WO2020064101A1

WO2020064101A1 - Radio sensor node

Info

Publication number: WO2020064101A1
Application number: PCT/EP2018/076156
Authority: WO
Inventors: Christoph Armschat; Uwe WEIGT
Original assignee: Siemens Aktiengesellschaft
Priority date: 2018-09-26
Filing date: 2018-09-26
Publication date: 2020-04-02
Also published as: EP3830804B1; ES2963492T3; EP3830804A1

Abstract

The invention relates to a radio sensor node (1). The radio sensor node (1) comprises a sensor unit (5) for detecting a measured variable and outputting an analogue electric sensor signal (S), an energy harvesting unit (13) for harvesting energy from the sensor signal (S), a signal processing unit (11) for generating a transmission signal (T) from the sensor signal (S) and a radio unit (17) for transmitting the transmission signal (T) as a radio signal. The sensor signal (S) can be supplied alternately to the energy harvesting unit (13) and to the signal processing unit (11).

Description

description

Radio sensor node

The invention relates to a radio sensor node.

A radio sensor node transmits measurement data acquired by means of a sensor to one wirelessly by means of radio waves

Receiver . Radio sensor nodes are often heavy

accessible or dangerous places where cabling, replacement and / or maintenance of the sensor is not possible or very expensive. Therefore, a radio sensor node is usually special

Requirements with regard to its robustness, durability, radio range and self-sufficient energy supply. These requirements often make it particularly difficult to implement a radio sensor node in a small size. Furthermore, the energy supply often proves to be problematic. On the one hand, batteries make it self-sufficient

Energy supply, on the other hand, have only one

limited lifespan. However, in the case of radio sensor nodes in particular, it is often difficult or impossible to replace a battery. Economical energy consumption can extend the lifespan of a battery, but on the other hand it can cut back on the transmission power and / or the operating times of the radio sensor node.

The invention has for its object to provide an improved radio sensor node and a method for operating it, in particular for use in a

Environment exposed to high electromagnetic loads.

The object is achieved according to the invention by a radio sensor node with the features of claim 1 and a method with the features of claim 14.

Advantageous embodiments of the invention are the subject of the dependent claims. A radio sensor node according to the invention comprises one

Sensor unit for acquiring a measured variable and outputting an analog electrical sensor signal, an energy harvesting unit for harvesting energy from the sensor signal, a

Signal processing unit for generating a

Transmission signal from the sensor signal and a radio unit for transmitting the transmission signal as a radio signal. The sensor signal can be fed alternately to the energy harvesting unit and the signal processing unit.

The invention therefore provides for the electrical sensor signal of the sensor unit of a radio sensor node

To use the power supply of the radio sensor node. For this purpose, the radio sensor node assigns an energy harvesting unit

Harvesting energy (especially electrical energy), so-called energy harvesting, from the sensor signal. The invention provides that the sensor signal alternately

Signal processing unit for generating a

Transmission signal from the sensor signal and the

Supply energy harvesting unit for harvesting energy. The invention takes advantage of the fact that a radio sensor node generally does not continuously process and send a sensor signal as a radio signal, but rather the majority of the time in one

Sleep mode to save energy. This

Sleep mode is used according to the invention to harvest energy from the sensor signal. The energy harvesting unit can

in particular also be referred to as an energy generation unit. The energy harvesting unit can also be used as

Energy recovery unit for the recovery of electrical

Energy from the sensor signal can be designated; the

Energy harvesting unit is used to obtain energy from the sensor signal. These are in particular:

electrical power .

An embodiment of the invention provides that the

Signal processing unit an averaging circuit for

Generate the transmission signal as an average of the a rectifier circuit rectified sensor signal. In this embodiment of the invention, a complex evaluation of the sensor signal is carried out in the

Radio sensor node omitted and instead as

Transmission signal is only an average of the

rectified sensor signal generated. Compared to an evaluation of the sensor signal in the radio sensor node, this generation of a transmission signal is special

energy saving. The energy intensive evaluation of the

In this case, the transmission signal occurs to a user of the radio sensor node. To evaluate the transmission signal, a calibration curve is measured in a test field of the manufacturer of the radio sensor node, for example, which represents the transmission signal as a function of the measured variable and is made available to a user of the radio sensor node.

