Method and apparatus for compensating for torque change in seek servo

A method of compensating for a torque change in a seek servo of a disc drive, the method comprising:

• performing predetermined test seeks with respect to test seek positions into which a disc is divided and seek directions;
• obtaining torque compensation constants from the test seeks;
• storing the torque compensation constants in a torque compensation constant table;
• and
• compensating for a gain of a seek control loop at a position where a seek is performed, taking into account a seek direction in a seek mode, using the torque compensation constants stored in the torque compensation constant table,
• wherein the torque compensation constants are obtained by calculating a ratio of an actual seek driving current trajectory to a design acceleration trajectory for each test seek position.

An apparatus to compensate for a torque change in a seek servo of a disc drive, the apparatus comprising:

• a seek servo control circuit generating a seek driving current to move a transducer to a target track through a predetermined seek control loop using a predetermined design acceleration trajectory, a predetermined design velocity trajectory, and a predetermined design position trajectory;
• a memory device storing a torque compensation constant table;
• a controller
• performing test seeks with respect to test seek positions into which a disc is divided under predetermined conditions,
• obtaining torque compensation constants from the test seeks,
• setting and storing the torque compensation constant table in the memory device, and
• determining a torque compensation constant according to a position on the disc, in a seek mode, using the torque compensation constant table;
• and
• a torque constant compensator compensating for a gain of the seek control loop using the torque compensation constant determined by the controller,
• wherein the torque compensation constants are obtained by calculating a ratio of an actual seek driving current trajectory to a design acceleration trajectory for each test seek position.

An apparatus to compensate for a torque change in a seek servo of a disc drive, the apparatus comprising:

• a seek servo control circuit generating a seek driving current to move a transducer to a target track through a predetermined seek control loop using a predetermined design acceleration trajectory, a predetermined design velocity trajectory, and a predetermined design position trajectory;
• a memory device storing a torque compensation constant table;
• a controller
• performing test seeks with respect to test seek positions into which a disc is divided, and seek directions,
• obtaining torque compensation constants from the test seeks,
• setting and storing the torque compensation constant table in the memory device, and
• determining a torque compensation constant according to a position on the disc, taking into account a seek direction, in a seek mode, using the torque compensation constant table;
• and
• a torque constant compensator compensating for a gain of the seek control loop using the torque compensation constant determined by the controller,
• wherein the torque compensation constants are obtained by calculating a ratio of an actual seek driving current trajectory to a design acceleration trajectory for each test seek position.

A method of generating torque compensation constants for a disc drive, the method comprising:

• performing predetermined test seeks, with respect to test seek positions into which a disc is divided;
• and
• obtaining torque compensation constants from the test seeks by calculating a ratio of an actual seek driving current trajectory to a design acceleration trajectory, with respect to the test seek positions
• wherein the torque compensation constants are obtained by calculating a ratio of an actual seek driving current trajectory to a design acceleration trajectory for each test seek position.

A computer program product including a computer readable medium having computer program codes for executing a procedure, comprising:

• a first set of instructions to
• perform predetermined test seeks with respect to test seek positions into which a disc is divided,
• obtain torque compensation constants from the test seeks, and
• store the torque compensation constants in a torque compensation constant table;
• and
• a second set of instructions to compensate for a gain of a seek control loop at a position where a seek is performed in a seek mode, using the torque compensation constants stored in the torque compensation constant table,
• wherein the torque compensation constants are obtained by calculating a ratio of an actual seek driving current trajectory to a design acceleration trajectory for each test seek position.

A computer program product including a computer readable medium having computer program codes for executing a procedure, comprising:

• a first set of instructions to
• perform predetermined test seeks with respect to test seek positions into which a disc is divided and seek directions,
• obtain torque compensation constants, and
• store the torque compensation constants in a torque compensation constant table;
• and
• a second set of instructions to compensate for a gain of a seek control loop at a position where a seek is performed taking into account a seek direction in a seek mode, using torque compensation constants stored in the torque compensation constant table,
• wherein the torque compensation constants are obtained by calculating a ratio of an actual seek driving current trajectory to a design acceleration trajectory for each test seek position.

An apparatus to compensate for a torque change in a seek servo of a disc drive having a disc that is divided into a plurality of tracks and regions, and a transducer to read and/or write data from and/or to the disc, the apparatus comprising:

• a controller that:
• for each region, performs test seeks moving the transducer from a given region to each track,
• determines torque compensation constants from the test seeks using test seek positions,
• stores the torque compensation constants in a torque compensation constant table, and
• when in a seek mode, selects a torque compensation constant according to a target track, using the torque compensation constant table;
• a memory device to store the torque compensation constant table;
• a torque constant compensator compensating for a gain of a seek control loop using the torque compensation constant selected by the controller;
• and
• a seek servo control circuit using a predetermined design acceleration trajectory, a predetermined design velocity trajectory, and a predetermined design position trajectory to generate a seek driving current, used in accordance with an output of the torque constant compensator to move the transducer to the target track,
• wherein the torque compensation constants are obtained by calculating a ratio of an actual seek driving current trajectory to a design acceleration trajectory for each test seek position.

A method to determine a torque compensation constant for a disc drive having a disc that is divided into a plurality of tracks and regions, and a transducer to read and/or write data from and/or to the disc, the method comprising:

• determining a value of a given track position;
• calculating a value of a test target track position by adding the given track position value to a test seek length;
• seeking for the target track;
• storing a trajectory of a seek driving current and a trajectory of a design acceleration in a buffer of a controller while seeking for the target track;
• calculating first harmonic sine coefficients for the respective trajectories of the seek driving current and the design acceleration;
• calculating the torque compensation constant;
• and
• storing the torque compensation constant in a torque compensation constant table.