Research Article A Feasibility Study of a Noncontact ...downloads.hindawi.com/journals/js/2015/126935.pdf · Torque can be read by examining the phase di erence between two induction

Research ArticleA Feasibility Study of a Noncontact Torque Sensor withMultiple Hall Sensors

Kyungshik Lee and Chongdu Cho

Department of Mechanical Engineering Inha University Graduate School 100 Inha-ro Nam-Gu Incheon 402-751 Republic of Korea

Correspondence should be addressed to Chongdu Cho cdchoinhaackr

Received 29 October 2014 Revised 16 December 2014 Accepted 29 December 2014

Academic Editor Luisa Torsi

Copyright copy 2015 K Lee and C Cho This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The feasibility of a noncontact sensor is investigatedThis type of sensor can potentially be used for torquemeasurement in a speed-variable power transmission system Torque can be read by examining the phase difference between two induction signals fromrespective magnetic sensors that detect the magnetic field intensity of permanent magnets mounted on the surface of a shaft inrotation A real-time measuring algorithm that includes filtering and calibration is adopted to measure the torque magnitude It isshown that this new torque sensor can perform well under rotation speeds ranging from 300 rpm to 500 rpm As an interim reportrather than a complete development this work demonstrates the feasibility of noncontact torque measurement by monitoring amagnetic field The result shows an error of less than 2 within the full test range which is a sufficient competitive performancefor commercial sensors The price is very low compared to competitors in the marketplace and the device does not require specialhandling of the shaft of the surface

1 Introduction

Torque is an axially twisting moment that is measured onthe shafts of rotating machines For example in automobileselectric motors and helicopters the technique of torquefeedback control is needed to reduce fuel consumptionand improve ride comfort Nonetheless no torque mea-surement solution has proven to be reliable and repeatablefor successful commercialization in the marketplace Thisholds true especially in the automotive industry which seeksto achieve a low-cost and in situ dynamic torque controlwithout major change of existing designs The installationmethod faces great difficulty because it requires reliable andavailable strain-gauge-type torque sensors in automobilesFor example common strain-gauge-type sensors must beinserted into themiddle of the power transmission shaftusinga slip ring which requires critical maintenance Anotherdifficulty is the necessity of keeping performance at a high oiltemperature of approximately 200∘C The strain-gauge-typesensor is normally reliable only under 80∘C and it is difficultto seal against hot oil

To resolve these difficulties studies [1] have pursuedthe development of a high-performance torque sensor with

a reasonable price Among noncontact-type sensors amagnetostrictive-type torque sensor uses one of the potentialtechniques which is based on the iteration of the periodictime difference [2ndash4] Contactless technique sensors can beused with fewer shaft design changes The elastomagneticeffect of ferromagnetic materials exhibits the phenomenonthat strain or stress induced by the torque on the shaftcan change the magnetic properties of a magnetostrictivematerial and cause hysteresis deformation and permeability[5] A frequency modulation- (FM-) type wireless CMOS ICmagnetoimpedance (MI) sensor is constructed using flash-annealed amorphous wire [6] A number of resonant wirelesssurface acoustic wave (SAW) sensors have been developedfor measuring temperature pressure and torque in variousautomotive applications [7] An embedded capacitive gratingtorque sensor andmeasuring systemhave beendeveloped [8]The capacitive torque sensor is composed of two capacitivedisplacement sensors in order to measure a twist angle [9]

Moving magnet technologies (MMT) and the SAW-typesensor are used successfully in the current market but theinstallation of these items requires extensive modification ofthe target shaft The best advantage of the new methods isthat there are no critical design changes to the current system

Hindawi Publishing CorporationJournal of SensorsVolume 2015 Article ID 126935 6 pageshttpdxdoiorg1011552015126935

2 Journal of Sensors

(1) (2) (3) (4)

Figure 1 Photo of test bench

20

40

60

80

100

478 490 500 510 520 530 540 550 560 570 578

Time (s)

