Patent Description:
Radio-frequency identification (RFID) technology uses electromagnetic fields to automatically identify and track tags attached to objects. The tags often contain electronically stored information such as an identification number. While active tags have a local power source (such as a battery) and may operate hundreds of meters from the RFID reader, passive tags collect energy from a nearby RFID reader's interrogating electromagnetic field and therefore has a reduced range. Unlike a barcode, the tag need not be within line of sight of the reader, so it may be embedded in the tracked object.

RFID tags are used in many industries. For example, an RFID tag attached to a work tool such as a cut-off disc can be used to identify the type of disc attached to the tool.

<CIT> discloses an example use of RFID technology with rotatable work tools.

Embedding wireless identification tags into metallic objects, such as a cut-off disc, is problematic since the high electrical conductivity of the metal surrounding the hole in which the tag is placed generates opposing magnetic flux that cancels out the magnetic flux through the hole. This effect, described by the Maxwell-Faraday equation, complicates interacting with the tag by a reader.

<CIT> describes a communication terminal and information processing system that can extend the range between a wireless dentification tag and a corresponding reader/writer.

<CIT> show work tools with embedded wireless identification tags.

<CIT> discloses abrasive work tools with embedded wireless identification tags.

<CIT> describes smart accessories for power tools.

<CIT> describes a circular saw blade balancing tool.

Despite the work done to-date, there is a need for improved wireless identification tag systems suitable for embedding into electrically conductive surfaces, such as a metal work tool.

It is an object of the present disclosure to provide wireless identification tags, readers, and systems where the tags are suitable for embedding into electrically conductive surfaces. This object is at least in part obtained by a wireless identification tag for embedding into an electrically conductive surface of a rotatable work tool. The tag comprises at least a first and a second inductive planar loop having corresponding first and second terminals. The first inductive planar loop and the second inductive planar loop are arranged in relation to a common plane. The first inductive planar loop and the second inductive planar loop are also arranged to cover different areas of the common plane, where each area on the common plane is associated with a respective polarity of the magnetic flux normal to said plane.

This way the wireless tag is not 'quenched' by the electrically conductive surface. Rather, the tag is matched to a magnetic flux with varying polarity.

Consequently, there is provided a wireless identification tag suitable for embedding into electrically conductive surfaces.

The rotatable work tool may, e.g., be a cut-off disc or a drill, such as a core drill.

According to aspects, the areas are separable by a line drawn on the common plane or by an arc of a circle having a radius drawn on the common plane. This approach to separation is particularly suitable for rotatable work tools.

According to aspects, the wireless identification tag comprises three or more inductive planar loops, wherein each inductive planar loop is arranged to cover a different area of the common plane, where each area is associated with a respective polarity of the magnetic flux normal to said plane. This way a wide variety of geometries can be used when embedding the tag into the electrically conductive surface. A tag thus matched to a magnetic field with varying flux polarity provides improved performance in terms of both inductive coupling and communication ability with respect to a tag reader.

According to aspects, the wireless identification tag comprises a connecting network configured to serially connect the first and the second inductive planar loops, thereby increasing a total voltage induced by the first and the second inductive planar loop in response to changes in a magnetic flux. This improves wireless identification tag communication range and energy transfer ability with respect to the reader, which is an advantage. Also, the physical footprint of the tag can be reduced since the efficiency is increased, which is an advantage.

According to aspects, the wireless identification tag comprises a connecting network configured to connect the first and the second inductive planar loops in parallel, thereby reducing a source resistance associated with the wireless identification tag. A reduced source resistance may be advantageous in certain applications.

According to aspects, the wireless identification tag comprises an identification circuit connected to the first inductive planar loop and to the second inductive planar loop. The identification circuit is arranged to modulate a load on the terminals of a circuit formed by the connection of the first inductive planar loop and the second inductive planar loop, thereby providing an inductive communication channel to a wireless identification tag reader. This way a wireless identification tag system is formed that allows communication between the tag and a corresponding tag reader in an efficient manner.

According to aspects, the identification circuit is arranged to be powered via the first and second inductive planar loops. By powering the identification circuit via the inductive loops, there is no need for a dedicated power source on the tag, such as a battery or the like, which is an advantage.

According to aspects, the identification circuit is arranged to store identification data. This enables, e.g., detecting what type of tool that is currently in use, and verifying that the tool is the correct one for the present application. The identification data also simplifies inventory management and the like.

According to aspects, the identification circuit is arranged to determine a temperature value. This enables an operator to read out temperature data and to, e.g., determine if a tool has been subject to overheating or the like. Also, overheating may be detected during tool use and a warning signal may be issued to the operator who may cease operation.

According to aspects, the identification circuit is arranged to determine an acceleration value. By determining acceleration value, a plurality of applications is enabled, which applications will be discussed in the following.

According to some other aspects, the identification circuit is arranged to receive data from the wireless identification tag reader, and to store the data. This enables, e.g., the reader, or a control unit connected to the reader, to measure operating time for a given tool, and to update an operating time parameter of the tool. A user can then read out the operating time parameter and thereby obtain information about how long a given tool has been used. The reader and/or control unit may also determine one or more operating conditions and store this information in the tool, by the identification circuit. The operating conditions may, e.g., comprise a user identity or authorization code, a time of day, a day of the week, and the like.

There are also disclosed herein wireless identification tag readers, wireless identification tag systems, blade guards, work tools and applications associated with at least some of the above-mentioned advantages. There is furthermore disclosed herein control units, computer programs, computer readable media, computer program products, and vehicles associated with the above discussed advantages.

There is furthermore disclosed herein a wireless identification tag for embedding into a rotatable work tool. The tag comprises at least a first inductive loop, an energy storage device, processing circuitry, and a radio frequency transceiver. The wireless identification tag is arranged to harvest electrical energy from a time varying magnetic flux by the first inductive planar loop and to store the electrical energy in the energy storage device. The processing circuitry and the radio frequency transceiver are arranged to be powered by the energy storage device. The energy storage device may, e.g., be a capacitor or a battery.

Thus, advantageously, there is no need for battery replacement or other external power source in the tag, since the tag harvests energy for its operation from the time varying magnetic flux. This time varying magnetic flux may be obtained, e.g., by arranging one or more permanent magnets along a rotational path of the wireless identification tag, e.g., in connection to a blade guard or the like. The radio frequency transceiver allows for wireless linkage between the tag an, e.g., a control unit, thereby avoiding complicated and costly wiring comprising a dedicated wireless tag reader.

