Magnetic suspension and vibration control of beams for non-contact processing

This paper presents an integrated approach to magnetic suspension of a tubular beam for noncontact processing. We describe noncontact sensors and actuators, structure modelling/identification, and control methods for such systems. We have also designed an experiment that uses 8 sensors and 8 actuators to suspend a 3 m long, 6.35 mm diameter steel tube. Results from this experiment are presented herein. To facilitate the experiment, we designed a novel two-dimensional position sensor by utilizing the concept of an x-y variable differential transformer. We also designed two types of actuators that apply magnetic force on the tube in two axes. The system dynamics are modelled theoretically, and identified experimentally from within the closed-loop system. In order to control the system under varying boundary conditions, we propose a slow roll-up lead compensator. We also introduce sensor interpolation and sensor averaging methods to make the control loop more robust. Our proposed ideas are verified in the experimental results.