DESCRIPTION

TECHNICAL FIELD

The present invention refers to the sensor sector. In more detail, the present invention concerns an antivibration support comprising an integrated sensor, a vibration measuring system comprising said support and an operating machine comprising said support or integrating the entire mechanical stress measuring system.

BACKGROUND

Operating machines, such as chiller units and fans - e.g. of HVAC systems -, pumps, electric motors, CNC systems, presses, grinding machines, etc., are typically supported on the ground by the use of antivibration supports and/or feet that serve to isolate these machines and ensure that they do not transmit vibrations to the ground.

These devices typically comprise a supporting portion of the machine and a support portion opposite each other along a main direction, transverse to the support surface in use. A layer or an elastic element is placed between these portions so that the operating machine is free to oscillate with respect to the support surface, while remaining bound thereto.

In addition, the vibrations produced by an operating machine are indicative of an operation state of the machine itself. The analysis of the amplitude and/or of the course over time of the vibrations produced by the operating machine makes it possible to identify malfunctioning conditions, anomalous operating conditions and/or, more generally, to discriminate among different operation conditions of the operating machine.

It is known in the art to couple transducers to the support or to the antivibration foot that convert the vibrations transmitted to the support or to the antivibration foot by the operating machine into electrical signals, in order to analyse the operation of the operating machine and identify anomalous operation conditions.

In addition, the measure ment and the analysis of the vibrations generated by the operating machine are typically carried out on a sample basis and/or periodically by maintenance technicians. Consequently, this control procedure does not allow malfunctions or, more generally, anomalous operation conditions of the operating machine to be detected in a timely manner. In addition, the monitoring operation is quite costly in terms of time and human resources. In fact, for each operating machine to be monitored it is necessary to install and, where necessary, calibrate at least one acquisition device before being able to carry out the measurements, to carry out the desired measurements and to remove the acquisition device.

In addition, the same mechanical stresses measured by the sensors may cause a reduction in the service life of electronic and/or electro-mechanical elements used to realize these sensors, for example if the levels are higher than the capacity of the instrument.

KR 101835467 concerns a pump with a self-diagnostic function. The pump comprises a plurality of sensors installed directly or indirectly in the pump housing for measuring vibrations and a system control device that is mounted on one side of the pump housing for diagnosing an anomaly through comparison of a value detected by the sensors with a reference value.

KR 101835467 describes a vibration measuring system affected by the disadvantages described above.

WO 2000/14476 proposes a displacement sensor, which can be used to measure vibrations, comprising a pair of nanometrically sized elongated conductors. These conductors are integrated into respective insulating elements so that they remain facing one surface of the respective insulating element. The conductors are then arranged facing one another and parallel to each other, but separated by a separation space comprised between 2 and 50 Armstrong. Subsequently, a potential difference is applied between the two conductors and an electric current flowing between the conductors due to the tunnelling effect is measured. The intensity of the current varies as a function of the distance between the two conductors.

The solution proposed in WO 2000/14476 is particularly complex to realize. In particular, the nanometric and sub-nanometric distances that characterise the structure of the sensor make it necessary to use extremely precise, complex and expensive machinery and technology in order to realize a properly functioning sensor. In addition, the sensor thus produced is particularly delicate and unsuitable for hostile environments and/or particularly intense mechanical stresses. Finally, the tolerances intrinsic in the industrial production processes lead to a high variability in sensitivity among sensors, requiring ad hoc calibration procedures for each sensor.

OBJECTS AND SUMMARY OF THE INVENTION

An object of the present invention is to overcome the drawbacks of the prior art.

In particular, an object of the present invention is to provide an antivibration support for operating machines capable of effectively reducing the transmission of mechanical stresses, in particular vibrations produced by the operating machine, while integrating a robust and reliable sensor that allows performing an accurate measurement of said mechanical stresses.

Furthermore, an object of the present invention is to provide a robust mechanical stress monitoring system capable of measuring the mechanical stresses to which an operating machine is subjected in a precise and accurate manner.