The wireless identification tag may further comprise the identification circuit discussed above; in which case the identification circuit can be communicatively coupled to an exterior unit via the radio frequency transceiver. The identification circuit application discussed above are therefore enabled also here.

A blade guard comprising one or more permanent magnets arranged to power a wireless identification tag arranged embedded in a rotatable work tool is also disclosed herein. The permanent magnets may be arranged in relation to a circular arc centered at a rotational center of the rotatable work tool. The permanent magnets may be arranged with alternating polarity along the circular arc.

There is furthermore disclosed herein construction equipment comprising a wireless identification tag, a blade guard, and a control unit arranged to communicate with the wireless identification tag via radio link.

The present disclosure will now be described in more detail with reference to the appended drawings, where.

<FIG> shows construction equipment <NUM> for cutting hard materials such as concrete and stone by a work tool <NUM>, here exemplified by a cut-off disc.

The work tool <NUM> may be in the form of a blade, such as a diamond blade comprising cutting segments with diamonds arranged along a periphery of the blade.

The tool <NUM> is made of metal, which means that its surface <NUM> is electrically conductive. The work tool <NUM> rotates in direction D about a center of rotation C. The direction D is shown as a 'down-cut' direction in <FIG>, however, 'up-cut' operation where the work tool <NUM> rotates in the opposite direction is also possible. <FIG> and <FIG> show similar equipment <NUM>, <NUM>.

Construction equipment <NUM>, <NUM>, <NUM> such as the cut-off tool shown in <FIG> and <FIG>, <FIG> are known in general and will not be discussed in more detail herein.

With reference to <FIG> and <FIG>, the work tool <NUM> comprises a wireless identification tag <NUM> arranged embedded into the electrically conductive surface <NUM>. The wireless identification tag <NUM> may be embedded in a circular hole cut in the surface <NUM>. The circular hole may be a laser-cut hole extending through the work tool <NUM>. Alternatively, the wireless identification tag may be embedded in a recess formed in the work tool, i.e., not a hole though the tool.

The tag <NUM> is arranged at a radial distance R from a center of rotation C of the work tool, which means that it will move along a circular arc <NUM> with radius R when the work tool <NUM> is in use.

The tag <NUM> is preferably arranged at a radial distance R below two thirds of the radius of the work tool <NUM>. For instance, if the radius of the work tool <NUM> is <NUM>,<NUM>, then the tag <NUM> should preferably be placed at a radial distance below <NUM>.

According to aspects, the tag <NUM> is preferably arranged at a radial distance R above one third of the radius of the work tool <NUM>.

Placing the tag too close to the edge of the rotatable work tool may cause the tag to overheat. However, some measurements of, e.g., tool temperature are more accurate if obtained close to the edge.

The larger the radial distance R the larger the rotational velocity, meaning that less time is available for powering and reading the tag <NUM> by the reader <NUM>.

Preferably, the wireless identification tag <NUM> is arranged away from a blade tensioning zone.

<FIG> also shows a work tool <NUM> comprising a wireless identification tag <NUM>. The two tags <NUM>, <NUM> differ in the way they are supplied with electrical energy and in how data stored on the tag is accessed, as will be made clear below where <FIG> is discussed in more detail. Other than the differences in how the tags are powered and in how data is read out from the tags, they are similar and support the same type of applications. In particular, the two tags <NUM>, <NUM> can be used for the same purposes with the same technical effects and are therefore associated with the same advantages. In particular, the identification circuits and applications discussed below can be implemented on any of the wireless identification tags <NUM>, <NUM> discussed herein.

Consequently, there is disclosed herein a work tool <NUM>, wherein a wireless identification tag <NUM>, <NUM> is configured to rotate about a center of rotation C during operation of the work tool.

With reference to <FIG>, each revolution of the work tool <NUM>, the wireless identification tag <NUM> passes a wireless identification tag reader <NUM> arranged on a blade guard <NUM> of the construction equipment <NUM>. The reader <NUM> is aligned with the tag <NUM> in the sense that it is arranged on the circular arc <NUM> at the same radial distance R from the center of rotation C as the tag, such that the tag passes more or less directly under the reader each revolution. The construction equipment discussed herein may be hand-held construction equipment or other types of construction equipment, including more heavy types of machinery such as floor saws, floor grinders, and the like. The rotatable work tool <NUM> may, e.g., be a cut-off disc or a drill, such as a core drill. It is appreciated that the wireless identification tags, readers, and systems discussed herein are applicable to a wide range of work tools, not just rotatable work tools.

<FIG> also shows a separate reader device <NUM> which may be in the form of, e.g., a smartphone, a tablet, or the like. The separate reader device <NUM> may be used to interface with the wireless identification tag <NUM> to, e.g., read out data from the tag or to write data onto a tag memory. The separate reader device <NUM> may also be used to configure the wireless identification tag <NUM>.

<FIG> shows a work tool <NUM> similar to the work tool in <FIG>. However, in <FIG>, the reader <NUM> is connected to a separate charging circuit <NUM> configured to harvest energy from one or more permanent magnets <NUM> arranged on the work tool <NUM>. The harvested energy may then be stored in an energy storage device <NUM> such as a rechargeable battery. The one or more permanent magnets <NUM> are arranged at a radial distance R' from a center of rotation C of the work tool <NUM>. The radial distance R' is preferably different from the radial distance R so as to not interfere with the tag-reader inductive connection. However, the reader <NUM> may be arranged to detect passage of the one or more permanent magnets in order to, e.g., synchronize reader operation. This is possible since there will be a fixed time duration between the permanent magnets <NUM> passing the reader <NUM> and the wireless tag <NUM> passing the reader.

The reader <NUM> in <FIG> is optionally arranged to communicate with a control unit <NUM> via wireless link <NUM> by a radio frequency transceiver <NUM>. The reader may also communicate with the remote server <NUM>, and perhaps also with the separate reader device <NUM> configured to read out data from the system. The separate reader device <NUM> may be comprised in, e.g., a smartphone, tablet or the like.

According to an example, a diameter Q of the wireless identification tag <NUM> is between <NUM>-<NUM>, and preferably about <NUM>. The radial length L of the reader <NUM> approximately mid-point as indicated in <FIG> is between <NUM>-<NUM>, and preferably about <NUM>, corresponding to one radian at the mounted radial distance from the center C.

