Spindle Motor Commutation via Servo Sector Phase Alignment
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Solution Overview
Problem
Existing data storage devices face challenges in accurately controlling the spindle motor's rotation phase, leading to issues such as acoustic noise, torque/speed jitter, and disk vibration due to the reliance on back electromotive force (BEMF) voltage measurements, which can lose synchronization with timing data.
Innovation Solution
Implementing a control circuitry that measures the spindle motor's rotation phase using servo sectors and generates a commutation sequence, allowing for phase error adjustment and compensation to stabilize the rotation, thereby reducing noise and vibration by switching between BEMF and timing data-based commutation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If BEMF voltage measurement is used to control commutation, then the system is simpler to implement, but synchronization is lost leading to acoustic noise and vibration
Solution Approach 1:
The patent implements a feedback mechanism where the rotation phase is continuously measured using servo sectors and this measurement is fed back to adjust the commutation sequence timing. The system compares the measured rotation phase with the commutation sequence phase and generates a phase error signal that is used to adaptively adjust the oscillator frequency, ensuring continuous synchronization and eliminating acoustic noise and vibration.
Solution Approach 2:
The patent replaces the traditional BEMF voltage measurement method with a servo sector-based rotation phase measurement system. This substitution uses timing data from servo sectors read by the head to determine rotation phase, providing more reliable and accurate synchronization information compared to BEMF measurements, thereby maintaining synchronization without losing accuracy.
2Measurement precision
If rotation phase measurement accuracy is improved, then synchronization is maintained, but the system becomes more complex
Solution Approach 1:
The patent utilizes the existing servo sectors that are already being read by the head for their primary purpose of head positioning to also serve the function of rotation phase measurement. The servo sectors contain timing information that is already present in the disk structure, and the system extracts rotation phase information from these same sectors without requiring additional dedicated measurement infrastructure, thus achieving high measurement precision without proportionally increasing system complexity.
3Object-affected harmful factors
If commutation sequence is adjusted for phase alignment, then vibration is reduced, but control system complexity increases
Solution Approach 1:
The patent implements a dynamic commutation control system where the commutation sequence is continuously adjusted based on real-time phase error measurements. The oscillator frequency is adaptively modified according to the phase difference between the measured rotation phase and the commutation sequence phase, allowing the system to dynamically maintain optimal alignment and minimize vibration and acoustic noise under varying operating conditions.
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 enhances spindle motor control accuracy, reduces acoustic noise and vibration, and maintains stable disk operation by adaptively adjusting the commutation sequence based on phase errors and mechanical parameters.
Implementation Method 1
A commutation controller applies a driving signal to the windings of the spindle motor using a particular commutation sequence in order to generate a rotating magnetic field that causes the spindle motor to rotate
Implementation Method 2
measuring a zero-crossing frequency of a back electromotive force (BEMF) voltage generated by the windings of the spindle motor
Implementation Method 3
The disk is typically rotated by a spindle motor at a high speed so that an air bearing forms between the head and the disk surface
Data Source
AI summary
A data storage device is disclosed comprising a head actuated over a disk, and a spindle motor configured to rotate the disk, wherein the spindle motor comprises a plurality of windings. A commutation controller is configured to commutate the windings based on a commutation sequence driven by an oscillator. A rotation phase of the spindle motor is measured, and a phase error is generated based on the measured rotation phase of the spindle motor and a phase of the commutation sequence, wherein a frequency of the oscillator is adjusted based on the phase error.