Fall 2012 IAB & Research Review
September 19 to 21
Circular Orbit Operating Mode for MEMS Gyroscopes
We present a gyroscope operating mode that reduces bias errors and scale factor drift and allows whole angle read-out. The gyroscope proof mass orbits in a circle at its natural frequency. An outside observer rotating under the proof mass then perceives a frequency change. If the observer rotates in the same direction as the orbital spin, the perceived frequency decreases, and in the opposite direction, the frequency increases. The addition of a second gyroscope that spins in the opposite direction enables a differential measurement, reducing temperature sensitivity. The frequency difference is exactly the angular rate; thus, the phase difference is the whole angle. Rate bias errors due to mechanical quadrature and cross-axis damping are periodic on the current angle of the proof mass relative to the sensor frame and are hence averaged out over one cycle. A 3-theta dual ring gyroscope chip with integrated CMOS buffer electronics and an off-chip controller demonstrates the technique.