WO2007107678A2

WO2007107678A2 - Autonomous unit for a network of measuring sensors, network comprising said autonomous unit, and communication protocol of said network

Info

Publication number: WO2007107678A2
Application number: PCT/FR2007/050985
Authority: WO
Inventors: Michel Petit; Stéphane URRUTIA; Hervé MICHON; Jean-Marc Bernex; Philippe Mirande-Iriberry
Original assignee: Lyracom
Priority date: 2006-03-22
Filing date: 2007-03-22
Publication date: 2007-09-27
Also published as: EP1997355A2; DE602007002995D1; FR2899035B1; ATE447315T1; WO2007107678A3; EP1997355B1; FR2899035A1

Abstract

The invention relates to an autonomous unit (20) comprising at least one measuring means (18), autonomous supply means (38), and means for transforming external energy into electrical energy, especially a photovoltaic panel which uses solar energy, can be incorporated into a network of autonomous units, and can communicate the measured value(s) by communication means (30). Said autonomous unit is characterised in that it comprises means which are used to store the electrical energy and are provided with a device for switching at least two capacitors, protected by protection means.

Description

AUTONOMOUS UNIT FOR A NETWORK OF MEASURING SENSORS, NETWORK INCORPORATING SAME AUTONOMOUS UNIT AND PROTOCOL OF

COMMUNICATION OF THE SAID NETWORK

The present invention relates to an autonomous unit for a measurement sensor network, to a network incorporating at least one autonomous unit and to a communication protocol of said network.

Typically, the accuracy of a measurement over a relatively large geographic area is related to the number of measurement points.

In the field of public lighting, the control of lighting or extinguishing of the public lighting for a sector of a city can be triggered from a value measured by a single brightness sensor, in particular a cell photovoltaic, measuring sunshine. The measured value is often a rough approximation of the brightness of the area to be illuminated which does not allow to optimize the management of the lighting.

One solution to increase accuracy is to increase the number of measurement points to obtain a more representative measured value. However, this solution requires the installation of a f ilaire network to ensure the power supply of the measurement sensors and the transmission of data. Or ₁ installing a network ilar f is relatively expensive. In some cases, it may even be impossible.

When the measurement sensors are grafted onto a network having a power supply, for example a street lamp network of a public lighting, it is possible to capture a portion of this electrical energy to power the sensors of measure, and use said network power supply to transmit the data using the carrier current method. However, this solution is not satisfactory because it induces overconsumption and the transmitted measurements can be tainted by error. In the absence of an existing network, even if some sensors can be communicating and transmit the data via wireless communication means, the power supply of said measurement sensors remains problematic.

Batteries or batteries can be provided to ensure the autonomy of said sensors. However, this solution is not satisfactory because these power supply means have a limited life, which induces significant maintenance to ensure their replacement. In addition, batteries are generally a source of significant pollution.

Also, the present invention aims at overcoming the disadvantages of the prior art by proposing an autonomous unit incorporating at least one measurement sensor, making it possible to multiply the measurement points, not requiring the installation of a dedicated network and / or major maintenance and using renewable energy.

For this purpose, the subject of the invention is an autonomous unit incorporating at least one measurement means, comprising autonomous power supply means comprising means for transforming an external energy into electrical energy, in particular a photovoltaic panel using the energy solar, and capable of integrating into a network of autonomous units and communicating by means of communication the measured value or values, characterized in that it comprises means for storing said electrical energy comprising a switching device capacitors, at least two capacitors, protected by means of protection. Other features and advantages will become apparent from the following description of the invention, description given by way of example only, with reference to the accompanying drawings in which:

FIG. 1 represents the composition of an autonomous unit according to one embodiment,

FIG. 2 is a perspective view illustrating the elements composing an autonomous unit,

FIGS. 3A and 3B show the printed circuit of an autonomous unit according to its preferred embodiment, FIGS. AA and 4B illustrate the Parallel / Series switching method,

- Figure 5 shows the communication protocol.

The present invention is now described applied to the management of a public lighting network. Nevertheless, the invention may have other applications for which it is necessary to disseminate several measurement sensors over a geographical area.

In order to refine the measurement, in particular the brightness measurement for controlling the switching on or off of the light points of a lighting network, a network consisting of at least one autonomous unit 20 incorporating at least one means is provided. 18 measurement, including brightness, and at least one coordinator, capable of communicating directly or indirectly with said autonomous units 20 and collect the measured values. In the case of management of public lighting, the coordinator is connected to the control means of said lighting network. According to the variants, the autonomous unit may comprise one or more measuring means, in particular any type of sensor or probe, operating at low voltage, enabling it to perform point-by-point measurements on a network equipped with said autonomous units 20 in the purpose of communicating, in the same way as for the measurements of brightness, said measurements to the coordinator. It may be sensors measuring pollution, for example sound, humidity, temperature or other, the coverage of point-by-point measurements can be very dense and easy to implement. The autonomous unit 20 is independent of a f ilaire network, in particular of the power circuit for supplying electrical energy to the various light points of the public lighting, which does not cause overconsumption of the lighting network during the operation of the In addition, the measurements do not suffer any disturbance related to any interference on said power circuit during communication with the coordinator, as may be experienced by, for example, powerline systems.

