MEMS Gyroscope

A silicon mass vibrating at kilohertz frequencies, listening for the whisper of Earth's rotation in a package smaller than a thumbnail.

A MEMS gyroscope measures angular rate — how fast something is rotating around an axis. Etch a tiny mass into a silicon wafer, suspend it on microscopic springs, and set it vibrating at a known frequency. When the whole chip rotates, Coriolis force deflects that vibrating mass perpendicular to both its motion and the rotation axis. Measure the deflection capacitively (the gap between silicon fingers changes by picometers), convert to voltage, and you have a rotation rate. Stack three of these at right angles, add three accelerometers, and you have a full inertial measurement unit that can track position and attitude without any external signal — no GPS, no radio, no light.

The key structure is usually a tuning-fork: two proof masses driven to oscillate toward and away from each other at a resonant frequency of several kilohertz. When the chip experiences angular rotation (rate Ω), the Coriolis acceleration (2 × velocity × Ω) pushes each mass sideways in opposite directions — differential motion that cancels common-mode vibration noise. Comb-drive electrodes sense the nanometre-scale displacement. A feedback loop (force-rebalance) keeps the masses near their rest position, turning the rebalancing force into the rotation measurement. The entire vibrating structure is vacuum-packaged at the chip level to preserve the high mechanical Q-factor (tens of thousands) needed for low noise. Higher Q means less thermal noise, lower bias instability, and longer integration times before errors accumulate.

In plain terms

Imagine swinging a ball on a string back and forth in a straight line. Now turn around while you swing it. The ball's path curves sideways. A MEMS gyroscope is a tiny version of that ball, etched into silicon, and it measures exactly how much you turned by measuring how much the ball drifted sideways.

Also called: Coriolis vibratory gyroscope, CVG, silicon gyroscope, tuning-fork gyroscope, MEMS IMU gyro.

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A short history

The idea of machining mechanical structures into silicon was pioneered at Berkeley in the early 1980s, but the first silicon MEMS device to demonstrate angular-rate sensing came from Draper Laboratory in 1987 — a double-gimbal MEMS Foucault gyroscope. The tuning-fork architecture, which remains the basis of most MEMS gyroscopes today, was first demonstrated at Draper in 1992 with a noise of roughly 500 °/hr/√Hz. That work, led by engineers including Jonathan Bernstein and Marc Weinberg, directly seeded the Honeywell MEMS inertial sensor product line. By 1996, the first all-silicon IMU was launched aboard the Extended-Range Guided Munitions Demonstration Program. Through the 2000s, consumer electronics adoption drove die sizes below 2 mm² and unit costs below a dollar, and by the 2010s every smartphone and game controller contained a Coriolis vibratory gyroscope descended from the Draper tuning-fork design. Research groups, notably at UC Irvine, subsequently demonstrated navigation-grade performance (0.065 °/hr bias stability) from a four-mass silicon MEMS gyroscope operating at a quality factor above 2 million.

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