Patent ID: 8853988

Claim:
A method for compensating for an effect of a motor that moves a stage in a stage device, the method comprising the steps of: generating an error signal by combining a desired trajectory of the stage and a measured position of the stage; generating a feedback signal with a feedback controller using the error signal; receiving an input signal corresponding to an effect of the motor, the input signal indicating a position of a moving member of the motor, wherein the effect of the motor comprising an electromotive force that varies with a movement of the moving member of the motor through a magnetic field; generating a feedforward control signal based on the input signal using a feedforward module that includes an analysis module that analyzes the input signal and estimates the effect of the motor to generate the feedforward control signal; wherein the step of generating the feedforward control signal includes the step of determining a value of the electromotive force corresponding to a future position of the moving member; summing the feedback signal and the feedforward control signal; generating a motor control signal from the summed feedback signal and feedforward control signal using a drive module; and sending the motor control signal from the drive module to the motor, thereby moving the stage of the stage device and compensating for the effect of the motor.