According to the invention, as illustrated in FIGS. 1 and 2, each autonomous unit 20 has at least one measuring means 18, in particular means for measuring brightness, communication means 30, capable of communicating with the coordinator and / or another autonomous unit 20 and autonomous power supply means 38.

Preferably, an autonomous unit 20 comprises a sealed housing 36 in which are arranged:

communication means 30,

autonomous supply means 38, at least one measuring means 18,

synchronization means 58,

- and eventually,

storage means 32,

means for executing instructions 40, means for controlling an external unit.

In an autonomous unit 20, the autonomous power supply means 38 provide the energy required by the other components. According to one characteristic of the invention, the autonomous power supply means 38 comprise means for transforming an external renewable energy 42, in particular solar energy, into electrical energy and storage means 44 for said electrical energy. In addition or alternatively, the device could use wind power or any other renewable energy. Thus, the autonomous unit 20 operates thanks to renewable energies so as to register in the field of sustainable development and urban ecology. In the application relating to the management of public lighting, the means for transforming an external energy source 42, in particular a photovoltaic panel, transforming the solar energy into electrical energy, can be used as means for measuring brightness and means for detecting malfunction and lighting of a light point. As illustrated in Figure 2, each autonomous unit 20 is equipped with a housing 36 having an upper portion 48 and a lower portion 50 between which are provided sealing means 46, in particular a silicone seal. The upper portion 48 of the housing 36 comprises a transparent wall 52 behind which are positioned the means for transforming an external energy 42. To complete the sealing of the housing 36 and more particularly to ensure a durable seal, given the duration of life required, especially for a device intended to be installed on a public lighting network, a one-way valve 54 is disposed on one of the faces of the housing 36, the opening of said valve being towards the outside of the housing 36 After assembling the various components of the autonomous unit 20 and following the closure of the housing 36 with the provision of the sealing means 46 between the upper 48 and lower 50 parts, the autonomous unit 20 is heated to a substantially higher temperature. at the maximum temperature of use. This rise in temperature increases the pressure air inside said housing 36, and more particularly at a pressure greater than the operating pressure of the valve 54. This rise in temperature therefore has the effect of evacuating a portion of the air contained in the housing 36, which subsequently, while cooling, will be substantially under vacuum and thus reinforced sealing. This evacuation phenomenon can also be reiterated and therefore regenerate during the summer season for example. Advantageously, the housing 36 comprises fastening means 26 adapted to the support on which is fixed the autonomous unit 20. The housing 36 can take various forms, a spherical shape being preferably recommended for the discretion of the autonomous units 20. As the 3A and 3B, said housing 36 contains a printed circuit 56 comprising the electrical energy storage means 44, the communication means 30 of the autonomous unit 20, the synchronization means 58, as well as possibly the means for executing instructions 40 and storage means 32, calibration means 62, power supply regulation means 64, temperature measuring means 60, secondary communication means 68. allow the operation of the various elements located on the printed circuit 56, the voltage supplied by the electrical energy storage means 44 must be regulated in order to provide a stable supply to said various elements of the printed circuit board 56.

As such, the energy storage means 44 are relayed by the regulation means 64 of the power supply. Said regulation means 64 of the power supply are in particular made using a DC / DC converter.

According to the variants, calibration means 62 may be used to calibrate the value of the voltage supplied by the means for transforming an external energy 42, which voltage is directly proportional to sunshine. These calibration means 62 are in particular made using a voltage divider bridge.

The electrical energy storage means 44 are composed of a capacitor switching device 70 and protection means 72 of said capacitor switching device 70.

The protection means 72 of the capacitor switching device 70 are controlled by a control command from the means for executing instructions 40, a control command which allows the switching of said device between a serial circuit of the capacitor switching device 70, having at least two capacitors, and parallel mounting of said capacitor switching device 70.

The protection means 72 of said capacitor switching device 70 are made using low-voltage detection means and field-effect transistors, more particularly N-channel or P-channel MOSFETs, in order to avoid overloading. said capacitors when they have reached their charging voltage, the power supply of the capacitor switching device being cut off.

This capacitor switching device 70 furthermore has switching means, made by field effect transistors, more particularly of the N-channel or P-channel MOSFET type, referenced T8N, T8P and T2A in FIGS. 3A and 3B. Said switching means have, for the purposes of this capacitor switching device 70, particularly fast switching speeds, in particular to have the minimum of pressure drop across the capacitors. The operation of the capacitor switching device is illustrated in FIGS. AA and 4B. For the preferred embodiment of the standalone unit 20, the number of capacitors is set at two, but this capacitor switching device 70 may comprise more than one pair of capacitors of the moment that the charging voltage supplied by the means for transforming an external energy 42 is provided accordingly.