Torq

ue(N

middotm)

minus5

Figure 2 Front screenshot of torque sensor program

For example MMT can measure the shaft angle between tworotating shafts that are linked by a torsion bar [10] but oursensor directly measures the distortion angle of a shaft

This paper proposes a new sensor concept and measure-ment principle using (1) where the shaft twist angle in alinear elastic state is proportional to the net in situ torque ofa prismatic circular-shaped shaft When a shaft has a radius119877 and a length 119871 and the shear modulus of the shaft materialis 119866 torque 119879 has a relation with a twisting angleΦ in rad

119879 =1205871198774

119866

2119871Φ (1)

On the other hand a traditional optical sensor may beused to measure a reflected distance using a specially pro-cessed surface of the axis to detect a twist angle Howeverthis method is limited in some special environments In thisstudy we propose a new torque sensor in which multiplepermanent magnet pairs make the sensor applicable even inharsh and hot environments such as oil and dust in workingmachines Increasing the longitudinal separation 119871 of thetwo Hall sensors improves the accuracy of measurementsHowever a major weak point is that not every target systemhas sufficient space to do so

2 Measurement System Configuration

21 Hardware Configuration A test bench which is detailedin Figure 1 is produced to evaluate the feasibility of thenewly proposed torque sensor The bench consists of (1) afriction powder clutch (2) commercial inline torque sensorsfor comparison purposes (3) the torque sensor under devel-opment in this study and (4) a servomotor that connects theshafts couplings data acquisition (DAQ) card and a personalcomputer

For analysis and visual results we used the LabVIEWprogram as shown in Figure 2 The red line indicates thedata from the inline-type sensor and the white line is fromthe new sensor The dialogue shows that the compared data

Magnets

x y z stage

Figure 3 Schematic of torque sensor bench and shaft

from the strain-gauge-type sensor can be used as evaluationcriteria and to help develop the new sensor

A Hall sensor is a device that proportionally converts arecognized magnetic field strength to DC voltage which istypically used for position recognition and detecting rotationspeed Aichi Steelrsquos AMI302 sensor has high sensitivity andlow magnetic field strength (full scale 2 Gauss) and canmeasure a complex three-axis magnetic field The AMI302is not capable of measuring the magnetic field in the threeaxis directions at the same time Measuring in the 119909 119910 and 119911directions can be selected by a digital signal

In order to change the distance between the four pairs ofmagnets and a pair of AMI302 magnetic sensors a precisionbench was fabricated with a 3D adjustable stage as shownin Figure 3 An optimum gap between the sensor and themagnet was obtained from the results of experiments In theexperimental results the optimum gap was determined bythe position that measuredmagnetic field strength within therange of the full scale of the sensor to detect clear signals

A servomotor (Mitsubishi Electric Corporation MR-J2S-12KA with a maximum torque of 200Nsdotm) is used in thisstudy for dynamic testing to apply the desired rotationalspeed according to an external analog control signal providedby the software To remove the noise generated by the high-capacity servomotor ferrite cores and noise-shielding cablewere employed A powder clutch to brake the torsional shaftwas mounted on the opposite side of the motor

The proposed commercial sensor (Haiam HKT-TRCstrain-gauge type) is installed and acts as a reference tocompare the torque This sensor has a real-time feedbackfunction and can measure torque up to 200Nsdotm as well asimportant specific nonlinearities The sensorrsquos hysteresis andrepeatability of plusmn05 make it a good candidate for a precisecomparison

22Magnet Selection Aneodymiummagnet (2mmhexagonsize) is designed as a test magnet The rubber magnet wasused in previous experiments [11ndash13] and did not exhibit goodrepeatabilityThis problem is believed to be a result of a weakmagnetic field high sensitivity to electrical noise generated bythe servomotor and various test equipment and the magnetrsquosnonlinear deformation characteristics

Journal of Sensors 3

The neodymium magnet a widely used type of rare-earth magnet is a permanent magnet made from an alloy ofneodymium iron and boron to form the Nd

