MTi and MTx User Manual and Technical Documentation
Contents
1. Field Field width Description Preamble 1 byte Indicator of start of packet gt 250 OxFA BID 1 byte Bus identifier address gt 255 OxFF MID 1 byte Message identifier LEN 1 byte Value equals number of bytes in DATA field Maximum value is 254 OxFE Value 255 OxFF is reserved DATA 0 254 bytes Data bytes optional Checksum 1 byte Checksum of message Preamble Every message starts with the preamble This field always contains the value 250 OxFA Bus identifier BID or Address All messages used for the MTi and MTx use the address value 255 OxFF indicating a master device Message Identifier MID This message field identifies the kind of message For a complete listing of all possible messages see MT Low level Communication Documentation Length LEN Specifies the number of data bytes in the DATA field Value 255 OxFF is reserved This means that a message has a maximum payload of 254 bytes If Length is zero no data field exists Data DATA This field contains the data bytes and it has a variable length which is specified in the Length field The interpretation of the data bytes are message specific i e depending on the MID value the meaning of the data bytes is different See the description of the specific message for more details about interpretation of the data bytes Checksum This field is used for communication error detection If all message bytes excluding the preamble are2. The calibrated data is unprocessed i e only the physical calibration model is applied to the 16 bit values retrieved from the AD converters There is no additional filtering or other temporal processing applied to the data The bandwidths of the signals are as stated in the datasheet and section 2 4 The output definition in calibrated data output mode is MD 50 acey acez ayrx gory apr magx magy magz TS MID 50 0x32 seen gyrX gyrY gyrZ magY Ts All data elements in DATA field are FLOATS 4 bytes TS time stamp optional The accelerometer rate of turn magnetometer data can be individually dis or enabled See SetOutputSettings message in section 3 3 3 NOTE The linear 3D accelerometers measure all accelerations including the acceleration due to gravity This is inherent to all accelerometers Therefore if you wish to use the 3D linear accelerations output by the MTi MTx to estimate the free acceleration ie 2 derivative of position gravity must first be subtracted 2 5 3 Un calibrated raw output mode In un calibrated raw output format the raw readings from the 16 bit AD converters in the MTi MTx are outputted This means the physical calibration model described in the previous section is not applied This gives you open access to the basic level of the sensor unit but in most cases this level of use is not recommended However if your main purpose is for 14 MTO100P G J sens
3. 3D rate of turn gyro and 3D magnetic field data all will have orthogonal XYZ readings within lt 0 1 as defined in figure 1 5 MT0100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V manon Secnnelesles 2 1 2 Orientation co ordinate system The MTi and MTx calculates the orientation between the sensor fixed co ordinate system S and a earth fixed reference co ordinate system G By default the local earth fixed reference co ordinate system used is defined as a right handed Cartesian co ordinate system with e X positive when pointing to the local magnetic North e Y according to right handed co ordinates West e Z positive when pointing up The 3D orientation output independent of output mode see chapter 3 is defined as the orientation between the body fixed co ordinate system S and the earth fixed co ordinate system G using the earth fixed co ordinate system G as the reference co ordinate system Example Z Z aE MTi MTx co y ordinate system S me co ordinate system G Local magnetic north All co ordinate systems are right handed Please refer to section 2 6 for further details on output co ordinate systems and different options to redefine the output co ordinate systems True North vs Magnetic North As defined above the output coordinate system of the MTi MTx is with respect to local Magnetic North The deviation between Magnetic North and True North known as
4. 2D mapping is suitable in applications where the object moves more or less in a single plane e g a car or boat P 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 If you degauss please make sure the MTi or MTx is not anymore on the object 45 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V mason SEENIOR Disturbance caused by objects in the environment near the MTi or MTx like file cabinets or vehicles that move independently with respect to the device cause a type of distortion that can not be calibrated for However the amount of error caused by the disturbance can be reduced using the option Adapt to magnetic disturbances in the sensor fusion filter settings in the MTi MTx 2 This type of disturbance is non deterministic 46 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V maen seems 6 Important notices 6 1 Environmental Operating Conditions The recommended operating temperature of the MTi MTx hardware is between 0 C and 55 C ambient temperature If operated outside this temperature range performance may decrease or the device might be damaged Fast transient temperature fluctuations may cause significant temperature
5. It is also possible to enter the Config State at power up see WakeUp message description in the MTi and MTx Low Level Communication Document Another way to enter the Config State or Measurement State is to use the GoToConfig or GoToMeasurement messages The default configuration of the MTi MTx is shown in the following table Output mode Orientation output Output settings Orientation in quaternion mode Sample counter Sample frequency 100 Hz Baudrate 115k2 bps Output skip factor 0 With the default configuration the MTi MTx outputs in Measurement State the MTData message at a frequency of 100Hz based on its internal clock The MTData message contains the orientation data in quaternions together with a sample counter If you want to retrieve the output data on request then set Output skip factor to value 65535 OxFFFF and send ReqMTData message to the device For more information see MTi and MTx Low Level Communication Document 3 3 Messages 3 3 1 Message structure The communication with the MTi and MTx is done by messages which are built according to a standard structure The standard MT Comm message can contain zero to 254 bytes of data and the total length is five to 259 bytes An MTComm message contains the following fields PREAMBLE BID MD LEN DATA CHECKSUM 22 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V motion Secnnelosles
6. MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V Motion Secnpelegies logging and post processing it may be advantageous as it is always possible to go back to the source of the signal In this mode the device temperature is also outputted housing ambient only NOTE The data fields are 2 bytes 16 bits as opposed to the 3 byte floats for the other output modes The output definition in un calibrated raw output mode is Pioo ot wa MID 50 0x32 GEAN Ee alu DEE Each data element in DATA field is 2 bytes 16 bit unsigned integers See below for reading the temperature data TS time stamp optional Temperature output format The 2 byte temperature data field in the un calibrated raw output mode of the MTi MTx can be interpreted as a 16 bits 2 complement number However please note that the resolution of the temperature sensor is not actually 16 bit but 12 bit For example you can interpret the 2 byte temperature as follows 00 00hex 0 0 C 00 80hex 0 5 C FF 80hex 0 5 C 19 10hex 25 0625 C E6 FOhex 25 0625 C The temperature field is a 16 bit two complement number of which the last byte represents the value behind the comma To calculate the temperature value use the formula T 2 x 256 ifx gt 2 or T x 256 if x lt 2 where x is the 16 bit value of the Temp field For example the value 59120 OxE6FO corresponds with a temperature of 25 0625 C 15 MT
7. Mapper add on PC Windows 2000 XP MT SDK documentation MT0200P MT Software documentation MT0201P MT Magnetic Field Mapper Documentation MT0202P e A letter with your individual software license code NOTE the most recent version of the software source code and documentation can always be downloaded on the support section of www xsens com this document 2 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V moon Seannelosles 1 3 Typical User Scenarios This section is intended to help you find the right documentation for the way you want to use your MTi or MTx 1 3 1 Getting Started with the MT Software The easiest way to get started with your MTi or MTx is to use the MT Software This easy to use software with familiar Windows user interface lets you view 3D orientation in real time log ASCII data files change and view various device settings and properties It is an easy way to get to know and to demonstrate the capabilities of the MTi and MTx miniature inertial measurement units Applies to Windows PC platform gt Please refer to the MT Software User Manual for more information on this topic 1 3 2 Interface through COM object API If you want to develop a software application that uses the MTi or MTx you can consider using the COM object API MTObj DLL which provides easy to use function calls to obtain data from the sensor or to change settings The COM object take
