Xsens MTi 10 Series User manual

Xsens Technologies B.V.
Xsens North America, Inc.
Pantheon 6a
P.O. Box 559
7500 AN Enschede
The Netherlands
phone [phone]
fax [phone]
e-mail [email protected]m
internet www.xsens.com
10557 Jefferson Blvd,
Suite C
CA-90232 Culver City
USA
phone [phone]
fax [phone]
e-mail [email protected]m
internet www.xsens.com
Document MT0605P, Revision E, 17 January 2014
MTi 10-series and MTi 100-series
MTi User Manual

Document MT0605P.E
© Xsens Technologies B.V.
MTi User Manual
ii
Revisions
Revision
Date
By
Changes
A
26 Sep 2012
MHA
Initial release
B
18 Dec 2012
MHA
Included MTi-G-700
C
07 May 2013
MHA
D
28 October 2013
MHA
Added NMEA, StartSampling,
vibration mounts
E
17 January 2014
MHA
Added product code, 3V3 and remark
on termination resistor
© 2005-2014, Xsens Technologies B.V. All rights reserved. Information in this document is subject to
change without notice. Xsens, MVN, MotionGrid, MTi, MTi-G, MTx, MTw, Awinda and KiC are
registered trademarks or trademarks of Xsens Technologies B.V. and/or its parent, subsidiaries and/or
affiliates in The Netherlands, the USA and/or other countries. All other trademarks are the property of
their respective owners.

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Table of Contents
1REFERENCES ..................................................................................................................................... 2
2INTRODUCTION ................................................................................................................................ 3
2.1 MTI 10-SERIES ................................................................................................................................. 3
2.1.1 MTi-30 AHRS........................................................................................................................ 3
2.1.2 MTi-20 VRU ......................................................................................................................... 3
2.1.3 MTi-10 IMU ......................................................................................................................... 3
2.2 MTI 100-SERIES ............................................................................................................................... 4
2.2.1 MTi-G-700 GPS/INS .............................................................................................................. 4
2.2.2 MTi-300 AHRS ...................................................................................................................... 4
2.2.3 MTi-200 VRU........................................................................................................................ 4
2.2.4 MTi-100 IMU........................................................................................................................ 4
2.2.5 Identifying device functionality using the unique Device Identifier ............................................ 5
2.2.6 Product code ........................................................................................................................ 5
2.3 EVOLUTION OF MTI PRODUCTS.............................................................................................................. 6
2.4 OVERVIEW MTI DEVELOPMENT KIT ........................................................................................................ 7
2.4.1 Contents .............................................................................................................................. 7
2.5 INSTALLATION................................................................................................................................... 8
2.5.1 Transient accelerations ......................................................................................................... 8
2.5.2 Vibrations ............................................................................................................................ 8
2.5.3 Magnetic materials and magnets .......................................................................................... 9
2.6 TYPICAL USER SCENARIOS ..................................................................................................................10
2.6.1 MT Software Suite .............................................................................................................. 10
2.6.2 Getting Started with the MT Manager..................................................................................11
2.6.3 Using the Software Development Kit (SDK) ...........................................................................12
2.6.4 Direct low-level communication with MTi .............................................................................14
2.6.5 Migration from MT SDK 3.3 (CMT) ....................................................................................... 14
2.6.6 Terms of use MT Software Suite...........................................................................................15
3MTI SYSTEM OVERVIEW .................................................................................................................. 16
3.1 CALIBRATION .................................................................................................................................16
3.2 XSENS KALMAN FILTER (XKF3I)FOR MTI 10-SERIES ..................................................................................16
3.2.1 Using the acceleration of gravity to stabilize inclination (roll/pitch) ........................................16
3.2.2 Using the Earth magnetic field to stabilize yaw .....................................................................17
3.2.3 Initialization.......................................................................................................................17
3.2.4 XKF3i filter profiles.............................................................................................................. 17
3.3 XSENS SENSOR FUSION ALGORITHM FOR MTI 100-SERIES ............................................................................19
3.3.1 MTi 100-series filter ............................................................................................................ 19
3.3.2 Transient accelerations .......................................................................................................19
3.3.3 Magnetic distortions........................................................................................................... 19
3.3.4 Loss of GPS ........................................................................................................................ 19
3.3.5 MTi 100-series filter profiles ................................................................................................19
3.3.6 MTi-G-700 filter profiles ......................................................................................................20
4OUTPUT SPECIFICATION .................................................................................................................. 22
4.1 OVERVIEW OF DATA OUTPUTS .............................................................................................................23
4.1.1 MTData2 output in XBus protocol ........................................................................................23
4.1.2 NMEA protocol...................................................................................................................24

