Calibration Procedure for ETH Calibration Using the Multiple Random Board Poses Method

This section will guide you through the ETH calibration using the multiple random board poses method.

Calibration Preset

1. Open Mech-Vision, click the Camera Calibration (Standard) button in the toolbar. The Calibration Preset window will be prompted.

2. In the Please select calibration mode window, select the Start a new calibration process radio button, and then click the Next button.

   

3. In the Please select a calibration setup window, select the Eye to Hand radio button, and then click the Next button.

   

4. In the Select a method to add calibration points window, select the Multiple random board poses radio button, and then click the Start calibration button.

   

Till now, the calibration preset work is completed and you will enter the calibration procedure.

Calibration Procedure

Note

The following part introduces the calibration steps by taking a connected robot as an example. If you use a special robot, please refer to Manual Calibration Procedure.

Connect to the Camera

1. In the Connect to Camera window, find the camera to connect in the Detected Cameras list, and click the Connect button.

   

2. After the camera is connected, click the Capture Live or Capture Once button.

   

3. In the right panel of the calibration interface, ensure that the captured image meets the calibration requirements and click the Next button.

   Note

   If the captured image does not meet the calibration requirements, you need to open the Mech-Eye Viewer software to adjust the 2D and 3D scanning parameters and re-capture images.

Mount the Calibration Board

1. In the Mount Calibration Board window, specify the calibration board type according to its model nameplate and click the Confirm button.

2. Make sure that the calibration board has been attached to the robot flange securely, and then click the Confirm button.

3. Use Mech-Viz to control the robot to move to the center of the camera’s field of view (the red rectangle in the 2D image), and then click the Confirm button.

4. After all operations are completed, click the Next button.

Check Camera Intrinsic Parameters

1. In the Check Camera Intrinsic Parameters window, click the Check Camera Intrinsic Parameters button.

2. Confirm the results of the camera intrinsic parameters check.

   • If the camera intrinsic parameters check passes, click the Next button.

   • If the camera intrinsic parameters check fails, adjust detecting parameters by drawing aid circles or manually adjusting the detecting parameters, and then click the Check Camera Intrinsic Parameters button again.

Generally, when the lighting conditions are good and the camera parameters are appropriate, the intrinsic parameter check will pass by simply keeping the default values. The following figure shows a successful detection of the feature points.

• Draw aid circle

To draw an aid circle, click the Start Drawing Aid Circle button, draw a circle coinciding with a circle in the calibration board. After that, the detecting parameters of the circles should change.

Tip

If the calibration circles are too small to be selected easily, the user could right click the 2D image, clear the Fit to Window check box, and select Normal Size. Start drawing aid circles after adjusting the size of the image.

• Manually adjust the detecting parameters

To manually adjust the detecting parameters, click Edit Detecting Parameters and change the values of detecting parameters accordingly.

• Adjust camera parameters

If the feature points are still not detected, please adjust the camera settings according to the on-site operating conditions. Detailed information can be found in Mech-Eye Viewer.

Set Move Trajectory

1. In the Set Move Trajectory window, specify the Calibration Height Range parameter.

   

   Tip

   The Calibration Height Range parameter should be set according to the recommended working distance range of the camera and the size of the robot’s working space.

2. Click the Detail Setting button, and set detailed parameters such as Height Parameters, Bottom Layer Lengths, Top Layer Lengths and Move Grid per Layer.

   

3. Click the Auto Generate Move Trajectory button, and the program will automatically generate each waypoint of the path. A dialog box will pop up after completion, as shown in the following figure.

   

4. Confirm that waypoints are reasonable and will not collide with obstacles in the environment in Mech-Viz.

   Open Mech-Viz, click the Robot tab, select the current robot type and click the Sync Robot button. Then check the distribution of the waypoints in the auto-generated path, as shown in the following figure. You must check that the path is reasonable and will not collide with obstacles in the environment!!!

   

5. Return to Mech-Vision, click the click the Next button, as shown in the following figure.

   

Add Marker-Images and Poses

1. In the Add Marker-Images and Pose window, select the Save Images check box, check the type of the connected robot and then click the Move Robot along Trajectory and Add Board Images button.

   

2. Read the safety window carefully and click the OK button after you make sure that the operation environment is safe.

   

3. Wait until the robot finishes moving along the preset path and the camera finishes capturing images on all waypoints. Captured images can be seen in the right viewer during this process.

   

   Attention

   • Please stay away from the robot working area to keep safe.

   • Clicking the Stop Robot button can exit the calibration process. But the robot will not stop until it finishes the current waypoint. In case of emergency, please tap the emergency stop button on the robot teach pendant to stop the robot immediately.

4. After all images are captured, confirm that the currently recognized calibration point meets the requirements, and then click the Next button.

   

Tip

If not, please manually add the calibration points by moving the robot through the teach pendant or Mech-Viz software. Select the Manually Add More Images check box, and click the Add Single Calibration Board Image And Record Pose button to collect images again.

Attention

During the calibration process, a prompt box may appear, indicating that a measurement deviation has been detected, as shown in the following figure. It is recommended to re-calibrate the camera intrinsic parameters and check whether the robot loses its absolute accuracy. You could choose to continue this calibration process by clicking the Ignore button. However, the calibration accuracy cannot be guaranteed.

Calculate Camera Parameters

1. In the Calculate Camera Parameters window, click the Calculate Camera Parameters Results button to confirm and save the calibration data accordingly, as shown in the following figure.

   

2. Click the Display Point Cloud in Mech-Viz button.

   

3. Enter Mech-Viz, select the Robot tab. Click the Configure Robot button, and in the pop-up that appears, choose the correct robot type, as shown in the following figure.

   

4. In Mech-Viz, select the Scene tab, and adjust the ground height accordingly, as shown in the following figure.

   

5. In the simulation interface of Mech-Viz, confirm that the point cloud of the calibration board are qualified, as shown in the following figure.

   

6. Return to Mech-Vision, click the Save button to save the calibration results to a specified project’s directory.

(Conditional) Adjust Camera Parameters

Note

For 4-axis robots or other rotation-constrained robots, extrinsic parameters at Z axis cannot be calibrated and need to be modified manually.

In the Adjust Camera Parameters window, select the Adjust Z-axis Translation radio button, set the Z-axis Translation parameter and then click the Save button to save the calibration results to a specified project’s directory.

Alternatively, in the Adjust Camera Parameters window, select the Adjust All Extrinsic Parameters radio button, adjust extrinsic parameters, and then click the Save button to save the calibration results to a specified project’s directory.

Till now, the calibration procedure is completed.