MTS SWIFT 20 User Manual

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SWIFT® 20 (Ultra) Sensor
Product Information

Spinning Wheel Integrated Force Transducer
For Small or High Performance Vehicles

100-037-800 L

Copyright information © 1999–2011 MTS Systems Corporation. All rights reserved.

Trademark information MTS, SWIFT, T estSt ar , and TestWare are registered trademarks of MTS Systems

Corporation within the United States. These trademarks may be protected in
other countries.

Microsoft, Windows, Wi ndows for Workgroups, Windows 95, and Windows NT
are registered trademarks of Microsoft Corporation. Apple and Macintosh are
registered trademarks of Apple Computer, Inc. UNIX is a registered trademark of
The Open Group. LabVIEW is a registered trademark of National Instruments
Corporation. All other trademarks or service marks are property of their
respective owners.

Publication information

Manual Part Number Publication Date

151956-00 B February 1999
100-037-800 A 12 June 2000
100-037-800 B 17 July 2000
100-037-800 C 9 May 2001
100-037-800 D December 2004
100-037-800 E February 2005
100-037-800 F April 2005
100-037-800 G May 2005
100-037-800 H October 2005

100-037-800 J January 2006
100-037-800 K November 2008
100-037-800 L December 2011

Contents

Technical Support 7

How to Get Technical Support 7
Before You Contact MTS 7
If You Contact MTS by Phone 9
Problem Submittal Form in MTS Manuals 10

Preface 11

Before You Begin 11

Conventions 12

Documentation Conventions 12

Hardware Overview 15

Spinning Applications (Test Track) 16

Non-spinning Applications (Simulation Lab) 17

Construction 18

Design Features 22

Coordinate System 23

Specifications 25

Calibration 29

Low-Profile Transducer Interface 31

Low-Profile TI Front Panel 34

Low-Profile TI Rear Panel 41

Induction Power Source 42

Low-Profile TI Jumpers 43

Interfacing with RPC 44

Software Utilities 45

Introduction 46

TISTATUS - Low-Profile Transducer Interface Status 47

TIXFER - Low-Profile Transducer Interface Transfer 48

TISHUNT - Low-Profile Transducer Interface Shunt 51

Setting Up Shunt Calibration Reference Values 55

TISETZERO – Low-Profile Transducer Interface Set Zero Method 56

SWIFT 20 Sensors Contents

3

Error Messages 57

Shunt Error Status 58

Setting up the Low-Profile Transducer Interface 59

Select a Zero Method 60

Calibration File Elements 61

Upload the Calibration File 64

Edit the Calibration File 66

Download the Calibration File 70

Installing the Transducer 73

Transducers Designed to Operate with a Low-Profile TI but Using a Mini TI 73

Test Track Vehicle for Slip Ring Sensor 74

Attaching SWIFT Components to the Wheel Assembly 77

Attaching SWIFT and Wheel Assembly to the Vehicle 80

Installing the Low-Profile Transducer Interface Electronics 82

Setting up the SWIFT Sensor for Data Collection 85

Verifying the Quality of the Zero Procedure 95

Collecting Data 98

Road Simulator 100

Attaching SWIFT Components to the Fixturing 102

Zeroing the Low-Profile Transducer Interface 105

Communication Configurations 106

Cable Configurations 108

SWIFT TI to PC Host (9-pin) 108
SWIFT Low-Profile TI to PC Host (25-pin) 108
SWIFT Low-Profile TI to SWIFT Low-Profile TI 109
T ermination Jumper 110

Analyzing SWIFT Data 111

The Data 112

Fx Data (Longitudinal Force) 113

Fz Data (Vertical Force) 115

Mx Data (Overturning Moment) 116

My Data (Brake Moment) 119

Acceleration and Braking Events Example 120

Slalom Curve Driving Example 122

Contents

4

SWIFT 20 Sensors

Maintenance 123

Transducer 124

Low-Profile Transducer Interface 125

Cables 126

Troubleshooting 127

Assembly Drawings 141

Cable Drawings 142

SWIFT 20A Mechanical Parts 156

SWIFT 20T Mechanical Parts 163

Common Parts 170

SWIFT 20 Sensors Contents

5

6

Contents

SWIFT 20 Sensors

Technical Support

How to Get Technical Support

Start with your

manuals

Technical support

methods

MTS web site

www.mts.com

E-mail [e-mail]

Telephone MTS Call Center 800-328-2255

Fax [phone]

Technical support

outside the U.S.

The manuals supplied by MTS provide most of the information you need to use
and maintain your equipment. If your equipment includes MTS software, look
for online help and README files that contain additional product inform ation.

If you cannot find answers to your technical questions from these sources, you
can use the internet, e-mail, telephone, or fax to contact MTS for assistance.

