the fundamentals of vehicle data...

© HORIBA MIRA Ltd. 2016


The fundamentals of vehicle data collection:

Instrumentation set-up

& checks

David Wood

Project Braking Engineer

19th April 2016


Contents/Summary

■ Brake engineering overview at HORIBA MIRA

■ Part 1: Selection of instrumentation:

- Understanding the testing requirements, identifying what you want to measure, understanding

the conditions and practicalities of the measurement, selecting the appropriate instrumentation

■ Part 2: Installation of instrumentation

- Taking a piece of instrumentation and correctly installing to ensure you measure as intended

■ Part 3: Installed instrumentation checks:

- Transducer checks to validate measurement, Polarities/Vehicle co-ordinate checking

■ Part 4: Vehicle shakedown

19th April 2016 2The fundamentals of vehicle data collection: Instrumentation set-up & checks


Brake engineering overview at HORIBA MIRA

Types of project work undertaken

Benchmarking and target setting

Refinement (noise/judder) test and development

Prototype brake system design and build

Production quality issue identification/resolution

Brake sizing/material investigations

ECE Regulation 13/13h legislative testing

(foundation brake performance testing)

FMVSS and other global legislation

Research projects (internal/external)



Brake test equipment and facilities

Capabilities/Equipment:

■ Full vehicle brake

performance evaluation

instrumentation

■ Full NVH development

instrumentation

■ Brake pedal feel

characterisation

instrumentation

■ Disc Thickness Variation

(DTV) and Pad wear

measurements

■ Pantone colour/brake dust

measurements

■ ABS and circuit failure

valves (legislative tests)

■ Braking Robot

Facilities:

■ UK based Road and Track ■ Climatic tests on road and

track (Almeria, Spain)

■ NVH & Performance

Dynamometer (Germany)



Contents/Summary:

Part 1: Selection of instrumentation












Understanding the testing requirements

■ Why are we testing/Who are we testing for?

- Legislation - defined

- Development – suggested/defined by procedure

- Validation – as defined by simulation

- Investigation - undefined

■ The above will determine the minimum requirements of our instrumentation

requirements



Considerations/Practicalities of testing

■ Given a requirement to take a measurement, how can/should we measure this?

- Are we told from our procedure?

- Can we measure the item directly in this application?

- Can/Should/Must we Calculate from something we can measure?

■ Which instrument will measure this most appropriately for the intended test?

- Example: We want to measure Vehicle Speed:

o GPS – position, heading and speed information

o 5th Wheel – speed and forward/reverse only

o Wheel speed encoders – speed and direction of that wheel i.e. depends on number fitted



Transducer Specification/Limitations

8

■ IP Rating - Environmental considerations

(temperature, dust, water)

■ Durable or consumable?

■ Proprietary or “home-made”?

The fundamentals of vehicle data collection: Instrumentation set-up & checks 19th April 2016


Instrumentation Considerations

Which thermocouple to use to measure brake disc temperature?

- Higher Temperature, Transient tests and the case of slotted/drilled discs means use of shoe

type thermocouple

- Robust versions available for environmental tests

- Button thermocouples for more general applications – slower response due to thermal mass

- Thermocouples can contaminate NVH data – usually circa 1kHz

- Desirable to use IR thrermocouples but emissivity & environment issues prevent use

9The fundamentals of vehicle data collection: Instrumentation set-up & checks 19th April 2016


Understand the Test - High Energy Input Test Example

Typical high speed fade test in time domain

- WOT acceleration to >0.5g deceleration

- Repeated transients

- Can reach >90% of Vehicle Vmax

- High brake temperatures reached

- Brake pedal travel increases demonstrate fade

- (baseline dashed, pedal travel shown in blue)

1019th April 2016The fundamentals of vehicle data collection: Instrumentation set-up & checks


Contents/Summary:

Part 2: Installation of instrumentation












Typical brake instrumentation installed

Some of the most common parameters measured

for brake testing are:

- Pedal travel

- Linear potentiometer and angular

potentiometer to pedal pad

- String potentiometer to pedal

- Pedal effort

- Load cell mounted centrally to pedal



Some of the most common parameters measured

for brake testing are:

- Vehicle deceleration

- Accelerometer mounted close to Centre of

Gravity height (seat rail)

