Abstract: A device for positioning a body (5) by means of at least one pair of electromagnets (13, 15). A position sensor (29) measures the size of an air gap (23) between one of the electromagnets (13, 15) and a guide beam (1). An output signal of the position sensor (29) is applied to an electronic control unit (35) which passes a control current through the electromagnets (13, 15) in dependence on a difference between the measured and a desired size of the air gap (23). In one embodiment an electrical switch (53) is connected between the control unit (35) and the two electromagnets (13, 15) controlled by the control unit (35), applying the control current to only one of the two electromagnets (13, 15) in dependence on the polarity of a control signal from the control unit (35).

Abstract: A device for positioning a body (5) by means of at least two electromagnets (13, 15). A position sensor (29) measures the size of an air gap (23) between one of the electromagnets (13, 15) and a guide beam (1). An output signal of the position sensor (29) is applied to a linear electronic control unit (35) which passes a control current through the electromagnets (13, 15) in dependence on a difference between the measured and a desired size of the air gap (23). An electronic root extractor (37) is connected between the control unit (35) and the two electromagnets (13, 15). An output signal of the root extractor (37) has a value equal to the square root of a control signal coming from the control unit (35). In this way a force exerted by the electromagnets (13, 15) on the guide beam (1) is proportional to the value of the control signal, so that a control is obtained with the linear control unit ( 35) in which the stiffness and bandwidth are independent of the value of the control current.

Abstract: A device for positioning a body (5) by means of at least two electromagnets (13, 15). A position sensor (29) measures the size of an air gap (23) between one of the electromagnets (13, 15) and a guide beam (1). An output signal of the position sensor (29) is applied to an electronic control unit (35) which passes a control current through the electromagnets (13, 15) in dependence on a difference between the measured and a desired size of the air gap (23). An electronic multiplier (47, 59) is connected between the control unit (35) and each of the electromagnets (13, 15), multiplying a control signal from the control unit (35) by the output signal from the position sensor (29). In this way a force exerted by the electromagnets (13, 15) on the guide beam (1) depends exclusively on the value of the control signal and not on the size of the air gap (23), so that a position-independent control is obtained.

Abstract: An optical lithographic device having a machine frame (1) to which is fastened a lens system (11) having a vertical optical main axis (13). Below the lens system (11), a positioning device (35) is fastened on a support member (3) of the machine frame (1), by means of which device an object table (27) is displaceable relative to the lens system (11) over a guide surface (5) of the support member (3) extending perpendicular to the optical main axis (13).The device is provided with a force actuator system (67) fastened to a reference frame (83) and controlled by a feedforward control system (95). The force actuator system (67) exerts a compensatory force on the support member (3) with a direction opposite to a direction of a reaction force simultaneously exerted by the positioning device (35) on the support member (3), and with a value which is substantially equal to a value of the said reaction force.