Plant electrophysiological analysis system

Abstract

A plant electrophysiological analysis system (1) comprising at least one first acquisition device (2) arranged to capture electrical signals (P1) emitted by one or more plants (P) and to convert said electrical signals into digital signals (S21), characterized in that it comprises a photovoltaic panel (8) arranged to power said first acquisition device. Figure to be published with the abbreviation: Fig. 1

Description

Title of the invention: Electrophysiological plant analysis system

[0001] The invention relates to the field of electrophysiological analysis of plants. More specifically, the invention relates to a system for electrophysiological analysis of several plants.

[0002] It has been observed that plants emit electrical signals, particularly in the form of action potentials, reflecting their physiological state. By measuring these electrical signals using electrodes and analyzing them, it is thus possible to determine the physiological state of a plant more quickly and reliably than by direct observation means. In addition, if a stress or disease situation is detected, it is also possible to propose, immediately and automatically, corrective actions to remedy it.

[0003] However, existing electrophysiological plant analysis systems are designed for laboratory use and are not suitable for agricultural use. Indeed, the known systems are based, on the one hand, on an electrical signal acquisition system allowing these signals to be digitized for processing and, on the other hand, on a module for processing these digitized signals implementing, in particular, statistical analysis methods. It is therefore necessary to acquire a plurality of electrical signals simultaneously, over long periods. Thus, for agricultural use, it is necessary to install several acquisition devices in a field.This multiplicity of acquisition systems therefore requires the use of a multitude of power cables to electrically supply each of the acquisition devices and data transmission cables to enable the transmission of digitized signals to the processing module. The number of cables thus required is detrimental to the robustness of the system and its simplicity of installation and use.

[0004] The present invention is placed in this context and thus aims to remedy the drawbacks cited, by proposing a system for electrophysiological analysis of plants which is robust and simple to install and use.

[0005] For these purposes, the invention relates to a system for electrophysiological analysis of plants, comprising at least one first acquisition device arranged to capture electrical signals emitted by one or more plants and to convert said electrical signals into digital signals, characterized in that it comprises a photovoltaic panel arranged to power said first acquisition device.

[0006] It is understood that, thanks to the invention, the acquisition device can be powered using the photovoltaic panel and therefore no longer requires a power cable. It is thus possible to reduce the number of cables necessary for operating the system, which makes it possible to increase its robustness while simplifying its installation and use.

[0007] Advantageously, the system comprises a voltage regulator connected to the photovoltaic panel. This voltage regulator is in particular arranged to maintain the electrical power, and in particular the electrical voltage, supplied by the photovoltaic panel at a constant value. According to an exemplary embodiment, the voltage regulator may be a linear voltage regulator. Where appropriate, the voltage regulator may be a linear regulator with low voltage drop. Such a regulator is also called an LDO regulator, from the English Low DropOut. In another exemplary embodiment, the voltage regulator may be a DC / DC type regulator, for example a voltage step-down type regulator, in particular a Buck type regulator.

[0008] In one embodiment of the invention, the first acquisition device comprises a rechargeable electric battery, the photovoltaic panel being arranged to charge said electric battery. According to a variant, the photovoltaic panel is arranged to directly power the first acquisition device.

[0009] Advantageously, the photovoltaic panel is arranged to simultaneously charge the electric battery and power said first acquisition device. Where appropriate, the system may comprise a unit for controlling the power supply of the first acquisition device, the control unit being arranged to selectively control the power supply of the first acquisition device by the photovoltaic panel and / or the electric battery, for example as a function of a daytime or nighttime operating condition of the system, local sunlight information and / or information relating to the state of charge of the electric battery.

[0010] Advantageously, the system may comprise a charge controller for said electric battery arranged to regulate the electric current generated by the photovoltaic panel.

[0011] Advantageously, the rechargeable electric battery has a nominal charging current value. In a first embodiment of the invention, the charge controller is arranged to control the value of the electric current generated by the photovoltaic panel so that this value substantially corresponds to said nominal charging current value. For example, the charge controller may be a chopper. In this mode, the aim is thus to recharge the electric battery as quickly as possible. In a second embodiment of the invention, the charge controller is arranged to control the value of the electric current generated by the photovoltaic panel to a value substantially lower than said nominal charging current value, for example less than 10%, in particular less than 5%, for example equal to 2.2%, of said nominal charging current value. For example, the charge controller may be a current limiting diode. In this mode, beyond reducing the cost of the system, slow recharging of the electric battery is allowed, which makes it possible to reduce the noise of this recharging on the measurement of the electrical signals emitted by the plant(s) by the first acquisition device.