FIG. 4A represents the series circuit of the capacitor switching device 70. The switching means T8N and T8P being open and T2A closed, the capacitors C1 and CZ are fed in series by a voltage U, resulting from the transformation means of FIG. an external energy 42. This series assembly is intended to perform the charging of said capacitors C1 and C2. When the charging voltage is reached, the protection means 72 of said capacitor switching device 70 switch off the power supply from the means for transforming an external energy 42 and, as illustrated in FIG. 4B, the T2A switching means open, which causes the closing of the switching means T8N and T8P. The capacitor switching device 70 has stored the electrical energy, and the two capacitors C1 and C2 are now connected in parallel to discharge their capacity and start delivering a voltage V substantially equal to half of said voltage U , the regulation means 64 of the power supply.

The electrical supply thus produced provides the electrical power required by the other components, in particular the measuring means 18, the means for executing the instructions 40, in particular a microprocessor, and the synchronization means 58, in particular an integrated time clock circuit. Programmable real, storage means 32, including EEPROM type, the temperature measuring means 60, including a circuit incorporating a temperature probe, the communication means 30, including an ultra-high transceiver integrated circuit frequencies corresponding to the IEEE802.15.4 standard, called ZigBee, operating at low voltage, and secondary communication means 68, in particular an optical transceiver for transmitting and receiving information and instructions. The storage means 32, in particular of the EEPROM type, are used to store the information specific to each measurement point, whether it is information derived from brightness measurements, temperature measurements, or any other measurements. , as well as data sent to the means for executing the instructions 40. The data thus stored can be reused for the establishment of an ignition reference curve for example, or for the learning of the measurement means.

Learning means the establishment of a database of measurements obtained by the various measurement means available in an autonomous unit 20 and available in the storage means 32, this database making it possible to establish a map said measurements on a time scale for example being able to be hourly, daily, weekly or allowing to cross the different measurements between them and to deduce from them possible relations. The advantages provided by the network of autonomous units 20 are dependent on a communication protocol, more particularly radio, adapted to the low voltage operating mode of the autonomous units 20. Because of the autonomy of the autonomous units 20, this protocol of communication is at low level of energy consumption. This low power consumption is based on the programmable synchronization means 58 which define a time-stamped operation of the autonomous units 20, based on a periodic request / response method of each autonomous unit 20, this communication protocol therefore being time-stamped. Preferably, the synchronization means 58 are in the form of a real-time clock integrated circuit whose frequency deviations of the crystal oscillator due to temperature variations can be compensated, thereby obtaining a reliable time stamping. with negligible drift over time. In order to synchronize the autonomous units 20 with each other, the communication protocol provides a periodic synchronization time interval during which the autonomous units synchronize two by two thanks to the programmable synchronization means 58, the synchronization means 58 enabling the autonomous units to synchronize with each other or with the coordinator, and through their means of communication 30. The protocol is bidirectional in the sense that the transmission of the signal is performed downward then rising on the network of autonomous units 20. The protocol defines a communication method carried out so that, during the downward phase, the signal transmitted by the communication means 28 of the coordinator, in particular a radio transceiver, is retransmitted to the communication means 30 of a first signal. autonomous unit 20, in particular the one located the most upstream of the network close to the coordo nnateur, then successively autonomous unit 20 in autonomous unit down on the network, to the last autonomous unit 20 of said network, located the most downstream, and, during the rising phase succeeding a downward phase, the signal goes back the upstream downstream network, from autonomous unit 20 to autonomous unit, until returning to the coordinator. During a rising phase M or downward D and thanks to the synchronization means 58, the autonomous unit 20 knows when it should be in reception, referenced R in Figure 5. During this reception period R, the means of communication are listening and are therefore likely to receive a signal from a transmitter and the instructions it contains. By following the reception period R and after the end of the reception of the signal, the communication means in turn transmit the signal, during a transmission period EM, to the communication means of the autonomous unit being in a period of reception. During the reception period R of the downward phase D, the execution means 40 carry out the instructions transmitted in the signal, in particular measurements, then during the emission period EM of the rising phase M, they transmit the data corresponding to the instructions to the means of communication 30.

Thus, and as illustrated in FIG. 5, the protocol is bidirectional with beacons.

