Transparency improvement for haptic interfaces

Haptic interfaces are robotic systems designed to provide information to a user regarding a remote or virtual environment via the sense of touch; these robotic systems accomplish this feat through force feedback. Designers of haptic interfaces desire to produce an interaction using the haptic interface wherein the virtual or remote environment feels indistinguishable from the actual environment; however, it is difficult to define when a haptic interaction feels the same as the real interaction it is reproducing. This thesis discusses transparency as a measure that quantifies the performance of a haptic device by comparing the desired environment to be displayed to the actual environment displayed. In order to demonstrate the utility of transparency as a performance measure, haptic interactions are defined by the causality relationship between the user and the device. These interaction types are introduced as active and passive user interactions. In the active user interaction, the user is treated as an energy source and the environment is a dynamic system without a source of energy; the passive user interaction is the opposite case wherein the environment is an energy source and the user is a dynamic system without a source of energy. Methods of improving transparency, and hence performance, of a haptic device are compared against the definitions of haptic user interactions. These comparisons show that transparency for purely active user interactions is dependent on the user, and that for passive user interactions, transparency is dependent on the user and the haptic interface. In addition, other performance improvement methods often rely linear assumptions which are not general. This thesis proposes a method for improving transparency while maintaining stability without regard to assumptions of linearity.