MEMS Sensor Merging Rotation and Acceleration Sensing
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Solution Overview
Problem
Conventional MEMS accelerometers cannot sense rotation, and conventional MEMS gyroscopes cannot sense acceleration, requiring separate devices for a six-degree-of-freedom sensing system, which increases manufacturing costs and complexity.
Innovation Solution
A single MEMS device with a proof mass, driving combs, and sensing combs is used, where a DC actuating potential is applied in series with an AC modulation potential to enable simultaneous sensing of rotation and acceleration by demodulating the output signals using different frequency filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate MEMS devices are used for sensing rotation and acceleration, then sensing capability is achieved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines a gyroscope and accelerometer into a single integrated MEMS device that can simultaneously sense both rotation and acceleration. The device uses a single proof mass with both driving combs and sensing combs, eliminating the need for separate devices and reducing overall system complexity while maintaining full sensing capability.
Solution Approach 2:
The MEMS device is designed with multi-functionality to perform both rotational sensing (gyroscopic function) and linear acceleration sensing (accelerometric function) using the same physical structure. The single proof mass and comb structures serve dual purposes, allowing one device to replace two separate specialized devices.
2Adaptability or versatility
If separate MEMS devices are used for sensing rotation and acceleration, then sensing capability is achieved, but manufacturing cost increases
Solution Approach 1:
By merging the gyroscope and accelerometer into a single MEMS device with shared proof mass and comb structures, the patent reduces the total number of devices that need to be manufactured. This consolidation directly lowers manufacturing costs while maintaining the ability to sense both rotation and acceleration.
Solution Approach 2:
The universal design allows a single device to perform multiple sensing functions, reducing the total component count and associated manufacturing expenses. The multi-functional structure eliminates redundant components that would be required if separate specialized devices were used.
3Device complexity
If a single MEMS device senses both rotation and acceleration, then device complexity is reduced, but signal separation becomes more difficult
Solution Approach 1:
The patent employs periodic oscillation of the proof mass at a known frequency to enable signal separation. The driving combs oscillate the proof mass periodically, and the sensing combs detect both rotation and acceleration effects. The periodic motion creates distinct signal characteristics that allow electronic separation of rotation and acceleration components through frequency analysis.
Solution Approach 2:
The oscillatory motion of the proof mass acts as an intermediary mechanism that transforms both rotation and acceleration inputs into detectable capacitance changes with distinguishable characteristics. This intermediate motion state enables the sensing system to separate the two types of signals through appropriate signal processing techniques.
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 approach reduces the number of devices needed, lowers manufacturing costs, and allows for shared sensing circuitry, enabling efficient simultaneous sensing of both rotation and acceleration with improved cost-effectiveness.
Implementation Method 1
the electrostatic force generated by 206 drives the moveable frame 203 and the proof mass 202 to move along the X axis in an oscillation manner
Implementation Method 2
When a linear acceleration is applied in the direction of the Y axis, an inertial force generated by the proof mass 102, due to the inertia of the proof mass 102, causes the sensing comb 105 to deform and in turn changes the capacitance of the comb fingers 105
Implementation Method 3
When a rotation around the Z axis is applied to the system, a Coriolis force is generated by the moving proof mass 202 and the springs deform in the direction of the Y axis
Implementation Method 4
an AC actuating potential is applied to the one or more driving combs such that the proof mass moves in an oscillatory manner
Data Source
AI summary
A MEMS device comprises a proof mass suspended above a substrate, one or more driving combs, and one or more sensing combs. During operation, a DC actuating potential in series with an AC modulation potential is applied to the proof mass, and an AC actuating potential is applied to the one or more driving combs such that the proof mass moves in an oscillatory manner. An inertial sensing system further comprises a sensing element configured to detect a rotation information coupled with an AC signal and an acceleration information coupled with a DC signal.