Predictive Oversampling for Servo Control Phase Delay
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Solution Overview
Problem
The existing servo control systems in data storage devices face performance degradation due to phase delay induced by serial interfaces, which affects the accuracy and efficiency of head positioning in disk drives.
Innovation Solution
A predictive oversampler is implemented in the driver circuit to generate predictive oversampled control values based on the slope of digital control values received from the servo controller, mitigating the phase delay by interpolating control signals between sample intervals, thereby improving servoing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If digital control values are transmitted through a serial interface, then device complexity is reduced, but phase delay occurs in the feedback loop
Solution Approach 1:
The predictive oversampler performs preliminary action by generating predicted control values in advance of when they are needed. It uses the slope calculated from previously received digital control values to predict future control values, thereby compensating for the phase delay introduced by the serial interface transmission before the actual control action is required.
2Speed
If control values are sampled at lower rate, then processing speed is reduced, but sampling frequency is insufficient for accurate servo control
Solution Approach 1:
The predictive oversampler creates copies of the control signal at higher resolution by generating multiple predicted control values between each pair of received digital control values. It uses the calculated slope to generate intermediate control values that replicate the intended control waveform at the higher DAC sampling rate, thereby achieving accurate servo control without requiring the servo controller to operate at the higher frequency.
Data Source
AI summary
A data storage device is disclosed comprising a disk comprising servo data, and an actuator configured to actuate a head over the disk. A servo controller is configured to generate digital control values at a first sample rate based on the servo data and transmit the digital control values over a serial interface to a driver circuit. The driver circuit is configured to generate predictive oversampled control values at a second sample rate higher than the first sample rate based on at least two of the digital control values received from the servo controller, apply the predictive oversampled control values to a digital-to-analog converter (DAC) to generate an analog control signal, and apply the analog control signal to the actuator.