MTS provides a full range of support services after your system is installed. If
you have any questions about a system or product, contact MTS in one of the
following ways.

The MTS web site gives you access to our technical support staff by means of a
Technical Support link:

www.mts.com > Contact MTS > Service & Technical Support

Weekdays 7:00 A.M. to 5:00 P.M., Central Time

Please include “Technical Support” in the subject line.

For technical support outside the United States, contact your local sales and
service office. For a list of worldwide sales and service locations and contact
information, use the Global MTS link at the MTS web site:

www.mts.com > Global MTS > (choose your region in the right-hand
column) > (choose the location closest to you)

Before You Contact MTS

MTS can help you more efficiently if you have the following information
available when you contact us for support.

Know your site

number and system

number

SWIFT 20 Sensors Technical Support

The site number contains your company number and identifies your equipment
type (material testing, simulation, and so forth). The number is usually written on
a label on your MTS equipment before the system leaves MTS. If you do not
have or do not know your MTS site number, contact your MTS sales engineer.

Example site number: 571167

When you have more than one MTS system, the system job number identifies
which system you are calling about. You can find your job number in the papers
sent to you when you ordered your system.

Example system number: US1.42460

7

Know information from

prior technical

If you have contacted MTS about this problem before, we can recall your file.
You will need to tell us the:

assistance

• MTS notification number

• Name of the person who helped you

Identify the problem Describe the problem you are experiencing and know the answers to the

following questions:

• How long and how often has the problem been occurring?

• Can you reproduce the problem?

• Were any hardware or software changes made to the system before the

problem started?

• What are the model numbers of the suspect equipment?

• What model controller are you using (if applicable)?

• What test configuration are you using?

Know relevant

computer information

Know relevant

software information

If you are experiencing a computer problem, have the following information
available:

• Manufacturer’s name and model number

• Operating software type and service patch information

• Amount of system memory

• Amount of free space on the hard drive in which the application resides

• Current status of hard-drive fragmentation

• Connection status to a corporate network

For software application problems, have the following information available:

• The software application’s name, version number, build number, and if

available, software patch number. This information is displayed briefly
when you launch the application, and can typically be found in the “About”
selection in the “Help” menu.

• It is also helpful if the names of other non-MTS applications that are

running on your computer, such as anti-virus software, screen savers,
keyboard enhancers, print spoolers, and so forth are known and available.

Technical Support

8

SWIFT 20 Sensors

If You Contact MTS by Phone

Your call will be registered by a Call Center agent if you are calling within the
United States or Canada. Before connecting you with a technical support
specialist, the agent will ask you for your site number, name, company , company
address, and the phone number where you can normally be reached.

If you are calling about an issue that has already been assigned a notification
number, please provide that number. You will be assigned a unique notification
number about any new issue.

Identify system type To assist the Call Center agent with connecting you to the most qualified

technical support specialist available, identify your system as one of the
following types:

• Electromechanical materials test system

• Hydromechanical materials test system

• Vehicle test system

• Vehicle component test system

• Aero test system

Be prepared to

troubleshoot

Write down relevant

information

After you call MTS logs and tracks all calls to ensure that you receive assistance and that action

Prepare yourself for troubleshooting while on the phone:

• Call from a telephone when you are close to the system so that you can try

implementing suggestions made over the phone.

• Have the original operating and application software media available.

• If you are not familiar with all aspects of the equipment operation, have an

experienced user nearby to assist you.

Prepare yourself in case we need to call you back:

• Remember to ask for the notification number.

• Record the name of the person who helped you.

• Write down any specific instructions to be followed, such as data recording

or performance monitoring.

is taken regarding your problem or request. If you have questions about the status
of your problem or have additional information to report, please contact MTS
again and provide your original notification number.

SWIFT 20 Sensors Technical Support

9

Problem Submittal Form in MTS Manuals

Use the Problem Submittal Form to communicate problems you are experiencing
with your MTS software, hardware, manuals, or service which have not been
resolved to your satisfaction through the technical support process. This form
includes check boxes that allow you to indicate the urgency of your problem and
your expectation of an acceptable response time. We guarantee a timely
response—your feedback is important to us.

The Problem Submittal Form can be accessed:

• In the back of many MTS manuals (postage paid form to be mailed to MTS)

• www.mts.com > Contact Us > Problem Submittal Form (electronic form to

be e-mailed to MTS)

Technical Support

10

SWIFT 20 Sensors

Preface

Before You Begin

Safety first! Before you attempt to use your MTS product or system, read and understand the

Safety manual and any other safety information provided with your system.
Improper installation, operation, or maintenance of MTS equipment in your test
facility can result in hazardous conditions that can cause severe personal injury or
death and damage to your equipment and specimen. Again, read and understand
the safety information provided with your system before you continue. It is very
important that you remain aware of hazards that apply to your system.

