Strain Sensors on Outer Hinges for Dual-Axis Mirror Rotation
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Solution Overview
Problem
In rotating mechanical devices, such as scanning micromirrors, existing strain sensors face challenges with long electrical traces that are prone to breakage and interference when located on inner hinges, particularly in multi-axis MEMS devices, where these traces must navigate around the gimbal and across narrow hinges.
Innovation Solution
Positioning strain sensors on the outer hinges to monitor the rotation-induced bending stress, which provides a reliable signal for the inner hinge rotation, thereby shortening electrical traces and reducing fabrication difficulties and interference issues, while using pairs of sensors for enhanced precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain sensors are positioned on inner hinges to directly monitor rotation, then measurement precision is improved, but electrical traces become long and prone to breakage and interference
Solution Approach 1:
The patent uses the outer hinge as an intermediary structure to sense the rotation of the inner hinge. By positioning strain sensors on the outer hinge and utilizing the mechanical coupling between the inner and outer hinges, the system indirectly measures inner hinge rotation without requiring electrical traces to be located on the inner hinge itself, thus avoiding trace breakage and interference issues
2Measurement precision
If strain sensors are positioned on inner hinges, then direct rotation sensing is achieved, but fabrication difficulty increases due to narrow hinge spaces
Solution Approach 1:
Instead of placing sensors on the inner hinge as conventionally done, the patent inverts the approach by placing strain sensors on the outer hinge. This inversion allows sensors to be positioned in a more accessible location with sufficient space for electrical traces and bonding pads, significantly easing fabrication while still enabling accurate inner hinge rotation sensing through the mechanical relationship between the hinges
3Adaptability or versatility
If electrical traces are extended to reach inner hinge sensors, then sensing capability is maintained, but interference and breakage risk increase
Solution Approach 1:
The outer hinge serves as an intermediary platform that allows electrical traces to be routed away from the narrow inner hinge region. This intermediary positioning maintains the sensing capability through mechanical coupling while eliminating the harmful effects of long, vulnerable electrical traces that would otherwise be required to reach sensors on the inner hinge
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 effectively monitors and controls the rotation of scanning mirrors by providing accurate signals for both inner and outer hinge rotations, improving precision and reliability, and reducing the risk of trace breakage and interference.
Implementation Method 1
One or more strain sensors are disposed on at least one of the first hinges and are configured to provide a signal indicative of a rotation of the rotating element about the second axis relative to the gimbal
Data Source
AI summary
Mechanical apparatus includes a rotational assembly, including a frame and a gimbal, which is attached to the frame by first hinges disposed along a first axis and is configured to rotate on the first hinges about the first axis relative to the frame. A rotating element is attached to the gimbal by second hinges disposed along a second axis, perpendicular to the first axis, and is configured to rotate on the second hinges about the second axis relative to the gimbal. One or more strain sensors are disposed on at least one of the first hinges and configured to provide a signal indicative of a rotation of the rotating element about the second axis relative to the gimbal. Control circuitry is configured to monitor the rotation of the rotating element about the second axis responsively to the signal.