Fraunhofer Institute for Electronic Nano SystemsOne focus of the R&D activities at Fraunhofer ENAS is the development of high precision MEMS angular rate sensors. Angular rate sensors are inertial sensors that can measure angular velocity without an external reference. The developed vibratory gyroscopes use the Coriolis effect, which occurs due to the oscillation (vibration) forced in the MEMS and an existing angular velocity. A force, called the Coriolis force, is generated and produces a detectable signal proportional to the rotational speed or rate.
The challenge for the development of the micromechanical systems or the entire sensor system is to achieve the target requirements for extremely low noise and low drift. The system consists of a micromechanical structure a mixed-signal ASIC co-designed with the MEMS and a package. The micromechanical structure transforms the applied angular velocity into a capacitance change. The ASIC performs the tasks of primary excitation of the MEMS, capacitance-to-voltage conversion, demodulation of the angular velocity information, and signal conditioning. At the same time, it serves as an interface for the next higher system level. The typical parameters of the developed rotation rate sensor are:
- ± 450 °/s Rotation rate range
- 5 °/h resolution = 14 mdps (milli degrees per second)
- In-run bias stability < 1 °/h
- Angle random walk (noise) < 0.03 °/√h (0.00043 °/s/√Hz)
- Operating temperature range from -40 °C to 85 °C