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Eye in hand three-axis Robot calibration

About 2034 wordsAbout 7 min

This article introduces how to perform Eye-hand calibration in the three-axis RobotEye in hand (Eye in hand) Scene.

Eye in hand (Eye in hand) three-axis Robot calibration is recommended to use the needle point tool poke point calibration method

1. Point tool calibration

1.1 Preparation before calibration

Before Eye-hand calibration, the following preparations need to be made:

(1) Complete the hardware construction of the 3D visual guidance kit

Please refer to [3D Vision Guidance Kit Hardware Construction] (../常用操作/3D视觉引导套件硬件搭建.md) to complete the installation and connection of Robot, Camera and industrial computer

(2) Complete the new project and new Task

Please refer to Project Operation Guide and Task Operation Guide to create a new project and Task

(3) Complete the Camera connection and parameter adjustment and configure the Task information

Please refer to [Camera Connection and Parameter Adjustment Guide] (../常用操作/相机连接与调参指南.md) to connect the Camera, adjust the Camera imaging quality, verify the Camera accuracy, and configure the Task information

(4) Complete Robot communication configuration

Please refer to Robot Configuration and Communication Operation Guide to establish communication between Robot and Pickwiz

(5) Prepare materials required for calibration

  • Please ensure that the Calibration Board is flat and clear, with no obvious scratches or dirt, and no bending or deformation.

  • If the calibration method is random attitude sampling calibration, please ensure that the Calibration Board is placed on the work platform and within the camera's field of view.

1.2 calibration information configuration

Enter the Eye-hand calibration interface and click Add Eye-hand calibration to enter the calibration information configuration interface.

For reference only, the picture shows the Scene of Eye to hand, the Eye in handScene is executed as described

  • Calibration name allows you to name the current calibration configuration yourself.

  • Calibration ID is used by Robot to switch calibration configurations

  • Camera is the IP address of the currently connected Camera

  • Camera Brand is the brand of the currently connected Camera

  • Robot type is consistent with the Robot type in Robot configuration

  • Camera installation method select Eye in hand

  • Calibration Board Type selects the current Calibration Board type

The appropriate Calibration Board is mainly determined by the Robot type and Camera height. Please refer to the following table to select the appropriate Calibration Board according to the actual scene requirements.

Robot typeCamera installation heightSelect Calibration Board
six-axis Robot Below 0.5 metersA6 Multi-Concentric Circle Calibration Board
Below 1.5 metersA5 Multi-Concentric Circle Calibration Board
1.5 meters -- 2.5 metersA4 Multi-Concentric Circle Calibration Board
2.5 meters and aboveA3 Multi-Concentric Circle Calibration Board
three-axis/four-axis Robot Below 0.5 metersA6 Multi-Concentric Circle Calibration Board
Below 1.5 metersA5 Multi-Concentric Circle Calibration Board
1.5 meters -- 2.5 metersA4 Multi-Concentric Circle Calibration Board
2.5 meters and aboveA3 Multi-Concentric Circle Calibration Board

  • Calibration method Select Point Tool Poke Point Calibration

  • If the Robot has written a corresponding calibration program, and when sampling the Calibration Board, the Robot needs to run the calibration program and send the pose to PickWiz, then Get coordinates online** select Yes; if the Robot has not written a corresponding calibration program, and when sampling the Calibration Board, you need to manually enter the pose of the RobotEnd-effector, then Get the coordinates online **Select No.

1.3 Inspection before calibration

For reference only, the picture shows the Scene of Eye to hand, the Eye in handScene is executed as described

  • Make sure the Robot base is firmly installed

Before performing eye-hand calibration, you should carefully check the installation of the Robot base. If the Robot base is not firmly installed, the Robot will shake significantly when it moves, affecting the Robot's accuracy and thus the calibration results.

