MEMS Inertial Sensor Dynamic Balancing via Electrostatic Springs
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Solution Overview
Problem
Vibrating angular inertial sensors, particularly MEMS-type sensors, face challenges in precision due to manufacturing defects causing dynamic unbalance, which leads to energy loss and measurement difficulties, especially in small sensors where correction by material removal is impractical and temperature-dependent.
Innovation Solution
A MEMS-type vibrating inertial angular sensor design featuring concentrically mounted solid bodies with electrostatic actuators and detectors, coupled through isotropic suspension means to a fixed frame, allowing for double suspension and mechanical coupling without levers, enabling dynamic balancing by controlling electrostatic springs based on unbalance measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If manufacturing precision is improved, then dynamic imbalance is reduced, but sensor size must be reduced which makes measurement of imbalance forces too small to detect
Solution Approach 1:
The patent introduces an intermediary measurement approach by measuring the vibration amplitude of the resonator itself rather than directly measuring the tiny imbalance forces. The unbalance detector measures the vibration caused by the imbalance, which is a larger signal that can be detected with standard sensors, thus solving the measurement precision problem without requiring larger sensor size.
2Manufacturing precision
If correction by localized material removal is applied, then dynamic imbalance is corrected, but the correction does not compensate for imbalance evolution over temperature and time
Solution Approach 1:
The patent transitions from static correction (material removal) to dynamic correction using electrostatic springs that can be actively controlled. The electrostatic springs allow real-time adjustment of the resonator's vibration characteristics to compensate for temperature and time-induced imbalance changes, providing both initial correction and ongoing stability.
Solution Approach 2:
The patent changes the physical state from passive mechanical correction to active electrostatic control. By varying the electrostatic spring parameters (voltage), the system can dynamically adjust the resonator's behavior to compensate for environmental changes, achieving both initial balancing and long-term stability.
3Manufacturing precision
If multiple massive bodies are used, then first-order balancing is achieved, but the construction becomes complex with multiple coupling levers
Solution Approach 1:
The patent extracts the coupling function from complex mechanical levers and integrates it into the suspension system itself. The suspension elements simultaneously provide mechanical support and the necessary coupling between massive bodies, eliminating the need for separate coupling levers and simplifying the overall construction while maintaining first-order balancing capability.
4Manufacturing precision
If rigid fixation of unbalanced resonator on large recoil mass is applied, then dynamic imbalance is suppressed, but vibration sensitivity and mechanical strength are reduced
Solution Approach 1:
The patent uses dynamic electrostatic springs instead of rigid fixation. The electrostatic springs can actively counteract imbalance forces while maintaining the resonator's mechanical strength and vibration sensitivity. The springs provide the necessary stiffness when needed but allow the resonator to maintain its vibrational characteristics.
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 enhances sensor performance by isolating mass bodies from frame deformations, simplifying structure and balancing, and allowing for effective dynamic balancing without precise voltage references, thus improving precision and stability across varying conditions.
Implementation Method 1
Each sensor includes actuators arranged to vibrate the deformable resonator or the solid body/elastic elements system at the system's resonant frequency
Implementation Method 2
detectors of the deformations of the deformable resonator or the movements of the solid body/elastic elements system are mounted between the support on one side and the deformable resonator or the solid body/elastic elements system on the other
Implementation Method 3
The resonator can also consist of one or more rigid solid bodies (also commonly called masses or test masses) connected to a support by elastic elements
Implementation Method 4
The support is connected by second means for suspening the massive bodies to a fixed frame such that the massive bodies and the support are movable relative to the fixed frame parallel to a suspension plane, the suspension means being isotropic along the suspension plane
Implementation Method 5
enabling dynamic balancing by controlling electrostatic springs based on unbalance measurements
Data Source
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AI summary
The invention relates to a vibrating MEMS inertial angular sensor including a substrate (1) for supporting at least two mass bodies (2) that are mobile relative to the substrate and associated with at least one electrostatic actuator (3) and at least one electrostatic sensor (4). The sensor includes first means for suspending the mass bodies relative to the substrate and means for coupling the mass bodies together. The substrate is connected to a stationary frame by second suspension means. The invention also relates to a method for balancing such a sensor.