Head control device, storage device, and contact detection method

A storage device for reading and writing data from and to a storage medium, the storage device comprising:

• a heater that changes a position of a head for reading and writing data from and to the storage medium by thermal expansion;
• a heater control unit that increases a current supplied to the heater stepwise;
• an external-force sample retrieving unit that retrieves sampling values of signals indicating a magnitude of an external force acting on the head in a moving direction of a head support mechanism of the head, the moving direction being in a direction parallel to the storage medium;
• an external-force evaluating unit that calculates a representative value of the sampling values retrieved by the external-force sample retrieving unit to evaluate the magnitude of the external force every time the heater control unit increases the current;
• a contact detecting unit that detects contact between the head and the storage medium by comparing each evaluation result by the external-force evaluating unit with a predetermined threshold value;
• and
• a spacing control unit that controls the head to maintain a constant distance between the head and the storage medium based on the current at detection of the contact by the contact detecting unit,
• wherein the contact detecting unit varies the threshold value according to an absolute value of a yaw angle between a tangent to a target track on the storage medium and the head support mechanism.

A contact detection method for detecting contact between a head and a storage medium, the head being used for reading and writing data from and to the storage medium, a position of the head being changed by thermal expansion of a heater, the head and the heater being included in a storage device, the contact detection method comprising:

• increasing a current supplied to the heater stepwise;
• retrieving sampling values of signals each indicating a magnitude of an external force acting on the head in a moving direction of a head support mechanism of the head, the moving direction being in a direction parallel to the storage medium;
• calculating a representative value of the sampling values to evaluate the magnitude of the external force every time the current is increased;
• and
• detecting contact between the head and the storage medium by comparing each evaluation result of the magnitude of the external force with a predetermined threshold value,
• wherein the detecting includes varying the threshold value according to an absolute value of a yaw angle between a tangent to a target track on the storage medium and the head support mechanism.