2 Copyright 1990 McGraw-Hill, Inc. Byte July, 1990 SECTION: FEATURES; Vol. 15, No. 7; Pg. 283 LENGTH: 2416 words HEADLINE: REACH OUT AND TOUCH YOUR DATA BYLINE: Howard Eglowstein ; Howard Eglowstein is a BYTE Lab testing editor. He can be reached on BIX as ''heglowstein.'' HIGHLIGHT: Three commercial hand trackers sense your every move BODY: Make a fist and shake it at your computer screen. Nothing happens? That's because you're not wearing a hand-tracking device. Although keyboards and mice convert hand movements into data, they can't capture the sweeping gestures and subtle articulation of a hand moving in space. Three commercial products purport to do just that: VPL Research's DataGlove, Exos's Dexterous Hand Master, and Mattel's Power Glove. When you wear one of these devices, it measures how much your fingers are flexed. A controlling computer, sampling the instrument's sensors at a rapid clip, can figure out the shape of your hand. Add a way to locate the hand in space, and you've got hand tracking. Imagine literally grabbing a dBASE record or rotating an AutoCAD model with a twist of your wrist. There is a world of possibilities; see ''Telltale Gestures'' on page 237 for more applications now in development. It's Not Polite to Point Each product discussed here uses its own method to track the fingers. Two of them use magnetic field interference to track hand motion, and one uses ultrasound triangulation. VPL's DataGlove, perhaps the best-known hand-tracking device, relies on fiber optics. When you bend a fiber-optic cable, the light dims in proportion to the amount of flex. The DataGlove uses loops of fiber-optic strands that run up the back of your hand. A part of each loop, which is fixed over the knuckle and first joint of each finger, forms a sensor (see figure 1). One end of the fiber loop connects to a constant light source, the other to a sensitive photo detector. A microprocessor scans through each of the 10 detectors in turn and takes a light reading. As the light intensity diminishes, the processor records more bend. After the whole hand has been read, the real fun begins. Calculating the angle of each joint requires knowing a lot about the physical nature of the hand and the makeup of the optical sensors. The microprocessor in the DataGlove controller takes care of managing that model and performing the needed computations. Precise measurements require that the fibers line up properly over the joint. The DataGlove relies on a snug-fitting Lycra glove that fits, well, like a PAGE 2 1990 McGraw-Hill, Inc., Byte, July, 1990 glove. The fibers, sewn onto the back of each finger, collect at the base of the glove on the back of the hand, as shown in photo 1. A separate unit, the size of a pocket calculator, houses the light source and sensors. A computer interface manages the scanning of the sensors and the communications with the host computer. The DataGlove uses a standard RS-232C serial port, which makes it compatible with most computers. Somewhere, My Glove Now the computer can tell what the fingers are doing. The next thing it needs to know is the position of the hand relative to a fixed point. VPL has incorporated the Polhemus Navigation Sciences' 3Space Tracker into the DataGlove. The Tracker measures magnetic interference in three dimensions. Users of Exos's Dexterous Hand Master typically employ the Tracker, too. Any coil charged with an electrical current generates an electromagnetic field. The field is strong in the direction of the coil's radius, and it is relatively weak in the perpendicular direction. Similarly, a magnetic field passing through a coil of wire generates an electric current proportional to the field's strength. The Tracker uses a transmitter with three coils of wire, each perpendicular to the other two. A similar receiver has the same arrangement (see figure 2). The Tracker's controller pulses each of the transmitter's coils in turn and reads the current generated in each of the three receiving coils, for a total of nine readings. Determining the receiver's orientation and distance from the transmitter requires plenty of math -- more than you'll need to do your taxes. Knowing that the strongest readings come from coils that lie on the same plane as the transmitter, the microprocessor can determine the orientation of the receiver in space (relative to the transmitter), as well as the distance in x, y, and z directions. The system works amazingly well. It can determine the relative positioning to the nearest tenth of an inch and to within half a degree, anywhere within a 3-foot radius. The receiver is a small, lightweight plastic cube, about the size of a sugar cube, that mounts on the back of your wrist. The transmitter, a slightly larger cube, rests near the DataGlove wearer on a stationary stand. Both the receiver and the transmitter connect to a control unit that handles the pulsing and sensing; the control unit connects to the host computer by way of a standard serial or parallel interface. Double-Jointed The DataGlove emphasizes comfort with a good degree of precision. However, unless you are an alien from the planet Zambodia, your fingers have three joints, not two. Exos's Dexterous Hand Master (see photo 2) delivers precise measurements at the expense of form. The Hand Master uses an intricate exoskeleton that fits over the back of your hand. Velcro bands and finger pads attach this framework to the midpoint of each finger segment, and a hinged