P300 and Motor Imagery Based Brain-Computer Interface for Controlling Wheelchairs 1

This paper proposes a brain-computer interface (BCI) wheelchair that integrates the advantages of event-related potential (ERP) and motor imagery (MI). The ERP, known as P300, is generally used to observe ERP, which is based on visual evocation. For example, users are presented with a screen that flashes possible targets. Users have to focus on the desired target and the result of ERP is recognized as targets and nontargets to control corresponding devices. P300 has the advantages of requiring no initial user training and easy to be observed in a simple and discriminative task Methods 2.1 The Control Scheme. The control scheme of wheelchair is divided into speed control and steering control, as shown in The steering control, which includes left turn and right turn, is activated by investigating the MI-based user's intention. For example, users are required to imagine the movement of kinesthetic of left hand to make a left turn of the wheelchair. When users image the movement of kinesthetic of both hands, the wheelchair is stopped immediately. Like driving, drivers adjust steering frequently to reach the desired positions and to avoid collisions. Because MI has the feature of fast feedback, it is suitable for continuous control commands. In order to achieve high reliability of the recognized result, the stimuli on the screen change according to the current condition of wheelchair. For example, the screen presents "Forward" and "Backward" at the idle state. When the "Forward" condition has been selected, the wheelchair moves with the speed of "Speed 1", and the screen presents "Speed 2" and "Stop" for changing speed and stopping the wheelchair. The bottom of left side of The finite state machine (FSM) is applied to describe the dynamic system with event transitions, as shown in Online Experiments. The online experiments, which involve three subjects, were conducted to validate this system. There are four obstacles arranged in a 7 m  4 m field. Eac