Electrostatic Acceleration Sensor with Offset Link Beams
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Solution Overview
Problem
Conventional acceleration sensors face increased detection errors due to inability to distinguish between rotations caused by acceleration in the substrate thickness direction and those caused by other axes, angular acceleration, and angular velocity.
Innovation Solution
The acceleration sensor design incorporates first and second torsion beams, detection frames, link beams, and an inertia mass body, where the link beams are offset to cause opposite rotational displacements of the detection frames, allowing for increased sensitivity only when detecting acceleration in the intended direction and suppressing sensitivity to other axes and angular motions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single detection frame and torsion beam configuration is used, then the device complexity is reduced, but the measurement precision deteriorates due to inability to distinguish acceleration from other rotational motions
Solution Approach 1:
The single detection system is segmented into two independent detection frames (first detection frame and second detection frame) with separate torsion beams. Each frame-torsion beam assembly responds to acceleration differently due to their offset positions, allowing the system to distinguish between acceleration-induced rotation and other rotational motions by comparing the responses of the two segments.
Solution Approach 2:
The first link beam and second link beam are positioned asymmetrically with offset distances from their respective torsion axes. The first offset distance and second offset distance are designed to be different, creating asymmetric mechanical leverage that causes the two detection frames to respond differently to the same acceleration input. This asymmetry enables the system to differentiate acceleration signals from other rotational disturbances.
2Manufacturing precision
If the link beams are positioned at the torsion axis, then the manufacturing precision is simplified, but the sensitivity to acceleration in the intended direction is reduced
Solution Approach 1:
Instead of positioning both link beams at the torsion axis (uniform quality), the invention applies different local qualities by offsetting the first link beam from the first torsion axis by a first offset distance and the second link beam from the second torsion axis by a second offset distance. This localized positional differentiation optimizes the mechanical advantage for acceleration detection while maintaining manufacturability through defined offset parameters.
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 effectively reduces detection errors from non-intended axis accelerations and angular motions, enhancing the precision of acceleration measurements in the intended direction.
Implementation Method 1
The plurality of detection electrodes are provided for detecting an angle formed between the substrate and each of the first and second detection frames on the basis of electrostatic capacitance
Implementation Method 2
The first torsion beam can be distorted around a first torsion axis, and is supported by the substrate. The first detection frame is supported by the substrate with the first torsion beam so as to be rotatable about the first torsion axis.
Implementation Method 3
When acceleration in the substrate thickness direction is applied to the acceleration sensor, inertia force in the substrate thickness direction acts on the inertia mass body. Since the inertia mass body is provided on the one end part, that is, at a position deviated from the axis of rotation in the substrate in-plane direction, this inertia force acts on the detection frame as a torque around the torsion beam.
Data Source
AI summary
First and second detection frames are supported by a substrate to be rotatable about first and second torsion axes. A first link beam is connected to the first detection frame on an axis located at a position moved from a position of the first torsion axis in a first direction crossing the first torsion axis and directed to one end side of the first detection frame. A second link beam is connected to the second detection frame on an axis located at a position shifted from a position of the second torsion axis in a second direction opposite to the first direction. An inertia mass body is displaceable in a thickness direction of the substrate by being linked with the first and second detection frames by the first and second link beams, respectively. This constitution makes it possible to obtain a highly precise acceleration sensor hardly influenced by disturbances.