VIBRATION SENSOR SYSTEM AND RELATED METHOD

Description

VIBRATION SENSOR SYSTEM AND RELATED METHOD DESCRIPTION FIELD OF INVENTION The present invention relates to a vibration sensor system suitable, in particular, for detecting and transmitting selective communication vibrations of insects. STATE OF THE PRIOR ART As has long been known, some animal species communicate with each other through vibrational signals, that is, signals transmitted by exploiting the vibrations of some substrate. Typically, some insects communicate through vibrations transmitted through the leaves and branches on which they perch. This communication technique has been studied to interfere with the behavior of some pests and prevent them from causing damage to agriculture. For example, see Anna Eriksson. "Mating disruption in Scaphoideus titanus Ball (Hemiptera: Cicadellidae) by vibrational signals." Doctoral thesis, University of Pisa. Jernej Polajnar, Anna Eriksson, Marco Valerio, Rossi Stacconi, Andrea Lucchi, Gianfranco Anfora, Meta Virant-Doberlet, Valerio Mazzoni. "The process of pair formation mediated by substrate-borne vibrations in a small insect." Elsevier and Mazzoni, V., Lucchi, A. Ten years of studies on vibrational communication in Scaphoideus titanus: from theory to practice. Proceedings of the Italian National Academy of Entomology.Rendiconti, 62: 209-214 describe various scientific studies aimed at this kind of analysis of the vibrational communications of harmful insects (in particular Scaphoideus titanus, which has harmful effects on the grapevine) and at the potential methodologies that could allow interference with the reproductive capacity of these insects. These studies highlight the potential of these vibrational communication methods, but point out that there are technological challenges in implementing them. To detect vibrational signals, laser interferometry is sometimes suggested, but this is only feasible in the laboratory, not in the field. In this publication Nieri, R., Michael, SCJ, Pinto, CF, Urquizo, 67546 CMF FUMERÒ Srl ON, Appel, H.M., Cocroft, R.B. (2022). Inexpensive Methods for Detecting and Reproducing Substrate-Borne Vibrations: Advantages and Limitations. In: Hill, P.S.M., Mazzoni, V., Stritih-Peljhan, N., Virant-Doberlet, M., Wessel, A. (eds) Biotremology: Physiology, Ecology, and Evolution. Animal Signals and Communication, vol 8. Springer provides signal processing techniques that allow useful information to be obtained even without the use of particularly sophisticated and expensive equipment and sensors. Mechanical vibration sensors are also known, but they have not yet been configured to correctly and selectively detect these vibration signals. An example of a vibration sensor is disclosed in US2010 / 0175476. PROBLEM AND SOLUTION The underlying problem of the invention is therefore to provide a system equipped with a vibrational signal sensor that allows for the selective identification and reproduction of low-frequency vibrational communications of insects, which is small and economical, suitable for field use and sufficiently immune to disturbances deriving from other vibrations. These purposes are achieved by means of the features described in essential terms in the attached claims. BRIEF DESCRIPTION OF THE DRAWINGS Further features and advantages of the invention will, however, become more evident from the following detailed description of a preferred embodiment, given purely by way of example and not of limitation and illustrated in the attached drawings, in which: fig. 1 is a logical diagram of the components of the system according to the invention; Fig. 2 is a longitudinal sectional view of an exemplary transducer / sensor according to the invention; Figs. 3A and 3B are photographic views of some prototype transducers / sensors; Fig. 4 are impedance graphs of two example sensors; Figs. 5A-5D are schematics of exemplary amplifier sections; Figs. 6A and 6B are exemplary circuit diagrams of the system according to 67546 CMF FUMERÒ Srl the invention; and fig. 7 is a logic diagram of a method of operation of the system according to the invention. DETAILED DESCRIPTION OF A PREFERRED FORM OF EXECUTION The device object of the invention is intended to exploit vibrational communication between insects, a communication method adopted by many insects to communicate with each other, to obtain useful information for preventive action on parasites or to interfere in some way with their behavior for the benefit of agriculture. This method involves the transmission and reception of information through substrate-borne vibrations, also called surface waves. A sensor device is preferably configured to have two different modes of use: 1) a passive mode: the device is able to detect the communicative activity of insects and provide statistics on the population present in the location under study; in this mode, the device selectively detects the vibrations produced by insects in order to provide reliable information on their presence and activity; 2) Interactive mode: the device allows for active interaction with a specific target insect, such as the scaphoideus titanus. In this mode, the device can reproduce the vibrations produced by the target insect to communicate with it and control its behavior. This helps prevent the spread of infection and protect host plants from damage. This innovative approach to vibrational communication can be adapted to different situations and crops, offering a wide range of possibilities for crop protection. Thanks to this flexibility, the device can represent an effective and versatile solution for combating insect infestations and preventing crop damage. To implement the two operating modes of the device, a sensor appropriately configured to detect the vibrations produced by insects and a suitable electronic circuitry specifically designed for this purpose are required. 