Dual-axis microgyroscope with closed-loop detection

A novel dual-axis microgyroscope fabricated by a surface micromachining pro cess is developed. A 7.0-mu m thick polysilicon layer deposited by LPCVD (L ow Pressure Chemical Vapor Deposition) is used for the vibrating structure. The microgyroscope is based on the angular vibration of the four plates wi th closed-loop rate detection. The comb-driven rotational body tilts to eac h input-axis parallel to the substrate and the tilting motion is sensed wit h capacitance change between the bottom electrode and the structure. The tw o tilting modes enable the sensor to detect two-input axis angular rate sim ultaneously within a single-chip. In particular, the structure utilizes a s imple force-balancing torsional torque which does not need another top elec trode layer to reduce the intrinsic non-linearity of a capacitance-type sen sor. The vibrating structure is strongly damped by air, so the gyroscope is tested in a high vacuum chamber for a high quality factor with hybrid sign al-conditioning integrated circuit. The experiment resulted in a noise equi valent signal of 0.1 degrees/s. (C) 1999 Elsevier Science S.A. All rights r eserved.