The term “joystick” seems a bit frivolous for the device in front of me, but there it is, an interface that hearkens back to the days of Pac Man and Donkey Kong. Yet this joystick is special—a highly evolved example of a technology that is changing the way humans interact with machines. I’m in the Microdynamic Systems Laboratory at Carnegie Mellon University in Pittsburgh, and the interface I’m looking at is properly called a magnetic levitation haptic device. The apparatus is built into a bowl-shaped indentation in a table; its plastic joystick sits in the midst of brightly colored red and blue magnet arrays. As I reach inside the basin to palm the handle, the device hums and shivers almost imperceptibly.
On a monitor in front of me, a small, spherical cursor hovers above a plain studded with nubby cones. It acts as a sort of fingertip for exploring the 3D landscape. When I push straight down on the joystick, the little orb drops. The grip jiggles my hand as I drag the sphere over the rocky ground. It’s surprisingly fun. I jounce over a cluster of mini-pyramids, glide over a smooth spot and then hit a solid wall—pop! I feel the joystick jerk to a stop in my hand. Every aspect of this virtual world is a playground of texture, and the haptic controller translates tactile data into feedback you can feel. It’s a high-tech exploration of an often-ignored sensory faculty—the sense of touch.
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At Carnegie Mellon University’s Microdynamic Systems Lab, this experimental magnetic levitation haptic device is used to quantify a variety of tactile sensations, including roughness and elasticity.
The world of haptics is expansive by definition. It is the field of science and technology dedicated to tactile sensation, and it has applications for everything from handheld electronic devices to remotely operated robots. Yet outside of the research and engineering community, it is a virtually unknown concept. “People don’t even recognize the word ‘haptics’ yet,” says Ralph Hollis, director of the Microdynamic lab. “You have to spell it for them.” In an age of digital devices that stimulate and amaze the eyes and ears with increasingly high fidelity, haptics has been employed mostly in relatively unsophisticated applications—rumbling video-game controllers and buzzers that alert you to a cellphone call. But as our digital tools have become more complex and capable, our interfaces with these devices are beginning to run into the limitations of sight and sound. “It’s really only now that we’re seeing a migration from keyboards and mechanical switches to touchscreens and touch-sensitive surfaces,” says Mike Levin, a vice president at Immersion, a San Jose, Calif., company that produces haptic interfaces. “We’re losing that tactile feel that we had before, and now we’re trying to bring it back.” Plus, games and online social networks are emerging with richly rendered 3D environments that can be hard to navigate on a two-dimensional screen.
Haptics doesn’t just close the gaps in our current computer interfaces—it can open up new possibilities. Blending haptics with recent advances in the field of robotics allows doctors to train for intricate procedures virtually, with increasingly accurate sensory feedback—and the technology can bring a new dimension to remotely controlled machines, helping negotiate obstacles in distant settings. To make haptic technology work, scientists and engineers must fine-tune a variety of sensors, actuators, magnets and motors to simulate the textures and pressures that help us feel our way around our world.
The magnetic levitation haptic device at CMU’s Microdynamic lab is about as finely tuned as modern haptic devices can get. Because it is a maglev system, it reacts instantly, with none of the latencies inherent to mechanical force-feedback interfaces. Position and force are updated more than 3000 times a second. The device exhibits relatively high stiffness, on the order of 225 pounds of force per inch, so it really lets you know when you’ve hit an obstacle. The only disadvantage is a limited range; the floating joystick can move only 12 in. in any direction and tilt up to 14 degrees. The range of motion is similar in scale to writing with a pencil.
According to Hollis, the device is strictly for the lab, but the research has importance beyond pure computer science. “Haptics has brought together people from three different disciplines,” he says. “Engineers who design devices, mathematicians who design efficient algorithms and psychologists who are interested in how the sense of touch really works.”
Compared to vision or hearing, the science behind the sense of touch is poorly understood. With help from haptic devices, however, a field of study called psychophysics is quantifying the subjective experience of various sensations. One of Hollis’s colleagues at CMU is Roberta Klatzky, a psychologist who uses the magnetic levitation haptic device to test how people perceive feelings such as roughness. Klatzky is positively starry-eyed about the potential of haptic feedback. “You could feel the fabric of a piece of clothing before buying it on the Internet,” she says of an e-commerce application. “We can create haptic experiences that you would never be able to have, living in the physical world.” Researchers at the University of North Carolina have already developed a nanomanipulation device that provides haptic feedback for microscopic-level materials that could not otherwise be felt by human hands.