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4.2 COORDINATE SYSTEMS ......................................................................................................................25
4.2.1 Calibrated inertial data and magnetic field data ................................................................... 25
4.2.2 Delta_angle and delta_velocity............................................................................................25
4.2.3 Orientation data................................................................................................................. 26
4.2.4 Velocity data......................................................................................................................27
4.2.5 Position data...................................................................................................................... 27
4.3 ORIENTATION PERFORMANCE SPECIFICATION ...........................................................................................30
4.4 POSITION AND VELOCITY PERFORMANCE SPECIFICATION (MTI-G-700) ............................................................ 31
4.5 ORIENTATION OUTPUT MODES............................................................................................................. 31
4.5.1 Quaternion orientation output mode ...................................................................................32
4.5.2 Euler angles orientation output mode .................................................................................. 33
4.5.3 Rotation Matrix orientation output mode.............................................................................33
4.6 SENSOR DATA PERFORMANCE SPECIFICATION ...........................................................................................35
4.6.1 Gyroscopes ........................................................................................................................ 35
4.6.2 Accelerometers and magnetometer .....................................................................................36
4.6.3 Y zBarometer .....................................................................................................................36
4.6.4 GPS receiver.......................................................................................................................37
4.7 BUILT-IN SELF-TEST ..........................................................................................................................38
4.8 TEST AND CALIBRATION CERTIFICATE .....................................................................................................39
4.9 SENSORS DATA OUTPUTS....................................................................................................................40
4.9.1 Physical sensor model .........................................................................................................40
4.9.2 Calibrated delta_q and delta_v outputs................................................................................41
4.9.3 Calibrated inertial and magnetic data outputs ...................................................................... 41
4.9.4 Free acceleration ................................................................................................................ 41
4.9.5 Uncalibrated raw output mode............................................................................................42
4.10 LEGACY OUTPUT MESSAGES ................................................................................................................ 43
4.11 RESET OF OUTPUT OR REFERENCE CO-ORDINATE SYSTEMS ............................................................................ 44
4.12 TIMESTAMP AND PACKET COUNTER OUTPUT ............................................................................................ 47
4.12.1 Packet counter ................................................................................................................... 47
4.12.2 Time UTC ........................................................................................................................... 47
4.12.3 Time stamp (Sample Time Fine) ...........................................................................................47
4.12.4 Setting UTC time on non-GPS MTi’s......................................................................................47
4.13 STATUS BYTE ..................................................................................................................................48
5BASIC COMMUNICATION ................................................................................................................ 50
5.1 INTRODUCTION ...............................................................................................................................50
5.2 STATES.........................................................................................................................................50
5.3 MESSAGES ....................................................................................................................................51
5.3.1 Message structure .............................................................................................................. 51
5.3.2 Message usage ..................................................................................................................52
5.3.3 Common messages.............................................................................................................53
5.4 COMMUNICATION TIMING .................................................................................................................54
5.5 TRIGGERING AND SYNCHRONIZATION .....................................................................................................57
5.5.1 External device triggers MTi (Send Latest) ............................................................................ 57
5.5.2 Marker in MT data (Trigger Indication) ................................................................................ 57
5.5.3 MTi triggers external devices (Interval Transition Measurement) ...........................................58
5.5.4 Clock synchronization (Clock Bias Estimation) .......................................................................59
5.5.4.1 Clock Bias Estimation from GPS ...........................................................................................59
5.5.5 StartSampling .................................................................................................................... 59
5.5.6 Combining synchronization functions ...................................................................................60

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5.6 INTERNAL CLOCK ACCURACY ................................................................................................................ 61
5.6.1 Clock of MTi’s without GPS receiver ..................................................................................... 61
5.6.2 Clock of MTi-G-700 GPS/INS ................................................................................................61
5.7 DEFAULT SERIAL CONNECTION SETTINGS ................................................................................................61
5.7.1 General definitions for binary data.......................................................................................62
5.7.2 Serial or USB communication...............................................................................................62
6PHYSICAL SPECIFICATIONS............................................................................................................... 63
6.1 PHYSICAL PROPERTIES OVERVIEW.......................................................................................................... 63
6.2 POWER SUPPLY ............................................................................................................................... 63
6.2.1 Alternative 3V3 power supply .............................................................................................. 64
6.3 MECHANICAL AND ELECTRICAL INTERFACE SPECIFICATIONS ...........................................................................65
6.3.1 Encased MTi connectors overview........................................................................................ 65
6.3.2 OEM connections overview ................................................................................................. 67
6.3.3 Additional interface specifications .......................................................................................69
6.3.4 Using the MTi MkIV with an external USB converter .............................................................. 70
6.4 HOUSING MECHANICAL SPECIFICATIONS.................................................................................................. 71
6.4.1 Environmental protection of the housing .............................................................................. 71
6.4.2 Dimensions MTi.................................................................................................................. 71
6.4.3 Mounting the MTi-OEM ......................................................................................................71
6.4.4 MTi 10-series technical drawing .......................................................................................... 72
6.4.5 MTi 100-200-300 technical drawing ..................................................................................... 73
6.4.6 MTi-G-700 technical drawing ..............................................................................................74
6.4.7 MTi-OEM technical drawing ................................................................................................75
7IMPORTANT NOTICES...................................................................................................................... 76
7.1 SAFETY INSTRUCTIONS.......................................................................................................................76
7.2 ABSOLUTE MAXIMUM RATINGS ............................................................................................................ 76
7.3 MAINTENANCE ...............................................................................................................................76
7.4 CE DECLARATION OF CONFORMITY FOR THE MT DEVICES ............................................................................77
7.5 FCC DECLARATION OF CONFORMITY FOR THE MT DEVICES ..........................................................................78
7.6 WARRANTY AND LIABILITY .................................................................................................................. 79
7.7 CUSTOMER SUPPORT........................................................................................................................79

