Ralf Voss

Silicon angular rate sensor for automotive applications with piezoelectric drive and piezoresistive read-out

In this work a silicon angular rate sensor for automotive applications with a new architecture is presented. It is based on the vibrating tuning fork principle with excitation direction of the tines perpendicular to the wafer surface. This arrangement allows the design of tines with significant inertial masses which lead to substantial signal. The oscillation of the tines is excited by a piezoelectric drive using an AlN thin film layer. The angular rate to be measured causes a torsional oscillation of the stem. The torsional amplitude is proportional to the angular rate and is measured by a piezoresistive read-out structure. We use silicon bulk micromachining based on a new twofold SOI-technique.

Tuning fork silicon angular rate sensor with enhanced performance for automotive applications

This paper reports on a silicon angular rate sensor designed for automotive applications like overroll protection and electronic skidding protection. The sensor is based on a tuning fork principle with the tines being piezoelectrically excitated perpendicular to the wafer surface. Due to the Coriolis effect, an angular rate parallel to the axis of the stem generates a periodic torque, which results in a torsional oscillation of the stem. This torsional oscillation is detected with an implanted piezoresistor located in the middle of the stem. A slot in the center of the stem enhances the shear stress at the read-out piezoresistor position resulting in a higher sensitivity. The latest sensor design with a split electrode allows an electronic compensation of mechanical imbalance in order to reduce the sensor offset and offset drift. Additionally, this electrode configuration can generate a periodic torque to perform a permanent test of the sensor functioning and the sensitivity during operation.

Silicon micromachined vibrating gyroscopes

This work gives an overview of silicon micromachined vibrating gyroscopes. Market perspectives and fields of application are pointed out. The advantage of using silicon micromachining is discussed and estimations of the desired performance, especially for automobiles are given. The general principle of vibrating gyroscopes is explained. Vibrating silicon gyroscopes can be divided into seven classes. for each class the characteristic principle is presented and examples are given. Finally a specific sensor, based on a tuning fork for automotive applications with a sensitivity of 250(mu) V/degrees is described in detail.

Robust and Selftestable Silicon Tuning Fork Gyroscope with Enhanced Resolution

Advanced automobile electronic systems like overroll protection , electronic skidding protection and x-by-wire systems require at least one robust and reliable angular rate sensor. Therefore a silicon micromachined gyroscope based on a tuning fork structure was developed with all resonant frequencies being above 10kHz and the primary and secondary gyroscope oscillation frequency being close to 40kHz. Additionally no other resonant frequencies arc within a bandwidth of 10kHz around the gyroscope modes in order to be insensitive to random vibrations occurring in automotive applications and to withstand high shock impacts .