RRO Cancellation Control Voltage for Optical Disc Positioning
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Solution Overview
Problem
Conventional optical disc drivers face challenges in effectively canceling repeatable run-out (RRO) errors due to asynchronous tracking and spindle control, especially with limited Hall sensors, leading to poor RRO cancellation and manufacturing cost constraints.
Innovation Solution
A method and apparatus that estimate the rotation period of the recording medium, determine an update interval for the RRO cancellation control voltage, and apply it to control positioning, using a sinusoidal control signal with determined phase and magnitude to synchronize with spindle rotation, allowing for flexible and precise RRO cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional RRO cancellation uses FG signal from Hall effect sensors to synchronize the cancellation algorithm to the spindle revolution, then the RRO cancellation is triggered at each edge of the FG signal, but the number of Hall sensors in the driver system predetermines the fixed number of RRO cancellation control per spindle rotation, resulting in poor RRO cancellation when only one Hall sensor is provided
Solution Approach 1:
The patent implements dynamic adjustment of the RRO cancellation update interval based on the estimated rotation period of the recording medium. The controller dynamically calculates the appropriate update interval to achieve a desired number of updates per rotation, allowing the system to adapt to varying spindle speeds and maintain precise RRO cancellation without being constrained by a fixed number of Hall sensor pulses. This dynamic approach replaces the static, sensor-count-dependent conventional method.
Solution Approach 2:
The patent changes the control parameter from a fixed update rate tied to FG signal edges to a variable update interval calculated based on the estimated rotation period. By adjusting the update interval parameter dynamically, the system can achieve the desired number of RRO cancellation updates per rotation regardless of the number of Hall sensors available, thereby improving cancellation precision without increasing device complexity.
2Productivity
If the tracking servo operates at a fixed rate whereas the spindle servo operates at variable rotation speed to maintain constant linear velocity, then the tracking servo and spindle control are asynchronous, but conventional error cancellation techniques assume the tracking actuator is synchronous to the spindle motor
Solution Approach 1:
The patent implements a feedback mechanism where the controller estimates the rotation period of the recording medium based on spindle speed measurements and uses this information to dynamically adjust the RRO cancellation update interval. This feedback loop ensures that the cancellation updates remain synchronized with the spindle rotation even as the spindle speed varies to maintain constant linear velocity, resolving the asynchrony issue between the fixed-rate tracking servo and variable-speed spindle servo.
Solution Approach 2:
The system dynamically adjusts the RRO cancellation update timing based on the estimated rotation period, which varies with spindle speed. This dynamic synchronization allows the tracking servo to maintain accurate positioning despite operating at a fixed rate while the spindle servo operates at variable speeds to maintain constant linear velocity, effectively decoupling the two operations while preserving tracking accuracy.
3Adaptability or versatility
If the RRO cancellation is triggered at each edge of the FG signal, then the number of FG pulses predetermines the fixed number of RRO cancellation control per spindle rotation, but this limits flexibility and increases manufacturing cost when only one Hall sensor is provided
Solution Approach 1:
The patent replaces the static, pulse-count-dependent control update mechanism with a dynamic update interval calculation based on the estimated rotation period. This allows the system to achieve a desired number of RRO cancellation updates per rotation regardless of the number of Hall sensors available, providing control flexibility without requiring additional sensors or increasing manufacturing complexity.
Solution Approach 2:
The patent segments the RRO cancellation control into multiple updates per rotation by dynamically determining the update interval. Instead of being constrained to a fixed number of updates equal to the number of Hall sensor pulses, the system can perform multiple smaller updates throughout each rotation, improving cancellation precision while using the same single Hall sensor, thereby reducing manufacturing cost while maintaining adaptability.
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 significantly reduces RRO errors, maintaining data integrity and improving reading/writing performance in optical disc drivers, even at varying spindle speeds, by decoupling control updates from FG pulses, enhancing cancellation precision and reducing manufacturing costs.
Implementation Method 1
A method and apparatus cancel repeatable run-out (RRO) errors in positioning on a recording medium using a RRO cancellation control voltage
Data Source
AI summary
A method and apparatus cancel repeatable run-out (RRO) errors in positioning on a recording medium using a RRO cancellation control voltage. The RRO cancellation includes (a) estimating a rotation period of the recording medium, (b) determining an update interval for the RRO cancellation control voltage based on the estimated rotation period and a desired number of updates to be performed per rotation, (c) updating a value of the RRO cancellation control voltage if a time period passed from a last update is greater than the update interval, and (d) applying the updated RRO cancellation voltage to control the positioning. A phase and a magnitude of the RRO cancellation control voltage may be determined for a RRO frequency range.