SE537785C2

SE537785C2 - Sensor system based on cable with integrated sensor nodes

Info

Publication number: SE537785C2
Application number: SE1230092A
Authority: SE
Inventors: Peter Nilsson; Are Björneklett; Robert Thorslund
Original assignee: Apr Technologies Ab
Priority date: 2012-09-07
Filing date: 2012-09-07
Publication date: 2015-10-20
Also published as: SE1230092A1; WO2014039003A1

Abstract

_ :g .c sš\.\\> - ..«~.«.~._ xšš. ,////ff//1/./”.f The present invention provides a sensor network based on a cable (1) comprising integrated sensor nodes (2) with communication arrangements (3) and protective mantel (4).The end of the cable is connected to a master unit (6). The integrated sensors andcommunication electronics provides a robust long-life system being easy to install. The cable ispreferably made of two or three electrical wires (5), insulation, fillers, yarns and sheaths of apolymer or a reinforced polymer mantel (4). The sensors and communication arrangement isbased on electronic circuits and electrical read out signals and has the capability to also act as alink to detect, localize and communicate with wireless sensors. The design of and the typicalapplications for such a sensor cable (1) is described.

Description

sensor network based on a sensor cableg '...9. ...-.4..ﬂ.... v There is in many situations a need for monitoring physical parameters such as temperature overa long distance. Some examples are fire detection in tunnels, pipelines or high power electrical cables. Other applications are large area monitoring of waste storage or biofuel storage.

Fire is a frequently occurring problem in bio fuel process and storage sites. Such fires aredifficult to predict and notice in an early stage, gﬁgigthey can go on for weeks or even monthsbeforebeging i-tuis-noticed. They may spread out of control and generally imply high cost forfirefighting as well as the loss of the fuel itself. The surroundings are typically affected by odor and harmful smoke.) Cable sensors have been in use for more than 40 years. The first applications were fire detectionin tunnels. Other applications are fire detection in petrochemical plants and pipelines. Earlyadoptions of the technique utilized for example a polymer material that would melt and shortcircuit cables at a specific temperature. The short circuit point could be localized thus providingthe position of the area of elevated temperature. High sensitivity calorimeters are used as wellas opto-cables based on laser sensing technologies. Digital electronic communications havebeen introduced later. However in general more than two parallel wires are needed in thecable. Separate wires for power supply, data transmission and addressing which sensor tocollect data from.

There are manually handled systems available on the rnarket but what really is needed is aninstallation of a robust and automatic system with long lifetime, and not disturhing the dailywork going on at the plant.

The prior art has drawbacks with regards to being able to provide robustness, reliability, longlife time, combined wired and wireless sensors and being an easy-to-install solution for sensorsystem.

The object of the present invention is to overcome the drawbacks of the prior art. This isachieved by the communication arrangement in each sensor node, low power consumption andthe positioning of sensor cable in combination with capability to include wireless sensors.Thanks to the invention it is possible to obtain a permanent installation with long life time,suitable for storage of solid waste and solid bio fuel.

The present invention relates to a sensor network based on a sensor cable containing a largenumber of sensors integrated in the cable, as well as communicating with wireless sensorsoutsibie the cable.

A suitable technology for such monitoring is the cable sensor. At many positions along the cablethere are embedded sensor elements which measure the tentperature or other physicalparameters. The sensor elements transmit the data on the cable to a master unit located at oneor both ends of the cable. The tvoicai length of the cable is from a few meters up to ntanvkilometers. The number sensor elemerrts are uo to several tiunolreds. in a network of rriuitipleternoerature serisrßrs, they are with advantage placed both in the ground and ernbedded in thewaste fuel in the forrn of wireless sensor nodes. 'fhese provide early information aboutiricreasecïi fire hazard as well as information on how the fire soreads.

