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Automatic sampling of random poses

About 2328 wordsAbout 8 min

This calibration method for three- and four-axis robots is not currently supported.

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. Automatic calibration requires configuring two communication fields respectively.

  • Robot sends visual inspection instructions: needs to be added

    • Photo calculation type (${co}), set to 3, represents a request for automatic calibration

    • Robot pose (${p}), represents Robot sampling pose

  • Automatic calibration sampling sending instructions: need to be added

    • Calibration sampling result (${sr}): represents the sampling result

    • Next sampling pose (${cp}): The next moving position of the Robot to collect calibration samples

(5) Prepare materials required for calibration

  • If you need to use the Calibration Board, please make sure that the Calibration Board is flat and clear, with no obvious scratches or dirt, and no bending or deformation;

2. Calibration information configuration

2.1 Eye to hand

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

  • 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 to 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
* `Calibration method` Select `Random attitude sampling calibration`

  • Get coordinates online Select Yes

  • Automatic calibration of sampling distribution

    • Sampling distribution: This configuration takes the current position as the origin (based on the Robot coordinate system). The user can set the movable sampling range of the Robot on the X/Y/Z positive and negative axes, as well as the angle fixed at the initial position for rotation sampling. It is necessary to ensure that the sampling range is within the camera's field of view, that there is no collision and that there is an appropriate space margin. Units are (mm) and (°).

    • Row/column/layer distribution:

      The number of rows/columns/layers of sample collection points within the movable sampling range of the Robot can be set.

      By default, the row and column layer distribution of 3x3x3 is used. If the accuracy allows, it can be set to a combination with a smaller number of row and row layer distributions such as 2x2x3. It is recommended that the number of any distribution is 2~3. The unit is (pieces)

2.2 Eye in hand

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

  • 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 Random attitude sampling calibration

  • Get coordinates online Select Yes

  • Automatic calibration of sampling distribution

    • Sampling distribution: This configuration constructs a virtual sphere (based on the Robot coordinate system) with the vertical projection point of the Camera on the Calibration Board as the center of the sphere, and the vertical distance between the Camera and the Calibration Board as the radius of the sphere. The user can set the number of sampling points and the moving sampling range (center angle) of the Robot on the sphere along the positive and negative X/Y axes. The end of the Robot always faces the direction of the center of the sphere. It is necessary to ensure that the sampling range is within the camera's field of view, that there is no collision and that there is an appropriate space margin. The units are (pieces) and (°).

    • Sampling distribution:

      Vertical distance between Camera and Calibration Board (mm): The default value is 1500.

      Number of sampling points on the great spherical circle (number): The default value is 5.

      Sampling sphere center angle range (°): The default value is 20.

3. Inspection before calibration

  • 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 to hand, and the Calibration Board needs to be installed on the End-effector to ensure that the Calibration Board is within 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, the Robot accuracy should be calibrated referring to [Calibration Verification] (标定校验.md).

4. Collect samples

4.1 collects multiple sets of Calibration Board and Robot coordinates

This process completes the closed-loop calibration process through Robot triggering. The Robot side needs to focus on Initial Pose calibration and real-time status feedback to ensure the spatial distribution uniformity of sampled data and system robustness.

4.1.1 Robot configuration is defined using Parameter

  • Robot visual inspection sends instructions

    • p: Robot’s current pose coordinates

    • co: Photo calculation type (fixed value 3 means automatic calibration sampling)

  • PickWiz automatically calibrates sampling and sends instructions

    • sr: Sampling result status code (determines the process direction)

    • cp: Coordinate command of the next sampling point (default value indicates termination)

4.1.2 operation process

  1. Initial configuration

    1. Enter the Robot configuration interface and complete single setting:

      • Visual detection sending command and Automatic calibration sampling sending command

      • Enable the current Robot configuration scheme

  2. Start preparation

    1. Select the calibration configuration and enter the sampling page

    2. Robot moves to Initial Pose

      Initial Pose Calibration: The Calibration Board must be located in the central area of ​​the Camera's field of view to ensure uniform distribution of samples.

  3. Automatic sampling phase

    1. Trigger first detection via Robot communication program:

      Different brands require different standard communication procedures, and you need to confirm whether the procedures are provided before entering the market.

      • Robot sends visual inspection instructions containing p=Initial Pose and co=3

      • PickWiz automatically generates a sampling distribution, records the first sampling, and returns the sr status code and the new cp coordinates

    2. Perform the following operations in a loop:

      • Robot moves to a new pose based on the returned sr status code and cp coordinates

      • Robot sends a visual inspection command containing p=current pose and co=3 to PickWiz.

      • PickWiz samples and returns sr status code and new cp coordinates to Robot

      • When Robot determines that cp is the default value (null value), it automatically ends sampling.

      Different calibration sampling results correspond to different signal values, as follows:

      0: Automatic sampling ends successfully

      1: Added sample successfully

      11: The new sample failed. At this time, you can pause and check the failed items in the test results

      12: Automatic sampling ends, but the minimum number of samples is reached. Due to the failure of adding new samples midway, the number of new samples is not enough. You need to check whether the RobotInitial Pose is in the field of view, or reset the automatic sampling distribution Parameter.

      13: Failed to generate sampling pose, confirm whether Robot configuration and sample distribution configuration are correct.

      14: Abnormal startup calibration: Did not enter the automatic calibration sampling page

      15: System error: Contact technical support

4.1.3 test result analysis

The detection is divided into 4 aspects:

Calibration image information: Eye-hand calibration image

Robot detection:

4.2 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.

5. Inspection and analysis of calibration results

If the calibration error exceeds the normal range, you need to locate the cause of the error, click Calibration Diagnosis, refer to [Calibration Result Inspection and Analysis] (标定结果检查与分析.md) to analyze the calibration results, solve the problem and check again until the accuracy of the calibration results meets the Scene requirements.

6. Select Eye-hand calibration configuration

After the calibration process is over, 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.