Overview of the winning approaches in BCI Controlled Robot Contest in World Robot Contest 2021:Calibration-free SSVEP

Recently, steady-state visual evoked potential(SSVEP) has become one of the most popular electroencephalography paradigms due to its high information transfer rate. Several approaches have been proposed to improve the performance of SSVEP. The calibrationfree scenario is significant in SSVEP-based brain–computer interface systems, where the subject is the first time to use the system.The participating teams proposed several effective calibration-free algorithm frameworks in the SSVEP competition(calibration-free)of the BCI Controlled Robot Contest in World Robot Contest 2021.This paper introduces the approaches used in the algorithms of the top five teams in the final. The results of the five subjects in the final proved the effectiveness of the approaches. This paper discusses the effectiveness of each approach in improving the system performance in the calibration-free scenario and gives suggestions on how to use these approaches in a real-world system.