Fire-prevention thermographic system

Abstract

A fire-prevention thermographic system is provided, said system comprising: a thermal imaging camera, a control unit, a temperature reference unit comprising a reference thermal element and a contact temperature sensor. The thermal imaging camera and the temperature reference unit are operationally connected to the control unit and both installed in an environment to be monitored. The contact temperature sensor is configured to provide the control unit with a reference temperature of the reference thermal element. The control unit is configured to adjust a temperature provided by the thermal imaging camera in the environment to be monitored on the basis of the reference temperature.

Description

[0001] DESCRIPTION

[0002] “Fire-prevention thermographic system” * * * * * * * * * * * * *

[0003] FIELD OF THE INVENTION

[0004] The present invention relates to the field of fire-prevention thermographic systems for detecting the formation of fires in open or closed environments such as (but not exclusively) yards, warehouses and storage premises. More particularly, the present invention relates to a fire-prevention thermographic system comprising one or more thermal imaging cameras and a method for detecting an anomalous temperature and preventing the formation of a fire.

[0005] PRIOR ART

[0006] Thermography is a non-destructive analysis technique which involves, as is the known, the detection of the temperature distribution on the surface of a body obtained by defining, by means of particular instruments, the infrared radiation emitted by it and the acquisition of images which represent the temperature distribution detected. Thermography is used for checking the heat insulation in buildings, conduits, etc., and also for locating “hot spots” (defects) in electric and electronic circuits, in the non-destructive testing of articles, and in the medical sector for diagnosing pathologies which result in a lack of homogeneity in the surface temperature distribution. The instrument used for thermographic investigation work is the thermal imaging camera, which detects the infrared radiation emitted by the body being examined.

[0007] For applications in industry and in particular in security applications, thermography may be used to monitor remotely a certain environment, but also to detect a fire and even detect in advance a fire (in particular, the ignition source), namely to predict the outbreak of a fire and activate means suitable for preventing the formation thereof. In other words, the advanced detection of the fire allows counter-measures to be taken so as to prevent the outbreak of said fire.

[0008] At present on the market there are present thermographic systems which use one or more thermal imaging cameras for video surveillance applications and thermographic systems which use one or more thermal imaging cameras for fire-prevention applications. In video surveillance systems, in particular, thermal imaging cameras are typically provided with, installed therein, a processing software which is able to provide images of the environment monitored in terms of temperature distribution, in order to detect any anomalies which might produce a heat gradient.

[0009] SUMMARY OF THE INVENTION

[0010] The inventors have noted that the abovementioned thermographic systems present on the market may not be very accurate and reliable because of various factors.

[0011] The first factor, which typically relates to thermographic systems for video surveillance, is the possible generation of false alarms. False alarms are due to the fact that the known instruments often are unable to distinguish between the actual ignition sources, to be detected as the start of a fire, and hot elements such as, in an industrial environment, the exhaust pipes of operating vehicles which are present in the field of vision of the thermal imaging camera.

[0012] Moreover, in the known systems used also for fire-prevention operations, the reading of the temperature provided by the thermal imaging cameras is influenced by various variable elements, such as the emissivity of the objects to be monitored (namely their capacity to emit infrared radiation), the radiation resulting from the surrounding environment which is reflected by the objects themselves (also called reflected ambient temperature), the transmittance of the objects, the atmospheric temperature and the response of the components of the thermal imaging camera. Typically, each thermal imaging camera has specific accuracy characteristics, for example ±5°C, provided by the manufacturer, but the temperature reading may be subject to errors.

[0013] Finally, the known thermographic systems, in particular in fireprevention applications, presuppose the setting of threshold temperatures for providing a warning (in the form, for example, of alarms and / or pre-alarms), resulting in the activation of fire-prevention counter-measures when said temperatures are exceeded. Typically, the threshold temperatures are set to fixed values which allow counter-measures to be activated only when a very high temperature, for example 230°C (corresponding, for example, to the self-ignition temperature of paper), is exceeded. This, however, does not allow the detection of ignition sources which are activated for example during the nighttime, when the ambient temperature is lower, because the temperature, at the start of the fire, does not reach the preset temperature.