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1 References
Reference
id
Document description
[LLCP]
“MT Low-Level Communication Protocol Documentation.pdf”, document ID
MT0101P
[MTM]
“MT Manager User Manual.pdf”, document ID MT0216P
[XDA_DOC]
XDA doxygen HTML documentation. Found in Xsens folder structure
[MTI_TD]
“MTi Technical Datasheet.pdf”, document ID MT0503P

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2 Introduction
The MTi product portfolio from Xsens currently has 7 family members ranging in functionality from
inertial measurement units (IMU’s) to a fully integrated GPS/INS solution. All products contain a 3D
inertial sensor assembly (ISA: gyroscopes and accelerometers) and 3D magnetometers, with
optionally a barometer and GNSS receiver.
The MTi product range is divided in two series, the MTi 10-series and the MTi 100-series. The MTi 10-
series is Xsens’ entry level model with robust accuracy and a limited range of IO options. The 100-
series is a revolutionary new class of MEMS IMU’s, orientation and position sensor modules offering
unprecedented accuracies and a wide array of IO interfaces.
All MTi’s have a powerful multi-processor core design, capable of processing roll, pitch and yaw with
extremely low latencies, as well as outputting calibrated 3D linear acceleration, rate of turn (gyro),
(earth) magnetic field and atmospheric pressure (100-series only) data. The MTi-G-700 GPS/INS also
offers 3D position and 3D velocity. Over 50 various output formats can be provided directly from the
MTi interface. The various outputs per product can be found in section 4.1.
This documentation describes the use, basic communication interfaces and specifications of all the 7
MTi’s. Where they differ is clearly indicated. All products are designed to be interchangeable from a
mechanical and software interface point of view.
2.1 MTi 10-series
The MTi 10-series is the basic product range of the MTi
product portfolio, offering inertial data and orientation data at
an affordable price. The MTi 10-series consists of 3 products
that have various integration levels.
The MTi-10 series can easily be recognized by the silver base
plate. There are no visual differences between the MTi-10
IMU, MTi-20 VRU and MTi-30 AHRS, other than the label.
2.1.1 MTi-30 AHRS
The MTi-30 AHRS is a full gyro-enhanced Attitude and Heading Reference System (AHRS). It outputs
drift-free roll, pitch and true/magnetic North referenced yaw, plus sensors data: 3D acceleration, 3D
rate of turn and 3D earth-magnetic field data. All products of the MTi 10-series are also capable of
outputting data generated by the Strapdown integration algorithm (orientation and velocity increments
∆q and ∆v).
2.1.2 MTi-20 VRU
The MTi-20 VRU is a 3D vertical reference unit (VRU), which means that it outputs the same data as
the MTi-30, except for the referenced yaw. They yaw is unreferenced, though still superior to just
gyroscope integration.
2.1.3 MTi-10 IMU
The MTi-10 IMU is a 3D inertial measurement unit (IMU) that outputs 3D acceleration, 3D rate of turn
and 3D earth-magnetic field data, so it doesn’t process data to orientation. The MTi-10-IMU is also
capable of outputting data generated by the Strapdown integration algorithm (orientation and velocity
increments ∆q and ∆v).

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2.2 MTi 100-series
The MTi-100 series is the high-performance product
range of the MTi product portfolio, with accuracies
overpowering conventional MEMS AHRS’s, because
of the use of superior gyroscopes and a new
optimization filter, going beyond (Extended) Kalman
Filter implementations. In addition, the factory
calibration is more elaborate to make use of these
higher class gyroscopes.
The MTi 100-series can be recognized by the dark-
grey base plate and the holes on one side of the
casing. These holes are used for the adaptation of
the inside air pressure to atmospheric pressure,
required for a proper working of the barometer. Note that the electronics inside is protected with a vent
that keeps the casing IP67 rated. There are no visual differences between the MTi-100 IMU, MTi-200
VRU and MTi-300 AHRS, other than the label. The MTi-G-700 has an extra SMA connector to allow a
GPS antenna to be attached.
2.2.1 MTi-G-700 GPS/INS
The flagship of the MTi product portfolio is the MTi-G-700 GPS/INS, a fully integrated solution that
includes an onboard GPS receiver. The MTi-G-700-GPS/INS is thus capable of not only outputting
GPS-enhanced 3D orientation, it can also output AHRS-augmented 3D position and velocity, so that
velocity and position accuracy significantly improve with respect to the accuracy of the GPS receiver
alone. Furthermore, it provides 3D sensors data, such as acceleration, rate of turn, magnetic field, the
navigation solution of the GPS receiver and static pressure. Data generated from the strapdown
integration algorithm (orientation and velocity increments ∆q and ∆v) are available, as all other
processed data, at 400 Hz.
2.2.2 MTi-300 AHRS
The MTi-300 AHRS is a full gyro-enhanced Attitude and Heading Reference System (AHRS). It
outputs drift-free roll, pitch and true/magnetic North referenced yaw. It also outputs sensors data and
data generated from the Strapdown integration algorithm as well as described in section 2.2.1.
2.2.3 MTi-200 VRU
The MTi-200 VRU is a 3D vertical reference unit (VRU) and this unit too runs the Xsens sensor fusion
algorithm from the MTi-G-700 and MTi-300. The difference between the data of the MTi-300 and MTi-
200 is that yaw is unreferenced, though the yaw is still much better than just integrating rate of turn.
2.2.4 MTi-100 IMU
The MTi-100 IMU is a 3D inertial measurement unit (IMU) that outputs 3D acceleration, 3D rate of turn
and 3D earth-magnetic field data. The MTi-10-IMU is also capable of outputting data generated by the
Strapdown integration algorithm (orientation and velocity increments ∆q and ∆v).

