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FIELD OF THE INVENTION

The present invention relates in general to systems for remote monitoring of the integrity of infrastructures distributed over the territory and more precisely a monitoring system that integrates technologies for monitoring structural integrity, obtained through a network of sensors of various types applied to the individual infrastructure, with wireless network- transmission technologies.

The invention proposed has the purpose of supplying a series of data and reports regarding the state of structural integrity of an infrastructure to the user who is responsible therefor. The main added value of this solution is that of providing the user with data of primary importance for assessing the structural state of the infrastructure without the need for an in-depth and costly inspection of the site.

Today, many companies have at their disposal and use a wide range of distributed infrastructures as element of primary importance for their business.

Companies of this sort base their business on proper functionality of their assets: a problem, damage, or else failure in one or more of these systems would create for the firm multiple economic harm, linked to the costs necessary for restoring the damaged structure, the costs regarding possible damage produced to third parties or goods of third parties, and finally to the possible loss of income connected with interruption of the service provided (distribution of electric power, diffusion of television signals, etc.).

In order to limit as far as possible the likelihood of there arising damage to the structures, the companies program campaigns of inspection during which teams of technicians carry out a series of inspections, either visual or using adequate instrumentation. Such inspections have the aim of assessing the conditions of the infrastructures in order to program possible maintenance interventions for restoring the damage possibly identified during these campaigns.

The above type of approach presents a series of intrinsic disadvantages.

The first disadvantage of this sort of methodologies of inspection lies in the fact that, precisely on account of their nature of "distributed assets", the infrastructures to be inspected are, to a large extent, installed in places that are isolated and not easy to access: it will suffice to consider masts for television broadcasting, which, in order to broadcast the signal over areas that are as wide as possible, are situated on mountain tops or hill tops far from built-up areas.

This condition means that the team of inspectors has to travel in order to reach the place where the structure to be monitored is located and carry out the necessary inspections. Inspections of this sort are expensive from an economic standpoint and a standpoint of commitment of resources.

The second disadvantage is due to the fact that this type of inspection campaign makes it possible to assess the conditions of the asset only after the inspections have been carried out. It is hence not possible for the owner/manager of the infrastructures to have information regarding the structural conditions between two successive inspections. This problem becomes all the more marked, the longer the time interval between two successive inspections.

The impossibility of having available information on the conditions of the structure in the absence of interventions of inspection proves critical when an exceptional event presents. For example, following upon extreme meteorological events (whirlwinds or powerful storms) that have subjected the structures to very intense loads, it may be very important to have an updated evaluation of the structural conditions. It will thus be necessary to plan urgent interventions of inspection, with consequent increase in costs.

Finally, even in the absence of particular conditions, planning of the inspection campaigns must pursue the target of guaranteeing integrity of the infrastructures with the maximum likelihood, endeavouring at the same time to contain the costs of the inspections. This planning is carried out on a statistical basis, taking into consideration a series of parameters of the infrastructures (age, geographical location, type of loads to which it is subject, and other parameters that depend upon the infrastructures themselves and upon their use). This type of planning consequently does not take into account the real conditions of the structure or the history of the loads to which it has been subjected. The result of this methodology is consequently the possibility that an intervention of inspection, planned without having available the necessary information, will prove useless a posteriori, since the infrastructure undergoing inspection is in conditions such as not to require any kind of maintenance intervention.

To overcome this type of problems, and to render the interventions of inspection and maintenance more efficient both from a standpoint of costs and from the standpoint of timing, it is of fundamental importance to have available a system that will be able to evaluate and transmit remotely information regarding the critical parameters of the structures.

Some attempts to overcome the problems so far described are disclosed, for example, in the documents Nos. US 2005/131652, WO 02/06764, and WO 2009/063523.

