Patent ID: 6911754
Filing Date: 2005-06-28
Classification: F16F

Abstract:
1. A support apparatus comprising: a plurality of electro-magnetic support actuators arranged in an array and coupled to a mounting of a load, so as to support the mounting and the load by electro-magnetic levitation, wherein each support actuator comprises: a current controller operable to produce a variable current; an electro-magnet connected to receive the variable current and to generate a magnetic field dependant on the variable current; a support armature separated from the electro-magnet by an operational gap and supported by the magnetic field; a first control means arranged to detect force generated by the electro-magnet and to operate the current controller dependant on variations in the force generated, and the first control means being arranged to vary the variable current in the electro-magnet such that the force generated substantially equals a given force demand value, whilst permitting the operational gap to vary; and means for generating said force demand value for each support actuator comprising: a plurality of displacement measurement devices attached to the mounting at selected points; and a global demand controller arranged to utilise data signals from the displacement measurement devices to generate signals relating to rigid body modes of movement of the mounting for each of the support actuators and to generate therefrom, signals representing said force demand values, for maintaining a mean position of said mounting.