Other MTS manuals In addition to this manual, you may receive additional MTS manuals in paper or

electronic form.
If you have purchased a test system, it may include an MTS System

Documentation CD. This CD contains an electronic copy of the MTS manuals
that pertain to your test system, including hydraulic and mechanical component
manuals, assembly drawings and parts lists, and op eration and preventive
maintenance manuals. Controller and application software manuals are typically
included on the software CD distribution disc(s).

SWIFT 20 Sensors Preface

11

Conventions

DANGER

WARNING

CAUTION

Conventions

Documentation Conventions

The following paragraphs describe some of the conventions that are used in your
MTS manuals.

Hazard conventions As necessary, hazard notices may be embedded in this manual. These notices

contain safety information that is specific to the task to be performed. Hazard
notices immediately precede the step or procedure that may lead to an associated
hazard. Read all hazard notices carefully and follow the directions that are given.
Three different levels of hazard notices may appear in your manuals. Following
are examples of all three levels.

Note For general safety information, see the safety information provided with

your system.

Danger notices indicate the presence of a hazard with a high level of risk which,
if ignored, will result in death, severe personal injury, or substantial property
damage.

Warning notices indicate the presence of a hazard with a medium level of risk
which, if ignored, can result in death, severe personal injury, or substantial
property damage.

Caution notices indicate the presence of a hazard with a low level of risk which,
if ignored, could cause moderate or minor personal injury, equipment damage, or
endanger test integrity.

Notes Notes provide additional information about operating your system or highlight

easily overlooked items. For example:

Note Resources that are put back on the hardware lists show up at the end of

the list.

Special terms The first occurrence of special terms is shown in italics.

Illustrations Illustrations appear in this manual to clarify text. It is important for you to be

aware that these illustrations are examples only and do not necessarily represent
your actual system configuration, test application, or software.

Electronic manual

conventions

This manual is available as an electronic document in the Portable Document
File (PDF) format. It can be viewed on any computer that has Adobe Acrobat
Reader installed.

12

Preface

SWIFT 20 Sensors

Conventions

Hypertext links The electronic document has many hypertext links displayed in a blue font. All

blue words in the body text, along with all contents entries and index page
numbers, are hypertext links. When you click a hypertext link, the application
jumps to the corresponding topic.

SWIFT 20 Sensors Preface

13

Conventions

14

Preface

SWIFT 20 Sensors

Hardware Overview

Data

S20-25

Test Track

Laboratory Simulation

Important This manual includes information on the Low-Profile Transducer

Interface (TI). For SWIFT transducers designed to operate with the
newer Mini TI, there is a separate manual that documents the
Mini TI, (MTS part number 100214316). For example information in
this manual regarding shunt verification, zeroing procedures, or
software utilities will pertain to the Low-Profile TI. If you have the
Mini TI as a transducer interface, refer to its product manual for
related information.

Overview The MTS Spinning Wheel Integrated Force Transducer (SWIFT®) is a light-

weight, easy-to-use transducer that enables you to conduct faster, less expensive
data acquisition and road simulation testing.

The transducer is designed for use both on the test track and in the test laboratory.
It attaches to the test vehicle or an MTS Series 329 Road Simulator using an
adapter and a modified wheel rim.

You can achieve excellent data correlation using the same transducer and vehicle
on the test track and on a road simulator. It is available in various sizes and
materials to fit various vehicle and loading requirements.

SWIFT 20 Sensors Hardware Overview

Contents Spinning Applications (Test Track) 16

Non-spinning Applications (Simulation Lab) 17
Construction 18

Design Features 22
Coordinate System 23
Specifications 25
Calibration 29
Low-Profile Transducer Interface 31

Low-Profile TI Front Panel 34

Low-Profile TI Rear Panel 41

Low-Profile TI Jumpers 43
Interfacing with RPC 44

15

Spinning Applications (Test Track)

Spinning Applications (Test Track)

The SWIFT sensor can be used for road load data acquisition (RLDA)
applications:

• Durability

• Noise, Vibration and Harshness (NVH)

• Ride and Handling

• Tire Performance

The transducer is durable enough to withstand harsh road testing and data
acquisition environments. The transducer is splash resistant and suitable for use
in conditions where the test vehicle will encounter occasional standing or running
water, or will be exposed to precipitation. However, it should not be submerged.

In a typical spinning application, the transducer is mounted on a modified rim of
a tire on a test vehicle, as shown in the following figure. Data is transmitted from
the spinning wheel to the Transducer Interface (TI) electronics via a slip ring
mounted on the transducer.The TI, power supply, and data recorder can be
located inside the vehicle or in the trunk.

