SE543930C2 - A configurable and self-powered shock sensor, a shot counter and an actuator - Google Patents

Abstract

A shock sensor arrangement (100) comprising a bobbin arrangement with an electromagnetic coil (4) and a magnetic core (2), a magnet (1) associated with a mass inertia, resiliently held in an equilibrium position (P) with respect to the bobbin arrangement (4,2), whereby the magnet (1) is arranged to reciprocate in relation to the bobbin arrangement (4,2) in response to mechanical impact, and a sensor circuit (5) configured to detect an electrical current or voltage generated in the electromagnetic coil (4) by the reciprocating magnet (1), thereby registering the mechanical impact.

Description

TITLE A CONFIGURABLE AND SELF-POWERED SHOCK SENSOR, A SHOTCOUNTER AND AN ACTUATOR TECHNICAL FIELD The present disclosure relates to shock sensors for detecting and registeringmechanical impact and vibration. There are also disclosed systems andmethods for detecting, analyzing and classifying mechanical shock andmechanical vibrations. There is furthermore disclosed herein mechanicalactuators.

BACKGROUND Sensitive equipment such as high precision instrumentation and measurementequipment is often vulnerable to mechanical shock and strong vibration.Unless carefully handled, the equipment may suffer reduced performance ormay even break down due to hard mechanical impacts or strong vibration.

Other devices may be prone to material fatigue causing fau|ts and ma|functionif the device is subjected to extended periods of vibration, even if the vibrationis not particularly strong. lt is desired to detect if a given piece of equipment has been subject tomechanical shock or vibrations. lf exposure to mechanical shock is detected,then the equipment can be examined in order to determine if its function hasbeen impacted, and if so the equipment can be repaired or replaced to ensurecontinued system function. lt may also be of importance to determine when intime and perhaps also how often a given piece of equipment has been subject to shock or vibration.

Known shock sensors comprise mechanical solutions which may be associated with limited precision, and which are often complicated and costly.

Also, some known shock sensors are only able to detect one shock event, afterwhich the sensor needs to be replaced or manually reset.

US 3,940,999 discloses an example mechanical shock sensor based on abody of liquid.

There is a need for improved shock sensors.

SUMMARY lt is an object of the present disclosure to provide improved shock sensorswhich are both durable and which provide a high level of detectionperformance. The disclosed shock sensors may also be self-powered,avoiding the need for an external power supply or regular battery exchange.

The object is obtained by a shock sensor arrangement comprising a bobbinarrangement with an electromagnetic coil and a magnetic core. The shocksensor arrangement also comprises a magnet associated with a mass inertia,resiliently held in an equilibrium position P with respect to the bobbinarrangement, whereby the magnet is arranged to reciprocate in relation to thebobbin arrangement in response to mechanical impact, wherein the magnet isheld in the equilibrium position P by a magnetic force generated between themagnet and the magnetic core so that a magnetic flow of the magnet is closedin a magnetic circuit comprising the magnetic core, and a sensor circuitconfigured to detect an electrical current or voltage generated in theelectromagnetic coil by the reciprocating magnet, thereby registering the mechanical impact.

Thus, an efficient and durable shock sensor is provided which requires aminimum of maintenance. The shock sensor is sensitive in the sense that it isable to detect very faint vibration. The shock sensor is also mechanically robustin the sense that it can be made to withstand severe mechanical impact andstrong vibrations for extended periods of time. Notably, the magnet does not need to be mechanically held in the equilibrium position by resilient members such as springs, since the magnet strives towards the bobbin arrangementwith the magnetic core due to magnetic force alone.

According to some aspects, the shock sensor arrangement comprises anenergy storage device configured to store electrical energy generated by thebobbin arrangement, wherein the energy storage device is arranged to at leastpartly power the sensor circuit. The shock sensor is thereby self-powered,which means that there is no need for an external power source, normaintenance involving battery replacements and the like, thereby extending the maintenance free running time of the device.

According to other aspects, the sensor circuit is arranged to record and to storedetected electrical current and/or electrical voltage values. This way the shocksensor keeps a record of events, which can be read out and analyzed,providing information about the history of the shock sensor environment whereit has been mounted. Consequently, the device can be attached to, e.g., apiece of sensitive equipment in order to see if the equipment has been subjectto shock requiring diagnostic maintenance or the like. The sensor can also besurface mounted or otherwise integrated with the electronics on the device tobe monitored, such as a printed circuit board (PCB), thereby providing an integrated shock sensor functionality.

According to an example, the sensor circuit may be arranged to determine ashock severity value based on a detected electrical current magnitude and/orbased on an electrical voltage magnitude. This way it can be established if,e.g., a piece of equipment has been subject to severe mechanical impact requiring diagnostic maintenance to ensure equipment functionality.

