Improvement in or relating to the control of electro-magnets

摘要

A support actuator 20 comprises an electro-magnet 21 having an input current 22 , provided through a current controller 23 , and which is arranged to generate a magnetic field 24 having a variable intensity proportional to a variable current 25 supplied by the controller 23 . The intensity of the field 24 is controlled to ensure that the magnet 21 is separated from a support armature 26 arranged to carry a load by an operational gap 27. A load cell 28 is connected between the armature 26 and a mounting position 29 for the armature 26 . The cell 28 produces a control signal 30 representing variations in force generated by the magnetic field 24 which acts on the load, and the signal 30 is fed backward, along a feedback control path 31 to the controller 23 so as to control the variable current 25 such that it is made substantially equal to a gain demand force D.