(Torque) Calibration

[sophielueth]

Dear Kinova Team,

we wanted to calibrate the torque sensors in our Kinova Gen3. Looking for the correct interface in the documentation, I found this. I am wondering what the parameters global_gain (float), global_offset (float), gain (float [] of length 4) and offset (float [] of length 4) represent, that exist for each actuator (see e.g. here. I assume the torque sensors to be strain gauges and therefore only expected one gain and one offset per sensor for a linear mapping.

Could you please elaborate on how these parameters are used and how they were identified?

On another note: I also came across the class CalibrationItem here. It contains COGGING, MAGNETIC, MOTORand POSITION_RANGE. What parameters exactly are calibrated here?

Thank you!

[kyilmazKinova]

Hi, you should use the WebApp. Simply position your Gen3 in a candle pose then, on the WebApp, navigate to "Configurations/Robot/Actuators/ActuatorX". For every Actuator, click on "Set Offset".

Best regards,

[sophielueth]

Hi kyilmazKinova,

Thank you for your fast answer! I understand that clicking "set offset" will set the offset of the torque sensors (probably the TorqueOffset shown here). This limits calibration to one static parameter but does not allow me to influence the readings of the robot when under load (apart from that offset, which is added).

I want to understand to what extent I can adjust/calibrate the robot's sensors. The function WriteTorqueCalibration which is part of ActuatorConfigClient takes a Torque Calibration object as input. This object has the parameters global_gain, global_offset, gain and offset.

Could you please elaborate on how these parameters are used and how they were identified?

(And I'm still interested in information about the class CalibrationItem here.)

Best,