The wireless identification tag <NUM> and the wireless identification tag reader <NUM> are comprised in a wireless identification tag system that enables functions such as identifying the type of work tool <NUM> attached to the construction equipment <NUM>, and gathering data about tool use in the tag, which data can then be wirelessly accessed by the reader <NUM>, and fed, e.g., to a control unit <NUM> in the construction equipment <NUM> or to a remote server <NUM>. Several different applications where the wireless identification tag system <NUM>, <NUM> can be used will be described below. For instance, sensors such as inertial measurement units (IMU), temperature sensors, shock sensors, and vibration sensors can be arranged in connection to the wireless identification tag <NUM>, and data from these sensors can be accessed via the reader <NUM>.

According to some aspects, the control unit <NUM> is communicatively coupled to the remote server <NUM> via wireless link <NUM>.

The remote server <NUM> may, e.g., be configured for fleet management of a collection of work tools <NUM>. The remote server may keep inventory based on wireless identification tag <NUM> identifier data and monitor the tools in the inventory based on sensor output from the tags <NUM>. A number of applications involving the wireless identification tag <NUM>, <NUM> the reader <NUM>, <NUM> and the remote server <NUM> will be discussed below.

Some RFID technologies use electromagnetic induction between two loop antennas located within each other's near field, effectively forming an air-core transformer, for communication. Such systems often operate within the globally available and unlicensed radio frequency ISM band around <NUM>. Theoretical working distance with compact standard antennas is up to <NUM> but the practical working distance is about <NUM>. In a passive mode of operation, an initiator device provides a carrier field and a target device answers by modulating the existing field. In this mode, the target device may draw its operating power from the initiator-provided magnetic field, thus effectively making the target device a transponder. The target device corresponds here to the wireless identification tag <NUM> and the initiator device corresponds to the wireless identification tag reader <NUM>.

The present system <NUM>, <NUM> may operate according to this electromagnetic induction principle of communication, thus, as the tag <NUM> passes under the reader <NUM>, the two come into range of each other for a short time duration. The tag is the first powered up, drawing energy from the reader via the inductive coupling, and then modulates the field in order to transfer information to the reader, such as an identification number or other data. This type of communication is known in general and will therefore not be discussed in more detail herein.

In physics, specifically electromagnetism, the magnetic flux through a surface is the surface integral of the normal component of the magnetic flux passing through that surface. The SI unit of magnetic flux is the weber (Wb), and the Centimetre-Gram-Second (CGS) unit is the Maxwell. Magnetic flux is usually measured with a known flux-meter, which contains measuring coils and electronics, that evaluates the change of voltage in the measuring coils to calculate the measurement of time varying magnetic flux.

With reference to <FIG>, RFID tags operating according to the induction principle of communication described above is hampered, or quenched, by nearby electrically conductive surfaces <NUM>. For a perfect electrical conductor with a hole or aperture <NUM> enclosed by the surface <NUM>, the total magnetic flux through the hole will always be constant. This is a direct effect of the Maxwell-Faraday equation: <MAT>.

The closed line integral along the edge <NUM> of the aperture <NUM> will be zero because there cannot exist an electric field in a perfect conductor. This means that the change in total flux through the hole over time also is zero. , if the magnetic flux through the hole was zero at one point in time it will always be zero.

Note in <FIG> how (assuming a homogenous applied field) the normal component of the flux (B · ez) is inverted close to the edge of the circular hole <NUM>. a tag <NUM> with a coil antenna along the very edge of the hole would have zero net flux.

However, a smaller coil centred in the hole would have a net flux which would give an induced E-field. This finding suggests that there is an optimum size of the tag antenna in relation to the diameter of the hole, as clearly the total flux goes towards zero when the surface area of the Tag S → <NUM>.

With reference to <FIG>, consider now a magnetic flux inside the perimeter <NUM> of the hole <NUM> that is inverted along the edge of the hole. Inside the hole two open loops are placed, an inner loop denoted A and an outer loop denoted B.

Herein, in line with convention, a dot <NUM> represents a vector going outwards while a cross <NUM> represents a vector in the opposite direction, i.e., going inwards. The dot schematically <NUM> shows an arrow approaching a viewer while the cross schematically illustrates an arrow <NUM> seen moving away from the viewer.

The voltage VA is the voltage induced in loop A and the voltage VB is the voltage induced in loop B. Connecting the loops A and <NUM> in series so that VAB = <NUM> VA = <NUM> VB both the inward and outward flux through the hole is used. If more inductance is required by the tag both loop A and loop B can be made with more than one turn and the same principle applies.

With reference to <FIG>, the above described principle also applies to non-circular, and non-symmetric apertures formed in electrically conductive surfaces. <FIG> shows an irregular hole <NUM> defined by a hole boundary <NUM>. The magnetic flux has a first polarity, here shown as upwards in regions 730a, 730b, and 730c, while the rest of the aperture <NUM> is associated with a magnetic flux of opposite polarity, here shown as downwards.

It is appreciated that voltage and potential are relative concepts which can be measured with respect to different reference frames. The concept of induced voltage and potential is known in general and will therefore not be discussed in more detail herein.

<FIG> shows an example of magnetic flux <NUM> through a hole in an electrically conductive surface where an ordinary planar single coil antenna is used. It is seen that the polarity of the flux changes close to the hole boundary. This magnetic flux <NUM> is different from the magnetic flux <NUM> shown in <FIG> resulting from use of a wireless identification tag such as the tag <NUM> shown in <FIG> and <FIG>.

<FIG> shows a layout <NUM> of inductive planar loops arranged matched to the regions of magnetic flux with positive and negative polarity. Thus, terminals 810a and 810b generate a positive voltage VAB = VB - VA, where VA is the potential at terminal 810a and VB is the potential at terminal 810b, due to the upwards magnetic flux time derivative in region 730a. In the same way; terminals 830a and 830b generate a positive voltage between them due to the upwards magnetic flux time derivative in region 730b, and terminals 860a and 860b generate a positive voltage between them due to the upwards magnetic flux time derivative in region 730c. At the same time terminals 820a and 820b, terminals 850a and 850b, and terminals 850a and 850b generate a positive voltage due to the downwards magnetic flux time derivative in region 730b. The different terminal pairs can be connected in series to increase overall voltage, or in parallel to reduce source resistance.

The inductive planar loops exemplified in <FIG> are all single turn. <FIG> illustrates an example <NUM> where one inductive planar loop is a multi-turn coil terminated by terminals 910a and 910b. A multi-turn coil may be realized as a flat spiral coil, a planar square spiral coil, a planar rectangular spiral coil, a planar hexagonal spiral coil, or an octagonal spiral coil, just to give a few examples. Notably, 'planar' does not necessarily mean that the entire coil is comprised in a plane. Rather, parts of the coil may, e.g., be arranged on different layers of a printed circuit board or the like. Thus, 'planar' should be interpreted broadly to mean any type of structure extending substantially in a plane, i.e., substantially flat, as opposed to having significant extension directions in more than two dimensions, i.e., having a volume in three dimensions.