joint connects each of the finger pads. Figure 3 shows the arrangement of the joints. Make no mistake -- this thing looks bizarre; it's not really a glove at all. But it's considerably more comfortable than it looks. The skeleton is made of lightweight aluminum. Each of the joints contains a small magnet and a Hall-effect sensor to measure the bending angle. The PAGE 3 1990 McGraw-Hill, Inc., Byte, July, 1990 sensor, built into the hinge assembly, responds with a voltage that is proportional to the strength of a nearby magnetic field. A small magnet bound to the sensor moves closer to or farther from it as the joint bends. The Hand Master connects to any standard AT-bus (Industry Standard Architecture) PC compatible through a custom data-acquisition board. The PC software reads the voltage from each of the sensors in turn to measure the position of the fingers. Thumb Fun Oops -- I almost forgot about the side-to-side motion. Happily, Exos didn't. Fingers can do more than go up and down; they go left and right, too, especially the thumb. Extra sensors on the Hand Master take care of the left and right motions, while allowing for measuring the full range of thumb motion. Like the DataGlove, the Hand Master can't detect the position of the entire hand. Hand Master applications typically use the same Polhemus Tracker that DataGlove applications use. Clearly, the Hand Master uses a different approach to hand sensing than the DataGlove does. However, both cost as much as a new car. The DataGlove in its standard configuration will set you back about $ 8800. If you prefer the added precision of the Hand Master, plan on handing over $ 15,000. But if you need that level of precision and reliability, both are cheap at the price. The same can be said of computers. Not everyone needs megabytes of memory and a hard disk drive, as the home video game manufacturers have known for years. Case in point: that Nintendo Entertainment System you bought for your kids. Did you know it has the same processor that the Apple II uses? Did you know that Mattel makes a hand-sensing glove for the Nintendo? One that you can buy for about $ 100? Mattel's Power Glove is a completely different animal than the DataGlove, yet the two share a common heritage. The Power Glove's basic design derives from the DataGlove's, with a few obvious modifications for the home video market. Most notably, it's a lot more rugged (see photo 3). Glove at First Sight The optical fibers on the DataGlove are fully exposed, glued to a lightweight Lycra glove. Not only is that construction expensive, but video-gaming kids would destroy the thing in 10 seconds flat. Mattel replaced the delicate fibers with a flat plastic strain gauge. The strain gauge has a convoluted history. In the early 1980s, engineers developing the Koala touchpad needed a tough, flexible plastic with a constant resistive surface. During development, there were a number of rejects -- one of which changed resistance as it was bent. That material, which is now manufactured by Amtec, forms the basis of the sensor technology that the Power Glove uses in its fingers. The sensors are 3 1/2-inch strips of polyester, coated with 0.6 mils of a specially formulated ink. As the sensor bends over the normal range of finger movement, the resistance changes. One sensor in each finger measures all the joints at once. This precludes measuring the individual joints, but does Mario really care if you bent your first or second joint? For Nintendo games and many PC applications, it's reasonable to measure the whole finger with some degree of precision and make assumptions about the individual joints. PAGE 4 1990 McGraw-Hill, Inc., Byte, July, 1990 So, you've got five sensors, one for each finger. That means you also need an A/D converter to read the sensors, and some kind of processing power. The Power Glove uses an 8-bit processor to watch the fingers, communicate with the host computer, and handle the ultrasonics. Ultrasonics? What for? You Don't Know Where That Hand Has Been Polhemus's Tracker technology would be far too expensive to include in a $ 100 retail product, so Mattel had to come up with something else. The solution that Mattel chose was an ultrasonic ranging system similar to that on modern Polaroid cameras. A small transducer located on the back of the Power Glove sends out a short click. Three receivers, one each to the left top, right top, and right bottom of your monitor, receive the click. They all hear the same sound, so the time it takes them to register the click will determine the absolute distance to the glove as well as the relative distance. A second transducer, which is located a few inches from the first, does the same. From there, the processor, which knows the speed of sound and the spacing between the transmitters and receivers, can use triangulation to compute the distance of the glove from the sensor array as well as the glove's roll and pitch (see figure 4). Ultrasonics, however, suffer from one inherent disadvantage: They require an unobstructed line of sight. If the transmitters don't point directly at the receivers, the Power Glove simply can't track. Other than that, though, it's a very sound design. OK, I'm Game As long is you're facing the receiver array, and you are within the normal range of the ultrasonics (about 5 feet), the Power Glove can track your hand motion to within a quarter of an inch and measure the flex of your fingers to some fair degree