Alternatively, the signal processing unit as

Transmission signal generates an effective value of the sensor signal. This alternative embodiment of the invention to the aforementioned embodiment is then preferred

used when the radio sensor node has sufficient energy to calculate the effective value due to energy harvesting.

In a further embodiment of the invention, the radio sensor node has a signal input to which the sensor signal is fed, and a switchover logic through which the

Signal input is alternately connectable to the energy harvesting unit and the signal processing unit. This embodiment of the invention realizes the alternating

Feeding of the sensor signal to the signal processing unit and the energy harvesting unit by a switching logic that alternately connects the signal input to the signal processing unit and the energy harvesting unit.

Another embodiment of the invention provides a

Voltage limiting unit to protect the signal input from Surges before. This embodiment of the invention advantageously increases the robustness of the signal input against

Surge voltages. These can be caused by direct coupling or by inductive coupling

(For example, from power surges in nearby passages

Current paths) or by capacitive coupling, which

especially in the vicinity of high-voltage systems

may occur .

Another embodiment of the invention provides that the signal input from a sensor node housing

Radio sensor node has led out contacts. This makes contacting the signal input from the outside

enables. Furthermore, one of the contacts can be used to open the contact outside of the radio sensor node

Ground potential.

A further embodiment of the invention provides that the radio sensor node has a lower plastic

Has permittivity encapsulated sensor node housing.

As a result, the radio signals of the radio unit are advantageously hardly attenuated by the sensor node housing.

Further refinements of the invention provide that the radio unit has an antenna, for example a ring antenna with one or more windings, and is designed to alternately transmit the radio signal with the antenna and from one in an environment of the radio sensor node

Harvest existing magnetic field inductively and / or a magnetic field strength in an environment of

Detect radio sensor node existing magnetic field. These refinements of the invention therefore provide that the antenna of the radio sensor node not only sends radio signals, but also for harvesting energy from a magnetic field and / or for detecting a magnetic field strength

Magnetic field in the vicinity of the radio sensor node

use. As a result, the antenna is also advantageous Power supply of the radio sensor node and / or as

Magnetic field sensor used.

A further embodiment of the invention provides that the radio sensor node is arranged on an electrically conductive surface and one with the electrically conductive surface

Surface electrically connected ground connection. In addition, the radio sensor node can be an electromagnetic one connected to the electrically conductive surface

Have shielding. This embodiment of the invention uses an electrically conductive surface on which the radio sensor node is arranged for potential connection of the radio sensor node and an electromagnetic shielding of the radio sensor node.

In a further embodiment of the invention, the radio sensor node has an energy storage unit for storing energy. The energy storage unit has

for example a super capacitor and / or one

Accumulator on. If the energy storage unit

Has supercapacitor and an accumulator, the accumulator is, for example, only charged when the

Supercapacitor is charged to a nominal voltage. These refinements of the invention make it possible, in particular, to store the energy harvested from the sensor signal if the harvested energy is not currently available

Power supply of the radio sensor node is required. The use of a supercapacitor and an accumulator combines the quick loading and unloading of one

Supercapacitor with the higher capacitance

Accumulator. In addition, supercapacitors have higher ones

Lifetimes as accumulators, so that the supercapacitor can be used for a long time if the lifespan of the

Accumulator has already expired. Loading the

The battery only takes place after the supercapacitor has been charged to a nominal voltage. This is achieved by means of a decoupling circuit. If the accumulator becomes defective after a few years of operation, it does not build up any voltage more on. The decoupling circuit then avoids discharge of the supercapacitor by the defective one

Accumulator so that the radio sensor node can continue to be supplied with energy from the supercapacitor. The parallel installation of the supercapacitor and the

The battery has the advantage that - depending on the energy harvest and cycle times - in the first years of using the

Radio sensor nodes can process significantly more measurement and arithmetic tasks than with the sole supply from the supercapacitor.

