Electrostatic Pendular Accelerometer Feedback Control
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Solution Overview
Problem
Electrostatic pendulum accelerometers face challenges due to manufacturing asymmetries, non-linearities, and reduced bandwidth, which affect their performance and accuracy in measuring acceleration, particularly in maintaining the pendulum's position and estimating acceleration with high precision.
Innovation Solution
The solution involves an electrostatic pendulum accelerometer with a driver circuit connected to a switch that selectively connects the electrodes to an excitation circuit, using pulses to maintain the pendulum's set position and determine acceleration, and a control circuit that alternately energizes the electrodes to detect capacitance differences and calculate the necessary command to control the pendulum's position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If closed-loop operation is used to maintain pendulum position, then measurement precision is improved, but device complexity increases due to servo control circuits
Solution Approach 1:
The patent implements closed-loop feedback control by continuously monitoring the capacitance difference between fixed electrodes and applying corrective electrostatic forces to maintain the pendulum at its neutral position. The control circuit measures the capacitance values, calculates the difference, and generates appropriate control signals to counteract any displacement, thereby achieving high measurement precision through feedback mechanisms.
2Device complexity
If all-or-nothing control with calibrated voltage pulses is used, then device complexity is reduced, but measurement precision deteriorates due to pulse symmetry requirements
Solution Approach 1:
The patent replaces the mechanical all-or-nothing pulse control system with an electrostatic field-based continuous control system. Instead of using calibrated voltage pulses that require precise symmetry, the invention uses continuous electrostatic forces generated by controlled voltage application to the fixed electrodes, allowing for smoother and more precise pendulum position control without the limitations of discrete pulse timing.
3Ease of operation
If the pendulum is made movable in pivoting to detect displacements, then ease of operation is improved, but manufacturing precision requirements increase due to asymmetries
Solution Approach 1:
The patent uses feedback control to compensate for manufacturing asymmetries in the pivoting pendulum structure. By continuously monitoring the capacitance values from the fixed electrodes and applying corrective electrostatic forces, the system can maintain accurate measurements even when the pendulum geometry has slight manufacturing variations. The feedback loop automatically adjusts for these asymmetries without requiring ultra-precise manufacturing.
4Productivity
If the pendulum natural frequency is increased to improve bandwidth, then productivity is improved, but measurement precision deteriorates due to reduced electrostatic force effectiveness
Solution Approach 1:
The patent employs parameter changes in the electrostatic control system to maintain precision across different bandwidth requirements. By dynamically adjusting the control voltage parameters and electrostatic force magnitude, the system can effectively control the pendulum at higher frequencies without sacrificing measurement accuracy. The adaptive parameter adjustment allows the servo control to remain effective even when the pendulum operates at higher natural frequencies for improved bandwidth.
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 improves the accuracy and precision of acceleration measurement by minimizing the impact of manufacturing asymmetries and non-linearities, allowing for better control of the pendulum's position and estimation of acceleration, thereby enhancing the overall performance of the sensor.
Implementation Method 1
Each fixed electrode forms with the movable electrode a capacitance whose value depends on their spacing
Implementation Method 2
The electrostatic force must therefore compensate for the acceleration applied along the sensitive axis
Data Source
AI summary
Accelerometric sensor, comprising at least one electrostatic pendular accelerometer having a first fixed electrode and a second fixed electrode which are fixed to a housing and which are linked to an excitation circuit and a third electrode which is carried by a pendulum linked to the housing so as to be mobile and which is linked to a detection circuit. The excitation circuit has an output hooked up to a switch linked to the first and second electrodes, the switch having a first connection position and a second connection position for selectively hooking the first electrode and the second electrode up to the excitation circuit. The detection circuit, the excitation circuit, the switch and the detection circuit are linked to a control circuit arranged so that the first and second electrodes are excited by pulse trains in such a way as to maintain the pendulum in a preset position and to determine an acceleration undergone by the pendulum. Method of controlling such a sensor.