Industrial robots are highly repeatable, but not accurate. Therefore, the accuracy of an industrial robot can be improved through robot and tool calibration. Without calibration, robot accuracy highly depends on the robot brand and model. With robot calibration, you can accurately calculate the tool center point (TCP) and calibrate the robot kinematic parameters. Robot accuracy can be improved by a factor of 2 to 10.
RoboDK TwinTool can be used to calibrate and validate the tool center point (TCP). The TwinTool can accurately calibrate the TCP for tools with spherical or conical geometries.
1.Spherical tools➔The center of the tool is calibrated
2.Conical tools➔ The tip of the tool is calibrated
It is required to install the RoboDK TwinTool App and have a compatible sensor to perform the automated robot calibration.
Make sure to have the following:
1.One or more industrial robot arms.
2.A compatible dial indicator (also known as LVDT or linear gage).
3.RoboDK software must be installed and an appropriate license for automated robot calibration must be available.
4.You need compatible robot drivers for your robot controller.
5.Install the RoboDK TwinTool App:
a.Download the RoboDK TwinTool App.
b.Double click the file to install the app and open it in RoboDK.
c.Alternatively, you can unzip the contents in C:/RoboDK/Apps/.
d.Select Tools➔Apps and double click on TwinTool to see the toolbar and menus on the right.
To calibrate the TCP using the linear gage sensor, we need to load the robot in RoboDK and make sure the sensor and the robot are connected. We can optionally model the cell by adding the 3D models of objects and tools. This will allow to automatically avoid collisions.
1.Load the robot:
a.Select File➔Open online library. The online library will show up in RoboDK.
b.Use the filters to find your robot.
c.Select Download to automatically load the robot in your RoboDK station.
d.Alternatively, download the robot file directly from the online library (https://robodk.com/library) and open the file with RoboDK (.robot file).
2.Connect the sensor:
a.Connect the sensor to your computer.
b.Select TwinTool➔ Measure.
c.Make sure the sensor is measuring and measurements are stable.
3.Connect the robot:
a.Select Connect➔Connect robot.
b.Enter the robot IP and port.
4.Select Get Position from the robot connection panel. This step will update the position of the robot in RoboDK.
You can optionally follow these steps to properly model the 3D environment of you cell.
1.Load the 3D model of your tool and create a tool in RoboDK. More information in the create tool section.
2.Load any 3D files to model the cell. You can load 3D STEP, IGES, STL files. More information in the getting started section.
To start the calibration procedure, simply select TwinTool➔ TwinTool Wizard.
After launching the wizard, you will be guided through the Calibration, Validation, or Simulation setups. This includes setting up the connection to the sensor, ensuring a valid state of the robot and review of key parameters.
After the calibration sequence completes, we’ll see a chart showing the calibration results. RoboDK calculates the tool center point (TCP) with and without robot calibration.
1.TCP without robot calibration: The TCP is calculated using the nominal robot kinematics.
2.TCP with robot calibration: The TCP is calculated using accurate robot kinematics. The measurements are used to calibrate the robot and an accurate robot TCP. This method can provide better accuracy results but requires program filtering to accurately account for robot errors. More information in the Program Filtering section.
Once we have run the calibration sequence, we can run some validation tests. These validation tests can be in the same location of the sensor or different locations.
Select Validate from the Wizard. The calibration data will be used to calculate the TCP (excluding robot calibration).
The calculated TCP will be displayed, and some statistics will provide estimated errors for the calculated TCP.
Select Validate from the toolbar to start the validation sequence.
Select Show Statistics to display a summary and some statistics about the results. These statistics correspond to the planar errors detected by the sensor.
This section describes additional settings and options that you can modify to better customize your calibrations and test the robot accuracy.
Select TwinTool➔Advanced Calibration Settings to open the complete list of advanced settings. Most of these settings are prompted and set through the Wizard.