In the method according to the invention for operating a radio sensor node according to the invention, the measurement variable is accordingly detected with the sensor unit and that

Sensor signal output, the sensor signal is alternately fed to the energy harvesting unit and the signal processing unit, with the signal processing unit

Transmission signal generated from the sensor signal, the transmission signal is sent as a radio signal with the radio unit, and energy is harvested from the sensor signal with the energy harvesting unit.

The above-described characteristics, features and advantages of this invention, as well as the manner in which they are achieved, will be more clearly understood in the

Relation to the following description of

Embodiments related to the

Drawings are explained in more detail. Show:

1 shows a block diagram of a radio sensor node,

2 shows a circuit diagram of a rectifier circuit and an averaging circuit for generating a

Transmission signal,

3 shows a circuit diagram of an energy storage unit. Corresponding parts are shown in the figures

the same reference provided calibrate _Z.

FIG. 1 shows a block diagram of an exemplary embodiment of a radio sensor node 1 according to the invention

Radio sensor node 1 comprises a sensor node housing 3, a sensor unit 5, a signal input 7, a switching logic 9, a signal processing unit 11, a

Energy harvesting unit 13 with an energy storage unit 15, a radio unit 17 and an electromagnetic one

Shield 19.

With the sensor unit 5, a measured variable is recorded and an analog electrical representative of the measured variable

Sensor signal S output at signal input 7. The

Sensor unit 5 has, for example, a temperature sensor for detecting a temperature as a measured variable, but can also have a sensor for detecting another measured variable. The sensor signal S is one of the

Sensor unit 5 generated electrical voltage, for example a voltage in the single-digit volt range.

The switching logic 9 connects the signal input 7

alternately with the signal processing unit 11 and the energy harvesting unit 13 and thus alternately carries the sensor signal S to the signal processing unit 11 and

Energy harvesting unit 13 too. For example, the

Switchover logic 9 low-loss for this purpose

Semiconductor switch, for example metal-oxide-semiconductor field effect transistors (MOSFET), and a control unit for controlling the semiconductor switch.

The signal processing unit 11 generates from the

Sensor signal S a transmission signal T. For example, the signal processing unit 11 generates as

Transmission signal T an average of the rectified sensor signal S, see Figure 2. FIG. 2 shows an example of a circuit diagram of a rectifier circuit 21 and an averaging circuit 23 for generating the transmission signal T as an average of the rectified sensor signal S. The

Rectifier circuit 21 is designed as a bridge rectifier circuit formed by four diodes 25. The averaging circuit 23 is connected downstream of the rectifier circuit 21 and has an inductance 27, one

Averaging capacitor 29 and one to that

Averaging capacitor 29 connected in parallel

Averaging resistance 31. In Figure 2 it is assumed that the signal input 7 via the switching logic 9 with the

Signal processing unit 11 is connected, the

Switching logic 9 is not shown in Figure 2. Of the

Signal input 7 is protected from overvoltages by a voltage limiting unit 33 formed by a varistor. For example, the voltage limiting unit 33 is designed for an incoming, decaying over 5 ms

Limit surge voltage with a voltage peak of 100 V to 15 V to 20 V. The transmission signal T is a voltage applied to the parallel connection of the averaging capacitor 29 and the averaging resistor 31. To evaluate the transmission signal T generated in this way, a calibration curve is measured in a test field of the manufacturer of the radio sensor node 1, which represents the transmission signal T as a transmission function of the measured variable and is made available to a user of the radio sensor node 1. Ideally, a time characteristic typical for the measurement signal is selected for the determination of the transfer function in the test field, which roughly corresponds to the expected measurement variable on the system.