8. OF THE USE OF THE PRODUCT OR WRITTEN MATERIALS IN TERMS OF CORRECTNESS ACCURACY RELIABILITY OR OTHERWISE Xsens shall have no liability for delays or failures beyond its reasonable control 48 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V manon Seannelosles 6 5 Customer Support Xsens Technologies B V is glad to help you with any questions you may have about the MTi or MTx or about the use of the technology for your application Please contact Xsens Customer Support gt by e mail support xsens com gt telephone 31 0 534836444 To be able to help you please mention your Motion Tracker Device ID on the back of the device and software license registration number in your e mail 49 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V motion Secnpelegies this page is intentionally left blank 50 MTO100P G
9. SETTINGS bits Settings Bit 1 0 Timestamp output 00 No timestamp 01 Sample Counter Bit 3 2 Orientation Mode 00 Quaternion 01 Euler angles 10 Matrix Bit 6 4 Calibration Mode Bit 4 0 Enable acceleration XYZ output 1 Disable acceleration XYZ output Bit 5 0 Enable rate of turn XYZ output 1 Disable rate of turn XYZ output Bit 6 0 Enable magnetometer XYZ output 1 Disable magnetometer XYZ output Bit 7 Reserved Bit 9 8 Output Format 00 Float output 01 Fixed point Signed 12 20 format GoToMeasurement MID 16 0x10 Data field n a Direction To MTi MTx Valid in Config State Switches the active state of the device from Config State to Measurement State The current configuration settings are used to start the measurement MTData MID 50 0x32 Data field DATA length variable Direction From MTi MTx Valid in Measurement State Contains the output data depending on the current Output Mode amp Output settings The data field can contain multiple data outputs but the order of outputs is always the same The following order is used disabled outputs must be omitted 1 Un calibrated raw data output 2 Calibrated data output 3 Orientation data output 4 Sample counter Un calibrated raw data output can not be used together with calibrated and or orientation data output The following text explains the data values of each output 26 MTO100P G sons MTi and MTx User Manual and Tech Doc 2
10. Value Output high voltage 3 0 3 3V Output low voltage 0 0V Minimum ohmic value of load 100 kOhm Latency offset 0 1 lus Latency offset gt 0 5 4us Jitter 40ns Supported by MTi RS 232 MTi 28A G 40 MTO100P G e SMsane MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V matin Secnpoelogies 4 5 Housing mechanical specifications The plastic parts of the housing are made of polyamide PA6 6 The MTi bottom plate is made of anodized aluminum 6082 The housing is dust proof but not water proof The MTi connector socket and housing assembly features rubber o ring sealing and is generally more robust to harsh environments than the MTx 4 MTO100P G sens MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V malen sechnolagies 4 5 1 Dimensions MTi 50 6 0 2 42 9 0 2 3 85 20 2 2x Li 0 2 2x Bs reproduction reserves tous droits de 29 35 0 20 34 4 CONNECTOR TYPE ODU GL OL 57 9 0 3 040 2x Eo D 2 Ee 29 og 50 4 0 3 37 8 N I N 7 7 alle Rechte vorbehalten alle rechten voorbehouden Date American 1 1 JB 2005 04 07 KA projection Ad Yoong Product code DIMS motion technologies MTi _ A G__
11. any potential difference between de measurement device ground and the signal ground appears as a common mode signal at both the positive and negative inputs of the amplifier and this difference is rejected by the amplifier If a hardware filter is not preferred it is also possible to use digital filtering Make sure that the sample frequency is set high enough to minimise the aliasing effects A minimum sample frequency of 40kHz is recommended 20 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V maen seems 3 Basic communication 3 1 Introduction This section describes the basics of how to communicate with the MTi MTx directly on low level using RS 232 422 485 serial communication with or without the use of an Xsens USB serial converter For detailed and a complete list of all messages please refer to the MT Low level Communication Documentation NOTE You can skip this chapter you plan to only interface with the device using Xsens GUI software or SDK API The communication protocol which is message based enables the user to change the configuration of the MTi or MTx and to retrieve the data from the device The communication protocol used for the MTi and MTx is compliant to the MotionTracker communication protocol The configuration is fully user settable e g sample frequency in amp output synchronization baudrate and data output modes can all be changed to fit your requirem
12. definitions MTi plug socket and wire color Signal ODU pin Wire color VCC Pin 1 Yellow GND Pin 2 Yellow green Analog output 1 Pin 3 Black TX sensor Pin 4 Beige RX sensor Pin 5 Brown Analog output 2 Pin 6 Green Analog output 3 Pin 7 Blue 36 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V manon SEERA 4 4 5 Pin and wire color definitions MTx 28A G MTx RS 232 standard version MTx housing socket Binder female 719 socket receptacle back view solder bucket view ridge on upper side MTx USB serial cable plug CA USB2x Binder 719 male connector back view solder bucket view Ridge on upper side Pin definitions MTx plug socket and wire color Signal Binder pin Wire color VCC Pin 2 Black GND Pin 4 Yellow green TX sensor Pin 1 Beige RX sensor Pin 5 Brown SyncIn Pin 3 Blue 37 MT0100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V manon SEERNES 4 4 6 Pin and wire color definitions MTx 48A G MTx RS 485 standalone MTx housing socket Binder female 719 socket receptacle back view solder bucket view ridge on upper side MCM SNS GO Ee NOF 2 83 MTx USB serial cable plug CA USB4x Binder 719 male connector back view solder bucket view Ridge on upper side Pin definitions MTx plug socket and wire color Sign
13. frame After this the orientation output will be with respect to the newly defined global axes 16 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V manon Secnnelesles NOTE 1 After a global reset the vertical will generally not be along the Z axis 2 A change of global earth fixed reference system does not have any effect of the calibrated sensor output since the calibrated sensor output is expressed with respect to the S coordinate frame 3 The orientation of the new global reference frame with respect to the earth fixed frame described in section 2 1 can not be stored in the MTi or MTx non volatile memory 2 6 4 Object reset The object reset function aims to facilitate in aligning the MTi MTx coordinate frame S with the coordinate frame of the object the sensor is strapped to O After an object reset the S coordinate frame is changed to S as follows e the S Z axis is the vertical up at time of reset e the S X axis equals the S X axis but projected on the new horizontal plane e the S Y axis is chosen as to obtain a right handed coordinate frame NOTE Once this object reset is conducted both calibrated data and orientation will be output in the new coordinate frame e The object reset can be used to set the MTi MTx coordinate frame to that of the object to which it is strapped see figure below The sensor has to be strapped such that the X axis is
14. gradients across the device Such gradients cannot be properly modelled by temperature compensation and may therefore decrease performance For optimal performance the ambient temperature should remain constant as much as possible during the measurement NOTE Never expose the MTi or the MTx to strong magnetic fields The MTi and MTx contains the absolute possible minimum of ferromagnetic materials hard and soft magnetic materials Nonetheless some minor components can be magnetized permanently by exposure to strong magnetic fields This will not damage the unit but will render the calibration of the magnetometers useless typically observed as a large deviation in heading For mild magnetization it may be possible to compensate for the magnetization of the device by a re calibration magnetic field mapping Taking care not to expose the MTi or the MTx to strong magnetic fields such as close proximity of permanent magnets speakers electromotor etc will make sure magnetization does not occur The MTi and MTx hardware must be kept dry at all times Condense may damage the internal electronics The MTi and MTx hardware should be protected from electro static discharges or sources of radiation as exposure to such source will damage the internal electronics The MTi and MTx hardware should be protected from violent handling such as drops on hard surfaces Excessive shocks or violent handling may damage the motion sensors The M
15. in the global reference system NOTE Once this alignment reset is conducted both calibrated data and orientation will be output with respect to the new S coordinate frame 2 7 Timestamp output Timestamp output can be enabled or disabled using the SetOutputSettings message The timestamp is always last in the data field of the MTData message Currently there is one option for the timestamp output the sample counter which is a 16 bit counter increasing with 1 with each MTData message sent After reaching 216 1 65535 the sample counter will wrap to zero 0 2 8 Analog outputs Besides sending the orientation information digitally the MTi with analog outputs has three pins of which the voltages correspond to the calculated Euler angles Please note that for the highest accuracy the digital interface should be used The analog outputs correspond with the roll pitch and yaw angles of the device only if the orientation mode and the analog outputs are enabled see SetOutputMode and SetExtOutputMode messages This is the default factory setting For the pinout specification of this version see section 4 4 for the pinout of this version 2 8 1 Conversion to Euler angles The voltage levels of the analog outputs 1 2 and 3 correspond to the roll pitch and yaw angle respectively To convert the measured voltage into the angle value use the following formula Angle gain measured voltage V offset The gain and off
