Haptic Actuator Calibration Using Back-EMF for Consistent Feedback
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Solution Overview
Problem
Haptic systems in electronic devices experience variations in haptic effects due to manufacturing deviations and material variations, leading to inconsistent user experiences, and these effects can drift over time, failing to meet user expectations.
Innovation Solution
A calibration method for haptic systems that generates a drive signal, detects and analyzes the back Electromotive Force (bEMF) signal from an actuator, adjusts the drive signal to match a target waveform, and stores the adjusted scale, allowing for on-chip calibration without external sensors, enabling efficient factory or user calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If manufacturing processes are used to produce haptic devices, then devices can be mass-produced, but haptic effects vary due to manufacturing deviations and material variations
Solution Approach 1:
The patent applies parameter changes by adjusting the drive signal characteristics (amplitude, frequency, duration) based on measured actuator properties. The calibration process modifies signal parameters to compensate for manufacturing variations, ensuring consistent haptic effects across mass-produced devices despite differences in actuator properties.
Solution Approach 2:
The patent implements feedback by measuring the back EMF signal from the actuator and using this information to adjust the drive signal parameters. This closed-loop approach allows the system to automatically compensate for manufacturing deviations and material variations, maintaining haptic effect consistency across mass-produced devices.
2Ease of operation
If haptic systems are used in electronic devices, then tactile feedback is provided to users, but haptic effects drift over time due to actuator property changes
Solution Approach 1:
The patent applies preliminary action by performing calibration before normal device operation begins. The calibration process pre-adjusts the drive signal parameters based on initial actuator measurements, establishing correct operating parameters before the actuator properties can drift through use. This preventive approach maintains haptic effect stability over time.
Solution Approach 2:
The patent implements self-service by enabling the device to automatically calibrate itself using its own resources (microphone, speaker, processor). The system performs self-diagnosis and self-adjustment of haptic parameters without requiring external equipment or user intervention, maintaining reliable haptic effects throughout the device lifecycle.
3Measurement precision
If external sensors are used for calibration, then accurate haptic measurement is achieved, but device complexity and cost increase
Solution Approach 1:
The patent uses an intermediary approach by employing existing device components (microphone and speaker) as measurement tools for haptic calibration. Instead of adding dedicated haptic sensors, the system uses the audio subsystem as a mediator to indirectly measure actuator properties through back EMF detection, avoiding increased device complexity while maintaining measurement precision.
Solution Approach 2:
The patent applies universality by making existing device components serve multiple functions. The microphone and speaker, originally designed for audio processing, are also utilized for haptic actuator characterization and calibration. This multi-functional approach eliminates the need for separate haptic measurement hardware, reducing device complexity while maintaining calibration accuracy.
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 method ensures consistent haptic output performance by compensating for device variations and user preferences, improving user satisfaction and reducing product returns by allowing for in-field tuning and customization.
Implementation Method 1
detecting a back Electromotive Force (bEMF) signal from the actuator in the haptic system
Data Source
AI summary
Methods and systems for calibrating a haptic system in an electronic device are provided. The calibration of the haptic system may be performed in a facility prior to a shipment to a user. The calibration may also be performed by a user prior to or after his/her use of the haptic system in the electronic device over time. A method for performing a calibration process in an electronic device includes generating a drive signal from a haptic driver in a haptic system disposed in an electronic device, transmitting the drive signal to an actuator in the haptic system, detecting a back Electromotive Force (bEMF) signal from the actuator in the haptic system, analyzing an output waveform from the bEMF signal, and adjusting a scale of the drive signal generated from the haptic driver.