A further object of the present invention is to provide a mechanical stress monitoring system provided with an antivibration support for operating machines capable of effectively reducing the transmission of mechanical stresses, in particular vibrations produced by the operating machine, while integrating a robust and reliable sensor that allows performing an accurate measurement of said mechanical stresses.

These and other objects of the present invention are achieved by a system incorporating the features of the annexed claims, which form an integral part of the present description.

According to a first aspect, the present invention is directed to an antivibration support for an operating machine comprising: first coupling means configured to couple the support to an operating machine, second coupling means configured to couple the support to a support surface or an element lying on a support surface, an elastic portion placed between the first coupling means and the second coupling means, wherein the elastic portion comprises a polymeric material and is configured to reduce a transmission of mechanical stresses between the operating machine and the support surface, and a sensor assembly configured to provide a signal which is a function of the mechanical stresses to which the support is subjected.

Advantageously, said elastic portion comprises a plurality of carbon molecular structures. Furthermore, the sensor assembly comprises said elastic portion and a pair of electrically conducting elements connected to the elastic portion. In particular, the elastic portion is configured to compress and expand along said main direction when subjected to vibrations, thereby varying an electrical resistance of the elastic portion at least along said main direction.

Preferably, although not limited to, the electrically conducting elements are connected to respective surfaces of the elastic portion opposite each other along a main direction of extension of the support.

Thanks to this solution, the antivibration support is suitable, at the same time, for reducing the transmission of the mechanical vibrations to which the support is subjected - in particular the vibrations produced by the operating machine during operation - and allow to reliably measure the amplitude of these oscillations. Varying the resistivity - or more generally the impedance - of the elastic portion of the support as a function of the intensity of the stresses experienced by the support makes it possible to obtain a particularly simple and accurate measurement of these mechanical stresses with a compact and robust structure of the support. In addition, the support is particularly simple and inexpensive to produce.

In one embodiment, the carbon molecular structures of the plurality of carbon molecular structures are generally in a mass fraction comprised between 0.1 % and 10% of the total weight of the elastic portion.

The Applicant has determined that this density ratio allows to obtain optimal results in terms of probability of tunneling effect and, consequently, of sensitivity to mechanical stresses without altering the elastic characteristics of the polymeric material of the elastic portion.

Preferably, the carbon molecular structures of the plurality of carbon molecular structures are selected from graphene, fullerene and graphite.

In one embodiment, the molecular structures of the plurality of carbon molecular structures comprise graphene nano-platelets.

Preferably, the graphene nano-platelets have a thickness comprised between 2 nm and 20 nm, preferably comprised between 5 nm and 10nm and a lateral dimension comprised between 5 p m and 50 p m, preferably comprised between 15 p m and 30 p m, for example equal to 25 p m. In another embodiment, the molecular structures of the plurality of carbon molecular structures comprise nanotubes in single or multiple wall configuration.

Preferably, the carbon nanotubes have a diameter comprised between 5 nm and 20 nm, preferably comprised between 5 nmand 15 nm, for example equal to 10 nm, and a length comprised between 1 p m and 10 p m, preferably comprised between 2 p m and 5 p m.

The Applicant has determined that such dimensions of the selected carbon molecular structures ensure optimal performance in terms of probability of electrical conduction due to the tunneling effect in the case of graphene nano-platelets and carbon nanotubes.

In one embodiment, the elastic portion comprises natural rubber and the nanotubes in single or multiple wall configuration are in a mass fraction comprised between 1 % and 8 %, preferably 4 %, of the total weight of the elastic portion.

The Applicant has determined that this composition of the elastic portion of the support provides optimal performance in terms of measurement sensitivity of the same without compromising the elastic properties of the material used to make the elastic portion.

A different aspect of the present invention concerns a system for monitoring mechanical stresses - vibrations produced by the operating machine - capable of providing reliable information on the amplitude and/or the course over time of the mechanical stresses experienced by at least one antivibration support according to one of the embodiments described above - coupled to an operating machine.