Follow the steps below to check whether the installation of the Robot base meets the requirements:

First, the surface on which the Robot base is installed must be flat and clean;

Second, control the Robot to translate or rotate at a large speed at 100% speed, and observe whether there are signs of shaking in the Robot. If there is any shaking, please readjust the fixed Robot base to ensure that problems such as displacement and tilt do not occur when the Robot moves;

Third, check whether the Robot body and the base are tightly connected, and tighten the screws to prevent them from loosening.

  • Make sure the Camera and its bracket are securely installed

Before performing eye-hand calibration, you should carefully check the installation of the Camera and its bracket. If the Camera and its bracket are not firmly installed, it will affect the camera imaging quality and thus the calibration results.

Follow the steps below to check whether the installation of the Camera and its bracket meets the requirements:

First, check whether the Camera bracket is a machine-mounted Target. The material of the bracket should avoid aluminum profiles;

Second, shake the bracket and observe whether there is obvious shaking in the bracket. If there is any shaking, please readjust the fixed bracket;

Third, shake the Camera and observe whether there is obvious shaking in the Camera to ensure that the Camera is installed securely.

  • Make sure the Calibration Board is placed smoothly in the Camera's field of view

The camera installation method is Eye in hand, and the Calibration Board needs to be placed on the work platform and within the camera's field of view.

  • Ensure that Robot accuracy meets project usage requirements

If the Robot accuracy does not meet the project usage requirements, please refer to [Calibration Verification] (标定校验.md) to correct the Robot accuracy.

1.4 Collect Sample

For reference only, the picture shows the Scene of Eye to hand, the Eye in handScene is executed as described

1.4.1 collects Calibration Board and Robot coordinates

(1) Adjust the position of the Calibration Board, place it in the area where the Target is placed, and click Start Sampling.

(2) Click Add Sample. If the sample is valid, a message Save Successfully will pop up; if the sample is close to an existing sample, the sample is invalid and a message indicating failed saving will pop up.

For reference only, the picture shows the Scene of Eye to hand, the Eye in handScene is executed as described

(3) Test results. If each test item is a green icon, the coordinate axis and feature points appear in the visualization window, and the center of the circle is green, it means that the current Calibration Board posture meets the requirements.

Camera detection is divided into 4 aspects:

1.4.2 Tip Touch Calibration Board

(1) Click Start Sampling, control the Robot to move, and follow the numerical order marked in the visualization window, and the needle tips touch the centers of the corresponding concentric circles respectively.

(2) Click Add Sample to collect the Robot coordinates at the time of stamping.

(3) Repeat the above steps to collect at least 3~6 concentric circle poke point samples.

  • Click Next

1.4.3 [Optional] Add new calibration position

In the calibration sampling phase, the system defaults to a single attitude calibration mode, but it can be expanded to a multi-position calibration strategy in specific application scenes, which improves the calibration robustness and system adaptability under complex working conditions:

  • To address the problem of accuracy deviation caused by changes in depth of field in wide-angle vision systems, layered sampling in the Z-axis direction can effectively balance the error distribution of different focal planes;

  • For working environments with limited space, when a single Calibration Board deployment cannot complete the collection of more than 3 feature points, the Calibration Board can be deployed in multiple locations and sampled in batches to meet the minimum sample size requirements through accumulation.

Click Add Position to add a calibration position, repeat **1.4.1 to collect Calibration Board and Robot coordinates ** and **1.4.2, touch the Calibration Board ** with the tip of the needle to collect the calibration sample and poke the Calibration Board.

For reference only, the picture shows the Scene of Eye to hand, the Eye in handScene is executed as described

1.4.4 Calculate calibration results

Click Calculation Result and Pickwiz will calculate the calibration result based on the collected samples. If the calibration error does not meet the requirements, please perform Calibration Result Check and Analysis.

1.5 Select Eye-hand calibration configuration

After the calibration process is completed, return to the Run Configuration interface, click Task Information, click the drop-down box of Eye-hand calibration, and select the corresponding Eye-hand calibration configuration.