The above described mechanisms can be exploited in order to provide an improved wireless identification tag system, as will now be described with reference to <FIG>.

<FIG> shows an example wireless identification tag <NUM> for embedding into an electrically conductive surface <NUM> of a rotatable work tool <NUM> such as the work tool shown in <FIG>.

The tag comprising at least a first <NUM> and a second <NUM> inductive planar loop having respective first and second terminals <NUM>, <NUM>, <NUM>. The inductive planar loops in the example of <FIG> are connected in series and therefore share a common terminal <NUM>. Thus, according to aspects, a terminal like the terminal <NUM> may just be a continuing wire that extends from a planar loop into another planar loop without interruption. The first loop <NUM> is directed in a clockwise direction <NUM>. The second loop <NUM> is instead directed in a counterclockwise direction <NUM>, i.e., in an opposite direction compared to the first loop. Thus, by connecting the loops by the common terminal <NUM>, the two loops become connected in series with respect to an induced voltage at the terminals of the loops.

The first inductive planar loop <NUM> and the second inductive planar loop <NUM> are arranged in relation to a common plane, e.g., parallel to the common plane. Notably, connecting to the discussion above on regions with different magnetic flux polarity, the first inductive planar loop <NUM> and the second inductive planar loop <NUM> are arranged to cover different areas of the common plane, where each area on the common plane is associated with a respective polarity of the magnetic flux normal to said plane. The plane referred to is here a plane defining a major extension of the flat wireless identification tag, which is coined shaped in this example. According to an example, a diameter D of the wireless identification tag <NUM> is between <NUM>-<NUM>, and preferably about <NUM>.

The different areas may, according to some aspects, be separate areas. However, the areas may also be partly overlapping, which can be the case, e.g., if the inductive planar loops are formed on separate layers of a PCB.

<FIG> shows the wireless identification tag <NUM> when embedded in a hole <NUM> formed in an electrically conductive surface <NUM> of a rotatable work tool <NUM>. The tag is preferably comprised on a piece of printed circuit board (PCB), which can be glued into a hole formed in the work tool <NUM>.

With reference to <FIG>, the wireless identification tag <NUM> comprises protruding portions <NUM> configured to engage slots formed in the work tool, thereby aligning the tag <NUM> with respect to the work tool <NUM>. The wireless identification tag shown in <FIG> is arranged to be embedded into the work tool <NUM> such that the separation line <NUM> forms a tangent to the circular arc <NUM>. The protruding portions simplify assembly of the work tool <NUM> and the tag <NUM>.

According to other aspects, the protruding portions <NUM> are configured as distance elements to space the tag <NUM> from the edge of the hole <NUM> formed in the work tool <NUM> to receive the tag <NUM>. The distance elements then center the tag in the hole and allows for, e.g., glue to fill the gap between tag and hole boundary.

The tag <NUM> is symmetric in the sense that a symmetry line or separation line <NUM> separates the first <NUM> and the second <NUM> inductive planar loops. This way, the first inductive planar loop <NUM> will be radially outside the circular arc <NUM> when the tag rotates along with the work tool <NUM> in direction D, while the second inductive planar loop <NUM> will be located radially inside the circular arc <NUM>. Notably, when the tag <NUM> passes under the reader <NUM>, a center point <NUM> of the tag follows along the circular arc <NUM> each revolution. In other words, the areas are separable by a line <NUM> drawn on the common plane or by an arc of a circle having a radius R drawn on the common plane.

With reference to the discussion in connection to <FIG>, the tag <NUM> may according to some aspects comprise three or more inductive planar loops, not only two as shown in <FIG>. Each inductive planar loop is then arranged to cover a different or separate area of the common plane, where each area is associated with a respective polarity, i.e., positive or negative, of the magnetic flux normal to said plane. It is appreciated that there are only two possible polarisations of the flux normal to a plane, namely positive and negative.

The tag <NUM> shown in <FIG> has single turn inductive planar loops. According to some aspects, at least one of the first inductive planar loop <NUM> and the second inductive planar loop <NUM> is a single turn inductive planar loop. However, one or more of the loops may also be a multiple turn inductive planar loop. An example of a wireless identification tag <NUM> with multiple turn indictive planar loops is shown in <FIG>. The first loop <NUM> and the second <NUM> planar loops are multiple turn inductive planar loops arranged serially connected and in a common plane.

The two loops comprising multiple turns provide a coupling with increased induced voltage at the terminals of the tag with respect to the reader <NUM>. In <FIG>, the inductive planar loops are constructed by a sequence of half-moon shaped turns starting from a terminal <NUM>, <NUM>. The two loops are serially connected, although the connecting or common terminal corresponding to the terminal <NUM> in <FIG> is not shown in <FIG>. The first loop <NUM> is directed in a counterclockwise direction. The second loop <NUM> is instead directed in a clockwise direction, i.e., in an opposite direction compared to the first loop.

As noted above, the wireless identification tags shown in <FIG> and <FIG> are both arranged to be embedded into the work tool <NUM> such that the separation line <NUM> form a tangent to the circular arc <NUM>.

<FIG> shows a wireless identification tag reader <NUM> for reading data from the wireless identification tag <NUM>, also when the tag is embedded into an electrically conductive surface <NUM> of a rotatable work tool <NUM>, the reader comprises at least a first <NUM> and a second <NUM> inductive planar loop inducing a current distribution in the surface of the rotatable work tool <NUM> which together with the current distribution in loop <NUM> and loop <NUM> is associated with a magnetic flux through the hole <NUM> shown, e.g., in <FIG>, matched to respective first <NUM> and second <NUM> inductive planar loops on the tag <NUM>. Each loop <NUM>, <NUM> on the reader <NUM> has a corresponding first and second terminal <NUM>, <NUM>, <NUM>, wherein the first loop <NUM> is arranged to generate a magnetic flux having a first flux polarity, wherein the second loop <NUM> is arranged to generate a magnetic flux having a second flux polarity different or opposite from the first flux polarity.

According to aspects, the first <NUM> and the second <NUM> inductive planar loop have arcuate forms corresponding to circle arcs of circles with a first and a second radius associated with the rotatable work tool <NUM>. The length L of the arcs may be configured in dependence of the rotational speed of the work tool <NUM>, and the time required to perform wake up and communication operations as the tag <NUM> passes the reader <NUM>. According to an example, the length L is between <NUM>-<NUM>, and preferably about <NUM>.

