This manual gives an overview of the 5th generation products and their usage. For previous generations, refer to User Manual revision I (20 December 2016). Refer to the section #Identifying device functionality to identify the generation of your MTi. The MTi product portfolio from Xsens currently has 11 family members ranging in functionality from inertial measurement units (IMU’s) to a fully integrated GNSS/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 into three series; the MTi 1-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 new class of MEMS IMUs, orientation and position sensor modules offering unprecedented accuracy and a wide array of IO interfaces. The MTi 1-series is a low-cost module for SMD assembly. Refer to the MTi 1-series Datasheet for more information on the MTi 1-series.
All MTi’s have a powerful multi-processor core. It processes IMU, magnetometer and barometer signals with extremely low latencies, and gives several outputs: calibrated 3D linear acceleration, rate of turn (gyroscope data), (earth) magnetic field and atmospheric pressure (100-series only) data along with sensor fusion estimates of roll, pitch and yaw. The MTi-G-710 GNSS/INS also offers 3D position and 3D velocity. Over 50 different output formats can be retrieved directly from the MTi. Refer to the Low-Level Communication Protocol Document for more information on the available outputs per device.
This documentation describes the use, basic communication interfaces and specifications of all the 7 MTi’s in the MTi 10-series and MTi 100-series. Where they differ is clearly indicated. All products are designed to be interchangeable from a mechanical and software interface point of view.
The MTi 10-series is the basic product range of the MTi product portfolio, offering inertial 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/AHT and MTi-30 AHRS devices, other than their label marking.
The MTi-30 AHRS is a full gyro-enhanced Attitude and Heading Reference System (AHRS). It gives various outputs: drift-free roll, pitch and true/magnetic north referenced yaw, plus sensor measurements: 3D acceleration, 3D rate of turn and 3D earth-magnetic field data. All products of the MTi 10-series can also give processed data output from the strapdown integration algorithm (orientation and velocity increments ∆q and ∆v).
The MTi-20 VRU/AHT is a 3D vertical reference unit (VRU) / Active Heading Tracker (AHT), which means that it gives the same data as the MTi-30, except for the referenced yaw. The yaw is unreferenced, though still superior to just gyroscope integration, when using the gyro bias estimation techniques available.
The MTi-10 IMU is a 3D inertial measurement unit (IMU) that gives 3D acceleration, 3D rate of turn and 3D earth-magnetic field data, so it does not process data to orientation. The MTi-10-IMU can be set to a data output generated by the strapdown integration algorithm (orientation increments ∆q and velocity increments ∆v).
MTi 100-series including the MTi-G-710
The MTi-100 series is the high-performance product range of the MTi product portfolio, with accuracies surpassing 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 accurate, repeatable and robust.
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 proper functioning of the barometer. Note that the electronics inside are protected by a vent that keeps the casing IP67 rated. There are no visual differences between the MTi-100 IMU, MTi-200 VRU/AHT and MTi-300 AHRS, other than their label markings. The MTi-G-710 has an extra SMA connector to allow a GPS/GNSS antenna to be attached.
The flagship of the MTi product portfolio is the MTi-G-710 GNSS/INS, a fully integrated solution that includes an onboard GNSS receiver (GPS, GLONASS, BeiDou, Galileo and QZSS). The MTi-G-710-GNSS/INS can thus not only give GNSS-enhanced 3D orientation output; it also gives AHRS-augmented 3D position and velocity outputs. Furthermore, it provides 3D sensor data, such as acceleration, rate of turn, magnetic field, the PVT (position, velocity, time) data of the GNSS receiver and static pressure. Data generated by the strapdown integration algorithm (orientation and velocity increments ∆q and ∆v) are available, along with other processed data, at 400 Hz.
The MTi-300 AHRS is a full gyro-enhanced Attitude and Heading Reference System (AHRS). It gives drift-free roll, pitch and true/magnetic north-referenced yaw outputs. It also delivers sensor data and processed data from the strapdown integration algorithm as described in the previous section.
The MTi-200 VRU/AHT is a 3D vertical reference unit (VRU) / Active Heading Tracker (AHT) and this unit runs the Xsens sensor fusion algorithm from the MTi-300 as well. 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 when using the gyro bias estimation techniques available. The MTi-200 also comes with Active Heading Stabilization.
The MTi-100 IMU is a 3D inertial measurement unit (IMU) that gives 3D acceleration, 3D rate of turn and 3D earth-magnetic field data. The MTi-100-IMU can also be configured so that it gives data generated by the strapdown integration algorithm (orientation increments ∆q and velocity increments ∆v).