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2.2.5 Identifying device functionality using the unique Device Identifier
Each Xsens product is marked with a unique serial device identifier referred to as the DeviceID. The
DeviceID is categorized per MTi product configuration in order to make it possible to recognize the MTi
(and thus its functionality and interface) by reviewing the DeviceID. The second digit of the DeviceID
denotes the functionality (e.g. ‘1’ for MTi-10 and MTi-100), the third digit denotes the product series (6
for MTi 10-series, 7 for MTi 100-series) and the fourth digit denotes the interface (e.g. ‘0’ for
RS232+USB). The last four digits are unique for each device; these four digits have a hexadecimal
format.
Below is a list of the products and interfaced with their corresponding products.
Product
RS232+USB
RS422
RS485+USB
MTi-10 IMU
0160xxxx
0161xxxx
0163xxxx
MTi-20 VRU
0260xxxx
0261xxxx
0263xxxx
MTi-30 AHRS
0360xxxx
0361xxxx
0363xxxx
MTi-100 IMU
0170xxxx
0171xxxx
0173xxxx
MTi-200 VRU
0270xxxx
0271xxxx
0273xxxx
MTi-300 AHRS
0370xxxx
0371xxxx
0373xxxx
MTi-G-700 GPS/INS
0770xxxx
0771xxxx
0773xxxx
2.2.6 Product code
The product code of the MTi MkIV consists of a number of characters that represent the product type,
full ranges of the inertial sensors, the interface and the casing option. The table below shows the
product code build-up.
Format
MTi-
####
-
*
A*
G*
Example
MTi-
G-700
-
2
A5
G4
-OEM
10
IMU
2
RS232
A5
5g
G4
450 º/s
Blank
Alu casing
20
VRU
4
RS485
A8
15g
G0
1000 º/s
-OEM
No casing
30
AHRS
6
RS422
100
IMU
200
VRU
300
AHRS
G-700
GPS/INS

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2.3 Evolution of MTi products
The MTi 10-series and MTi 100-series are Xsens 4th generation products, building on knowledge and
products from over a decade. They may be designated as MkIV MTi’s. In source code or software, this
can be Mk4.
In this manual, the term legacy MTi, MTx or MTi-G may be used. In these cases, it is referred to the
previous generation products, which set the standard in MEMS Motion Tracking technology.
Also included in the Motion Tracker range is the wireless MTw, which has a close resemblance to the
MTi 10-series and MTi 100-series in terms of system architecture and interfacing.
The MTi 10-series and MTi 100-series are described in detail in section 2.1 and 2.2, for completeness
they are listed below as well:
Product name
Description
Availability
Product photo
Legacy MTi
The standard setting MTi is a full 3D
AHRS, comparable in function to the
MTi-30 and MTi-300. It has a plastic
casing and aluminum bottom plate.
Product codes are in the form of MTi-
28A53G35
Introduced:
2005
Available: at
least till Dec
2013
Legacy MTi-OEM
The OEM board of the legacy MTi.
The board is green (contrary to
orange MTi-10s and MTi-100s OEM
board)
Introduced:
2006
Available: at
least till Dec
2013
Legacy MTx
Designed as a Motion Tracker for
human movements, this low-weight
Motion Tracker has a fully plastic
casing. Product codes are in the form
of MTx-28A53G25
Introduced:
2005
Available: at
least till Dec
2013
Legacy MTi-G
The GPS-aided MTi-G offers reliable
orientation during accelerations. The
successor of the MTi-G is the MTi-G-
700. The casing is as the legacy
MTi’s casing. Product codes are in
the form of MTi-G-28A53G35.
Introduced:
2007
Available: at
least till Dec
2013
MTw
The wireless MTw is available as
single Motion Tracker or in a time-
synchronized network together with
the Awinda station. Product codes are
in the form of MTw-38A70G20.
Introduced:
2010
MTi 10-series,
MTi 100-series
(including MTi-G-
700) and OEM
The latest 4th generation addition to
the Motion Trackers of Xsens (MkIV).
See section 2.1 and 2.2 for more
information. The OEM board is
orange. This manual focuses on
these products. Product codes are in
the form of e.g. MTi-30-2A5G4
Introduced:
2012