Transducer Signals

Customer Supplied

12 Vdc Power Supply

Spinning Application (Test Track)

Output

Signals

Customer Supplied

Data Recorder

Transducer Interface

(TI)

S20-26

Hardware Overview

16

SWIFT 20 Sensors

Non-spinning Applications (Simulation Lab)

12 Vdc Power Supply

(with 4 connections)

Customer Supplied

Data Recorder

Transducer Interface

(TI)

Transducer Signals

Output

Signals

PC

Communication

S20-27

Non-spinning Applications (Simulation Lab)

The SWIFT sensor can be fully integrated into the simulation process, since it is
an optimal feedback transducer for use with MTS Remote Parameter Control

®

(RPC

) software. The transducer takes data at points where fixturing inputs are
located rather than at traditional instrumentation points along the vehicle’s
suspension. Using the SWIFT sensor saves you instrumentation time, and fewer
iterations are required to achieve good simulation accuracy.

Measuring spindle loads allows engineers to generate generic road profiles.
Generic road profiles are portable across various vehicle models, do not require
new test track load measurements for each vehicle, and eliminate additional
RLDA tasks.

Four of the six loads measured by the transducer directly correlate to the MTS
Model 329 Road Simulator inputs: vertical force, longitudinal force, lateral force,
and braking input.

The same transducers used to collect road data at the test track can be mounted
directly in the wheel adapters of the MTS Model 329 Road Simulator. For
durability testing, an aluminum SWIFT sensor can be used for iterations within
the RPC process. The aluminum SWIFT sensor should then be removed for the
durability cycles, to preserve its fatigue life. It can be replaced by an adapter
plate, available from MTS, to duplicate the mass and center of gravity of the
actual SWIFT sensor. If a SWIFT sensor is to be used during full durability tests,
we suggest using the titanium model, which has a higher fatigue rating.

®

In a typical non-spinning application, a SWIFT sensor is mounted on a road
simulation test fixture, as shown in the following figure.

Non-spinning Application (Laboratory Simulation)

SWIFT 20 Sensors Hardware Overview

17

Construction

S20-57

Modified Rim

Hub Adapter

Transducer

Slip Ring

Bracket

Slip Ring

Encoder

Construction

The SWIFT sensor has one-piece construction for outstanding fatigue life, low
hysteresis, and high stiffness. Its compact package has a minimal effect on inertia
calculations, and a minimal dynamic effect on the test vehicle.

The transducer can be used for developing conventional durability tests on the
MTS Model 329 Road Simulator. Normally, the transducer is replaced with an
equivalent wheel adapter after the simulation drive signals are developed and
prior to the start of the test.

The SWIFT sensor includes several mechanical and electrical components.

Slip Ring Assembly

Transducer The transducer attaches directly to a modified wheel rim. On the test track, it

spins with the wheel. It does not spin on a road simulator. The transducer is
available in two materials: aluminum for spinning applications where the priority
is on light weight, and titanium for non-spinning or higher force applications,
where the priority is on durability.

The transducer’s unibody design means there are no multiple parts welded or
screwed together.

The transducer has four beams with strain gages that measure six orthogonal
outputs:

Fx—longitudinal force
Fy—lateral force
Fz—vertical force
Mx—overturning moment
My—acceleration and brake torque
Mz—steering moment

It has onboard conditioning and amplifiers to improve the signal-to-noise ratio.

Hardware Overview

18

SWIFT 20 Sensors

Construction

Telemetry Model Slip Ring Model

Slip

Ring

Slip Ring

Bracket

Transducer

Interface

Cable Bracket

Anti-rotate Device

(Bend to fit vehicle)

Transducer

Customer-supplied

Attachment Bracket

Wheel Rim

Customer-supplied

Rim Adapter Flange

Attach to

vehicle

suspension

Wheel Rim

Transducer

Anti-rotate

Device

Hub

Adapter

Hub

Adapter

Brake Rotor

Telemetry Bearing

with Hub Electronics

Transducer

Interface

Cable

S20-49

Hub adapter The hub adapter attaches to the inner diameter of the transducer, allowing you to

place it at the original position of the spindle face of the vehicle. The hub adapter
enables you to maintain the original position of the tire on the vehicle while the
transducer is attached to the vehicle (the tire will not protrude from the vehicle).

Components Set Up for Test Track

Slip ring bracket The slip ring bracket is used to attach the slip ring to the transducer. It has

internal wiring that provides excitation power to the strain gage bridges and
brings signals out from the transducer to the slip ring.

Encoder An encoder measures the angular position of the transducer. The SWIFT sensor

uses an optical encoder that counts off “ticks” to measure the angular position as
the wheel rotates. In applications using a slip ring, the integral encoder measures
2048 (512 plus quadrature) points per revolution (ppr) with a resolution of 0.18
degrees and an accuracy of 0.18 degrees.