2Fe14B tetrago-

nal crystalline structure [14] The most outstanding charac-teristic of the neodymium magnet is related to temperatureenergy loss in the power transmission shaft is mainly dissi-pated as heat energy The Curie temperature of the magnet is310ndash370∘C and its maximum operating temperature is 80ndash200∘C The density of the magnet is 74ndash76 gcm3 so themagnets in the test are just 74mg each Those weights canbe ignored by the dynamic unbalanced mass on the shaft

3 Signal Processing and Algorithm

31 Noise-Filtering Method When the neodymium magnetis set at a 12mm gap from the sensor the maximum valueof the measured magnetic field reaches a sufficient valueof 2 Gauss The noise and Hall-effect (HE) sensor output-signal contrast ratio are reduced to 10 which is helpful inimproving precision

Nevertheless many large-capacity electrical componentssuch as the servomotor can generate considerable high-frequency noise In order to remove this noise a low-passfilter with a 60Hz or higher cutoff frequency is applied bysoftware The major signal frequency is approximately 33Hzat 500 rpm To increase the reliability of the data a highercutoff frequency is useful at 500 rpm or higher If a newmeasurement system is applied to an internal combustionengine (as in the transportation industry) and reduces thedistance between the HE sensor and DAQ board the signalwould be much clearer and the cutoff frequency of the low-pass filter (LPF) could be increased

A spline fitting [15] and averaging filter [16] are appliedthrough LabVIEW to obtain a smooth curve in which todetect peaks of the signal

32 Theoretical and Experimental Formula The concept ofthis experiment is to develop a detection method of corre-sponding individual peaks of magnetic field strength wavesto estimate a twisted angle Therefore detecting peaks froma signal acquisition is the most important factor Based on adiscrete data set a best-fit spline wave is determined by the119899-dimensional spline fitting process data from which a peakcan be estimated

The correlation between torque and twist angle can beexpressed in the following equation Equation (2) is a modi-fied version of (1) and can be applied to four magnets that areconfigured in pairs where the measured time is Δ119905

119894and the

initial time is Δ1199051015840119894

119879 =1198991205872

1198774

119866

60119871

1

4

4

sum

119894=1

(Δ119905119894minus Δ1199051015840

119894

)

=1198991205872

1198774

119866

60119871Δ119905mean = 119862Δ119905mean

(2)

Δ119905mean is checked from the data as a unique parameter oftorque measurement if rotational speed 119899 in radsec is fixed

The shear modulus is assumed to be constant because thetemperature gap is smaller than 10∘C in this study

The constant value 119862 in (2) can be calculated easilyas 19 times 106 at 400 rpm and 140 times 106 at 3000 rpm Tomaintain a calculated torque value of one sampling periodless than 1Nsdotm the system should be designed with sensorsand circuits that have sampling frequencies greater than thecalculated constant value ADAQ card is used in experimentswith a maximum sampling frequency of 1024 kHz In orderto compensate for the problem of higher data acquisitionfrequency the calculation takes the average data of the pastfew periods and fits the curve

4 Results and Discussion

The four magnet pairs are mounted on the shaft at 90∘ incre-ments to compensate for the dynamic reaction during rota-tionThe effect of pairing themagnets and the calibration dataare analyzed in this chapterThe experiments can be classifiedinto three steps

The first step is calibration to obtain two critical param-eters by measuring an initial angle difference between eachpair of magnets and the twist angle per applied unit torque(in radNsdotm) In this step the role of the commercial sensoris to act as a calibrator

The second step is the repeated data correction of the firststep to check long-term variation and repeatability

The last step involves comparing the respective data of thecommercial sensor and the calculated data from the proposedsensor while changing the rotation speed and applied torqueThis step confirms the repeatability and reproducibility of thenew suggested measurement method as a torque meter

41 Repeatability of the Initial Interval Measurement Test Apair of sensors and four pairs of magnets are rarely alignedin an axial position with a no-load condition because it isimpossible to install them on an exact axial line Thereforeone of the important tasks of sensor calibration is to readthe initial deviation of each magnet pair at a no-load orspecified torque condition In order to confirm repeatabilityand reliability as a torquemeasurement sensor this parameterhas no variation in the short or long term