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2.4 Overview MTi Development Kit
The MTi development kit is a very easy to use
starter’s kit that allows for fast and easy
integration of the MTi in any user scenario. On
the right, the Development Kit is shown,
containing an MTi, USB cable, Software Suite
(on USB flash drive), a Quick Setup sheet and
license key (both in the lid).
The full content of the MTi DK is described
below.
2.4.1 Contents
Your MTi
Device specific Test and Calibration
Certificate
A letter with your individual software
license code
USB cable (CA-USB-MTi)
Multi-purpose cable (CA-MP-MTi) (optional)
Quick Setup Sheet
MT Software Suite on USB Flash Drive
oMT Low-level communication Documentation PDF [MT0101P]
oQuick Setup PDF
oMT Software Suite
Xsens MTi USB driver
MT Manager
MT Software Development Kit (MT SDK)
XsensDeviceApi.DLL, 32-bit and 64-bit
oDLL C and C++ interface
oCOM interface
XDA public source files (C, C++ wrapper)
Example source code and examples
oMATLAB: DLL example supported from MATLAB 2010b
oC: DLL example
oC++: public source example and DLL example
Linux SDK: beta release download from www.xsens.com
Magnetic Field Mapper (MFM)
Documentation
MTi User Manual [MT0506P]
MT Low level communication Documentation [MT0101P]
MT Magnetic Field Mapper Documentation [MT0202P]
XDA doxygen HTML API documentation
NOTE: the most recent version of the software, source code and documentation can always be
downloaded on the support section of www.xsens.com/en/support.

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2.5 Installation
2.5.1 Transient accelerations
The 3D linear accelerometers in the MTi are primarily used to estimate the direction of gravity to obtain
a reference for attitude (pitch/roll). During long periods (more than tens of seconds) of transient “free”
accelerations (i.e. 2nd derivative of position) the observation of gravity cannot be made. The sensor
fusion algorithms take these effects into account, but nonetheless it is impossible to estimate true
vertical without added information.
The impact of transient accelerations can be minimized when you take into account a few things when
positioning the device when installing it in the object you want to track/navigate/stabilize or control.
If you want to use the MTi to measure the dynamics of a moving vehicle/craft it is best to position the
measurement device at a position where you expect the least (smallest) transient accelerations. This
is typically close to the centre of gravity (CG) of the vehicle/craft since any rotations around the centre
of gravity translate into centripetal accelerations at any point outside the point of rotation, which is
usually close to the CG. The acceleration of the vehicle as a whole can of course not be taken into
account. For the MTi-G-700 however that have a valid GPS-fix, transient accelerations make the
orientation better observable.
The MTi 100-series cope better with transient “free” accelerations because of the higher-class
gyroscopes in the MTi 100-series. Next to the better hardware, the algorithm in the MTi 100-series is
superior in detecting and coping with challenging conditions, such as transient accelerations.
2.5.2 Vibrations
Although the MTi samples at 10kHz and includes a strap down integration algorithm with
coning/sculling compensation and vibration rejection, for best results it is recommended that the MTi is
mechanically isolated from vibrations as much as possible: since vibrations are measured directly by
the accelerometers, the following two conditions can make the readings from the accelerometers
invalid;
1. The magnitude of the vibration is larger than the measurement range of the accelerometer.
This will cause the accelerometer to saturate, which may be observed as a “drift” in the zero-
level of the accelerometer. This will show up as an erroneous roll/pitch.
2. The frequency of the vibration is higher than the bandwidth of the accelerometer. In theory,
such vibrations are rejected, but in practice they can still give rise to aliasing, especially if
close to the bandwidth limit. This can be observed as a low frequency oscillation. Further, high
frequency vibrations often tend to have large acceleration amplitudes (see item 1).
There is an effect on the gyroscopes as well and especially when the vibrations include high-frequent
coning motion, the gyroscope readings may become invalid. The MTi 100-series features vibration
rejecting gyroscopes, designed to better cope with these specific conditions.
Note that the sleeve on the Fischer connector can move by design in order to enable unmating.
Vibrations on the MTi, especially in the direction of the MTi’s x-axis, can make the sleeve vibrate
against the panel part of the connector. This may be visible in the accelerometer and gyroscope data.
To prevent this, the sleeve of the Fischer connector may be locked with the ring at the connector.
Xsens has tested a set of vibration dampeners on the MTi. Vibration dampeners are low-profile rubber
cylinders that allow the MTi to be mounted on an object without a direct metal to metal connection that
transduces vibrations from the object to the MTi. The vibration dampeners have been tested with
frequencies up to 1200 Hz that caused aliasing when the MTi was mounted directly on the vibration
table had no effect with the vibration dampeners fitted. The dampeners tested are manufactured by
Norelem and have part number 26102-00800855, www.norelem.com

