中文摘要：

针对目前基于低频稳态视觉诱发电位的脑-机接口（Steady state visual evoked potential-brain-computer interface,SSVEP-BCI）系统存在目标数目少、刺激时间长、易诱发疲劳和癫痫等不足导致的系统稳定性不高、信息传输率低问题,提出高频组合编码稳态视觉诱发电位（Combination coding-based high-frequency SSVEP,CCH-SSVEP）范式,通过n个稳态高频排列组合实现刺激编码,理论上可呈现nn个刺激目标,解决单频率呈现目标数量受限的问题;同时,针对组合刺激编码产生的变频脑电信号时序特征,提出基于改进的希尔伯特-黄变换（Improved Hilbert-huang transform,IHHT）的变频脑电信号特征提取与局部频谱极值目标识别方法,针对经验模态分解（Empirical mode decomposition,EMD）在变频脑电信号处理应用中的端点和停止准则优用问题,分别对比优选端点切线预测法和固定筛选10次停止准则,提出广义过零点（Generalized zero-crossing,GZC）算法计算瞬时频率,并在应用中通过差异化组合优化选择频率刺激编码,最终提高了目标信号的辨识效率,从而提升CCH-SSVEP的通讯传输速率和可靠性;再利用高频SSVEP（高于25 Hz）的刺激闪烁融合效应,提高使用者的舒适度,降低诱发疲劳和癫痫的可能。将该方法应用于智能轮椅脑-机导航控制中,通过3个基本频率的对比试验（低频传统SSVEP范式呈现3个目标和高频CCH-SSVEP范式呈现6个目标）验证该方法的技术优势,保障了基于高频组合编码稳态视觉诱发电位的智能轮椅导航高效无损功能实现。

英文摘要：

A new steady-state visual evoked potential（SSVEP） paradigm for brain computer interface system（BCIs） is proposed in order to solve the problems of lower stability and information transfer rate（ITR）, duing to the shortages of target number less, easy to make subjects fatigue and increase the risk of photosensitive epileptic seizures in the traditional low frequency SSVEP-BCIs. The new paradigm is time series combination coding-based high-frequency SSVEP（CCH-SSVEP）. The CCH-SSVEP paradigm produces nn with n high stimulation frequencies through time series combination code in order to solve the problem of few targets in traditional SSVEP-BCIs utilizing single frequency to encode each target. Furthermore, an improved Hilbert-huang transform（IHHT）-based variable frequency EEG feature extraction method and a local spectrum extreme target identification algorithm are adopted to extract time-frequency feature of the proposed CCH-SSVEP response. Linear predictions and fixed sifting（iterating） 10 times are used to overcome the shortages of end effect and stopping criterion of empirical mode decomposition（EMD） in the processing of variable frequency EEG data, generalized zero-erossing（GZC） is used to compute the instantaneous frequency of the proposed SSVEP respondent signals, the differentiation combination method is proposed to select the combination coding sequence in order to increase the recognition rate, in the result, the ITR and the stability of the CCH-SSVEP-BCI system are Improved. What is more, SSVEPs evoked by high-frequency stimuli（beyond 25 Hz） minimally diminish subject＇s fatigue and prevent safety hazards linked to photo-induced epileptic seizures, utilizing the flicker fusion effect. Six stimulus targets are presented with three high frequencies through CCH-SSVEP, as a contrast, three stimulus targets are presented with three low frequencies through traditional SSVEP, the above two kinds of different contrast experiments are applied to intelligent wheelchair navigation