According to further aspects, the sensor circuit can be configured with one ormore detection criteria and arranged to compare the detected electrical currentor voltage to the detection criteria. For instance, the detection criteria can be athreshold, allowing for low complexity processing. The detection criteria canalso be more advanced, e.g., involving pattern recognition, signal amplitudeand/or frequency characteristics, and impact duration, just to name a few.

The magnet may for example be arranged to be resiliently held inside a tubularstructure configured to guide the magnet along the axis. The tubular structureprovides a low friction guiding means which converts mechanical impact froma wide variety of directions into |inear motion along the axis. The tubularstructure also provides structural integrity to the shock sensor, making it morerobust. The magnet may be resiliently held inside the tubular structure bymagnetic force alone, or by a combination of magnetic force and, e.g., springloading or the like. The tubular structure preferably has a circular cross-section shape, but rectangular or hexagonal cross-sectional shapes are also possible.

The shock sensor may also comprise a communication circuit configured tocommunicate over an interface with an external device or a remote server. Thecommunication circuit makes it more convenient and efficient to access data collected by the sensor, which is an advantage.

There is also disclosed herein methods and arrangements for classifyingvibrations into a set of pre-defined types of vibration events. ln particular, thereis disclosed herein a shot counter for a weapon with recoil. The shot counteris arranged to detect when the weapon is fired, and to store the number of firedshots in the storage medium. This way it becomes possible to monitor a givenweapon and to conduct more accurate weapon servicing based on actual use rather than on fixed service time intervals.

According to aspects, the shot counter is configured to record a vibrationsignature and to compare the recorded vibration signature to a set of storedvibration signatures associated with respective types of ammunition. Theshock sensor arrangement is configured to maintain shot counters for at leasttwo different ammunition types. This way a firing history of a weapon can bemonitored in order to properly service the weapon, and to determine when parts of the weapon are due for replacement.

There are also disclosed herein actuators comprising a bobbin arrangementwith an electromagnetic coil and a magnetic core. The actuators comprise amagnet associated with a mass inertia, resiliently held in an equilibriumposition with respect to the bobbin arrangement, whereby the magnet is arranged to reciprocate in relation to the bobbin arrangement in response to acurrent or voltage in the bobbin arrangement, wherein the magnet is held inthe equilibrium position by a magnetic force generated between the magnetand the magnetic core so that a magnetic flow of the magnet is closed in amagnetic circuit comprising the magnetic core. A sensor circuit is configuredto generate the current or voltage in the bobbin arrangement in response to atrigger signal, thereby causing a mechanical motion by the magnet.

There are furthermore disclosed herein methods, circuits, control units,computer programs and measurement devices associated with the same advantages as discussed above.

Generally, all terms used in the claims are to be interpreted according to theirordinary meaning in the technical field, unless explicitly defined otherwiseherein. All references to "a/an/the element, apparatus, component, means,step, etc." are to be interpreted openly as referring to at least one instance ofthe element, apparatus, component, means, step, etc., unless explicitly statedotherwise. The steps of any method disclosed herein do not have to beperformed in the exact order disclosed, unless explicitly stated. Furtherfeatures of, and advantages with, the present invention will become apparentwhen studying the appended claims and the following description. The skilledperson realizes that different features of the present invention may becombined to create embodiments other than those described in the following,without departing from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present disclosure will now be described in more detail with reference tothe appended drawings, where Figures 1-2 schematically illustrate example shock sensor arrangements;Figures 3-8 show details of example shock sensor arrangements; Figure 9 is a flow chart illustrating details of example methods; Figure 10 schematically illustrates a control unit; Figure 11 illustrates a computer program product; Figure 12 schematically illustrates vibration signatures; Figure 13 is a flow chart illustrating details of example methods;Figure 14 schematically illustrates a classification machine; andFigure 15 schematically illustrates a surface mounted component.DETAILED DESCRIPTION Aspects of the present disclosure will now be described more fully withreference to the accompanying drawings. The different devices and methodsdisclosed herein can, however, be realized in many different forms and shouldnot be construed as being limited to the aspects set forth herein. Like numbersin the drawings refer to like elements throughout.

The terminology used herein is for describing aspects of the disclosure onlyand is not intended to limit the invention. As used herein, the singular forms"a", "an" and "the" are intended to include the plural forms as well, unless thecontext clearly indicates otherwise.

There are disclosed herein various types of shock sensors, some of whichhave logging functionality. The disclosed sensors have the ability to sensemechanical shock, i.e. mechanical impact, and also shaking and vibrations.Some of the disclosed shock sensor arrangements are self-powered shocksensors (SPSS) which harvest energy from mechanical forces acting on thesensor. For instance, an SPSS may capture the energy in the mechanicalimpact which the sensor is configured to detect, thereby providing extended operating periods without maintenance or external power sources.

Some of the sensors disclosed herein are configured as surface mountablecomponents which can be assembled onto, e.g., a PCB or the like, therebyproviding an integrated shock sensor functionality to a device or system. Thesurface mountable shock sensor components may be configured as stand- alone components which do not require power or control circuitry.