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2.5.3 Magnetic materials and magnets
When an MTi is placed close to or on an object that is either magnetic or contains ferromagnetic
materials, the measured magnetic field is distorted (warped) and causes an error in measured yaw.
The earth magnetic field is altered by ferromagnetic materials, permanent magnets or very strong
currents (several amperes). In practice, the distance to the object and the amount of ferromagnetic
material determines the amount of disturbance. Errors in yaw (MTi-30, MTi-300 and MTi-G-700 only)
due to such distortions can become quite large, since the earth magnetic field is very weak in
comparison to the magnitude of many sources of distortion.
Whether or not an object is ferromagnetic should preferably be checked by using the MTi’s
magnetometers. It can also be checked with a small magnet, but be careful, you can easily magnetize
hard ferromagnetic materials, causing even larger errors. If you find that some object is magnetized
(hard iron effect), this is often the case with for example stainless steels that are normally not
magnetic, it may be possible to “degauss
1
” the object.
In most cases when the disturbance of the magnetic field caused by placement of the MTi on a
ferromagnetic object can be corrected for using a specialized calibration procedure commonly known
as a “hard- and soft iron calibration”. The calibration procedure (MTi-30, MTi-300 and MTi-G-700 only)
can be executed in a few minutes and yields a new set of calibration parameters that can be written to
the MTi non-volatile memory. This calibration procedure is implemented in the software module
“Magnetic Field Mapper” (MFM) that comes with the Software Suite.
Disturbance caused by objects in the environment near the MTi, like file cabinets or vehicles, that
move independently, with respect to the device cause a type of distortion that cannot be accounted
for
2
. With the MTi-300 and MTi-G-700, the effect of magnetic distortions will be lower than in the MTi-
30. Also, the choice for a filter profile greatly influences the total error amount because of the magnetic
distortion.
1
Degaussing is a procedure to apply strong alternating magnetic fields with decreasing magnitude in random
direction to an object that has been magnetized. The effect of the strong alternating fields is to remove any
magnetized (aligned) domains in the object. When degaussing, make sure the MTi is not attached to the object.
2
This type of disturbance is non-deterministic.

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2.6 Typical User Scenarios
This section is intended to help you find the right software component and corresponding
documentation for the way you want to use your MTi.
2.6.1 MT Software Suite
The MT Software Suite is a set of software components that can be used to communicate with the MTi
and to perform more high-level routines, such as logging, exporting, a magnetic field calibration and
updating of the firmware. Depicted below is a flow chart based on the software platform and the
preferred interface level.
On the left, three programs with GUIs are shown (Firmware Updater, Magnetic Field Mapper and MT
Manager). These programs offer the possibility to configure the MTi in a very easy way. The MT
Manager also can be used to communicate with the MTi.
The MT SDK contains all the developer code, such as a DLL, a shared object for x86 computers and
basic functionality in C source code for embedded systems. Of course it is possible to use lower level
communication options, down to the XBus low-level protocol; the most functionality however can be
found in the DLL and shared object.
The XBus low-level protocol is described in high detail in the Low Level Communication Protocol:
[LLCP].
The hardware driver of the USB interface for Linux can be found on http://github.com/xsens/xsens_mt.
The driver is also included in Linux kernel 3.9 and higher.

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2.6.2 Getting Started with the MT Manager
The easiest way to get started with your MTi is to use the MT Manager software for Windows XP/W7.
This easy to use software with a Windows user interface allows you to:
record data and playback/review data
view orientation, position and velocity in real-time (if available)
view inertial and magnetic sensor data in real time
view low-level communication and XDA communication via message terminals
export log files to ASCII and KML/KMZ
change and view various device settings and properties
reprocess pre-recorded data, e.g. with different settings
The MT Manager is therefore an easy way to get to know and to demonstrate the capabilities of the
MTi and to configure the device easily to suit your needs.
With the MT Manager, it is possible to apply a configuration profile to multiple MTi’s. This allows
system integrators to configure MTi’s fast and accurate.
Please refer to the MT Manager User Manual [MTM] for more information on this topic
Applies to: Windows PC platform

