This document discusses electromagnetic positioning sensors and their design factors. It describes how electromagnetic positioning works using principles from Maxwell's equations and how factors like frequency, range, radiation pattern, and positioning methods are important in the design of these sensors. It also covers advantages and challenges of electromagnetic positioning as well as relevant legislation.

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CONFIDENTIAL Template Innovation Day 2017CONFIDENTIAL
Sensors for electromagnetic positioning
Guus Colman
Consultant Embedded Systems
guus.colman@verhaert.com
TRACK 1 - TRANSFORMATIONAL TECHNOLOGIES

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CONTENT
Positioning systems as key to transformation
Electromagnetic positioning
Important design factors
• Frequency
• Range
• Radiation pattern
• Position defining properties
• Positioning methods
• Robustness
• Legislation

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POSITIONING AS KEY TO INDUSTRY TRANSFORMATION
GPS navigation
1995: Fully operational
Surgery robotics
May 2006: First unassisted
robotic surgery
Instrument landing
system
Tempelhof Central Airport, Berlin,
1932 First operational system
Some ideas change applications, others transform the world…

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REASONS FOR KEEPING POSITION INFORMATION
To increase handling accuracy1
In safety critical systems: to change legislation2
To obtain user information3
A feedback loop leads to automation4
Building block in sensor fusion5

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THE POSITION DATA (R)EVOLUTION
Why is position data only now used on large scale?
• Localization principles are old
e.g. Maxwell’s equations: 1873
• New sensors based on old principles:
• Smaller sensors
• Higher frequency
• But no drastic changes
• Data processing power is rising fast
• Enormous increase in processor operations
• Advanced algorithms to get the most out of our data

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THE POSITION DATA (R)EVOLUTION
Manual car parking
Car parking aid system
Adaptive cruise control
(Supervised) self-driving cars
Traffic control
The technology is there, now is the time to act!
Sensors
Communication

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OVERVIEW OF LOCALIZATION TECHNIQUES
Electromagnetic
Acoustic - Ultrasound
Optical – Visual
Inertial measurement systems
Mechanical
Mainly used technique

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THE ELECTROMAGNETIC SPECTRUM
Electromagnetic positioning

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ELECTROMAGNETIC FIELDS
Voltage
Current
Electric field
Magnetic field
Electromagnetic field
Near antenna Far from antenna

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ELECTROMAGNETIC FIELDS
Voltage
Current
Electric field
Magnetic field
Electromagnetic field
Near antenna Far from antenna

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SENSORS FOR ELECTROMAGNETIC POSITIONING

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Advantages
• One (principle) fits all
• Scalable technology
• Well known
• Robustness
• Low power vs. Range
• High accuracy
• High speed signals
EM-POSITIONING: ADVANTAGES / DRAWBACKS
Drawbacks
• Densely used spectrum
• EMC tests/legislation
• High speed signals

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EM-POSITIONING SYSTEM: IMPORTANT DESIGN FACTORS
Electromagnetic
positioning
system
Legislation
Robustness
Positioning
method
Frequency
Antenna
radiation
pattern
Position
defining
property
Range

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MEASUREMENT FREQUENCY: SPECTRUM ALLOCATION
Heavily regulated:
• Look for ISM (industrial, scientific, medical)-frequency bands
• Region dependent (e.g. CE (EU) – FCC (US))

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DC
MEASUREMENT FREQUENCY: COMPARISON
(Electro)magnet:
Very small range (cm-range), unless a very big magnet is used (earth)
Low frequency (< 1 MHz)
• Curbed field propagation (also curbed
in atmosphere: localization errors)
• High power for large range
• Large antenna structures
• Less influenced by metal structures
High frequency (> 1 GHz)
• Straight field propagation
(line-of-sight required)
• Low power for large range
• Small antenna structures
• Multipath effects, water damping (2,4 GHz)

