Interference Mitigation in Impedance Sensing Systems
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Solution Overview
Problem
Existing methods for monitoring complex impedances in vibro-haptic transducers, such as linear resonant actuators, face challenges in accuracy and precision due to noise and interference, which affect the measurement of displacement and resonance frequency, leading to potential damage and suboptimal performance.
Innovation Solution
A system comprising driving circuitry, sensing circuitry to detect physical quantities, and interference detection circuitry to mitigate interference, allowing for accurate impedance measurement and displacement control in vibro-haptic transducers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If impedance sensing is performed in vibro-haptic transducers, then displacement measurement capability is improved, but measurement precision deteriorates due to noise and interference
Solution Approach 1:
The patent introduces an intermediary frequency component (pilot tone) that is modulated by the displacement signal. This pilot tone acts as a carrier wave that transports the displacement information through the system, allowing the sensing circuitry to extract displacement data by detecting variations in the pilot tone's frequency or phase, thereby overcoming the noise and interference that would directly corrupt a simple impedance measurement
Solution Approach 2:
The patent applies partial action by using a specific frequency range (above the audio bandwidth) for the pilot tone that is excessive for normal audio operation but necessary for accurate sensing. This higher frequency component allows the system to measure displacement without being affected by the same noise and interference that impact lower frequency audio signals
2Reliability
If displacement measurement is implemented to protect transducers, then transducer protection capability is improved, but device complexity increases due to additional sensing circuitry
Solution Approach 1:
The patent makes the output transducer multi-functional by using it both for audio/haptic output and for sensing displacement measurements. The same transducer that produces the audio signal also serves as the sensing element by modulating the pilot tone frequency according to its displacement, eliminating the need for separate sensing transducers or complex sensing circuitry
Solution Approach 2:
The patent merges the audio output function and the displacement sensing function into a single integrated system. The pilot tone generation, modulation, and detection are combined with the existing audio amplification and transducer drive circuitry, allowing displacement measurement capability to be added without proportionally increasing overall device complexity
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 solution enhances the accuracy and precision of impedance measurement and displacement control, reducing the risk of damage to vibro-haptic transducers and improving their performance by effectively mitigating noise and interference.
Implementation Method 1
the back-EMF voltage VB(t) associated with the haptic transducer. Sensed terminal voltage VT(t) may be given by: V(t) − I(t) · Ro = VT(t) = I(t) · ZCOIL(t) + VB(t)
Implementation Method 2
An LRA may be modelled as a mass-spring electro-mechanical vibration system. Bl is the magnetic force factor of the coil
Data Source
AI summary
A system may include driving circuitry configured to drive a driving signal to an output transducer, sensing circuitry configured to sense a physical quantity associated with the output transducer in response to the driving signal, and interference detection circuitry configured to detect the presence of interference of the system and mitigate the effect of the interference in the system.