Thanks to the invention it is possible to monitor fire ignitions, micro biological activities andgases. lt is a further advantage of the invention to provide §_solution to detect and monitor pollutionfrom landfill sites, analysis of leachate water as well as concentrations of greenhouse gases anddust. lt is a yet further advantage that the same main unit can talk with both cable sensors as well aswireless sensors being distributed in _a_pile. lt also enables a simple way to localize the wirelesssensors as well as ithelps overcome the damping of wireless signals caused by the solidmaterials being stored. ln a second aspect, the two or three wire cable enables a cost effective manufacturing of cablewith integrated sensor nodes. ln addition, the invention helps overcome difficulties with sensor integration for users comingfrom agriculture, landfill, wood chip plies, pellets storage, solid waste storage, conveyor belts,cable tunnels, silos, traffic tunnels, oil and off-shore industry.

Other object, advantages and novel features of the invention will become apparent from thefollowing detailed description of the invention when considered in conjunction with theaccompanying drawings and claims.

Briiefdescri tion of the drawiin 's Preferred ernbodirnezits of the invention will now be described with reference to the accompanying drawings, wherein: Fig l is a schernatic illustration of a sensor cable cornorising a rnain unit, cable and sensor nodes.according to the invention; Fig 2 is a schernatic illustration of the »wired sensor node according to the invention; and Fie 3 is a schematic illustration of a sensor system comprising embedded sensor cable and wireiess sensor riodes according to the invention.

The cable is a two-wired or three-wired cable and in most cases it is a ruggedized cable foremployment in harsh environmental conditions. Each sensor part in our invention consists of asmall sized electronics module being integrated in the cable. The sensor node includes a smallmicroprocessor, analog-to-digital conversion and tlieä sensing element. ln the case oftemperature measurement the sensing element is typically a temperature sensitive resistor. Thesystem has two-way data communication between the master unit and the sensor elements incable, by means of voltage shift of the voltage between the wires.

Each sensor element module is powered by current drawn from the cable. Since the number ofsensor elements can be in the order of many hundreds, the current drawn by each of the sensorelement modules is low.

The sensor node (2) typically contains FET transistor (7), resistor (8) together with anuelectricalcircuit (9) of _a__micro-processor, gunmanalog-digital converter, amsensor element, wiredcommunication, aunmantenna and wireless communication. The FET transistor (7) sensegincoming data triggered by voltage change between the cable wires (5). The load resistor (8) isused for transmitting wired data onto the cable by pulling down the voltage between the cable wires.

Sensor elements are built on different technologies and gfguoften commercially available. LiggSgame type or a multiple type of sensors are integrated in the one or more cables. The transienthot strip method is used to measure thermal properties of surrounded materials. få,'fi-temperature dependent resistor is used to measure changes in temperature other than what isnormal.

The sensor cable can interact with wireless sensor nodes (9) and localize them individually, asthey are positioned inside a storage pile of easily ignitable material (10) which can be but is notlimited to waste materials, biofuel or dust. The sensor cable is typically embedded on ground(12) under the pile (10) in a foundation material (11). The foundation material can be but is notlimited to asphalt, gravel, concrete, cement, soil or grass.

The cable sensors nodes (2) and/or wireless sensor nodes (9) located at distances from 0.1 to 10meter from cable, can detect temperature, moisture, chemicals and thermal properties insurroundings. Chemicals are typically methane, carbon oxides, nitrogen oxides, oxygen, smokeand water. The sensor element include sensors to measure chemical concentrations, gasconcentrations of for example oxygen, carbon oxides and methane, moistu re levelgﬁ ln one embodiment, the system is connected to §_main unit and _a__mobile modem, andcommunicating to ga__mobile phone and/or the ilnternet. ln one embodiment, a sensor system for storage, based on cables with integrated sensor nodesalso able to communicate with wireless sensor nodes. The sensor cable is localized close to thematerial to be stored, typically embedded in the ground surface, on a sidewall and/or in theroof. lt contains several integrated sensor nodes with the advantage of having capability to alsoact as the link to further detect, localize and communicate with wireless sensors, to be includedin the system. This forms a large sensor network with sensors both integrated in cable andrandomly positioned in the larger surroundings to the cable. The wireless sensor nodes isautomatically detected and localized. ln one embodiment, the sensor cable has a large number of parallel connected integratedsensor nodes. lt uses two-way data communication between the master unit and the integratedsensor nodes by means of voltage shift of the voltage between the wires. The powerconsumption, the data rate and the update frequency are all very low.