One of the differences between the present invention and the technical solutions described in the above documents lies in the fact that an algorithm is provided for detection of false positives for the alarms generated on the basis of meteorological events. As will emerge more clearly from what follows, the present invention is also able to establish directly or indirectly the presence of ice or snow on the structure, through detection of the temperature, pressure, and humidity of the air, via sensors present in situ and preferably through a connection with an external weather-forecasting service. It should be noted, in fact, that the presence of ice and snow adds temporary weight on the structure that it being monitored, and this entails modification of the vibrational "signature" of the structure itself. In the solutions described in the known art, this modification would be detected as a damage alarm since an increase in the weight of a structure, at the vibrational level, has the same effect as a reduction in its stiffness (i.e., in the presence of damage): there is a reduction in the value of the natural vibrational frequencies of the structure. Given that ice and snow do not constitute a danger for the structure (except in extreme cases), it is not to be considered as damage, and for this reason - unlike the known art - the present invention is able to exclude these situations of false positives.

It should be noted that the technical solution described in the document No. WO 2009/063523 is based upon a self-learning algorithm, but these meteorological events cannot be considered in self-learning in so far as they are not to be counted as events that repeat cyclically, as instead may be seasonal variations in temperature that affect expansion of the materials. In other words, seasonal variation of temperature can be self-learnt by the system described in WO 2009/063523, whereas the presence of ice or snow cannot since it is caused by complex meteorological phenomena.

Another difference between the present invention and known systems is based upon detection of the intensity and direction of the wind. A satellite georeferencing system (e.g., GPS, which is usually installed in the top part of the structure to have a better reception of the satellite signal) supplies to the system the possible displacement of the structure with respect to its nominal conditions. The presence of wind may cause the structure to shift and generate a false positive in an alarm. Also in this case, which is new, wind constitutes a meteorological event that is difficult to foresee and hence may be difficult to be self-learned by a system like the one described in WO 2009/063523. According to the present invention, moreover, the information regarding the intensity and direction of the wind can be compared with the displacement detected by the geolocator, thus excluding a damage event or else, on the contrary, predicting an imminent collapse of the structure in the case of excessive intensity.

Moreover forming an essential condition is the fact that this system should be able to acquire data in a completely autonomous way and that the data acquired locally on the individual infrastructure be transferred to a processing centre after they have been received, collected, and processed in a centre for management of the data of the individual infrastructure.

All these results have been achieved by the present invention by envisaging a remote data-acquisition system that integrates technologies for monitoring the integrity of structures, such as for example masts, obtained through a network of sensors of various types installed on the infrastructure to be monitored using wireless network-transmission technologies, where the network has the task of collecting the key parameters thereof and information on the surrounding environment.

In a preferred embodiment, the configuration of the sensor network, for each infrastructure monitored, consists of:

A) one or more structural nodes that have the task of acquiring and collecting:

1 . the vibrational response of the infrastructure to external stimuli;

2. the data regarding the environmental parameters of the site of interest that can affect the structural behaviour, such as atmospheric temperature, barometric pressure, humidity, speed and direction of the wind; and

3. other monitoring data, for example chemical monitoring data; and

B) a main node, which is the central element of the network.

The main node collects the data transmitted by the other sensor nodes and operates as bridge for communication and control between them and the remote station.

Each main node is constituted by one or more of the following components:

a) a transceiver system comprising:

a 2.4-GHz radio transceiver unit; and

an interface between the transceiver unit and the microprocessor card;

b) a microprocessor card comprising:

a microprocessor unit with operating system and software with data-processing algorithm; and

a nonvolatile memory

c) a gateway for network connection:

via Ethernet; and

via GPRS

d) a power-supply system comprising:

an external power-supply system, or else a solar and/or wind power generator;

a charge-regulation circuit; and

energy-storage batteries.

The sensor network has the following functions/features:

- implementation of pre-set processes and/or remote-control implementation of on-demand processes;

- setting-up of telecommunication connections;

- use of wireless technology;

- use of self-supply systems; and

- operation in any meteorological condition.

