Capacitive MEMS Sensor Analog Reset Compensation for Reset Talk-Through
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Solution Overview
Problem
Capacitive micromechanical sensors, such as MEMS sensors, face accuracy issues due to the interference between external acceleration forces and internal electrostatic forces, leading to measurement inaccuracies known as 'reset talk-through', which complicates the compensation of deflections in closed-loop operations.
Innovation Solution
The solution involves compensating for the 'reset talk-through' by adding a signal corresponding to the electrostatic restoring force to the output signal and using a controller to adjust the voltage in a way that counteracts the deflection of the center electrode, with the option of reversing the excitation voltage polarity to prevent signal drifting, employing either a proportional or proportional-integral controller with a complex feedback branch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If closed-loop operation is used to compensate deflection, then measurement accuracy is improved, but reset talk-through interference occurs due to superposition of electrostatic forces on the readout signal
Solution Approach 1:
The patent extracts and separates the reset talk-through component from the total readout signal. By identifying the electrostatic restoring force component and removing it through subtraction, the true deflection measurement is obtained without interference from the reset mechanism.
Solution Approach 2:
The patent introduces an intermediary signal processing step that mediates between the raw readout signal and the final measurement. A controller calculates the reset talk-through component based on the restoring force and subtracts it from the readout signal, acting as an intermediary correction mechanism.
2Stability of the object's composition
If excitation voltage polarity is reversed to prevent signal drifting, then long-term stability is improved, but measurement accuracy may be affected during transition
Solution Approach 1:
The patent implements periodic reversal of the excitation voltage polarity to prevent signal drifting and maintain long-term stability. This periodic action resets any accumulated offset or drift in the measurement system, ensuring consistent performance over time.
Solution Approach 2:
The patent applies preliminary compensation for the polarity reversal effect. Before or during the polarity reversal, the system prepares by adjusting the reset talk-through compensation signal to account for the upcoming polarity change, minimizing measurement disruption.
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 significantly improves the accuracy of MEMS sensors by effectively compensating for measurement inaccuracies caused by internal electrostatic forces, ensuring precise deflection measurement and maintaining signal stability through deterministic or stochastic polarity reversal.
Implementation Method 1
the force acting on the deflection of the center electrode of the differential capacitor is composed of an (external) acceleration force and an (internal) electrostatic force (resetting force)
Implementation Method 2
at least one differential capacitor formed by two fixed electrodes and a resiliently suspended movable center electrode arranged between them
Data Source
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AI summary
The invention relates to a method and a switch arrangement for operating a micromechanical capacitive sensor having at least one, and at most two, fixed electrodes (E1, E2) and one differential capacitor formed by a movable central electrode (EO) that can be deflected by an external force, wherein the deflection of said electrode (EO) is measured. The invention provides that a fraction of the force acting on the central electrode corresponding to the electrostatic restorative force be compensated. Under closed-loop operation of the sensor, the selection signal is influenced by a regulator supplementing a restore-crosstalk signal in such a manner that the created capacitive restorative force acts in a compensatory manner against the deflection of the central electrode. Two embodiments of the invention and a measure supplementing said embodiments for optimizing the control are presented.