There is also disclosed herein a wireless identification tag reader <NUM> for reading data from a wireless identification tag <NUM> embedded into an electrically conductive surface <NUM> of a rotatable work tool <NUM>. The reader comprises at least one loop, of which one loop segment is positioned over a line <NUM> defining separation of areas with flux of opposite polarities matching the separation line <NUM> between areas of opposite flux polarities of the wireless identification tag loops.

With reference to <FIG>, there is furthermore disclosed herein a blade guard <NUM> for a work tool <NUM> comprising a rotatable work tool <NUM>, wherein the blade guard <NUM> comprises a wireless identification tag reader according to the above discussion.

The tag <NUM> and the reader <NUM> together form a wireless identification tag system <NUM>, <NUM> comprising a wireless identification tag <NUM> and a wireless identification tag reader <NUM> for reading data from the wireless identification tag <NUM> when embedded into an electrically conductive surface <NUM> of a rotatable work tool <NUM>, the reader <NUM> comprising at least one inductive planar loop <NUM>, <NUM>, of which at least one loop segment is positioned over a line <NUM> defining separation of areas with magnetic flux of opposite polarities matching a separation line <NUM> between areas of opposite flux polarities of inductive planar loops on the wireless identification tag.

Herein, a serial connection of two or more inductive planar loops or coils is a connection which increases overall voltage, i.e., a connection between positive and respective negative voltage terminals. It is appreciated that the relative terms positive voltage and negative voltage are defined in dependence of the direction of magnetic flux' time derivative through the inductive planar loop. Ideally, for a serial connection, the voltage induced over the new (combined) two ports of the combined loops is the sum of the voltage induced over each of the individual loops. However, losses may be incurred resulting in a combined voltage somewhat below the sum of the voltage induced over each of the individual loops. In some implementations of systems such as this, a capacitance is used to make the coil and capacitance circuit resonant which produces an even higher voltage. The capacitance can also in some systems be in series with the inductance of the antenna and then the voltage at resonance will be very low but the current high. Such implementations are known and will therefore not be discussed in more detail herein.

A parallel connection of two inductive planar loops is the opposite to a serial connection. If the serial connection connects positive terminal to negative terminal, the parallel connection connects positive to positive, or negative to negative. It is again appreciated that the relative terms positive voltage and negative voltage are defined in dependence of the direction of magnetic flux' time derivative through the inductive planar loop. Ideally, for a serial connection, the voltage induced over the new (combined) two ports of the combined loops is the same as the voltage induced over each of the individual loops if the voltages of the two loops are identical.

According to some aspects, the wireless identification tag <NUM> comprises a connecting network <NUM> configured to serially connect the first <NUM> and the second <NUM> inductive planar loops, thereby increasing a total voltage induced by the first <NUM> and the second <NUM> inductive planar loop in response to changes in a magnetic flux.

According to some other aspects, the wireless identification tag <NUM> comprises a connecting network <NUM> configured to connect the first <NUM> and the second <NUM> inductive planar loops in parallel, thereby reducing source resistance associated with the wireless identification tag <NUM>. Source resistance is here to be interpreted in relation to the resistive element of a circuit equivalent comprising of the series connection of a Thévenin equivalent and a reactance, that electrically describes the power delivered by the planar inductive loops <NUM> and <NUM> into a load impedance when the loops are subjected to a time varying magnetic flux.

The connecting network <NUM> may, e.g., be just a common terminal such as in <FIG>. However, the terminals of one or more inductive planar loops may also be connected to ports on a switch circuit comprising a connecting matrix. This connecting matrix may be arranged to permanently connect terminals in a pattern, or it can be arranged to connect terminals according to some input control signal. This way the connections between loops may be switched from a serial connection into a parallel connection depending on the control signal.

The wireless identification tag <NUM> may, according to some aspects, comprise an identification circuit <NUM> connected to the first inductive planar loop <NUM> and to the second inductive planar loop <NUM>, wherein the identification circuit <NUM> is arranged to modulate a load on the terminals of the first inductive planar loop <NUM> and on the second inductive planar loop <NUM>, thereby providing an inductive communication channel to a wireless identification tag reader <NUM>. Inductive communication channels were discussed above. Such channels and methods of communication are known in general and will not be discussed in more detail herein. One example identification circuit <NUM> will be discussed below in connection to <FIG>. The identification circuit <NUM> may comprise, e.g., processing circuitry, storage medium <NUM>, and an interface for communications <NUM>. The interface communicates via the inductive planar loops with the reader <NUM> by modulating a load on the terminals of the first inductive planar loop <NUM> and on the second inductive planar loop <NUM>. There are also low frequency RFID protocols which do not use load modulation but instead has a charging time and then actively transmits once the RFID circuit has enough energy to do so.

According to some aspects, the identification circuit <NUM> is arranged to be powered via the first <NUM> and second <NUM> inductive planar loops. Thus, as the wireless identification tag passes in vicinity of the reader, it draws energy from the reader which allows it to power up and start operating. Any surplus energy may be stored by a capacitor, battery, or other means for storing electrical energy.

According to some aspects, the identification circuit <NUM> is arranged to store identification data. The identification data may, e.g., comprise an identification code or number which can be used to identify the type of object which the tag is attached to, or its owner. The identification data may furthermore comprise data to identify a production batch, a producer, a classification or the like.

The identification data may also store dimension data such as a rotatable work tool diameter and thickness.

The identification data may furthermore comprise data relating to intended use, i.e., an operational design regime of the tool and other tool specifications.

The dimension data and data relating to intended use may support applications that prevent erroneous use of the construction equipment.

The identification data may also comprise data relating to an owner of the tool, optionally in combination with authentication data.

The authentication data and data relating to the owner of the tool can be used to prevent unauthorized use of the construction equipment and/or of the rotatable work tool <NUM>.

The identification circuit <NUM> may furthermore be equipped or connected to various forms of sensors or actuators. For instance, a temperature sensor, arranged to determine a temperature value associated with the work tool <NUM>, may be configured to periodically sample a temperature value associated with the work tool <NUM>, and store the data, or some function of the data such as maximum temperature, in the storage medium <NUM>. The reader <NUM> can then be used to access the stored temperature data in order to monitor, e.g., if the work tool <NUM> has been subject to overheating. Temperature data in the form of temperature signatures can also be used to detect when the work tools has been worn out and needs replacement. The identification circuit <NUM> can be configured to perform such detection based on the temperature data and trigger transmission of a warning signal via the reader <NUM>.