A mechanical or physical shock is a sudden acceleration caused, for example,by impact. Shock is a transient physical excitation. Mechanical shock may bedescribed in vector form with units of acceleration (rate of change of velocity),or simply in magnitude. A shock pulse can be characterized by its peakacceleration, the duration, and the shape of the shock pulse (half sine,triangular, trapezoidal, etc.). Shock response spectrum is a method for furtherevaluating a mechanical shock.

A mechanical vibration is a sequence of mechanical shocks, often themechanical shocks involved in a vibration are relatively weak compared to a shock event, but this is not always the case.

The magnitude of an event considered as a shock naturally varies fromapplication to application. For instance, high precision measurementinstrumentation in a laboratory is likely to regard quite low magnitude forcesas shock, while mining equipment and other types of heavy machinery are likely to regard significantly stronger force events as shock.

Figure 1 illustrates an example shock sensor arrangement 100. More detailedviews of the shock sensor arrangement are shown in Figures 3-7; Figures 3-4and 7 show side views of the arrangement, and Figures 5-6 show top views, The shock sensor arrangement comprises a permanent magnet 1 having amass inertia and a magnetic core 2. The north (N) and south (S) poles, seeFigure 6, of the magnet 1 are given the opportunity to be oriented in anequilibrium position P, so that the magnetic flow is closed in a magnetic circuitcomprising the magnetic core 2 with high permeability. The magnet 1 shownin Figure 1 is of spherical shape, however, other shapes are also possible.

The permanent magnet 1 is held in position P in the middle of the soft core gapin the magnetic circuit, guided sideways by an optional guiding tube 3. Otherguiding means are of course possible, such as rods forming a cage having anextension direction along the axis A. ln other words, the magnet 1 is held inthe equilibrium position P by the magnetic force generated between thepermanent magnet 1 and the magnetic circuit comprising the magnetic core 2.The magnet is allowed to reciprocate in relation to the rest of the shock sensor arrangement along an axis A, i.e., up and down in Figure 1. Notably, no springsor other resilient members are required in order to resiliently hold the magnetin the equilibrium position P, which is an advantage. The magnet is, accordingto some aspects, free floating, which means that there is only a minimum offriction between the magnet 1 and other parts as the magnet reciprocatesalong the axis A.

As long as there is no mechanical impact or vibration, the magnet 1 stays inthe equilibrium position P. lf there is an impact to the system, the inertial force(due at least in part to the mass inertia of the magnet 1) will cause the magnet1 to reciprocate; The magnet will first be offset from the equilibrium location P,and then return towards the equilibrium position due to the magnetic forceacting on the permanent magnet 1. The magnet will pass the equilibriumposition P and the process will be repeated to cause reciprocating motion ofthe magnet 1 with respect to the rest of the shock sensor arrangement 100. ln addition to holding the magnet 1 in the equilibrium position by means ofmagnetic force, the magnet 1 may also be held by resilient members, e.g.,springs, elastic bands, or elastic meshes, which also allows the magnet toreciprocate in relation to the rest of the shock sensor arrangement along anaxis A. Bushing or other resilient members may be arranged to protect themagnet as it hits the frame at the extreme points of the reciprocating motion, where the magnet changes direction.

As noted above, the shock sensor arrangement 100 optionally comprises aguiding tube 3, which is a tubular structure arranged to constrain the magnet1 to linear motion along the axis A, thereby guiding the magnet as itreciprocates back and forth along the axis A. The end portions 3A, 3B of thetubular structure 3 may be fitted with resilient pads or compression springswhich cause the magnet 1 to 'bounce' off the end sections of the tubularstructure 3 as it reciprocates. These resilient pads improve efficiency of thearrangement, and also protects the magnet from particularly strong mechanical impacts. lt is appreciated that the tubular structure can be replaced by a guidingstructure having other cross-sectional shapes, and may be constructed from,e.g., rods to form a cage instead of a tubular structure. For instance, arectangular guiding structure can be used instead of the circular cross-sectionguiding tube 3. The shape of the magnet 1 is preferably adapted to fit theguiding structure, i.e., matched to the shape of the guiding structure. A cuboidshaped magnet 1 would for instance fit well inside a rectangular guidingstructure, whereby the magnet 1 is arranged to reciprocate in relation to therest of the shock sensor in response to mechanica| impact. Hexagonal cross section guiding structures also possible.

To summarize, the guiding tube 3 in general has an elongated shape allowingthe magnet 1 to reciprocate inside the guiding structure. The shape of themagnet 1 is matched to the shape of the guiding structure to allowreciprocating motion along axis A.

