Variable Width Torsional Beam Flexure for MEMS Scanner Strain
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Solution Overview
Problem
In MEMS scanning devices, strain sensors often experience inadequate mechanical strain due to the small size of support structures, leading to a low signal-to-noise ratio in feedback signals, which hampers the accuracy of angular position modulation of scanning mirrors.
Innovation Solution
A torsional beam flexure with varying cross-sectional area properties along the rotational axis is designed to maximize mechanical strain at the strain sensor location, ensuring a high signal-to-noise ratio by positioning the sensor where torsional deformation is highest, proximate to the frame mounting location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the strain sensor is positioned on the torsional beam flexure to detect angular position, then the feedback signal accuracy is improved, but the mechanical strain at the sensor location is insufficient due to the small size of the support structure
Solution Approach 1:
The torsional beam flexure is designed with non-uniform cross-sectional properties, creating regions of different stiffness along its length. The strain sensor is strategically positioned at a location where the local geometry maximizes mechanical strain for a given angular displacement, while other regions provide structural support. This local variation in geometric properties allows the sensor to experience sufficient strain without compromising the overall structural integrity of the small support structure.
2Volume of moving object
If the torsional beam flexure is made smaller to reduce device size, then the compactness is improved, but the mechanical strain available for sensing is reduced
Solution Approach 1:
The cross-sectional geometric parameters of the torsional beam flexure are varied along its length to optimize strain distribution. By changing the width, thickness, or moment of inertia at different positions, the beam is designed to concentrate mechanical strain at the sensor location while maintaining overall compact dimensions. This parameter optimization allows the small support structure to generate sufficient strain signal for accurate sensing despite the reduced overall size.
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 increases the proportion of mechanical strain related to the angular position of the scanning mirror, enhancing the accuracy of feedback signals for adjusting drive signals and improving the modulation accuracy of the scanning mirror's angular position.
Implementation Method 1
actuators induce torsional deformation into the torsional beam flexure to cause rotation of the scanning mirror about the rotational axis
Implementation Method 2
a strain sensor may be positioned on a support structure such as a torsional beam flexure which suspends the scanning mirror in relation to a frame
Data Source
AI summary
A microelectromechanical systems (MEMS) scanning device comprising a torsional beam flexure that has a variable width in relation to a rotational axis for a scanning mirror. The geometric properties of the torsional beam vary along the rotational axis to increase a desired mode of mechanical strain at a location where a strain sensor is operating within the MEMS scanning device to generate a feedback signal. The torsional beam flexure mechanically suspends the scanning mirror from a frame structure. During operation of the MEMS scanning device, actuators induce torsional deformation into the torsional beam flexure to cause rotation of the scanning mirror about the rotational axis. The degree or amount of this torsional deformation is directly related to the angular position of the scanning mirror and, therefore, the desired mode of mechanical strain may be this torsional deformation strain component.