Patent ID: 8120302

Claim:
A servo control apparatus for performing drive control on an electric motor and a load machine on the basis of a torque command, comprising: a PI control section for calculating a basic signal of the torque command on the basis of a deviation between a speed command and a feedback speed, a disturbance observer for outputting the torque command on the basis of the basic signal of the torque command and a rotational speed of the electric motor; and a phase advance compensation observer for generating, from the basic signal of the torque command and the rotational speed of the electric motor, an output of a nominal plant serving as an element in which no delay occurs to output the output as the feedback speed, wherein the disturbance observer inputs the rotational speed of the electric motor to an inverse system of the nominal plant, determines, as a disturbance estimation signal, a value obtained by subtracting an output of the inverse system of the nominal plant from the torque command, inputs the disturbance estimation signal to a first low-pass filter, and adds an output of the first low-pass filter to the basic signal of the torque command to obtain the torque command.