Hybrid non-linear differentiator design for a permanent-electro magnetic suspension maglev system

In this study, to solve the vehicle-guideway resonance problem when a maglev train is suspended on an elastic beam at a low speed, a gap differentiator with global fast convergence is designed. The differentiator in possession of a simple algorithm but without obvious oscillation phenomenon, has a good ability of filtering out the noise. From the analysis of amplitude frequency and phase frequency characteristics of the differentiator, the authors point out that the parameter choice should be based on the linear differential unit, and the auxiliary non-linear unit implements phase compensation, so the differentiator has a nearly 90° phase advance in the effective frequency band. The digital gap differentiator goes through the functional simulation with algorithm level in the open-loop and hardware test in the loop independently. Finally, the designed gap differentiator is used in a closed-loop suspension control system of permanent-electro magnetic suspension -type maglev train, the theoretical analysis and simulation experiments show that the differentiator can restrain the resonance phenomenon on the elastic beam effectively.