The sensors installed on the structure are governed by microprocessor electronic control devices.

These devices are made up of a hardware part and a software part. The systems of the hardware part comprise: controller/computer card, data buses, wired/wireless interfaces, digital-to-analog converters, nonvolatile external-storage devices, interface with telecommunication terminal.

The software part is made up of a firmware, an operating system, a control-and-planning software, and a data-management software. These devices are electronic systems with ultra-low-power technology. They have available an autonomous power-supply system, with stand-by batteries and an energy-harvesting system, through the use of solar panels or other devices for generating electrical energy, for recharging them, so that the network of sensor nodes will be able to acquire the data in a completely autonomous way.

Advantageously, the data-processing station is modular in such a way as to be able to manage multiple infrastructures. It consists of a hardware and software system and is provided with appropriate standard interfaces that enable integration with other technological systems.

The data acquired by the nodes are transmitted via wireless connection (using, for example, the 2.4-GHz standard) to the central node. This node has the task of carrying out a preliminary processing and filtering of the data.

From the central node, the information is transferred to the remote station in which a processing system is present (installed, for example, at the user's control centre), which has the task of:

- saving the data acquired in order to create a historic of the measurements made;

- executing processing of these data in order to generate parameters and other information useful for the owner of the infrastructure monitored;

- supplying a user interface for displaying the useful parameters on the screen;

- enabling operators, via the user interface, to navigate within the historic database and display the trends of the parameters selected; and - displaying alerts and (possibly) alarms in the case where the information processed were to overstep pre-determined thresholds. Further characteristics and advantages of the present invention will emerge clearly from the ensuing detailed description, with reference to the attached plates of drawing, which represent a preferred embodiment thereof merely by way of non-limiting example.

In the plates of drawings:

Figure 1 shows a structural node, self-supplied with a solar panel;

Figure 2 shows a piezoelectric sensor installed on the structure of a mast by being glued thereon;

Figure 3 shows the data acquired by a structural node and transferred to the processing centre;

Figure 4 shows processing of the time-history with a Fast Fourier Transform to obtain the first vibration frequencies of the structure;

Figure 5 shows the flowchart for generation of an alert for the user;

Figure 6 is a block diagram of a structural node with the various specific sensors;

Figure 7 is a block diagram of the main node with the various components;

Figure 8 is a diagram provided by way of example of the complete system, which represents two masts, located on each of which are a number of structural nodes, each structural node of a mast being directly connected to a main node positioned on the mast itself or in a housing in the proximity thereof, each main node being autonomously connected to the central monitoring station; and

Figure 9 shows the block diagram of the microcontroller card of a structural node.

With reference to the figures, the monitoring device forming the subject of the invention comprises at least two apparatuses, one of which is mainly designed for detection of the structural datum and is referred to as "structural node" (Figure 1 ) and the other is designed for reception of said datum from the structural node, for its processing, and retransmission to the user according to an appropriate protocol. This node is referred to as "main node" (Figure 7).

By "structural datum" is meant a series of information useful for definition of the state of a structure, such as: measurements of deformation, acceleration, displacement, meteorological measurements of temperature, pressure, humidity of the surrounding air, speed and direction of the wind.

The structural nodes, designated by NS, may be multiple and may be located, as emerges from Figure 8, in different points on the structure in question 10. They communicate in radio mode with the main node NP that collects the data received.

Each structural node NS, as may be seen in Figure 6, is constituted by one or more of the following components:

1 . a plurality of sensors, such as:

o one or more piezoelectric sensors SPZ, designed for supplying a local measurement of the deformation;

o one or more accelerometers SAC, designed for supplying a local measurement of the acceleration;

o one or more satellite position detectors GPS, designed for supplying a local measurement of the position and hence of the displacement;

o one or more temperature sensors ST for detecting the temperature of the surrounding air;

o one or more pressure sensors SP for detecting the pressure of the surrounding air; and

o one or more sensors for measuring the speed and direction of the wind SA in the surrounding environment.

