4536809

This patent describes an adaptive misposition correcting system for magnetic disk storage devices. Its primary goal is to enhance data track density and positioning accuracy by mitigating errors caused by factors like spindle runout and other slowly varying disturbances.

Key aspects of the invention include:

1. Dynamic Error Measurement: The system continuously measures misposition errors relative to the data track centerline using an anti-aliasing analog filter.
2. Digital Processing: The measured analog signal is digitized, and specific harmonics of the resulting cyclic error signal are removed.
3. Matched Digital Filtering: The processed error signal is transformed by a "matched digital filter." This filter's transfer function has independently adjustable parameters (DC gain, fundamental-frequency gain, and phase lead), allowing the generated correction signal to precisely match the servo system's electrical and mechanical response.
4. Iterative Refinement: The correction signal is iteratively refined by re-applying it to the servo controller during subsequent misposition error measurements, leading to continuous improvement in accuracy.
5. Multi-Transducer Support: The system stores separate misposition correction signals for each transducer (read/write head) on the disk, ensuring optimal correction regardless of which head is active.
6. Bias Force Correction: It also generates a dedicated bias force correction signal to compensate for non-linear position errors arising from variations in forces acting on the transducer carriage across its radial displacement.

In essence, the invention provides a self-calibrating and adaptive method to precisely maintain the position of data heads over disk tracks, overcoming inherent mechanical and electrical imperfections, thereby allowing for significantly higher data storage densities.