Addressing the challenges of position sensor solutions in safety critical automotive applications

Copyright 2017, IDT Inc.

Technical Education Webinar Series, January 25, 2017

Presented by Jan Leuckfeld and Heinz Oyrer

Addressing the Challenges of Position Sensor Solutions in Safety Critical Automotive Applications

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http://www.idt.com/application/automotive

http://www.idt.com/application/mobile-personal-electronics

http://www.idt.com/application/high-performance-computing


Abstract

This talk will discuss position sensor challenges such as the issue of stray fields, harsh environments, installation space, mechanical tolerances, as well as levels of accuracy performance for safety critical applications such as electronic power steering (EPS) and electrical motor control to meet new safety and efficiency regulations.

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Introduction to Automotive Electronics

• Sensing is a major function of the electronics system with position sensors as on of the biggest market

segment in regards to automotive sensor demand.

• Position sensors in vehicles are increasingly installed for applications such as throttle valve position, suspension control, power

assisted steering, electronic gas pedals, electronic brake pedals and fluid level systems.

• Systems are increasingly being electrically-powered In addition to previously mechanically-driven

applications such as power steering.

• Increasing for brushless DC motors stimulating the demand for motor position and

control sensors in the automotive sector.

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What does Safety-critical mean?

• Safety-critical or Life-critical system

is a system whose failure or malfunction may result in one (or more) of the following outcomes:

– Death or serious injury to people

– Severe damage to equipment/property and environmental harm

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ISO 26262 - titled "Road vehicles – Functional safety”

• The standard ISO 26262 is an adaptation of the Functional Safety standard IEC 61508 for Automotive Electric/Electronic Systems.

• Functional safety features form an integral part of each automotive product development phase

• ISO 26262 defines functional safety for automotive equipment applicable throughout the lifecycle of all automotive electronic and electrical safety-related systems.

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Model-based Functional Safety in E/E system development

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• ISO 26262 - increased awareness of this topic in the industry.

• Challenge of fulfilling the requirements of the standard and addressing the rising complexity of safety-related functions.

• It takes much greater work effort to develop safety-critical compared to conventional systems

• Development, analysis and test methods need to be integrated in a uniform process.

Source: Vector Consulting Services (Model-based Functional Safety in E/E system development)




https://vector.com/portal/medien/cmc/press/Vector/Safety_AutomobilElektronik_201204_PressArticle_EN.pdf




Safety-critical applications in Automotive

• Modern cars are stuffed full of microprocessors and microcontrollers that perform a variety of functions, which vary in their importance from convenience to safety critical.

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Source: www.nexteer.com product images

• Systems in cars may be broadly divided into 3 categories, depending on their safety requirements:

1. Convenience systems, which add to the comfort and pleasure of using the vehicle, but are only an inconvenience if they malfunction; an example is climate control.

2. Non-critical safety systems, which add to the safety of the vehicle, but do not render the vehicle unsafe if switched off, but may introduce problems if they malfunction; an example is an electronic stability program (ESP).

3. Critical systems, the correct functioning of which is essential to the safe operation of the vehicle; the braking and the steering system is a good example.

.




http://www.nexteer.com/


Improved fuel efficiency & emissions in vehicles

• Europe CAFE standards require OEM’s to raise average fuel efficiency to 60.6 mpg ≈ 26 km/l for new vehicles by 2025.

– Translates in CO2 emission reductions to 70 g/km by 2025.

• U.S. CAFE standards require OEMs to raise average fuel efficiency to 56.2 mpg ≈ 24 km/l for new vehicles by 2025

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Source: Center for Climate and Energy Solutions

CAFE = Corporate Average Fuel Economy





Selected Automotive Applications

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Powertrain • Air intake manifold

• Throttle valve

• Turbocharger wastegate

• Turbocharger bypass valve

• Exhaust gas recirculation

• Transfer case gear position

• Transmission gear position

• Gear shift lever position

• Double clutch actuator

• Transmission actuator

• Engine cooling fan

• Hybrid E- Generator

• Fluid level sensors

• Crankshaft

• Camshaft

Chassis • Steering motor

• Steering column position

• Suspension height

• Headlamp leveling

• Power seat position

• Electric park brake

• Fuel level sensor

• Convertible roof position

Safety • Auto Brake actuator

• Steering Angle & Torque

Body • HVAC pump motor

• Airflow actuators position

• Wiper position & motor

• Mirror Position

• Seat position

• Accelerator pedal

• Clutch pedal, e-clutch

• Brake pedal





What are Position Sensors?

