Stability enhancement of magnetic levitation ball system with two controlled electomagnets

Magnetic levitation ball system is a highly nonlinear and unstable system. If the system is linearised at the equilibrium point, the achievable balance range of the magnetically levitated ball is very short with one electromagnet. This paper presents an improved magnetic levitation ball system, that contains two electromagnets, where one electromagnet is set above the magnetic ball for pulling, and another one is set under the magnetic ball for pushing. In addition, this paper applies a 2-DOF (degree-of-freedom) PID (proportional-integral-derivative) controller instead of 1-DOF PID for the control of the two electromagnets so that they can work corporately to make the magnetic ball levitate in the air. These improvements not only increase the balance range of the ball, but also make the magnetic levitation ball system more stable. The effectiveness of the proposed system is further validated by both numerical simulations and real experiments.