Condition
- The depth of field used in the scene is relatively small (within a range of about 300 mm in the camera’s Z-direction).
- The error in the Z-direction caused by temperature drift is also relatively small (around 5 mm).
- The reference marker is within the defined range for the robot’s job (in the camera’s Z-direction).
Method
During the normal operation of the vision system, fix a marker within the camera’s field of view. While recognizing the workpiece, also recognize the pose of the marker.
- If using an object as the marker, get its pose using 3D matching.
- If using the ground (workstation platform surface) as the marker, use Step “Calc Poses and Dimensions from Planar Point Clouds.”
- The pose recognition requirement for the marker is: the Z-axis repeatability of the pose needs to be controlled within 0.1 mm.
- Save the reference pose of the marker.
Read the reference pose of the marker, compare it with the pose of the marker recognized after temperature changes, and obtain the Z-value error. Then directly compensate the Z-value error of the marker to the current workpiece’s poses.
- Pay attention to error prevention for the pose error compensation value. If the pose error value after compensation exceeds the threshold, no compensation should be performed.
- If the pose error value after compensation is within the threshold, use the compensated pose value.
