Optimize gripper at pickup - Gripper orientation

Owned by Roger Almaas
Last updated: Oct 30, 2024 by Roger Almaas
3 min read

In order to get better reach or performance, the program can automatically recalculate and use the gripper rotated by +90, -90, 180 degrees at the pickup position. This may be necessary to reach the pallet corners or avoid collision with the base frame.

The allowed rotations can be configured. You can instruct the optimizer to enforce the default orientation, choose between forward and backward, or choose between forward, backward, left, or right. Pally will calculate the best optimized grip for each box, if enabled.

Visual representation of the different gripper rotations at pickup

forward (default)
backward

 

Note: the rotations are relative to the default calibrated orientation (forward)

 

Gripper optimization settings can be selected in Program / Pally / Advanced / Path planning

None: forward (the gripper direction at the calibrated pick position)

2-Way: forward and backward

4-Way: forward, backward, left, right

Gripper optimizer can be configured in run-time via the variable rf_grip_rot, which is an array of 5 elements.

  • The first element is the number of allowed rotations n,

  • The next n elements are the allowed rotations in degrees.

    • 0: calibrated orientation

    • 90: right orientation

    • -180: backwards orientation

    • -90: left orientation

Example:

rf_grip_rot = [3, 0, -90, 90, 0]

This will tell the optimizer to choose a gripper rotation between forward, left, and right (backward is not allowed)

If you want to limit the allowed gripper rotation to left and right you need to use the following Example:

rf_grip_rot = [2, 90, -90, 0, 0]

If you want to use this in a particular pattern, The best place for this script line is the BeforeZone callback. Here you can check the name of the pattern, and set rf_grip_rot accordingly.

Please note: rf_grip_rot is used as a default value to initialize the optimizer, but gripper rotation in the pattern file has priority. If you have set the enforced gripper rotation in the pattern JSon file (see Advanced: gripper rotation: front-back-left-right in the pattern editor) for one or more box positions, this will override rf_grip_rot. You can always enforce any gripper rotation(s) in the pattern file independent of the default gripper optimizer settings.

Rotation direction

Pally will automatically choose rotation direction between pickup and placing the box, as well as the rotation direction between placing the box and picking up the next box. This is done to avoid Wrist 3 errors, where to robot rotates more then 360 degrees and the palletizing operation is stopped by protective stop.

This automatic rotation direction can not be overruled.

You can reduce rotation by locking gripper orientation and box orientation, but you can not set a desired rotation direction.