System Calibration

This section will guide you to calibrate the probe and, optionally, your robot, and how to match the measurement system with your real setup.

These steps only need to be done once but they are important to obtain accurate results.

If your measurement system is not accurate enough to calibrate a robot (such as the HTC Vive trackers), you should skip the robot calibration step. However, make sure to follow the steps in the Setup for Offline Programming section.

Robot calibration

This section describes how to automatically calibrate your robot using RoboDK TwinTrack and your measurement system. Robot calibration allows you to improve robot accuracy to up to 0.150 mm when you generate programs offline or using TwinTrack teach by demonstration tools in RoboDK (the level of accuracy highly depends on the quality and size of the robot).

It is recommended to perform the robot calibration after you build your robot cell, or you make major modifications (such as changing the payload of your tool). This helps obtaining the best accuracy.

Before you begin the calibration, you can model your cell in RoboDK to automatically avoid collisions. You can use basic geometries such as planes or cubes to avoid unwanted areas. You can also limit the joint space of the robot.

You can select TwinTrack➔Calibrate robot to start the robot calibration procedure.

This operation will guide you to calibrate the robot, including the automatic generation of points for calibration and validation. RoboDK can automatically generate points that are visible by the tracker.

The robot calibration procedure requires taking around 200 measurements. The procedure starts by taking some measurements around the home position of the robot.

Once the setup is ready and the communication with the robot is properly established, the calibration procedure should take 15-30 minutes.

The system requires no special fixtures or accessories; it simply tracks the position of the tool with respect to the tracker reference.

It’s fine if you miss some measurements because the targets are not visible.

Probe calibration

It is important to properly calibrate the tip of your probe and make sure it is accurate within your desired tolerances.

Calibrating the tip of the probe is accomplished by moving the tip around a static point.

Select TwinTrack➔Calibrate/Validate Probe Tip to start the tool calibration.

In this case, because we are using the Creaform HandyProbe, you can calibrate the probe using Creaform VXElements software and validate it using RoboDK.

To validate the tip of your probe you simply need to move around a static point and RoboDK will display the accuracy.

Setup for Offline Programming

This section guides you through the procedure to match the real measurement system with your simulation offline. This lets you build a digital twin that shares a common reference frame between your simulation and the real setup.

You can use the TwinTrack teach by demonstration features without a calibrated robot or even a real robot. This means you can simulate and program your robot offline only with your measurement system before you have access to the real robot.

You simply need a part with a well-defined coordinate system that you can use as a reference. The reference must be the same offline and in the real setup.

Once you have the measurement system and your part ready (real or simulated) you can follow these steps to define the coordinate system of your measurement device:

1.Define the part’s coordinate system with your real robot using the Define Reference Frame option from the Utilities menu. If you don’t have a real robot, use an approximated position of the coordinate system in your RoboDK simulation. You can repeat this procedure later with a real setup.

2.Right click the coordinate system of your part (or the coordinate system the jig/fixture is attached to).

3.Select Update the Measurements Reference.

4.Follow the instructions on the screen to teach 3 points of your real part using the probe. These 3 points define the coordinate system in the right order: the origin, a point on X+ and a point on Y+.

The measurement system will be updated accordingly, and you can proceed to teach points, curves or other coordinate systems.