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Converting the acceleration data from the sensor (MetaMotion R) frame to Earth frame of reference

ResearcherResearcher
in General

Hello everyone,

I am using Metamotion R sensors to get the linear accelerations. First of all I tried to stream both of the linear acceleration and the Euler angles, but the MetaBase application for iOS gave me an error that the sensors cannot stream both of them. I tried to use the data from the accelerometer and the gyroscope and I have a question about this option

1) If the approach of the integrating the gyroscope data with respect to time to get the instantaneous Euler angles and then getting the acceleration in Earth frame of reference by multiplying the inverse of Euler rotation matrix with the acceleration data is right . Then, which rotation matrix convention shall I use? Is it 'XYZ', 'ZYZ', or 'ZYX'?

Another thing, when I tried the MetaBase application for windows, I did not show me the error of measuring linear acceleration and Euler angles data simultaneously but another problem I found is that I cannot stream from more than two devices. Is there a way to overcome the problems of the MetaBase applications for windows and iOS?

Thanks in advance.

Comments

  • EricEric

    Why do you need Euler angles if you are looking to measure linear acceleration?

    Gyro data is noisy and should not be solely relied upon for an extended period of time.

    Those are not problems with the app. Streaming from more than 2 devices is not a recommended use case nor is streaming both linear acc and Euler angles simultaneously (the UWP app should have caught this). If you want to record both linear acc and Euler angles and/or collect data from multiple devices simultaneously, you will need to:

    1. Log the data to the on-board flash chip
    2. Use a Linux based system, like the MetaHub, where you can use multiple Bluetooth adapters
    3. Design an app customized for your use case, if in fact your device's (PC, iPhone, etc) Bluetooth stack / adapter can handle that amount of data
      • This probably will not be likely without need multiple adapters
  • ResearcherResearcher

    Thanks Eric for your reply.

    I need Euler angles to convert the linear acceleration of the sensor axis to the earth axis. I need them in this way to compute the velocities of the body and the arms in xyz of the earth reference.What I found, is that I can stream both of them from maximum 2 sensors using the MetaBase app for windows PC. But if I want to measure both of them from more than two sensors, then I will need to log you are right.

    Regards,

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