- Alternative mechanical versions are still

sometimes used




Some of the most common parameters

measured for brake testing are:

- Brake temperature

- Disc rubbing thermocouple (Button or

sliding shoe style)

- Disc embedded thermocouple

- Pad embedded thermocouple

- Brake caliper fluid thermocouple

- Ambient temperature





Some of the most common parameters

measured for brake testing are:

- Brake fluid pressure

- Brake line upstream of caliper (front / rear)

- Brake caliper (bleed nipple)

- Brake master cylinder

- Brake failure valves primary / secondary

- Brake booster vacuum pressure




Some of the most common parameters measured for brake testing are:

- Speed / Stopping Distance

- GPS

- Wheel speed encoders (ABS testing)

- High sample rate data acquisition (particularly for NVH)



Specialised brake instrumentation

Other (more specialized) brake sensors:

- NVH measurements:

- Drivers ear microphone

- Caliper vibration (uni-accelerometer)

- Driver subjective rating

- Steering wheel nibble / judder

- Seat vibration

- Brake torque

- Torque wheels/Strain gauged brake calipers



Disc Thickness Variation (DTV) Measurement Example

20

Judder/Off-Brake wear investigations:

- 6 point non-contact Disc Thickness

Variation (DTV) measurements:

- Runouts measured at inner &

outer faces with respect to disc

position in degrees

- DTV calculated from paired run-

out measurements

- DTV usually worst at rim (furthest

from hub)



Disc Thickness Variation (DTV) Measurement Example

21

-50

0

50

Ru

no

ut/

DT

V [

mic

ron

s]

0 60 120 180 240 300 360

Rotation [degrees]

RO Inner-Rim

RO Inner-Centre

RO Inner-Hub

RO Outer-Rim

RO Outer-Centre

RO Outer-Hub

DTV Rim

DTV Centre

DTV Hub

VN14 EPV

RO Rim DTV Rim

RO Centre DTV Centre

RO Hub DTV Hub

Inner Outer Inner Outer Inner Outer

25 26 2 19 19 1 16 15 2



Contents/Summary:

Part 3: Installed instrumentation checks












Transducer Checks



Transducer Calibration


Inboard

(instrumented)

displacement

transducer –

”wheel-to-body”

Outboard

(calibration)

displacement

transducer –

actual wheel-

to-body


Transducer Calibration



Instrumentation - Ranges

Data collection ranges – general examples a for high performance car

26

Channel Range

Vehicle Velocity 400 km/h

Longitudinal Deceleration +/- 2.5 g (+ve deceleration)

Brake Pressure +ve 200 bar

Booster Vacuum Pressure -ve 1 bar

Brake Pedal Travel +ve 200 mm (Varies)

Brake Pedal Force +ve 2 kN

Brake Disc Temperatures -30 to +950 ̊C



Vehicle Co-Ordinates/Polarity



Senses


- MIRA RLD standard sign conventions for positive sense are as follows:

- X - +ve rearwards

- Y - +ve left (whilst facing the front of the vehicle)

- Z – +ve upwards

- Moments – right hand screw (clockwise when looking away from the origin along the

axis)

- Strain – tension +ve

- Relative displacement, eg wheel-to-body – transducer extension +ve


Contents/Summary

Part 4: Vehicle shakedown












Vehicle Shakedown


- First opportunity to test the fully installed setup

- Are dynamic checks suitable for the specific test?

- Should collect data during shakedown

- Obtains a record for reference later in the test

- Allows data to be put through the analysis process

- Allow for heat soak to test for drift

- Allow instrumentation to see the environment they will be exposed to during testing

- Check vehicle runs correctly, any test ballast secured and doesn’t effect instrumentation

etc.


Dynamic Checks


Dynamic checks at steady states:

- Ramp to ground

- Acceleration & brake

- Clockwise and Counter clockwise turn

- Speed bump


Contact Details

19th April 2016 32

HORIBA MIRA Ltd.

Watling Street,

Nuneaton, Warwickshire,

CV10 0TU, UK

T: +44 (0)24 7635 5000

F: +44 (0)24 7635 8000

www.horiba-mira.com

David WoodMEng

Braking Project Engineer

Direct T: +44 (0)24 7635 5394

E: [email protected]

The fundamentals of vehicle data collection: Instrumentation set-up & checks

the fundamentals of vehicle data...

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