As with the experimental results in Figure 4 the initialinterval measure is highly irregular at 200 rpm We believethis results from the mechanical gap of the ball bearings andthe misalignment of the entire test system A system thatmeasures torque to provide feedback for a closed-loop systemmust have a highly precious mechanical balance

The data of 300 rpm were compared in Figure 5 Thereis a nonlinear region that has unexpected errors in the low-torque range This may occur because the magnets wereattached using epoxy an adhesive material that may notdeform linearly or uniformly at the beginning of the twistingof the shaft

In order to consider removing the effect of temperaturea magnet was mounted with AXIA super glue which canwithstand temperatures up to 120∘C without changing itsphysical properties The variable dependent on temperature


128

130

132

134

136

200 300 400 500Test rotation speed (rpm)

Sensor position

Initi

al d

etec

ted

sens

or d

iffer

ence

times1

00

0(r

ad)

Figure 4 Initial angle interval of attached sensors on the shaft

00

05

10

15

0 20 40 60 80 100

Nonlinearregion

1st pair2nd pair

3rd pair4th pair

Sensor position

minus15

minus10

minus05

Test torque

alig

ned

at5

0

Mea

sure

d tw

ist an

gletimes

10

00

N

middotm (r

ad)

(Nmiddotm)

Figure 5 Nonlinear relationship interval at low torque (300 rpm)

in (1) is shearmodulus119866This can be compensatedwith a 4th-order polynomial equation but we ignore the temperatureeffect because the temperature difference is only 5∘C duringall experiments

42 Speed Range for Sensor Test Initially the targeted speedrange for the experiment was 100ndash1000 rpm However above600 rpm we cannot continuously increase the torque morethan 100Nsdotm because the current test brake system onlycools down by air In addition the chosen NIrsquos DAQ cardcan operate only at 1024 kHz maximum This is thought tolimit the maximum shaft speed to under 600 rpm Figure 6shows the measured data in rotational speed versus torqueper twist angle and denotes the measured twist angle with atorque increasing by 100Nsdotm every 5Nsdotm As in Figure 6 therepeated deviations and twist angle quantitative differencesunder 250 rpm show very unstable results

20

22

24

26

28

30

32

34

36

38

40

100 150 200 250 300 350 400 450 500Test rotation speed (rpm)

Twist

angl

e per

uni

t tor

que (

120583ra

dN

middotm)

Figure 6 Twist angle per unit torque in the 100ndash500 rpm range

These results can be explained in two ways The firstcause is the misalignment of the shafts The coupling jointedwith the torque motor the proposed torque sensor the com-mercial sensors and the friction clutch make a comparablevibration The other cause is a position mismatch of thenew sensor and the strain-gauge-type sensor between thetwo sensors are ball bearings that cause a loss in torquebecause the bearings exhibit different friction coefficients fora variable speed range

For the present sensor system the general quality oftorque measurements is improved except in the low-rpmrange For better dynamic torquemeasurement in the presentsystem we isolated the torque-measuring module and shaftfrom outside vibration The sensor body would move by arelativemotion tomaintain the distance between themagnetsand the sensors

However we failed to obtain an ideal uniform valueduring testing We observe that the cause of this failure isprobably the ball-bearing gap on both sides of the modules

Figure 7 shows average twist angles from the proposedsensor system for each applied torque in the 200ndash500 rpmrange The trend lines with the least-square method almostoverlap This means the system is accurate in the 300ndash500 rpm range

43 Comparison of Experimental Data In a previousapproach [13] with a pair of magnets the error was notnegligible for every rotating speed that could not compensatefor the shaft vibration After installing the four pairs ofmagnets at 90∘ intervals the four cycles of sine waves can beacquired from one motor rotation cycle The signals fromeach pair of magnets can compensate for the vibration of themagnet effect that is located at a 180∘ difference The averageof the values of repeatability in the multisensor methodimproved significantly Experiments in the 300ndash500 rpmrange were carried out with less than 2 of linear andrepeatable data