Slip ring The slip ring allows you to output the transducer bridge signals and angular

position to the TI. A transducer data cable attaches from the slip ring to the back
panel of the TI. The slip ring is not typically used for non-spinning applications.

Anti-rotate device The anti-rotate device is attached to the stator portion of the slip ring and the

SWIFT 20 Sensors Hardware Overview

vehicle’s suspension (or other non-rotating point). It is able to move up and down
with the vehicle. Its primary function is to provide a fixed reference point for the
optical encoder. Its secondary function is to prevent the cable from rotating with
the wheel and becoming tangled or breaking.

The anti-rotate device is mainly used for road data collection. Although it can
also be used for short periods of time on a road simulator. MTS does not
recommend this use. Due to the extreme fatigue loading characteristics of
durability testing on road simulators, we suggest that you either remove the slip
ring assembly before installing the vehicle on a road simulator, or use it only for
iteration passes, then promptly remove it.

19

Construction

S20-55

Slip Ring

Assembly

Suspension/

Unsprung Mass

Tire must not

hit bracket when

loaded or rotating.

Anti-Rotate Bracket

must be stiff

(preferably steel

or stiff aluminum

tubing).

Center line

of Wheel

Anti-Rotate

Assembly

Vehicle
Fender

Bracket must not

hit fender at

extreme end of

suspension travel

Slip Ring ModelSlip Ring Model

Cable Conduit

Bracket

Alignment Fixture

Example of
Anti-Rotate

Bracket Attached

to Brake Caliper

Example of
Anti-Rotate

Bracket Attached

to Strut

Cable
Conduit
Bracket

Telemetry Model

Accelerometer

(optional)

Shunt A

Load

Shunt B

S20-54

Connector Housing

S20-58

Non-Spinning

Cable Assembly

Non-Spinning

Connector Bracket

Spinning

Slip Ring

Bracket

Non-Spinning

Connector Bracket

The slip ring anti-rotate device should be configured such that no loading occurs
to the slip ring throughout all loading and suspension travel. This means that
when you attach the anti-rotate device to the vehicle, you must consider all
possible motion of the suspension. The anti-rotate device should not bump
against the wheel well at any time; any jarring of the anti-rotate arm will damage
the slip ring. For steering axles, the anti-rotate bracket must be mounted to part of
the unsprung suspension that steers with the tire, such as the brake caliper. For
additional anti-rotate device mounting recommendations, refer to the Anti-Rotate
Customer/User Assembly drawing at the back of this manual.

Non-spinning

connector housing or

connector bracket

20

Hardware Overview

The non-spinning connector housing or the non-spinning connector bracket (both
shown below) provide a connection between the SWIFT and the TI electronics
for non-spinning use. Both assemblies incorporate rugged connectors suitable for
durability testing. The non-spinning connector housing can also include an
optional connector with built-in, tri-axial accelerometers.

SWIFT 20 Sensors

Construction

Low-profile TI

Mini TI

Transducer Interface

(TI)

The TI comes in two versions: a Low-Profile TI and the newer Mini TI.
Information on the Low-Profile TI can be found in this manual. Information on
the Mini TI can be found in a separate product manual (MTS part number

100214316).
The Low-Profile TI conditions the power supply, and uses previously stored

calibration values to convert the eight bridge outputs and the encoder signal to
six non-rotating analog outputs (Fx, Fy, Fz, Mx, My , Mz) plus an angle output (or
angular velocity with the Mini TI). The force and moment outputs have a value
of 10 V full scale, unless a different full-scale output is requested by a customer.
The angle output is a 0–5 V sawtooth output.

Additional

components

SWIFT 20 Sensors Hardware Overview

Additional components that are supplied with your SWIFT sensor include shunt
and transducer data cables, TI power cable, a SWIFT Transducer Interface
Utilities disk, and the calibration file. MTS can also provide a 12 V DC power
converter for use in the test laboratory.

21

Construction

Design Features

Flexure isolation The SWIFT sensor has a very stiff outer ring and flexured beam isolation which

render it relatively insensitive to stiffness variations in matings with rims and
road simulator fixtures.

Flexure isolation minimizes thermal expansion stresses. With flexure isolation, if
the inner hub experiences thermal expansion the beams are allowed to expand
out, resulting in lower compressive stress on the beams.

Thermal stability The entire sensor is machined from a solid, specially forged billet of high

strength aluminum or titanium. The absence of bolted joints permits an efficient
transfer of heat across the sensor structure, minimizing temperature differentials
in the gaged area.

As mentioned earlier, flexure isolation allows thermal expansion with minimal
stresses.

The transducer is designed to accommodate the high temperature environments
that occur during severe driving and braking events. Individual temperature
compensation of each strain gage bridge minimize temperature induced
variations in accuracy. Since minimal electronics reside on the SWIFT sensor, it
can easily tolerate high temperatures. The temperature rating for the SWIFT
sensor is 125° C (257° F) at the spindle hub.