[0014] The Applicant has defined the aim of providing a thermographic system for the prevention of fires, referred to also a fire-prevention thermographic system, which is more precise and reliable than the known systems and which, in particular, is able to reduce the reading errors of the thermal imaging camera, and also of improving the performance of the thermographic system in terms of prior detection of a possible fire. The Applicant has also defined the aim of providing a method for detecting an anomalous temperature by means of the thermographic system in question and preventing the formation of a fire.

[0015] According to the present invention, the fire-prevention thermographic system comprises at least one thermal imaging camera, a control unit and at least one temperature reference unit. Operation of the system involves measuring one or more reference temperatures, comprising preferably a reference ambient temperature, by means of one or more contact measurements provided by the temperature reference unit (or by the temperature reference units, if the system comprises more than one of them) so that at least one of these measurements, which is precise and reliable, allows real-time adjustment of the temperature value provided by the thermal imaging camera, in a contactless manner, and the correction of any errors. According to embodiments of the present invention, the reference ambient temperature measurement is used to determine one or more threshold temperatures for the possible warning signal. In this way, the threshold temperatures may vary dynamically, namely they may be automatically set to adapt to the temporal progression of the ambient temperature, and therefore allow more efficient warning that is actually in advance of a potential fire. Differently from known systems which employ dynamic calibration of the thermal imaging camera by using external thermal reference systems (so- called “blackbodies”), the system according to the present invention is based therefore on the compensation of any error in the temperature value provided by the thermal imaging camera. The calibration of a thermal imaging camera, as is known, is a process which is performed off-line and which requires specially equipped laboratories and optimum temperature and emissivity conditions. Typically, these conditions cannot be reproduced in real plants, resulting in the calibration process being impractical or unreliable if performed in a working context. The compensation-based system which is employed in the system according to the present invention instead allows simplification of the hardware architecture and a substantial reduction in the operational complexity, eliminating the need for additional components which are subject to deviations, faults or maintenance. Compensation of the error may therefore be performed in the field during the measurement of the temperature itself. Moreover, compensation of the error may be adapted to take into account environmental, optical and temporal factors, ensuring thermal measurements which are reliable and stable over time, also in difficult conditions or in industrial environments subject to variability. The compensation-based approach, finally, ensures more rapid processing of the data, resulting in greater reactivity and operative continuity.

[0016] As is known, a thermal imaging camera comprises a sensor consisting of a matrix of detection elements or pixels, each of which is able to detect electromagnetic infrared radiation (IR) striking it and emit a corresponding electric signal indicating the temperature.

[0017] In the present description and the claims, the expression “temperature provided by the thermal imaging camera” relating to a region of interest in the environment to be monitored or, generally, “temperature of the region of interest”, will indicate the temperature of a region of the field of vision of the thermal imaging camera, said temperature being processed on the basis of the temperatures corresponding to the signals emitted by the pixel(s) which cover(s) the region considered (for example, said temperature corresponds to the average value of the temperatures provided by the single pixels).

[0018] In the present description and the claims, the expression “ambient temperature” will indicate the temperature of the location in which the at least one thermal imaging camera of the fire-prevention thermographic system is positioned.

[0019] Finally, in the present description and the claims, the expression “anomalous temperature” indicates a temperature which is above a threshold temperature (for example an alarm threshold temperature) or is within the range comprised between two different threshold temperatures (for example, between a pre-alarm threshold temperature and an alarm threshold temperature).

[0020] According to a first aspect of the present invention, a fire-prevention thermographic system is provided, the system comprising: a thermal imaging camera; a control unit; a temperature reference unit comprising a reference thermal element and a contact temperature sensor; wherein the thermal imaging camera and the temperature reference unit are operationally connected to the control unit and both installed in an environment to be monitored, wherein the contact temperature sensor is configured to provide the control unit with a reference temperature of the reference thermal element, wherein the control unit is configured to adjust a temperature provided by the thermal imaging camera in the environment to be monitored on the basis of the reference temperature.

