FT Sensor Calibration

FT Sensor Calibration#

Calibrating the FT sensor#

The zero of the ankle FT sensor (ATI Mini58) can be set with

ros2 run kanagroo_constrained_dynamics_ros calibrate_ft_sensor.sh        # pick a sensor interactively
ros2 run kanagroo_constrained_dynamics_ros calibrate_ft_sensor.sh --all  # zero every FT sensor found

Run it on the robot (it talks to the hardware directly via the EtherCAT master — it is not a ROS node).

  • Warm up first. The strain gauges drift with temperature, so use and calibrate the sensor only after the robot has been powered on for ~30 minutes, once it is thermally settled — otherwise the zero keeps drifting as it warms up.

  • Calibrate unloaded. Zeroing makes the sensor read zero for whatever wrench is applied at that moment. That load is baked into the new zero and subtracted from every later reading, so do it with no (or very little) load on the foot — foot in the air, nothing pressing on it.

  • Rarely needed. A good zero holds; this is a once-in-a-while operation (after warm-up, a hardware change, or visible drift), not a routine step.

How it works: the script finds the FTSensor EtherCAT slaves, and for each one switches it to PRE-OP, writes the update-offset command to SDO object 0xFB01, switches it back to OP, then polls the status code (0x6010) until the board reports the calibration finished.

Note

Allow up to ~10 s per sensor. The completion poll (check_calibration_status) is currently unreliable — the FT firmware does not report the status bits dependably — so the script may print “complete” immediately or loop on a stale value rather than tracking the real progress. The offset update itself still takes time on the board, so just give it ~10 s before trusting the new zero (or power-cycling), regardless of what the script prints.