16. is a registered trademark of Xsens Technologies B V MTi and MTx are trademarks of Xsens Technologies B V il MTO100P G MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V Table of Contents 1 INTRODUCTION 1 1 PRODUCT DESCRIPTION 1 1 1 MTi miniature gyro enhanced Attitude and Heading Reference Sensor 1 12 MTx miniature inertial 3DOF Orientation Tracker 1 2 OVERVIEW MTI AND MTX DEVELOPMENT KIT 1 2 1 Contents 1 3 TYPICAL USER SCENARIOS 1 3 1 Getting Started with the MT Software 1 3 2 Interface through COM object API 1 3 3 Direct low level communication with MTi or MTx 1 4 SENSOR FUSION 2 OUTPUT SPECIFICATION 2 1 CO ORDINATE SYSTEMS 2 1 1 Calibrated Sensor readings 2 1 2 Orientation co ordinate system 2 2 ORIENTATION PERFORMANCE SPECIFICATION 2 2 1 Sensor fusion algorithm settings 2 3 ORIENTATION OUTPUT MODES 2 3 1 Quaternion orientation output mode 2 3 2 Euler angles orientation output mode 2 3 3 Rotation Matrix orientation output mode 24 CALIBRATED DATA PERFORMANCE SPECIFICATION 2 5 CALIBRATED DATA OUTPUT MODE 2 5 1 Physical sensor model 2 5 2 Calibrated inertial and magnetic data output mode 2 5 3 Un calibrated raw output mode 2 6 RESET OF OUTPUT OR REFERENCE CO ORDINATE SYSTEMS 2 6 1 Output with respect to non default coordinate frames 2 6 2 Heading reset 2 6 3 _ Global reset 2 6 4 Object reset 2 6 5 Alignment reset 2 7 TIMESTAMP OUTPUT 2 8 ANALOG OUTPUTS 2 8 1 Conversion to Euler angle
17. mm r c Xsens Technologies B V 2005 all rights reserved Fa Drawn Chec 42 MT0100P G sens MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V malen sechnologies 4 5 2 Dimensions MTx 8 S 35 N E 8 58 38 i CONNECTORS 7 TYPE BINDER 719 53 09 9766 20 04 Tt Oo i S 5 N pal 6J O elg Ii y o N c 1 lt A 3 s 10 4 0 8 58 6 i N 53 88 28 Scale Drawn Chec Date American R 1 1 JB 2005 04 08 KA projection A4 Sans fresas pn motion technologies MTx A G mm c Xsens Technologies B V 2005 all rights reserved 43 MT0100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V NEE EEE 5 Operating Guidelines 5 1 Normal operating procedure NOTE Please also refer to the Quick Setup Sheet that came in your Development Kit package Power on the device Optional check the device is using the settings you need Allow electronics to warm up for about 15 minutes for optimal performance Start measurements Stop measurements Power off device ON ee a Remarks 1 Unlike previous generation devices MT9 A MT9 B the MTi and MTx can start tracking accurately while moving rotating in default setting If possible this should be avoided and tracking Start should be done in s
18. one qo The inverse qsg is defined by the complex conjugate of qas The complex conjugate is easily calculated dhs qo qi 42 q3 qsa As defined here gas rotates a vector in the sensor co ordinate system S to the global reference co ordinate system G XG gesxsqbhs JGSXSISG Hence qsg rotates a vector in the global reference co ordinate system G to the sensor co ordinate system S where gs is the complex conjugate of qas The output definition in quaternion output mode is MID 50 0x32 All data elements in DATA field are FLOATS 4 bytes TS time stamp optional 9 MTO100P G e SMsane MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V motion Secnpelogies 2 3 2 Euler angles orientation output mode The definition used for Euler angles here is equivalent to roll pitch yaw heading also known as Cardan The Euler angles are of XYZ Earth fixed type subsequent rotation around global X Y and Z axis also known as aerospace sequence e o roll rotation around Xa defined from 180 180 e 0 pitch rotation around Yg defined from 90 90 e y yaw rotation around Zo defined from 180 180 NOTE Due to the definition of Euler angles there is a mathematical singularity when the sensor fixed X axis is pointing up or down in the earth fixed reference frame i e pitch approaches 90 This singularity is in no way present in the q
19. output mode NOTE This section is intended to give detailed information on the definition of the calibrated inertial data output modes of the MTi and MTx The output sequence of the elements of the vectors defined here holds for all interface levels RS 232 422 API GUI For more detailed information about the respective interfaces please refer to their specific documentation Direct gt MTi and MTx Low level communication Documentation API gt MT Software Development Kit Documentation GUI gt MT Software 2 5 1 Physical sensor model This section explains the basics of the individual calibration parameters of each MTi and MTx This explains the values found on the MT Test and Calibration Certificate that comes with each MTi and MTx The physical sensors inside the MTi and MTx accelerometers gyroscopes and magnetometers are all calibrated according to a physical model of the response of the sensors to various physical quantities e g temperature The basic model is linear and according to the following relation s K u b The model really used is more complicated and is continuously being developed further From factory calibration each MTi MTx has been assigned a unique gain matrix Kr and the bias vector br This calibration data is used to relate the sampled digital voltages u unsigned integers from the 16 bit ADC s from the sensors to the respective physical quantity s The gain matrix is split into a misalignment ma
20. 006 Xsens Technologies B V nOD SEERNES DATA The data can contain multiple outputs All the different outputs are described separately here If not specified otherwise each data value is 4 bytes long and corresponds with the single precision floating point value as defined in the IEEE 754 standard float Un calibrated raw data output mode 20 bytes Contains the un calibrated raw data output of the accelerations rate of turn and magnetic field in X Y amp Z axes These values are equal to the analog digital converter readings of the internal sensors The data values are NOT float values but 16 bit unsigned integer values Calibrated data output mode 36 bytes Contains the calibrated data output of the accelerations rate of turn and magnetic field in X Y amp Z axes in floats allee Orientation data output mode quaternion 16 bytes Contains the q0 q1 q2 and q3 quaternions in floats that represent the orientation of the MTi MTx Orientation data output mode Euler angles 12 bytes Contains the three Euler angles in floats that represent the orientation of the MTi MTx Orientation data output mode Matrix 36 bytes Contains the rotation matrix DCM in floats that represents the orientation of the MTi MTx See chapter 2 3 3 for the interpretation of the data values Sample counter 2 bytes The optional sample counter is a 16 bit unsigned integer value that is increased for each transmission
21. 0100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V manon Secnnelosles 2 6 Reset of output or reference co ordinate systems 2 6 1 Output with respect to non default coordinate frames In some situations it may occur that the sensor axes are not exactly aligned with the axes of the object of which the orientation has to be recorded It may be desired to output the orientation and or calibrated inertial data in an object fixed frame as opposed to an sensor fixed frame Four features have been added to the software to facilitate in obtaining the output in the desired coordinate frames 1 A heading reset that redefines the X axis of the global coordinate frame while maintaining the Z axis along the vertical After the heading reset the orientation will be expressed with respect to the new global earth fixed reference frame 2 A global reset that permits the user to use the MTI MTx to define all the axes of the global coordinate frame including Z axis up down 3 An object reset that defines how the sensor it oriented with respect to the coordinate axes to which it is attached After the object reset both the orientation and the calibrated sensor data are expressed with respect to the axes of the object 4 A combined object heading reset referred to as alignment NOTE For all co ordinate system reset functions it is important to remember that the housing of the MTx can not be considered an accu
22. 2 Yellow green Analog IN Pin 3 Black TX sensor Pin 4 Beige RX sensor Pin 5 Brown SyncOut Pin 6 Green SyncIn Pin 7 Blue 34 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V motion Seannelesles 4 4 3 Pin and wire color definitions MTi 68A G MTi RS 422 MTi housing socket ODU L series 7 pin female socket receptacle back view solder bucket view ODU product code GLOLOC TO07LCC0 000 MTi USB serial cable plug CA USB6 ODU L series 7 pin male connector plug back view solder bucket view solder contact for AWG 28 wire ODU product code S10LOC TO7MCC0 5200 Pin definitions MTi plug socket and wire color Signal ODU pin Wire color VCC Pin 1 Yellow GND Pin 2 Yellow green TX Al sensor Pin 3 Black TX B1 sensor Pin 4 Beige RX A2 sensor Pin 5 Brown RX B2 sensor Pin 6 Green SyncIn Pin 7 Blue 35 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V TOS SEERA 4 4 4 Pin and wire color definitions MTi 28A G D MTi RS 232 analog outputs MTi housing socket ODU L series 7 pin female socket receptacle back view solder bucket view ODU product code GLOLOC TO07LCC0 000 MTi USB serial cable plug CA USB2 ODU L series 7 pin male connector plug back view solder bucket view solder contact for AWG 28 wire ODU product code S10LOC TO7MCC0 5200 Pin
