Simulation of an Industrial Environment and overview of test results J. CATRYSSE; KHBO J. Rayée, D....

Simulation of an Industrial Simulation of an Industrial Environment and overview of Environment and overview of

test resultstest results

J. CATRYSSE; KHBOJ. CATRYSSE; KHBO

J. Rayée, D. Degrendele; KHBOJ. Rayée, D. Degrendele; KHBO

Increasing use of wireless Increasing use of wireless systemssystems

Advantages:Advantages:• flexibilityflexibility• less wiring neededless wiring needed• still improving (power management, still improving (power management,

interference protection, …)interference protection, …) Disadvantages:Disadvantages:

• lack of robustness against mechanical and lack of robustness against mechanical and electrical constraintselectrical constraints

• Wired systems are usually more robustWired systems are usually more robust

Lack of information about Lack of information about industrial environmentsindustrial environments

Not much information available about Not much information available about performance of wireless technologies in performance of wireless technologies in heavy industrial environments. heavy industrial environments.

In most literature only office use is In most literature only office use is considered.considered.

3 ways for the characterisation 3 ways for the characterisation of an industrial environmentof an industrial environment

Theoretical modelsTheoretical models• difficulty to quantify parametersdifficulty to quantify parameters

In situ measurementsIn situ measurements• time consumingtime consuming• difficulty to implement in real machinerydifficulty to implement in real machinery

Simulation setupSimulation setup• controlled measurement environmentcontrolled measurement environment• all disturbance effects can be taken into accountall disturbance effects can be taken into account• influence of the effects can be tested separately influence of the effects can be tested separately

or togetheror together

Wireless systems technologyWireless systems technology

Wireless systems are protected against Wireless systems are protected against possible disturbances by using (encoding, possible disturbances by using (encoding, spread spectrum, protocol, …)spread spectrum, protocol, …)

Makes use of ISM frequenciesMakes use of ISM frequencies• free for short range communicationfree for short range communication• high density of disturbing signalshigh density of disturbing signals

Cost/profit analysis to find the most Cost/profit analysis to find the most fitting solutionfitting solution

Selection of technologiesSelection of technologies

System Technology Optional FrequencyS1 FM Modulation 433 MHzS2 FHSS 900 MHzS3 DSSS 2,45 GHzS4 Bluetooth 2,45 GHzS5 DECT 1,9 GHz

Wireless technologies usedWireless technologies used

Wireless system S1 - Frequency Wireless system S1 - Frequency modulationmodulation• a lot of side bands createda lot of side bands created

if modulation index if modulation index • # side bands # side bands • S/N-ratio S/N-ratio


Wireless system S2 - FHSSWireless system S2 - FHSS• Frequency hopping spread spectrum (FHSS)Frequency hopping spread spectrum (FHSS)

this systems hops over a certain sequence of this systems hops over a certain sequence of different frequency channelsdifferent frequency channels

• Adaptive FHSSAdaptive FHSS detects affected channels and skips themdetects affected channels and skips them


Wireless system S3 - DSSSWireless system S3 - DSSS• Direct Sequence Spread Spectrum (DSSS)Direct Sequence Spread Spectrum (DSSS)• Every information bit is modulated using the Every information bit is modulated using the

same pseudo random bit code.same pseudo random bit code.• The energy is spread over a wider frequency The energy is spread over a wider frequency

spectrumspectrum• Per frequency, signal levels are lower, this Per frequency, signal levels are lower, this

means less interference to other systems and means less interference to other systems and higher security against intrudershigher security against intruders


Wireless system S4 - BluetoothWireless system S4 - Bluetooth• uses FHSSuses FHSS• includes coding schemes (CRC, FEC, …)includes coding schemes (CRC, FEC, …)• P2P as well as piconet configurationsP2P as well as piconet configurations


Wireless system S5 - DECTWireless system S5 - DECT• Digital Enhanced Cordless Communication Digital Enhanced Cordless Communication

(DECT)(DECT)• uses Time Division Multiple Access (TDMA)uses Time Division Multiple Access (TDMA)

every user gets certain timeslots allocated every user gets certain timeslots allocated many users possible at the same timemany users possible at the same time

Overview of the technical specs Overview of the technical specs of the wireless systemof the wireless system

Performance of wireless systemsPerformance of wireless systems

Quantified by the bit error rate Quantified by the bit error rate (BER)=(#errorbits) / (total # of bits)(BER)=(#errorbits) / (total # of bits) e.g. e.g.