Temperature compensation is done on each bridge for better performance in
transient or non-uniform temperature occurrences.

Low hysteresis The SWIFT sensor has very low hysteresis, since the sensing structure is

constructed with no bolted joints. Micro slippage in bolted joints contributes
most of the hysteresis in highly stressed structures. Hysteresis errors due to
micro-slip at joints can contribute to unresolvable compounding errors in
coordinate transformation of the rotating sensor.

Low noise On-board amplification of the transducer bridges minimizes noise contribution

prior to data transmission via low noise slip ring.

Low cross talk The advanced design of the SWIFT sensor means that it has very low cross talk.

The alignment of the sensing element is precision machined. This alignment is
critical to achieving minimum cross talk error between axes and minimum errors
in coordinate transformation (from a rotating to a nonrotating coordinate system).
Any small amount of cross talk present is compensated by the TI.

Velocity information Angular position output is available from the TI when it is used in the spinning

mode with the encoder. For the Low-Profile TI, this angular out put can be used to
calculate wheel velocity. In non-spinning applications, accelerometers can be
integrated into the transducer connector housing.

The Mini TI has a user selectable angle or angular velocity output.

Hardware Overview

22

Note MTS does not supply any conditioning electronics for accelerometers.

Ask your MTS consultant for more information about this option.

SWIFT 20 Sensors

Coordinate System

Fx

Fy

Fz

Mz

Mx

My

Transducer

Interface

Output signals

+

10 Volts

Angular
Position

Bridge

Outputs

S20-06

+Mz

+Fz

+Fy

+My

+Mx

+Fx

Forces acting on outer ring

S20-07

In the transducer, independent strain gage bridges measure forces and moments
about three orthogonal axes. The signals are amplified to reduce the signal-to­noise ratio. An encoder signal indicates angular position, which is used to
convert raw force and moment data from the rotating transducer to a vehicle­based coordinate system. The force and moment and encoder information is sent
to the transducer interface (TI).

Coordinate System

The TI performs cross talk compensation and converts the rotating force and
moment data to a vehicle coordinate system. The result is six forces and moments
that are measured at the spindle: Fx, Fy, Fz, Mx, My, and Mz. A seventh (angle)
output is available for tire uniformity information, angular position, or to
determine wheel speed (depending on the data acquisition configuration).

The coordinate system shown below was originally loaded into the TI settings by
MTS. It uses the right-hand rule.

The SWIFT coordinate system is transducer-based, with the origin located at the

reference drawings at the end of this manual. Positive loads are defined as
applied to the outer ring of the transducer.

SWIFT 20 Sensors Hardware Overview

center of the transducer. The lateral offset of the transducer is illustrat ed in the

23

Coordinate System

The direction of positive forces follows the right hand rule:

• Vertical force (Fz) is positive up

• Lateral force (Fy) is positive out of the vehicle

• Longitudinal force (Fx) is positive fore or aft of the vehicle depending on

which side of the vehicle the SWIFT is mounted

You can change to the MTS Model 329 Road Simulator convention (lateral load
into the vehicle is always positive) or to any coordinate system by changing the
polarities in the calibration file. For instructions on how to change the coordinate
system polarities, see the chapter, “Setting up the Transducer Interface” in this
manual or refer to “Transducer Interface Setup” in the Mini TI manual.

The Mini TI has the capability to offset the coordinate system. For example you
can offset the coordinate system such that the coordinate system is at the center
of the rim instead of the default coordinate system location at the center of the
transducer. The Mini TI manual has additional information.

Hardware Overview

24

SWIFT 20 Sensors

Specifications

Specifications

SWIFT 20 Transducer Performance

Parameter Specification

Use

SWIFT 20 A (aluminum) for

SWIFT 20 T (titanium) for
Maximum usable rpm
Maximum speed
fits rim size (usable range)

Maximum hub bolt circle diameter
accommodates M12 or 1/2 inch studs

Input voltage required
Input power required per transducer
Output voltage ± full scale calibrated load

Aluminum Titanium

SAE J328 rated load capacity
Standard Maximum Calibrated Load Rating‡

Longitudinal force (Fx)

Lateral force range (Fy)

Vertical force range (Fz)

Overturning moment (Mx)

Driving/braking moment (My)

Steering moment (Mz)
Resolution (analog system)
Noise level (peak-to-peak 0-500Hz)
Performance accuracy

Nonlinearity

Hysteresis

Modulation§

Cross talk
Maximum operating temperature

Low level amplifiers

Transducer interface

* A special flange configuration is required for a 12 inch wheel. Larger diameter rims can be used, providing that overall

clearance from brake calipers and suspension components is maintained.
† Load impedance >1 k
‡ The actual calibrated range may be different based on individual customer requirements. Consult the calibration range

sheet that accompanies each transducer for the correct calibration range.