[0021] Preferably, the contact temperature sensor is configured to provide the control unit with a reference ambient temperature of the reference thermal element and wherein the control unit is configured to compare the temperature provided by the thermal imaging camera with a threshold temperature determined by the control unit as a function of the reference ambient temperature.

[0022] Preferably, the control unit is configured to: receive from the contact temperature sensor of the temperature reference unit the reference temperature; and calculate a correction coefficient as the difference between the reference temperature and a temperature provided by the thermal imaging camera in a reference region of interest occupied by the reference thermal element.

[0023] Preferably, the control unit is configured to: receive from the thermal imaging camera a temperature of a region of interest of the environment to be monitored; and adjust the temperature of the region of interest by adding to it the correction coefficient.

[0024] Preferably, the control unit is configured to determine the threshold temperature by adding a predefined constant temperature component to the reference ambient temperature.

[0025] Preferably, the reference thermal element is an element which is present in the environment to be monitored and which reaches a given operating temperature.

[0026] According to some embodiments of the system according to the present invention, the reference thermal element is a passive device with known emissivity, such as a dissipator device made of black anodized aluminium.

[0027] According to some embodiments of the system according to the present invention, the contact temperature sensor is a thermocouple.

[0028] According to some embodiments of the system according to the present invention, the contact temperature sensor is a PT1000, PT500 or PT100 probe.

[0029] According to a second aspect of the present invention, a method for detecting an anomalous temperature in an environment to be monitored by means of the fire-prevention thermographic system described above is provided, the method comprising, at the control unit: a) receiving from the contact temperature sensor the reference ambient temperature of the reference thermal element, b) adjusting a temperature provided by the thermal imaging camera in the environment to be monitored on the basis of the reference ambient temperature; c) determining a threshold temperature as a function of the reference ambient temperature; d) comparing the temperature provided by the thermal imaging camera and adjusted on the basis of the reference ambient temperature with the threshold temperature; and e) if the temperature provided by the thermal imaging camera and adjusted on the basis of the reference ambient temperature exceeds the threshold temperature, generating an anomaly signal.

[0030] BRIEF DESCRIPTION OF THE FIGURES

[0031] The present invention will become clearer from the following detailed description, provided purely by way of a non-limiting example, to be read with reference to the accompanying figures in which:

[0032] Figure 1 schematically shows a fire-prevention thermographic system according to embodiments of the present invention; and

[0033] Figure 2 is a flow diagram of a method for detecting an anomalous temperature by means of the system shown schematically in Figure 1 .

[0034] DETAILED DESCRIPTION

[0035] Figure 1 is a block diagram illustrating a fire-prevention thermographic system 1 according to example embodiments of the present invention. The fire-prevention thermographic system 1 is in particular suitable for detecting an anomalous temperature and for preventing the formation of fires in open or closed environments such as (but not exclusively) yards, warehouses and storage premises. In particular, the fire-prevention thermographic system may be used to prevent fires in yards or storage premises designed to store and / or treat waste or in yards or storage premises designed to store combustible materials.

[0036] In the continuation of the present description and in the claims, the expression “fire-prevention thermographic system” may also be replaced by the expression “system”, “fire-prevention system” or other similar shorter expressions. The system 1 according to the present invention comprises one or more thermal imaging cameras 11 and a control unit 12 configured to process the data provided by the one or more thermal imaging cameras 11 and to detect any anomalous situations, as will be described in greater detail below.

[0037] In particular, the example system schematically shown in Figure 1 comprises only one thermal imaging camera 11. The thermal imaging camera 11 is installed in the environment to be monitored. The thermal imaging camera 11 is for example a thermal imaging camera of the known commercially available type. For example, the system according to the present invention may comprise a FLIR Series A thermal imaging camera manufactured by Teledyne FLIR LLC, for example a FLIR A50 or FLIR A70 thermal imaging camera. As already mentioned above, the thermal imaging camera comprises a sensor consisting of a matrix of detection elements or pixels, each of which is able to detect electromagnetic infrared radiation (IR) striking it and to emit a corresponding electric signal indicating the temperature. For example, in the case of the thermal imaging cameras mentioned above, the detection elements are microbolometers.