According to other aspects, the identification circuit <NUM> can be arranged to determine an acceleration value, e.g., by means of an inertial measurement unit (IMU) integrated with or connected to the identification circuit. The IMU can be configured to determine an engine speed, e.g., a rotational velocity in terms of revolutions per minute (RPM). This data can again be read out via the reader by, e.g., the control unit <NUM>. By comparing the RPM from the IMU with the RPM from the engine control system, need for drive belt adjustment, drive belt wear and the like can be determined. It is also possible to determine the type of material being cut by analysis of the vibrations measured by the IMU. In case the work tool <NUM> is used to cut into a material for which it was not intended, a warning signal can be issued. Other forces and vibrations acting on the tool can also be determined and stored for later access. This way analysis can be performed on a tool to see if the tool has been subject to unusually large forces or vibrations, or mechanical impact.

A kickback condition can be detected by the IMU on the identification circuit <NUM> and the event can be stored in memory. The kickback data can then form basis for further analysis.

A pre-kickback condition can also be detected by the IMU on the identification circuit <NUM>. A pre-kickback condition is a jerking motion by the tool which often occurs prior to kickback. The pre-kickback condition often occurs when the rotatable work tool <NUM> is subject to wear.

Erroneously assembled work tools give rise to vibrations which can be detected. A warning signal may be triggered in case the vibrations match some pre-determined vibration criteria.

According to some other aspects, the identification circuit <NUM> is arranged to receive data from the wireless identification tag reader <NUM>, and to store the data in a memory unit. This enables, e.g., the reader <NUM>, or a control unit <NUM> connected to the reader <NUM>, to measure operating time for a given tool, and to update an operating time parameter of the tool. A user can then read out the operating time parameter and thereby obtain information about how long a given tool has been used. For this purpose, a separate reader device <NUM> may be provided. This separate reader device <NUM> is arranged to interface with the wireless identification tag <NUM>, to power the tag, and to read out data from the tag <NUM>.

The reader <NUM> and/or control unit <NUM> may also determine one or more operating conditions and store this information in the tool, by the identification circuit. The operating conditions may, e.g., comprise a user identity or authorization code, a time of day, a day of the week, and the like. The separate reader device <NUM> can then be used to determine who has used a given tool, when, and for how long.

To summarize, with reference also to <FIG>, the construction equipment <NUM> is arranged to obtain data from the wireless identification tag <NUM> via the reader <NUM>, and to take action in response to the obtained data, wherein the action comprises any of; adjusting one or more operation parameters of the construction equipment, triggering an emergency routine or warning signal, and executing an authentication procedure.

<FIG> is a flow chart illustrating methods as disclosed herein. These methods comprise measuring data S1 by one or more sensor units arranged in connection to the wireless identification tag, on the work tool <NUM>. The data is then optionally pre-processed by the identification circuit <NUM>, before being read out S2 by the reader <NUM> as the tag passes in vicinity of the reader <NUM>. The methods also comprise processing the data by the control unit <NUM>. Some examples of the illustrated methods have been discussed above.

The methods may also comprise reading data from the tag <NUM> by the separate reader device <NUM> discussed above.

With reference again to <FIG>, which shows construction equipment <NUM> comprising a work tool <NUM>. The work tool <NUM> in turn comprises an embedded wireless identification tag <NUM> according to the discussions above. The wireless identification tag <NUM> is configured to rotate about a center of rotation C during operation of the work tool.

Some types of construction equipment are very sensitive to imbalance in the work tool. A cut-off disc for instance may start to wobble and cause reduced comfort for the user in case the rotatable work tool is not correctly balanced. The hole formed in the work tool for embedding the wireless identification tag <NUM> will cause a slight shift in the balance of the tool, since the tag is likely of less weight than the material which has been removed. To compensate for this shift of mass, the work tool <NUM> may optionally comprise a balancing hole configured to compensate for a weight imbalance in the rotatable work tool <NUM> due to the embedded wireless identification tag <NUM>. The balancing hole or holes may be arranged on opposite side of the work tool compared to the wireless identification tag, i.e., on the other side of the tool with respect to the center of rotation C. One or more balancing holes may be formed in the work tool <NUM>. Alternatively, or in combination with the balancing holes, extra weights may be arranged on the work tool to balance the tool in compensation of the wireless identification tag <NUM>.

According to some aspects, the work tool <NUM> comprises one or more embedded permanent magnets <NUM> configured in radial dependence of the embedded wireless identification tag <NUM>. A magnet <NUM> may, for instance, be arranged in a balancing hole. These magnets may be used to wake up the reader, i.e., they may be arranged in front of the wireless identification tag in the rotation direction D. When they pass the reader, the reader knows the tag <NUM> soon follows, and it can therefore power up its systems. The reader can then go to sleep after the tag has passed, until the magnet passes again. This way the reader may conserve energy, by implementing a type of duty-cycle operation.

According to some aspects, with reference to <FIG>, <FIG> and <FIG>, the wireless identification tag reader <NUM> comprises an energy storage device <NUM> and a charging circuit <NUM> arranged to harvest energy from one or more permanent magnets <NUM>, <NUM> attached to the rotatable work tool <NUM>. The wireless identification tag reader <NUM> may then be at least partly powered by the energy storage device <NUM>.

This way the reader can be energy self-supportive in that it harvests energy from the time varying magnetic flux of the permanent magnet <NUM> which rotates to pass the reader periodically.

According to some related aspects, the wireless identification tag reader <NUM> comprises a radio frequency transceiver <NUM> configured to transmit the data from the wireless identification tag <NUM> to an external entity such as the control unit <NUM> and/or the remote server <NUM>. This way the need for a wired connection to, e.g., the control unit <NUM> is avoided, which is an advantage. An example of this type of tag will be discussed below in connection to <FIG>.

It is appreciated that the permanent magnet <NUM> may have at least two different purposes, i.e., energy harvesting and circuit wake-up. One or more permanent magnets may be arranged on the rotatable work tool <NUM>. For energy harvesting purposes, it may be advantageous to embed an array of permanent magnets with alternating polarity in order to provide an increased time varying magnetic flux experienced by the reader <NUM>. Thus, there is disclosed herein a rotatable work tool <NUM> comprising one or more embedded permanent magnets <NUM> configured to power and/or wake up a wireless identification tag reader <NUM>. An array of permanent magnets is preferably arranged along a circular arc with alternating polarity in order to optimize energy harvesting capability.