§ Typical value on most steel rims. Aluminum rims typically have slightly higher modulation, but at a lower added weight.
# Each SWIFT sensor is calibrated on an MTS calibration machine. MTS provides complete documentation of calibration

values for each SWIFT unit

#

Ω; 0.01 µF (maximum) load capacitance.

4.3 kN (965 lbf) 7.0 kN (1,580 lbf)

±21 kN (±4,720 lbf) ±30 kN (±6,745 lbf)
±16 kN (±3,595 lbf) ±25 kN (±5,620 lbf)

±21 kN (±4,720 lbf) ±30 kN (±6,745 lbf)
±4 kN•m (±35,405 lbf•in) ±6 kN•m (±53,105 lbf•in)
±5 kN•m (±44,255 lbf•in) ±8.5 kN•m (±75,230 lbf•in)
±4 kN•m (±35,405 lbf•in) ±6 kN•m (±53,105 lbf•in)

15 N (3.4 lbf) 25 N (5.6 lbf)

low weight, high sensitivity

high fatigue life, durability

2,200

240 kph (150 mph)

12–15 inch

*

4.5 inch (114.3 mm)

10–17 VDC

30 W maximum (22 W typical)

†

±10 V

Infinite

1.0% full scale

0.5% full scale
≤3.0% reading

1.5% full scale

70°C (158°F)
50°C (122°F)

SWIFT 20 Sensors Hardware Overview

25

Specifications

Transducer Center-of-Gravity

Transd ucer Center-of-Gravity and Inertia Specifications

Material

Aluminum Titanium

X

0.0 mm 0.000 in 0.0 mm 0.000 in

cg

Y

19.2 mm 0.755 in 19.2 mm 0.755 in

cg

Z

0.0 mm 0.000 in 0.0 mm 0.000 in

cg

I

xx

180 kg·cm262 lbm·in2290 kg·cm299 lbm·in

I

yy

353 kg·cm2121 lbm·in2569 kg·cm2195 lbm·in

I

zz

180 kg·cm262 lbm·in2290 kg·cm299 lbm·in

Low-Profile Transducer Interface (part 1 of 2)

Parameter Specification

Physical

Height
Width
Depth
Weight
Rack Mounting Kit

31.75 mm (1.25 in)

431.8 mm (17 in)

215.9 mm (8.5 in.)

1.68 kg (3 lb 11.1 oz)
Optional

2

2

2

*

Environmental

Ambient temperature
Relative humidity

Hardware Overview

26

0° C (32° F) to 50° C (122° F)
0 to 85%, non-condensing

SWIFT 20 Sensors

Low-Profile Transducer Interface (part 2 of 2)

Parameter Specification

Power Requirements

Input voltage
Supply current
Fuse

Angular velocity

Encoder limit
Processing limit
Encoder resolution

10–17 V DC
2 A typical, 3 A maximum at 12 V DC
3 A fast-blow

2,200 rpm maximum
10,000 rpm maximum
2048 counts per revolution

(512 pulses with quadrature)

Specifications

Time delay (encoder tick to main outpu t stable)
Transducer cable length
Shunt cable length
Analog outputs

Voltage

12 µs (typical)
100 ft maximum
100 ft maximum

±10 V range† (force and moment outputs)
0–5 V sawtooth (angle output)

Capacitive load
Current
Noise at output, with typical gains

0.01 µF maximum
6 mA maximum
7 mVpp, DC - 500 Hz (typical)

15 mVpp, DC - 500 Hz (maximum)

Bandwidth (bridge input to main output)

–3 dB at 30.1 kHz (typical)
90 degree at 16.6 kHz (typical)

* Add 25.4 mm (1.0 in) for ground lugs.
† Standard from MTS. Other full scale voltages can be evaluated and may be provided at special

request.

Low-Profile Transducer Interface Communications (part 1 of 2)

Parameter Specification

Communications Channel # 1
(Remote Host Connections)

Baud rates
Parity
Stop bits
Data bits
Isolated RS-232/RS-485 interface power

supply
Electrical interface

19,200 Kbits/s
None
1
8
+5 V DC @ 200 mA maximum

Isolated RS-232 or RS-485 remote host connection
Isolated RS-485 TI to TI connection

Maximum number of devices that can be part
of a RS-485 multidrop chain

32 with RS-232 remote host
31 with RS-485 remote host

*

Maximum cable length

SWIFT 20 Sensors Hardware Overview

27

Specifications

Low-Profile Transducer Interface Communications (part 2 of 2)

Parameter Specification

For RS-232 host:

50 ft from host to the first (nearest) TI,
and
300 ft from the first TI to the last SWIFT TI in the RS-

485 multidrop chain

For RS-485 host:

300 ft from host to the last (furthest) TI in the RS-485
multidrop chain

* Includes all compatible devices, such as an MTS 407 controller. A maximum of only nine transducer

interfaces can be connected, because the addresses are limited to 1–9.

