Magnetically supported plate

Description

For teaching and research purposes as well as for demonstrating active magnetic bearing technology, an experimental setup was developed at the LSR in which a plate levitates in a magnetic field generated by four electromagnets arranged above the plate. Thanks to flatness-based control methods, the plate, which weighs around 4.7 kg, can be positioned vertically below the electromagnets, with air gaps from one to around five millimeters wide being possible. The panel is controlled using industrial real-time hardware, whereby the vertical position of the panel is measured without contact.

So far, algorithms for the robust and sensitive real-time detection of rapidly changing disturbing forces and for the automatic diagnosis of sensor and actuator errors have been developed on the magnetically mounted plate (see Derivative Estimation and Discontinuity Detection). In this way, these disturbances can be compensated for even at very low amplitudes, and highly precise control of the position trajectories can be achieved. Thanks to model-based approaches, the developed algorithms do not require the use of additional sensors. Good robustness is achieved against typical, practically relevant disturbances, such as against measurement noise and non-modeled natural oscillations of the plate. Therefore transferability to other applications is possible.

The test setup is regularly used in the context of public relations, for example at the Hannover Messe Industrie 2013, the open day of the university and measures for student recruitment (see media coverage).

Video: Juggling a table tennis ball with a plate floating in a magnetic field

The floating plate is automatically controlled in such a way that a table tennis ball bounces continuously. Ball position is not measured. Instead, collisions between the 2.7 g table tennis ball and the 4.7 kg tabletop are detected using a simple mathematical process model and algebraic estimation methods. The estimation results are used to move the plate appropriately.