• What are the gyro bias stabilities on the VN-100/VN-200?

    For both the VN-100 and VN-200, the bias stabilities are < 10 deg/hr.  Sample Allan Deviation plots are provided below:

    Allan Deviation
    Allan Deviation
    Allan Deviation
    Allan Deviation
  • What are the Limitations of the individual MEMS Sensors?

    The MEMS Gyros has high noise density and large bias drifts as shown below:

    MEMS Gyro Noise

    mems-limitations-3
  • How can the Gyro bias drift be estimated?

    Gyros of all types (as well as accelerometers) are subject to bias instabilities, in which the zero reading of the gyro will drift over time due to inherent noise properties of the gyros.  The attitude filter on the VN-100 uses the accelerometer and magnetometer measurements to estimate the drift in the gyro zero reading over time, such that the reported gyro readings are compensated for this drift.

    The INS filter also uses the GPS outputs to estimate the real-time accelerometer bias drift in addition to the gyro bias drift. 

  • How can the accelerometer bias drift be estimated?

    The INS filter on the VN-200 uses the GPS outputs to estimate the real-time accelerometer bias drift in addition to the gyro bias drift. 

  • Can the INS withstand saturation in any axis?

    The INS will operate with degraded performance if any of the axes are saturated. Likely sensor saturation in VectorNav’s experience will only occur on the accelerometer due to excessive vibration. The gyro range is +/- 2000 deg/s and the accelerometer range is +/-16g.

  • What is the recovery time from saturation?

    This depends on the dynamic motion. The INS might have lost some accuracy and dynamic motion will cause it to re-align itself. Worst case the solution is lost and a system re-start could be required, which would take a few minutes to fully recover the solution accuracy.

  • Is there hysteresis from saturation? Does it maintain calibration?

    In our experience there is no hysteresis from saturation.

  • Can we upgrade precision by having additional units on the platform?

    The precision of the VN-200 output exceeds its accuracy.  The accuracy of the system can be improved by averaging solutions from several devices and a 1/SQRT(# VN-200 sensors) performance improvement is theoretically possible.