Mechanical Balancing
Micro-electromechanical systems design employs multiple decoupled proof masses to cancel out common-mode vibration and external shocks. Implementing a quad-mass architecture utilizing four symmetrically arranged proof masses provides high immunity to cross-axis interference in gyroscopes and resonant sensors. This design relies on the differential motion of the masses to distinguish between rotational rates and linear accelerations.
Acceleration Compensation
The four masses are interconnected by a system of micro-machined springs that constrain their movement to specific modes. In a gyroscope using a quad-mass architecture, the drive loop excites the masses into anti-phase oscillation. When the sensor undergoes linear acceleration, the masses move in the same direction, which cancels out in the differential sense electronics.
This configuration ensures that only the Coriolis force causes the specific out-of-phase displacement that is measured as rotation.
Production Tolerances
High-precision etching processes define the dimensions of the silicon suspension beams and proof masses. Standard electrostatic tuning adjusts the resonant frequencies of the individual masses to compensate for minor manufacturing variations in the quad-mass architecture. This balancing process is performed before the sensor is hermetically sealed at the wafer level.
Resonant Isolation
The balanced nature of the four-mass system reduces the transmission of mechanical energy from the sensor to the surrounding substrate. This isolation prevents energy loss through the package and maintains a high quality factor. A higher quality factor increases the resolution and stability of the sensor output.
