Method for determining a commutation offset and for determining a compensation map for a stage

摘要

A method for determining a commutation offset for a mover (250A) of a mover assembly (220C) that moves and positions a stage (220A) relative to a stage base (220B) includes controlling the mover assembly (220C) in a closed loop fashion to maintain the position of the stage (220A) along a first axis and along a second axis with the stage (220A) levitated above the stage base (220B). The method also includes the steps of (i) directing current to a coil array (240) of the mover assembly (220C) so that the mover assembly (220C) imparts a disturbance on the stage (220A); and (ii) evaluating one or more forces generated by the mover assembly (220C) as a result of the disturbance on the stage (220A) created by the mover (250A). Further, a method for generating a compensation map (1402) includes sequentially directing a plurality of excitation signals to the control of the mover assembly (220C) and determining the control commands that result from the plurality of excitation signals.

主权项

1. A method for determining a commutation offset for a mover of a mover assembly that moves and positions a stage relative to a stage base along a plane including a first axis, the mover including a coil array and a magnet array that interacts with the coil array, the method comprising the steps of:
measuring a measured position of stage with a measurement system and generating feedback regarding the measured position of the stage; controlling the mover with a control system using the feedback from the measurement system to levitate the stage above the stage base along a second axis that is vertically oriented relative to the plane, the control system including a processor; controlling the mover with the control system using feedback from the measurement system to maintain the position of the stage along the first axis and along the second axis; and obtaining information of a commutation offset for the mover, while the stage is levitated above the stage base with the mover and while controlling the mover with the control system using feedback from the measurement system to maintain the position of the stage along the first axis and along the second axis, utilizing the steps of (i) directing current to the coil array with the control system so that the mover imparts a disturbance on the stage, and (ii) evaluating one or more forces generated by the mover under the control of the control system and required to maintain the measured position of the stage along the first axis and along the second axis as a result of the disturbance on the stage to obtain information of the commutation offset, wherein the commutation offset represents an adjustment to a position of the coil array relative to the magnet assembly at the time the disturbance is imparted on the stage.