MEMS Accelerometer Observer for Temperature Bias Compensation
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Solution Overview
Problem
Conventional MEMS accelerometers are agnostic to temperature effects, leading to deformation of capacitor plates and additional bias errors in acceleration estimation, and fail to accurately estimate input acceleration when the proof-mass is not stabilized in the zero steady state position.
Innovation Solution
A MEMS accelerometer system with an observer module that includes a displacement calculator, drive acceleration calculator, and observer dynamics module, which uses temperature readings to estimate input acceleration and filter noise, employing deterministic mathematical equations to improve estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional MEMS accelerometer methods are used, then the system structure is simple, but temperature variations cause capacitor plate deformation and additional bias errors in acceleration estimation
Solution Approach 1:
A temperature sensor is introduced as an intermediary device to measure temperature variations. The temperature signal is then fed to the observer module which uses it to compensate for capacitor plate deformation effects, thereby improving acceleration estimation accuracy without fundamentally changing the core accelerometer structure.
Solution Approach 2:
The patent replaces direct mechanical compensation methods with a signal processing approach. Instead of mechanically compensating for temperature effects, the system uses an observer module that processes temperature signals and capacitance signals to mathematically compensate for thermal deformation effects on the proof mass and capacitor plates.
2Measurement precision
If the controller operates on proof-mass displacement to generate drive commands, then the system can maintain proof-mass at zero position in steady state, but the controller output is not a good estimate of input acceleration when proof-mass is not stabilized
Solution Approach 1:
The observer module implements feedback by continuously monitoring the proof-mass position and velocity, and using this information to update the acceleration estimate. The observer uses the actual proof-mass displacement and the drive acceleration to correct and refine the acceleration estimation, ensuring accuracy both in steady state and during transient motion.
Solution Approach 2:
The patent introduces dynamic modeling of the proof-mass system, treating it as a second-order linear dynamic system. The observer module dynamically adjusts its estimation based on the real-time state of the proof-mass, using differential equations to model the system behavior and provide accurate acceleration estimates during transient conditions.
3Adaptability or versatility
If temperature effects are ignored, then the system is agnostic to thermal variations, but capacitor plate material deformation causes additional temperature attributed bias error
Solution Approach 1:
The temperature sensor provides continuous feedback on thermal conditions to the observer module. This temperature information is fed back into the system to dynamically adjust the acceleration estimation, allowing the accelerometer to adapt to temperature variations and maintain measurement accuracy across different thermal environments.
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
The system reduces bias errors due to temperature variations and improves estimation accuracy by accurately tracking input acceleration, even during transient motion and steady state, with enhanced noise rejection and flexibility to operate at different performance grades.
Implementation Method 1
in cases/applications where significant temperature variations are developed the MEMS formed capacitor plates material can deform, and, hence the overall capacitance changes resulting in an additional temperature attributed bias error in the estimated acceleration
Implementation Method 2
external applied specific acceleration (hereafter called the input acceleration) displaces a proof-mass and varies the distance of the formed capacitor plates, and, hence the overall capacitance. The above capacitance variation is transduced to an electrical voltage by a displacement transducer
Data Source
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AI summary
A MEMS accelerometer system can include a proof mass device having a proof mass configured to move from an initial position in response to an input acceleration, a transducer operatively connected to the proof mass device to output a transducer signal correlating to a movement and/or position of the proof mass, a driver operatively connected to the proof mass device and configured to drive the proof mass, and a controller operatively connected to the driver to control the driver. The controller is operatively connected to the transducer to receive the transducer signal and output a drive signal to the driver to drive the proof mass toward an initial position. The system can include an observer module operatively connected to the controller to receive the drive signal. The observer module can be operatively connected to the transducer to receive the transducer signal. The observer module can be configured to deterministically estimate the input acceleration based on the transducer signal and the drive signal based on a deterministic model. The observer module can be configured to output an estimated input acceleration signal.