Robot Calibration (Laser Tracker)
There are four sets of measurements that are required to successfully accomplish robot calibration:
1.Base setup: six measurements (or more) moving axis 1 and 2 are required to place the calibration reference with respect to the robot. SelectShowin the calibration settings window and the robot will move along the sequence.
2.Tool setup: seven or more measurements are required to calibrate the tool flange and the tool targets (moving axis 5 and 6). SelectShowand the robot will move along the sequence.
3.Calibration measurements: 60 measurements or more are required to calibrate the robot. These measurements can be randomly placed in the robot workspace and free of collision with the surrounding objects.
4.Validation measurements(optional): as many measurements as desired can be used to validate the robot accuracy. These measurements are used only to validate the accuracy of the robot and not to calibrate the robot.
The first two sets of measurements are automatically generated by RoboDK. SelectShowand the robot will follow the sequence (as shown in the following images). If the sequence needs to be changed, selectMeasureand export the calibration measurements as a CSV file by selectingExport data。This file can be edited using an Excel sheet and re-imported by clickingImport data。
The last two sets of measurements (calibration and validation) can be generated using the macro script called
Create measurements。这个宏脚本将自动添加到station when we start the robot calibration project. Double click the macro to execute it. This macro is a Python program that guides the user to define the following settings:
●Number of measurements: The number of measurements to generate. By default, 80 measurements are used because a minimum of 60 measurements is required for robot calibration.
●Reference position: The reference position must be a position of the robot where the tool is facing the tracker with visible targets.
oJoint limits: The lower and upper joint limits must be provided.
oCartesian limits: We can provide Cartesian limits (X,Y,Z values) with respect to the robot reference frame.
The script automatically generates measurements where the tool is facing the tracker as well as respecting the joint and Cartesian constrains. A rotation of +/-180 deg around the tool is permitted around the direction that faces the tracker at the reference position. Furthermore, the sequence of joint movements is free of collision and inside the measurement workspace (if the workspace is set to be visible).The following image shows the summary that is presented to the user before the automatic sequence starts. It may take up to 5 minutes for the sequence to finish.
If desired, we can modify the script by right clicking theCreate measurementsscript and selectingEdit script, then, modify additional parameters of the algorithm. The script automatically saves the user input as station parameters. We can view, edit or delete these settings by right clicking the station and selectingStation parameters, as shown in the next image.
A new message will pop up once the algorithm finishes. We can select “Calibration” to use the 60 measurements for robot calibration. We can re-execute the same script to generate another set of measurements for validation. This step is optional but 80 measurements are recommended for validation purposes.
Finally, it is also possible to import configurations that have been selected manually by selectingImport data(inside theMeasuremenu). We can import a CSV or a TXT file as an Nx6 matrix, where N is the number of configurations.
