Disk drive having separate motion sensors for base and actuator

A disk drive, comprising:

• a head disk assembly including a base, a rotating disk, and a rotary actuator that pivots relative to the base;
• a first motion sensor rigidly coupled to the base for sensing motion of the head disk assembly, wherein the first motion sensor rigidly coupled to the base is mounted to a PCBA that is rigidly secured to the base;
• and
• a second motion sensor mounted to the rotary actuator for sensing motion of the rotary actuator.

A disk drive, comprising:

• a head disk assembly including a base, a rotating disk, and a rotary actuator that pivots relative to the base;
• a first motion sensor rigidly coupled to the base for sensing motion of the head disk assembly;
• and
• a second motion sensor mounted to the rotary actuator for sensing motion of the rotary actuator, wherein the first and second motion sensors are substantially vertically aligned when the rotary actuator is at a particular position relative to the rotating disk.

A disk drive, comprising:

• a head disk assembly including a base, a rotating disk, and a rotary actuator that pivots relative to the base;
• a first motion sensor rigidly coupled to the base for sensing motion of the head disk assembly;
• and
• a second motion sensor mounted to the rotary actuator for sensing motion of the rotary actuator, wherein the first and second motion sensors are substantially vertically aligned when the rotary actuator is at a particular position where a read/write head supported by the rotary actuator is located over a middle diameter of the disk.

A disk drive, comprising:

• a head disk assembly including a base, a rotating disk, and a rotary actuator that pivots relative to the base;
• a first motion sensor rigidly coupled to the base for sensing motion of the head disk assembly;
• and
• a second motion sensor mounted to the rotary actuator for sensing motion of the rotary actuator, wherein the first and second motion sensors comprise first and second linear accelerometers, and the second linear accelerometer has its sense axis substantially perpendicular to a long axis of the rotary actuator.

A method of controlling a disk drive having a head disk assembly including a base, a rotating disk, and a rotary actuator that pivots relative to the base, in order to achieve improved track following performance by reducing off-track error caused by shock and vibration, the method comprising the steps of:

• generating a first sense signal corresponding to a motion of the head disk assembly;
• generating a second sense signal corresponding to the motion of the rotary actuator;
• comparing the first and second sense signals in order to detect off-track movement of the rotary actuator while track-following;
• and
• compensating for the off-track movement.

A method of controlling a disk drive having a head disk assembly including a base, a rotating disk, and a rotary actuator that pivots relative to the base, in order to achieve improved track following performance by reducing off-track error caused by shock and vibration, the method comprising the steps of:

• generating a first sense signal corresponding to a motion of the head disk assembly;
• generating a second sense signal corresponding to the motion of the rotary actuator;
• comparing the first and second sense signals in order to detect off-track movement of the rotary actuator while track-following;
• and
• compensating for the off-track movement by modifying a nominal digital command in a servo control loop with a digital value corresponding to the result of the comparing step.

A method of controlling a disk drive having a head disk assembly including a base, a rotating disk, and a rotary actuator that pivots relative to the base, in order to achieve improved track following performance by reducing off-track error caused by shock and vibration, the method comprising the steps of:

• generating a first sense signal corresponding to a motion of the head disk assembly;
• generating a second sense signal corresponding to the motion of the rotary actuator with a linear accelerometer that has its sense axis substantially perpendicular to a long axis of the rotary actuator;
• comparing the first and second sense signals in order to detect off-track movement of the rotary actuator while track-following;
• and
• compensating for the off-track movement.