Patent ID: 7782446

Claim:
A stage system for a lithographic apparatus comprising: a stage; a plurality of actuators configured to act on the stage, the actuators being over-determined in an actuator degree of freedom; at least two sensors configured to each measure a position dependent parameter of the stage and to provide a respective sensor signal, the at least two sensors being arranged to measure the respective position dependent parameters in a sensor degree of freedom; a controller configured to provide a controller output signal to at least one of the plurality of actuators in response to a setpoint and the position dependent parameter as measured by at least one of the sensors; and a further controller provided with the position dependent parameters as measured by the at least two of the sensors, the further controller configured to determine a difference between the position dependent parameters from the at least two of the sensors, the determined difference being indicative of a resonance mode of the stage, and to provide a further controller output signal to at least one of the plurality of actuators in response to the determined difference, the at least one of the plurality of actuators being controlled by the further controller using the further controller output signal to reduce the resonance mode.