With reference to <FIG>, according to some aspects, the work tool <NUM> also comprises a wire <NUM> extending in a loop radially outwards on the rotatable work tool <NUM> from the embedded wireless identification tag <NUM>. The embedded wireless identification tag <NUM> is arranged to detect tool wear in case the wire loop is broken. Thus, if an abrasive portion or cutting segment <NUM> of the work tool <NUM> is worn down, the wire gets cut, which the tag <NUM> can detect, e.g., by detecting the resulting open circuit. The tag <NUM> can then trigger a warning signal which the control unit <NUM> can receive via the reader <NUM>.

Several applications may be realized by the herein disclosed identification tags, readers, and systems. These applications will now be discussed in detail. It is appreciated that the applications may be implemented separately or in combination. The applications are based on construction equipment <NUM> comprising a rotatable work tool <NUM>, a wireless identification tag reader <NUM>, and a control unit <NUM>. The applications are also possible to realize based on the wireless identification tag <NUM> and construction equipment discussed below in connection to <FIG> and <FIG>. The rotatable work tool <NUM> comprises a wireless identification tag <NUM>, <NUM> according to the above discussion, i.e., the tag is configured to store data configured to be accessible via the wireless identification tag reader <NUM> or via radio link to the control unit <NUM> as discussed below in connection to <FIG> and <FIG>.

In some applications, as noted above, the data configured to be accessible via the reader <NUM> or by radio frequency link <NUM> comprises identification data to identify the rotatable work tool <NUM>. This allows for keeping track of the rotatable work tool <NUM> by, e.g., defining a digital twin associated with the rotatable work tool. For instance, the digital twin may comprise data related to tool specification, intended use domain, dimensions, and the like. The digital twin may also comprise information associated with an owner of the tool.

In some other applications, the data configured to be accessible via the reader <NUM> or by radio frequency link <NUM> comprises authentication data to authenticate the rotatable work tool <NUM> against the control unit <NUM>. The authentication data can be used to, e.g., ensure that only the intended tool is possible to use with a given piece of construction equipment. In case some other tool is attached to the equipment, the equipment can be prevented from operating by, e.g., disabling the power source or the like. A rental company, fleet operator, or the like, can thereby assure that a machine is only operated with certain rotatable work tools <NUM>.

The data configured to be accessible via the reader <NUM> or by radio frequency link <NUM> optionally also comprises tool specification data associated with the rotatable work tool <NUM>. This way a given machine can be pre-configured to only accept tools complying with some range of specifications. For instance, a machine may only be possible to start if the specification of the rotatable work tool meets some pre-determined criteria. If the rotatable work tool does not meet the criteria, operation can be prevented and/or a warning signal can be triggered.

The data configured to be accessible via the reader <NUM> or by radio frequency link <NUM> may also comprise tool dimension data associated with the rotatable work tool <NUM>. A machine can be configured to only accept tools having certain pre-defined dimensions. If a tool not complying the requirements on dimension is attached to a given piece of construction equipment, operation can be prevented, or a warning signal can be triggered. This also applies to the interface between tool and machine. If the two are not in compliance, operation can be prevented and/or a warning signal triggered.

The wireless identification tag <NUM>, <NUM> optionally comprises a temperature sensor arranged to determine and to store a temperature value associated with the rotatable work tool <NUM>. This allows the construction equipment to monitor tool temperature and thereby, e.g., prevent tool overheating. If the reported temperature from the wireless identification tag goes above a predetermined threshold level, then the machine can be stopped, a warning signal can be triggered, or the rotational velocity decreased. Cooling water flow can also be controlled in dependence of the reported tool temperature, i.e., the construction equipment <NUM> is optionally arranged to regulate a flow of water for cooling the rotatable work tool <NUM> based on a temperature sensor reading from the wireless identification tag <NUM>.

The wireless identification tag <NUM>, <NUM> may further comprise a first and a second temperature sensor, arranged radially from each other on the rotatable work tool <NUM>, wherein the first and second temperature sensor is arranged to determine a radial temperature gradient associated with the rotatable work tool <NUM>. This way a more refined control based on tool temperature is enabled. By knowing the temperature gradient and the radial location R of the tag, a temperature on the perimeter of the tool, close to abrasive or cutting elements, can be determined by extrapolating the temperature gradient from the location of the tag.

As noted above, the reader <NUM> and/or control unit <NUM> may store data in the tag comprising information related to who has used the tool, when, and for how long. This data can then be used for setting service intervals and determining when a rotatable work tool <NUM> should be replaced. It may be advantageous to let the reader <NUM> and/or the control unit <NUM> measure operating time, since the wireless identification tag <NUM> may be sleeping for large portions of the operating time, and can therefore not easily measure time by, e.g., a timer or a clock.

Nevertheless, the wireless identification tag <NUM>, <NUM> optionally comprises a timer or clock configured to determine and to store an operating time associated with the rotatable work tool <NUM>. This allows the control unit and/or the remote server <NUM> to monitor how long a tool is used. This data can then be used for setting service intervals and determining when a rotatable work tool <NUM> should be replaced.

The wireless identification tag <NUM>, <NUM> optionally comprises an inertial measurement unit (IMU). IMUs were discussed above. The IMU may be configured to monitor a vibration signature of the rotatable work tool <NUM>, and to detect any of; crack formation in the tool, blade core skew or unevenness, blade wear, and tool glazing or occurrence of polished diamonds, based on the vibration signature.

A vibration signature is a time sequence of vibration which can be used to identify various conditions. For instance, crack formation in the rotatable work tool gives rise to a characteristic vibration pattern which can be detected by the IMU by comparing the measured vibration to a set of pre-defined vibration patterns in terms of, e.g., waveform shape of frequency characteristics. Blade core skew or unevenness, blade wear, and tool glazing or occurrence of polished diamonds also give rise to characteristic vibration patterns or signatures which can be detected by the IMU. The detection may be based on an artificial neural network trained to recognize various types of vibration signatures.

Other applications comprise the IMU being configured to monitor rotatable work tool <NUM> jerk, and to detect a kickback condition and/or a pre kickback condition based on the monitored tool jerk. Kickback conditions are associated with rapid acceleration in certain directions. Kickback is often preceded by one or more pre-kickback events, which are minor kickbacks or jerking motions by the tool. An IMU can be trained by, e.g., artificial neural network or otherwise configured to recognize such pre-kickback events and to trigger a warning signal or even prevent further use of the tool until it has been serviced, e.g., by replacement or re-tipping of the rotatable work tool <NUM>.