[0038] In the example of the system 1 , the thermal imaging camera 11 is preferably connected to a thermographic processing module 13 via a switch 14 for example. The thermographic processing module 13 preferably comprises one or more electronic boards configured to process the data provided by the thermal imaging camera 11 and provide thermographic images indicating the temperature distribution within the field of vision of the thermal imaging camera 11. Such a processing system is known and will therefore not be described in greater detail in the continuation of the present description. By means of the switch 14, the thermographic processing module 13 is connected to the control unit 12 and provides this unit with the thermographic images.

[0039] The control unit 12 is, for example, a PC equipped with a processing and control software application for processing the data acquired by the one or more thermal imaging cameras 11 and for detecting any anomalous situations, outputting corresponding anomaly signals (for example, video and / or audio signals). The control unit 10 may be equipped with a display, a loudspeaker and an input / output unit such as a keyboard and / or a touchpad.

[0040] According to embodiments of the present invention, the aforementioned application is a web server application and the control unit 12 is the server on which said application is run. With these types of application, an operator may access the data and the thermographic images provided by the application and interact with the application itself, inputting or outputting information via the Internet (i.e. by connecting up to a web page), by means of a device such as a PC or a portable device such as a tablet or a smartphone.

[0041] The control unit 12 is preferably connected, via the switch 14, to an actuation module 15. The actuation module 15 is in turn connected to at least one temperature reference unit 16 which comprises a reference thermal element and a contact temperature sensor. The actuation module 15 may be connected to a fire-prevention central unit 17 (which does not form part of the system according to the present invention). The actuation module 15 is configured to receive, at its input, the signals emitted by the control unit and to provide the fire-prevention central unit 17 with any actuation signals which allow the activation, if necessary, of measures for counteracting the fire by means of suitable fire signalling apparatus (for example, sirens, luminous panels, etc.) and / or fire-extinguishing apparatus (for example, sprinklers). The actuation module 15 is also configured to receive at its input the signal output from the contact temperature sensor of the temperature reference unit 16 and to provide the corresponding temperature value to the control unit 12.

[0042] The actuation module 15 may be a programmable logic controller (PLC) or a contact board. It is configured to make available, normally by means of the closing / opening of electrical contacts, actuation signals based on the anomaly signals provided by the control unit 12.

[0043] The control unit 12, the thermographic processing module 13, the switch 14 and the actuation module 15 of the system according to the present invention are preferably in a location remote from the environment to be monitored. According to the embodiments of the present invention schematically shown in Figure 1 , the system comprises a single temperature reference unit 16. The temperature reference unit 16 preferably comprises an element which is at a reference temperature (said element will be referred to as “reference thermal element”) and a contact temperature sensor of the reference thermal element. The reference thermal element is, according to preferred embodiments of the present invention, a passive device with a known emissivity, which is positioned in the environment to be monitored and is at the ambient temperature. It may be for example a dissipator device (referred to as a “plate”) made of black anodized aluminium. Aluminium has a high thermal conductivity, which means that the device rapidly transfers heat and “responds” rapidly to the variations in temperature of the surrounding environment, assuming a uniform surface temperature. As a result of this aspect, this type of device is particularly reliable as a temperature reference element. The black anodization on the surface of the dissipator device increases its thermal emissivity (>0.95). The black finish absorbs and radiates heat more efficiently than other finishes, allowing the element to reach rapidly the temperature equilibrium with the surrounding environment. Moreover, the anodization creates a protective layer on the surface of the aluminium, making it more resistant to corrosion. This is particularly important in the case where the dissipator device is exposed to adverse or wet environmental conditions. The dissipator device may have, for example, a surface area of about 50 x 50 mm or more depending on the geometric resolution (for example clusters of 3 x 3 pixels).

