Servo Spiral Writing via Iterative Learning Control
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Solution Overview
Problem
The existing methods for writing servo spirals on hard disk drives require external equipment, making them time-consuming and expensive in high-volume manufacturing, and there is a need for a method to generate servo spirals without external equipment.
Innovation Solution
An iterative learning control scheme is applied for open-loop control of the magnetic head actuator to ensure uniform and constant spiral slope, combined with ramp contact detection based on actuator current profiles to achieve full utilization of the actuator stroke, allowing for in-drive writing of servo spirals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If external equipment (external media writer or servo writing machine) is used to write servo spirals on the disk surface, then the servo spirals can be written with precise and constant slope, but the manufacturing process becomes time-consuming and expensive
Solution Approach 1:
The patent applies self-service by enabling the hard disk drive to write its own servo spirals using its internal actuator and control systems. The iterative learning control scheme allows the drive to automatically adjust and optimize the writing process without external equipment, making the system self-sufficient for servo pattern generation.
Solution Approach 2:
The patent extracts the servo spiral writing function from external equipment and transfers it to the internal components of the hard disk drive. By removing the dependency on external media writers or servo writing machines, the process is integrated directly into the drive assembly line, eliminating the need for separate external processing steps.
2Measurement precision
If external equipment is used for writing servo spirals, then accurate positioning can be achieved, but the setup and operation of external equipment adds complexity to the manufacturing process
Solution Approach 1:
The patent merges the servo spiral writing function with the hard disk drive's internal actuator system. By combining the positioning control, writing head, and actuator into a single integrated system, the patent eliminates the need for separate external positioning equipment and simplifies the overall manufacturing process while maintaining positioning accuracy.
Solution Approach 2:
The patent makes the hard disk drive actuator multi-functional by using it for both data writing operations and servo spiral generation. This universal approach allows the same internal components to perform multiple functions, eliminating the need for dedicated external equipment and reducing manufacturing process complexity.
3Stability of the object's composition
If iterative learning control is applied for open-loop control of the magnetic head actuator, then uniform and constant spiral slope can be ensured, but the control system becomes more complex
Solution Approach 1:
The patent applies feedback through an iterative learning control scheme that uses measured velocity profiles from previous iterations to adjust and optimize the actuator control parameters. The system measures the actual velocity profile during each writing iteration and uses this feedback information to refine the control strategy, ensuring uniform spiral slope while maintaining manageable control system complexity.
Solution Approach 2:
The patent implements dynamics by using an iterative learning control approach that continuously adapts and optimizes the velocity profile based on measured performance. The control parameters are dynamically adjusted across multiple iterations to achieve the desired uniform spiral slope, transforming a static control problem into a dynamic optimization process.
Data Source
AI summary
A reference spiral is written on a recording surface of a magnetic storage disk that is free of position or timing information. The reference spirals are written on the recording surface with a substantially uniform slope by using open loop control of the position of a read/write head in conjunction with an iterative learning control scheme. A voltage profile applied to a voice coil motor is adapted over multiple iterations of moving the read/write head across the recording surface to closely approximate a target voltage profile, and the reference spiral is written using the adapted voltage profile. In addition, ramp contact detection based on actuator current profile may be employed to achieve full utilization of available actuator stroke.