• Sent: Sent: 0110 00010110 0001• Received: Received: 000010 0010 001111• BER=2/8=25%BER=2/8=25%

Possible disturbance effectsPossible disturbance effects

Mechanical disturbancesMechanical disturbances• VibrationVibration• Low & high speed movementLow & high speed movement• temperaturetemperature• ……

Electrical disturbancesElectrical disturbances

Mechanical disturbancesMechanical disturbances

Influence depends on the quality of the Influence depends on the quality of the hardwarehardware

this info should be supplied by the this info should be supplied by the manufacturermanufacturer

Not dealt with in this paperNot dealt with in this paper


Power reduction at the receiving antennaPower reduction at the receiving antenna• reflectionsreflections• path losspath loss• multipath fadingmultipath fading• antenna efficiencyantenna efficiency• obstructions in the propagation wayobstructions in the propagation way

Interference signalsInterference signals


Path lossPath loss• reduction of power due to increasing distance reduction of power due to increasing distance

between the RX and TXbetween the RX and TX• path loss can be increased by introducing path loss can be increased by introducing

obstructions in the propagation wayobstructions in the propagation way

• The reduced power at the receiver will increase The reduced power at the receiver will increase the likelihood of disturbances in the the likelihood of disturbances in the communicationcommunication


Multipath fadingMultipath fading• arises when reflected waves that are out of arises when reflected waves that are out of

phase interfere with direct wavesphase interfere with direct waves• caused by direct waves hitting conducting caused by direct waves hitting conducting

objects and in this way generating reflected objects and in this way generating reflected waveswaves

Test setup for multipath fadingTest setup for multipath fading

Results of measuring multipath Results of measuring multipath fadingfading

RPR= received power reduction = PRPR= received power reduction = PRXRX/P/PTXTX

RPR is 10dB less in hall than in open area, RPR is 10dB less in hall than in open area, although there are reflecting wallsalthough there are reflecting walls


InterferenceInterference• caused by other wireless systemscaused by other wireless systems

solution: co-existence plan in some protocolssolution: co-existence plan in some protocols

• caused by nearby machinerycaused by nearby machinery hard to predicthard to predict typically 170dBµV/m in the [10kHz, 500MHz] rangetypically 170dBµV/m in the [10kHz, 500MHz] range decreases with increasing frequencydecreases with increasing frequency


Interference caused by nearby machineryInterference caused by nearby machinery• measurements are made in the near field, measurements are made in the near field,

because: because: in practice communication devices are in close in practice communication devices are in close

proximity to the machineryproximity to the machinery in the far field, emissions are limited by the EMC in the far field, emissions are limited by the EMC

directive & emission standardsdirective & emission standards

• simulated by adding an interference antenna simulated by adding an interference antenna

Measuring interference of nearby Measuring interference of nearby machinerymachinery

Measuring in near field using sniffer E- & Measuring in near field using sniffer E- & H- field probesH- field probes

Measurement results show the envelope of Measurement results show the envelope of the maximum measured field strengths on the maximum measured field strengths on different components of the machinerydifferent components of the machinery

Measuring interference of nearby Measuring interference of nearby machinery: welding machinemachinery: welding machine

Measured EM environment welding machine

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Electric Field Magnetic Field

Measuring interference of nearby Measuring interference of nearby machinery: frequency convertermachinery: frequency converter

Measured EM environment frequency converter

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Measuring interference of nearby Measuring interference of nearby machinery: computermachinery: computer

Measured EM environment computer

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Measuring interference of nearby Measuring interference of nearby machinery: weaving machinemachinery: weaving machine

Measured EM environment weaving machine

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Measuring interference of nearby Measuring interference of nearby machinery: electrical motormachinery: electrical motor