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2.6.3 Using the Software Development Kit (SDK)
This chapter gives an introduction to the Xsens Device API (XDA). It serves as a starting point for
members of a software development department interested in assessing the basis of the SDK and
knowing about the background considerations. The main objective of the SDK is to facilitate easy
development of user-specific host applications based on Xsens motion trackers.
The MT SDK 4.x (and the MT Software Suite) are designed for the MTi 10-series and MTi 100-series.
The communication protocol is the same as in previous versions of the SDK. Obviously, new
functionality has been introduced. In some functions and messages a new term is introduced to point
specifically to the MTi 10-series and MTi 100-series. This term is MkIV (or Mk4 in functions) and is an
abbreviation for Mark IV: the 4th generation MTi.
2.6.3.1 Using the Source code and Dynamic Library
The MT SDK consists of Source code and a Dynamic Library. Source code is made available in C,
since this language can be handled by many other programming languages, such as C++, Java and
Python. Since C++ is a more convenient language
to use for first-time users of the MT SDK (lower risk
of making mistakes, easier to handle complex
functions), Xsens also supplies a C++ wrapper
around the C-compiled library. Depicted on the
right is a schematic overview of the MT SDK. As
can be seen, the host application developer can
choose to use a COM, C, C# or C++ interface.
However, only the C interface is delivered as a
compiled dynamic library. For the C# and C++
interface the source code of the wrapper classes
are supplied as part of the SDK. The interfaces are
discussed in more detail in the following sections.
Note that conceptually XDA makes no distinction
between the cases that the data source is real-time
data stream from a device or if it is a recorded file
data stream.
Using the Xsens XBus low-level communication
protocol is discussed in section 2.6.4.
Device management and global control functions
are grouped in the XsControl object. To access
functionality for a specific device the XsDevice
object is available. Typical steps are:
1. Enter a serial key with XsControl::setSerialKey
2. Scan for Xsens devices with XsScanner::scanPorts
3. Open port with XsControl::openPort and get device object with XsControl::device
4. Configure device with XsDevice functions
5. Start measuring
Figure 1: Xsens Device API

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C-interface libraries
XDA is implemented in two C-interface libraries that are supplied for MS Windows and Linux,
consisting of two parts:
XDA that contains the access to functionality as implemented in devices, e.g. configuring the
Motion Trackers, requesting data etc (–Linux only available as beta via [e-mail])
XsTypes that contains generic types (vectors, matrices, quaternions, etc.) and some basic
operations on those types, e.g. converting quaternions coming from the MTi into Euler angles.
The C API exposes all possible functions that could be supported by an Xsens device. As such, a
certain functionality implemented in devices is accessible by a function call that takes at least an
XsDevice Object as a parameter. Not every Xsens device supports all functionality, e.g. an MTi does
not support getting a position estimate whereas the MTi-G does. This means that whether the function
returns a meaningful result depends on the connected device. The DeviceID indicates the MTi product
with associated functionality: a list of DeviceIDs can be found in section 2.2.5. Exposing all the
possible functionalities has the advantage that when changing the MTi in the application to a device
with other functionalities, the majority of the code can remain unchanged.
Internally the Xsens host software is implemented using an object oriented approach in which the
functionality is only implemented in subclasses, see schematic below.
It is important for the developer to use only functions supported by the connected device. During run
time, calling an unsupported function will generate an error status in line with the normal error handling
framework.
C++ interface
To offer the convenience of object-lifetime management to developers, the XDA is also offered as a
C++ interface which basically implements a convenience wrapper around the C API. This means that
the developer does not have to deal with memory management (i.e. easy object-lifetime management)
as the class implementation takes care of this. This means that for example functions named
XsDevice_<function name> in the C interface are available in the C++ interface as the
<function name> method of the XsDevice class.
COM interface
For MS Windows environments, all the functionality is also available via a COM interface.
Figure 2: Functionality implementation for specific products

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2.6.4 Direct low-level communication with MTi
The MTi features a powerful embedded multi-processor core. Since the MTi has an on-board non-
volatile memory that can store all settings, the MTi can conveniently be used without using a host
computer.
The low-level communication protocol (named XBus protocol) offers full control and functionality,
however without the convenience advantages that the Xsens Device API offers, such as threading,
object-oriented programming and error handling. Low-level communication is essential on platforms
that do not support the Xsens Device API, such as custom embedded computers.
The low-level communication is extensively described in the Low-Level Communication Protocol
Documentation. Next to that, source code is delivered to make driver development and Xbus message
parsing for the MTi as easy and quick as possible.
2.6.5 Migration from MT SDK 3.3 (CMT)
Programmers familiar with using the CMT interface from the MT SDK 3.x and lower (Xsens’ interface
for legacy MTi products) will find that changes need to be made in order to work with the new XDA.
Notable differences are shown below:
MT SDK 3.3 / CMT 3.3
MT SDK 4 / XDA 4.x
Xsens CMT (Communication for
Motion Trackers) library
XDA (Xsens Device API) library
Mixed C/C++ interface
Pure C interface with C++ wrapper interface. The C interface
supplies the same functionality as the C++ interface but uses
the class name as a function prefix (ie XsControl_openPort
instead of XsControl::openPort)
Preallocation of buffers is often
required
XDA-managed safe interface objects are passed between the
library and the application
Library functions are plain functions
using an instance number and
DeviceID for device identification
Library functions and structures are available as C++ classes
without the need for explicit identification per function
Only supports MT9-C and Xbus
Master devices
Supports all Xsens devices
Data output in fixed-rate all-in-one
format
Data output rates configurable per type of output. Also many
more output types are available.
All functions are prefixed with cmt
All structs are prefixed with Cmt
All global functions and objects are prefixed with Xs.
Source code is available including
logging and custom functions
Source code is limited to a message interface. However,
fewer messages are required to configure MTis and data
messages are easier to understand so the message interface
is more robust.
Linux functions in source code only
A shared object for Linux on x86 processors is available (beta)
XDA can be run side-by-side with CMT, but the libraries don’t interact. A full conversion to XDA is
recommended. The following coding steps are needed: replace all Cmt objects in the code by their Xs
counterparts and replace DeviceID storage by XsDevice storage and use XsDevice class functions
instead of global CMT-functions. In section 2.6.3.1, the typical workflow of XDA is explained. Also refer
to examples, to be found in the Xsens folder in Program Files of your computer.