According to embodiments, the sensor cable has the advantage of dual use and can also act todetect, monitor and localize wireless sensors in the surroundings.

According to embodiments, the sensor cable has one or more sensor nodes molded in polymeror reinforced polymer¿ According to embodiments, the sensor cable is installed embedded in solid ignitable material¿According to embodiments, the sensor cable has only three electrical wires to the main unit.According to embodiments, the sensor cable is used to monitor fire ignitions: According to embodiments, the sensor cable is used to monitor micro biological activities;According to embodiments, the sensor cable is used to monitor gases; According to embodiments, the sensor cable is used to monitor concentrations of green housegasesà According to embodiments, the sensor cable is used to detect and monitor pollution fromlandfill sites¿ According to embodiments, the sensor cable is used for chemical analysis of leachate water;According to embodiments, the sensor cable is powered by solar cells; According to embodiments , a large number of wireless sensor nodes are positioned andleft/kept in stored material during its life time, it will actually to be stored at different locationsand the sensors follow the material all the way to final destination that typically is combustion.

Claims

Claims:

1. A sensor system for a_storage, basedcomprising enat least one cablee with integrated sensor nodes; wherein each integrated sensor node comprises a communication arrangement, therebybeing cagableeapabi-l-i-w to also-act as the link to fu-Ft-heßdetect, iocalize andcommunicate with wireless sensors, -t-e-beincluded in the system;

2. A sensor system according to claim 1, where a_large number of wireless sensor nodes arepositioned and left/kept in stored material during its life time._,

3. A sensor eablesystem according to claim 1 or 2, withwherein the at least one cable hasonly Z-tvviowires connected to a multiple of sensors;

4. A sensor system according to any of the preceding claims-L-å, connected to a_main unitand a_mobi|e modem, and communicating teïh _a_mobile phone and/orﬂejlnternet.

5. A sensor ealalesystem according to any of the preceding claims-lë, the at least one cablereading signals from wireless sensor nodes connected to solar cells;

6. A sensor eablesystem according to any of the preceding claimg-L, wherein the at leastone cable has avvith maximum gåmrgg wires, being parallel connected to a multiple ofsensors;

7. A sensor ealalesystem according to any of the preceding claims-l-S, with a_multiple ofsensor types in _th_esame at least one cable;

8. A sensor eablesystem according to any of the preceding claims, the at least one cablewithcomprising a multiple of chemical sensors;

9. A sensor eablesystem according to any of the preceding claims,_-the at least one cable wi-thcomprising chemical sensors for concentrations of oxygen and carbon oxides_._

10. A sensor eablesystem according to any of the preceding claims, the at least one cablecomprising with-a multiple of moisture level detectors;

11. A sensor cable-system according to any of the preceding claims, the at least one cable comgrising with-one or more transient hot strip sensors;

12. A sensor c-ablesystem according to any of the preceding claims, the at least one cablecomprising uæi-th-a_sensor element module comprising a microprocessor with currentconsumption 1-100 uA¿

13. A sensor eable-system according to any of the preceding claims, the at least one cablecomprising vvit-h-no transformers or inductive components needed for thea datacommunication to §_master unit.

14. A sensor eablesystem according to any of the preceding claims, the at least one cablecomgrising wi-t-h-a_typical data transmission rate between 10 to 1000 bit/s.

15. A sensor eablesystem according to any of the preceding claims, the at least one cableMtb-having a length from 10 to 10000 meters;

16. A sensor eable-system according to any of the preceding claims, the at least one cablecomgrising with-more than one integrated sensor node being protected with at least,but not limited to, polymer and metal.

17. A sensor eablesystem according to any of the preceding claims, the at least one cableblgpmbedded in thíeground under g_pile of solid bio fuels or waste material;