Figure 8 shows real measuring data and the averagevalue with each pair of sensors at 400 rpm The solid line


00

05

10

15

0 10 20 30 40 50 60 70 80 90 100minus15

minus10

minus05

200 rpm300 rpm

400 rpm500 rpm

Mea

sure

d tw

ist an

gletimes

10

00

al

igne

d at

50

Nmiddotm

(rad

)

Test torque (Nmiddotm)

Figure 7 Measured average twist angle at 200ndash500 rpm

00

05

10

15

20

25

0 20 40 60 80 100

Average

Sensor position

Twist

ed an

gletimes

10

00

(rad

)

y = 00228x minus 00063


Figure 8 Measured twist angle of four pairs of sensors at 400 rpm

represents the linearized average dataThe signal data for eachpair do not seem to exhibit linearity However every point(lowast) of the average twist angle and the linearized solid lineexhibit a deviation that is smaller than 2 Hence regardingnonlinearity we recognize that the multimagnet method issuperior to the single-magnet method

After we calibrated the new torque meter we comparedthe above theoretical data in (1) and the experimental data at400 rpm

Φ =2119871

1205871198774119866119879 =

2 lowast 006

120587 lowast 001254 lowast 70 lowast 109119879

= 2236 lowast 10minus5

(radN sdotm) lowast 119879(3)

where 119871 = 006m 119877 = 00125m and 119866 = 70GPa Theconstant values (radNsdotm) are 991 and matched the slopeof Figure 8 of the experimental results Where the theoret-ical slope value is constantmdashwhich is currently tested with

the experimental devicesmdashthe high matching ratio showsthat the new torque measuring system exhibits better accu-racy during experiments

5 Conclusion

In this study a noncontact-type torque sensor was evaluatedto examine in variable torque condition its performancethrough the test bench with a rotating shaft The shafttorque value was obtained by using four pairs of permanentneodymium magnets attached to the surface of the shaft anda pair of magnetic Hall sensors The measured magnetic fieldshows the intervals between peaks In addition the frequencydetected by the sensor helps to calculate rotational speedwhich is the most important variable when converting fromthe time gap to a twisted angle

The repeatability of the measured initial-angle differenceat each rotational speed between magnets is less than 2This does not appear to satisfy the needs of the automotiveindustry However we expect that the result will improveand become more accurate when we employ a higher-gradehardware system

To guarantee the performance of the torque sensor acalibration step or phase correction is necessary Sufficientdata regarding constraint material properties and geometryare required in order to apply them to a successful torquesensor by assuming a linear deformation in the rotationaldirection

Specifications for the commercial vehicle industry areneeded and future tests should include these important keypoints

(i) To eliminate vibration effects the sensor should com-plement any effect by the fixed part of the axis of rota-tion

(ii) Measurements should be possible even at high rota-tional speeds To increase the effectiveness of thehardware configuration and the algorithm for high-speed processing of data high-speed data acquisitionmust be possible

(iii) Measurements over a low-torque region need to beimproved with regard to linearity in order to obtainaccurate data aftermodifications to the test bench andrealignment shaft and after upgrading the motor orbearings

(iv) A molding process is needed to protect the Hall sen-sor from oil and dust in actual conditions and toreduce the size of the entire module To ensure thatoperation is free from operating temperature weshould employ the calibration and repeatability testprocess because the elastic modulus is temperaturedependent

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper


Acknowledgment

This work was supported by Inha University

References

[1] W J Fleming ldquoOverview of automotive sensorsrdquo IEEE SensorsJournal vol 1 no 4 pp 296ndash308 2001

[2] T Tsujisawa and K Yamakawa ldquoImprovement of the angular-dependent noise in a magneto-striction type torque sensorrdquoInternational Journal of Automotive Engineering vol 2 no 3 pp75ndash80 2011

[3] T Tsujisawa and K Yamakawa ldquoProposal and performanceevaluation of a magneto-striction type torque sensor consistingof small-sized coils connected in seriesrdquo ISRN Electronics vol2012 Article ID 738597 8 pages 2012