23. MTi and MTx User Manual and Technical Documentation as Document MT0100P Revision G March 2 2006 Xsens Technologies B V Capitool 50 phone 31 0 53 4836444 4 SG NIS P O Box 545 fax 31 0 53 4836445 7500 AM Enschede e mail support xsens com motion technologies The Netherlands internet www xsens com sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V manon Seannelosles Revisions Revision Date By Changes A June 1 2005 PS First version B June 3 2005 PS Minor editorial changes def Ras in Euler on section 2 3 3 corrected C August 8 2005 SS Added pin definitions for MTi RS 422 version Added wire color definitions for USB CA Added specification of SyncIn SyncOut and Analog In Added explanations on sensor fusion algorithm settings September 8 2005 SS Added specification amp pinout of MTi analog outputs version December 2 2005 RG Added pin definitions for MTx RS 485 standalone version Added pin definitions for MTx Xbus version Corrected product code ODU connector January 30 2006 PS SS Update specs in section 2 4 Added pin definitions of USB converter March 2 2006 SS Changed name Xbus class to MTComm Added 5g option accelerometer in section 2 4 2005 2006 Xsens Technologies B V All rights reserved Information in this document is subject to change without notice Xsens
24. O100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V manon SSES gt Please refer to the MTi and MTx Low level communication protocol documentation and the MT Software Development Kit Documentation for more information on this topic 1 4 Sensor fusion The MTi MTx s low power DSP runs a proprietary sensor fusion algorithm developed in house by Xsens tailor made to the MTi and MTx that can accurately calculate absolute orientation in three dimensional space from miniature rate of turn sensors gyroscopes accelerometers and magnetometers in real time 3D gyroscopes 3D accelero meters 3D driftless orientation Sensor Fusion Algorithm The design of the algorithm can be explained as a sensor fusion algorithm where the measurement of gravity accelerometers and magnetic north magnetometers compensate for otherwise unlimited increasing drift errors from the integration of rate of turn data This type of drift compensation is often called attitude and heading referenced and such a system is often called an Attitude and Heading Reference System AHRS 4 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V motion secnpoelegies 2 Output Specification In this chapter the various output modes of the MTi and MTx are described The two major modes Orientation output and Calibrated data output are discussed separately Howeve
25. Products not subjected to misuse will be repaired replaced or credit issued at the sole option of Xsens Technologies B V Contact support xsens com for return material authorization RMA prior to returning any items for calibration repair or exchange The product must be returned in its original packaging to prevent damage during shipping The warranty shall not apply to products repaired or altered or removed from the original casing by others than Xsens Technologies B V so as in Xsens Technologies B V opinion to have adversely affected the product products subjected to negligence accidents or damaged by circumstances beyond Xsens Technologies B V s control NOTE Xsens reserves the right to make changes in its products in order to improve design performance or reliability Subject to the conditions and limitations on liability stated herein Xsens warrants that the Product as so delivered shall materially conform to Xsens then current specifications for the Product for a period of one year from the date of delivery ANY LIABILITY OF XSENS WITH RESPECT TO THE SYSTEM OR THE PERFORMANCE THEREOF UNDER ANY WARRANTY NEGLIGENCE STRICT LIABILITY OR OTHER THEORY WILL BE LIMITED EXCLUSIVELY TO PRODUCT REPAIR REPLACEMENT OR IF REPLACEMENT IS INADEQUATE AS A REMEDY OR IN XSENS OPINION IMPRACTICAL TO REFUND THE PRICE PAID FOR THE PRODUCT XSENS DOES NOT WARRANT GUARANTEE OR MAKE ANY REPRESENTATIONS REGARDING THE USE OR THE RESULTS
26. Ti and MTx hardware should be protected from strong vibrations Excessive and continuous vibration may damage the device Please contact support xsens com for more detailed information 6 2 Absolute maximum ratings Stresses above Absolute Maximum Ratings may cause permanent damage to the device Shock any axis 20000 m s 2000 g unpowered powered Max Voltage 0 3 V 16 V Operating Storage Temperature 5 C 60 C NOTE Drops onto hard surfaces can cause shocks of greater than 20000 m s 2000 g exceed the absolute maximum rating of the device Care should be taken when handling to 47 MT0100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V manon ESERIES avoid damage Drops causing shock greater than absolute maximum ratings may not destroy the device but will permanently alter the properties of the physical motion sensors which may cause the device to become inaccurate 6 3 Maintenance The MTi and MTx will not require any maintenance if properly used see also sections 6 1 and 6 2 However if the Motion Tracker is not functioning according to the specifications please contact Xsens Technologies B V support xsens com For maintenance it is necessary to remove the USB cable 6 4 Warranty and liability Xsens Technologies B V warrants the products manufactured by it to be free from defects in material and workmanship for a period of 1 year from the date of delivery
27. al Binder pin Wire color VCC Pin 2 Black GND Pin 4 Yellow green Z B Pin 1 Beige Y A Pin 5 Brown Do not use Pin 3 Blue 38 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V maen seems 4 4 7 Pin and wire color definitions MTx 49A G MTx Xbus MTx housing socket Binder 719 female back view solder bucket view ridge on upper side MTx housing plug Binder 719 male receptacle connector back view solder bucket view ridge on upper side Pin definitions MTx socket and wire color Signal Binder pin Wire color VCC Pin 2 Black GND Pin 4 Yellow green Z B Pin 1 Beige Y A Pin 5 Brown Ain Pin 3 Blue Pin definitions MTx plug and wire color Signal Binder pin Wire color VCC Pin 2 Black GND Pin 4 Yellow green Z B Pin 1 Beige Y A Pin 5 Brown Do not use Pin 3 Blue 4 4 8 Additional interface specifications The MTi amp MTx has additional interface lines for synchronization and or analog input support Which features are supported depends on the type of device See pin definitions of the device Analog IN This line supports in 16 bit sampling of an external analog signal of voltage range 0 to 5V at the sampling frequency used by the MTi MTx Currently this feature is not implemented in the firmware Contact Xsens for more information support xsens com Specification Value I
28. chnologies B V motion seems 5 2 2 Vibrations For best performance the MTi or MTx should be mechanically isolated from vibrations as much as possible Vibrations are measured directly by the accelerometers This is not necessary a problem but two conditions can make the readings from the accelerometers invalid 1 The magnitude of the vibration is larger than the 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 in the 3D orientation estimates 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 5 2 3 Magnetic materials and magnets When an MTi or MTx is placed close or on an object that contains ferromagnetic materials or that is magnetic by itself the measured magnetic field is distorted warped and causes an error in measured yaw heading 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 disturbanc
29. e Further the MTi and MTx have several onboard temperature sensors to allow compensation for temperature dependency of the various sensors 4 2 Physical properties overview MTi 28A G MTi 68SA GH MTx 28A G MTx 48A GH Interface Serial digital Serial digital Serial digital Serial digital RS 232 RS 422 RS 232 RS 485 Operating 4 5 15 V 4 5 15 V Voltage Power consumption AHRS 3D sonra orientation mode Temperature 0 C 55 C 0 C 55 C 0 C 55 C 0 C 55 C Operating Range Outline 58x58x22mm 58x58x22mm 38X53X21 mm 38x53x21 mm Dimensions W x Lx H W x Lx H Wx Lx H Wx Lx H Weight 50 g 50 g 30 g 30 g 4 3 Power supply The nominal power supply of the MTi and MTx is 5V DC The minimum operating supply voltage is gt 4 5V and the absolute maximum is lt 15V 31 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V maen SeenON e The sensor works at a power supply of gt 4 5 15V Use only SELF power supplies double isolated that are short circuit proof e The average operating power consumption is 360mW 70 mA 5V for the MTi and MTx The average power consumption may vary slightly with usage mode DSP load e The peak current at startup power on can be up to 200mA e When operated in room temperature the temperature inside the sensor will be 33 40 C in normal conditions 4 4 Physical interface specifications 4 4 1 USB se