The protocol is tagged as each autonomous unit transmits a beacon, or message, to a specific EM transmission period, bearing the network identifier, the transmitter identifier, the number of the time slot , date and time. The beacon is the means used by each autonomous unit 20 to synchronize with another autonomous unit 20 or the coordinator, said synchronization being effected in pairs. The temporal accuracy of the emission period EM is essential to prevent sudden variations causing the stall of the tail of the network. Said accuracy of the emission period EM depends on the clock stability of each autonomous unit 20, this stability being obtained by compensating in temperature by the temperature measuring means 60 the high-precision clock defined by the synchronization means 58 programmable. To increase the data traffic that can pass, the communication protocol uses several signal transmission frequencies, a frequency however being reserved to synchronize or resynchronize the autonomous units 20 between them. This synchronization frequency is used to create a signaling link which is used to re-synchronize an autonomous unit 20.

In case of isolation of an autonomous unit 20, it performs its own search synchronization. An autonomous unit 20 declares itself isolated when it no longer sees a tag several times in a row. There are three modes synchronization search from self declaration of isolation. A quick mode that consists in remaining in the reception period for the isolated autonomous unit 20 after the rising phase M to find the signaling link signaling phase, the probability of finding the signaling beacon being directly related to the quality of the signal. Beyond the time of presence of the signaling link, since it is useless to continue the search, the isolated autonomous unit 20 then goes into the slow search mode which consists in waiting for the next reception transmission cycle to scan the semaphore channel in a time equivalent to that of the fast search. The last search mode is established at each time slot where an autonomous unit 20 having lost the channel attached thereto will perform a close sequence to the second of synchronization cycles for one minute to give an order of ideas. During the first identification, a child parent relationship is created between the autonomous unit 20 in research, called child, and the autonomous unit 20 or the coordinator, called said parent, who accepts it as part of the network. The parent enrolled in his means of memorizing 32 the coordinates of his new child. Similarly, the child inscribes in his means of storage 32 the coordinates of his parent. When a child is isolated, he / she performs a so-called orphan procedure to find his / her parent, the network connection procedure and the resynchronization procedure being based on the methods defined by the IEEE802.15.4 standard.

Beyond the orphan procedure, an autonomous unit 20 is completely isolated and can then erase the coordinates stored by the storage means 32 to perform a connection procedure to the network, this procedure involved in the case of the disappearance of the parent corresponding to a destruction or replacement of an autonomous unit 20. Attachment to a parent is a stable privileged relationship. There is no reason to change parents.

A parent standalone unit can accept multiple child standalone units as part of the manufacturing parameters. Each autonomous 20 child unit is identified separately. All stand-alone children's units listen to the same parent stand-alone unit during the same time interval. The different autonomous units 20 children of the same parent unit 20 then work on their own time interval and do not see each other. Of course, the invention is obviously not limited to the embodiment shown and described above, but covers all variants, particularly with respect to the shapes, dimensions and materials of the various elements.

Claims

An autonomous unit (20) incorporating at least one measuring means (18), comprising autonomous power supply means (38) comprising means for transforming an external energy (42) into electrical energy, in particular a photovoltaic panel using solar energy, and capable of integrating into a network of autonomous units and communicating by means of communication (30) the measured value or values, characterized in that it comprises storage means (44) said electrical energy comprising a capacitor switching device (70), at least two capacitors, protected by protection means (72).

2. autonomous unit according to claim 1, characterized in that the capacitor switching device (70) comprises switching means (T8N, T8P and T2A) switching between:

a series connection of capacitors C1 and C2, supplied in series by a voltage U, originating from the means for transforming an external energy (42), and a parallel connection of said capacitors C1 and C2, the protection means ( 72) cutting said power supply from the means for transforming an external energy (42).

3. autonomous unit according to any one of the preceding claims, characterized in that it comprises control means (64) of the power supply provided by the electrical energy storage means (44).

4. autonomous unit according to any one of the preceding claims, characterized in that it comprises calibration means (62) for calibrating the value of the voltage supplied by the means for transforming an external energy (42).

5. autonomous unit according to any one of the preceding claims, characterized in that it comprises synchronization means (58) to allow a time-stamped operation of said autonomous unit.

6. autonomous unit according to claim 5, characterized in that it comprises temperature measuring means (60) for adjusting the synchronization means (58) as a function of the measured temperature.

7. autonomous unit according to any one of the preceding claims, characterized in that it comprises a housing in which are arranged the constituent elements, said housing comprises a one-way valve (54) for having an air pressure inside the housing (36) less than the air pressure outside said housing (36).

8. Network comprising at least one autonomous unit (20) according to any one of the preceding claims and at least one coordinator capable of collecting the measured values.

9. Communication protocol for a network comprising at least one autonomous unit (20) according to any one of claims 1 to 7 and at least one coordinator, characterized in that it operates in a timestamped manner, the autonomous units synchronizing two to two, for transmitting a signal downward then rising on said network of autonomous units and in that each autonomous unit transmits a beacon to a given transmission period, carrying the network identifier, the identifier of the transmitter, the number of the time interval, the date and the time.