One or more bobbins 4 or windings, e.g., copper windings, are positioned sothat the magnetic flow 630 flows through the coil of the winding as illustratedin, e.g., Figure 6. The bobbin or bobbins are connected to a sensor device 5(shown best in Figure 4) that is arranged to detect an electrical current or anelectrical voltage in the bobbin or bobbins 4.

The shock sensor arrangement 100 works so that an incoming mechanica|shock rapidly moves all the components of the sensor arrangement 100 exceptfor the magnet 1, which, due to its mass inertia, remains in or close to itsoriginal equilibrium position P. ln this way a relative movement occurs between the magnet 1 and the bobbin arrangement 4, 2.

This relative motion causes a rapid change in the magnetic flow 630 throughthe bobbin as illustrated in Figure 6, where a cross 620 represents 'downward'current into the bobbin and a dot 610 represents 'upwards' current out fromthe bobbin, according to convention. The change creates an induced voltageand an electric current 610, 620 is generated which can be detected by thesensor device 5. The magnet 1 then enters a periodic reciprocating motionpattern, passing the gap in the magnetic core 2 in reciprocating motion, until at least a part of the motion energy has been converted into electrical energyin the bobbins 4.

When the movement due to the mechanical shock has ceased, the magnet 1returns to its equilibrium position P due to the magnetic force from, e.g., themagnetic core 2, as it can optimally close its magnetic flow in the middle of thegap of the magnetic core 2. The process can be repeated again and againwithout limit and without manual intervention, which is an advantage comparedto known shock sensors. Thus, the shock sensor arrangement disclosedherein can be used to monitor a series of shocks and not just a single shockevent. ln other words, the shock sensors disclosed herein are configured torevert back to the equilibrium position P after registering a mechanical impact,whereby the shock sensor arrangement is ready to detect a sequence of mechanical impacts without manual reset, manual arming, or the like. lt is noted that no springs are necessary for holding the magnet in theequilibrium position P. Such springs may be disadvantageous in that they maybrake and cause malfunction in the shock sensor. The design shown in, e.g.,Figure 1 voids the use of springs, e.g., compression springs, for holding themagnet in the equilibrium position P.

A sensor circuit, or micro-logger, is according to some of the examplesdescribed herein programmable so that a predetermined limit level, i.e., athreshold, on the allowed mechanical impact or acceleration is configured,thereby providing a configurable shock sensor where, e.g., a detectionsensitivity can be set according to application. Should the sensor circuit besubjected to an impact or acceleration above the configured limit level, thenan alarm can be triggered and / or an event note can be logged in memory.This way, an operator or user can be made aware of any mechanical impacts,shock, or vibrations which the equipment has been subject to, and also astrength or magnitude level associated with each event. More advanced detection mechanisms will be discussed below in connection to Figures 12-14.

According to an example, each impact event is stored in a memory capsule onthe shock sensor, which at a later time can be read out, e.g., when the equipment is supplied with external power supply and communication to anexternal control unit is established. This way the shock sensor can supportanalysis of the history of a given device or system.

Figure 2 shows an example shock sensor arrangement 200 where the magnetis instead resiliently held in position by a leaf spring 9. The function of the shocksensor arrangement 200 is basically the same as the shock sensorarrangement 100. The magnet 1 can now take on a wider variety of shapes,such as the cylinder shapes and/or an array 230 of several magnets 210, 220with alternating polarity, as shown in Figure 2 (top right insert). Thisarrangement will change the magnetic flux, even more rapidly in the magneticcircuit 2, due to the changing magnetic polarity, resulting in a higher voltageoutput. A top view of the shock sensor arrangement 200 is provided in Figure8.

Both Figure 1 and Figure 2 illustrate examples of shock sensor arrangements100, 200, comprising a bobbin arrangement with an electromagnetic coil 4 anda magnetic core 2. A magnet 1, associated with a mass inertia, is resilientlyheld at least partly by magnetic force in an equilibrium position P with respectto the bobbin arrangement 4,2, whereby the magnet 1 is arranged toreciprocate in relation to the bobbin arrangement in response to mechanicalimpact. A sensor circuit 5 is configured to detect an electrical current or voltagegenerated in the electromagnetic coil 4 by the reciprocating magnet, therebyregistering the mechanical impact. lt is advantageous to use a magnet 1 associated with large weight, i.e., largeinertia, since this increases overall efficiency. According to an example, themagnet 1 comprises elements made in Wolfram. For instance, the magnet 1may be mounted in a holder associated with a high density, such as a holdermade in Wolfram or other relatively heavy material. An example holder 240 isshown in Figure 2. A corresponding holder can also be manufactured or holding the magnet 1 in Figure 1.

The reciprocating motion in Figure 1 is along the axis A, while the reciprocatingmotion in Figure 2 is slightly curved as indicated by the path B in Figure 2.

The magnet 1 may have a spherical shape as shown in Figure 1, or acylindrical shape as shown in Figure 2. lt is appreciated that a wide variety ofdifferent magnet shapes are possible. Also, an array 230 of magnets can beused for increased effect, as shown in Figure 2.