30. e Errors in yaw heading due to such distortions can be 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 or MTx 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 the object In most cases when the disturbance of the magnetic field caused by placement of the MTi or MTx 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 can be executed in a few minutes and yields a new set of calibration parameters that can be written to the MTi MTx non volatile memory This calibration procedure is implemented in the software module Magnetic Field Mapper that comes with the SDK The method used in this software is unique in the sense that it allows a user chosen measurement sequence within certain constraints and that it allows for full 3D mapping 3D mapping is important in applications where the object is rotating through a substantial range of orientations e g a camera Normal
31. ents All configuration changes must be made while the device is in the so called Config State In this state the device accepts messages that set the output mode or changes to other settings Whenever the preferred configuration is completed the user can set the device to Measurement State In this state the device outputs data based the current configuration settings 3 2 States Power up WakeUp Procedure WakeUpAck received No WakeUpAck received Measurement The MTi MTx has two states i e Config State and Measurement State In the Config State various settings can be read and written In the Measurement State the device will output its data message which contains data dependent on the current configuration S The MotionTracker host protocol is a fully documented standard message based protocol developed by Xsens tailor made for the needs of inertial sensors 21 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V manon Secnnelesles There are two different ways to enter the Config State or the Measurement State At power up the device starts the WakeUp procedure if no action is taken it will then enter Measurement State by default using its latest stored configuration Prior to entering the Measurement State the Configuration message is sent to the host This is the configuration that is read from the internal non volatile memory and will be used in the Measurement State
32. ents in DATA field are FLOATS 4 bytes TS time stamp optional 2 4 Calibrated data performance specification rate of acceleration magnetic temperature turn field Unit deg s m s mGauss C Dimensions 3 axes 3 axes 3 axes Full Scale units 300 17 750 55 125 Linearity of FS 0 1 0 2 0 2 lt l Bias stability units 10 5 0 02 0 5 0 5 crane 10 0 05 0 5 8 Noise density units VHz 0 1 0 001 0 5 lo ABE deg 0 1 0 1 0 1 Bandwidth Hz 40 30 10 These specifications are valid for an MTi with standard configuration The standard configuration of the MTx is with a rate gyro with a range of 1200 deg s The following custom configurations are available standard configuration highlighted in bold Accelerometer Rate gyro 17 m s 1 7 g Full scale 1200 deg s MTx default 50 m s 5 g 300 deg s MTi default 100 m s 10 g 150 deg s higher noise levels 0 05 s VHz noise density increased bias instability Specifications of custom units may vary 1l temperature compensated deviation over operating temperature range lo 12 minimal resolution of digital readout is 0 0625 absolute accuracy is 0 5 C B after compensation for non orthogonality calibration 12 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V onion Secnnelosles 2 5 Calibrated data
33. ets the output mode of the MTi MTx The output mode can be set to calibrated sensor data and or orientation data The un calibrated raw data output however can not be used together with any of the other outputs MODE Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 MODE bits Output mode Bit 0 Temperature data Bit 1 Calibrated data Bit 2 Orientation data Un calibrated raw data not in combination with Bit 14 calibrated sensor data and or orientation data SetExtOutputMode MID 134 0x86 Data field MODE 2 bytes Direction To MTi MTx Valid in Config State Sets the extended output mode of the MT1 The extended output mode en or disables the analog outputs For Euler angles outputs also set the output mode to orientation data see SetOutputMode message MODE RiR R RPRIR R RP Ri R R RPRI RR Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 MODE bits Extended output mode Bit 1 Analog outputs 0 Disable analog outputs 1 Enable analog outputs Euler output Bit 15 2 Reserved SetOutputSetings MID 210 OxD2 Data field SETTINGS 4 bytes Direction To MTi MTx Valid in Config State Sets the output settings of the MTi MTx le Only applicable for MTi s with analog outputs option product code MTi 28A G D 25 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V manon seems SETTINGS eee eee EEEEEE ELI Bit 31 24 23 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
34. gnal noise is shown in the figure on the right The noise highly depends on type of measurement and the use of antialiasing filters See next section for additional information 2 8 3 Accurate measurement of analog outputs In general when taking measurements at a specific sample frequency it is important to ensure that the signal does not have frequency components that are higher than the sample frequency If these frequency components exist the sampled data will also contain these unwanted components i e aliasing Therefore the use of a proper defined low pass or antialiasing filter is important as it will remove these unwanted frequency components This filter should be located as close as possible to the measuring point e g at operational amplifier To minimize further noise contributions it is also important to use proper shielding and or short cables The antialiasing filter used for the calibration is a one pole lowpass filter for each channel This is a traditional RC filter see next figure R 8 2 kOhm Analog line 1 C 100nF Fc 1 2mRC 194 Hz Analog line 2 To measuring From sensor device Analog line 3 For highest accuracy it is recommended to make non referenced single ended measurement instead of a ground referenced measurement For example if an instrumentation amplifier is 19 MT0100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V manon veormelosies used
35. ial data max update rate is 512 Hz 7 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V manon Seannelesles MT The sensitivity of the system to such disturbance can be significantly reduced by an advanced sensor fusion algorithm setting called AMD Adapt to Magnetic Disturbances The default or normal operating mode should however be with this option turned OFF as drift around the vertical yaw heading will occur over time 2 3 Orientation output modes The orientation as calculated by the MTi or MTx is the orientation of the sensor fixed co ordinate system S with respect to a Cartesian earth fixed co ordinate system G The output orientation can be presented in different parameterizations e Unit Quaternions also known as Euler parameters e Euler angles roll pitch yaw XYZ Earth fixed type also known as Cardan or aerospace sequence e Rotation Matrix directional cosine matrix A positive rotation is always right handed i e defined according to the right hand rule corkscrew rule This means a positive rotation is defined as clockwise in the direction of the axis of rotation NOTE This section is intended to give detailed information on the definition of the various orientation output modes of the MTi and MTx The output sequence of the elements in the vectors and matrices defined here holds for all interface options RS 232 422 API GUI For more detailed i
36. in the XZ plane of the object coordinate frame situation A i e the MTi MTx can be used to identify the X axis of the object To preserve the global vertical the object must be oriented such that the object z axis is vertical The object reset causes the new S coordinate frame and the object coordinate frame to be aligned situation B NOTE Since the sensor X axis is used to describe the direction of the object X axis the reset will not work if the sensor X axis is aligned along the Z axis of the object A y B 5 sensor new sensor coordinate coordinate frame S frame Object Object coordinate coordinate frame O frame O MTi or MTx coordinate frame before A and after B object reset The new Z axis of the sensor coordinate frame will be along the vertical The new direction of the X axis will be the old X axis that is projected on the horizontal plane 17 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V maen seems 2 6 5 Alignment reset The alignment reset simply combines the Object reset and the Heading reset at a single instant in time This has the advantage that all co ordinate systems can be aligned with a single action Keep in mind that the new global reference x axis heading is defined by the object X axis to which XZ plane you have aligned the MTi MTx If you would like to preserve global vertical the Z axis of the object must be pointing up
37. ing factor Indicates how much the sensor data from the magnetometer should be weighted relative to the accelerometer data A number of 1 indicates the magnetometer data is considered equal to the accelerometer data and this should be the default value A number of 0 0 will completely disregard any data from the magnetometers otherwise valid range is lt 0 1 10 Filter Gain The gain is the most important tweaking option Very roughly the gain equals the cross over frequency of the sensor fusion algorithm in Hertz For example a value of 1 for the gain means more or less that frequency components of the calculated orientation vector exceeding 1 Hz will be determined by the rate of turn sensors and components below 1 Hz will be determined by the accelerometers and magnetometers The actual implementation is of course more sophisticated but this serves as an example for understanding Valid values are larger than 0 01 and lower than 50 i e lt 0 01 50 some values may lead to unstable operation of the algorithm under certain conditions The recommended default value of the gain is 1 Adapt to Magnetic Disturbances Large amounts of ferrous material iron nickel and cobalt but not e g aluminum and most stainless steels will disturb the homogenous earth magnetic field used as a reference by the Lo standard deviation of zero mean angular random walk gt in homogenous magnetic environment may depend on type of motion 5 inert