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.
The 4th generation MTi’s can be identified by the last four digits of the DeviceID (or SerialNumber). If the last four digits are lower than hexadecimal 2000, they are the 4th generation MTi’s, otherwise they belong to the 5th generation of MTi devices. Refer to version MTi User Manual rev I (20 Dec 2016) when you have an MTi with one of these DeviceIDs
Below is a list of the product types with their associated DeviceIDs.
Device ID's for 5th generation MTi
|
Product (MTi Mk5) |
RS232+USB |
RS422 |
RS485+USB |
|
MTi-10 IMU |
0168xxxx |
0169xxxx |
016Bxxxx |
|
MTi-20 VRU/AHT |
0268xxxx |
0269xxxx |
026Bxxxx |
|
MTi-30 AHRS |
0368xxxx |
0369xxxx |
036Bxxxx |
|
MTi-100 IMU |
0178xxxx |
0179xxxx |
017Bxxxx |
|
MTi-200 VRU/AHT |
0278xxxx |
0279xxxx |
027Bxxxx |
|
MTi-300 AHRS |
0378xxxx |
0379xxxx |
037Bxxxx |
|
MTi-G-710 GNSS/INS |
0778xxxx |
0779xxxx |
077Bxxxx |
The product code of the MTi Mk5 consists of a number of characters that represent the product type, the full range of the inertial sensors, the interface and the casing option. The figure below shows the product code build-up, e.g. MTi-10-4A8G4 is an IMU with RS485 interface, 20g full range on the accelerometers and 450 deg/s full range for the gyroscopes.
Note that not every combination is available.
Example of a label showing the SN (DeviceID) and the product code
The MTi 10-series and MTi 100-series are described in detail in sections #MTi 10-series and #MTi 100-series, for completeness, they are listed below as well.
|
Product name |
Description |
Availability |
Product photo |
|
MTi 10-series, MTi 100-series (including MTi-G-700/710) and OEM |
The 4th generation Motion Trackers of Xsens (MkIV). |
Introduced: 2012
Status: Inactive |
|
|
MTi 1-series |
The MTi 1-series is a full range module (IMU, VRU/AHT, AHRS and GNSS/INS) in a miniature SMD form factor. The MTi 1-series is not described in this manual. For MTi 1-series documentation, see MTi 1-series. |
Introduced: 2015
Status: Active |
|
|
MTi 10-series, MTi 100-series (including MTi-G-710) and OEM |
The new 5th generation of the MTi series. The product will replace the 4th generation MTi and has significantly higher specifications in e.g. acceleration and MTBF. |
Introduced: 2017
Status: Active |
|
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 and cable. All software and installation instructions are available online.
The full content of the MTi DK is described below.
NOTE: the most recent version of the software, source code and documentation can always be downloaded at www.xsens.com/software-downloads.
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 can mitigate these effects to a certain extent, but nonetheless, it is impossible to estimate the true vertical without additional 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 close to the centre of rotation (CR) of the vehicle/craft. Any rotations around the centre of rotation translate into centripetal accelerations at any point outside the center of rotation. For the MTi-G-710 with a valid GNSS-fix, the detrimental effect of transient accelerations on orientation estimates is overcome by integrating with GNSS measurements in the sensor fusion engine.
The MTi 100-series copes 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.
The MTi samples IMU signals at 10kHz per channel, processing them using a strapdown integration algorithm with coning/sculling compensation. Proper coning/sculling compensation already mitigates errors that poorly designed signal processing pipelines introduce when the device is under vibration. For best results, however, it is recommended that the MTi be 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;
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 mechanical vibration rejecting gyroscopes, designed to better cope with these specific conditions.
Note that the moving part on the Fischer connector can move to enable mating and unmating of the cable with the MTi. The ring behind the moving part must be locked to prevent vibrations of the moving parts of the connector from being transferred to the casing of the MTi.
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. These vibrations had no effect with the vibration dampeners fitted. The dampeners tested are manufactured by Norelem and have part number 26102-00800855, www.norelem.com
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 the computed yaw. The earth's magnetic field is altered by the presence of ferromagnetic materials, permanent magnets or power lines with strong currents (several amperes) in the vicinity of the device. The distance to the object and the amount of ferromagnetic material determines the magnitude of disturbance introduced. Errors in estimated yaw due to such distortions can be quite large, since the earth's magnetic field is very weak in comparison to the magnitude of the sources of distortion.