As an alternative to holding the magnet 1 in position by magnetic force alone,the magnet can be resiliently held in position by a spring arrangementconfigured to bias the magnet towards the equilibrium position P, or it can beresiliently held in position by a leaf spring as shown in Figure 2.

As illustrated by the example in Figure 1, the magnet 1 is optionally arrangedto be resiliently held inside a tubular structure 3 configured to guide the magnetalong the axis A of reciprocation. The tubular structure 3 protects the magnet1 and the resilient holding means from excessive forces incurred by strongmechanical impacts. lt also guides the magnets as it reciprocates back andforth along the axis A.

A further advantage associated with using the tubular structure 3 is thatmechanical impacts from a wide range of different directions can be translatedinto linear motion along the axis A (or along the curved path B) by the magnet.This way a large variety of different types of impacts and vibrations can bedetected by the arrangement. Thus, a single shock sensor arrangement canbe used instead of a plurality of sensors arranged in different spatialorientations. As noted above, the tubular structure can be replaced by otherguiding means, such as a circular configuration of rods forming a cage in which the magnet may reciprocate along axis A.

The magnetic core 2 is optional; an air-core coil can also be used in caseswhere a resilient member is used to hold the magnet 1 in position. However, ifa magnetic core is used, a wide variety ofdifferent options exist; iron, annealediron, silicon steel, mu-metal, a permalloy material, a supermalloy material, orcarbonyl iron, just to name a few. The magnetic core, or soft core, significantlyimproves the performance of the shock sensor since it increases the energygenerated by the bobbin arrangement 4, 2.

The magnitude and appearance of the voltage and/or current in the bobbinarrangement is directly proportional to the amplitude of the incomingmechanical shock. Thus, mechanical shock magnitude can be quantifiedbased on the generated electrical current or voltage. The energy in the bobbinarrangement is in many applications sufficient to wake up and start amicroprocessor or control unit arranged in connection to the bobbinarrangement. Both shock sensor arrangements 100, 200 may optionallycomprise an energy storage device 6 configured to store electrical energygenerated by the bobbin arrangement 4, 2. The energy storage device 6 maythen at least partly power the sensor circuit 5. The energy storage device 6 isshown in Figure 7. The energy storage device 6 may comprise, e.g., a battery,a capacitor, a supercapacitor, or the like. lt is appreciated that the magnet will move in response to any mechanical forceacting to move the shock sensor arrangement. Even small mechanical forceswill generate electrical current in the bobbin arrangement. This electricalcurrent may not be large enough to count as mechanical shock, but it can stillbe used in energy harvesting to generate an energy supply. This way the shocksensor is able to charge itself while monitoring the incoming vibrations, even ifno vibration or shock of significant strength occurs.

According to some aspects, the sensor circuit 5 is arranged to record and tostore detected electrical current and/or electrical voltage values in memory.The sensor circuit 5 may optionally record and store time stamp valuesassociated with detected electrical current and/or electrical voltage values.This way an operator of the device can access data not only related to theoccurrence of mechanical shock, but also when the shock happened. lf thedata comprises registered vibration, then the time stamp data may indicate theduration of the vibration event.

Thus, the sensor circuit logs events as they happen possibly also with anassociated time stamp, allowing an operator to access data related to thehistory of the sensor arrangement. This logged data may, e.g., be useful inanalyzing remaining useful lifetime (RUL) of a device or system. The logged data can also be used to characterize a given operating scenario, e.g., in orderto determine if a suitable sensor has been deployed or if some other type ofsensor should replace the deployed sensor. For instance, experiencedmechanical shock and vibration may be smaller than expected, indicating thata differently dimensioned or configured sensor arrangement would be bettersuitable than the sensor currently in place. lt will also support the user withinformation, when it is relevant to perform preventive maintenance, to achievemaximum utilization of their equipment, while minimizing probability of equipment or system malfunction.

Different detection mechanisms can be used in the sensor circuit 5 to detectthe electrical current or voltage generated in the electromagnetic coil 4 by thereciprocating magnet 1. For instance, a comparator can be programmed tocompare the input signal to a reference level corresponding to the specifiedlimit acceleration, to determine if the initial voltage of the bobbin system andits duration is high enough to trigger an alarm and /or log a shock event in thememory capsule. ln other words, the sensor circuit 5 may be arranged to detectmechanical impact by comparing the detected electrical current or voltage toa threshold value.