Possibly provided are other sensors (not illustrated in the figure), such as:

o one or more humidity sensors for detecting the humidity of the surrounding air; and

o one or more chemical sensors (for example, for detecting corrosion).

2. a microcontroller card MCU.

3. a transceiver system comprising:

o a 2.4-GHz radio transceiver unit TX/RX; and

o a radio antenna RA.

4. a power-supply system comprising:

o a solar power generator GS and/or wind power generator GE;

o a charge-regulator circuit RG; and

o rechargeable energy-storage batteries BR; and finally

5. a box 14 (as may be seen in Figure 1 ) for protecting the electronics, made of metal for shielding from electromagnetic waves and from atmospheric agents.

All the sensors are appropriately connected to the microcontroller card of the structural node NS through shielded cables 16.

As may be seen in Figure 9, the microcontroller card comprises: o a system of voltage dividers PT for rendering uniform the voltage of the analog electrical input signals coming from the sensors;

o one or more analog-to-digital converters CA/D;

o one or more interfaces for digital data with input ports USART SPI

TWI and output ports UR to the radio;

o nonvolatile flash memories M2, and EEPROMs M3;

o a volatile SRAM MV;

o a microcontroller unit CPU with processing software;

o a unit GA for managing the state of hibernation/state of activity to reduce to a minimum electric power consumption, said unit being made up of oscillator/clock-generator circuits CO, an oscillator OW, and a watchdog timer TW;

o a power-supply supervision unit SAL; and

o a data bus BD. In its service life, the structure 10 to be monitored, under the action of external loads, for example wind, and/or internal loads, for example due to motors, vibrates according to natural frequencies. These vibrations of the structure are detected by the piezoelectric sensors, fixed via gluing to the structure itself (Figure 2), and/or by accelerometers through a transduction of mechanical energy into electrical voltage signals. These signals, if they are of an analog type, are scaled by an appropriate system of voltage dividers and sent to an analog-to-digital converter. The microcontroller MCU manages the digital signals, sending them to a nonvolatile memory M and transmitting them, at pre-set time intervals or upon request, to the main node NP via the radio transceiver unit TX/RX.

As may be seen in Figure 7, each main node NP is constituted by one or more of the following components:

• a transceiver system comprising:

o a 2.4-GHz radio transceiver unit; and

o an interface between the transceiver unit and the microprocessor card;

• a microprocessor card comprising:

o a microprocessor unit with operating system and software with data-processing algorithm; and

o a nonvolatile memory;

• a gateway for network connection:

o via Ethernet; and

o via GPRS; and

· a power-supply system comprising:

o an external power-supply system; or else

o a solar and/or wind power generator;

o a charge-regulator circuit; and

o rechargeable energy-storage batteries.

The main node NP receives, through its radio transceiver unit, and gathers all the data supplied by the structural nodes NS, stores them in a nonvolatile memory MP, and re-transmits them at pre-set time intervals or upon request to a user terminal located in the proximity of the structure or remotely, said user terminal being referred to as "remote station SC" (Figure 8). The latter transmission may be carried out with various modalities: Ethernet, satellite transmission, GPRS transmission, radio transmission.

The remote station SC is a data-processing system that has the task of:

• saving the data acquired in order to create a historic of the measurements made;

• processing these data in order to generate parameters and other information useful for the owner of the infrastructure monitored;

• providing a user interface for displaying the useful parameters on the screen;

· enabling operators, via the user interface, to navigate the historic database and display the trends of the parameters selected; and

• displaying alerts and (possibly) alarms in the case where the information processed were to overstep pre-determined thresholds.

Illustrated in Figure 3 is an example of data acquired by a structural node NS and transferred to the main node NP for a first processing and filtering of the data.

