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Feb. 20, 2004 — Vacuum cleaners that are self-directed, jogging suits that tell you when to run faster, robots that dance, airplanes without pilots.
The new millennium brought with it a focus on “smart” devices — appliances, clothes and toys that can, with the help of various sensors, interact with the environment and determine the appropriate action or reaction. An important aspect of such “intelligence” is the ability of these products to know where they are on the ground or in the air.
Until recently, this capability was achieved via use of accelerometers. But these sensors are somewhat limiting in that they can only communicate linear motion (back and forth, up and down, etc). Being able to sense rotational movement adds an extra layer of precision and smarts for more-complex next-generation systems — and this is where gyroscopes come into play.
Gyros — also called angular rate sensors — sense rotational motion. Combining gyros with accelerometers into a single module results in an inertial measurement unit (IMU), which can provide six degrees of freedom measurement. A notable exception at this point is Kearfott Guidance, whose micromachined vibrating beam multisensor can measure both linear and rotational movement. That means only three multisensors are needed for its IMU, rather than the more typical combination of three gyros and three accelerometers.
Gyros and IMUs can provide information on directional navigation (speed, heading and velocity) as well as stabilization and balance. An application that demonstrates this really well is the Segway Human Transporter. IMUs that have been coupled with Global Positioning System technology are typically called inertial navigation systems, which have been rapidly embraced by the military for use in guidance and navigation systems inside what are commonly known as “smart bombs.”
Gyroscopes have been around for decades. But MEMS gyros are making great strides in displacing entrenched technologies — including ring laser gyroscopes (RLG) and fiber optic gyroscopes (FOG). In fact, 10 of the top 12 IMU suppliers are either currently offering or actively developing MEMS gyro-based IMUs. And of the more than five-dozen IMUs available, or known to be in development, nearly 50 percent use (or will use) both MEMS gyros and MEMS accelerometers.
This is certainly surprising in a very good way, as this indicates that IMU suppliers clearly believe that MEMS gyros are the next-generation technology of choice. As a result, they are positioning themselves to take advantage of burgeoning markets by offering MEMS-based products that are increasingly high-performance, robust and low-cost.
At present, nearly all MEMS gyros are sold to the automotive and military markets, with 99 percent sold as part of an IMU. That will change little over the next five years. An interesting side benefit is that accelerometer suppliers also stand to gain. With the exception of Analog Devices and Honeywell, the 19 companies who are currently offering MEMS gyros are focused only on gyros. They’re looking to others to provide the accelerometers for the IMU piece of the puzzle.
The most successful application to date for MEMS gyros in passenger vehicles is Electronic Stability Programs/Vehicle Dynamic Control (ESP/VDC). Introduced in 1995, such systems have already found their way into nearly 10 percent of all cars today. Use of gyros in rollover detection systems is also an application to watch, although the total market opportunity is not nearly as large as it is for ESP/VDC.
Two key defense-related applications for gyros are munitions and unmanned vehicles, both of which are seeing tremendous growth. MEMS’ role in smart munitions has come about as a result of IMUs that are smaller and less expensive than those based on RLG or FOG technologies. MEMS-based inertial navigation systems provide accurate, jam-resistant guidance for artillery shells, bombs, missiles and torpedoes, allowing for precision attacks in any weather, day or night.
The use of gyros in Unmanned Aerial Vehicles for use in military reconnaissance is fairly well known. But their use in non-defense applications could be where the real opportunity lies. Two potential end-uses include looking for hot spots in fire-prone areas (such as the drought-stricken Western United States), and supplementing the U.S. border patrol.
If the average selling price can indeed drop below $10 as suppliers suggest, MEMS gyros will be able to go after applications where low-cost vibrating piezo gyros have gotten a head start — consumer electronics. One application that has garnered a lot of attention is cell phones, using gyros for scrolling through screens, among other things. Quite frankly, they’re not likely to be found in more than a few high-end models for some time, since a price of $10 is one-fifth the total bill of materials in today’s cell phones!
Even so, In-Stat/MDR forecasts revenues of MEMS gyros to grow from $279 million in 2002, to $396 million in 2007, with unit shipments experiencing a compound annual growth rate of 24.2 percent.