H_ ¡Þ Control Of Magnetic Levitation System

Maglev is a new mechatronics technology which can make an object levitate without contact and then decrease the mechanical loss. It has played an important role in the fields of aerospace, machinery manufacturing, transportation, etc. Now, the nonlinearities, friction, couple and uncertainties in the control of magnetic levitation system are also difficult to deal with. In this paper, a class of magnetic levitation systems with modeling uncertainties, couple and friction are researched with the ECP Model 730 magnetic levitation system. Several problems in the control of practical system are analyzed and corresponding methods are followed. The main contents of this paper are concluded as follows:1) The linear mathematic models of the ECP Model 730 magnetic levitation system in the two different confrontations of single magnet or double magnets are built with the consideration of the nonlinearities of the sensor, actuator and the interaction between the two magnets.2) The uncertainties of the single magnet levitation system are analyzed and attributed to the mixed sensitivity problems, and then an H∞controller is designed. The friction model of the single magnet levitation system is built through genetic algorithm against to the problem that the friction effects can't be eliminated with the H∞controller and then the friction effects can be compensated on the basis of the friction model. The experimental results show that this method overcomes the friction of the system to a certain extent. Further, the friction effects can't be eliminated completely with the friction compensation because there are uncertainties in the friction model. For this problem, the friction is regarded as the disturbance in the input-end of the system and the description of disturbance is added into the sensitivity weight function. Then a new H∞controller which has an input-end disturbance rejection capacity is designed. The dynamic performance, steady-state performance, disturbance rejection capacity and the robustness to four different kinds of parameter perturbations of the new H∞control system are verified through the simulation. At last, the single magnet levitation system with the final control algorithm is debugged. The experimental results show that the magnet has a good dynamic tracking performance, which verifies the effectivity of the new H∞controller.3) The characteristics of the double magnets levitation system are analyzed and the differences between the single magnet and double magnets levitation systems are discussed. For the problems of friction and couple, an H∞controller for the double magnets levitation system is designed on the basis of friction compensation and couple compensation. The dynamic performance, steady-state performance, disturbance rejection capacity and the robustness to four different kinds of parameter perturbations of the H∞control system are verified through the simulation. At last, the double magnets levitation system with the H∞controller is debugged, the experimental results show that the H∞control system behaves a good dynamic and steady-state performance which verifies the effectivity of the new H∞controller.