67546 CMF FUMERÒ Srl intended for the sensor. For passive mode, it is also necessary to provide a method for recording the signals in digital format, so as to be able to analyse the information collected by the sensor and provide statistics on the insect population present. For the interactive mode, however, a microcontroller programmed with an algorithm trained on the target insect's communication protocol is required. This allows the microcontroller to actively interact with the insect and control its behavior, following a specific communication protocol. Thanks to these components, the device is able to offer high performance and adapt to different situations and needs. The device according to the invention is composed of a transducer / sensor, which is the component capable of converting an electrical signal into mechanical vibration and vice versa, a control section that includes RTX amplifiers and analog and digital converters, which allows the signal transmitted to the vibration sensor to be controlled both in reception and transmission, as well as a logic processing section in which a data processing procedure is implemented capable of recognizing specific 'patterns' of the detected vibrational signal, to determine the presence of a specific insect, or simulate corresponding output vibrational signals. Referring to Fig. 1, the right-hand side schematically represents a transducer / sensor that acquires vibrations from a natural substrate, such as a leaf or a branch of a plant. The transducer is connected to a backward amplification section (LNA) that amplifies the detected signal towards a BP band-pass filter. Downstream of the BP band-pass filter is an analog-to-digital converter (ADC) that provides the detected signal in digital format to a DSP signal processor. In reverse mode, the forward transmission signal is generated by the DSP processor, then converted by a digital-to-analog converter (DAC) which presents it to a buffer amplifier which in turn inputs it to the transducer which produces a mechanical vibrational motion on the substrate. 67546 CMF FUMERÒ Srl A component that has proven to be quite critical to the device's proper functioning is the signal transducer. Fig. 2 shows a schematic representation of an example transducer / sensor. At the base of the transducer (fig. 2) there is a solenoid S and a magnet MA with a magnetic field linked to the solenoid, mutually movable along a vibration axis. The solenoid S is integral with a vibrating membrane ME which, together with the magnet MA, constitute a classic loudspeaker construction. The membrane ME is fixed to a containment casing B which also houses the solenoid S and the magnet MA. According to the invention, a calibrated mass C is applied to the vibrating symmetry axis of the ME membrane - for example of approximately 10-15 g, but to be chosen based on the specific signal that needs to be acquired and / or reproduced - which moves in solidarity with the ME membrane itself. On the exposed side of the ME membrane on which the calibrated mass C is applied, an internal cap Z is placed which acts as an attenuator of the surrounding sounds (sound absorber) which are a source of noise for the system. The internal cap Z could be made of polyurethane or sound-absorbing sponge or even cork (expensive but efficient) and equipped with a cavity Zi into which the calibrated mass C is inserted without interference. Above the hood Z there is an external sound-absorbing hood F with the additional feature of being rigid and protective against external agents such as rain, wind and impacts. The outer cap F has a large internal cavity Fi into which the inner cap Z is glued. According to a preferred embodiment, a dissipative element Ci can be applied (glued) to the calibrated mass C in interference (adherent or sliding) with the cap Zi. The assembly of the membrane ME and calibrated mass C constitutes the tuned element that determines the desired operating frequency of the transducer, while Ci represents the damping element of the resonant system: Ci is also chosen based on the specific signal to be acquired (the greater the friction induced by Ci on Z, the greater the damping effect of the frequency peaks, with consequent broadening of the bandwidth of interest). 67546 CMF FUMERÒ Srl This sound transducer configuration has proven particularly effective. Thanks to its construction, it is sufficiently selective with respect to the desired frequencies. In particular, two measures are effective in obtaining the desired selectivity: - a screen that attenuates sounds coming from the surrounding world; - the calibrated mass C connected to the membrane which, when suitably sized, constitutes an inertial element capable of being frequency selective and therefore filtering low frequency disturbances (for example vibrations induced by the wind). At very low frequencies, in fact, the calibrated mass C moves together with the system, preventing the signal from being transferred to the coil (the coil and the magnet move together). It is believed that frequencies below 50-70Hz are not significant for the vibrational communication of insects, however there is a certain probability of finding disturbances caused by the wind and therefore eliminated. At higher frequencies, however, the mass remains still thanks to its inertia and the membrane that connects it to the rest of the system acts as a decoupler: in this way, the vibrations of the substrate on which the casing B is placed cause the magnet to move relative to the mass, generating an emf (electromotive force) induced in the inductor of the solenoid S. At very high frequencies, the substrate acts as a natural filter that does not let the vibrations pass. Laboratory measurements show that signals above 1KHz are naturally filtered by the wood of the branch to which the device is applied, typically vine wood; evidently, different substrates have different characteristics, but most are limiting at high frequencies. The system works as a band-pass filter and the value of the calibrated mass C is selected based on the desired characteristic: the smaller it is, the more easily low frequencies are neglected. This is especially useful since each insect has its own operating frequency. The transducer also exploits the reciprocity