[4] H Wakiwaka and M Mitamura ldquoNew magnetostrictive typetorque sensor for steering shaftrdquo Sensors and Actuators APhysical vol 91 no 1-2 pp 103ndash106 2001

[5] H Ruser U Troltzsch and M Horn ldquoLow-cost magnetictorque sensor principlerdquo Sensors vol 2 no 2 pp 901ndash904 2002

[6] CM Cai KMohri Y Honkura andM Yamamoto ldquoImprovedpulse carrier MI effect by flash anneal of amorphous wires andFM wireless CMOS IC torque sensorrdquo IEEE Transactions onMagnetics vol 37 no 4 pp 2038ndash2041 2001

[7] V Kalinin ldquoWireless physical SAW sensors for automotiveapplicationsrdquo in Proceedings of the IEEE International Ultrason-ics Symposium (IUS rsquo11) pp 212ndash221 October 2011

[8] R Xie T Ma Y Wu and Z Xie ldquoStudy on torque measure-ment of revolving shaft based on capacitive grating sensingtechnologyrdquo in Proceedings of the International Conference onElectronic andMechanical Engineering and InformationTechnol-ogy (EMEIT rsquo11) vol 9 pp 4520ndash4523 August 2011

[9] R F Wolffenbuttel and J A Foerster ldquoNoncontact capacitivetorque sensor for use on a rotating axlerdquo IEEE Transactions onInstrumentation and Measurement vol 39 no 6 pp 1008ndash10131990

[10] D Angleviel D Frachon and G Masson ldquoDevelopment of acontactless hall effect torque sensor for electric power steeringrdquoSAE Technical Paper 2006-01-0939 SAE 2006

[11] C Piao Study on wireless torque sensor by monitoring magneticfield [PhD thesis]Mechanical EngineeringDepartment INHAUniversity Incheon Korea 2006

[12] G ShiResearch of a non-contact torque sensor based onmagneticfield detecting [MS thesis] Department of Mechanical Engi-neering Inha University Incheon Republic of Korea 2011

[13] G Shi N Wang and C Cho ldquoDesign of a new non-contacttorque sensor for rotating stepped shaft bymonitoringmagneticfieldrdquo Applied Mechanics andMaterials vol 44ndash47 pp 547ndash5512010

[14] J Fraden Handbook of Modern Sensors Physics Designs andApplications Springer New York NY USA 4th edition 2010

[15] T C Lee ldquoOn algorithms for ordinary least squares regressionspline fitting a comparative studyrdquo Journal of Statistical Com-putation and Simulation vol 72 no 8 pp 647ndash663 2002

[16] J Astola P Haavisto and Y Neuvo ldquoVector median filtersrdquoProceedings of the IEEE vol 78 no 4 pp 678ndash689 1990

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RoboticsJournal of

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Active and Passive Electronic Components

Control Scienceand Engineering

Journal of



RotatingMachinery


Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design



Shock and Vibration


Civil EngineeringAdvances in

Acoustics and VibrationAdvances in



Electrical and Computer Engineering

Journal of

Advances inOptoElectronics


Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of


Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014


Chemical EngineeringInternational Journal of Antennas and

Propagation




Navigation and Observation



DistributedSensor Networks



(1) (2) (3) (4)

Figure 1 Photo of test bench

20

40

60

80

100

478 490 500 510 520 530 540 550 560 570 578

Time (s)

Torq

ue(N

middotm)

minus5

Figure 2 Front screenshot of torque sensor program

For example MMT can measure the shaft angle between tworotating shafts that are linked by a torsion bar [10] but oursensor directly measures the distortion angle of a shaft

This paper proposes a new sensor concept and measure-ment principle using (1) where the shaft twist angle in alinear elastic state is proportional to the net in situ torque ofa prismatic circular-shaped shaft When a shaft has a radius119877 and a length 119871 and the shear modulus of the shaft materialis 119866 torque 119879 has a relation with a twisting angleΦ in rad

