Quiet Retraction System for Disk Drive Arm Acoustic Noise Reduction
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Solution Overview
Problem
Optical disk drives face challenges in reducing acoustic noise during the parking of the arm, particularly when the drive current exceeds a singing threshold, leading to noticeable noise, which is not effectively addressed by existing technologies.
Innovation Solution
A quiet retraction system (QRS) that assesses the magnitude of the drive current and adjusts it to a lower frequency, maintaining a constant back electromotive force (Bemf) to reduce acoustic noise, using a voice coil motor and a series of gain stages, converters, and timers to control the arm's movement and estimate Bemf, thereby minimizing noise while parking the arm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the drive current is increased to improve arm movement speed and positioning precision, then the arm can be moved more quickly and accurately to the parked position, but acoustic noise exceeds the singing threshold and becomes noticeable
Solution Approach 1:
The patent applies periodic action by using pulsed drive currents instead of continuous current during arm retraction. The system delivers current in controlled pulses that move the arm efficiently while allowing silent intervals that prevent acoustic resonance, thereby reducing noticeable noise while maintaining retraction speed
Solution Approach 2:
The system dynamically adjusts the drive current characteristics during retraction. By monitoring arm position and velocity, the controller modifies current pulse width and frequency in real-time, optimizing the balance between movement speed and noise generation throughout the retraction process
2Object-affected harmful factors
If the drive current is reduced below the singing threshold to decrease acoustic noise, then noise is reduced, but the arm movement precision and speed are compromised
Solution Approach 1:
The pulsed current delivery allows the system to operate below the continuous singing threshold while still achieving effective arm movement. The periodic pulses provide sufficient force for precise positioning without sustaining the continuous vibration that causes noticeable acoustic noise
Solution Approach 2:
The system uses feedback from position sensors and current monitors to adjust pulse parameters dynamically. This ensures that even at reduced current levels, the arm achieves accurate positioning by optimizing pulse timing and duration based on real-time arm state
3Object-affected harmful factors
If the drive current is adjusted frequently to maintain constant Bemf during quiet retract, then acoustic noise is reduced, but the system complexity increases due to additional control mechanisms
Solution Approach 1:
The system employs feedback control by monitoring Bemf voltage and adjusting drive current pulses accordingly. This closed-loop approach maintains constant Bemf during quiet retract operations, ensuring noise reduction is achieved through systematic current management rather than trial-and-error adjustments
Solution Approach 2:
The patent replaces complex mechanical noise damping mechanisms with electrical control solutions. By using electronic pulse width modulation and Bemf-based feedback control, the system achieves quiet operation through software-controlled current management rather than additional mechanical components
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 QRS significantly reduces acoustic noise by deriving the drive current differently and maintaining a constant Bemf, ensuring a quiet retract operation without compromising the arm's parking precision, making the system more user-friendly by allowing programmable noise thresholds.
Implementation Method 1
a voice coil motor and a series of gain stages, converters, and timers to control the arm's movement
Implementation Method 2
maintaining a constant back electromotive force (Bemf) to reduce acoustic noise
Data Source
AI summary
A quiet retraction method for regulating constant velocity while parking an arm within a disk drive is described. The method comprises the steps of: driving a motor for the arm using a first drive current for a first period; floating the motor; sampling a back electromotive force (bemf) for a first sampled voltage, while floating the motor; driving the motor with a second drive current during a second period in response to sampling the bemf; determining whether the second drive current exceeds a current limit; estimating the bemf using the first sampled voltage when the second drive current exceeds the current limit; driving the motor with a third current during a third period in response to estimating the bemf; wherein driving the motor with the first, second, and third currents quietly parks the arm, while regulating the constant velocity.