property of the field 67546 CMF FUMERÒ Srl magnetic to realize a transceiver (RTX) function of the transducer: - a variation in the magnetic field linked to the solenoid, due to a mechanical force transferred from the vibrating substrate, generates an induced emf on the solenoid and therefore a modulated current which is received as an analogue signal; - a suitably modulated electric current inserted into the solenoid generates a magnetic field that can exert a force on the magnet which is transmitted as a vibration on the underlying substrate. The mechanical component connected to the electromagnetic transducer is effectively a tuned and resonant device. Its frequency characteristics are characterized by reactive components, which in this case are the magnet's mass, the membrane's spring constant, and a possible resistive (dissipative) component. Fig. 4A illustrates the mechanical model in analogy with the sensor: the mass (C ), the membrane (ME) and the damper (Ci) correspond respectively to a mass C, to the spring with elastic constant ME and to a heat sink with friction coefficient Ci. Fig. 4B illustrates the electrical equivalent of the electromechanical model in analogy with the mechanical model in Fig. 4A. Figure 4B also shows the simplified electrical model in which the equivalent mechanical component is neglected. This model, given its simplicity, will often be used in subsequent representations to carry out the sizing calculations. Fig. 4C shows the impedance (real and imaginary parts) of two different sensors, appropriately calibrated, with the calibrated mass C chosen to receive two different frequencies. In particular, the sensor represented in the leftmost graph is calibrated to receive and transmit the communication frequencies of Scaphoideus Titanus. The frequency selection is very precise thanks to the selection of the "resonant mass". The transducer, typically of very small dimensions, for example with a diameter of a few centimetres, can be applied (for example 67546 CMF FUMERÒ Srl glued or otherwise joined together) to the substrate and thus detect or transmit the desired vibrations. A general diagram of the amplification section is shown in Figs. 5 and 6. The amplifier is configured to use the sensor / transducer for both reception and transmission, allowing for signals that follow the same path and can be easily correlated. The amplifier offers high precision, programmable gain, and low noise, ensuring high and reliable performance. The amplifier can measure the mechanical impedances of the medium in which the sensor is applied (this function is very useful for academic purposes as it allows for some studies / considerations on substrates; for the scaphoideus it is not strictly necessary). The amplifier section is preferably designed to meet two different requirements. On the one hand, it feeds an input voltage into the transmit transducer (Tx): in this way, the system is able to transform an electrical signal into a mechanical vibration, which is propagated from the sensor to the substrate. On the other hand, it detects the current generated by the magnetic sensor in the receive mode (Rx): in this way, the system is able to transform a mechanical stress applied to the sensor (vibration) into an electrical current, which can be processed to obtain detailed information on the vibration spectrum and therefore on the target insect or the characteristics of the substrate in which the vibrations propagate. In principle, a voltage-controlled current source (vccs:voltageControlledCurrentSource) with negative voltage feedback provides this function. In the simplest version, a source follower performs this function. General Principle The basic circuit is illustrated in Fig. 5A, where a VCCS with negative feedback on the load is represented: - Vsensor=Vin (thanks to feedback)^TX function - Iout = Isensor=induced emf / Rin (resistance seen by the sensor which in 67546 CMF FUMERÒ Srl in this case the following is true: Isensor =n——--- with gm=transconductance) ^function —+Rsensor gm TX The function you want to achieve is to force a voltage on the sensor to obtain the conversion into vibrations (TX function) and / or read a current obtained from the electromagnetic induction produced by vibrations incident on the sensor (RX function). The TX and RX operations applied to the same sensor are particularly advantageous because: - Economic - Simple - The Tx and Rx signals see the same path to the insect Figs. 5B-5D show alternative circuits for the amplifier section. Fig. 5B represents the simplest implementation of the general principle but with the following limitations: - Limited Tx accuracy as the input signal is not entirely converted into vibration due to the finite transconductance value (gm) - limited ability to receive signals in Rx: the emf induced in the solenoid by vibrations, in order to be efficiently converted into current, must see a small resistance across its terminals (as a load); the value of this resistance is imposed by the transconductance offered by the amplifier (the resistance seen by the sensor is 1 / transconductance gm) The configuration in Fig. 5C represents an evolution compared to the previous implementation, as it introduces a high-gain operational amplifier (ÒPAMP) connected with negative feedback. The high gain and feedback allow for a precise voltage to be applied to the sensor (TX function); furthermore, the Rx function is also improved by reducing the impedance seen by the sensor, allowing for a more precise conversion from induced emf in the sensor to current. Fig. 5D represents a further evolution of the solution in fig. 5C by using a class AB output stage compared to the class A in fig. 5D. 67546 CMF FUMERÒ Srl Figures 6A and 6B show two possible synoptic implementation schemes for the entire TRX system, with the two amplification sections. Focusing on Fig. 6A, the following points stand out: - The cooperation between the transmitting (TX) and receiving (RX) sections, both connected to the same sensor. - A gain-controlled transmission signal application mode: The transmitted