, 1989; Howe, 1994; Howe and Cutkosky, 1993; Mar, Randolph, Finch, van Verth, & Taylor, 1996; Massie, 1996; Millman, 1995; Mor, 1998; Nakamura & Inoue, 1998; Rao, Medioni, Liu, & Bekey, 1988; Srinivasan & Basdogan, 1997; Yamamoto, Ishguro, & Uchikawa, 1993).Haptic acquisition and display devicesResearchers have been interested in the potential of force feedback devices such as pen or stylus-based masters, like Sensable's PHANToM (Massie, 1996; Salisbury, Brock, Massie, Swarup, & Zilles, 1995; Salisbury & Massie, 1994), as alternative or supplemental input devices to the mouse, keyboard, or joystick. The PHANToM is a small, desk-grounded robot that permits simulation of single fingertip contact with virtual objects through a thimble or stylus. It tracks the x, y, and z Cartesian coordinates and pitch, roll and yaw of the virtual probe as it moves about a three-dimensional workspace, and its actuators communicate forces back to the user's fingertips as it detects collisions with virtual objects, simulating the sense of touch. The CyberGrasp from Virtual Technologies is an exoskeletal device which fits over a 22 DOF CyberGlove, providing force feedback and vibrotactile contact feedback; it is used in conjunction with a position tracker to measure the position and orientation of the forearm in three-dimensional space. Similar to the CyberGrasp is the Rutgers Master II (Burdea, 1996; Gomez, 1998; Langrana, Burdea, Ladeiji, and Dinsmore, 1997) which has an actuator platform mounted on the palm that gives force feedback to four fingers. Position tracking is done by the Polhmeus Fastrak. Alternative approaches to haptic sensing and discrimination have employed the vibrotactile display, which applies multiple small force vectors to the fingertip. For example, Ikei, Wakamatsu, and Fukuda (1997) used photographs of objects and a contact pin array to transmit tactile sensations of the surface of objects. Each pin in the array vibrates commensurate ...