• Contacting: through a mechanical connection (switch)

• Non-contacting: without physical contact

Sensors which measure linear or rotational motion

• More reliable

• Longer functional life due to the absence of mechanical parts and physical contact

Non-contacting position sensors are

• From simple angle sensors towards robust and intelligent sensor systems

• Contact-less AND magnet-less position sensor solutions

Strong trend

• Non-contacting, magnet-less, intelligent position sensors!

IDT Position Sensors

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Focus on Inductive Technology

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Metallic target

(Al, Cu,..)

Simple coil

design

on 2-sided

PCB

• Ultra-thin solution - Small form factor, no magnet required

• Total stray field immunity - ISO 11452-8 compliant

• No external sensor needed - the sensor is a PCB coil

• Compliant to auto standards - AECQ-100, ESD, EMC, ISO26262

• Suitable for high temperature

• On and off-axis capability and alignment

Chip




https://www.youtube.com/watch?v=VMDeVNSlHNU&feature=youtu.be


Typical Inductive Position Applications

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linear motionend of shaft

360°

on- axis

rotation

end of shaft

180°

on- axis

rotation

hollow shaft 360°

off-axis rotation

arc motion

2D (XY) motion

Torque

Side shaft, 1x 360°

off- axis rotation

res.: 0.088° / step

Side shaft, 2x 180°

off- axis rotation

res.: 0,044°/step

End of shaft 1x 360°

on- axis rotation

res.: 0.088° / step

Side shaft, 6x 60°

off- axis rotation

res.: 0,015°/step

arc coil shape for

limited space





Identifying and solving the challenges (1)

• ISO11452-8 compliant!

Stray field immunity

• No temperature limitations

Harsh environments • Thinnest

position sensor on the market!

Installation space

• No tight assembly tolerances required!

Mechanical tolerances • No magnet

required!

Sensing target

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• High accuracy in every application!

Accuracy

• Same IC for on-axis + off-axis!

Off-axis capability

• Fully automotive qualified!

EMC and overvoltage protection

• Suitable for any number of rotor poles!

Motor position and commutation

• Thinnest torque sensor available!

Torque Sensing

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• Maximum resolution at every angle range!

Narrow angle

• Full resolution for long or short linear strokes!

Long strokes • 2D motion

with only one IC!

2D Sensing

• Flexible motion paths!

Arc Motion and Non-uniform

Sensing • ISO11452-8 compliant!

Stray field immunity

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Sensors and strayfields

• Sensors – Use of sensors has dramatically increased – Number and strengths of electric fields have increased – Exposure to environmental factors such as magnetic stray fields,

vibration and misalignment cause issues with system safety and reliability

• What is a stray field? – Magnetic fields are generated by magnets, motors, transformers or any

current-carrying conductors – Stray Fields are parasitic magnetic fields as observed by a sensor

• Why stray fields in automotive – Increased electrification of automobiles – Electric cars - large high current carrying wires run between the front and

back of the vehicle

• Issues caused by stray fields – High levels of electro-magnetic interference (EMI) are a strong concern

in industrial and automotive applications

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Examples of strayfields

• Electric motor – Generates a magnetic field that effect e.g. the angle position

sensor accuracy

• Drive-train of vehicles becomes partially or wholly electrified

– Battery cable connections can be negatively impacted e.g. the position sensor in an acceleration pedal or an electronic power steering system

– Stray magnetic field from a high-voltage power line in an EV or HEV is easily large enough to affect safety-critical systems such as the brake pedal

• Huge induction fields – such as in future charging stations of electric vehicles

