Patent ID: 7929242

Claim:
A magnetic disk apparatus comprising: a driving section for moving a magnetic head recoding and reproducing information in a magnetic disk; and a controller for controlling the driving section, the controller including: a position-error feedback control system having an integrator and a phase lead compensator and obtaining a position command based on difference between target position and detection position of the magnetic head to perform feedback control of the driving section; and a two-freedom-degree control system inputting a target move distance of the magnetic head and outputting a current command to the driving section by using a mathematic model of the driving section, the controller providing the driving section with an output of the integrator and therewith updating the mathematical model by using an output of the phase lead compensator, in each of the times of positioning control and seek of the magnetic head, a velocity feedback gain Gv determining a state in the positioning control being set so that a matrix A + BL = [ 1 2 - B 21 · b 1 · G v 1 + ( - B 21 · G v - 2 · b 1 ) ] have an eigenvalue of zero, where b1 represents inclination of a target velocity curve, B21 represents a model gain, A = [ 1 2 0 1 ] B = [ 0 B 21 ] and L = [ - b 1 · G v - G v - 2 · b 1 · 1 B 21 ] .