Haptic Transducer Impedance Estimation for Consistent Tactile Feedback
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Solution Overview
Problem
Existing haptic transducers face challenges in maintaining consistent resonance frequency due to variations in individual transducers, device assembly, aging, and user interaction, leading to unpredictable vibro-haptic feedback.
Innovation Solution
A method and system for estimating the impedance of an electromagnetic load in haptic transducers, which involves selecting an appropriate measurement technique based on the load conditions and performing the selected technique to generate an impedance estimate, thereby effectively reducing coil resistance and improving transducer dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional impedance measurement techniques are used, then measurement simplicity is maintained, but measurement precision deteriorates due to sample-to-sample variations and changing operating conditions
Solution Approach 1:
The system dynamically selects between different impedance measurement techniques (DC resistance measurement, AC impedance measurement, or pilot tone measurement) based on real-time operating conditions such as transducer state, temperature, and signal level. This dynamic adaptation allows the system to maintain high measurement precision across varying conditions without requiring all measurement circuits to be active simultaneously, thus managing device complexity effectively.
Solution Approach 2:
The system changes measurement parameters (frequency, amplitude, measurement timing) based on operating conditions. For example, it uses DC resistance measurement when the transducer is inactive, AC impedance measurement during operation, and pilot tone measurements for tracking changes. This parameter adaptation enables accurate impedance estimation across different transducer states without requiring a single complex measurement system.
2Use of energy by moving object
If the transducer is operated at resonance frequency for efficient tonal vibration, then energy efficiency is improved, but reliability deteriorates due to unpredictable resonance frequency variations
Solution Approach 1:
The system continuously monitors transducer impedance using multiple measurement techniques and uses this feedback to track resonance frequency variations. By measuring impedance at different frequencies and analyzing the resonance peak, the system can identify shifts in resonance frequency caused by sample variations, aging, or temperature changes, and adjust the driving frequency accordingly to maintain efficient operation.
Solution Approach 2:
The system performs preliminary impedance measurements during manufacturing and assembly to establish baseline characteristics for each transducer. This preliminary characterization allows the system to pre-compensate for sample-to-sample variations and predict resonance frequency drift over time, enabling more reliable efficient operation throughout the transducer's lifetime.
3Measurement precision
If multiple impedance measurement techniques are available, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system dynamically selects between different impedance measurement techniques (DC resistance measurement, AC impedance measurement, or pilot tone measurement) based on real-time operating conditions such as transducer state, temperature, and signal level. This dynamic adaptation allows the system to maintain high measurement precision across varying conditions without requiring all measurement circuits to be active simultaneously, thus managing device complexity effectively.
Solution Approach 2:
The measurement system is segmented into distinct functional blocks: a DC resistance measurement circuit for low-frequency measurements, an AC impedance measurement circuit for operational measurements, and a pilot tone generation and measurement system for tracking changes. Each segment handles specific measurement tasks, allowing independent optimization and simplifying the overall system architecture while maintaining comprehensive measurement capability.
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 proposed solution enhances the accuracy of impedance estimation, reduces the quality factor of the transducer, decreases attack time, and minimizes ringing, resulting in a more crisp and consistent tactile response in haptic applications.
Implementation Method 1
Vibro-haptic transducers, for example linear resonant actuators (LRAs), are widely used in portable devices such as mobile phones to generate vibrational feedback
Implementation Method 2
selecting, based on a condition of an electromagnetic load, a selected measurement technique from a plurality of impedance measurement techniques for measuring an impedance of the electromagnetic load
Data Source
AI summary
A method may include selecting, based on a condition of an electromagnetic load, a selected measurement technique from a plurality of impedance measurement techniques for measuring an impedance of the electromagnetic load and performing the selected measurement technique to generate an estimate of the impedance of the electromagnetic load.