signal, usually generated by a microcontroller's DAC, has too high an amplitude (power) to be compatible with the insects' vibrational signals (several orders of magnitude difference). Thanks to the Tx Zgain and Tx Zinput components, it is possible to precisely control the transmitted signal (applied as a voltage to the sensor) so that it is compatible with the insects' levels. - The recovery and amplification of the induced current from the received signal via the Pmirror and Nmirror mirrors is illustrated, followed by amplification through a current-to-voltage converter using a ÒPamp in feedback with Rx gain (together they form a current-to-voltage transconductance amplifier). - The current and voltage conversion of the Rx amplifier is useful because the reading of the signal by the microcontroller occurs via a voltage ADC. With reference to fig. 6B, we want to simplify the implementation of fig. 6A by exploiting the possible integrated implementation within the TX opamp of the components that implement the source follower of fig. 6A (reduction of component costs and PCB construction). In the circuit part, a data storage section is also preferred, preferably downstream of the ADC converter section, which allows the sampled signals to be stored and a downstream analysis to be performed. In particular, according to a preferred embodiment of the invention, a pattern matching analysis is performed on the acquired vibrational signal data, which allows the presence of the insect to which the device is 'tuned' to be identified in a very short time (Fig. 7). The specific algorithm implemented on board the DSP, which is not the subject of the present invention and therefore will not be 67546 CMF FUMERÒ Srl Described in further detail, it uses well-known FFT, DTW (dynamicTimeWarp) systems, and digital filters to compare specific characteristics extracted from known vibration spectra of the insects being monitored (e.g., Scaphoideus titanus) with the characteristics of the vibration spectra detected in real time in the field. The coincidence of these characteristics, within established thresholds, allows the system to recognize the presence of the monitored insect and identify the number of occurrences per unit of time, which is an important indicator for allowing agronomists, for example, to receive timely alerts to the increase in the population of a pest insect. An early warning of the increase in a certain pest allows for more targeted intervention with protection or extermination measures and to minimize the impact of these measures on other aspects of the agricultural environment. This variant thus provides a portable early detection system based on insect vibrational communication, to help agronomists detect infestations before they spread. The system leverages the ability to intercept insect vibrational communication via substrate, adding a stored data processing component capable of comparing the received signals in real time with pre-recorded patterns in internal memory and alerting the operator to the presence of an insect. The fundamental hypothesis is that each insect species possesses unique and characteristic vibrational signals that allow for its identification. The distinctive properties of these vibrational signals manifest themselves in both the temporal (time domain) and frequency (frequency domain) dimensions and are called 'characteristics' or 'features'. The invention works by means of a comparison analysis between the features previously extracted and statistically processed, which act as a reference, and the signals captured and acquired by the hardware device and analysed in real time. The outcome of the comparison, which can be expressed in terms of the frequency of occurrence over time of the vibrational signal typical of the monitored insect, can be shown to the operator by means of output means, for 67546 CMF FUMERÒ Srl For example, a visor, a low-range radio frequency transmitter (Bluetooth, NFC, etc.), a USB port, or other low-power device. The visor can also be a small display activated by pressing a local button, for example, manually activated by an operator during a reconnaissance phase of multiple devices installed in the field. The comparison of vibration profile characteristics is achieved through the use of a classifier, which can be based on maximum likelihood principles, advanced statistical methods, or both. The classification process assigns a score to each input signal characteristic, quantifying its correspondence with the characteristics of the stored model. The classifier can be a Bayesian or KNN classifier in the statistical case, or a maximum likelihood classifier such as DynamicTimeWarp or LongestCommonSubSequence. As can be seen from the above description, the device of the invention perfectly achieves the objectives set out in the preamble. Specifically, using a sensor / transducer with an optimized configuration—which can simply be placed in contact with the vibration transmission substrate—and a suitable TRX amplification section, with a related data storage and processing section, it is possible to provide a portable, low-power, easily field-installable device that provides timely information useful to agronomists in combating specific insect infestations. By detecting vibrational communications, it is possible to obtain useful information on the occurrence and frequency of these insects. By operating in reverse, i.e., by transmitting selective vibrational signals to the substrate, it is potentially possible to interfere with communication between insects and modify their behavior, for example by inhibiting their reproduction or attracting them to suitable traps. It is understood, however, that the invention is not to be considered limited to the particular provisions described above, which constitute only exemplary embodiments of it, but that various variants are possible, all within the reach of a technician in the field, without thereby departing from the scope of protection of the invention itself, as defined by the claims which 67546 CMF FUMERÒ Srl follow.

