MEMS Pressure Sensor Electrostatic Servo Control
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Solution Overview
Problem
Existing MEMS and NEMS pressure sensors face limitations in bandwidth and resolution due to mechanical configuration, restricting the operating range and compromising between these parameters, especially in microphone applications where sensitivity to both maximum and minimum sound pressures is crucial.
Innovation Solution
A pressure sensor design with a movable part that includes distinct control and detection means, utilizing capacitive or piezoelectric servo mechanisms to control the displacement of the sensitive element, and electrostatic trimming to reduce mechanical stiffness, allowing for improved performance by decoupling bandwidth and resolution optimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the mechanical configuration of the detection means is optimized for high resolution, then the measurement precision is improved, but the bandwidth is reduced
Solution Approach 1:
The patent replaces the purely mechanical detection system with a hybrid system that uses electrostatic actuation and control. The sensitive element is coupled with electrostatic actuators that can actively control its position, allowing the system to overcome mechanical limitations and achieve high resolution without sacrificing bandwidth through electronic feedback control.
Solution Approach 2:
The patent introduces dynamic control through electrostatic actuators that can actively adjust the position of the sensitive element in real-time. This dynamic compensation allows the system to maintain high resolution measurements while responding quickly to pressure changes, effectively decoupling the resolution-bandwidth trade-off through active feedback control.
2Measurement precision
If the mechanical gain is increased to improve resolution, then the measurement precision is improved, but the dynamic range is reduced
Solution Approach 1:
The patent implements feedback control using electrostatic actuators that receive signals from the detection means and actively adjust the sensitive element's position. This feedback mechanism allows the system to maintain high gain for resolution while compensating for saturation effects, thereby extending the dynamic range through active control rather than being limited by passive mechanical properties.
Solution Approach 2:
The patent changes the operational parameters of the sensitive element by applying electrostatic forces that can dynamically adjust its mechanical properties. Through voltage control of the electrostatic actuators, the system can modify the effective stiffness and position of the sensitive element, allowing optimization of both resolution and dynamic range under different operating conditions.
3Measurement precision
If the sensitive element is made more compliant to improve sensitivity, then the measurement precision is improved, but the structural stability deteriorates
Solution Approach 1:
The patent introduces electrostatic actuators as intermediary elements between the sensitive element and the fixed structure. These actuators provide the necessary support and stability to the compliant sensitive element through electrostatic forces, allowing the element to be highly compliant for sensitivity while the actuator system maintains overall structural stability through active control.
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 enables enhanced sensitivity and dynamic range without compromising bandwidth, allowing for independent optimization of sensor performance parameters, thereby improving the measurement of pressure variations in acoustic pressure applications.
Implementation Method 1
means for detecting the displacement or deformation of the movable part, and of the means for enslaving the displacement or deformation of the sensitive element
Implementation Method 2
the detection means are of the piezoresistive or capacitive type
Implementation Method 3
means for applying trimming to the sensitive element, this trimming making it possible to significantly improve the performance of the sensor
Implementation Method 4
the servo means can be of the piezoelectric type
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 2A'~2A''
AI summary
MEMS and/or NEMS pressure sensor including, in a substrate: a stationary portion and a portion that is movable relative to the stationary portion, the movable portion comprising a sensitive element (108) that is able to move in the plane of the sensor under the effect of a pressure variation; a stress gauge (18) for detecting the movement of the sensitive element (108) in the plane of the sensor due to the pressure variation; electrodes (24.1, 24.2) for actuating the sensitive element, said actuating electrodes being borne partially by the stationary portion and partially by the movable portion, said actuating electrodes being commanded so as to automatically control positionwise the movement of the sensitive element (108); and means (C) for commanding the actuating electrodes, which are configured, on the basis of signals emitted by the gauge, to bias the actuating electrodes so as to automatically control positionwise the movement of the sensitive element.