The version of the shown in Figure 2

Signal processing unit 11 for generating the

Transmission signal T as an average of the

rectified sensor signal S requires no complex evaluation of the sensor signal S in the radio sensor node 1 and is therefore particularly energy-saving. If sufficient harvested energy is available, the

Instead, signal processing unit 11 is more complex

be executed. For example, the

Signal processing unit 11 have an integrated circuit which as a transmission signal T one

RMS value of the sensor signal S is calculated.

For example, the effective value is formed over a time period of approximately 100 ms with a sampling frequency of more than 3 kHz. With larger radio sensor nodes 1, the

Measured value _V elaboration several signals include, contain a Messwertspeieher and include a more complex processing.

The energy harvesting unit 13 is designed to harvest energy from the sensor signal S, which is used to supply energy to the radio sensor node 1. The

Energy harvesting unit 13 has an energy storage unit 15, which is designed to store energy when the harvested energy is not currently required to supply energy to the radio sensor node 1.

FIG. 3 shows a circuit diagram of an exemplary embodiment of the energy storage unit 15, it being assumed that the energy storage unit 15 is connected to the signal input 7 via the switchover logic 9 and, as in FIG. 2, the switchover logic 9 is not shown. The

Energy storage unit 15 of this exemplary embodiment has a supercapacitor 35, an accumulator 37

Overflow unit 39 with an integrated overload protection and a blocking diode 41 and is via a

Rectifier circuit 21 connected to the signal input 7, wherein the rectifier circuit 21 can match the rectifier circuit 21 shown in FIG. 2 or can be implemented separately. The supercapacitor 35 and the accumulator 37 are decoupled by the overflow unit 39, but in principle are connected in parallel to one another. The

Overflow unit 39 directs excess energy into the

Accumulator 37 when the supercapacitor 35 is on a Nominal voltage is charged, that is, the accumulator 37 is only charged when the supercapacitor 35 is already charged to the nominal voltage. When the accumulator 37 reaches the end of its service life, the

Energy storage unit 15 only with the

Super capacitor 35 operated.

The radio unit 17 has an antenna 43 with which the transmission signal T is transmitted as a radio signal. The antenna 43 is designed as a ring antenna with one or more turns. The radio unit 17 is preferably also designed to alternately transmit the radio signal with the antenna 43 and to inductively harvest energy and / or a magnetic field strength in one from an existing magnetic field in an environment of the radio sensor node 1

Detect the surroundings of the radio sensor node 1 existing magnetic field.

The electromagnetic shield 19 is as one

low-inductance conductor loop designed for

Shielding electromagnetic fields in the

Sensor node housing 3 runs around the electrical and electronic components of the radio sensor node 1.

The signal input 7 has contacts 44, 45 led out of the sensor node housing 3, via which the

Signal input 7 can be contacted from the outside. About the

Contacts 44, 45 can be an external one, for example

Sensor unit 5 are connected to the signal input 7 in order to supply the signal input 7 with a sensor signal S output by the external sensor unit 5. A lead-out contact 45 and the electromagnetic shield 19 are led out of the sensor node housing 3

Ground connection 47 connected. The ground connection 47 is electrical with an electrically conductive surface 49

connected to which the radio sensor node 1 is arranged. Optionally, the energy harvesting unit 13 can be removed from the

Sensor node housing 3 lead out additional contacts 51, 52 harvest energy. The sensor node housing 3 is in a plastic

low permittivity so that the radio signals of the antenna 43 are hardly attenuated.

The radio sensor node 1 is, for example, in a

environment exposed to high electromagnetic loads.

Although the invention in detail by preferred

Exemplary embodiments have been illustrated and described in more detail, the invention is not restricted by the examples disclosed and other variations can be derived therefrom by the person skilled in the art without the scope of protection of the

Leaving invention.

