Frequency Control Apparatus for Vibration Motor Noise Reduction
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Solution Overview
Problem
The Pulse Density Modulation (PDM) system used in frequency control for vibration motors results in frequency scattering, leading to uneven speed profiles and audible noise due to modulated frequencies within specific bands, which existing technologies fail to adequately address.
Innovation Solution
A frequency control apparatus that includes a signal generator, an estimator, and a frequency shift unit to estimate and shift frequencies, preventing unwanted frequency components from entering specific bands by adjusting the target frequency and associated signal frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PDM control is used to achieve high frequency resolution, then frequency resolution is improved, but frequency scattering occurs causing uneven speed profiles and audible noise
Solution Approach 1:
The patent implements a feedback mechanism where the actual output frequency is measured and compared with the target frequency. Based on the frequency error detected, the control system adjusts the PDM modulation parameters in real-time to compensate for frequency scattering and eliminate audible noise components.
Solution Approach 2:
The patent dynamically changes PDM control parameters including modulation depth, switching frequency, and pulse width based on the detected frequency error. By varying these parameters adaptively, the system maintains high frequency resolution while suppressing frequency scattering and audible noise.
2Object-generated harmful factors
If random noises are added to disperse frequency spectrum intensity, then peaky frequency spectrum in audible band is reduced, but frequency scattering increases at predetermined time intervals
Solution Approach 1:
The system continuously monitors the output frequency and uses feedback control to counteract the frequency scattering introduced by random noise addition. The feedback loop adjusts the modulation frequency in real-time to maintain stable average frequency while dispersing peaky spectrum components.
Solution Approach 2:
Instead of adding full-strength random noise, the patent applies a controlled amount of random noise that is sufficient to disperse peaky frequency components but limited enough that feedback control can compensate for the resulting frequency variations, achieving partial dispersion without excessive instability.
3Measurement precision
If frequency is changed for each predetermined time period in PDM system, then high frequency resolution is obtained, but output frequency scatters when observed at predetermined time intervals
Solution Approach 1:
The patent employs feedback control that measures the actual frequency output over predetermined time periods and adjusts the modulation parameters to compensate for scattering. This ensures that while frequency changes occur for high resolution, the average frequency remains consistent and reliable.
Solution Approach 2:
The system performs preliminary frequency planning where the target frequency for each time period is pre-calculated to anticipate and compensate for expected scattering. By planning frequency transitions in advance based on statistical characteristics of PDM scattering, the system maintains better frequency consistency.
Data Source
AI summary
A frequency control apparatus includes a signal generator configured to generate an output signal as a digital signal having a target frequency that has been set, using a plurality of signals having frequencies that are different from the target frequency and one another, an estimator configured to estimate a mixed frequency that is a frequency of a signal component mixed in the output signal and different from the target frequency and each of frequencies of the plurality of signals, and a frequency shift unit configured to shift at least one of the target frequency and the frequencies of the plurality of signals in accordance with an estimation result of the mixed frequency.