[0044] The temperature sensor may comprise a thermocouple (TC) or thermistor. The temperature sensor may be, for example, a type K thermocouple, which is typically able to measure the temperature in an extremely wide range, from about -200°C to about +1300°C. Alternatively, the temperature sensor may be a PT1000, PT500 or PT100 probe namely a RTD sensor (Resistance Temperature Detector) made of platinum (Pt) with a nominal resistance of 100Q (or 500Q or 1000Q) at the temperature of 0°C. This sensor, as is known, makes use of the capacity of a material to vary its electrical resistance with a variation in the temperature. This type of sensor is typically able to measure the temperature within the range of about -200°C to about 600°C with a precision of up to + / - 0.1 °C.

[0045] The sensor, as mentioned, provides a contact measurement of the temperature of the reference thermal element. Since this measurement is a contact measurement, the value measured is very precise and reliable. For example, a probe of the PT100 type in the precision class B typically has, as is known, a tolerance of + / - 0.3 °C at 0°C, + / - 0.8°C at 100°C and + / - 1.3°C at 200°C.

[0046] In the continuation of the present description, the reference number 16 will indicate both the temperature reference unit as a whole and the temperature sensor present in it.

[0047] According to some embodiments of the present invention, the temperature reference unit 16 provides a reference ambient temperature used by the system both to adjust or correct the temperature provided by the thermal imaging camera and to vary dynamically one or more threshold temperatures, as will be described in greater detail below.

[0048] According to other embodiments of the present invention, the reference thermal element may be an element already present in the environment to be monitored, for example associated with a machine or a portion of a machine, or the like, which reaches a given operating temperature which is measured by the contact temperature sensor and used as a reference temperature for correcting the temperature provided by the thermal imaging camera.

[0049] According to yet other embodiments of the present invention, the system comprises several temperature reference units, for example comprising a reference thermal element at ambient temperature which provides a reference ambient temperature and a further reference thermal element at a different temperature which provides the reference temperature used by the system to correct the temperature provided by the thermal imaging camera.

[0050] All the connections shown in Figure 1 between the components of the system according to the present invention may be wired connections or wireless connections. The connection between the temperature reference unit 16, in particular the contact temperature sensor, and the actuation module 15 may be a wireless connection and the data exchange may be based on the known LoRa (Long Range) communication protocol. The connection between the control unit 12 and the actuation module 15 may be a wired connection and the data exchange may be based on the known Modbus communication protocol.

[0051] Figure 2 is a flow diagram which illustrates a method for detecting an anomalous temperature in the environment considered and therefore for preventing the formation of a possible fire. The method is implemented by the control unit 12 and comprises processing the data provided by each thermal imaging camera and providing any signals in the presence of an anomaly, according to example embodiment of the present invention. The method implemented by the control unit 12 comprises an algorithm for analysis of the data provided by the thermal imaging camera which per se does not form the subject of the present invention and which therefore will not be described in particular detail. Said algorithm preferably involves processing of the data of the thermal imaging cameras so as to provide the temperature read by the thermal imaging camera in a number of regions of interest (also called ROi - Region Of Interest) within the field of vision of the thermal imaging camera. Each region of interest within the field of vision of the thermal imaging camera corresponds to a given zone of the environment to be monitored which is recorded by the thermal imaging camera and which can be set, for example, by a user via the software application of the control unit 12. These regions are typically represented by rectangles, circles or, more generally, polygons. Each region corresponds to the combination of the instantaneous fields of vision of a certain number of pixels.

[0052] For each region of interest, the analysis algorithm provides for performing a comparison of the temperature provided by the thermal imaging camera with one or more threshold temperatures and the detection, within each region of interest considered, of the possible presence of an object with an anomalous temperature. Moreover, the algorithm may involve an analysis of the form and the position (and any possible variations thereof over time) of the object with an anomalous temperature. Finally, the algorithm performs the generation of an anomaly signal when certain conditions arise. For example, the algorithm may envisage a single alarm threshold temperature or an alarm threshold temperature and a pre-alarm threshold temperature lower than the alarm threshold temperature.

