Hard Disk Motor Duty Correction for Vibration Reduction
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Solution Overview
Problem
Existing motor driving methods for hard disk drives face challenges in reducing noise and vibration due to precision errors in sinusoidal voltage application, particularly when using Pulse Width Modulation (PWM), as errors occur between the duty instructed and the duty output by the driver.
Innovation Solution
A motor driving method employing a motor driving device with a drive transistor and a regenerative transistor, which executes duty instructing, duty correcting, PWM signal generating, and drive operations to improve the precision of sinusoidal voltage application, using a PWM corrector to adjust duty instruction values and generate corrected PWM signals, thereby reducing noise and vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If PWM modulation is used to drive the motor, then the motor can be controlled efficiently, but errors occur between the instructed duty and the actual duty output, deteriorating the precision of sinusoidal voltage application
Solution Approach 1:
The patent implements feedback by detecting the actual duty output from the driver and comparing it with the instructed duty. The difference (error) is then used to correct the instructed duty value, creating a closed-loop control system that compensates for PWM modulation errors and maintains high precision in sinusoidal voltage application.
Solution Approach 2:
The patent changes the parameter being controlled by introducing a correction value that adjusts the instructed duty. Instead of directly controlling the duty, the system controls the correction applied to the duty, allowing precise compensation for PWM errors while maintaining the efficiency benefits of PWM modulation.
2Object-affected harmful factors
If high precision sinusoidal voltage is applied to the motor, then torque ripple is reduced and noise decreases, but driver errors cause the actual voltage precision to deteriorate
Solution Approach 1:
The system uses feedback to detect the discrepancy between instructed and actual duty values, then applies correction based on this feedback. This ensures that despite driver errors, the actual voltage applied to the motor maintains high precision, thereby effectively reducing torque ripple, noise, and vibration.
Solution Approach 2:
The patent applies preliminary anti-action by pre-correcting the instructed duty value before it is applied to the motor. The correction value, calculated based on detected errors, is added in advance to compensate for expected driver inaccuracies, preventing precision deterioration before it occurs.
3Measurement precision
If duty correction is implemented to improve precision, then the system complexity increases due to additional correction operations
Solution Approach 1:
The patent makes the control system multi-functional by having the same control unit perform both the original PWM generation and the duty correction functions. The correction value calculation and application are integrated into the existing control architecture, allowing one component to serve multiple purposes without proportionally increasing system complexity.
Data Source
AI summary
The present invention is intended to reduce noise and vibration of a motor. A first duty correction circuit generates a first corrected duty instruction value which changes with an increment same as an increment of a duty instruction value and in which an offset value as a constant is reflected. A second duty correction circuit generates a second corrected duty instruction value which changes with an increment different from an increment of the duty instruction value. A selector outputs, as the corrected duty instruction value, either one of the first corrected duty instruction value and the second corrected duty instruction value in accordance with a magnitude relation between the duty instruction value and a duty reference value.