Decoupled Drive MEMS Angular Rate Sensor
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Solution Overview
Problem
Existing angular velocity sensors using vibratory rate gyroscopes face challenges in accurately measuring angular velocity due to non-idealities in electrostatic actuators, which can cause unwanted motion and rotation of the proof mass, leading to measurement errors.
Innovation Solution
The angular rate sensor design includes a substrate with a rotating structure and a drive mass anchored to it, using electrostatic actuators to drive the drive mass into oscillation along one axis and the rotating structure into rotational oscillation around a second axis, with transducers to sense motion responsive to Coriolis forces, while decoupling the drive mass from the rotating proof mass to minimize non-ideal forces and errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electrostatic actuators are used to drive the proof mass, then the sensor can achieve angular velocity measurement functionality, but non-idealities in the actuators cause unwanted motion and rotation of the proof mass leading to measurement errors
Solution Approach 1:
The system is divided into separate drive and sense components. The drive mass is separated from the sense mass (proof mass), allowing independent optimization of each function. The drive system generates motion while the sense system measures Coriolis effects, preventing actuator non-idealities from directly affecting measurement accuracy.
Solution Approach 2:
The drive function is extracted from the proof mass system. A dedicated drive mass is used to generate the primary oscillation, while the proof mass is reserved solely for sensing. This extraction removes the source of actuator-induced errors from the measurement path.
2Device complexity
If a coupled drive and sense system is used, then the device structure is simplified, but non-ideal electrostatic forces directly affect the proof mass causing measurement errors
Solution Approach 1:
The system divides functionality into separate physical components: a drive mass for generating motion and a proof mass for sensing. This segmentation increases structural complexity but eliminates the coupling that causes measurement errors, achieving a trade-off where moderate complexity increase yields significant precision improvement.
Solution Approach 2:
The drive mass acts as an intermediary between the electrostatic actuator and the proof mass. It receives actuation forces and transmits only the beneficial driving motion to the proof mass through controlled coupling, filtering out non-ideal forces in the process.
3Measurement precision
If the drive mass is decoupled from the rotating proof mass, then measurement accuracy is improved by minimizing non-ideal forces, but the device complexity increases
Solution Approach 1:
The system segments the proof mass into two distinct functional components: a drive mass for actuation and a proof mass for sensing. This segmentation requires additional structural elements and coupling mechanisms, increasing device complexity while enabling independent optimization of drive and sense functions for improved measurement precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances the sensitivity and accuracy of angular velocity measurements by minimizing the impact of non-ideal electrostatic actuator forces on the proof mass, reducing measurement errors and optimizing area usage with a decoupled drive system.
Implementation Method 1
an actuator for driving the drive mass into oscillation along a first axis in plane to the substrate
Implementation Method 2
for driving the rotating structure into rotational oscillation around a second axis normal to the substrate
Implementation Method 3
a first transducer to sense the motion of the rotating structure in response to a Coriolis force in a sense mode
Data Source
AI summary
In a first aspect, the angular rate sensor comprises a substrate and a rotating structure anchored to the substrate. The angular rate sensor also includes a drive mass anchored to the substrate and an element coupling the drive mass and the rotating structure. The angular rate sensor further includes an actuator for driving the drive mass into oscillation along a first axis in plane to the substrate and for driving the rotating structure into rotational oscillation around a second axis normal to the substrate; a first transducer to sense the motion of the rotating structure in response to a Coriolis force in a sense mode; and a second transducer to sense the motion of the sensor during a drive mode. In a second aspect the angular rate sensor comprises a substrate and two shear masses which are parallel to the substrate and anchored to the substrate via flexible elements.