Collaborative control of a levitation module for maglev trains with physical contact prevention and user-defined convergence time

The levitation module of maglev trains is contact-prone between electromagnets and guideways due to its high nonlinearity and various external disturbances. Hence, the coupling structure between the electromagnetic points in a levitation module calls for safe and collaborative control. To achieve this goal, this study proposes a novel collaborative levitation control scheme with physical contact prevention. Considering operational safety requirements confronted by the levitation system, a barrier function is introduced to address the physical contact problem, which strictly limits the levitation gap within an allowable range. Moreover, considering the transient response of the controlled system, the predefined-time stability is synthesised, which ensures that the tracking errors converge to a very small neighbourhood of zero within an arbitrarily settling time determined by users. This brings great convenience of tuning controller parameters and avoids non-trivial tuning with a large set of parameters by trails and errors. In addition, quadratic functions are integrated to guarantee the nonsingularity of control signals to enhance practicality. A series of numerical simulations verify the effectiveness of the proposed control scheme.