Patent ID: 7167334

Claim:
In a hard drive assembly having an actuator, the actuator having an actuator voltage, a method of controlling the actuator comprising the steps of: sampling the actuator voltage; sampling an actuator current; calculating a BEMF using the sampled actuator voltage and sampled actuator current; calculating a velocity error using the BEMF and a selected target voltage; producing a digital voltage command for compensating the actuator voltage for the velocity error; and applying a voltage at the actuator according to the digital voltage command, wherein the digital voltage command, Vcmd, may be described by the formula, Vcmd=ki*[x ( n )+ x ( n− 1)]+ yi ( n− 1)+ kp*x ( n )+ ffwd [Equation 4], wherein, ki is a constant representing the magnitude of integral compensation to apply, x(n) is a sample of the current value of the error term Ev, yi represents the output of the integral portion of the compensation, and ffwd represents a feed forward voltage that allows the loop to run with a zero error within the dynamic range of the integrator.