Claims

1. Vibration sensor system comprising a transducer / sensor suitable for contact with a vibration transmission substrate, an electrical control section for said transducer / sensor, and a logic section for processing data received from and transmitted to said control section, characterised in that said transducer / sensor comprises a solenoid (S) and a magnet (MA) with a magnetic field linked to said solenoid (S), mutually movable along a vibration axis, a vibrating membrane (ME) integral with said solenoid (S) which define a loudspeaker configuration, said vibrating membrane (ME) being fixed to a containment casing (B) in which said solenoid (S) and magnet (MA) are also housed, a calibrated mass (C), applied to said membrane (ME), tunable to define a desired operating frequency of the transducer / sensor,and in which an internal cap (Z) is also provided which acts as a damper / sound absorber and is applied on the side of said membrane (ME) on which said calibrated mass (C) is applied and equipped with an internal cavity (Zi) in which said calibrated mass (C) is housed, an external cap (F) which is sound absorbing and protective against external physical agents and is placed above said internal cap (Z).

2. Vibration sensor system as in claim 1, wherein a damper (Ci) is also provided which is integral with the calibrated mass (C) and arranged in interference with said internal cavity (Zi) of the internal cap (Z).

3. Vibration sensor system as in claim 1 or 2, wherein said external cap (F) joined to the containment casing (B) is joined to the internal cap (Z) consisting of a light and porous body without interference with membrane (ME) in which said calibrated mass (C) is inserted.

4. Vibration sensor system as in claim 2, wherein 67546 CMF FUMERÒ Srl said external cap (F) has a large internal cavity (Fi) in which said internal cap (Z) is placed.

5. Vibration sensor system as in any of the preceding claims, wherein said electrical control section comprises at least one backward amplification section (LNA) that amplifies a vibrational signal acquired by said transducer / sensor towards a band-pass filter (BP), downstream of which is arranged an analog-to-digital converter (ADC) that supplies said acquired vibrational signal in digital format to a signal processor (DSP) arranged in said logic processing section.

6. Vibration sensor system as in claim 5, wherein said signal processor (DSP) is configured to generate digital data representative of a vibration signal, and is arranged upstream of a digital / analog converter (DAC) connected to a buffer amplifier in turn electrically connected to said transducer / sensor.

7. A vibration sensor system as claimed in any preceding claim, wherein said data processing logic section further comprises a data storage section adapted to store sampled vibration signals.

8. A vibration sensor system as claimed in claim 7, wherein said signal processor (DSP) is configured to perform a pattern matching analysis comparing said sampled vibration signals to predetermined characteristics of a reference vibration signal spectrum.

9. A method of preventing agricultural pest infestations, comprising the steps of arranging a plurality of systems as in any preceding claim, tuning a transducer / sensor to a vibrational signal typical of said pest insects, acquiring and storing vibrational profile data by said transducer / sensor and performing a comparison with pre-stored typical vibrational profiles, determining an occurrence of said pest insects from said comparison, 67546 CMF FUMERÒ Srl reporting a trend of said occurrence on output means.