A Low-cost Rate-grade Nickel Microgyroscope

This paper presents a low-cost microgyroscope with a resolution in the rate-grade at atmospheric pressure, which is fabricated using a CMOS compatible nickel electroplating process. Angular rate resolution of the gyroscope is increased by matching the resonance frequencies of the drive and sense modes close to each other using symmetric suspensions and electrostatic frequency tuning; whereas, undesired mechanical coupling between the two modes during matched mode operation is reduced by the fully decoupled gyro flexures. Reduced mechanical coupling results in a stable zero-rate output bias, i.e., providing excellent bias stability. The gyroscope is hybrid connected to a CMOS capacitive interface circuit, and the hybrid system operation is controlled by external electronics constructing an angular rate sensor. The sensor demonstrates a noise equivalent rate of 0.1(deg/sec)/Hz and short-term bias stability better than 0.1deg/sec. The nominal scale factor of the sensor is about 18mV/(deg/sec) in a measurement range of ±100deg/sec, with a nonlinearity of only 0.12% full-scale. Measurement bandwidth of the gyroscope is currently set to 30Hz, while it can be extended beyond 100Hz depending on the application requirements.