38. ion Rsg naturally yields the identity matrix P Rl 1 ResRse I The rotation matrix Rgs can be interpreted in terms of quaternions F a q5 g3 2q1q2 24093 24092 24193 Res 20 29142 A Z 4 q4 20243 2404 29193 2404 29243 20 G H G H 2q 2 1 2q q2 24043 2143 2002 2q1q2 2qoqs 246 24 1 2q243 2qoq1 24143 240 24293 2aoa1 2 245 1 or in terms of Euler angles Ras RZ RY RX a Y sinw A cos 0 sin d 0 0 j sinw cosy 0 0 1 0 0 cosp sing 0 0 1 sind 0 cos o lo sing coso cos 0 cos sin sinf cosy cos sin cos psind cosy sing sin Y eos sinw sinpsindsind eospeosd cos dsin 0 siny sind cos w sin 0 sin cos cos cos 0 As defined here Ras rotates a vector in the sensor co ordinate system S to the global reference system G xq Resxs Rso xs It follows naturally that Rsg rotates a vector in the global reference co ordinate system G to the sensor co ordinate system S For the rotation matrix DCM output mode it is defined that Ru Ry Ris H R Ro R i Ry Re Rol c gia YS VD A D Q l A a oe Here also the row order col order is defined 11 MT0100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V moea SEERA The output definition in rotation matrix DCM output mode is mo soc Lele elefeltlelh i s MID 50 0x32 ee All data elem
39. ions 5 2 3 Magnetic materials and magnets IMPORTANT NOTICES 6 1 ENVIRONMENTAL OPERATING CONDITIONS 6 2 ABSOLUTE MAXIMUM RATINGS 6 3 MAINTENANCE 64 WARRANTY AND LIABILITY 6 5 CUSTOMER SUPPORT iv motion technologies MT0100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V motion secnpelogies 1 Introduction The MTi and MTx are both complete miniature inertial measurement units with integrated 3D magnetometers 3D compass with an embedded processor capable of calculating roll pitch and yaw in real time as well as outputting calibrated 3D linear acceleration rate of turn gyro and earth magnetic field data The major difference between the MTi and the MTx is in the casing shape and weight connector and general ruggedness The MTi further supports various advanced IO options such as RS 422 and analog output DAC This documentation describes the use basic communication interfaces and specifications of both the MTi and the MTx Where they differ it is clearly indicated 1 1 Product Description 1 1 1 MTi miniature gyro enhanced Attitude and Heading Reference Sensor The MTi is a miniature gyro enhanced Attitude and Heading Reference System AHRS Its internal low power signal processor provides drift free 3D orientation as well as calibrated 3D acceleration 3D rate of turn rate gyro and 3D earth magnetic field data The MTi is an excellent measurement unit for stabilization and con
40. leads for these housings e g Farnell InOne code 889570 The pin definitions are the same as the pin definitions of the connected Motion Tracker i e pins one to seven for MTi and pins one to five for MTx Check the following sections for the pin definitions of your MTi MTx Pin 8 is always ground and pin 9 is reserved do not use this pin For definition of wire colors see next sections The operating temperature of the USB serial data and power cable CA USB2 is 0 C 40 C The MTi and MTx are designed to be used with the power supply supplied by Xsens integrated in the RS 232 22 485 to USB cable It is possible to use other power supplies however this must be done with care For safety and EMC any power supply used with the device must comply with the Electromagnetic Compatibility directive 33 MT0100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V motion secnnelesles 4 4 2 Pin and wire color definitions MTi 28A G MTi RS 232 standard version MTi housing socket ODU L series 7 pin female socket receptacle back view solder bucket view ODU product code GLOLOC TO07LCC0 000 MTi USB serial cable plug CA USB2 ODU L series 7 pin male connector plug back view solder bucket view solder contact for AWG 28 wire ODU product code S10LOC TO7MCC0 5200 Pin definitions MTi plug socket and wire color Signal ODU pin Wire color VCC Pin 1 Yellow GND Pin
41. nal acquisition and calculation time in this mode is 6 43 ms Practical example Orientation output mode in Euler angles 3 floats 460k8 bps 3 4 7 bytes 10 190 bits gt 190 bits 460800 bits s 0 41 ms transmission time 28 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V maen Secnnelosles Total time between physical event and receive of complete data message 6 43 ms 0 41 ms 6 84 ms worst case 3 4 2 Calibrated data output mode timing The internal acquisition and calculation time in this mode is 1 08 ms Practical example Calibrated data output mode 9 floats 115k2 bps 9 4 7 bytes 10 430 bits gt 430 bits 115200 bits s 3 73 ms transmission time Total time between physical event and receive of complete data message 1 08 ms 3 73 ms 4 81 ms worst case 3 5 Internal clock accuracy The internal clock jitter of the MTi and MTx is less than 25ns The internal clock of the MTi and MTx which generates the sample timing based on the set sample period is accurate to 30 ppm over the temperature operating range In practice this means that the worst case deviation after a 1 hour log is 0 108 seconds 3600 s 30 ppm or 10 sample counts in 360 000 at 100 Hz sample rate 0 3 us sample 100 Hz NOTE For long logging times that require synchronization with external clocks or events means of synchronization with a high precision external clock should be conside
42. nformation about the respective interfaces please refer to their specific documentation Direct gt MTi and MTx Low level Communication Documentation API gt MT Software Development Kit Documentation GUI gt MT Software Any disturbance in the magnetic field due to the object the MT is attached to can be compensated for please refer to the Magnetic Field Mapping software plug in 7 Please note that due to the definition of Euler angles there is a mathematical singularity when the sensor fixed X axis is pointing up or down in the earth fixed reference frame i e pitch approaches 90 In practice this means roll and pitch is not defined as such when pitch is close to 90 deg This singularity is in no way present in the quaternion or rotation matrix output mode 8 MTO100P G e sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V motion Secnpoelogies 2 3 1 Quaternion orientation output mode A unit quaternion vector can be interpreted to represents a rotation about a unit vector n through an angle das cos nsin 5 A unit quaternion itself has unit magnitude and can be written in the following vector format das qo q 9 43 Wa lit Quaternions are an efficient non singular description of 3D orientation and a quaternion is unique up to sign q q An alternative representation of a quaternion is as a vector with a complex part the real component is the first
43. nput voltage range 0 to 5V Input capacitance 150 pF ADC resolution 16 bit Supported by MTi RS 232 MTi 28A G and MTx Xbus MTx 49A G 39 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V maen Secnnelesles AnalogOut Please refer to section 2 8 SyncIn This digital input can be used to trigger the MTi MTx for synchronization purposes The MTi MTx can wait until a valid trigger is detected and it either starts sampling or sends the latest calculated data For more information about the SyncIn settings timing polarity see the MT Low level Communication Documentation The signal specifications are listed in the next table Specification Value Input range high voltage 2 0 to 20V Input range low voltage 0 0 to 0 4V Input resistance 10 kOhm Latency offset 0 17 6us Latency offset gt 0 not including 21 7us Jitter 40ns Supported by MTi RS 232 MTi 28A G MTi 68A G MTi RS 422 and MTx 28A G MTx RS 232 standard version SyncOut This is an output signal that can trigger other device s for synchronization purposes The triggering instance is related to the sampling instance of the MTi The signal parameters like type offset skipfactor or width can be customized using the SyncOut settings See the MT Low level Communication Documentation The signal specifications are listed in the next table Specification
44. of the MTData message If its maximum value is reached i e 65535 OxFFFF it will wrap and start at zero again 27 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V Motion seems 3 4 Communication Timing For many applications it can be crucial to know exactly the various delays and latencies in a system In this section it is described how the timing between physical events and the device output are related in the basic usage modes of the MTi and MTx Sampling Physical ie ADC Calibration Sensor Output Fusion Triggering Data Hardware software triggers When the MTi MTx is in Measurement State the internal DSP continuously runs a loop roughly according to the above diagram The triggering can be generated by device internal sampling triggers or by external software triggers polling or even hardware triggers normally not recommended The time delay between a physical event e g an orientation change or acceleration is dictated by two factors 1 Internal acquisition and calculation time 2 Serial transmission time The serial transmission time can easily be calculated Total bytes in message 10 bits byte wenn nn nnn nnn enn nnn nnn nn nnn nn transmission time in seconds communication baudrate bits per second These two factors will be discussed using the example of the two common output modes of the MTi and MTx 3 4 1 Orientation output mode timing The inter