119879 =1205871198774

119866

2119871Φ (1)

On the other hand a traditional optical sensor may beused to measure a reflected distance using a specially pro-cessed surface of the axis to detect a twist angle Howeverthis method is limited in some special environments In thisstudy we propose a new torque sensor in which multiplepermanent magnet pairs make the sensor applicable even inharsh and hot environments such as oil and dust in workingmachines Increasing the longitudinal separation 119871 of thetwo Hall sensors improves the accuracy of measurementsHowever a major weak point is that not every target systemhas sufficient space to do so

2 Measurement System Configuration

21 Hardware Configuration A test bench which is detailedin Figure 1 is produced to evaluate the feasibility of thenewly proposed torque sensor The bench consists of (1) afriction powder clutch (2) commercial inline torque sensorsfor comparison purposes (3) the torque sensor under devel-opment in this study and (4) a servomotor that connects theshafts couplings data acquisition (DAQ) card and a personalcomputer

For analysis and visual results we used the LabVIEWprogram as shown in Figure 2 The red line indicates thedata from the inline-type sensor and the white line is fromthe new sensor The dialogue shows that the compared data

Magnets

x y z stage

Figure 3 Schematic of torque sensor bench and shaft

from the strain-gauge-type sensor can be used as evaluationcriteria and to help develop the new sensor

A Hall sensor is a device that proportionally converts arecognized magnetic field strength to DC voltage which istypically used for position recognition and detecting rotationspeed Aichi Steelrsquos AMI302 sensor has high sensitivity andlow magnetic field strength (full scale 2 Gauss) and canmeasure a complex three-axis magnetic field The AMI302is not capable of measuring the magnetic field in the threeaxis directions at the same time Measuring in the 119909 119910 and 119911directions can be selected by a digital signal

In order to change the distance between the four pairs ofmagnets and a pair of AMI302 magnetic sensors a precisionbench was fabricated with a 3D adjustable stage as shownin Figure 3 An optimum gap between the sensor and themagnet was obtained from the results of experiments In theexperimental results the optimum gap was determined bythe position that measuredmagnetic field strength within therange of the full scale of the sensor to detect clear signals

A servomotor (Mitsubishi Electric Corporation MR-J2S-12KA with a maximum torque of 200Nsdotm) is used in thisstudy for dynamic testing to apply the desired rotationalspeed according to an external analog control signal providedby the software To remove the noise generated by the high-capacity servomotor ferrite cores and noise-shielding cablewere employed A powder clutch to brake the torsional shaftwas mounted on the opposite side of the motor

The proposed commercial sensor (Haiam HKT-TRCstrain-gauge type) is installed and acts as a reference tocompare the torque This sensor has a real-time feedbackfunction and can measure torque up to 200Nsdotm as well asimportant specific nonlinearities The sensorrsquos hysteresis andrepeatability of plusmn05 make it a good candidate for a precisecomparison

22Magnet Selection Aneodymiummagnet (2mmhexagonsize) is designed as a test magnet The rubber magnet wasused in previous experiments [11ndash13] and did not exhibit goodrepeatabilityThis problem is believed to be a result of a weakmagnetic field high sensitivity to electrical noise generated bythe servomotor and various test equipment and the magnetrsquosnonlinear deformation characteristics



2Fe14B tetrago-








119894and the

initial time is Δ1199051015840119894

119879 =1198991205872

1198774

119866

60119871

1

4

4

sum

119894=1

(Δ119905119894minus Δ1199051015840

119894

)

=1198991205872

1198774

119866

60119871Δ119905mean = 119862Δ119905mean

(2)














128

130

132

134

136


Sensor position

Initi

al d

etec

ted

sens

or d

iffer

ence

times1

00

0(r

ad)


00

05

10

15

0 20 40 60 80 100

Nonlinearregion

1st pair2nd pair

3rd pair4th pair

Sensor position

minus15

minus10

minus05

Test torque

alig

ned

at5

0

Mea

sure

d tw

ist an

gletimes

10

00

N

middotm (r

ad)