In particular, the present invention is directed to a mechanical stress monitoring system comprising antivibration support for an operating machine and a control device. The antivibration support comprises: first coupling means configured to couple the support to an operating machine, second coupling means configured to couple the support to a support surface or an element lying on a support surface, an elastic portion placed between the first coupling means and the second coupling means, wherein the elastic portion comprises a polymeric material and is configured to reduce a transmission of mechanical stresses between the operating machine and the support surface, and a sensor assembly configured to provide a signal which is a function of the mechanical stresses to which the support is subjected.

The control device comprises a measuring unit connected to the sensor assembly and a processing unit connected to the measuring unit.

Advantageously, said elastic portion comprises a plurality of carbon molecular structures. Furthermore, the sensor assembly comprises said elastic portion and a pair of electrically conducting elements connected to the elastic portion. In particular, the elastic portion is configured to compress and expand along said main direction when subjected to vibrations, thereby varying an electrical resistance of the elastic portion at least along said main direction. Furthermore, the control device measures a voltage proportional to a value of the electrical resistance of the elastic portion and determines an intensity of the mechanical stresses to which the antivibration support is subjected based on said value of the electrical resistance.

Thanks to this solution, the system is simple and does not require the use of conditioning circuits (for example Wheatstone Bridge with low-pass filter and demodulator) as in the case of capacitive sensors. This makes it possible to obtain robust measuring systems, with reduced complexity and cost.

In one embodiment, the measuring unit generates a direct or alternating electric current or voltage between the pair of electrically conducting elements and measures a corresponding voltage or current, respectively, across said pair of conductive elements. This measured voltage or current has a value which is a function of the electrical resistance of the elastic portion.

Further, the antivibration support may comprise the features of any of the embodiments described above.

Preferably, the measuring unit samples the voltage across the pair of electrically conducting elements or the current flowing between the pair of electrically conducting elements and calculates an effective value of the voltage across the pair of electrically conducting elements or an effective value of the current flowing between the pair of electrically conducting elements. The effective voltage or effective current value is indicative of the electrical resistance of the elastic portion.

Even more preferably, the measuring unit samples the voltage across the pair of electrically conducting elements or the current flowing between the pair of electrically conducting elements for a sampling period inversely proportional to a maximum allowable frequency of the mechanical stresses.

Such a monitoring system is particularly simple and inexpensive to realize, but at the same time capable of reliably monitoring, preferably in real time, the intensity of the mechanical stresses.

In one embodiment, the processing unit is configured to detect a mechanical stress with intensity equal to or greater than a predetermined value and, in this case, to generate an alarm signal denoting an anomalous operation condition of the operating machine.

Advantageously, the predetermined value, used as a threshold for identifying anomalous mechanical stresses, is selected so as to minimize false positives and therefore the emission of unnecessary alarms. This can be obtained empirically starting from the analysis of the operating characteristics of the system in which the antivibration supports are integrated.

In addition or alternatively, the processing unit is configured to generate and transmit to the operating machine a stop signal when a mechanical stress with intensity equal to or greater than the predetermined value is detected, the stop signal forcing the operating machine to stop.

The monitoring system according to the invention makes it possible to identify anomalous operation conditions or malfunctions of an operating machine to which one or more supports are connected and to report this event to an operator - both human and informative - in a timely manner and/or to interrupt the operation of the operating machine to prevent or limit damage to it. In one embodiment, the processing unit detects a mechanical stress with intensity equal to or greater than the predetermined value, when the effective voltage or the effective current calculated by the measuring unit is equal to, or greater than, a threshold value.

Alternatively, the processing unit detects a mechanical stress with intensity equal to or greater than the predetermined value, when the effective voltage or the effective current calculated by the measuring unit is equal to, or greater than, a threshold value for a predetermined period of time.

A further object of the present invention is to present an operating machine that integrates one or more supports according to the embodiments of the present invention and connected to, or integrating, the measuring unit and/or the processing unit of said mechanical stress monitoring system.