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MTi 10-series and MTi 100-series devices are designed to be drop-in replaceable with legacy MTi and
MTx devices. When new MTi’s are configured to output orientation data in legacy output mode, CMT
will recognize the device. In this case only basic functionality is available, such as the reading of
orientation data. See section 4.10 for more information about the legacy output mode.
2.6.6 Terms of use MT Software Suite
The installer of the MT Software Suite can install 4 components of the MT Software Suite: the MT
Manager, the MT SDK, the MT Magnetic Field Mapper and the MT Firmware Updater. It is possible to
install only parts of the MT Software Suite, so every component has a separate EULA or Software
License Agreement that you need to read and accept. In the following table, the guidelines for use of
each component are described.
Component
EULA/SLA
Guidelines
MT Manager
EULA
For use with Xsens products only
Not allowed to re-distribute
Not allowed to reverse engineer
Not allowed to modify
Serial key required
MT SDK
SLA
For use with Xsens products only
Allowed to re-distribute “as is” or embed in programs
Not allowed to reverse engineer
Allowed to modify and extend source code; not allowed to modify DLL
Serial key required for use of DLL; not needed for source code
Include Software License Agreement with distribution
MT MFM
SLA
For use with Xsens products only
Allowed to re-distribute “as is”
Not allowed to reverse engineer
Not allowed to modify
No serial key required
Include Software License Agreement with distribution
MT FWU
SLA
For use with Xsens products only
Allowed to re-distribute “as is”
Not allowed to reverse engineer
Not allowed to modify
No serial key required
Include Software License Agreement with distribution

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3 MTi System Overview
3.1 Calibration
A correct calibration of the sensor components inside the MTi is essential for an accurate output.
Because of the importance of the calibration, each Xsens’ MTi is calibrated and tested by subjecting
each product to a wide range of motions and temperatures.
The MTi 10-series and the MTi 100-series feature different gyroscopes and a different sensor fusion
algorithm. Therefore, the high-performance MTi 100-series require a more elaborate calibration
method.
The individual calibration parameters are used to convert the sensor component readout (digitized
voltages) to physical quantities as accurately as possible, compensating for a wide range of
deterministic errors. Additionally, the calibration values are used in both Xsens sensor fusion
algorithms, as discussed below.
3.2 Xsens Kalman Filter (XKF3i) for MTi 10-series
The orientation of the MTi 10-series is computed by Xsens Kalman Filter. XKF3i uses signals of the
rate gyroscopes, accelerometers and magnetometers to compute a statistical optimal 3D orientation
estimate of high accuracy with no drift for both static and dynamic movements. XKF3 is a proven
sensor fusion algorithm, which can be found in various products from Xsens and partner products.
The design of the XKF3i algorithm can be summarized as a sensor fusion algorithm where the
measurement of gravity (by the 3D accelerometers) and Earth magnetic north (by the 3D
magnetometers) compensate for otherwise slowly, but unlimited, increasing (drift) errors from the
integration of rate of turn data (angular velocity from the rate gyros). This type of drift compensation is
often called attitude and heading referencing and such a system is referred to as an Attitude and
Heading Reference System (AHRS).
3.2.1 Using the acceleration of gravity to stabilize inclination (roll/pitch)
XKF3i stabilizes the inclination (i.e. roll and pitch combined) using the accelerometer signals. An
accelerometer measures gravitational acceleration plus acceleration due to the movement of the
object with respect to its surroundings.
XKF3i uses the assumption that on average the acceleration due to the movement is zero. Using this
assumption, the direction of the gravity can be observed and used to stabilize the attitude. The
orientation of the MTi in the gravity field is accounted for so that centripetal accelerations or
asymmetrical movements cannot cause a degraded orientation estimate performance. This
assumption is surprisingly powerful, almost all moving objects undergo accelerations if they are
moving, but in most cases the average acceleration with respect to the environment during some
period of time is zero. The key here is the amount of time over which the acceleration must be
averaged for the assumption to hold. During this time, the rate gyroscopes must be able to track the
orientation to a high degree of accuracy. In practice, this limits the amount of time over which the
assumption holds true. For the class of miniature MEMS rate gyroscopes used in the MTi-10 series
this period of time is about 10-20 seconds maximum.
However, for some applications this assumption does not hold. For example an accelerating
automobile may generate significant accelerations for time periods lasting longer than the maximum
duration the MT’s rate gyroscopes can reliably keep track of the orientation. This will degrade the
accuracy of the orientation estimates with XKF3i somewhat, because the application does not match