LED Dynamic Marker and Tracking Algorithm for External Camera Positioning

A particular type of dynamic LED visual marker was designed in this study to address the shortcomings of the existing visual marker of the multi-robot positioning system that uses an external camera. Moreover, this dynamic LED visual marker was proposed using the tracking and positioning algorithm. This marker can distinguish and detect the positions of all the robots with LED visual markers in the image. Dynamic LED visual markers use colourful LEDs as carriers, which are arranged in the order of red, green and blue colours to communicate information. Moreover, a coding rule based on ternary trees was also developed. The tracking and positioning algorithm applied the dual-thread design of the tracking and detection threads. The former completes coding verification using the Kalman filtering algorithm while tracking the LED markers in images. The latter positions LED and reads encoding information by detecting the initial signal. Such dual-thread design effectively decreases the computation workload and emphasises on accurate positioning and fast response. The experimental results suggest that the proposed visual marker has a smaller volume and a more extended sphere of influence than the existing ARTag visual marker method. The tracking and positioning algorithm completes the visual positioning task of a multi-robot system with high accuracy and robustness.