Further features and advantages of the present invention will be more evident from the description of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described hereinbelow with reference to certain examples provided by way of nonlimiting example and illustrated in the accompanying drawings. These drawings illustrate different aspects and embodiments of the present invention and reference numerals illustrating structures, components, materials and/or similar elements in different drawings are indicated by similar reference numerals, where appropriate.

Figure 1 is a schematic axonometric view of an antivibration support according to an embodiment of the present invention;

Figure 2 is a schematic front view of an operating machine fixed to the ground by means of antivibration supports according to an embodiment of the present invention;

Figure 3A is a schematic sectional side view of the antivibration support of figure 1 in a resting condition;

Figure 3B is an enlargement of an elastic portion of the antivibration support of figure 3A in which molecular carbon structures diffused in a polymer are highlighted;

Figure 4A is a schematic sectional side view of the antivibration support of figure 1 subjected to a compressive force;

Figure 4B is an enlargement of an elastic portion of the antivibration support of figure 4A in which molecular carbon structures diffused in the polymer are highlighted;

Figure 5 is a schematic representation of a vibration measuring system according to an embodiment of the present invention, and

Figure 6 is a flowchart of a vibration monitoring procedure implemented by the system of figure 5.

DETAILED DESCRIPTION OF THE INVENTION

While the invention is susceptible to various modifications and alternative constructions, certain preferred embodiments are shown in the drawings and are described hereinbelow in detail. It must in any case be understood that there is no intention to limit the invention to the specific embodiment illustrated, but, on the contrary, the invention intends covering all the modifications, alternative and equivalent constructions that fall within the scope of the invention as defined in the claims.

The use of Tor example”, “etc.”, “or” indicates non-exclusive alternatives without limitation, unless otherwise indicated. The use of “includes” means Includes, but not limited to” unless otherwise indicated.

With reference to Figure 1 , an antivibration support, more briefly support 1 hereinbelow, according to an embodiment of the present invention comprises a supporting portion 10, a support portion 20 and an elastic portion 30. In detail, the elastic portion 30 is placed between the supporting portion 10 and the support portion 20 along a main direction P of development of the support 1.

In the example considered, the support 1 comprises a first screw 41 fixed to the supporting portion 10 and a second screw fixed to the support portion 20 and protruding in opposite directions from each other and to the elastic portion 30 along the main direction P of the support 1.

Typically, the first screw 41 is used for fixing the support 1 to an operating machine 2, schematically illustrated in figure 2, at a base of the operating machine 2, whereas the second screw 42 is used for fixing the support 1 to a receiving element 3, preferably, in turn fixed to a support surface S (the ground, for example) so as to constrain the operating machine 2 to the ground by means of the support 1.

In other words, the supporting portion 10 and the first screw 41 form first coupling means configured to couple the support 1 to an operating machine, whereas the support portion 20 and the second screw 42 form second coupling means configured to couple the support 1 to the support surface S or an element lying on a support surface S.

The support 1 according to the embodiments of the present invention comprises a sensor assembly 50 configured to provide a signal proportional to the amplitude of the mechanical stresses, in particular vibrations, to which the support 1 in use is subjected, as best appreciated in Figures 3A and 3B.

In detail, the sensor assembly 50 comprises a pair of electrical contacts 51 and 52 electrically connected to opposite surfaces of the elastic portion 30 along the main direction P. Preferably, each electrical contact 51 and 52 is in direct contact with a respective surface of the elastic portion 30. In addition, the sensor assembly 50 comprises the elastic portion 30. In detail, the elastic portion 30 is formed in a polymeric element loaded with a plurality of carbon molecular structures 31.

In the present invention, the expression ‘carbon molecular structure’ refers to a substance in an allotropic state of carbon such as graphene - for example nano-platelets -, fullerenes, graphite, etc. For example, in one embodiment of the present invention, the elastic portion 30 is loaded with carbon nanotubes - i.e. fullerenes in a tubular configuration. In particular, the nanotubes may be in single or multiple wall configuration.