45. r please note that the two output modes can easily be combined so that you get a combined data packet of orientation data and inertial calibrated data together with the same time stamp 2 1 Co ordinate systems 2 1 1 Calibrated Sensor readings All calibrated sensor readings accelerations rate of turn earth magnetic field are in the right handed Cartesian co ordinate system as defined in figure 1 This co ordinate system is body fixed to the device and is defined as the sensor co ordinate system S The 3D orientation output is discussed below in section 2 2 z AD Figure 1 MTi and MTx with sensor fixed co ordinate system overlaid S The co ordinate system is aligned to the external housing of the MTi and MTx The aluminum base plate of the MTi is carefully aligned with the output coordinate system during the individual factory calibration The alignment of the bottom plane and sides of the aluminum base plate with respect to w r t the sensor fixed output coordinate system S is within 0 1 deg High accuracy alignment between the plastic housing and the sensor fixed output coordinate system S is not possible for the MTx for obvious reasons The actual alignment between the S co ordinate system and the bottom part of the plastic housing is guaranteed to lt 3 The non orthogonality between the axes of the body fixed co ordinate system S is lt 0 1 This also means that the output of 3D linear acceleration
46. rate reference Placement and subsequent aligning must be done very carefully otherwise alignment errors may be induced 2 6 2 Heading reset Often it is important that the global Z axis remains along the vertical defined by local gravity vector but the global X axis has to be in a particular direction In this case a heading reset may be used this is also known as bore sighting When performing a heading reset the new global reference frame is chosen such that the global X axis points in the direction of the sensor while keeping the global Z axis vertical along gravity pointing upwards In other words The new global frame has the Z axis along gravity pointing upwards the X axis in the plane spanned by the vertical and the sensor X axis perpendicular to the global Z axis and the Y axis such that a right handed coordinate system is formed NOTE After a heading reset the yaw may not be exactly zero this occurs especially when the X axis is close to the vertical This is caused by the definition of the yaw when using Euler angles which becomes unstable when the pitch approaches 90 deg 2 6 3 Global reset When performing a full global reset the MTi MTx axes S is used to define the axes of the new global coordinate frame G When pressing the reset button or sending the reset command S has to be orientated in such a way that the sensor axes all point in exactly the same direction as the axes of the global coordinate
47. red 3 6 Default Serial Connection Settings Bits second bps 115200 Data bits 8 Parity none Stop bits 20 Flow control none These settings are for same for the RS 232 as the RS 422 versions The baudrate bps setting can be changed by the user The maximum is 921k6 bps and the minimum 9600 bps Please refer to the MT Low level Communication Documentation for details 17 Tn order to allow correct frame timing 1 stop bit is also possible in receive only mode 29 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V manon seems 3 6 1 General definitions for binary data All binary data communication is done in big endian format Example Un calibrated 16 bits accelerometer output 1275 decimal 0x04FB hexadecimal Transmission order of bytes 0x04 OxFB Calibrated accelerometer output float 4 bytes 9 81 decimal 0x411CF5C3 hexadecimal Transmission order of bytes 0x41 0x1C OxF5 0xC3 The bit order in a byte is always MSB LSB gt bit 7 bit 0 30 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V maen seems 4 Physical Specifications 4 1 Physical sensor overview MTi and MTx Sensor Fact Table Accelerometers MEMS solid state capacitative readout Rate of turn sensor MEMS solid state monolithic beam rate gyroscope structure capacitative readout Magnetometer Thin film magnetoresistiv
48. rial data and power cables overview RS 232 MTi cable CA USB2 RS 232 MTx cable CA USB2x RS 422 MTi cable CA USB6 RS 485 MTx cable CA USB4x My The USB serial data and power cable delivered with the MTi and MTx Development Kit is compatible with USB 1 1 and higher Make sure your PC USB outlet is rated to deliver 100 mA or more all USB compliant outlets should be The RS 422 MTi cable CA USB6 is compatible with the RS 422 version of the MTi Blue cable markers are located at the connector and the casing for visual distinction between the RS 232 MTi cable The MTx can not be ordered with RS 422 interface therefore no RS 422 MTx cable is available The RS 485 MTx cable has yellow cable markers to indicate RS 485 interface instead of RS 232 The USB serial data and power cable provides easy access to the individual pins of the Motion Tracker Inside the housing there is a free connector that can for example be used for synchronization purposes The following photo shows the location of the connector 18 Tf an alternative power supply is used check if it can supply these peak currents Do not use a power supply if the peak supply current is lower than stated 32 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V motion secnpelogies It is a 9 pins Molex header type 53048 0910 and it mates with the Molex crimp housing type 51021 0900 Farnell InOne code 615122 Farnell also offers crimp
49. s 2 8 2 Accuracy 2 8 3 Accurate measurement of analog outputs 3 BASIC COMMUNICATION 3 1 INTRODUCTION 3 2 STATES 3 3 MESSAGES 3 3 1 Message structure 3 3 2 Message usage 3 3 3 Common messages 3 4 COMMUNICATION TIMING 3 4 1 Orientation output mode timing 342 Calibrated data output mode timing 3 5 INTERNAL CLOCK ACCURACY 3 6 DEFAULT SERIAL CONNECTION SETTINGS 3 6 1 General definitions for binary data iii Wsaens motion technologies j Yo NN AUU A Bw wone MT0100P G MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V 4 Wsaens PHYSICAL SPECIFICATIONS 4 1 PHYSICAL SENSOR OVERVIEW 4 2 PHYSICAL PROPERTIES OVERVIEW 4 3 POWER SUPPLY 4 4 PHYSICAL INTERFACE SPECIFICATIONS 4 4 1 USB serial data and power cables overview 44 2 Pin and wire color definitions MTi 28A G MTi RS 232 standard version 4 4 3 Pin and wire color definitions MTi 68A G MTi RS 422 4 44 Pin and wire color definitions MTi 28A G D MTi RS 232 analog outputs 44 5 Pin and wire color definitions MTx 28A G MTx RS 232 standard version 4 4 6 Pin and wire color definitions MTx 48SA G MTx RS 485 standalone 4 4 7 Pin and wire color definitions MTx 49A G MTx Xbus 44 8 Additional interface specifications 4 5 HOUSING MECHANICAL SPECIFICATIONS 4 5 1 Dimensions MTi 4 5 2 Dimensions MTx OPERATING GUIDELINES 5 1 NORMAL OPERATING PROCEDURE 5 2 PLACEMENT CONSIDERATIONS 5 2 1 Transient accelerations 5 2 2 Vibrat
50. s For example the MID of message requesting the output mode ReqOutputMode is the same as the message that sets the output mode SetOutputMode The difference between the two messages is that the Length field of ReqOutputMode is zero and non zero for SetOutputMode Example Request current output mode Sending message ReqOutputMode OxFA OxFF 0xD0 0x00 0x31 hexadecimal values Receiving message Acknowledge ReqOutputModeAck OxFA OxFF 0xD1 0x02 MH ML CS hexadecimal values ReqOutputModeAck contains data which represents the current mode MH amp ML CS stands for the checksum value To change the output mode you must add the new mode in the data field of the sending message Set the output mode Sending message SetOutputMode OxFA OxFF OxDO 0x02 MH ML CS hexadecimal values Receiving message Acknowledge SetOutputModeAck OxFA OxFF 0xD1 0x00 0x30 hexadecimal values 3 3 3 Common messages GoToConfig MID 48 0x30 Data field n a Direction To MTi MTx Valid in Measurement State amp Config State Switches the active state of the device from Measurement State to Config State This message can also be used in Config State to confirm that Config State is currently the active state 24 MTO100P G e motion technologies sans MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V SetOutputMode MID 208 0xD0 Data field MODE 2 bytes Direction To MTi MTx Valid in Config State S
51. s care of the hardware communication interfacing and it is an easy way to get soft real time performance Typically this is preferred when you want to access the MT s capabilities directly in application software such as MATLAB LabVIEW Excel Visual Basic etc examples included in SDK Both polling and events based methods are supported Applies to Windows PC platform gt Please refer to the MT Software Development Kit Documentation for more information on this topic NOTE The MT COM object also provides backwards compatibility of your software developed for the MT9 B 1 3 3 Direct low level communication with MTi or MTx Direct interfacing with the MTi or MTx RS 232 422 is the natural choice if you are looking for full control maximum flexibility and or have hard real time performance requirements The MTi MTx s low power embedded DSP does all the calculations calibration you just retrieve the data from the COM port using the MTi MTx binary communication protocol using with streaming free running mode or polling request mode Even this part is made easy for you by the inclusion of the source code C of the MT Communication C class CMTComm in the MT SDK Example C C application code should get you quickly started on your development platform of choice Example code that has been functionally checked and compiled on both Windows and Linux is included Applies to Any RT OS or processor platform C C 3 MT
