The below describes the calibration method for Beta RapidSense release. This requires some manual work and ensuring the cal.json file is configured and stored in the directory: ~/.config/rapidsense. In the future RapidSense release, the process will include a GUI and be much more user friendly.
Overview
The current method uses the robot to calibrate the sensors. The robot will need to hold a calibration tag and move through positions with the tag in the sensors field of view during calibration process. The positions will need to be set by the user. A calibration tag will also need to be mounted stationary in the scene in the field of view of the sensors in order for the system to be able to detect if the sensors have shifted out of calibration.
Calibration Requirements
The requirements for calibration are:
Aruco tag mounted off of the robot faceplate
Static Aruco tag placed in the scene which is easily visible to the sensor
Calibration preset with accurate TCP located at the center of the Aruco tag. More details in the cal.json file linked below
cal.json file which has all the camera serial_numbers and it’s corresponding robot target positions for calibration which have the Aruco tag on the robot in the sensor field of view
Setup and Running Calibration Process
To easily generate the cal.json file and save it in /etc/rapidsense/cal.json, there is a calibration_generator.py script which prompts the user for all the necessary information. After the cal.json file has been generated, run the calibration_service.py script and go to localhost:9000/calibration to calibrate all the cameras after rapidsense_app and proxy are running. This script will pull in information from the cal.json file and make the robots move to the cal_targets sequentially, extrinsically calibrating all corresponding cameras. The robot will then return to the home location and all the cameras will save the pose of the static marker placed in the scene. After a successful calibration, all the values will be automatically updated in the cal.json file.
Further details of components can be found in the section below:
Calibration ASCII Interface
'topic': 'Calibrate', 'data': { 'serial_number' : serial_number, 'tcp_pose' : tcp_pose }
The calibration ASCII command { 'topic': 'Calibrate', 'data': { 'serial_number' : serial_number, 'tcp_pose' : tcp_pose } } is used where the serial_number is the camera to be calibrated and the TCP_pose is for the associated robot with the tag mounted on it. These values are sent over the proxy to rapidsense where Aruco detection algorithm finds the markers which allows for calibration of the sensors to occur.
After successful calibration, the pose of the static marker is found and saved in the file cal.json. GetRapidSenseStatus is set as true for the is_calibrated for the corresponding sensor.
Calibration Checking Functionality
During the calibration process, the static Aruco tag in the scene is found and the image is cached to compare against during system running in order to detect when the sensors may have been shifted out of calibration. When it is detected that a sensor may have been shifted out of calibration, GetRapidSenseStatus is set to false for Is_calibrated for that particular sensor in order to warn the user that the calibration needs to be adjusted and run again.