Robot Base Calibration with RoboCalc

Background:

Industrial robots are used for automation in the manufacturing sector, such as the automotive industry, to automate work processes.

Typical tasks include precisely aligning, gluing, welding, or riveting car body parts. To do this, knowledge of the relative position between the robot (especially the tool) and the component—that is, the robot parameters—is essential.

Challenge:

Due to various factors—such as imprecise setup or inaccurate calibration—the actual robot pose does not match the planned pose. This results in increased effort required to retrain points from the offline programming.

However, standard methods for determining the current pose parameters (three translations and three rotations in space) only calculate these for a specific robot position, which is often outside the robot’s workspace. As a result, the accuracy of the workpoints within the robot’s workspace varies greatly and may fall well outside the required tolerance.

Solution:

Using RoboCalc, an add-on module for the open-source software OpenIndy, both the six parameters of the base (position and orientation) and the three parameters (position) of the tool can be determined in a single step.

Procedure:

1. Secure the prism in the TCP
2. Calibrate in the fixture using a laser tracker (typically via the reference holes
3. Teach-in and simultaneous measurement (with the LT) of approximately 10 robot positions in the workspace
4. Calculate values using RoboCalc
   • Select the robot manufacturer and program using the taught points
   • Select measurement points
   • Release the base and tool
5. Transfer parameters to the robot
6. Verify the entered base and tool

Achieved Benefit:

By averaging the deviations during compensation, these parameters apply not only at a single point but across the entire measurement range. This increases accuracy and significantly reduces the effort required for re-calibration.

Another advantage, particularly for rotary tables or drums, is that the parameters can be determined more quickly than with conventional methods.

Please feel free to contact us directly to discuss this!