The Magnetic Levitation (Maglev) unit demonstrates closed loop levitation of permanent and ferromagnetic elements. The unit used for our experiments is shown in Figures 1 and 2, and the magnetic disc is shown in Figure 3.
Figure 1. The Magnetic Levitation System (Model 730 of ECP, USA)
Figure2. Side and Front View of the Maglev System
Figure 3.Top view of the magnetic disc
The plant consists of upper and lower coils that produce a magnetic field in response to a DC current. A magnet (or sometimes even two magnets) travels along a glass guide rod. By energizing the lower coil, a single magnet is levitated through a repulsive magnetic force. As the current in the coil increases, the field strength increases and the levitated magnet height is increased. For the upper coil, the levitating force is attractive.
Up to two magnets may be controlled simultaneously by stacking them on the glass rod. The magnets are of ultra-high field strength and are designed to provide large levitated displacements to clearly demonstrate the principle of levitation and motion control. Two laser-based sensors measure the magnet positions. The lower sensor is typically used to measure a given magnet position in proximity to the lower coil, and the upper one for proximity to the upper coil.
The unit can be set up in the stable and unstable (repulsive and attractive fields) configurations. If two magnets and coils are used, the field interaction between the magnets causes strong cross coupling and thus produces a true multivariable system. Thus, magnets can be added or removed to provide single loop or multi-loop plants that are stable or unstable. These configurations are illustrated in Figure 4 below.
Most experiments deal with the so-called configuration1 shown in Figures 5 and 6. It is a configuration in which the lower magnet is levitated by exciting the lower electromagnetic coil. The excitation of the lower electromagnet causes the repulsive force on the magnetic disc. The repulsive force in turn levitates the magnetic disc. It is a stable configuration.
Figure5. Schematic of Configuration 1 (Repulsive Levitation, Stable)
Figure 6. Layout diagram of Configuration1 (Repulsive Levitation, Stable)