Position control system, a lithographic apparatus and a method for controlling a position of a movable object

A lithographic apparatus comprising:

• a patterning device support configured to support a patterning device, the patterning device being capable of imparting a radiation beam with a pattern in its cross-section to form a patterned radiation beam;
• a substrate support constructed to hold a substrate;
• a projection system configured to project the patterned radiation beam onto a target portion of the substrate;
• and
• a position control system configured to control a position of a movable object, the system comprising
• a position measurement system configured to measure a position of the movable object with a sensor and a sensor target, the sensor being arranged on the movable object and the sensor target being substantially stationary, or vice versa, the position measurement system configured to output a measured position signal representative of the measured position of the movable object;
• a comparator configured to provide an error signal;
• a controller configured to provide a control signal based on the error signal;
• a feed-forward device configured to provide a feed-forward signal based on a first signal related to a desired position;
• one or more actuators configured to act on the movable object based on the control signal and the feed-forward signal;
• a compliance compensator configured to provide a compliance compensation signal, and
• a module configured to receive the measured position signal and the compliance compensation signal and provide a feedback signal based on the measured position signal and the compliance compensation signal, the feedback signal to be received by the comparator,
• wherein the error signal is determined using a set-point position signal, the measured position signal, and the compliance compensation signal.

A method for controlling the position of a movable object, comprising:

• determining a position of a sensor or sensor target on the movable object;
• determining an error signal;
• generating a control signal based on the error signal;
• generating a feed-forward signal based on a first signal related to a desired position of the movable object;
• actuating one or more actuators based on the control signal and the feed-forward signal, and
• providing a compliance compensation signal,
• wherein the error signal is determined by comparing a set-point position signal, a signal representative of the measured position of the movable object, and the compliance compensation signal, and
• wherein the measured position signal and the compliance compensation signal are inputted in a module to provide a feedback signal based on the measured position signal and the compliance compensation signal.