52. set value are determined for each analog output during calibration of the device and can be found on the device individual calibration certificate 2 8 2 Accuracy The voltages of the three analog outputs are generated by a digital to analog converter DAC which has a resolution of 12 bits The calculated values are mapped into a range of zero to three volts In other words the theoretical resolution of the analog output is 3V 4096 14 Only applicable for MTi s with analog outputs option product code MTi 28A G D 18 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V manon veormelosies 0 7mV or 360 4096 0 09 In practice the accuracy is mainly defined by the signal noise and the relative accuracy of the DAC besides the accuracy of the orientation calculation itself The relative accuracy is the deviation between a perfect straight line and the DAC transfer function Typical deviations are 2mV maximum deviation specified for the DAC is 11mV The calibration certificate specifies for each channel the RMS value of the deviation An example of the relative accuracy is plotted in the following leftmost figure x 10 Relative accuracy Captured analog data 200Hz and 0 15enV resolution 1 ch 1 Volts o 1 1 L L L 1 L a L 4 500 1000 1500 2000 2500 3000 3500 4000 o 1 2 3 4 5 Binairy code time sl An example of the si
53. summed and the lower byte value of the result equals zero the message is valid and it may be processed The checksum value of the message should be included in the summation 3 3 2 Message usage Generally a message with a certain MID value will be replied with a message with a MID value that is increased by one i e the acknowledge message Depending on the type of message the acknowledge message has no or a certain number of data bytes In some cases an error message will be returned MID 66 0x42 This occurs in case the previous message has invalid parameters is not valid or could not be successfully executed An error message contains an error code in its data field 23 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V maen seems Example Requesting the device ID of an MTi MTx Sending message ReqDID OxFA OxFF 0x00 0x00 0x01 hexadecimal values Receiving message Acknowledge DeviceID OxFA OxFF 0x01 0x04 HH HL LH LL CS hexadecimal values The requested Device ID is given in the acknowledged message DeviceID here shown as HH HL LH LL the checksum is CS As you can see the MID Message ID of the acknowledgement is increased by one in comparison with the sending message ReqDID Some messages have the same MID and depending on whether or not the message contains the data field the meaning differs This is the case with all the messages that refer to changeable setting
54. tatic conditions to allow fast convergence 2 Try to avoid leaving the device powered if not needed If you use the USB serial cable that comes with the Development Kit this means you either unplug the MTi or MTx from the cable or you un plug the USB serial cable from you PC 5 2 Placement considerations 52 1 Transient accelerations The 3D linear accelerometers in the MTi and MTx are primarily used to estimate the direction of gravity to obtain a reference for attitude pitch roll During periods of transient free accelerations i e 2 derivative of position the observation of true 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 If you want to use the MTi or MTx 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 CG The acceleration of the vehicle as a whole can of course not be taken into account 44 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Te
55. the magnetic declination varies depending on your location on earth and can be roughly obtained from various models of the earths magnetic field as a function of latitude and longitude The MTi MTx can accept a setting of the declination value This is done by setting the heading in the MT Software SDK or by direct communication with the sensor The output will then be offset by the declination and thus referenced to local true north 6 MT0100P G Wsaens e MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V matin Secnpologies 2 2 Orientation performance specification Typical performance characteristics of MTi and MTx orientation output Dynamic Range all angles in 3D Angular Resolution 0 05 RMS Static Accuracy roll pitch lt 0 5 Static Accuracy heading lt 1 0 Dynamic Accuracy 2 RMS Update Rate user settable max 120 Hz 2 2 1 Sensor fusion algorithm settings The MTi and MTx has been designed to operate with the highest possible accuracy under a wide range of operating conditions Under some circumstances however the performance may benefit from some of the advanced settings available in the Sensor Fusion Algorithm Mainly when transient accelerations are expected it may be attractive to the advanced user to tweak or explore the influence of some advanced settings of the algorithm NOTE Normal operation does not require the user to change these settings Weight
56. trix A and a gain matrix G The misalignment specifies the direction of the sensitive axes with respect to the ribs of the sensor fixed coordinate system S housing E g the first accelerometer misalignment r describes the sensitive direction of the accelerometer on channel one The three sensitive directions are used to form the misalignment matrix ae Ay ay K 0 0 A Aar A2 y Az G 0 G 0 is azy fel 0 0 G3 G 0 0 dre iy a Kr 0 Go 0 Oor Ay G22 O lo o all a3 E a3 y 03 2 With O representing higher order models and temperature modelling etc Each MTi and MTx is also modeled for temperature dependence of both gain and bias for all sensors and other effects This modeling is not represented in the simple model in the above equations but is implemented in the firmware 13 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V manon Seannelosles The basic parameters in the above model of your individual MTi or MTx can be found on the MT Test and Calibration Certificate 2 5 2 Calibrated inertial and magnetic data output mode Output of calibrated 3D linear acceleration 3D rate of turn gyro and 3D magnetic field data is in sensor fixed coordinate system S The units of the calibrated data output are as follows Vector Unit Acceleration m s Angular velocity rate of turn kaak a u arbitrary units Magnetic field normalized to earth field strength
57. trol of cameras robots vehicles and other equipment Fields of use e robotics e aerospace e autonomous vehicles e marine industry e bore industry 1 1 2 MTx miniature inertial 3DOF Orientation Tracker The MTx is a small and accurate 3DOF inertial Orientation Tracker It provides drift free 3D orientation as well as kinematic data 3D acceleration 3D rate of turn rate gyro and 3D earth magnetic field The MTx is an excellent measurement unit for orientation measurement of human body segments d Example fields of use e biomechanics exercise and sports virtual reality animation motion capture 1 MT0100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V motion technologies 1 2 Overview MTi and MTx Development Kit Photos of the MTi left and MTx right Development Kit 1 2 1 Contents O o0o0000 0 O MTi or MTx miniature inertial measurement unit Device individual calibration certificate Quick Setup Sheet USB serial data and power cable 5 meters CA USB2 CA USB2x CA USB6 MTi and MTx User Manual and Technical Documentation MT0100P MTi and MTx Low level Communication Documentation MT0101P MT Software Development Kit MT Software PC Windows 2000 XP MT Communication C class for low level communication full C source MotionTracker object COM object API Windows Example source code C C MATLAB LabVIEW VisualBasic Magnetic Field
58. uaternion or rotation matrix output mode The Euler angles can be interpreted in terms of the components of the rotation matrix Rgs or in terms of the unit quaternion qas _1 Ra 1 24243 200 bes tan Ee tan ae a a Ga R33 2q2 2q 1 as sin Rai sin 2q1q3 24042 Roy 1 20192 24093 Was an 2 an 2q 2q 1 Here the arctangent tan is the four quadrant inverse tangent function NOTE that the output is in degrees and not radians The output definition in Euler angle output mode is MTData MID 50 0x82 All data elements in DATA field are FLOATS 4 bytes TS time stamp optional 2 3 3 Rotation Matrix orientation output mode The rotation matrix also known as Direction Cosine Matrix DCM is a well known redundant and complete representation of orientation The rotation matrix can be interpreted as the unit vector components of the sensor coordinate system S expressed in G For Res the unit vectors of S are found in the columns of the matrix so col 1 is Xs expressed in G etc A 8 foll is also known as bank pitch is also known as elevation or tilt 10 ce 2 66 yaw is also known as heading pan or azimuth 10 MTO100P G sons MTi and MTx User Manual and Tech Doc 2006 Xsens Technologies B V maen SeenON rotation matrix norm is always equal to one 1 and a rotation Rgs followed by the inverse rotat
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