[0053] Merely by way of a non-limiting example, below reference will be made to an algorithm which provides a comparison between the temperature provided by the thermal imaging camera and a single alarm threshold temperature and the possible generation of an anomaly signal when this alarm threshold temperature is exceeded.

[0054] Moreover, also merely by way of a non-limiting example, the embodiments of the present invention which envisage the use of a single temperature reference unit which provides a reference ambient temperature will be described.

[0055] Upon start-up of the system, the thermal imaging camera 11 and the temperature reference unit 16 are preferably installed in the environment to be monitored. The reference thermal element is at the ambient temperature. As already mentioned above, the reference thermal element identifies a spatial region, inside the environment to be monitored, occupied by a passive device with a known emissivity which provides a reference ambient temperature reference, as will be described below. The contact temperature sensor of the temperature reference unit 16 then measures the temperature of this device.

[0056] According to embodiments of the present invention, after the start of the procedure for monitoring the considered environment, when operation of the system 1 is activated, the thermal imaging camera 11 records the environment to be monitored in such a way that its field of vision comprises the reference thermal element. The thermal imaging camera 11 then provides the data acquired to the thermographic processing module 13 which processes said data (using algorithms known in the thermography field) and provides corresponding thermographic images transmitted to the control unit 12. The control unit 12 preferably processes the data of each thermographic image and provides the temperature values read by the thermal imaging camera 11 in a number M of regions of interest within the field of vision of the thermal imaging camera, as will be described below. According to the present invention, the number M of regions of interest comprises a reference region of interest corresponding to a region of interest occupied by the reference thermal element.

[0057] In particular, steps 201 -27 of the method shown in the flow diagram of Figure 2 are preferably repeated with a frequency corresponding to the acquisition frequency of the thermal imaging camera 11 , i.e. the frequency of acquisition of the flow of thermographic images (for example, 30 Hz). During operation, the thermal imaging camera 11 records the environment to be monitored and provides the temperature data corresponding to the signals emitted by the pixels for the number M of regions of interest comprising the reference region of interest (indicated also by the abbreviation “RR” in the flow diagram of Figure 2) occupied by the reference thermal element of the temperature reference unit 16.

[0058] The method, according to embodiments of the present invention considered here, involves a first step 201 during which reading of the temperature of the reference region of interest RR is performed.

[0059] In particular, step 201 is composed of two sub-steps 201 a and 201 b:

[0060] - during the sub-step 201a, the control unit 12 processes the temperature values provided by the pixels of the thermal imaging camera 11 in the reference region of interest RR occupied by the reference thermal element, namely the values provided by the pixels TRp(i), i=1 , ... , N, N being the number of pixels of the thermal imaging camera 11 which cover the reference thermal element 16 and calculates the average value TRM thereof, which represents the temperature provided by the thermal imaging camera in the reference region of interest RR;

[0061] - during the sub-step 201 b, the control unit 12 preferably receives from the temperature sensor of the temperature reference unit 16 the reference ambient temperature value acquired said sensor TR. In particular, in the system shown schematically by way of example in Figure 1 , the data acquired by the temperature sensor 16 is provided to the control unit 12 via the actuation module 15 which converts the signal provided by the sensor 16 into temperature data.

[0062] During the following step 202, the control unit 12 preferably processes the data received and calculates a temperature correction coefficient as the difference DT between the temperature acquired by the sensor 16 and the temperature provided by the thermal imaging camera for the reference region of interest RR, i.e.:

[0063] DT=TR-TRM .

[0064] This difference, if different from zero, indicates a reading error of the thermal imaging camera 11 , i.e. indicates that the temperature provided by the thermal imaging camera 11 at the reference element is different from the temperature measured by the temperature sensor 16. The error will therefore be used, according to the present invention, to adjust the temperature. For example, if the reference ambient temperature TR detected by the sensor is 32°C, while the temperature TRM provided by the thermal imaging camera is 30°C, the correction coefficient is equal to 2°C. On the other hand, if the reference ambient temperature TR detected by the sensor is 30°C, while the temperature TRM provided by the thermal imaging camera is 33°C, the correction coefficient is equal to -3°C.