According to another example, the sensor circuit 5 is configured with one ormore detection criteria and arranged to compare the detected electrical currentor voltage to the detection criteria. This allows for more advanced detectionmechanisms to be implemented. For instance, a given event, say a trainpassing, may be associated with a given pattern or sequence of mechanicalshocks and vibrations different from the passing of a car or a truck. Bymatching the generated electrical current or voltage in the bobbin to theconfigured detection criteria, the sensor circuit may be able to classify eventsaccording to different predetermined classes, thereby allowing for moreadvanced system analysis. Also, typical motion patterns and sequences ofparticular interest, can be detected. For instance, a machine or other piece ofequipment may exhibit a change in vibration patterns prior to malfunction. Thisparticular pattern may be detected and used to trigger a notification to an operator or a service technician.

Figure 12 shows an example where a vibration 1210 has been recorded by theshock sensor arrangement 100, 200. The vibration can be characterized interms of signal amplitude A, over time t, as in Figure 12, or in terms of afrequency domain representation of the vibration which can be obtained byapplying a Fourier transform or wavelet transform to the captured vibrationsignature 1210. This vibration is compared to a set 1220, 1230, 1240 ofsignatures, each indicating a specific type of event or type of vibration. Forinstance, vibration signature 1220 may be associated with a first type of event,vibration signature 1230 may be associated with a second type of event, andvibration signature 1240 may be associated with a third type of event. Different similarity metrics can be determined, e.g., a sum of squares metric; m” = 2ï=1(s1[k] - s2[k])2, where m is a measure of similarity between two waveforms, s1 and s2 are discrete sampled vibration signatures, k is a sampleindex and N is the total number of captured samples for a signature. Theclosest signature from the set of signatures can be selected as the signatureassociated with the smallest sum of squares metric.

Figure 13 is a flow chart illustrating methods. There is shown a method forclassifying a vibration using a device according to the discussions above. Themethod comprises obtaining S1x or measuring a vibration signature using ashock sensor arrangement 100, 200 as described above. The method thencomprises comparing S2x the obtained vibration signature to a set of differenttypes of vibration signatures and classifying S3x the vibration based on asimilarity metric. The set of different types of vibration signatures may, e.g., beobtained from the storage 1030, or from a remote server 13 shown in Figure1.

The comparison can be realized based on an Artificial Neural Network 1400as schematically illustrated in Figure 14. The obtained vibration signature isinput at the input layer. The data is then processed over a number of hiddenlayers, before a classification result is obtained at the output layer. The network1400 is first trained based on data obtained for known events. Artificial neural networks, and their training, is known in general and will therefore not be discussed in more detail herein. ln another embodiment the shock sensor 100, 200 is arranged in a weapon todetect the recoil and to, e.g., count the number of firings. For instance, theshock sensor may be arranged in a weapon where there is a possibility to useseveral different types of ammunitions. The shock sensor can then detect,recognize and count not only firings but also remember the type of ammunitionused when firing the weapon, since each type of ammunition has and uniquevibration signature, that is emitted at each firing in a weapon system. This vibration signature can be matched against the measured vibration signature.

Thus, according to some aspects, the shock sensor 100, 200 with the controlunit 5, is arranged to, when mounted on a weapon system, detect each typeof fired ammunition, using Vibration Signature Recognition (VIR), meaning acomparison of the incoming vibration signature with a correspondingpredefined vibration signature as discussed above, and, if a match occurs,when compared to a predefined reference matrix with a set of possibleammunition types for the weapon system, the fired ammunition type will beidentified and a counter incremented to keep track of the use.

According to some further aspects, the sensor circuit 5 is arranged todetermine a shock severity value based on a detected electrical current magnitude and/or based on an electrical voltage magnitude.

A frame structure 7 can optionally be arranged to enclose the shock sensorarrangement 100. All sub-components are then suspended inside the framestructure 7, which constitutes the mechanical interface to the intended deviceor system to be monitored. According to some aspects, the frame structurecomprises fastening means for attaching the sensor arrangement 100, 200 toan external object, whereby mechanical impact to the external object isarranged to be detected by the sensor circuit 5. According to some examples,a base foundation of the frame structure 7 may be attached to an externalobject with double-sided adhesive tape or the like. The frame structure can also be glued, clamped, snapped, welded, riveted, or bolted onto the externalstructure to be monitored.

The sensor circuit may be mounted on a circuit board 14, such as a printedcircuit board (PCB), or the like. This circuit board may be equipped withcommunication interfaces that enable reading of a memory module storinginformation about shock events. For instance, the shock sensor arrangement100, 200 may comprise a communication circuit 11 configured to communicate over an interface with an external device.

According to some aspects, the communication circuit 11 is a wirelesscommunication circuit comprising an antenna and wireless transceiverconfigured to communicate wirelessly with the external device. The wirelesscommunication may be a near-field communication system or a low-energyBluetooth communication system. The scope of the present disclosure is notlimited to any particular form of wires or wireless communication. The skilledperson realizes that various communication methods can be selected basedon application and circumstances.