[0012] In an exemplary embodiment of the invention, the first acquisition device comprises at least one first electrode intended to be connected to a plant to capture a first analog electrical potential, the first acquisition device being arranged to generate a digital signal from said first analog electrical potential.

[0013] If desired, the or each first input connected to the or one of the first electrodes is associated with a filter arranged to filter the first analog electrical potential captured by this first electrode. The or each of the filters may comprise an analog smoothing filter and / or a filter for protection against electrostatic discharges.

[0014] According to this example, the first acquisition device may comprise an analog-digital converter provided with a first input connected to the first electrode to receive the first analog electrical potential, the analog-digital converter being arranged to measure the potential difference between the first analog electrical potential received and a reference electrical potential and to convert this measured potential difference into a digital signal. Where appropriate, said reference electrical potential may be obtained by means of the electric battery.

[0015] Preferably, the first acquisition device comprises a second electrode intended to be connected to said plant, the analog-digital converter being provided with a second input connected to said second electrode, the second input being connected to the reference electrical potential. For example, the second input may be connected to the ground of the electric battery. According to one example, the pair of first and second electrodes may be connected to the plant so as to measure a linear electric field generated by the superposition of the transient depolarizations of the membranes of the leaf cells and / or by the ionic exchanges at the level of the root system.For example, each of the first and second electrodes may be connected to the stem of the plant to contact the phloem or alternatively, one of the electrodes may be connected to the stem of the plant and the other of the electrodes may be connected to an underground bulb of the plant.

[0016] Advantageously, the analog-to-digital converter may comprise an operational amplifier, the operational amplifier being arranged to receive the first analog electrical potential and said reference electrical potential, the analog converter comprising an elementary delta-sigma analog-to-digital converter connected to the output of the operational amplifier. The term "link between the output of an operational amplifier and an elementary delta-sigma analog-to-digital converter" means both a single link between an amplifier with a single output and the converter on which the signal amplified by the amplifier passes and a double link between an amplifier with a differential output and the converter where the amplified signal is obtained by the difference between the signals passing on each of the lines of the double link.

[0017] For example, the operational amplifier may be a low-noise programmable gain amplifier (also called a PGA). Where appropriate, the operational amplifier may be arranged to have a gain of at most 24 and to introduce noise whose average level is less than 5 pV and in particular substantially 0.1 pV in the case of an amplifier with a gain of 24. Advantageously, the elementary delta-sigma analog-digital converter is arranged to have a sampling rate greater than 50 SPS (sample per second) or 50 Hz, or even greater than 250 SPS or 250 Hz, and to convert a signal received at the input into a digital signal coded on 24 bits.Where appropriate, the unitary assembly formed by an operational amplifier and an elementary delta-sigma analog-to-digital converter is arranged to have an effective number of bits (also called ENOB, from the English Effective Number Of Bits) of at least 16, and in particular at least 19 for an amplifier gain of 24 and for a sampling rate of 250 SPS. This combination is particularly suitable for the electrophysiological analysis of plants insofar as the electrical potential differences from the operational amplifiers are low-amplitude analog signals (of the order of a microvolt) which can be amplified by the amplifier while introducing little noise and distortion, thanks to a low gain, and which nevertheless be converted by the converter into digital signals with high resolution (of the order of a nanovolt).

[0018] Advantageously, the first acquisition device comprises a housing in which the analog-digital converter and, where appropriate, the electric battery and the charge controller are arranged.

[0019] Advantageously, the electrophysiological analysis system comprises a digital processing module for the digital signal converted by the analog-digital converter of the acquisition device, for example arranged to implement a or more methods of processing this digital signal to determine a physiological state of the plant.

[0020] Advantageously, the processing module can be arranged to implement one or more methods for processing the generated digital signal to determine a physiological state of the plant. It has in fact been observed that the potential differences thus measured and therefore the converted digital signals exhibit variations which are functions of the physiological state of the plant, and in particular of its sunshine, its water stress, its thermal stress, etc. These variations are variations of certain frequency components of these converted digital signals, and in particular variations of low amplitudes of high frequency components.

[0021] The processing module may be arranged to carry out a spectral analysis of the digital signal. For example, the processing module may be arranged to obtain a spectrum from the digital signal (for example by means of a Fourier transform or by a wavelet decomposition) and to determine one or more spectral power indicators from this spectrum, and in particular one or more indicators chosen from the following indicators: a. a spectral edge frequency (also called Spectral Edge Frequency or SEF), namely a frequency below which 95% of the total spectral power is concentrated; b. a median frequency (also called in English: Median Edge Frequency or MEF), namely a frequency below which 50% of the total spectral power is concentrated; c. a power index, namely the total spectral power contained in a given frequency band, in particular a power index in the frequency bands known as beta (>0.5 Hz), alpha (0.3-0.4 Hz), theta (0.1-0.2 Hz) and delta (0-0.1 Hz); d. power index ratios, including a ratio of the delta power index and the theta power index; e. spectral entropy (also called Power Spectrum Entropy or PSE).