Measured EM environment electrical motor

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Measuring interference of nearby Measuring interference of nearby machinery: CNC centremachinery: CNC centre

Measured EM environment CNC center

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Summary of measurements on Summary of measurements on interference of nearby machineryinterference of nearby machinery

Simulation of the disturbances Simulation of the disturbances using a generic simulatorusing a generic simulator

The communication devices are connected The communication devices are connected to the PC’s through an RS232-connectionto the PC’s through an RS232-connection

Implementation of disturbance Implementation of disturbance effects on the simulatoreffects on the simulator

Mechanical disturbancesMechanical disturbances• vibrations vibrations vibrating table vibrating table

Electrical disturbancesElectrical disturbances• interference interference interference antenna interference antenna• path loss path loss introducing a metal plate between introducing a metal plate between

RX and TXRX and TX• multipath fading multipath fading adding metal plates behind adding metal plates behind

and next to the RXand next to the RX• ambient noise levels ambient noise levels adding an interference adding an interference

antennaantenna


Mechanical disturbancesMechanical disturbances• vibrations vibrations vibrating table vibrating table

Generic simulatorGeneric simulator

1 vibration table1 vibration table 2 transmitter TX2 transmitter TX 3 interference 3 interference

antennaantenna 4 metal obstruction4 metal obstruction 5 metal plates for 5 metal plates for

reflectionreflection 6 receiver RX6 receiver RX 7 moving table7 moving table


Electrical disturbancesElectrical disturbances• interference interference interference antenna interference antenna


Electrical disturbancesElectrical disturbances• path loss path loss introducing a metal plate between introducing a metal plate between

RX and TXRX and TX


Electrical disturbancesElectrical disturbances• multipath fading multipath fading adding metal plates behind adding metal plates behind

and next to the RXand next to the RX

MeasurementsMeasurements

Measurement on the generic simulatorMeasurement on the generic simulator In situ measurementsIn situ measurements

• influence of long distance on path lossinfluence of long distance on path loss• changing mutual height of RX and TXchanging mutual height of RX and TX• obstructions in the propagation wayobstructions in the propagation way

Measurements on the generic Measurements on the generic simulatorsimulator

Radiated interference + multipath fadingRadiated interference + multipath fading• interference antenna generates signal + interference antenna generates signal +

reflection plates addedreflection plates added


Multipath fading + path lossMultipath fading + path loss• TX & RX enclosed in metal boxes, consisting of TX & RX enclosed in metal boxes, consisting of

single platessingle plates


Multipath fading + linear movementMultipath fading + linear movement


VibrationsVibrations


Vibrations, multipath fading, linear Vibrations, multipath fading, linear movement and radiated interferencemovement and radiated interference

Summary of the test results (1)Summary of the test results (1)

Only S1 (FM) showed degradation under Only S1 (FM) showed degradation under several conditions. These maybe due to several conditions. These maybe due to limitations of the PCB.limitations of the PCB.

Performance of a certain technology Performance of a certain technology depends on the TX-power and the RX-depends on the TX-power and the RX-sensitivitysensitivity• Bluetooth and DECT have best performanceBluetooth and DECT have best performance

Summary of the test results (2)Summary of the test results (2)

Propagation delay timePropagation delay time• =timeRX-timeTX=timeRX-timeTX• =radio propagation delay + processing delay=radio propagation delay + processing delay• Sometime technologies use an automatic Sometime technologies use an automatic

repeat, so delay time becomes unpredictablerepeat, so delay time becomes unpredictable

ConclusionsConclusions

Simulation of an industrial environment Simulation of an industrial environment describeddescribed

Different disturbances discussedDifferent disturbances discussed Design of a generic measuring setupDesign of a generic measuring setup Technologies with a lot of encoding (DECT, Technologies with a lot of encoding (DECT,

Bluetooth) provide more reliable Bluetooth) provide more reliable communication channelscommunication channels

Simulation of an Industrial Environment and overview of test results J. CATRYSSE; KHBO J. Rayée, D....

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