IMU Sensor (Acceleration & Gyroscope Values) in NED vs ENU Frames

in Matlab R2020b Sensor Fusion Tracking Toolbox. Considering "Creating an Arc Trajectory" example. NED trajectory and ENU trajectory were created. Additionally imu sensor object was created in NED, ENU frames respectively. The following example is for NED frame

rng('default')
trajectory = waypointTrajectory(constraints(:,2:4),'TimeOfArrival',constraints(:,1), ...
                           'Orientation',quaternion(constraints(:,5:7),'eulerd','ZYX','frame'),...
                           'ReferenceFrame','NED');
imu = imuSensor('SampleRate', sampleRate, 'ReferenceFrame', 'NED');

Considering the axis-orientation for NED and ENU Frames ( , , )

I compared the outputed Accelerometer in NED vs ENU frames respectively and found that only Z-axis matches the above convention. Whereas the X-axis & Y-axis are extacly identical.

The Gyroscope values in NED vs ENU frame are exactly identical.

What could be the possible explaination for these outputs?

How can I generate the correct data w.r.t to NED and ENU frames? or It is possible to generate the data into one of the frames and then transform it to the other one?

Answer 1

[Ryan Salvo]

Hi Ravindra,

If you change the ReferenceFrame property for both the waypointTrajectory and imuSensor, the specified waypoints are also converted. This leads to the same output for the IMU, with only the gravity direction changed. That is why you are seeing the same x and y data for the accelerometer, but a change in the z data, and why the gyroscope has the same x, y, and z data.

As a simple example, if you set two waypoints [0 0 0] and [10 0 0] with ReferenceFrame set to NED, this will generate a trajectory moving North 10 meters. If only the ReferenceFrame property is changed to ENU, then the trajectory generated will be moving East 10 meters.

Thanks,

Ryan