Principles of haptic perception in virtual environments

Gabriel Robles-De-La-Torre


During haptic interaction with everyday environments, haptic perception relies on sensory signals arising from mechanical signals such as contact forces, torques, movement of objects and limbs, mass or weight of objects, stiffness of materials, geometry of objects, etc. (Fig. 1a). In contrast, haptic perception in Virtual Environments (VEs) relies on sensory signals arising from computercontrolled mechanical signals produced by haptic interfaces (see Fig. 1b, the online animation [1] under Selected Readings and Websites, and [1, 2]). Haptic interfaces are programmable systems, which can reproduce mechanical signals that are normally experienced when haptically exploring real, everyday environments. Perhaps more importantly, haptic interfaces can create combinations of mechanical signals that do not have counterparts in real environments. This allows creating haptic VEs in which entirely new haptic sensory experiences are possible. As a result, it becomes feasible to investigate haptic perception and related phenomena, such as motor control, in entirely new ways. In this regard, interfaces do for haptic perception research what computer graphics does for human vision research. The importance of haptic technology extends beyond scientific research. This technology opens the door to new applications in a variety of fields.
The main objective of this chapter is to discuss the essentials for effective use of haptic VEs in perception research and applications involving user testing. To illustrate this, the chapter also discusses some recent haptic perception discoveries in which haptic VEs played a key role. This chapter does not review the growing perception literature that uses haptic VEs. A full treatment of this literature would require an entire book of its own. Also, an important part of this literature can be consulted in several other chapters of this book. In this chapter, practitioners from fields such as neuroscience will find information to understand the similarities and differences between real and virtual haptic environments. Such practitioners will also find important information about designing and conducting perception experiments involving haptic VEs. This information would also benefit practitioners from areas such as engineering who are interested in haptic perception assessment in specific applications. The close interplay of basic research and engineering in haptic VEs has important implications for perception research and for haptic interface design. This is illustrated with examples of how haptic technology research contributes to our basic understanding of perception, and also of how perception research contributes to practical applications of haptic technology.