Digital Filter for Voice Coil Motor Drive Circuit
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Solution Overview
Problem
Existing motor drive circuits for voice coil motors in actuators, used in devices like hard disc drives and portable terminals, face challenges in achieving rapid stabilization of moving parts due to varying natural frequency periods, leading to longer convergence times and unsatisfied response speeds.
Innovation Solution
A motor drive circuit incorporating a digital filter to attenuate the amplitude in the frequency band including the resonance frequency of the actuator, converting the filtered signal into an analog current control signal to efficiently supply drive current to the voice coil motor, utilizing digital-analog conversion and a drive circuit with an operational amplifier and NMOS transistor to control the drive current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the drive current is ramped up over a longer time period to match lower natural frequency, then vibration is reduced, but convergence time increases and response speed decreases
Solution Approach 1:
The patent extracts and removes the harmful resonance frequency components from the drive signal using a digital filter. By identifying the natural frequency of the actuator and applying a notch filter at that frequency, the resonance vibrations are eliminated from the drive current, allowing rapid positioning without the need for prolonged ramp-up periods.
Solution Approach 2:
The patent dynamically changes the parameters of the drive signal by adjusting the frequency components through digital filtering. The system measures the natural frequency of the actuator and modifies the drive signal's frequency spectrum by attenuating the resonant frequency components, enabling fast convergence without excessive vibration.
2Stability of the object's composition
If the ramp time is extended to accommodate varying natural frequencies, then positioning stability is improved, but response speed becomes insufficient
Solution Approach 1:
The patent employs feedback by measuring the natural frequency of the actuator and using this information to adjust the drive signal. The system monitors the actuator's resonant characteristics and dynamically modifies the drive current's frequency spectrum to avoid excitation of resonance, achieving both rapid response and stable positioning.
Solution Approach 2:
The system changes the frequency parameters of the drive signal based on measured actuator characteristics. By applying digital filtering that attenuates specific frequency components corresponding to the actuator's natural frequency, the system achieves stable positioning with fast response time adaptable to different actuator configurations.
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 solution significantly shortens the convergence time of the actuator's vibration stabilization, improving response speed by selectively attenuating resonance and harmonic frequency components, thereby enhancing the motor drive circuit's performance across varying actuator configurations.
Implementation Method 1
a digital filter configured to attenuate amplitude in a frequency band including a resonance frequency of an actuator
Implementation Method 2
a voice coil motor configured to drive the actuator... produces thrust by passing an electric current through a coil in a magnetic field of a permanent magnet
Data Source
AI summary
A motor drive circuit includes: a digital filter configured to attenuate amplitude in a frequency band including a resonance frequency of an actuator in a target current signal, the target current signal being a digital signal indicative of a target value of a drive current, the drive current being supplied to a voice coil motor configured to drive the actuator; a digital-analog converter configured to convert an output signal of the digital filter into an analog signal, and output the converted analog signal as a current control signal; and a drive circuit configured to supply the drive current to the voice coil motor according to the current control signal.