Scanning MEMS Mirror Leaf-Spring Coupling for Vibration Robustness
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Solution Overview
Problem
Existing MEMS scanning mirrors for automotive LIDAR applications face challenges with low eigenfrequencies of undesirable modes, such as in-plane translation (Tx) and out-of-plane rotation (Rz), leading to increased sensitivity to vibrations and reduced robustness due to the use of relief springs that introduce non-linear effects and mechanical stresses.
Innovation Solution
A MEMS scanning mirror design featuring a mirror body with a coupling element comprising a bridge section and parallel leaf spring sections, which enhances stiffness in the X-direction by eliminating relief springs, thereby increasing the eigenfrequency of undesirable modes and reducing sensitivity to vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If relief springs are used to mitigate stiffening behavior of leaf springs at larger tilt angles, then the achievable tilt angle is increased, but the translational stiffness in the X-direction is reduced, leading to lower eigenfrequency of the translational eigenmode Tx and increased sensitivity to vibration
Solution Approach 1:
The patent removes the relief springs from the suspension system entirely. By extracting this component, the invention eliminates the trade-off between tilt angle and vibration sensitivity, achieving both large scan angles and high vibration resistance through the optimized leaf spring configuration alone
Solution Approach 2:
The patent modifies the geometric parameters of the leaf springs (width, thickness, length ratios) to change their mechanical properties. By optimizing these parameters, the leaf springs can accommodate large tilt angles while maintaining high translational stiffness, thus increasing the eigenfrequency of the Tx mode and reducing vibration sensitivity
2Reliability
If the eigenfrequency of undesirable modes is increased to reduce sensitivity to vibration, then the robustness is improved, but the device complexity increases due to the need for optimized coupling elements with multiple leaf spring sections
Solution Approach 1:
The coupling element is segmented into multiple leaf spring sections (first, second, and optionally third leaf spring sections) with different geometric parameters. This segmentation allows each section to contribute differently to the overall stiffness characteristics, enabling independent optimization of various eigenfrequencies without requiring complex external components
Solution Approach 2:
The coupling element with multiple leaf spring sections serves multiple functions simultaneously: it provides the desired rotational stiffness for scanning motion, suppresses undesirable translational and rotational modes, and enables large tilt angles. This multi-functionality is achieved within a single integrated component rather than through multiple separate elements
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
The improved design achieves higher eigenfrequencies for undesirable modes, enhancing the mirror's robustness and reducing sensitivity to vibrations, while maintaining a high stiffness and allowing for larger tilt angles without introducing non-linear effects.
Implementation Method 1
a first leaf spring section and a second leaf spring section... The first and the second leaf spring section each preferably have a length in the second planar direction that is larger than a length of the bridge section in the first planar direction
Implementation Method 2
at least one coupling element that biases the mirror body towards a neutral state wherein a mirror surface of the mirror body is parallel with a reference plane
Data Source
AI summary
The improved scanning MEMS mirror device disclosed herein comprises a mirror body that is rotatable around a rotation axis with respect to a stationary body, wherein a rotation of the mirror body is flexibly restrained with at least one coupling element that biases the mirror body towards a neutral state. The coupling element comprises at least a bridge section and a first leaf spring section and a second leaf spring section. The first leaf spring section extends in an extension direction from a first end thereof at the bridge section towards a second end thereof that is connected to the mirror body. The second leaf spring section extends in an extension direction from a first end thereof at the bridge section towards a second end thereof where it is connected to the stationary body. The extension direction of the first leaf spring section and the extension direction of the second leaf spring section are at least substantially the same as the second planar direction. The leaf spring sections have a thickness defined in a direction orthogonal to the reference plane that is smaller than their width, defined in said first planar direction. The construction of the improved scanning MEMS mirror device results in an increased eigenfrequency of undesirable eigenmodes.