Alternative communication systems for people with severe motor disabilities: a survey <s> Switch based control and Proportional Biosignals sensors <s> In line with the mission of the Assistive Technology Act of 1998 (ATA), this study proposes an integrated assistive real-time system which "affirms that technology is a valuable tool that can be used to improve the lives of people with disabilities." An assistive technology device is defined by the ATA as "any item, piece of equipment, or product system, whether acquired commercially, modified, or customized, that is used to increase, maintain, or improve the functional capabilities of individuals with disabilities." The purpose of this study is to design and develop an alternate input device that can be used even by individuals with severe motor disabilities. This real-time system design utilizes electromyographic (EMG) biosignals from cranial muscles and electroencephalographic (EEG) biosignals from the cerebrum's occipital lobe, which are transformed into controls for two-dimensional (2-D) cursor movement, the left-click (Enter) command, and an ON/OFF switch for the cursor-control functions. This HCI system classifies biosignals into "mouse" functions by applying amplitude thresholds and performing power spectral density (PSD) estimations on discrete windows of data. Spectral power summations are aggregated over several frequency bands between 8 and 500 Hz and then compared to produce the correct classification. The result is an affordable DSP-based system that, when combined with an on-screen keyboard, enables the user to fully operate a computer without using any extremities. <s> BIB001 </s> Alternative communication systems for people with severe motor disabilities: a survey <s> Switch based control and Proportional Biosignals sensors <s> An oral tactile interface provides an approach for silent and hands-free communication between humans or between human and machine. An efficient tongue-operated switch array (TOSA), which provides an alternate input or manipulating method for a computer or operative system, is described. A TOSA has been designed and fabricated using printed circuit board technology and a membrane-switching mechanism, and is integrated with a dental palate mold made from a silicone impression material. The TOSA has four switches laid out in cardinal directions with a fifth switch in the center. Human subject experiments have been conducted to evaluate device performance. The characteristics of tactile sensation and mobility of the tongue are used to quantify the performance and optimize the geometric design of the TOSA. Results indicate that operation on all switches are highly accurate and fast enough for use as an alternative input method. <s> BIB002 </s> Alternative communication systems for people with severe motor disabilities: a survey <s> Switch based control and Proportional Biosignals sensors <s> 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. <s> BIB003
A human-machine interface sensor can be defined as a device meant to capture and transmit the action that the user intends to perform. Due to the wide range of ways for the sensors used as communication aids to capture and transmit information, it appears necessary to sort them according to the operational mode. Two function types can then be identified: the switch-based control (SBC) sensor type and the proportional sensor type (PRO). This classification is no obstacle to the possibility of combining these functions and thus raises the number of possibilities of interaction when using the communication aid. For instance, sensors designed to act as a mouse replacement call on these two function types with the click button (SBC) and the movement controlling a cursor (PRO) on the screen. A SBC type sensor just transmits binary signals to the AT device, whatever technology has been applied for its conception. Consequently, this device is the least efficient when used for interaction with a communication aid. Such systems work only as a tool to scan various possibilities and make a selection, the major difficulty being then to decide about the scanning delay BIB003 . The PRO-type sensor has the clear advantage of representing several binary commands using only one proportional signal in the same way one integer number is represented by one or more bits, thus saving the user time and effort during the AT device operation. However, these sensors -that are generally used to control a cursor on the computer screen -suffer a drawback related to their mode of operation: the person with disability is supposed to have sufficient dexterity to control them, which is not always the case. To take advantage of an electrical biosignal in AAC tasks, the user may express his intention in three different ways: eye movements (EOG), muscle (EMG) and cerebral activity (EEG). Even though these sensors may also be used to provide a progressive signal as in  , they usually deliver a binary one, which demands lesser control over the body functions by the user. One example of using the biosignal with either PRO or SBC type sensor is the interpretation of the EMG signal. The envelope amplitude may be translated to: (i) a binary signal, when compared against a threshold (muscle contracted or not) or (ii) a continuous signal scaled between 0 and a maximum value. It must be observed that the use of the progressive signal in this specific case is highly dependent of the final application, which may be more or less susceptive to envelope amplitude variations. Another case is using the EOG signal to deploy a PRO-sensor, as each degree of eye movement represents changes from 14 to 16 μV in the recorded signal. Other strategies generate discrete signals employing binary information obtained from a biosignal. Barreto et al. BIB001 controlled a cursor that was allowed three different levels of speed, which increased over time as long as the muscle remained contracted. The biosignal sensor is generally more complex than those using mechanical principles, requiring elaborated circuitry for data acquisition and signal processing algorithms. In spite of the technical feasibility of exploring electrical biosignals, the application of those kinds of sensors for alternative communication is indicated mainly in cases of severe motor disabilities. In situations where the user demonstrates the ability to move some part of the body, other approaches will probably be more suitable than using electrical biosignals: (i) head movements tracked by a camera is an alternative to control a cursor using EMG from facial muscles; (ii) sensor using mechanical principles, such as pressure membrane based devices activated with the tongue BIB002 or the side of the head are easier to operate and less prone to errors than a BCI system.