Degrees of Freedom Control through Three Electromagnets and Three Linear Induction Motors
Configuration that the mover has three electromagnets and three linear induction motor (LIM) has been proposed for contactless flexible conveyance system. Hybrid electromagnet that uses permanent magnet can let power consumption converge to zero in steady state, and its stator becomes simple because the combination of three LIM’s is used for two-dimensional drive. The normal attractive force of LIM can increase the carrying capacity of the mover, although it can be also disturbance force for the stabilization of the magnetic levitation system. Authors have experimentally confirmed that the proposed configuration can realize six-degrees of freedom control of the mover. Position sensing for the closed loop control of two-dimensional linear drive is difficult: one possible approach based on visual sensing combined with dual sample-rate digital observer is proposed and discussed.
4 Poles 3 Degrees of Freedom Magnetic Levitation Control and its Coordination with Two-Dimensional Linear Motor
Electromagnetic suspension (EMS) has been widely used in many industrial fields because of various advantages in practical use. The U-type magnets are often used to generate the levitation force in the EMS system. This conventional electromagnet, however, can only control one degree-offreedom. It cannot construct a levitation system solely by itself. A 4-pole type yoke hybrid electromagnet is proposed instead of the usual U-type magnet and its magnetic levitation control is studied in this paper. The basic structure and characteristics of the proposed magnet are described, and the control systems are designed. The semi-zero-power controller, with a disturbance observer, is proposed to improve the performance of the control system. Furthermore, the combination with the linear motor is discussed.
Ground Fault Protection for Electric Utility Generating Station Medium Voltage Auxiliary Power Systems
Most generating station designs have medium voltage auxiliary power systems with low resistance grounded neutrals.1 In order to provide even higher reliability, the auxiliary power distribution system configurations supply increasingly redundant process equipment.