MEMS Oscillating-Mass Fault Detection with Lowpass Amplitude Estimation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing fault-detection circuits for MEMS devices, such as MEMS mirrors, are prone to high-frequency noise interference and require complex calibration procedures, leading to performance degradation and increased consumption.
Innovation Solution
A fault-detection circuit that includes a reference generator, multiplier circuits, lowpass filters, and an amplitude-estimator stage to process position signals from MEMS devices, providing resilience to noise and simplified calibration through the use of two thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a differentiator circuit is used downstream of an analog-to-digital converter to reduce response time, then the fault detection speed is improved, but the circuit becomes extremely sensitive to high-frequency noise, degrading performance
Solution Approach 1:
The patent extracts and removes the differentiator circuit from the signal processing chain. Instead of using a differentiator to achieve fast response, the invention directly processes the raw position signal through simple threshold comparison, eliminating the source of high-frequency noise sensitivity while maintaining fast fault detection capability.
Solution Approach 2:
The patent replaces the complex differentiator circuit with a simple threshold comparison mechanism. This simpler, less sophisticated approach (analogous to using a cheap, simple component) achieves the same fault detection function without the harmful side effects of high-frequency noise amplification.
2Reliability
If complex fault-detection circuits are used to improve detection reliability, then measurement precision is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent implements a self-service approach where the fault detection function utilizes the existing position signal and control signal already present in the system. By comparing these existing signals against predetermined thresholds, the system achieves reliable fault detection without requiring additional complex circuitry or increasing power consumption.
Solution Approach 2:
The patent makes the fault detection circuit universal by using the same position signal that is already used for control purposes. The same signal serves dual functions: both for controlling the MEMS device and for detecting faults, eliminating the need for separate dedicated detection circuitry.
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A circuit to detect faults in a MEMS device (2) including a mass (3) that oscillates periodically, which receives a position signal (px[n]) formed by a succession of samples of an analog signal (px(t)) that is a function of the position of the mass (3) and has an amplitude and an oscillation frequency. The circuit includes: a reference stage (32) that generates a first reference signal (xref[n]) and a second reference signal (yref[n]) formed by successions of samples of a first sinusoidal signal and a second sinusoidal signal, respectively, with a frequency equal to the oscillation frequency and phase-shifted by 90°; a first multiplier (34) and a second multiplier (36), which generate, respectively, a first product signal (y[n]) and a second product signal (y[n], x[n]) via multiplication of the position signal by the first reference signal and the second reference signal, respectively; a first filter (40) and a second filter (42) of a lowpass type, which filter, respectively, the first and second product signals (y[n], x[n]) and generate a first filtered signal (YLPF[n]) and a second filtered signal (XLPF[n]); an estimator stage (46), which determines estimates of the amplitude, as a function of the first and second filtered signals (YLPF[n], XLPF[n]); and a decision stage (48), which compares the estimates with a range of values and detects the presence of faults on the basis of the outcomes of the comparisons.