Research On Interface Optimization Design Of BCI System Based On SSVEP

With the development of brain-computer interface technology,the application of brain-computer interface interaction technology based on steady-state visual evoked potential is gradually diversified,and the potential user group is gradually expanded from the people with movement disorders to the general population.For the SSVEP-BCI system with a digital interface,the ergonomic research on its stimulation interface can improve the system interaction efficiency and user experience.As for the design of SSVEP screen display stimulation interface,previous studies have rich research conclusions on the attributes of stimulation paradigm,stimulation frequency,and stimulation color,while in the field of frequency modulation SSVEP-BCI,there are few studies on the size,spacing,and shape of stimulation elements,there are some limitations in the experimental process and conclusion.This paper adopts the more efficient layout of "cross-type" stimulation elements confirmed by previous studies,and carries out ergonomic experiments and subjective evaluation according to the different levels of the size,spacing,and shape of stimulation elements,to explore the impact of these three factors on the system interaction efficiency and user experience,to summarize design suggestions and optimize the screen stimulation interface of SSVEP-BCI system.Firstly,through the analysis of the theoretical background of SSVEP and the off-line analysis of EEG signals in the laboratory environment,an online BCI system for experiments had established,and then makes the experimental stimulation interfaces with different "size","spacing" and "shape" levels of stimulation elements through Unity,and refers to the existing conventional system interaction usability evaluation questionnaire and scale,According to the content of ISO standard,a subjective evaluation questionnaire for the interactive form of digital interface SSVEP-BCI system is created.Through ergonomic experiments and subjective evaluation,the following research results are obtained:(1)In the range of stimulus element side length size in Experiment 1(2.44°,3.66°,4.88°),the larger the stimulus element size,the shorter the completion time of the human-computer interaction task of the SSVEP-BCI system and the less the number of failures,while the stimulus element spacing has no effect on the efficiency of SSVEP-BCI system.The size of stimulus elements has a significant impact on user comfort.Within the value range of side length of stimulus elements in Experiment 1,the larger the size of stimulus elements,the lower the comfort of subjects;The distance between stimulus elements has a significant impact on the comfort and acceptability of users.The compact or alienated layout will lead to a decline in user satisfaction.In Experiment 1,the horizontal subjective evaluation result of "distance" between stimulus elements,which is 7.32° vertically from the center of the screen and 14.56° horizontally from the center of the screen,is the best.(2)In the shape setting of stimulation elements in Experiment 2(regular triangle,square,regular hexagon,and circle),the human-computer interaction efficiency of the SSVEP-BCI system under circular and square stimulation elements is significantly higher than that of regular triangle stimulation elements,and the completion time data of circle is the best,and the completion time results of regular hexagon stimulation elements are not significantly different from other shapes.Circular stimulus elements failed less than the other three shape categories.In the stimulus element shape setting of Experiment 2,the circle is the stimulus element shape with the highest user experience,comfort,and acceptability,and the degree of fatigue is the lightest,followed by the regular hexagon;The scores of square comfort and acceptability are the same as those of regular hexagon,but the degree of fatigue is the most serious,and the user experience score is the worst in parallel with the regular triangle;The fatigue caused by triangular stimulus elements is the same as regular hexagon,but its user experience,comfort,and acceptability are the worst.This topic explores the influence of the size,spacing,and shape of SSVEP-BCI system screen display stimulation interface elements on system efficiency and users’ subjective feelings through ergonomic experiments and subjective evaluation of subjects,and puts forward corresponding design suggestions and examples,which makes a certain contribution to the SSVEP-BCI system screen display stimulation interface design,provides theoretical guidance for the design in this field and improves the system interaction efficiency and user experience,It has practical application value.