OEM.

The display provides a CO2 concentration level indication by means of a simple set of icons and/or warning lights - to a exact format to be determined by customer feedback.

The display unit will alert the driver in the event of the detector being unable to complete its function due to failure or tampering.

4 0 Detectable faults include: Gas detection circuit failure Sampling pump failure Sampling pump tubing blockage Loss of Communications Detector power failure Software Design Figure 2 shows a top level flowchart of the software design.

. . . . . . ace

Message Specification

This section contains the system specific requirements for the CO2 detection system communications protocol.

This part of the specification defines the CAN

messages to be used in the system and their physical meaning. It is arranged in three tables:

TABLE 1 (Figure 3A)

CAN Message Matrix - defines the message parameters to be transmitted and received by each node.

TABLE 2 (Figure 3B)

CAN Message Details - defines the structure and meaning for each parameter.

Several parameters may be packed within a single CAN message as defined in the tables.

Any node wishing to receive a parameter, must receive all the parameters contain within the message in which the parameter is transmitted.

All nodes shall ignore any parameters contained within a received message that are not required.

TABLE 3 (Figure 3C)

Transmit / Receive Data Bytes Conversion Table encodes the number of bytes being transmitted in a following CAN message.

Message Construction The message from the microcontroller that contains the data from the optical sensors and from the receiver/display is standard CAN 2.0a format (see Figure 19), with additional data at the beginning of the message to instruct the modem what to do with the data bytes presented to it.

* When transmitting messages of this format, the microprocessor adds OxFn (see Figure 3C) to the front of the CAN message.

see e e ë e ee. eve e e - e Software and/or Firmware Figure 2 conveys overall operational considerations, from initiation or enabling, with a check mode prefacing a detector activation and condition interpretation to generate a control message.

Figure 3B summarises encoding bit allocation to accommodate sensor or detector data range or fault conditions and gas detector reset by pump purge.

Figure 4 reflects amplification for detector output, for onward relay.

Figure 5 reflects detector module connections between sub-units.

Figure 6 reflects detector bulb connections.

Figure 7 reflects detector modem circuit detail.

Figure 8 reflects provision for detector running from a vehicle 24Volt supply with decoupling to minimise noise interference.

Figure 9 reflects a detector condition processor for data format in conformity with standard CAN protocol.

Figure 10 reflects provision for detector reset by pump purge initiation preparatory to fresh condition establishment.

Figure 11 reflects the detector sub-board circuit detail with amplification of both measurement and reference channels for signal comparison.

Figure 12 reflects detector module interconnections following a CAN protocol.

Figure 13 reflects display module processor con nections.

Figure 14 reflects display module power supply circuit detail.

Figure 15 reflects display module modem circuit detail.

Figure 16 reflects display module connections between sub-units.

ë e C . . . . ...

- Figure 17 reflects display module interconnections following a CAN protocol.

Follow-On Actions Once a person has been detected (in a cargo bay) the following actions could be triggered automatically: all doors to that area immediately locked; a digital photo taken of the trailer interior; exterior warning lamps illuminated in a particular pattern or sequence; LED lamps display a cover warning signal; an audible siren or bell activated.

Although emphasis in the foregoing example has been upon CO2 detection, wider principles of remote sensing, encoding and relay - over power cables, dedicated data lines or otherwise, can be applied to other remote detection conditions or criteria.

Similarly, features may be extracted for independent use and/or mixed and matched selectively for diverse 2 5 pu rposes.

Moreover, 'single ended' modules could be contemplated - say allowing detector and local alarm (lamp signals) for an uncoupled trailer.

Alternative Applications Any gas could be detected using the above principles of the invention.

For example, gas detection and monitoring in a refrigerated environment could be used to identify off' condition food or drink products which may be harmful if consumed.

Further, toxic or potentially hazardous material or fumes may be detected, such as exhaust, refridgeration or even hydraulic fluid leakage.

Alternatively, a similar device could be used to monitor a greenhouse environment including plant transpiration.

In a further application, a CO2 detector could be used to log CO2 emissions, say from a road vehicle, to signal (non-) compliance with prescribed standards or ee: . :::e :: ... :e:.: :: ë to categorise vehicle emissions for taxation levy.

Sub-titles or summary phrases alongside claim

numbering in the appended claims are for ease of reference and do not themselves form part of or otherwise impact upon claim scope or interpretation.

Component List 1 0 1 1 detector 1 2 microprocessor 1 3 interface 1 4 controller 15 power cable 1 6 controller 1 7 microprocessor 1 8 display 1 9 interface trailer tractor cargo bay cab

Claims (6)

A: c: . I: t ... . . e t < . Claims.

1. {Remote Condition Sensor} A remote condition sensor or detector, such as for road vehicle operation, comprising a condition sensor or detector, to produce an output signal according to condition; a microprocessor for receiving detector output; and a controller for modulating signals for a communications channel. 1 5

2. {Detector} A detector comprising: a respiratory gas sensor for monitoring gas levels in a closed environment; a controller to determine gas levels reaching a predetermined threshold; and a warning indicator, responsive to controller determination, for producing a warning of personnel occupancy of monitored environment.

3.

A detector of either preceding claim configured for a road freight vehicle, such as a truck or trailer, with a detector coupled to an indicator through a vehicle power supply.

4.

A detector of Claim 1 configured for a road freight vehicle, such as a truck or trailer, with a detector coupled to an indicator through an existing data link.

e. . . . , e se

5.

A detector of any preceding claim, with a non-dispersive infra red (NDIR) carbon dioxide detector to monitor respiratory exhalation by occupants of a vehicle (cargo hold).

6.

A detector of any preceding claim, with a driver information module to receive, process and display information transmitted by a carbon dioxide detector.

A detector of any preceding claim, with a portable driver information module deriving power and communication signals via a vehicle driver cab cigarette lighter / power outlet. 8.

A detector of any preceding claim, with a driver information module configured as factory-fitted cab OEM (Original Equipment Manufacturer). 9.

A detector of any preceding claim configured to use vehicle electrical power cables to transmit and receive data between a carbon dioxide detector module and a driver information module. 10.

A detector of any preceding claim configured for integration with a lighting control module.

A: e: ë age: . a . A detector of any preceding claim with discrete self-contained carbon dioxide detector and driver information unit, configured for a tractor and trailer combination. 12.

A detector of any preceding claim, using a communication protocol between carbon dioxide detector and driver information unit in conformity with CAN protocol modulated using ASK (Amplitude Shift Keying). 13.

A detector of any preceding claim, incorporating a detection sensitivity model for faithful respiratory CO2 determination in a closed environment the model being characterized by cargo air volume and CO2 concentration increase for a minimum single person occupancy. 14.

A detector or remote condition detection system substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings. 15.

A vehicle or cargo trailer incorporating a detector or remote condition detection system of any preceding claim. 16.

A driver information unit, configured for use with a vehicle or cargo trailer of 0 Claim 15.

ë :e::: te: *e e:e e. ce' : 17.

A remote condition sensor or detector, such as for road vehicle operation, comprising a condition sensor or detector, to produce an output signal according to condition; a microprocessor for receiving detector output; a controller for modulating signals for a communications channel; and an interface with a vehicle power supply, for supply modulation according to condition data.