LRA Driving Circuit Using Back-EMF for Resonant Frequency Tracking
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Solution Overview
Problem
Conventional methods for determining the resonant frequency of linear resonant actuators (LRAs) are prone to errors due to low clock frequencies or noisy feedback signals, leading to incorrect zero-crossing points and inefficient operation.
Innovation Solution
A driving circuit that utilizes a voltage sensor to detect back electromotive force (EMF) of the LRA, a signal controller to adjust the operation period based on the EMF, and a signal generator to generate a driving signal corresponding to the adjusted period, ensuring the LRA operates at its resonant frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the clock frequency is reduced, then the power consumption decreases, but the timing calculation error increases leading to wrong resonant frequency determination
Solution Approach 1:
The patent replaces the conventional zero-crossing detection method (which relies on high clock frequency timing) with a back-EMF based detection method. The back-EMF signal naturally indicates the resonant frequency through its amplitude characteristics, eliminating the need for high-frequency timing measurements and reducing power consumption while maintaining measurement precision.
Solution Approach 2:
The patent changes the detection parameter from timing-based (requiring high clock frequency) to voltage-based (back-EMF amplitude). By monitoring the back-EMF voltage signal characteristics instead of timing zero-crossings, the system achieves accurate resonant frequency detection at lower clock frequencies, thus reducing power consumption without sacrificing measurement accuracy.
2Measurement precision
If the clock frequency is increased, then the timing calculation precision improves, but the power consumption increases
Solution Approach 1:
The patent substitutes the high-frequency timing-based zero-crossing detection with a back-EMF based detection system. The back-EMF signal's amplitude directly correlates with resonant frequency, allowing accurate detection without requiring high clock frequencies, thus achieving measurement precision with lower power consumption.
Solution Approach 2:
The patent transitions from timing parameter measurement (which requires high clock frequency for precision) to voltage amplitude measurement (back-EMF). This parameter change enables accurate resonant frequency detection at lower operating frequencies, reducing power consumption while maintaining or improving measurement precision.
3Measurement precision
If the feedback signal quality is improved, then the zero-crossing detection accuracy improves, but the device complexity increases
Solution Approach 1:
The patent replaces the complex zero-crossing detection system (requiring high-quality feedback signals and precise timing) with a back-EMF based detection system. The back-EMF signal provides direct information about resonant frequency through its amplitude characteristics, simplifying the detection mechanism and reducing device complexity while maintaining or improving detection accuracy.
Solution Approach 2:
The patent changes the detection approach from analyzing the timing of zero-crossing points (which requires high signal quality and complex processing) to analyzing the amplitude characteristics of the back-EMF signal. This parameter change simplifies the signal processing requirements and reduces device complexity while achieving accurate resonant frequency detection.
4Measurement precision
If the noise level in feedback signal is reduced, then the zero-crossing point determination accuracy improves, but the device complexity increases
Solution Approach 1:
The patent substitutes the noisy zero-crossing detection method with back-EMF based detection. The back-EMF signal inherently provides clear resonant frequency information through its amplitude characteristics, which are less susceptible to noise, thereby improving determination accuracy without requiring complex filtering or noise reduction circuits.
Solution Approach 2:
The patent transitions from detecting zero-crossing points (which are highly sensitive to noise and require complex filtering) to measuring back-EMF amplitude characteristics. This parameter change makes the detection process more robust to noise, improving accuracy while reducing the complexity of signal conditioning and filtering circuits.
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 driving circuit accurately adjusts the operation frequency to match the resonant frequency of the LRA, enhancing efficiency and reducing errors associated with conventional methods.
Implementation Method 1
The voltage sensor, coupled to the resonant device, is configured to detect a back electromotive force (EMF) of the resonant device
Data Source
AI summary
A driving circuit for driving a resonant device includes a voltage sensor, a signal controller, a signal generator and a driver. The voltage sensor, coupled to the resonant device, is configured to detect a back electromotive force (EMF) of the resonant device. The signal controller, coupled to the voltage sensor, is configured to control the length of an operation period of the driving circuit according to the back EMF. The signal generator, coupled to the signal controller, is configured to generate a driving signal corresponding to the length of the operation period. The driver, coupled to the signal generator, is configured to output the driving signal to the resonant device.