Reference list

1 radio sensor node

3 sensor node housings

5 sensor unit

7 signal input

9 switching logic

11 signal processing unit

13 energy harvesting unit

15 energy storage unit

17 radio unit

19 electromagnetic shielding

21 Rectifier circuit

23 Averaging circuit

25 diode

27 inductance

29 averaging capacitor

31 averaging resistance

33 voltage limiting unit

35 supercapacitor

37 accumulator

39 overflow unit

41 blocking diode

43 antenna

44, 45 lead out contact

47 Earth connection

49 electrically conductive surface

51, 52 additional contact

S sensor signal

T transmission signal

Claims

1. radio sensor node (1), comprising

a sensor unit (5) for detecting a measured variable and outputting an analog electrical sensor signal (S),

- an energy harvesting unit (13) for harvesting energy from the sensor signal (S),

- A signal processing unit (11) for generating a transmission signal (T) from the sensor signal (S) and

- A radio unit (17) for transmitting the

Transmission signal (T) as a radio signal,

- The sensor signal (S) alternately the

Energy harvesting unit (13) and the

Signal processing unit (11) can be fed.

2. radio sensor node (1) according to claim 1, wherein the

Signal processing unit (11) has an averaging circuit (23) for generating the transmission signal (T) as an average value of the sensor signal (S) rectified with a rectifier circuit (21).

3. radio sensor node (1) according to claim 1, wherein the

Signal processing unit (11) generates an effective value of the sensor signal (S) as the transmission signal (T).

4. radio sensor node (1) according to one of the preceding

Claims with a signal input (7), which the

Sensor signal (S) is supplied, and with a

Switching logic (9) through which the signal input (7)

alternately with the energy harvesting unit (13) and the

Signal processing unit (11) can be connected.

5. radio sensor node (1) according to claim 4 with a

Voltage limiting unit (33) to protect the

Signal input (7) before overvoltages.

6. radio sensor node (1) according to claim 4 or 5, wherein the signal input (7) from a sensor node housing (3) of Radio sensor node (1) leads out contacts (44, 45).

7. radio sensor node (1) according to one of the preceding

Claims with one in a plastic with lower

Permittivity encapsulated sensor node housing (3).

8. radio sensor node (1) according to one of the preceding

Claims, wherein the radio unit (17) has an antenna (43) and is designed to alternately transmit the radio signal with the antenna (43) and to inductively harvest energy from a magnetic field present in an environment of the radio sensor node (1).

9. radio sensor node (1) according to one of the preceding

Claims, wherein the radio unit (17) has an antenna (43) and is designed to alternately transmit the radio signal with the antenna (43) and one

Magnetic field strength in an environment of

Detect radio sensor node (1) existing magnetic field.

10. radio sensor node (1) according to one of the preceding

Claims of an electrically conductive

Surface (49) is arranged and one electrically connected to the electrically conductive surface (49)

Has ground connection (47).

11. A radio sensor node (1) according to claim 10, which is connected to the electrically conductive surface (49)

has electromagnetic shielding (19).

12. radio sensor node (1) according to one of the preceding

Claims with an energy storage unit (15) for

Storing energy, the

Energy storage unit (15) has a supercapacitor (35) and / or an accumulator (37).

13. radio sensor node (1) according to claim 12, wherein the

Energy storage unit (15) has a supercapacitor (35) and an accumulator (37) and the accumulator (37) is charged to a nominal voltage only after the supercapacitor (35) has been charged.

14. A method for operating a radio sensor node (1) according to any one of the preceding claims, wherein

- With the sensor unit (5) the measured variable is recorded and the sensor signal (S) is output,

- The sensor signal (S) alternately the

Energy harvesting unit (13) and the

Signal processing unit (11) is supplied,

- With the signal processing unit (11)

Transmission signal (T) is generated from the sensor signal (S),

- With the radio unit (17), the transmission signal (T) is sent as a radio signal and

- With the energy harvesting unit (13) energy from the

Sensor signal (S) is harvested.