Eye to hand Calibration for 3-Axis Robots
This article describes how to perform eye-hand calibration for a 3-axis Robot in an Eye to hand scenario.
1. Needle-Tip Tool Touchpoint Calibration
1.1 Preparations Before Calibration
Before performing eye-hand calibration, complete the following preparations:
（1）Complete the hardware setup of the 3D vision guidance kit
Please refer to 3D Vision Guidance Kit Hardware Setup to complete the installation and connection of the Robot, Camera, and industrial PC
（2）Create a new Project and a new task
Please refer to Project Operation Guide and task Operation Guide to create a new Project and task
（3）Complete Camera connection and Parameter adjustment, and configure it in the task information
Please refer to Camera Connection and Parameter Adjustment Guide to connect the Camera, perform camera imaging quality adjustment, verify Camera accuracy, and configure it in the task information
（4）Complete Robot communication configuration
Please refer to Robot Configuration and Communication Operation Guide to establish the robot communication connection between the Robot and PickWiz
（5）Prepare the materials required for calibration
Ensure that the Calibration Board is flat and clear, with no obvious scratches, dirt, bending, or deformation
If the calibration method is Random Pose Sampling Calibration, ensure that the Calibration Board is placed on the work platform and is within the Camera field of view.
1.2 Calibration Information Configuration
Go to the eye-hand calibration interface, click Add Eye-Hand Calibration, and enter the calibration information configuration interface
Calibration Namecan be used to name the current calibration configurationCalibration IDis used by the Robot to switch calibration configurationsCamerais the IP address of the currently connected CameraCamera Brandis the brand of the currently connected CameraRobot Typemust be consistent with the Robot type in Robot ConfigurationFor
Camera Installation Method, selectEye-to-HandFor
Calibration Board Type, select the current Calibration Board type
A suitable Calibration Board is determined mainly by the Robot type and the Camera mounting height. Please refer to the table below and select the proper Calibration Board based on the actual application scenario.
| Robot Type | Camera Mounting Height | Select Calibration Board |
|---|---|---|
| Six-axis Robot | Below 0.5 m | A6 multi-concentric-circle Calibration Board |
| Below 1.5 m | A5 multi-concentric-circle Calibration Board | |
| 1.5 m -- 2.5 m | A4 multi-concentric-circle Calibration Board | |
| Above 2.5 m | A3 multi-concentric-circle Calibration Board | |
| Three-axis/Four-axis Robot | Below 0.5 m | A6 multi-concentric-circle Calibration Board |
| Below 1.5 m | A5 multi-concentric-circle Calibration Board | |
| 1.5 m -- 2.5 m | A4 multi-concentric-circle Calibration Board | |
| Above 2.5 m | A3 multi-concentric-circle Calibration Board |
For
Calibration Method, selectNeedle-tip Tool Touch CalibrationIf the Robot has a corresponding calibration program and needs to run it to send the pose to PickWiz while sampling the Calibration Board, then for
Get Coordinates Online** selectYes; if the Robot does not have a corresponding calibration program, you need to manually enter the pose of the Robot end tool while sampling the Calibration Board, then forGet Coordinates Online**selectNo.
1.3 Pre-calibration Checks
- Ensure that the Robot base is securely installed
Before performing eye-hand calibration, carefully check the installation of the Robot base. If the Robot base is not securely installed, the Robot may shake noticeably during motion, affecting Robot accuracy and therefore the calibration result.
Check whether the Robot base installation meets the requirements as follows:
First, the surface on which the Robot base is installed must be flat and clean;
Second, operate the Robot at 100% speed with large translation or rotation movements and observe whether there are signs of shaking. If shaking occurs, readjust and secure the Robot base to ensure that no displacement or tilting occurs during Robot motion;
Third, check whether the Robot body and base are tightly connected, and tighten the screws to prevent loosening.
- Ensure that the Camera and its bracket are securely installed
Before performing eye-hand calibration, carefully check the installation of the Camera and its bracket. If the Camera or bracket is not securely installed, camera imaging quality may be affected, which in turn affects the calibration result.
Check whether the Camera and its bracket installation meets the requirements as follows:
First, check whether the Camera bracket is a machined part. Aluminum profile material should be avoided for the bracket;
Second, shake the bracket and observe whether there is any obvious wobble. If so, readjust and secure the bracket;
Third, shake the Camera and observe whether there is any obvious wobble to ensure that the Camera is securely installed.
- Ensure that the Calibration Board is stably placed within the Camera field of view
For the Eye to hand Camera mounting method, install the Calibration Board on the end tool and ensure that the Calibration Board is within the Camera field of view.
- Ensure that Robot accuracy meets the Project requirements
If Robot accuracy does not meet the Project requirements, please refer to Calibration Verification to correct Robot accuracy.
1.4 Collect Samples
1.4.1 Collect Calibration Board and Robot coordinates
（1）Adjust the position of the Calibration Board, place it within the workpiece placement area, and click Start Sampling.
（2）Click Add Sample. If the sample is valid, a Saved Successfully message is displayed; if the sample is close to an existing sample, the sample is invalid and the save fails.
（3）Check the inspection results. If all inspection items are shown as green icons, coordinate axes and feature points appear in the visualization window, and all circle centers are green, the current Calibration Pose meets the requirements.
The inspection consists of 4 aspects:
1.4.2 Touch the Calibration Board with the Needle Tip
（1）Click Start Sampling, control the Robot to move, and touch the center of each corresponding concentric circle with the needle tip in the numerical order shown in the visualization window.
（2）Click New Sample to collect the Robot coordinates at the touchpoint moment.
（3）Repeat the above steps to collect at least 3~6 concentric-circle touchpoint samples.
- Click
Next
1.4.3 [Optional] Add a new calibration position
During the calibration sampling stage, the system uses a single-pose calibration mode by default. However, in specific application scenarios, it can be extended to a multi-position calibration strategy to improve calibration robustness and system adaptability under complex working conditions:
To address accuracy deviations caused by changes in depth of field in wide-angle vision systems, layered sampling along the Z-axis can effectively balance the error distribution across different focal planes;
For work environments with limited space, when a single Calibration Board placement cannot complete the collection of more than three feature points, multiple Calibration Board placements and separate sampling can be used to cumulatively meet the minimum sample quantity requirement.
Click New Position to add a new calibration position, then repeat 1.4.1 Collect Calibration Board and Robot coordinates and 1.4.2 Touch the Calibration Board with the Needle Tip to collect calibration samples and perform Calibration Board touchpoint operations.
1.4.4 Calculate the Calibration Result
Click Calculate Result. PickWiz calculates the calibration result based on the collected samples. If the calibration error does not meet the requirements, perform Calibration Result Inspection and Analysis.
1.5 Select the eye-hand calibration configuration
After the Calibration Process is completed, return to the Run Configuration interface, click Task Information, click the Eye-Hand Calibration drop-down list, and select the corresponding eye-hand calibration configuration.
