Two-Input Axis Angular Rate Sensor

Abstract

A vibrating angular rate sensor is developed by the polysilicon surface micromachining process. The 7.0 µm-thick polysilicon layer is deposited by low-pressure chemical vapor deposition (LPCVD) and is suspended by sacrificial oxide wet etching after patterning by reactive ion etching. The angular rate sensor uses angular resonance for the driving and sensing modes. The two-degenerate sensing modes enable the sensor to detect the angular rate inputs from each orthogonal substrate rotation. In view of cost and size, one sensor chip is preferable to two sensor chips orthogonally-configured for the detection of two-input axis angular rate. The Coriolis motion arising from the angular rate causes the capacitance change and is converted to voltage change with signal conditioning hybrid application-specific integrated circuit (ASIC). The performance of the angular rate sensor is degraded by air damping, so the sensor element is housed in a high vacuum chamber for a high quality (Q) factor. The angular rate sensor has an active structure element less than 1mm2 in size and shows a noise equivalent signal of 0.1 deg/s.