Dual Actuator Emergency Power Off Retraction
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Solution Overview
Problem
In data storage devices with dual actuators, managing emergency power off (EPO) events is complex due to the need to retract and park multiple actuators and brake the spindle motor while ensuring data egress and preventing head damage.
Innovation Solution
A data storage device with dual actuators is designed to retract and park both lead and support actuators using an internal supply voltage generated from the back electromotive force (BEMF) voltage of the spindle motor, and then brake the spindle motor, ensuring that both actuators are fully retracted and parked before braking the spindle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple actuators are used to increase HDD performance, then productivity is improved, but device complexity increases
Solution Approach 1:
The patent divides the actuator system into distinct lead and support actuators, each with dedicated control logic. During EPO events, the lead actuator is retracted first, followed by the support actuator, creating a segmented approach to handling multiple actuators that simplifies the overall control complexity while maintaining the productivity benefits of having multiple actuators.
2Object-affected harmful factors
If spindle motor is braked quickly to minimize head wear, then head wear is reduced, but risk of head damage increases if actuators are not fully retracted
Solution Approach 1:
The patent implements preliminary action by ensuring both the lead and support actuators are fully retracted and parked before the spindle motor brake is activated. This sequence prevents the harmful effect of head wear during normal operation while eliminating the risk of head damage during EPO events, as the heads are already in a safe position before braking begins.
3Reliability
If internal supply voltage from BEMF is used to power actuator retraction during EPO, then reliability is improved by preventing head damage, but loss of energy occurs as BEMF voltage must be managed carefully
Solution Approach 1:
The patent applies self-service by utilizing the back electromotive force (BEMF) voltage generated by the spinning spindle motor itself to power the actuator retraction process during EPO events. This eliminates the need for external power sources and ensures reliable head parking by using the system's own energy resources, converting what would otherwise be wasted energy into a useful function.
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 solution ensures safe and efficient handling of EPO events in dual actuator systems, preventing head damage and ensuring reliable data egress by managing the internal supply voltage effectively.
Implementation Method 1
the momentum of the disk spinning generates a back electromotive force (BEMF) voltage across the windings of the spindle motor that may be used to generate an internal supply voltage
Data Source
AI summary
A data storage device comprises a lead actuator that actuates a first read-write head over a first disk and a support actuator that actuates a second read-write head over a second disk. A spindle motor rotates the first and second disks. In response to an emergency power off (EPO) event, a processing device retracts and parks the actuators using an internal supply voltage generated from a back electromotive force (BEMF) voltage of the spindle motor, and brakes the spindle motor. The spindle motor is not braked until both the lead and support actuators have been retracted and parked.