H/sub 2/ and H/sub /spl infin// control applied to an electromagnetically levitated vehicle

Several magnetically levitated transport systems have been constructed, tested and constantly improved. Various technologies for the magnetic levitation system are also being developed and some of them use electromagnets for the vehicle levitation. In this work, an electromagnetically levitated vehicle prototype is studied. The vehicle levitation is achieved through the control of the gaps of these electromagnets. The constructed prototype will have independent levitation and propulsion systems; this paper considers only the magnetic levitation system. The resultant system is open loop unstable and highly nonlinear with a very restrictive equilibrium region. A SISO analytical model and closed loop identification experiments are also presented. The emphasis in this paper is related to design procedures of H ₂ and H _∞ controllers applied to the electromagnetic levitation system. For the designs of these controllers, a weighting function is employed to attenuate a resonance peak at low frequencies in the closed loop system. The results show that closed loop system responses with the H ₂ and H _∞ controllers are very similar but with better performance than the response obtained with a classical theory controller.