EXPERIMENTAL VALIDATION OF A SMART BIAS ACTIVE MAGNETIC BEARING CONTROLLER

Active magnetic bearings (AMBs) are experiencing an increased use in many rotating machines as an alternative to conventional mechanical bearings. An AMB provides a noncontact means of supporting a rotating shaft through an attractive magnetic levitation force. The magnetic force is generated/controlled by passing an electric current through a coil wound around a stator made of ferromagnetic material (i.e., an electromagnet). See Figure 1 for an illustration of a one degree-offreedom (DOF) AMB. Due to the non-contact nature of the bearings and rotor, AMBs have the unique ability to suspend loads with no friction, allow the operation of rotors at higher speeds, and operate under environmental conditions that prohibit the use of lubricants. Furthermore, since AMBs can be actively controlled, they offer other advantages over mechanical bearings such as eliminating rotor vibration through active damping, adjusting the stiffness of the suspended load, compensating for rotor misalignment and changes in rotor speed, and providing an automatic rotor balancing capability.