A Theory Of Asynchronous Control With Low Information Capacity Interfaces

Low information capacity interfaces (LICIs) such as binary switches, often become the only means by which people with disabilities can interact with their assistive devices. Although numerous studies have been done to develop novel ways to estimate user intention in cases of extreme disability, little attention has been paid to the process by which the acquired information is translated into specific control tasks (e.g. navigating a menu or positioning a cursor). It has been traditionally assumed that an exact estimate of user intention is needed to produce reliable control commands. When using LICIs, this requires lengthy synchronous control strategies which demand a significant amount of sensory feedback. In order to develop appropriate alternatives, we have redefined the latter as a communication, rather than a control problem. Thus, our objective becomes the efficient transmission of control commands from the user to the device through LICIs. By applying basic principles of information theory, we use the natural uncertainty of asynchronous human-machine interactions with LICIs to obtain increasingly accurate estimates of user intention. Our theory is based on the implementation of a virtual intention pointer (VIP) that maps the user's intention on the device domain. Thus, changes in the VIP's behavior result in corresponding changes to the device being controlled. The VIP's behavior is described by user intention rings (UIRs). UIRs are unidimensional, viscoelastic spaces, mapped on each of the angular dimensions of the VIP's velocity vector. A variety of kernels representing different communication/control strategies may be used to deform the UIRs creating non-parametric estimates of user intention. Although cursor positioning and trajectory following in 2- and 3-D spaces are ideal applications for this theory, it can also be used for virtual navigation in multidimensional domains to control, for instance, prosthetic or robotic arms with multiple (>3) degrees of freedom.