of accuracy. For the personal computer user, the most significant drawback of the Power Glove is that it will work only with the Nintendo system. To that end, the unit comes with a proprietary Nintendo connector that plugs directly into the game unit. Even worse, the Power Glove takes all its detailed information and converts it into an emulation of the standard game controller pads. Although there is a special high-resolution mode, the standard mode will give you the A fire button (flexing the thumb), the B fire button (flexing the index finger), Start, Select, and the up/down/left/right motion from center. Notice that it can't tell you how far from the center you are, just that you're off-center. The Power Glove's low price makes it a fascinating device for folks who are interested in experimenting with hand trackers. I created crude but usable gesture-recognition software using only the cursor pad emulation. The text box ''Can We Talk?'' on page 288 describes the communications protocol and the cabling that are required to connect the glove to an unused printer port on your PC compatible. Give Your Computer a Hand? After getting my hands on these three products, it's evident that none in its present form could ever replace the mouse. The Dexterous Hand Master measures the anatomical motions of the hand with more PAGE 5 1990 McGraw-Hill, Inc., Byte, July, 1990 precision than today's applications could exploit. The DataGlove would be more practical for mainstream applications, but the fibers mounted on it seem too delicate to withstand the rigors of everyday use. And the price tags of these two products clearly put them out of reach as a replacement for your computer's mouse. What about the Power Glove? Maybe. Mattel implemented it beautifully for the home video market. It's priced right and has more-than-adequate resolution for its intended purpose. The appearance is less than professional, but then, it wasn't designed to be used in the boardroom. The Power Glove is one rugged puppy, built for hard use by kids playing Nintendo games. Being so new, no one really knows how long the Power Glove will hold up under actual use. The unit I worked with was connected to a PC compatible for several weeks. It looked haggard after being crunched under piles of books and papers, but it never failed to work. Still, the Power Glove will probably never become a popular accessory for Macs or PCs. We need something else. All three vendors agree that some yet-undeveloped product would fill that need nicely. A product with the Hand Master's precision, the DataGlove's ease of use, and the Power Glove's affordability and rugged construction would be just the ticket. In the meantime, don't sell these products short. Many applications -- most obviously, CAD -- are just crying out for a good three-dimensional input device. The Dexterous Hand Master and the DataGlove are here today, and they are priced within the budgets of those who really need them. If you're just curious, you might want to try experimenting with a Power Glove. I've navigated Lotus 1-2-3 spreadsheets, logged onto BIX, and scrolled through hours of Prodigy screens without ever touching my keyboard. The Power Glove is just downright fun, and it's a good way to get your hand on (or in) a piece of the future. COMPANIES MENTIONED Amtec International (Strain gauges inside the Power Glove) 3653 West 1987 South Salt Lake City, UT 84104 (801) 977-0359 Curtis Manufacturing, Inc. (NC-1 Super Extendo) 30 Fitzgerald Dr. Jaffrey, NH 03452 (603) 532-4123 Exos, Inc. (Dexterous Hand Master) 8 Blanchard Rd. Burlington, MA 01803 (617) 229-2075 Mattel, Inc. (Power Glove) Consumer Affairs 5150 Rosecrans Ave. Hawthorne, CA 90250 (213) 978-5150 Polhemus Navigation Sciences ( 3Space Tracker) P.O. Box 560 Colchester, VT 05446 (802) 655-3159 PAGE 6 1990 McGraw-Hill, Inc., Byte, July, 1990 VPL Research, Inc. (DataGlove) 656 Bair Island Rd., Suite 304 Redwood City, CA 94063 (415) 361-1710 GRAPHIC: Figure 1, The DataGlove's sensors are glued to the glove, arranged directly over each joint. Loose fibers connect each sensor to a light source/receiver pair for measurement. ; Figure 2, Designed to report the relative location of the user's hand in space, the Polhemus 3Space Tracker consists of a small cube mounted on the hand, and a slightly larger transmitter that rests on a stationary stand nearby. The cutaway views show the three perpendicular coils in both the transmitter and the receiver. ; Figure 3, The Hand Master consists of an exoskeletal arrangement of sensors. The sensors are held over each finger joint by lightweight pads and Velcro straps. Each sensor houses both a Hall-effect magnetic pickup and a magnet. ; Figure 4, The Power Glove uses two ultrasonic transmitters and three receivers to triangulate the position and orientation of the hand. The cursor keypad duplicates the sensory functions and allows for somewhat more precise input. ; Photograph, Perhaps the best-known hand-tracking device, the VPL DataGlove relies on fiber optics to track finger motions. ; Photograph, The Dexterous Hand Master from Exos uses an intricate exoskeleton, made of lightweight aluminum, that fits over the back of the hand.; Photograph, Mattel's Power Glove shares a common heritage with VPL's DataGlove, but it was designed for the home video market. As such, it's a lot less expensive and a lot more rugged. Nevertheless, you can easily adapt it to work with a PC-compatible computer.