Issue with low-force assembly application using Force Mode

General Application Help: How do I?
1

Hello,

I am developing a precision assembly application using Force Mode. The process requires the robot to simultaneously apply downward pressure along the Z-axis and a rotational torque around RZ.

My process is as follows:

  1. The robot picks the part from the Jig.

  2. Approaches the assembly position (approx. 50mm above the mold).

  3. Executes zero_ftsensor(), sets Damping and Scaling to 0.8.

  4. Activates Force Mode (Simple): Moves downward with a target force of 2N.

  5. Executes end_force_mode().

  6. Activates Force Mode (Frame): Applied forces are F_z = 8N and T_r = 2.5Nm.

  7. Wait condition: Current_T_rz_value >= 0.5Nm OR Rotation_angle_deg > 6.

  8. Check logic: If the tool rotation angle exceeds >= 6, trigger an Error/Alarm. Otherwise, release the gripper.

However, according to the datasheet, the robot’s sensor specifications are as follows:

  • Force: Accuracy ± 4N, Precision ± 3.5N.

  • Torque: Accuracy ± 0.3Nm, Precision ± 0.2Nm.

Currently, during testing, the NG (Not Good) rate is quite high. Given that my target forces are almost equal to the sensor’s margin of error, are there any solutions or calibration methods to overcome this hardware limitation?

2

There are 3rd party force torque sensors that you can add that probably have more precision.

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