We have now sufficient evidence that using electrical biosignals in the field of Alternative and Augmented Communication is feasible. Additionally, they are particularly suitable in the case of people with severe motor impairment, e.g. people with high-level spinal cord injury or with locked-up syndrome. Developing solutions for them implies that we find ways to use sensors that fit the user's needs and limitations, which in turn impacts the specifications of the system translating the user's intentions into commands. After devising solutions for a given user or profile, the system should be evaluated with an appropriate method, allowing a comparison with other solutions. This paper submits a review of the way three bioelectrical signals - electromyographic, electrooculographic and electroencephalographic - have been utilised in alternative communication with patients suffering severe motor restrictions. It also offers a comparative study of the various methods applied to measure the performance of AAC systems.

For some people with motor disabilities and speech disorders, the only way to communicate and to have some control over their environment is through the use of a controlled scanning system operated by a single switch. The main problem with these systems is that the communication process tends to be exceedingly slow, since the system must scan through the available choices one at a time until the desired message is reached. One way of raising the speed of message selection is to optimize the elementary scanning delay in real time so that it allows the user to make selections as quickly as possible without making too many errors. With this objective in mind, this article presents a method for optimizing the scanning delay, which is based on an analysis of the data recorded in "log files" while applying the EDiTH system [Digital Teleaction Environment for People with Disabilities]. This analysis makes it possible to develop a human-machine interaction model specific to the study, and then to establish an adaptive algorithm for the calculation of the scanning delay. The results obtained with imposed scenarios and then in ecological situations provides a confirmation that our algorithms are effective in dynamically adapting a scan speed. The main advantage offered by the procedure proposed is that it works on timing information alone and thus does not require any knowledge of the scanning device itself. This allows it to work with any scanning device.

Abdruct -The VAHM project aims to improve the control of powered wheelchairs by adding possibilities of autonomous mobility. The disabled person will indicate the goal to be rerched,may alter already undertaken trajectory or stop the mobile in casc of emergency. A hybrid software architecture is proposed to achieve this. The possibilities offered by such a system are described from itn esami)le of application.

Abstruct-The VAHM project aims to improve the control of powered wheelchairs by adding possibilities of autonomous mobility. We propose specifications which are based on a detailed study of similar projects described in specialized publications. Three operating modes are defined in order to adapt the system to a great diversity of situations. In the autonomous mode a global trajectory is planned, and the user then intervenes to point the goal and, if need be, stop a motion during its execution. The assisted manual mode allows access to local primitives like a wall following. Finally, in the manual mode, we find the classical control of a powered wheelchair again. The first results of the technical evaluation are discussed in the conclusion.

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