Camera Calibration

Camera - Robot Calibration is the process of synchronizing the coordinate information measured by the camera with the coordinate information of the robot.

With Calibration, the camera can accurately move to the location of the measured item, and it can accurately measure dimensions in terms of length. During Calibration, a checkerboard with predefined design information is used. The method currently offered by Doosan Robotics is StandAlone calibration, and the elements required for this calibration are four robot poses taught based on the camera image of the checkerboard shot from the shooting position and tool tip.

Caution

During calibration, it is necessary to align the camera lens and the checkerboard in parallel as much as possible. In addition, when performing calibration, the calibration board must be placed at the surface height of the item to be measured. If the height of the checkerboard during calibration differs from the surface height of the item to be measured, it can cause failure to detect the item or decrease measurement accuracy.

Additional Functions available with the SVM

The Live screen is displayed on the Jog

If the Vision license is entered, a live image can be viewed in the Jog tab. The user can operate the robot while viewing the live image.

Added Vision category to Peripheral

SVM Calibration Board Download

The SVM Calibration Board can be downloaded from [https://lab.doosanrobotics.com/en/Index Robot LAB – Resources – Tech Data – Reference] after logging in.

No.	Item	Description
1	Camera Calibration	Enables Camera - Robot Calibration function. After the Camera Calibration function is enabled, the Camera Calibration Image button is enabled.
2	Live/Shoot Image	The Live/Shoot Image can be checked. To ensure proper camera calibration, a checkerboard is placed as follows: The calibration image provided by Doosan Robotics is a 15 mm checkerboard. [Download Page] Place the checkerboard at a distance of 300 mm~600 mm from the SVM. The checkerboard and the camera must be parallel (less than 1°). Use the Grid function of the image to position the checkerboard as follows: Place the center point where the center arrow “O” is pointing on the red cross at the center of the camera image. Align the checkerboard vertically and horizontally along the green guide lines to prevent rotation.
3	Lighting Setting/ Save Shoot Image/ Shoot Pose	Adjust the focus, brightness and lighting to display the edge of the checkerboard clearly. Press the Shoot button to check edge information. Press the Apply Reference Image button to save the camera information and Shoot Pose.
4	Camera Calibration Image	Run checkerboard corner point detection. Press the View Image button to check the detection results. If detection fails, the checkerboard pattern is not displayed on the View Image button. Note If the calibration data performed by DART-Vision is found, calibration cannot be executed from the teach pendant. At this time, if you want to proceed with the calibration in the teach pendant, you must delete the calibration data performed in DART-Vision.
5	Load TCP Setting	Sets the information of the Tool currently equipped on the robot as TCP. A probe type Tool is recommended. If a gripper is used, it is recommended to make measurements with a probe-shaped item grabbed as in the following image: For information about measuring the tool center position, refer to the Workcell Manager End Effector Management section of the User Manual.
6	Obtain PointA - PointD Points	Obtains the robot pose [x, y, z, rx, ry, rz] of PointA - PointD. If the base plane of the robot and the workspace are on the same plane, the tool center point of the robot is aligned based on the base axis. Robot poses corresponding to PointA-PointD are acquired with the aligned axis unchanged using plane lock and axis lock of the Constraints Motion button in the robot cockpit. Refer to Robot User Manual - Jog - Setting Screen - Align according to Base Axis for how to align the base axis with the TCP end. If the workspace where the target item located is slanted, unlike the base plane of the robot, align the tool center point according to a virtual vector area. Refer to Robot Manual – Jog – Setting Screen – Align according to Target Point. Perform direct teaching of corner points on the checkerboard in the order of Ⓐ, Ⓑ, Ⓒ and Ⓓ with the end of the robot tool to enter the coordinates of each point. Tap the Move To button to move to the corresponding point. Press the Reset button to reset robot coordinates. If the end of the tool fails to accurately pinpoint the corner points of the checkerboard, point deviation occurs.
7	Alignment with Robot Coordinate	Run the camera - robot coordinate matching calculation. After calculation is completed, the results are displayed. If successful,save the Calibration information in the camera. To save the Calibration information in the UI, press the Confirm button on the top of the Workcell Manager. Success ( ) / Failure ( ) Success Criteria • All grid patterns of the checkerboard must be displayed on the image. • Dark grid patterns of the checkerboard must be positioned on the top/bottom left. • Check whether all corner points are detected using View Image. • TCP information identical to the information of the tool equipped must be set. • Enter corner points of ABCD of the checkerboard with direct teaching to the robot. • Teach the robot tool the exact positions of ABCD corner points of the checkerboard. • The checkerboard position must not change during direct teaching. Failure Criteria • If all corner points of the checkerboard are not detected. • If the direct teaching order of ABCD corner points of the checkerboard is incorrect. • If the set TCP information does not match the information of the Tool equipped. • If the direct teaching of corner points of the checkerboard is not accurate. • If the ABCD coordinates measured by the camera are different from the ABCD coordinates taught to the robot by direct teaching (calibration fails if a deviation of more than 5 mm occurs). Items to Check Upon Failure • Check the position/direction of the checkerboard. • Check whether edges of the checkerboard are clearly displayed. • Check whether direct teaching was performed in the order of ABCD. • Check whether the TCP setting is correct. • Check whether the checkerboard print was moved after Camera Calibration Image. • Check whether the ABCD corner points of the checkerboard were taught accurately.
8	Import Calibration Data	Imports calibration data that succeeded in existing vision works. • Select a vision work to import the calibration data and press the import button to save the corresponding calibration data.
9	Set	Sets the Workcell Item loaded on the left of the Set button to the current tool center point.