Patent ID: 8149533

Claim:
A method of estimating a coil resistance and a torque constant for load and unload control of a head attached to an arm driven by a voice coil motor, the method comprising: measuring a head velocity and a terminal voltage of a coil of the voice coil motor at least two times before unloading in a control system wherein a back electromotive voltage of the coil is proportional to a head velocity and a coil current is proportional to a command voltage and during a period wherein the head velocity is not influenced by a transient response of inductance due to a change of the command voltage and the head velocity is determined by a mathematical equation for the terminal voltage of the coil, the command voltage, the coil resistance, and the torque constant; and calculating a torque constant and a coil resistance based on command voltages, at least two measured head velocities and at least two measured terminal voltages of the coil, and the mathematical equation.