Magnetic disc drive system having automatic offset and gain adjustment means

A magnetic disc drive system, comprising:

• a magnetic head for reading a magnetic disc;
• an actuator connected to and moving said magnetic head;
• a control current detection circuit connected to said actuator and detecting a control current flowing through said actuator;
• a position signal generation circuit coupled to said magnetic head and generating a position signal corresponding to a position of said magnetic head;
• a speed control circuit coupled to said control current detection circuit and effecting a seek control of said magnetic head;
• a position control circuit connected to said control current detection circuit and effecting a fine position control of said magnetic head after completion of said seek control;
• and
• offset adjustment means operatively connected to said speed control circuit, said position control circuit, said control current detection circuit and said position signal generation circuit, operating immediately upon receipt of power and before receipt of a seek command, for calculating one or more offset correction values along one or more cylinders of the magnetic disc dependent upon the detected control current from said control current detection circuit when a position of said magnetic head is controlled under said fine position control by said position control circuit, said offset adjustment means outputting said calculated one or more offet correction values to said speed control circuit and said position control circuit, said offset adjustment means controlling said speed control circuit to effect the seek control responsive to a normal seek command in accordance with said calculated one or more offset correction values, and controlling said position control circuit to effect the fine position control in accordance with said calculated one or more offset correction values after completion of the seek control by said speed control circuit.