Preferably, the carbon molecular structures 31 have a diameter comprised between 5 nm and 20 nm, preferably comprised between 5 nm and 15 nm, for example equal to 10 nm, and a length comprised between 1 p m and 10 p m, preferably comprised between 2 p m and 5 p m, in the case of nanotubes or a thickness comprised between 2 nm and 20 nm, preferably comprised between 5 nm and 10nm and a lateral dimension comprised between 5 p m and 50 p m, preferably between 15 p m and 30 p m, for example equal to 25 p m in the case of graphene nano-platelets.

In the embodiments of the present invention, the elastic portion 30 is made of a polymer loaded with carbon molecular structures, wherein the carbon molecular structures 31 substantially correspond to a mass fraction - also indicated by the expression “weight percentage" - comprised between 0.1 % and 10% of the total weight of the elastic portion 30. Generally, the concentration of carbon molecular structures 31 is maintained below the electrical percolation threshold associated with the particular material chosen for the elastic portion 30 and with the particular carbon molecular structures 31 used.

For example, in one embodiment the elastic portion 30 is made of natural rubber and comprises an amount of carbon nanotubes comprised between 1 % and 8%, preferably 4 %, of the weight of the elastic portion 30.

Other embodiments envisage using a synthetic polymeric material commonly used in the production of antivibration supports loaded with carbon molecular structures 31 in a proportion comprised between 0.1% and 10% of the weight of the elastic portion 30. Examples of, but not limited to, usable synthetic rubbers comprise, but are not limited to, rubbers based on ethylenepropylene diene monomers (orEPDM), nitrile rubber (NBR - Nitrile Butadiene Rubber), fluorinated elastomer-based rubbers (FKM, e.g. the family of rubbers under the trade name VITON), polychloroprene -based rubbers (e.g. the family of rubbers under the trade name NEOPRENE), polymer-based rubbers obtained by polyethylene sulfochlorination (e.g. the family of rubbers under the trade name HYPALON).

Preferably, although not limited to, the elastic portion 30 is made by dispersing the carbon molecules in the polymeric base material as homogeneously as possible, for example by means of ultrasonic calendering and sonication techniques, avoiding the formation of carbon agglomerates in the solution before and/or during the subsequent curing step.

The carbon molecular structures 31 in the elastic portion 30 allow a flow of electrons between the electrical contacts 51 and 52 placed on opposite sides of the elastic portion 30 both due to the tunneling effect and by contact between the same molecular structures, in a way known per se and not described in detail here for brevity’s sake.

An equivalent electrical resistance REQ of the elastic portion 30 is a function of the mechanical vibrations to which the support 1 is subjected. In fact, the mechanical vibrations have the effect of deforming the elastic portion 30 with respect to a length yO thereof at rest, along the main direction P of the support 1 , as shown schematically in Figures 3A-3B and 4A-4B. In the present invention, the expression ‘along the main direction P’ is to be understood as comprising a direction corresponding to or parallel to the main direction P to which an applied force, a deformation, a length, a distance, etc., is aligned.

In particular, a compressive force F(t) applied to the support 1 associated with a mechanical vibration causes a compression of the elastic portion 30 that reduces itself, along the main direction P, to a compressed length y1 that depends on the compressive force F(t) and on the elastic modulus of the polymer of the elastic portion 30.

This compression causes a reduction of an average distance - along the main direction P - between the carbon molecular structures 31 proportional to the difference between the length at rest yO and the compressed length y1 of the elastic portion 30. Accordingly, there is an increased probability of tunneling phenomena between carbon molecular structures 31 along the main direction P. In addition, a greater probability of contact between carbon molecular structures 31 along the main direction P will result therefrom. These phenomena have the effect of reducing the electrical impedance of the elastic portion 30. These phenomena are represented graphically in detail in Figures 3B and 4B by resistance symbols rOO, r01, and r02 in Figure 3B of a larger size than corresponding resistances r10, r11 and r12 in Figure 4B, wherein the resistances rOO, rO1 , and r02 in Figure 3B connect carbon molecular structures 31 in the resting elastic portion 30 and the resistances r10, r11 and r12 connect the same carbon molecular structures 31 in the compressed elastic portion 30.

