3-Axis Angular Accelerometer Layout for Low-Offset Sensing
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Solution Overview
Problem
Existing MEMS angular accelerometers face challenges in accurately detecting angular acceleration around three orthogonal axes due to undesirable offset errors and reduced sensitivity caused by mechanical stress, particularly when the proof mass is suspended by a central anchor.
Innovation Solution
The accelerometer design positions sensing elements differently for each axis, with those for the z-axis closer to the center and x and y-axes farther away, using tethering structures to reduce mechanical stress impact and enhance sensitivity, and employs differential signaling to suppress common mode signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the proof mass is suspended by a central anchor, then the device structure is simplified, but mechanical stress causes offset errors and reduced sensitivity
Solution Approach 1:
The device divides the sensing function into multiple independent sensing elements positioned at different locations (inner edge, outer edge, and intermediate positions) rather than relying on a single central anchor point. This segmentation allows each element to detect angular acceleration independently, reducing the impact of mechanical stress on overall measurement precision.
Solution Approach 2:
Different sensing elements are positioned at different radial distances from the center to optimize their local sensing characteristics. Elements at the inner edge are closer to the rotation axis where mechanical stress is lower, while elements at the outer edge experience higher stress but provide different sensitivity characteristics. This local quality variation compensates for stress-induced errors.
2Device complexity
If sensing elements are positioned uniformly, then the device structure is simplified, but sensitivity to angular acceleration is reduced
Solution Approach 1:
The sensing elements are arranged asymmetrically with respect to the rotation axis, with different numbers and positions of elements at different radial distances. This asymmetric arrangement optimizes the sensitivity to angular acceleration by creating differential sensing patterns that enhance the detection of rotational motion while compensating for mechanical stress effects.
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 configuration reduces output signal offset and increases sensitivity while maintaining low power operation, effectively detecting angular acceleration with improved accuracy and reduced interference from mechanical stress.
Implementation Method 1
detection of angular acceleration is achieved by using one or more capacitive sensors
Data Source
AI summary
Angular accelerometers are described, as are systems employing such accelerometers. The angular accelerometers may include a proof mass and rotational acceleration detection beams directed toward the center of the proof mass. The angular accelerometers may include sensing capabilities for angular acceleration about three orthogonal axes. The sensing regions for angular acceleration about one of the three axes may be positioned radially closer to the center of the proof mass than the sensing regions for angular acceleration about the other two axes. The proof mass may be connected to the substrate though one or more anchors.