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MEASUREMENT RANGE
Low frequency:
More robust against external influences
Higher frequency:
Smaller near field region  higher range
Receivedsignalstrength
Distance from transmitter
NEAR FIELD
10λ0.1λ
FAR FIELD
20 dB / 10x distance
40-60 dB / 10x
distance
Magnetic field Electromagnetic wave
λ = wavelength

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MEASUREMENT RANGE
10 MW – 1 MHz : Russian Duga Radar 5W - 8 GHz: Mars communication

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IN WHICH WAY DOES AN ANTENNA RADIATE?
Omnidirectional antenna
• Small antenna
• Dipole antenna
• …
The radiation pattern shows the ratio of the power density at which
an antenna radiates in the far field in all angles
Each small antenna is omnidirectional
Directive antennas
• Yagi-Uda
• Log periodic
• Satellite dish
• …
Large antennas can be directional
Many antenna shapes exist

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IN WHICH WAY DOES AN ANTENNA RADIATE?
Near field coil radiation pattern Phased antenna array
0.000E+00
5.000E-04
1.000E-03
1.500E-03
2.000E-03
2.500E-03
0.000E+00 5.000E-04 1.000E-03 1.500E-03 2.000E-03 2.500E-03
Amplitude90°(V)
Amplitude 0° (V)
The radiation pattern shows the ratio of the power density at which
an antenna radiates in the far field in all angles

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Presence detection
• Inductance change
• Mutual coupling change
• Resistance change
• Capacitance change
POSITION DEFINING PROPERTIES
Positioning
• Incoming field amplitude
• Angle of arrival
• Time of flight
• Doppler: frequency offset
Which signal property can be used for position definition?

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1. Presence detection system
2. Reflection based system
3. Triangulation
POSITIONING METHODS
Which system can be used for position definition?

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1. Presence detection system
• Mainly based on property changes
POSITIONING METHODS
Mutual coupling sensor
Transmitter coil
Receiver coil
Transmitter coil
Receiver coil
Without rotor blade With rotor blade
Receiver coil sees a different amount of magnetic field

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2. Reflection based system
• EM-waves reflect at medium changes
• Conductivity or ε, µ-changes
• Same principle can be used acoustic and optical
Time domain reflectometry:
Locate electrical faults in cables
• Can be used for maintenance of telecom wires,
gas/oil/dredge pipes, security (fences),…
• EM-reflection systems are blind the first meters
POSITIONING METHODS
Radar
30 m

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3. Triangulation
• If you know the distance, the angle, or the path to a
reference system, it is possible to calculate the location
Medical drill positioning system
POSITIONING METHODS

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What to do in case of disturbances?
• Make a list of probable disturbances in this application
• Frequency bands
• Materials, shapes,…
• Simulate the effect of these disturbances
• Change the system until robustness is ok
• Change position
• Change frequency
• Create redundancy: more transmitters/receivers
• Change modulation: narrowband vs. UWB
• Change your positioning method or principle
POSITIONING METHODS: ROBUSTNESS

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Both are needed during development
• Measurements:
• Realistic if correctly executed
• Are expensive and take time to execute
• Provide global results (only where sensors are put)
• Simulations:
• To compare solutions
• Oversimplified
• Mainly takes computation time: more experiments in given time
• Provide detailed insights
Make a simulation model, and verify your simulation
model and results with experiments
MEASUREMENTS VS. SIMULATIONS

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Transmitting EM-measurement devices need to comply with:
• Low voltage directive
• Product safety
• EMC directive: Measurement frequency range depends on:
• Highest generated frequency
• Intentionality of the transmitter
• Radio equipment directive (RED, previously R&TTE):
• In-band regulation
• Out-of-band regulation
• Use pre-certified modules in case of low volumes
• 20-30k per test campaign + RF design costs (designers + equipment)
• Break-even point needs to be estimated
LEGISLATION

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Positioning can be the key to industry transformation
Electromagnetic positioning is a very good candidate
CONCLUSIONS
The technology is ready, so act now!

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QUESTIONS

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