This, ata macroscopic level, is reflected in a reduction of the equivalent resistance REQ of the elastic portion 30 of the support 1. In other words, the equivalent electrical resistance REQ of the elastic portion 30 of the support 1 , according to the embodiments of the present invention, is a function of the mechanical vibrations stressing the support 1. The effect of reducing the equivalent resistance EQ will be greater the more yieldable the polymeric base material will be, i.e. , the smaller the elastic modulus of the material and the greater the compression between the elements 10 and 20, with the same imposed load F(t).

In one embodiment - schematically illustrated in Figure 5 -, the support 1 just described and a control device 60 are included in a monitoring system 4 which is configured to detect the vibrations to which the support 1 is subjected.

In the considered embodiment, the control device 60 comprises a measuring unit 61 and a processing unit 62. The measuring unit 61 is electrically connected to the electrical contacts 51 and 52 of the sensor assembly 50 of the support 1 , while the processing unit 62 is connected to the measuring unit 61.

The control device 60 is configured to perform a procedure 100 - of which figure 6 is a flowchart - for monitoring the vibrations generated by the operation of the operating machine 2 to which the support 1 is coupled, as illustrated in Figure 2 above.

In the example considered, the measuring unit 61 is configured to generate a direct or alternating electric current IT, with an intensity - that is, a peak value - constant over time, in the sensor assembly 50 (block 101) and to measure the voltage V(t) that develops between the electrical contacts 51 and 52 (block 103). The measuring system is simple and does not require the use of conditioning circuits (for example Wheatstone Bridge with low-pass filter and demodulator) as in the case of capacitive sensors. This makes it possible to obtain robust measuring systems, with reduced complexity and cost. The processing unit 62 receives the voltage V(t) measured by the measuring device 61 (block 105). The measuring device 61 is configured to provide the measured value of the sampled voltage V(t) with a sampling frequency suitable for covering the frequency band of interest of the specific vibration phenomenon, in a manner known in the art and not described herein for brevity’s sake. For example, the sampling frequency is selected based on the maximum expected frequency of the vibrations.

In the example considered, the processing device 62 is configured to calculate the effective value Veff of the voltage V(t) (block 107) and detect whether the effective voltage value V _e tf equals or exceeds a threshold value VTH and/or whether the effective voltage value V _e tf equals or exceeds the threshold value V H for a predetermined period of time (decision block 109 and output branch N of that block).

Advantageously, the threshold value V H is a limit value associated with the onset of vibrations with excessive extent transmitted to the support 1. These vibrations in turn are indicative of a malfunction, a fault and/or an undesired operation condition of the operating machine 2 with which the support 1 is associated. In fact, the greater the amplitude of the vibrations transmitted by the operating machine 2 to the support 1 , the greater the compression and extension of the elastic portion 30 and, consequently, the greater the variation of equivalent resistance REQ shown by the elastic portion 30. This variation of the equivalent resistance EQ in turn results in a greater amplitude of the effective voltage Vetf developed between the electrical contacts 51 and 52, with the same intensity of the electric current IT injected into the sensor assembly 50.

Preferably, the effective voltage value Vetf is calculated over a selected period so as to effectively detect vibrations of interest. Similarly, the processing device 62 is preferably configurable to output the effective voltage value Vetf and/or a corresponding indication of the intensity of the vibrations measured continuously or at a desired rate.

When an effective voltage value Veff equal to or greater than the threshold value VTH (output branch Y of block 109) is detected, the processing device 62 generates an alarm signal, indicative of an anomalous operation condition of the operating machine 2 (block 111). For example, the alarm signal may be a visual and/or acoustic signal generated through an input/output interface of the processing device 62 and intelligible to a human operator and/or a signal transmitted to another electronic device, for example an electronic control device of a production plant to which the operating machine belongs, a user device of a supervisor of the operating machine.

Optionally, the processing unit 62 is configured to generate a stop signal and to transmit said stop signal to the operating machine 2 (block 113), in order to stop its operation.

