Actuator Control Device Resonance Frequency Correction
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Solution Overview
Problem
Haptic feedback systems using linear resonance actuators face challenges in maintaining optimal power efficiency due to variations in resonance frequency caused by manufacturing tolerances, mounting conditions, temperature, and aging, which affect vibration strength and residual vibration, especially in short driving times or small BEMF signals.
Innovation Solution
A control device and method that corrects the resonance frequency of linear resonance actuators by detecting the zero cross point of the BEMF signal and adjusting the clock frequency, using a PWM pulse generated from a combination of a reference clock frequency and driving signal waveform data, to ensure maximum vibration efficiency and minimize residual vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the actuator is driven at a fixed reference frequency, then the control system is simple, but the vibration efficiency decreases when resonance frequency varies due to manufacturing tolerances, temperature, or aging
Solution Approach 1:
The patent implements a feedback mechanism by detecting the zero cross point of the BEMF signal and using this information to automatically adjust the driving frequency. The controller measures the actual resonance frequency through zero cross point detection and feeds this information back to correct the driving frequency, ensuring the actuator operates at optimal resonance conditions despite variations in manufacturing tolerances, temperature, or aging.
Solution Approach 2:
The patent dynamically changes the driving frequency parameter based on detected resonance conditions. By adjusting the driving frequency to match the actual resonance frequency (detected through zero cross point timing), the system adapts to varying operating conditions and maintains maximum vibration efficiency without requiring complex manual calibration.
2Measurement precision
If the driving time is extended to allow accurate BEMF signal detection, then the resonance frequency can be accurately detected, but the response time increases which is unacceptable for short duration haptic feedback
Solution Approach 1:
The patent applies preliminary action by using the zero cross point detection method that can accurately determine resonance frequency from the very first driving cycle. Instead of requiring extended measurement periods, the system performs the essential detection action immediately by identifying the zero cross point of the BEMF signal, enabling fast frequency correction without sacrificing measurement accuracy.
Solution Approach 2:
The patent rushes through the detection process by using zero cross point detection which provides immediate frequency information. Rather than averaging multiple cycles or using complex spectral analysis that requires extended time, the system quickly identifies the resonance frequency from the timing of the zero cross point, enabling rapid adaptation for short duration haptic feedback applications.
3Device complexity
If the actuator is driven at frequencies away from resonance, then the system can operate with fixed frequency simplification, but the vibration force is weakened and power efficiency decreases
Solution Approach 1:
The actuator system performs self-service by automatically detecting its own resonance frequency through zero cross point detection of the BEMF signal and self-adjusting the driving frequency accordingly. This self-regulating mechanism ensures the actuator always operates at maximum vibration force without requiring external calibration or complex control systems, maintaining optimal power efficiency autonomously.
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 allows for real-time correction of resonance frequency, maintaining maximum vibration efficiency and reducing residual vibration, even in scenarios with short driving times or small BEMF signals, thereby enhancing the click feel of touch buttons and optimizing power usage.
Implementation Method 1
A linear Resonance Actuator (LRA) is used as a means of generating vibration in a haptic feedback system
Implementation Method 2
it detects the zero cross point of the back electro motive force (BEMF) signal
Data Source
AI summary
The present invention relates to a haptic feedback system and, particularly, to a device and a method for controlling an actuator for haptic feedback, the method comprising: a first step of controlling the output of an oscillator such that a clock necessary in the generation of a driving signal for driving an actuator is oscillated at a reference clock frequency; a second step of calculating the resonance frequency of the actuator from a cycle of a BEMF signal according to the driving of the actuator; and a third step of calculating a clock frequency for following the calculated resonance frequency of the actuator so as to newly change and set same to the reference clock frequency, thereby controlling the output of the oscillator.