(Nmiddotm)




20

22

24

26

28

30

32

34

36

38

40


Twist

angl

e per

uni

t tor

que (

120583ra

dN

middotm)









00

05

10

15

0 10 20 30 40 50 60 70 80 90 100minus15

minus10

minus05

200 rpm300 rpm

400 rpm500 rpm

Mea

sure

d tw

ist an

gletimes

10

00

al

igne

d at

50

Nmiddotm

(rad

)



00

05

10

15

20

25

0 20 40 60 80 100

Average

Sensor position

Twist

ed an

gletimes

10

00

(rad

)

y = 00228x minus 00063





Φ =2119871

1205871198774119866119879 =

2 lowast 006






5 Conclusion












Acknowledgment


References



















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











2Fe14B tetrago-








119894and the

initial time is Δ1199051015840119894

119879 =1198991205872

1198774

119866

60119871

1

4

4

sum

119894=1

(Δ119905119894minus Δ1199051015840

119894

)

=1198991205872

1198774

119866

60119871Δ119905mean = 119862Δ119905mean

(2)














128

130

132

134

136


Sensor position

Initi

al d

etec

ted

sens

or d

iffer

ence

times1

00

0(r

ad)


00

05

10

15

0 20 40 60 80 100

Nonlinearregion

1st pair2nd pair

3rd pair4th pair

Sensor position

minus15

minus10

minus05

Test torque

alig

ned

at5

0

Mea

sure

d tw

ist an

gletimes

10

00

N

middotm (r

ad)

(Nmiddotm)




20

22

24

26

28

30

32

34

36

38

40


Twist

angl

e per

uni

t tor

que (

120583ra

dN

middotm)









00

05

10

15

0 10 20 30 40 50 60 70 80 90 100minus15

minus10

minus05

200 rpm300 rpm

400 rpm500 rpm

Mea

sure

d tw

ist an

gletimes

10

00

al

igne

d at

50

Nmiddotm

(rad

)



00

05

10

15

20

25

0 20 40 60 80 100

Average

Sensor position

Twist

ed an

gletimes

10

00

(rad

)

y = 00228x minus 00063





Φ =2119871

1205871198774119866119879 =

2 lowast 006






5 Conclusion












Acknowledgment


References



















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










128

130

132

134

136


Sensor position

Initi

al d

etec

ted

sens

or d

iffer

ence

times1

00

0(r

ad)


00

05

10

15

0 20 40 60 80 100

Nonlinearregion

1st pair2nd pair

3rd pair4th pair

Sensor position

minus15

minus10

minus05

Test torque

alig

ned

at5

0

Mea

sure

d tw

ist an

gletimes

10

00

N

middotm (r

ad)

(Nmiddotm)




20

22

24

26

28

30

32

34

36

38

40


Twist

angl

e per

uni

t tor

que (

120583ra

dN

middotm)









00

05

10

15

0 10 20 30 40 50 60 70 80 90 100minus15

minus10

minus05

200 rpm300 rpm

400 rpm500 rpm

Mea

sure

d tw

ist an

gletimes

10

00

al

igne

d at

50

Nmiddotm

(rad

)



00

05

10

15

20

25

0 20 40 60 80 100

Average

Sensor position

Twist

ed an

gletimes

10

00

(rad

)

y = 00228x minus 00063





Φ =2119871

1205871198774119866119879 =

2 lowast 006






5 Conclusion












Acknowledgment


References



















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










00

05

10

15

0 10 20 30 40 50 60 70 80 90 100minus15

minus10

minus05

200 rpm300 rpm

400 rpm500 rpm

Mea

sure

d tw

ist an

gletimes

10

00

al

igne

d at

50

Nmiddotm

(rad

)



00

05

10

15

20

25

0 20 40 60 80 100

Average

Sensor position

Twist

ed an

gletimes

10

00

(rad

)

y = 00228x minus 00063





Φ =2119871

1205871198774119866119879 =

2 lowast 006






5 Conclusion












Acknowledgment


References



















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










Acknowledgment


References



















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









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