[0022] Advantageously, the processing module may implement methods for analyzing variations in this or these indicators, in particular to recognize a shift in the spectral frequency front and / or the median frequency according to a given model or a variation in a power index or a ratio of power indices according to a given model, or a variation in the spectral entropy according to a given model. This may, for example, be a method for classifying a variation in this or these indicators from a library of variation models. predetermined, each predetermined variation model being associated with a given physiological state of a plant. Such a classification process could, for example, be implemented by a pattern recognition algorithm based on automatic learning to recognize the models in said library of models.

[0023] The present invention is now described using examples which are solely illustrative and in no way limitative of the scope of the invention, and from the attached illustration:

[0024] [Fig-1] represents a system for electrophysiological analysis of plants according to a embodiment of the invention.

[0025] [Fig.l] shows schematically and partially an electrophysiological analysis system 1 according to a first embodiment of the invention.

[0026] The system 1 comprises a first acquisition device 2 comprising a plurality of first electrodes 21 each intended to be connected to a separate plant P to capture a first analog electrical potential PI and a plurality of second electrodes 22 each intended to be connected to one of said plants P. Each plant P is thus connected to a pair of electrodes 21 and 22, the first electrode 21 being for example connected at the level of an upper section of the stem of the plant P to be in contact with the phloem and the second electrode 22 being for example connected at the level of a lower section of the stem of the plant P also to be in contact with the phloem

[0027] The first acquisition device 2 comprises a multi-channel analog-to-digital converter 3 provided with a plurality of first inputs 31, each connected to one of the first electrodes 21 to receive the first analog electrical potential PI captured by this electrode. The multi-channel analog-to-digital converter 3 is further provided with a plurality of second inputs 32, each connected on the one hand to one of the second electrodes 22 and on the other hand to the same common reference electrical potential P2. Each of the inputs 31 and 32 is associated with a filter (not shown) arranged to filter the first or second electrical potential PI, P2 intended to be received by this input

[0028] The multi-channel analog-to-digital converter 3 comprises a plurality of operational amplifiers 33 each arranged to receive one of the first analog electrical potentials PI from one of the first inputs 32 and said common reference electrical potential P2 from one of the inputs 32 and to measure an electrical potential difference P21 between this first multiplexed analog signal PI and the common reference electrical potential P2. In the example described, each operational amplifier is a low-noise programmable-gain amplifier, also called PGA (Programmable-Gain Amplifier), whose gain can be programmed up to a value of 24 without an average level of the noise introduced into the signal amplified by the amplifier exceeds a value of approximately 2 pV for this gain of 24.

[0029] The analog converter further comprises a plurality of elementary analog-digital converters 34 of delta-sigma type, each connected to the differential output of one of the operational amplifiers 33 to convert the electrical potential difference P21 measured by this operational amplifier into a digital signal S21. In the example described, each elementary converter of delta-sigma type 5 is arranged to sample the electrical potential difference P21, for example at a sampling frequency of 250 Hz, so as to obtain a digital signal S21 coded on 24 bits. This combination of low-noise PGAs and delta-sigma type converters makes it possible to obtain an effective number of bits of at least 19 when the PGA gain is set to 24.In this way, the digital signal S21 obtained at the output of the elementary converter 5 has a particularly satisfactory resolution, taking into account the voltage levels observed for the electrical potentials captured by the electrodes. It should be noted that the sampling frequency can advantageously be modulated, in particular as a function of the desired recording duration.

[0030] The first acquisition device 2 further comprises a connection unit 4 to a data transmission network 5. The system 1 comprises a digital processing module 6, connected to the data transmission network 5 to receive the digital signals S21 converted by the multi-channel analog-digital converter 3 and arranged to implement one or more methods for processing these signals to determine a physiological state of the plants P connected to the first electrodes 21. Without this being limiting, the processing module 6 may be arranged to obtain a spectrum from the digital signals S21 (for example by means of a Fourier transform or by a wavelet decomposition) and to determine one or more spectral power indicators from this spectrum, then to implement methods for analyzing the variations of this or these indicators in order to determine the physiological state of the plants P

[0031] In order to electrically power the first acquisition device 2 and to provide the common reference electrical potential P2, the system 1 comprises a photovoltaic panel 8 and the first acquisition device 2 comprises an energy source 7 comprising several rechargeable electric batteries.