Figure 9 illustrates a method for detecting mechanical impact whichsummarizes the discussions above. The method comprises configuring S1 abobbin arrangement with an electromagnetic coil 4 and a magnetic core 2,configuring S2 a magnet 1 associated with a mass inertia, resiliently held in anequilibrium position P with respect to the bobbin arrangement 4,2, whereby themagnet 1 is arranged to reciprocate in relation to the bobbin arrangement 4,2in response to mechanical impact, and detecting S3, by a sensor circuit 5, anelectrical current or voltage generated in the electromagnetic coil 4 by thereciprocating magnet, thereby registering the mechanical impact.

Conversely, the shock sensors disclosed herein can also work as actuators,when a power pulse is input into the bobbin arrangement, so this results in amechanical movement by the magnet. Consequently, there is disclosed hereinan actuator comprising a bobbin arrangement with an electromagnetic coil 4and a magnetic core 2, a magnet 1 associated with a mass inertia, resilientlyheld in an equilibrium position P with respect to the bobbin arrangement 4,2.

The magnet 1 is arranged to move in relation to the bobbin arrangement 4,2in response to a current or voltage in the bobbin arrangement. A sensor circuit5 is configured to generate the current or voltage in the bobbin arrangement inresponse to a trigger signal, thereby causing a mechanical transient by themagnet 1.

Thus, the disclosed actuator is similar to the shock sensors discussed above,but operated in reverse. lnstead of registering mechanical impact, the magnetis caused to move in relation to the frame structure 7. The actuator can, forinstance, be used to generate vibrations for notifying a user of, e.g., a smartphone or the like. The actuator can also be used for other purposes where amechanical transient effect is desired. The generated current or voltage will determine the manner of mechanical movement by the magnet 1.

The devices disclosed herein may be used as combined shock sensors andmechanical actuators. l.e., the devices may be configured to detect shock, andgenerate motion by the magnet in response to some condition. Themechanical motion may be powered from energy harvested from the magnet and bobbin arrangement and stored. lt is appreciated that the shock sensors disclosed herein can be maderelatively small, i.e., a spherical magnet with diameter of about 2-3 mm can beused in a frame that fits inside a cuboid with side on the order of 5-6 mm. lngeneral, the dimensions of the magnet can be such that the magnet fits withina bounding box having a side between 2-10 mm, the overall shock sensor maythen fit within a bounding box having dimensions on the order of 4-20 mm.

With reference to Figure 15, these small shock sensor arrangements 100' canbe configured with pads for surface mounting onto a printed circuit board (PCB)1510. The shock sensor can then be used as a component when designingelectrical systems, just like a microprocessor or other component 1520 that issurface mounted onto a PCB. This component 100' can also provide power tothe rest of the circuit on the PCB, or act as an energy-booster when neededby the other PCB components 1520, or as a back-up energy source.

Thus, with reference also to Figure 1, there is disclosed herein a component100' for surface mounting onto a PCB 1510. The component comprises abobbin arrangement with an electromagnetic coi| 4 and a magnetic core 2, amagnet 1 associated with a mass inertia, resiliently held in an equilibriumposition P with respect to the bobbin arrangement 4,2, whereby the magnet 1is arranged to reciprocate in relation to the bobbin arrangement 4,2 in responseto mechanical impact.

According to some aspects, the component comprises pads for connecting the bobbin arrangement to a circuit 1520 on a PCB 1510 via surface mounting.

According to some other aspects, the component comprises any of the sensorcircuit 5 and/or the energy storage device 6 discussed above, wherein thecomponent is arranged to be surface mounted onto a PCB, thereby connectingthe sensor circuit 5 and/or energy storage device 6 to other components onthe PCB.

Figure 10 schematically illustrates, in terms ofa number of functional units, thecomponents of the sensor circuit 5 according to an embodiment of thediscussions herein. Processing circuitry 1010 is provided using anycombination of one or more of a suitable central processing unit CPU,multiprocessor, microcontroller, digital signal processor DSP, etc., capable ofexecuting software instructions stored in a computer program product, e.g. inthe form ofa storage medium 1030. The processing circuitry 1010 may furtherbe provided as at least one application specific integrated circuit ASIC, or field programmable gate array FPGA.

Particularly, the processing circuitry 1010 is configured to cause the sensorcircuit 5 to perform a set of operations, or steps, such as the methodsdiscussed in connection to Figure 4. For example, the storage medium 1030may store the set of operations, and the processing circuitry 1010 may beconfigured to retrieve the set of operations from the storage medium 1030 tocause the control unit 140 to perform the set of operations. The set ofoperations may be provided as a set of executable instructions. Thus, the processing circuitry 1010 is thereby arranged to execute methods as hereindisclosed.

The storage medium 1030 may also comprise persistent storage, which, forexample, can be any single one or combination of magnetic memory, opticalmemory, solid state memory, memory card or even remotely mounted memory.

The sensor circuit 5 may further comprise an interface 1020 forcommunications with at least one external device. As such the interface 1020may comprise one or more transmitters and receivers, comprising analogueand digital components and a suitable number ports for wireline or wireless communication.