Some more advanced applications are built on a construction equipment system <NUM>, <NUM> comprising the construction equipment <NUM> discussed herein and the remote server <NUM>. The remote server <NUM> is communicatively coupled <NUM> with the control unit <NUM> and configured to access data stored by the wireless identification tag <NUM>, <NUM>.

In some such applications the remote server <NUM> and/or the control unit <NUM> is arranged to determine a cost per use associated with the construction equipment <NUM>. The cost per use can be determined based on, e.g., estimated tool wear, tool use time, and on how the tool has been used, e.g., if challenging materials have been processed by the tool or if the tool has been used under lighter load only.

In some other applications the remote server <NUM> is arranged to store information relating to the construction equipment <NUM> and/or relating to the rotatable work tool <NUM>, wherein the information is indexable by identification data stored by the wireless identification tag <NUM>. This allows, e.g., a fleet operator to keep track of inventory by managing a set of digital twins corresponding to the work tools. The digital twins can be used to keep track of tool use, tool wear, and to determine appropriate service intervals.

The remote server <NUM> can also be arranged to determine a service interval associated with the construction equipment <NUM> and/or trigger rotatable work tool <NUM> replacement based on the data stored by the wireless identification tag <NUM>, <NUM>.

Some applications comprise the remote server <NUM> being arranged to determine one or more statistics associated with the construction equipment <NUM> and/or with the rotatable work tool <NUM>. These statistics can be used by a fleet operator or by a tool manufacturer for analysis and optimization of overall operations. The statistics can also be used as feedback for design of new tools and updates to existing products.

Some of the data reported from the wireless identification tag may be indicative of tool misuse by an operator. For instance, some operator or group of operators may experience increased occurrences of kickback conditions, or increased tool wear. This misuse can be detected, and training needs identified. Training can then be offered to identified operators or groups of operators. In other words, the remote server <NUM> is optionally arranged to determine a training need of an operator using the construction equipment based on the data stored by the wireless identification tag <NUM>, <NUM>.

<FIG> schematically illustrates, in terms of a number of functional units, the general components of a control unit <NUM>, or an identification circuit <NUM>, a tag <NUM> or a reader <NUM> according to embodiments of the discussions herein. Processing circuitry <NUM> is provided using any combination of one or more of a suitable central processing unit CPU, multiprocessor, microcontroller, digital signal processor DSP, etc., capable of executing software instructions stored in a computer program product, e.g. in the form of a storage medium <NUM>. The processing circuitry <NUM> may further be provided as at least one application specific integrated circuit ASIC, or field programmable gate array FPGA.

Particularly, the processing circuitry <NUM> is configured to cause the device <NUM>, <NUM>, <NUM>, <NUM> to perform a set of operations, or steps, such as the methods discussed in connection to <FIG> and the discussions above. For example, the storage medium <NUM> may store the set of operations, and the processing circuitry <NUM> may be configured to retrieve the set of operations from the storage medium <NUM> to cause the device to perform the set of operations.

The device <NUM>, <NUM>, <NUM>, <NUM> may further comprise an interface <NUM> for communications with at least one external device.

The processing circuitry <NUM> controls the general operation of the device <NUM>, <NUM>, <NUM>, <NUM>, e.g., by sending data and control signals to the interface <NUM> and the storage medium <NUM>, by receiving data and reports from the interface <NUM>, and by retrieving data and instructions from the storage medium <NUM>. In case of a tag or a reader, the interface comprises (or is connected via ports) to the inductive planar loops of either the tag <NUM> or the reader <NUM>.

<FIG> illustrates a computer readable medium <NUM> carrying a computer program comprising program code means <NUM> for performing the methods illustrated in <FIG>, when said program product is run on a computer. The computer readable medium and the code means may together form a computer program product <NUM>.

<FIG> shows construction equipment <NUM> where a wireless identification tag <NUM> has been embedded into the rotatable work too <NUM>. However, this wireless identification tag comprises an inductive loop configured to harvest energy from a time varying magnetic flux generated by one or more permanent magnets <NUM> arranged on the blade guard <NUM> of the construction equipment <NUM>. The wireless identification tag <NUM> further comprises energy storage means and a radio frequency transceiver, by which it can communicate via wireless link <NUM> with the control unit <NUM>. Thus, the applications discussed above are possible to realize without a reader arranged in connection to the blade guard <NUM>, such as the reader <NUM> shown in <FIG>. The identification circuit <NUM> discussed above can be used together with the wireless identification tag <NUM> without modification, or with minor modifications.

According to an example, a diameter D of the wireless identification tag <NUM> is between <NUM>-<NUM>, and preferably about <NUM>.

<FIG> shows a blade guard <NUM> comprising one or more permanent magnets <NUM> arranged to power a wireless identification tag <NUM> arranged embedded in a rotatable work tool <NUM>. It is appreciated that, although <FIG> shows three magnets, any number of permanent magnets can be used, including a single permanent magnet.

<FIG> also shows a construction equipment <NUM> comprising a wireless identification tag <NUM>, a blade guard <NUM> with one or more permanent magnets <NUM>, and a control unit <NUM> arranged to communicate with the wireless identification tag <NUM> via radio link <NUM>.

<FIG> schematically illustrates a wireless identification tag <NUM> for embedding into a rotatable work tool <NUM>. The tag comprises at least a first inductive loop <NUM>, an energy storage device <NUM>, processing circuitry <NUM>, and a radio frequency transceiver <NUM>. The wireless identification tag <NUM> is arranged to harvest electrical energy from a time varying magnetic flux by the first inductive planar loop <NUM> and to store the electrical energy in the energy storage device <NUM>. The processing circuitry <NUM> and the radio frequency transceiver <NUM> are arranged to be powered by the energy storage device <NUM>.

The control unit <NUM> is communicatively coupled <NUM> to the remote server <NUM> as discussed above.

Claim 1:
A wireless identification tag (<NUM>) for embedding into an electrically conductive surface (<NUM>) of a rotatable work tool (<NUM>), the tag comprising at least a first (<NUM>) and a second (<NUM>) inductive planar loop having corresponding first and second terminals (<NUM>, <NUM>, <NUM>), wherein the first inductive planar loop (<NUM>) and the second inductive planar loop (<NUM>) are arranged in relation to a common plane and wherein the first inductive planar loop (<NUM>) and the second inductive planar loop (<NUM>) are arranged to cover different areas of the common plane, characterized in that each area on the common plane is associated with a respective polarity of the magnetic flux normal to said plane and where first loop (<NUM>) is directed in an opposite direction compared to the second loop (<NUM>).