Hardware Overview

28

SWIFT 20 Sensors

Calibration

Calibration

Important The following sections include information related to the Low-

Profile Transducer Interface (TI). For SWIFT transducers designed
to operate with the newer Mini TI, there is a separate manual that
documents the Mini TI software utilities (MTS part number

100214316).

Each transducer is calibrated by MTS before shipment. The transducer and Low­Profile TI may be returned to MTS for repair and recalibration as required.

Calibration is performed at MTS on a special fixture that is capable of applying
multiple loads to the transducer. During calibration, raw signals are measured.
The calibration gains and cross talk compensation values are computed from this
raw data. These gains are recorded in a calibration file.

A unique calibration file is supplied for each transducer. The serial number of the
Low-Profile TI associated with the transducer is listed at the top of the
calibration file. A label with the serial number of the Low-Profile TI box (and the
SWIFT sensor with which it was originally calibrated) is located at the back of
each Low-Profile TI box.

The calibration file is loaded into the Low-Profile TI non-volatile RAM by MTS
before the transducer is shipped. A copy of the file is also provided on a diskette.

MTS verifies the calibration by applying loads to the transducer, measuring the
main outputs and checking for accuracy. Final calibration reports are provided
with each transducer.

Shunt calibration At the end of the calibration process, a shunt calibration is performed. During a

shunt calibration, a resistance is introduced into the bridge circuit. The difference
between the shunted and unshunted voltage is the delta shunt reference value for
each bridge. That value is saved in the calibration file, which is downloaded from
a PC or laptop computer and stored in non-volatile memory in the Low-Profile
TI.

At any time afterward, pressing the Shunt button on the front of the Low-Profile
TI causes each of the strain gage bridges to be shunted in sequence, and the
measured shunt voltage (delta shunt measured value) is compared to the
reference value.

An acceptable tolerance range is also loaded into the Low-Profile TI memory
during system calibration. One tolerance value is used for all bridges. This value
is loaded as a percentage of allowable deviation from the delta shunt values. For
example, if the FX1 bridge has a shunt delta reference value of –3.93, and the
tolerance is set at 2 (percent), the acceptable range for the measured value would
be –3.85 to –4.01.

SWIFT 20 Sensors Hardware Overview

29

Calibration

When you press the Shunt button, the associated Shunt LED lights. As the Low­Profile TI automatically switches throug h the series of bridges, it verifies that the
outputs are within the accepted tolerance range. If all bridge shunt values fall
within the tolerance range, the Shunt LED on the front panel will go off (after
several seconds). If any bridge fails to fall within the shunt tolerance range, the
LED will blink, indicating that the shunt calibration has failed. See the chapter,

“Troubleshooting,” on page 127, for more information on dealing with shunt

calibration failures.

ShuntTolerance=2
FX1ShuntDeltaRef=-3.91836
FX2ShuntDeltaRef=-3.91896
FY1ShuntDeltaRef=-3.92366
FY2ShuntDeltaRef=-3.91639
FY3ShuntDeltaRef=-3.91824
FY4ShuntDeltaRef=-3.92494
FZ1ShuntDeltaRef=-3.92282
FZ2ShuntDeltaRef=-3.92673
FX1ShuntDeltaMeas=-3.91854
FX2ShuntDeltaMeas=-3.9192
FY1ShuntDeltaMeas=-3.92412
FY2ShuntDeltaMeas=-3.91572
FY3ShuntDeltaMeas=-3.91815
FY4ShuntDeltaMeas=-3.92464
FZ1ShuntDeltaMeas=-3.9227
FZ2ShuntDeltaMeas=-3.92646

Example of Calibration File Shunt Data

The above example shows shunt data from the calibration file. This data may be
transferred, using the TIXFER program, from the transducer interface RAM to a
computer or from a computer to the transducer interface RAM. Note that items
marked ShuntDeltaMeas are uploaded from RAM, but not downloaded from the
computer. (For more information on TIXFER, see the chapter, “Software
Utilities.”

Shunt verification You can check the electrical integrity of a transducer at any time by pressing the

Shunt switch. Subsequent shunt commands compare the current feedback values
against those stored in the Low-Profile TI. You may set the tolerance values for
each Low-Profile TI by editing the calibration file (see the chapter, “Setting up
the Transducer Interface”, for instructions).

If the current feedback values from a shunt calibration are outside the tolerance,
the Shunt LED blinks to indicate a failure.

Hardware Overview

30

SWIFT 20 Sensors