Patent ID: 8040098

Claim:
A position controller that controls driving of a motor and a load machine, comprising: a position control part that calculates a speed command on the basis of a difference between a position command and a rotation position of the motor; a PI control part that calculates a torque command on the basis of a difference between the speed command and a feedback speed; a phase lead compensator that calculates a phase lead compensation signal of the torque command on the basis of the speed command; an adder that calculates a new torque command by adding the phase lead compensation signal of the torque command to the torque command; and an observer that receives the new torque command and a rotation speed of the motor, inputs a value obtained by subtracting an output of a delay element model from the rotation speed of the motor into an observer compensator, inputs a value obtained by adding an output of the observer compensator to the new torque command into a machine movable part model, inputs an output of the machine movable part model into the delay element model, and outputs the output of the machine movable part model as the feedback speed, wherein the delay element model is defined by a primary delay filter, and wherein a gain of the phase lead compensator is a value obtained by subtracting a proportional gain of the PI control part from a value in which a time constant of the primary delay filter is multiplied by an integral gain of the PI control part.