[0065] At the end of this step, therefore, the control unit 12 preferably stores the correction coefficient DT and the reference ambient temperature TR.

[0066] During step 203, reading of the temperature of a region of interest RT, comprising for example a specific object which may prove to be a potential ignition source, is performed. In particular, during step 203, the control unit 12 processes the temperature values provided by the pixels of the thermal imaging camera 11 in the region of interest RT. The values provided by the thermal imaging camera 11 are the temperature values of the pixels which cover the region of interest RT considered. In particular, during step 203, the control unit 12 processes the values provided by the pixels of the thermal imaging camera 11 in order to determine the average temperature value TM of the region of interest RT, namely the temperature provided by the thermal imaging camera 11 in this region.

[0067] At the control unit 12, during step 204, the temperature value TM provided by the thermal imaging camera 11 is then updated by adding to it the correction coefficient DT. The control unit 12 then provides an updated (or corrected) temperature TM’ of the region of interest RT by means of the following calculation:

[0068] TM' =TM+DT .

[0069] In this way, it is possible to correct any reading error of the thermal imaging camera, thereby improving the reading accuracy of the instrument.

[0070] It should be noted that this process corresponds to a compensation of the error in the temperature value provided by the thermal imaging camera and not to a calibration of the thermal imaging camera itself. As already mentioned above, in fact, the system according to the present invention may operate correcting the error in the temperature value provided by the thermal imaging camera in the field and does not involve any (offline) calibration of the thermal imaging camera itself. Advantageously, compensation of the error may be adapted to take into account environmental, optical and temporal factors, ensuring thermal measurements which are reliable and stable over time, also in difficult conditions or industrial environments subject to variability. Moreover, it ensures more rapid processing of the data, resulting in greater reactivity and operative continuity.

[0071] During step 205, the control unit 12 preferably determines the alarm threshold temperature Th associated with the region of interest considered RT. In particular, the control unit 12 preferably determines the alarm threshold temperature Th depending on the reference ambient temperature TR measured by the sensor 16 and stored in the control unit itself. For example, according to embodiments of the present invention, the threshold temperature Th may be determined from the ambient temperature TR by adding to this value a constant temperature component TF, which may be preset, for example, equal to 30°C. The threshold alarm temperature Th may therefore be determined in the following manner:

[0072] Th=TR+TF.

[0073] According to embodiments of the present invention, step 205 may be performed offline compared to the procedure for acquisition of data by the thermal imaging camera for the region of interest RT (steps 203 and 204). In particular, step 205 may be repeatedly periodically during the operation of the system 1 so as to monitor the variation over time of the ambient temperature TR with a repetition frequency less than the data acquisition frequency of the thermal imaging camera 11. This results in savings in terms of computational resources.

[0074] In step 206, the value of the temperature TM’ of the region of interest RT provided by the thermal imaging camera 11 and updated by means of the correction coefficient DT is compared with the alarm threshold temperature Th. If the temperature value TM’ exceeds the alarm threshold temperature Th, the control unit 12 preferably generates an anomaly signal and forwards it to the actuation module 15 (step 207). At the same time, the control unit 12 may also store the thermographic image where the temperature above the threshold in the monitored environment was detected, for future analyses.

[0075] If the temperature TM’ does not exceed the alarm threshold temperature Th, the method continues with the analysis of the data relating to the next acquisition performed by the thermal imaging camera 11 .

[0076] In the case where there are more than one region of interest in the field of vision of the thermal imaging camera 11 , the sequence of steps 203-207 is preferably repeated for each region of interest. For each thermographic image considered, processing, by the control unit 12, of the data relating to the different regions of interest is more or less simultaneous.

