4.5 Self-calibration

4.5 Self-calibration

The disk drive occasionally performs self-calibration in order to sense and calibrate mechanical external forces on the actuator, and VCM torque. This enables precise seek and read/write operations.

4.5.1 Self-calibration contents

(1) Sensing and compensating for external forces

The actuator suffers from torque due to the FPC forces and winds accompanying disk revolution. The torque varies with the disk drive and the cylinder where the head is positioned. To execute stable fast seek operations, external forces are occasionally sensed.

The firmware of the drive measures and stores the force (value of the actuator motor drive current) that balances the torque for stopping head stably. This includes the current offset in the power amplifier circuit and DAC system.

The forces are compensated by adding the measured value to the specified current value to the power amplifier. This makes the stable servo control.

To compensate torque varying by the cylinder, the disk is divided into 13 areas from the innermost to the outermost circumference and the compensating value is measured at the measuring cylinder on each area at factory calibration. The measured values are stored in the SA cylinder. In the self-calibration, the compensating value is updated using the value in the SA cylinder.

(2) Compensating open loop gain

Torque constant value of the VCM has dispersion for each drive, and varies depending on the cylinder that the head is positioned. To realize the high speed seek operation, the value that compensates torque constant value change and loop gain change of the whole servo system due to temperature change is measured and stored.

For sensing, the firmware mixes the disturbance signal to the position signal at the state that the head is positioned to any cylinder. The firmware calculates the loop gain from the position signal and stores the compensation value against to the target gain as ratio.

For compensating, the direction current value to the power amplifier is multiplied by the compensation value. By this compensation, loop gain becomes constant value and the stable servo control is realized.

To compensate torque constant value change depending on cylinder, whole cylinders from most inner to most outer cylinder are divided into 13 partitions at calibration in the factory, and the compensation data is measured for representative cylinder of each partition. This measured value is stored in the SA area. The compensation value at self-calibration is calculated using the value in the SA area.

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Fujitsu MHW2040AC, MHW2060AC manual Self-calibration contents
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MHW2060AC, MHW2040AC specifications

The Fujitsu MHW2040AC and MHW2060AC are notable hard disk drives (HDDs) that have been widely used in various computing applications, especially in laptops and compact devices. These models are part of Fujitsu's commitment to providing reliable storage solutions that meet the demands of modern computing.

The MHW2040AC offers a storage capacity of 40 GB, while the MHW2060AC provides a slightly larger capacity at 60 GB. This range of storage makes both models suitable for users looking for dependable space for documents, multimedia files, and software applications. Both drives utilize a 2.5-inch form factor, ideal for mobile computing, as they are lightweight and designed to fit into space-constrained environments.

In terms of performance, both drives operate at a spindle speed of 5400 RPM. This speed strikes a balance between power consumption and performance, making these drives an efficient choice for everyday tasks, such as web browsing and office applications. The drives are equipped with an interface of Ultra ATA/133, which enables faster data transfer rates compared to older models, thereby enhancing overall system responsiveness.

The MHW2040AC and MHW2060AC also incorporate several advanced technologies to bolster their performance and reliability. One such feature is the use of a fluid dynamic bearing (FDB) for the spindle motor, which minimizes noise and vibration, thus improving the overall user experience. Additionally, both drives come with error correction technology that helps maintain data integrity by detecting and correcting errors during read and write operations.

Moreover, these HDDs feature a shock sensor that can detect sudden movements, allowing the drive to park its heads to prevent data loss and hardware damage. This is particularly beneficial in mobile environments where the risks of impact are higher.

Both the MHW2040AC and MHW2060AC are designed with energy-saving features, making them an environmentally responsible choice for energy-conscious consumers. Their low power consumption not only contributes to a reduced carbon footprint but also extends battery life for portable devices.

In summary, the Fujitsu MHW2040AC and MHW2060AC are reliable, efficient, and user-friendly hard disk drives that combine moderate capacities with advanced features designed to enhance performance, ensure data integrity, and extend device longevity. These drives are well-suited for a range of applications, making them a solid choice for users seeking dependable storage solutions.
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