– Can result in an adverse impact on all on-board sensors in a car

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Inductive – solving the strayfield problem

• Adherence to Standards – Naturally, these unique inductive position sensors meet

the latest standards for immunity to magnetic fields and functional safety

• ISO11452-8 - immunity to magnetic fields • ISO26262 - functional safety

– Inductive = Stray field immunity. This enables a small form factor and it allows for a cost effective solution as external components and expensive external shielding are not needed - in short:

• Simple • Inexpensive • Small form factor • Safer usage • Unlimited protection from stray fields

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Position Sensors Ubiquitous in EPS Systems (safety-critical)

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• Enable Auto OEMs to meet improved steering safety and fuel efficiency requirements

• Hand-wheel position for ESP and adaptive light control as well turns-counting

• Torque sensing to control the steering power support for the driver

• Rotor position for motor commutation, particularly in BLDC motors for power steering assistance

Torque Sensor

Steering Angle Sensor

Steering Torque Sensor

Rotor position Sensor

Source: Nexteer





Opportunities for efficiency - Electrical motors

• Electric motors use majority of global electricity – Electric motors are the single biggest consumer of electricity.

– They account for about 2/3 of industrial power consumption and, about 45% of global power consumption, according to a new analysis by the International Energy Agency

• Majority of electric motors are inefficient – Rarely discussed is the fact that the majority of electric motors are inefficient,

oversized, or running when they don’t need to be running.

• Addressing the efficiency of electric motors is an important topic that needs to be tackled.

– Reducing CO2-emissions by saving weight and reducing fuel consumption as a key requirements in Automotive market

– Brushless Direct Current (BLDC) motors are rapidly gaining popularity. Major advantages of brushless DC motors include higher efficiency at converting electricity into mechanical power, reduced noise, longer lifetime and higher reliability

– Government regulations worldwide: Require the industry to implement new efficiency classes IE1, IE2, IE3, … (IE = International Efficiency to reduce CO2 (higher efficiency means better motor control)

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Source: CleanTechnica, abb.com/energyefficiency





Motor Position Sensor IC - enables efficient EPS motor commutation

• Controls commutation of a brushless DC motor employed in the system

• Eliminates need for discrete hall sensors in stator

• More design freedom - the sensor does not need to reside on specific positions inside the motor

• Provides fast and accurate measurements

• Power efficient - no power dissipation

• Easy integration, high temperature environment

• High start-up torque, low torque ripple

• Low audible noise, excellent reliability

• High safety levels, high accuracy

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Source: press picture Brose Fahrzeugteile

Brushless DC (BLDC)

Motor is preferred

choice in EPS as it

offers better starting

torque and efficiency




Copyright 2017, IDT Inc. 22

How EPS Technology is Paving the Way for ADAS

• EPS is the gateway technology to autonomous driving of the future.

• EPS technology is enabling the future of “intuitive motion control” with its advanced mechatronic hardware/ electronics, software and sensor building blocks.

• Safety-critical components play a key role in “Advanced Driver Assistance Systems” – or ADAS

Source: Hitachi IR Day 2015

Position Sensor Controls

commutation of a

brushless DC motor

employed in the system





Wrap up

• Sensing is a major function of the electronics system in automotive.

• Position sensors as one of the biggest market segment in regards to automotive sensor demand.

• Position sensors provide system power and cost savings while improving vehicle performance and safety.

• Inductive Position Sensor technology will continue to experience strong adoption in EPS/ADAS and other automotive safety critical and fuel efficiency applications.

• Inductive Position Sensor ICs offer many benefits over other sensing technologies.

• Superior robustness through contactless, magnet-less, intelligent “system-on-chip” solution.

• Stray field immune technology provide high accuracy measurements even in the noisiest of electromagnetic interference (EMI) environments, commonly found in automotive applications.

• New emission regulations and safety standards are key business drivers.

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Thank You Analog Mixed Signal Product

Leadership in Growth Markets

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Date post:	03-Mar-2017
Category:	Automotive
Upload:	heinz-oyrer
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