[0032] The photovoltaic panel 8 is associated with a linear voltage regulator 81 of the LDO type, regulating the electrical power generated by the photovoltaic panel to provide an electrical voltage of constant value.

[0033] The first acquisition device 1 comprises a first power supply line connecting the photovoltaic panel 8 and its regulator 81 to a switching unit 82. During the daytime, a control unit (not shown) controls the switching unit 81 so as to authorize the power supply of the first acquisition device 2 directly by the photovoltaic panel 8. If necessary, the reference potential P2 is thus provided by the linear voltage regulator 81.

[0034] The first acquisition device 1 also comprises a second power supply line connecting the photovoltaic panel 8 and its regulator 81 to the energy source 7, via a charge controller 83. The charge control 83 is notably arranged to authorize the charging of the batteries of the energy source 7, for example by converting the electrical power supplied by the panel 8 and the regulator 81 into a power adapted to the charging of the batteries. During the day, the photovoltaic panel 8 therefore supplies the first acquisition device 2 and simultaneously charges the electric batteries of the energy source 7.

[0035] The energy source 7 is also connected to the switching unit 81. During the daytime, the switching unit 81 prohibits the power supply of the first acquisition device 2 by the energy source 7.

[0036] During the night period, the switching unit 81 authorizes the power supply of the first acquisition device 2 by the energy source 7, for example via each of the batteries or alternatively by the most charged battery. The common reference electrical potential P2 is in this case provided by the ground of this or these batteries.

[0037] In the example described, the multi-channel analog-digital converter 3, the energy source 7, the switching unit 82 and the charge controller 83 are integrated in the same housing 23 of the first acquisition device 2.

[0038] Although the example described in [Fig. 1] describes only a single first acquisition device 2, it goes without saying that the analysis system 1 may employ a plurality of acquisition devices, each being similar to the first acquisition device 2 and being connected to one or more other plants, the digital signals converted by these devices all being transmitted to the processing module 6 to be processed there.

[0039] The preceding description clearly explains how the invention makes it possible to achieve the objectives it has set itself, and in particular by proposing a system for electrophysiological analysis of plants whose acquisition device is powered, directly or indirectly, by means of a photovoltaic panel. It is thus understood that it is not necessary to provide an electrical power supply cable, which makes it possible to reduce the number of cables necessary for operating the system, and therefore to make the system more robust and simpler.

[0040] In any event, the invention cannot be limited to the embodiments specifically described in this document, and extends in particular to all equivalent means and to any technically effective combination of these means. In particular, it will be possible to provide for comparing the first electrical potentials captured by the first electrodes directly to second electrical potentials captured by the second electrodes, the second inputs of the analog-digital converter not being in this case connected to the same common reference electrical potential.

Claims

Claims

1. System (1) for electrophysiological analysis of plants, comprising at least one first acquisition device (2) arranged to capture electrical signals (PI) emitted by one or more plants (P) and to convert said electrical signals into digital signals (S21), characterized in that it comprises a photovoltaic panel (8) arranged to power said first acquisition device, in that it comprises a voltage regulator (81) connected to the photovoltaic panel (8) and in that the voltage regulator (81) is a linear regulator with low voltage drop.

2. System (1) according to the preceding claim, characterized in that the first acquisition device (2) comprises a rechargeable electric battery (7), the photovoltaic panel (8) being arranged to charge said electric battery.

3. System (1) according to the preceding claim, in which the photovoltaic panel (8) is arranged to simultaneously charge the electric battery (7) and power said first acquisition device (2).

4. System (1) according to one of claims 2 or 3, characterized in that it comprises a charge controller (83) of said electric battery (7) arranged to regulate the electric current generated by the photovoltaic panel (8).

5. System (1) according to one of the preceding claims, wherein the first acquisition device (2) comprises at least one first electrode (21) intended to be connected to a plant (P) to capture a first analog electrical potential (PI), the first acquisition device being arranged to generate a digital signal (S21) from said first analog electrical potential.

6. System (1) according to the preceding claim, in which the first acquisition device (2) comprises an analog-digital converter (3) provided with a first input (31) connected to the first electrode (21) to receive the first analog electrical potential (PI), the analog-digital converter being arranged to measure the potential difference (P21) between the first analog electrical potential received and an electrical potential reference (P2) and to convert this measured potential difference into a digital signal (S21).

7. System (1) according to the preceding claim, in which the first acquisition device (2) comprises a second electrode (22) intended to be connected to said plant (P), in which the analog-digital converter (3) is provided with a second input (32) connected to said second electrode, the second input being connected to the reference electrical potential (P2).

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