A control system for controlling a position of a mass, such as, for
example, a substrate holder in a lithographic apparatus, is presented
herein. The control system comprises a first input to receive a desired
position of the mass, a second input signal to receive a feedback signal
indicative of the actual position of the mass, a control unit that
produces a signal indicative of the required control force based on the
difference between the desired mass position and the actual mass
position, and an estimator unit that calculates an estimated relation
between the control force and mass status information indicative of at
least one of a position of said mass, a velocity of said mass, and an
acceleration of said mass, and a third input to receive a feed-forward
signal indicative of the desired mass acceleration. The control system
then determines the control force needed to accelerate the mass and move
it to a desired position based on the estimated relation and the desired
mass acceleration.