Mechanical Low Pass Filter for Motion Sensor Vibration Isolation
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Solution Overview
Problem
Motion sensors in compact consumer electronics face interference from mechanical vibrations, leading to noise and error in output due to resonance behaviors, which conventional electrical low-pass filters inadequately address, especially in low power applications.
Innovation Solution
A mechanical low-pass filter is integrated into the motion sensor package using a mechanically compliant suspension system comprising dampers and metal springs, with a resonant frequency higher than the sensing bandwidth but lower than the motion sensor's resonant frequency, to attenuate out-of-band vibrations and improve stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an electrical low-pass filter is implemented at the output of the motion sensor, then the signal outside the defined bandwidth is attenuated, but the filter consumes power which limits its utility in low power applications
Solution Approach 1:
The patent replaces the electrical low-pass filter with a mechanical low-pass filter consisting of a mass-spring-damper system. The mechanical filter physically isolates the motion sensor from vibrations outside the defined bandwidth through mechanical resonance characteristics, eliminating the need for power-consuming electrical filtering components while achieving the same noise attenuation function.
Solution Approach 2:
The patent introduces a mechanical intermediary system (mass-spring-damper) between the vibration source and the motion sensor. This intermediary mechanically filters out-of-band vibrations before they reach the sensor, serving as a physical mediator that protects the sensor from harmful vibrations without requiring active power consumption.
2Reliability
If the resonant frequency of the mechanical suspension system is set higher than the sensing bandwidth but lower than the motion sensor resonant frequency, then out-of-band vibrations are attenuated and sensor stability is improved, but the device complexity increases
Solution Approach 1:
The patent merges the mechanical suspension system with the motion sensor package, integrating the mass-spring-damper filter directly into the sensor assembly. This consolidation achieves vibration isolation and sensor stabilization while minimizing additional device complexity by combining filtering functionality with the existing sensor structure rather than adding separate external components.
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 mechanical suspension system effectively isolates the motion sensor from unwanted vibrations and package strain, enhancing sensor stability and reducing noise, with improved frequency response and power efficiency.
Implementation Method 1
the one or more metal springs and dampers provide a mechanical suspension system having a resonant frequency that is higher than a sensing bandwidth of a motion sensor in the sensor stack and lower than a resonant frequency of the motion sensor
Implementation Method 2
mechanical vibrations from speakers, vibrators or other system components can impact the desired motion signal by inducing noise and error in the motion sensor output
Implementation Method 3
one or more mechanically compliant dampers formed on the substrate
Data Source
AI summary
Mechanical low pass filters for motion sensors and methods for making same are disclosed. In some implementations, a motion sensor package comprises: a substrate; one or more mechanically compliant dampers formed on the substrate; one or more mechanically compliant metal springs formed on the one or more dampers and the substrate; and a sensor stack attached to the one or more metal springs, wherein the one or more metal springs and dampers provide a mechanical suspension system having a resonant frequency that is higher than a sensing bandwidth of a motion sensor in the sensor stack and lower than a resonant frequency of the motion sensor.