[0077] The procedure described above advantageously allows adjustment of the temperature provided by the thermal imaging camera in each region of interest in a precise and reliable manner. Moreover, it allows calculation of the threshold temperature as a function of an ambient temperature variable over 24 hours; the threshold temperature is therefore adapted in a dynamic and automatic manner depending on the ambient temperature and this enables the potential ignition sources in the monitored environment to be recognized in advance, this resulting in time being gained for activation of the counter-measures. Said counter-measures, if activated in advance, may be activated to a reduced extent compared to a situation in which the ignition source is recognized with a delay and has therefore already caused damage, with obvious savings in terms of resources and costs. For example, let us assume that, over 24 hours, the ambient temperature may vary between -5°C and 30°C. Assuming a constant temperature component TF of 30°C for calculation of the alarm threshold temperature Th, according to the example procedure described above, the method envisages that the alarm threshold temperature Th may vary between 35°C and 60°C, allowing potential ignition sources in any ambient condition to be recognized in advance.

[0078] As mentioned above, during step 207, the control unit 12 preferably generates an anomaly signal. This signal may, for example, generate a video message for the user on the device which the user uses in order to interact with the software application mentioned above (for example in the case of a web server application, the portable device with which user connects to the server). The anomaly signal is preferably forwarded to the actuation module 15 which in turn may forward a corresponding actuation signal to the fireprevention central unit 17. The fire-prevention central unit 17 may at this point implement one or more counter-measures, namely may implement them by means of suitable fire-signalling apparatus (for example sirens, luminous panels, etc.) and / or fire-extinguishing apparatus (for example, sprinklers).

Claims

CLAIMS1 . A fire prevention thermographic system comprising:- a thermal imaging camera (11 );- a control unit (12);- a temperature reference unit (16) comprising a reference thermal element and a contact temperature sensor, said reference thermal element being a passive device with known emissivity; wherein said thermal imaging camera (11 ) and said temperature reference unit (16) are operationally connected to said control unit (12) and both installed in an environment to be monitored, wherein said contact temperature sensor is configured to provide said control unit (12) with a reference ambient temperature of said reference thermal element, wherein said control unit (12) is configured to:- adjust a temperature provided by said thermal imaging camera (11 ) in said environment to be monitored on the basis of said reference ambient temperature;- compare said temperature provided by the thermal imaging camera (11 ) and adjusted on the basis of said reference ambient temperature with a threshold temperature determined by said control unit (12) as a function of said reference ambient temperature; and- if said temperature provided by said thermal imaging camera (11 ) and adjusted on the basis of said reference ambient temperature exceeds said threshold temperature, generate an anomaly signal.

2. The fire prevention thermographic system according to claim 1 , wherein said control unit (12) is configured to:- receive from said contact temperature sensor of said temperature reference unit (16) said reference ambient temperature; and- calculate a correction coefficient as the difference between said reference ambient temperature and a temperature provided by the thermal imaging camera (11 ) in a reference region of interest occupied by said reference thermal element.

3. The fire prevention thermographic system according to claim 2, wherein said control unit (12) is configured to:- receive from the thermal imaging camera (11 ) a temperature of a region of interest of said environment to be monitored; and- adjust said temperature of said region of interest by adding to it said correction coefficient.

4. The fire prevention thermographic system according to any one of claims 1 to 3, wherein said control unit (12) is configured to determine said threshold temperature by adding a predefined constant temperature component to said reference ambient temperature.

5. The fire prevention thermographic system according to any one of the preceding claims, wherein said contact temperature sensor is a thermocouple.

6. The fire prevention thermographic system according to any one of claims 1 to 4, wherein said contact temperature sensor is a PT1000, PT500 or PT100 probe.

7. A method for detecting an anomalous temperature in an environment to be monitored using the fire prevention thermographic system according to claim 1 , said method comprising, at said control unit (12): a) receiving from said contact temperature sensor said reference ambient temperature of said reference thermal element, b) adjusting a temperature provided by said thermal imaging camera (11 ) in said environment to be monitored on the basis of said reference ambient temperature; c) determining a threshold temperature as a function of said reference ambient temperature; d) comparing said temperature provided by said thermal imaging camera (11 ) and adjusted on the basis of said reference ambient temperature with said threshold temperature; and e) if said temperature provided by said thermal imaging camera (11 ) and adjusted on the basis of said reference ambient temperature exceedssaid threshold temperature, generating an anomaly signal.

Images