The data-processing software uses a Fast Fourier Transform for converting the piezoelectric and/or accelerometric signal from the time domain to the frequency domain (Figure 4). The conversion is used for detecting the vibrational-frequency resonance peaks of the signal. These resonance frequencies represent the structural signature of the structure that is being monitored.

When these values move away from the nominal situation, it means that there has occurred a change in the structure, such as a variation of stiffness and/or of weight. These variations are considered as a signal of onset or presence of structural damage, and consequently an alarm is activated for the operator.

The environmental data detected by the specific sensors have the purpose of purging the structural datum from possible effects due to the environment, such as increase in weight and stiffness due to snow or ice, deformations due to variations in temperature, displacements due to wind intensity. In the latter case, the datum on the direction and intensity of the wind enables the operator to monitor the loads of the wind on the structure and evaluate the correlations between these loads and the response of the structure itself: an excessive response to a given wind load can trigger an alarm.

The satellite position datum serves to indicate a possible disruption of the territory, such as for example a phenomenon of landslide or subsidence that could jeopardise stability of the structure.

The algorithm with which the data are aggregated to generate a system of alerts for the user is illustrated in Figure 5.

As may be seen, represented schematically is a structural node NS that substantially comprises four types of sensors:

a structural sensor of a piezoelectric type, designed to supply a dynamic-deformation signal;

a sensor for measuring the speed and direction of the wind

(anemometer); and

a set of environmental sensors, designed for measuring the temperature, atmospheric pressure, and relative humidity of the surrounding air.

The signals at output from the aforesaid sensors are transmitted via wireless connection to the central node, where a first processing and filtering thereof is carried out.

In particular, it is highlighted how:

the displacement of the position detected by the sensor GPS activates a subsidence alarm;

the simultaneous presence of a signal of displacement of the modal frequencies of the structure with respect to the nominal frequencies and of the presence of ice or snow detected by the environmental sensors activates a snow/ice-alarm signal;

a signal of displacement of the modal frequencies of the structure with respect to the nominal frequencies in the absence of a signal indicating the presence of ice or snow activates a damage-alarm signal.

The maximum value of deformation extrapolated from the dynamic- deformation signal coming from the piezoelectric sensor is compared with the previously established threshold value of the maximum deformation caused by the wind: if the difference is found to fall outside the range of tolerance, a damage alarm is activated.

The wind speed detected by the anemometer is compared with a threshold value: if this speed exceeds the acceptable threshold value a damage alarm is activated.

In any case, signals are created alerting exceeding of thresholds of all the parameters measured and the positive or negative variation of the fundamental vibrational frequency within certain percentage values.

Advantages

With the present invention it is possible to achieve a series of significant advantages.

The first is inherent in the inspections that it is necessary to carry out on the infrastructures, which at the moment are in general costly, problematical, and not frequent, thus giving rise to information that is only temporally defined. The invention enables continuous monitoring in remote conditions, reducing the cost of ordinary maintenance, which would become on-condition on the basis of detection of damage.

The second advantage is that the invention makes it possible to determine the effects that could occur, to the infrastructure, in the presence of extraordinary events, whether natural or not, known or not (for example, atmospheric events, geological events, landslides, flooding, wilful damage). The third advantage is that the invention also exploits piezoelectric sensors, which supply a direct local measurement of the deformation of the structure and an indirect measurement of the state of stress unlike traditional accelerometric sensors, which supply only a local measurement of the acceleration. This leads in many cases, in particular for structures of great height, such as towers for television transmissions or pylons of high- tension power lines, to major advantages in terms of ease of installation. In fact, piezoelectric vibration sensors (piezoelectric chips) that enable measurement of the deformation have to be located, in order to increase the quality of measurement, in the position where the structural deformation is maximum (typically at the base of structures of great height), whereas accelerometers, since they measure the maximum accelerations, must be located in the positions of maximum acceleration, typically for the structures referred to above, at their tops, with evident difficulties of installation.