However, it is clear that the above examples must not be interpreted in a limiting sense and the invention thus conceived is susceptible of numerous modifications and variations.

For example, although the positioning of the electrical contacts described above allows obtaining optimal performance, nothing prevents, in alternative embodiments (not illustrated), the electrical contacts and the sensor assembly from being connected to the elastic portion according to different configurations. In a non-limiting manner, the electrical contacts may be connected to the elastic portion in opposite positions to each other along directions transverse to the main direction of development of the support, or the electrical contacts may be connected to the elastic portion at mutually adjacent surfaces of the elastic portion, again, the contacts may be arranged on the same surface, preferably spaced from each other along the main direction of development of the support. In an alternative embodiment (not illustrated), the support comprises the measuring unit or a monitoring signal conditioning and acquisition unit configured to amplify and/or filter the voltage value across the sensor assembly in a frequency band of interest and, possibly, calculate the effective value of the voltage.

In another embodiment (not illustrated), the processing unit corresponds to, or is integrated into, a processing module of the operating machine. If necessary, the measuring unit or the conditioning and acquisition unit is also integrated into the processing module of the operating machine.

In one embodiment, the measuring unit or the conditioning and acquisition unit may comprise a transceiver configured to exchange data via radio frequency signals with the processing unit.

In one embodiment, the operating machine is supported on the ground by two or more supports according to an embodiment of the present invention.

In this case, the measuring system is configured to determine a value that considers the effective level of vibration and/or the course of the vibration over time based on the voltages measured across the sensor assembly integrated in each of said two or more supports.

As will be apparent to the skilled person, the control device may be configured to determine that more than one threshold has been reached and/or crossed.

In addition to or alternatively to detecting that one or more thresholds has/have been reached/crossed and/or to the course over time, the control device may be configured to determine a period, a frequency and/or a phase of the vibrations and/or a variation over time of such parameters.

As a further addition or alternative, the sampling frequency used for sampling the voltage across the sensor assembly may be set in order to identify vibrations having a frequency of oscillations comprised in a specific band and/or the measuring unit may comprise a band-pass filter or a similar system configured to identify vibrations or vibration components having a frequency comprised in a specific frequency band or concentrated around a specific frequency.

Naturally, all the details can be replaced with other technically-equivalent elements.

For example, it will be apparent that in alternative embodiments (not illustrated) the support may comprise a single fixing element (a single screw) or no fixing element.

It will also be apparent to a person skilled in the art that the equivalent resistance of the elastic portion of the support, according to the embodiments of the present invention, varies, in particular it increases, when the elastic portion extends under the effect of a deformation force.

Still, in an alternative embodiment, the measuring unit 61 is configured to apply a direct or alternating voltage V(t), with an constant intensity over time, in the sensor assembly 50 (as an alternative to the constant current as described in relation to block 101) and measure the current IT that develops between the electrical contacts 51 and 52 (as an alternative to the voltage as described in relation to block 103), as a function of the electrical resistance of the elastic portion 30. In this case, the processing unit 62 receives the electric current IT measured by the measuring device 61 (similarly to what happened for the voltage as described in relation to block 105). Again, the measuring device 61 is configured to provide the effective value of the electric current IT sampled with a sampling frequency suitable for covering the frequency band of interest of the specific vibration phenomenon.

More generally, the measuring unit in the embodiments of the present invention is configured to measure an electrical magnitude which is a function of a mechanical stress to which the support is subjected.

In conclusion, the materials used, as well as the shapes and contingent dimensions of the devices, apparatuses and terminals mentioned above, may be any according to the specific implementation needs without thereby departing from the scope of protection of the following claims. For example, embodiments may be provided in which the elastic portion is made of a composite material comprising a polymeric matrix (e.g., made of epoxy resin) reinforced with long or short structural non-conductive fibres (e.g., glass fibres). In this case, the carbon molecular structures will be dispersed in the matrix by sonication and calendering technique after coupling with the structural reinforcement fibres.