Haptics

Visualize   By Tracy Staedter   April 2002

A glove and mechanical assembly let you feel the unreal.

Most virtual-reality systems immerse you in a world of virtual sight, sound and motion. But even these sensory-laden experiences can seem like glorified spectating. If you really want to participate, you need the sense of touch.

Few computer-simulated environments offer haptic (from the Greek haptikos, meaning “to touch”) interfaces that do more than buzz or vibrate. Building the devices and writing the programs to control them have been costly endeavors. Touch-technology developer Immersion in San Jose, CA, is among a handful of companies offering commercial products, such as CyberGrasp, that let users press, push, pull, punch, squeeze, swat and sculpt virtual objects in a computer-generated world.

CyberGrasp consists of a lightweight mechanical assembly, or exoskeleton, that fits over a motion capture glove. About 20 flexible semiconductor sensors sewn into the fabric of the glove measure hand, wrist and finger movement. The sensors send their readings to a computer that displays a virtual hand mimicking the real hand’s flexes, tilts, dips, waves and swivels.

The same program that moves the virtual hand on the screen also directs machinery that exerts palpable forces on the real hand, creating the illusion of touching and grasping. A special computer called a force control unit calculates how much the exoskeleton assembly should resist movement of the real hand in order to simulate the on-screen action. Each of five actuator motors turns a spool that rolls or unrolls a cable. The cable conveys the resulting pushes or pulls to a finger via the exoskeleton. If the virtual hand is grasping a virtual wrench, for example, the actuators provide resistance to the human fingers at the points where they would touch the tool’s edges.

The CyberGrasp is not alone in the feel-good market. Woburn, MA-based SensAble Technologies, founded by MIT haptics pioneer Thomas H. Massie, makes several touch-based modeling systems for industrial designers. SensAble’s FreeForm system consists of a stylus attached to a jointed arm. Actuators exert pressure on the stylus as the user sculpts objects from virtual clay.

Though available now, these technologies cost tens of thousands of dollars. It could be years before you find yourself feeling your way through the virtual world.


Tracy Staedter is the managing editor at Technology Review.