MLX300: Using Collision Detect to Determine a Part was Picked

The typical method to determine whether a part was picked, is to use vacuum feedback, a proximity sensor or an optical sensor.   An alternative way to detect a part with MLX300 is to use Collision Detection feedback.    This solution requires no additional hardware and has been used in the past with heavier parts.

The MLX300 has a command to reset the Max Collision Detection values that are shown on the robot pendant.    After a reset, it's able to get the new max detection values in the PLC tags and compare them to the reference values of an empty gripper.

PROGRAM SEQUENCE

1.  Execute a move to the pick position.

2.  After a short 25ms delay, command the MLxRobotResetCollisionDetectionTorque AOI, and wait for the AOI done bit to turn on (.sts_DN).
                - This command can only be executed when the robot is not moving.
               - The collision detection max values will be cleared.

3.  Move the robot up to a location above the pick.

4.  Command the MLxRobotGetCollisionDetectionTorque AOI to get the new max detection values.

5.  After the AOI done bit turns on, compare the MaxMeasuredTorque[x] values in the PLC tags with the reference values recorded with an empty gripper.    For many case, the PLC only needs to compare one value, such as the torque of the upper arm axis or Torque[2].

6.   If the values are close to the ones obtained from an empty gripper, move the robot back to the pick location and try again.