Mixed-Mode Haptic Actuator Drive for Crisp Resonance Control
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Solution Overview
Problem
Vibro-haptic transducers, such as linear resonant actuators, face challenges in maintaining consistent resonance frequency due to variations in individual transducers, device assembly, aging, self-heating, and user interaction, leading to inefficient generation of tonal vibrations and a 'mushy' tactile response instead of a 'crisp' one.
Innovation Solution
A transducer driving system that seamlessly switches between open loop and negative impedance closed loop modes, using a mode switch to transition between these modes and employing a control subsystem to generate playback waveforms, effectively reducing coil impedance and improving transducer dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the transducer operates in open loop mode, then the device complexity is reduced, but the manufacturing precision and resonance frequency consistency deteriorate
Solution Approach 1:
The patent implements a feedback control mechanism that monitors the actual resonance frequency of the transducer and dynamically adjusts the drive signal frequency to maintain optimal operation. This feedback loop compensates for variations in transducer characteristics, assembly differences, and environmental changes, thereby maintaining manufacturing precision without requiring overly complex manual calibration systems.
Solution Approach 2:
The system dynamically changes the operating parameters (specifically frequency) based on detected transducer characteristics. By measuring the actual resonance frequency and adjusting the drive signal accordingly, the system adapts to individual transducer variations and maintains consistent performance across different manufacturing batches and operating conditions.
2Reliability
If the transducer operates in closed loop mode with negative impedance, then the transducer dynamics and response crispiness are improved, but the device complexity increases
Solution Approach 1:
The closed-loop mode employs negative impedance feedback that actively counteracts the transducer's natural resonance characteristics. By injecting a feedback signal with opposite phase and adjusted amplitude, the system dampens unwanted ringing and sharpens the tactile response, achieving superior reliability and response quality.
Solution Approach 2:
The system dynamically changes the impedance characteristics of the drive circuit by switching between different operational modes (open loop and closed loop with negative impedance). This parameter change allows the system to optimize for either simplicity or performance depending on the specific operating requirements.
3Adaptability or versatility
If the system switches between open loop and closed loop modes, then the adaptability to different operating conditions is improved, but the device complexity increases
Solution Approach 1:
The system implements dynamic mode switching capability that allows transition between open-loop and closed-loop operational states. This dynamic adaptability enables the system to optimize performance for different types of haptic events (e.g., using closed-loop for sustained tonal vibrations requiring precision, and open-loop for simple transient effects), while the switching mechanism itself is managed through integrated control logic that minimizes added 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
This approach enhances the transducer's response by minimizing ringing and achieving a more 'crisp' tactile feedback, maintaining consistent haptic effects across varying conditions and reducing latency in haptic feedback control.
Implementation Method 1
An LRA may be modelled as a mass-spring electro-mechanical vibration system... The driving amplifier outputs the voltage waveform V(t)... The mass-spring system 201 moves with velocity u(t)
Implementation Method 2
In order to generate tonal vibration notifications efficiently, it may be desirable to operate the haptic actuator at its resonance frequency... The resonance frequency f0 of a haptic transducer may be approximately estimated as...
Implementation Method 3
An LRA may be modelled as a mass-spring electro-mechanical vibration system... LRAs are non-linear components that may behave differently depending on, for example, the voltage levels applied, the operating temperature, and the frequency of operation
Implementation Method 4
Re and Le are the DC resistance and coil inductance of the coil-magnet system, respectively; and Bl is the magnetic force factor of the coil
Data Source
AI summary
In accordance with embodiments of the present disclosure, a method of driving a playback waveform to an electromagnetic actuator by a transducer driving system may include operating the transducer driving system in a first mode wherein the electromagnetic actuator is driven with the playback waveform in a closed loop to form a closed-loop voltage drive system that includes a negative impedance, operating the transducer driving system in a second mode wherein the electromechanical actuator is driven with the playback waveform in an open loop, and operating a mode switch for transitioning the transducer driving system to operate between the first mode and the second mode.