Actuator control device

An actuator control device comprising:

• a head which at least reproduces information from a disk;
• an actuator which moves said head;
• a position detector which detects a position of said head;
• a control unit which controls said actuator based on the output of said position detector;
• a disturbance observer which estimates disturbance added to said actuator;
• a storage which stores the disturbance estimated by said disturbance observer;
• an adder which adds the output of said disturbance observer and the output of said storage to the output of said control unit;
• a driving circuit which drives said actuator based on the output of said adder;
• an abnormality detector which detects an application of am external force exerted on a disk apparatus which drives the disk apparatus into an out-of-tracking state, based on the position of said head and the output of said disturbance observer;
• and
• a modifying unit which modifies the output of said disturbance observer according to the output of said abnormality detector.

An actuator control device comprising:

• a head which at least reproduces information from a disk;
• an actuator which moves said head;
• a position detector which detects a position of said head;
• a control unit which controls said actuator based on the output of said position detector;
• a disturbance observer which estimates disturbance added to said actuator;
• a storage which stores the disturbance estimated by said disturbance observer;
• an adder which adds the output of said disturbance observer and the output of said storage to the output of said control unit;
• a driving circuit which drives said actuator based on the output of said adder;
• an abnormality detector which detects an application of an external force exerted on a disk apparatus based on the position of said head and the output of said disturbance observer;
• and
• a modifying unit which modifies the output of said disturbance observer according to the output of said abnormality detector,
• wherein said abnormality detector includes a feedback area detector which detects a positive feedback area and a negative feedback area at the position of said head.