For more information on how to mitigate the detrimental effects of magnetic distortion, refer to the BASE article Estimating Yaw in magnetically disturbed environments.
Xsens GNSS/INS Development/Starter Kits include a GNSS patch antenna. In contrast to other antenna types such as helix antennas, patch antennas require a ground plane underneath them to operate properly. A ground plane will reduce errors due to multipathing effects, by blocking signals that can normally reach the GNSS antenna from low or sub-horizon elevations.
Adding a ground plane is not necessary when mounting the antenna directly onto a flat metal surface, such as the roof of a car. Otherwise, we recommend mounting the antenna on top of a metal plate (thickness irrelevant) with a minimum diameter of 10 cm.
For best practices or tailor-made ground planes, we recommend contacting the original manufacturer of the used GNSS antenna. Antennas that are sold by Xsens, as well as their product code and original manufacturer, are listed in this BASE article. For Tallysman patch antennas, best practices were discussed here.
In addition to creating a proper ground plane, avoid mounting the antenna underneath or in close proximity of other metal structures and electronics in order to ensure the best GNSS signal reception.
This section is intended to help you find the right software component and corresponding documentation for the way you want to use your MTi.
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, magnetic calibration and updating of the firmware. Depicted in the figure 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 can also be used to communicate with the MTi. The MagField Mapper is also available as an SDK for integration into another application.
The MT SDK contains all the developer code, such as a DLL, a shared object and basic functionality in source code for embedded systems. Of course, it is possible to use lower level communication options, down to the Xbus Low Level protocol; most of the functionality, however, can be found in the DLL and shared object.
Structure of the MT Software Suite
The Xbus low-level protocol is described in high detail in the Low Level Communication Protocol Document.
The hardware driver of the USB interface for Linux can be found on https://github.com/xsens/xsens_mt. The driver is also included in Linux kernel 3.9 and higher.
The easiest way to get started with your MTi is to use the MT Manager software for Windows.
This easy to use software with a Windows user interface allows you to:
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 correctly with a quick turn-around time.
Please refer to the MT Manager User Manual for more information on this topic.
This chapter gives an introduction to the Xsens Device API (XDA). It serves as a starting point for system integrators 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 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. Refer to the MT SDK documentation in the Xsens installation folder to find a schematic overview of the Xsens Device API. 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++ interfaces, the source code of the wrapper classes is 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 of a real-time data stream from a device or a recorded file data stream.
Using the Xsens Xbus low-level communication protocol is discussed in the section #Direct low-level communication with the MTi.
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:
C-interface libraries
XDA is implemented in two C-interface libraries that are supplied for Windows and Linux, consisting of two parts:
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-30 does not support getting a position estimate whereas the MTi-G-710 does. This means that whether the function returns a meaningful result depends on the type of connected device. The DeviceID indicates the MTi product with associated functionality: a list of DeviceIDs can be found in Table Device ID's for 5th generation MTi. 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 the schematic below.
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Functionality implementation for specific products
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.
The MTi features a powerful embedded multi-processor core. As 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, but without the convenient 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.
The installer of the MT Software Suite can install 4 components of the MT Software Suite: the MT Manager, the MT SDK, the Magnetic Field Mapper and the MFM SDK. The Firmware Updater is a separate installer. The MT Software Suite has a Restricted License Agreement that you need to accept. In the following table, the guidelines for use of each component are described.
Guidelines for the use of the MT Software Suite
|
Component |
Guidelines |
|
MT Manager |
For use with Xsens products only Not allowed to re-distribute Not allowed to reverse engineer Not allowed to modify |
|
MT SDK |
For use with Xsens products only Allowed to re-distribute “as is” or embed in programs Not allowed to reverse engineer Allowed to execute, reproduce, modify and compile (modified) source code to use with Xsens products only Not allowed to modify DLL Include License Agreement with distribution |
|
MFM |
For use with Xsens products only Allowed to re-distribute “as is” Not allowed to reverse engineer Not allowed to modify Include License Agreement with distribution |
|
MFM SDK |
For use with Xsens products only Allowed to re-distribute “as is” or embed in programs Not allowed to reverse engineer Allowed to execute, reproduce, modify and compile (modified) source code to use with Xsens products only Not allowed to modify DLL Include License Agreement with distribution |
|
FWU |
For use with Xsens products only Allowed to re-distribute “as is” Not allowed to reverse engineer Not allowed to modify Include License Agreement with distribution |
