MEMS Gyroscope Position-Control Driving for Resonance Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing microelectromechanical gyroscopes face challenges in maintaining precise oscillation control due to variations in resonance frequency over time, complexity, and cost associated with feedback driving circuits, particularly in stabilizing the movable mass at the real resonance frequency while suppressing disturbances.
Innovation Solution
A microelectromechanical gyroscope with a hybrid microelectromechanical loop that includes a charge amplifier operating in discrete-time mode, a low-pass filter, and a variable-gain amplifier, along with a phase-locked loop circuit, to control the position of the driving mass and maintain oscillation amplitude close to a reference, using differential capacitive structures and switched-capacitor components for efficient position control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If feedback driving circuits based on sigma-delta modulators are used to stabilize oscillation at resonance frequency, then measurement precision and reliability are improved, but device complexity and manufacturing cost increase due to multiple filtering and processing stages
Solution Approach 1:
The patent extracts and eliminates the complex filtering, decimation, and processing stages from the sigma-delta modulator-based feedback circuit. Instead, it uses a simplified capacitive coupling mechanism that directly transfers the oscillation signal from the driving mass to the sensing mass without requiring multiple intermediate processing stages, thereby reducing circuit complexity while maintaining resonance frequency stabilization capability.
Solution Approach 2:
The patent replaces the electronic feedback control system (with its complex filters and processors) with a direct capacitive coupling mechanism. The electrostatic coupling between the driving mass and sensing mass provides automatic frequency tracking and stabilization without requiring complex electronic processing, substituting a simpler physical mechanism for a complex electronic system.
2Device complexity
If open loop periodic stresses are applied at resonance frequency, then device complexity is reduced, but measurement precision deteriorates because resonance frequency varies over time due to temperature gradients and ageing
Solution Approach 1:
The patent implements a feedback mechanism through capacitive coupling where the sensing mass detects the actual oscillation frequency and automatically adjusts the driving frequency to maintain resonance. This closed-loop feedback is achieved through the natural electrostatic coupling between masses, providing frequency stabilization without complex circuitry, thus resolving the contradiction between simplicity and precision.
Solution Approach 2:
The system uses the sensing mass itself to provide the frequency correction signal through capacitive coupling. The sensing mass automatically detects frequency deviations and the coupled capacitive structure self-adjusts the driving frequency, enabling the system to self-correct resonance frequency drift without external control circuits, combining simplicity with precision.
3Measurement precision
If two separate movable masses are used for driving and sensing, then measurement precision is improved, but device complexity increases due to the complex electromechanical structure
Solution Approach 1:
The patent merges the driving and sensing functions into a single integrated electromechanical structure where two masses are capacitively coupled within one resonant system. This unified structure allows both driving and sensing to occur simultaneously in the same mechanical framework, reducing overall structural complexity while maintaining the precision benefits of separate driving and sensing masses.
Solution Approach 2:
The capacitive coupling structure serves multiple functions simultaneously: it transfers the oscillation signal from the driving mass to the sensing mass, provides frequency stabilization through feedback, and enables angular velocity sensing. This multi-functional design reduces the need for separate components and simplifies the overall electromechanical structure while maintaining measurement precision.
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 solution provides a precise and reliable control of microelectromechanical gyroscope oscillations, reducing complexity and cost, while effectively tracking resonance frequency drifts and improving signal-to-noise ratio, enabling robust angular velocity sensing.
Implementation Method 1
The movable mass is moreover coupled to the fixed body via capacitive structures (capacitors). The movement of the movable mass with respect to the fixed body, for example on account of an external stress, modifies the capacitance of the capacitors, whence the possibility of getting back to the relative displacement of the movable mass with respect to the fixed body
Implementation Method 2
Vice versa, by supplying appropriate biasing voltages, it is possible to apply an electrostatic force to the movable mass to set it in motion
Implementation Method 3
In the case of rotation of the microstructure with respect to a pre-set axis with an angular velocity, is subject to a Coriolis force proportional to the angular velocity itself
Implementation Method 4
A microelectromechanical gyroscope with position-control driving and to a method for controlling a microelectromechanical gyroscope... a phase-locked loop circuit, to control the position of the driving mass and maintain oscillation amplitude close to a reference
Data Source
AI summary
A MEMS gyroscope includes: a microstructure having a fixed structure, a driving mass, movable with respect to the fixed structure according to a driving axis, and a sensing mass, mechanically coupled to the driving mass so as to be drawn in motion according to the driving axis and movable with respect to the driving mass according to a sensing axis, in response to rotations of the microstructure; and a driving device, for keeping the driving mass in oscillation with a driving frequency. The driving device includes a discrete-time sensing interface, for detecting a position of the driving mass with respect to the driving axis and a control stage for controlling the driving frequency on the basis of the position of the driving mass.