[ros-users] [Discourse.ros.org] [ROS Projects] IMcoders: easy-to-install (and cheap) odometry sensors

ruffsl ros.discourse at gmail.com
Tue Aug 14 19:54:56 UTC 2018

[quote="solosito, post:5, topic:5543"]

Thus, depending on the use case, our sensors will provide a better or worse output depending on the quality of the IMU integrated in the board (sometimes it is just a matter of calibration).


How are you currently calibrating for the extrinsics of the origin of the IMU sensor with respect to the center of rotation of the wheel axis? After fixating the IMCoder to the wheel in a new position, are you by chance rotating the wheel at a constant velocity, then inferring the rotational speed `` from the sinusoidal frequency from the two IMU accelerometers axes perpendicular to the wheels axle, then additionally using the amplitude to infer the radial distance `r` from the wheel axis, and the phase of the peak of the waveform to discern the angular position ``? I suppose the phase between accelerometer axes x, y (assuming z points along the wheel axle) could be used to resolve the rotation of the IMU about the endpoint of the vector `(r, )` if neither `x` or `y` happen necessarily lie along `(r, )`.

I'm not sure how level the mounting of your fixture is to the wheel, or even if the toy's wheel and axles would be true (straight); if it's only roughly perpendicular, the offaxis comentents may then need to be accounted for as well, necessitating a full 6DOF calibration rather than just a 3DOF calibration. Additionally, if positioning is subject to disturbances during reinstallment, like in the case with the rotationally symmetric magnetic clips, then perhaps making the calibration online or as a tracking filter might be appropriate to simplify deployment to arbitrary platforms.


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