The processing circuitry 1010 controls the general operation of the sensorcircuit 5 e.g. by sending data and control signals to the interface 1020 and thestorage medium 1030, by receiving data and reports from the interface 1020,and by retrieving data and instructions from the storage medium 1030. Othercomponents, as well as the related functionality, ofthe control node are omitted in order not to obscure the concepts presented herein.

Figure 11 schematically illustrates a computer program product 1100,comprising a set of operations 1110 executable by the sensor circuit 5. Theset of operations 1110 may be loaded into the storage medium 1030 in thesensor circuit 5. The set of operations may correspond to the methodsdiscussed above in connection to Figure 5 or to the different operations by theshock sensors discussed above. ln the example of Figure 11, the computer program product 1100 is illustratedas an optical disc, such as a CD (compact disc) or a DVD (digital versatile disc)or a Blu-Ray disc. The computer program product could also be embodied asa memory, such as a random-access memory (RAM), a read-only memory(ROM), an erasable programmable read-only memory (EPROM), or anelectrically erasable programmable read-only memory (EEPROM) and moreparticularly as a non-volatile storage medium of a device in an external memory such as a USB (Universal Serial Bus) memory or a Flash memory, such as a compact Flash memory. Thus, while the computer program is hereschematically shown as a track on the depicted optical disk, the computerprogram can be stored in any way which is suitable for the computer programproduct.

Claims (10)

1. A shock sensor arrangement (100, 100', 200), comprising a bobbin arrangement with an electromagnetic coil (4) and a magnetic core(2), a magnet (1) associated with a mass inertia, resiliently held in an equilibriumposition (P) with respect to the bobbin arrangement (4,2), whereby the magnet(1) is arranged to reciprocate in relation to the bobbin arrangement (4,2) inresponse to mechanical impact, wherein the magnet (1) is held in theequilibrium position (P) by a magnetic force generated between the magnet(1) and the magnetic core (2) so that a magnetic flow of the magnet (1) isclosed in a magnetic circuit comprising the magnetic core (2), and a sensor circuit (5) configured to detect an electrical current or voltagegenerated in the electromagnetic coil (4) by the reciprocating magnet (1),thereby registering the mechanical impact.

2. The shock sensor arrangement (100, 100', 200) according to claim 1,comprising an energy storage device (6) configured to store electrical energygenerated by the bobbin arrangement (4, 2), wherein the energy storagedevice (6) is arranged to at least partly power the sensor circuit (5).

3. The shock sensor arrangement (100, 100', 200) according to anyprevious claim, wherein the sensor circuit (5) is arranged to detect mechanicalimpact by comparing the detected electrical current or voltage to a threshold value.

4. The shock sensor arrangement (100, 100', 200) according to anyprevious claim, wherein the sensor circuit (5) is arranged to determine a shockseverity value based on a detected electrical current magnitude and/or based on an electrical voltage magnitude.

5. The shock sensor arrangement (100) according to any previous claim,wherein the magnet (1) is arranged to be resiliently held inside a tubular structure (3) configured to guide the magnet along the axis (A).

6. The shock sensor arrangement (100, 100', 200) according to anyprevious claim, comprising a communication circuit (11) configured tocommunicate over an interface with an external device (12) or a remote server(13).

7. The shock sensor arrangement (100, 100', 200) according to anyprevious claim, configured to be surface mounted to a printed circuit board.

8. A shot counter for a weapon with recoi| comprising the shock sensorarrangement (100, 100', 200) according to any previous claim, wherein theshock sensor arrangement (100, 100', 200) is arranged to detect when theweapon is fired, and to store the number of fired shots in a storage medium(1030).

9. The shot counter according to c|aim 8, wherein the shock sensorarrangement (100, 100', 200) is configured to record a vibration signature(1210) and to compare the recorded vibration signature to a set of storedvibration signatures (1220, 1230, 1240) associated with respective types ofammunition, wherein the shock sensor arrangement (100, 100', 200) isconfigured to maintain separate shot counters for at least two different types of ammunitions.

10. An actuator comprising; a bobbin arrangement with an electromagnetic coil (4) and a magnetic core(2), a magnet (1) associated with a mass inertia, resiliently held in an equilibriumposition (P) with respect to the bobbin arrangement (4,2), whereby the magnet(1) is arranged to reciprocate in relation to the bobbin arrangement (4,2) inresponse to a current or voltage in the bobbin arrangement, wherein themagnet (1) is held in the equilibrium position (P) by a magnetic force generatedbetween the magnet (1) and the magnetic core (2) so that a magnetic flow ofthe magnet (1) is closed in a magnetic circuit comprising the magnetic core(2), and a sensor circuit (5) configured to generate the current or voltage in the bobbinarrangement in response to a trigger signal, thereby causing a mechanicalmotion by the magnet.