Cooperative Control Of Multi-Levitation Points For High-Speed Maglev Trains Under Guideway Irregularities

Levitation control is one of the key technologies of maglev vehicles.Engineering application conditions of high-speed maglev vehicles have been satisfied,but a series of technical issues still have to be solved.With the increase of operational speed,the influence of guideway irregularities on the levitation control system becomes more significant.Supported by the National Key Research and Development Plan of the “13th Five-Year Plan”,this dissertation focuses on the levitation performance deterioration of maglev vehicle operation subject to irregularities and studies the control theories and methods to achieve a controlled levitation system with disturbance-rejecting,safety and comfort.To tackle the continuous excitation of irregularities on the maglev levitation system in this dissertation,a nonlinear levitation electromagnet model with secondary suspension is built at the first stage.A robust levitation controller with input saturation is designed by combining the fixed-time disturbance observer,of which stability is globally finite-time.Numerical simulation under various operation scenarios demonstrates its satisfactory performance.Next,a nonlinear half-bogie model with a rigid coupling structure is established.To deal with the cooperation between the two electromagnets in a half bogie,the anti-disturbance cooperative controller is constructed based on the adaptive disturbance observer,and the event-triggered mechanism is introduced to reduce actuation time and achieve lazy cooperation.Finally,the full bogie dynamics considering secondary suspension and irregularity excitation is formulated,and a multi-objectives controller is proposed to guarantee air gap tracking,levitation safety,ride comfort and input saturation.The main contents and contributions are as follows:First,regarding the nonlinear electromagnet dynamics with secondary suspension and irregularity excitation,a robust finite-time levitation controller is proposed for maglev vehicles.To begin with,the nonlinear levitation model for an electromagnet including secondary suspension and irregularities is constructed.To effectively compensate for the guideway irregularities,external disturbances and input truncation,the fixed-time disturbance observer is introduced and the robust finite-time controller is designed.Theoretical analysis establishes the global stability of the whole system.Simulations under various operation scenarios,including high speed,time-varying speed,gust and slope,verify the effectiveness and robustness of the proposed control scheme.Extended simulations on a full bogie with load also demonstrate the effectiveness.Second,for the half bogie with two electromagnets rigidly coupling on one side,the predefined-time anti-disturbance cooperative control between two levitation points is studied for the half bogie.This dissertation establishes a newly nonlinear model for the half-bogie,which fully reflects the rigid coupling relationship between two electromagnets on a side,irregularity excitation on half-bogie dynamics and external disturbances.Then,the adaptive disturbance observer with a simple structure is adopted to estimate the irregularities and external disturbances.Combining speed function and backstepping techniques,a predefined-time cooperative controller is derived for the two coupling levitation points.Moreover,the lazy cooperative model is designed by integrating the event-triggered mechanism to decrease the actuation times.The stability of the closedloop system is proven.Numerical simulations under two types of irregularities verify the effectiveness of the cooperative control.Third,considering the full bogie model with secondary suspension,a multiobjectives controller is synthesized to prevent physical contact and uncomfortableness resulting from guideway irregularities.The high-speed maglev full bogie model with secondary suspension and multi-degree of freedom is formulated,which fully reveals the influences of load and secondary suspension on electromagnets.Then,considering latent magnet smashing,a novel control barrier function is designed,and with this function,a safe levitation controller is constructed to guarantee the air gaps greater than the permissible minimal levitation distance.Meanwhile,to promise ride comfort,the vertical acceleration constraints of the cabin is transformed into the indirect constraints of the control input.Next,the objectives,including air gap tracking,levitation safety,passenger comfort,as well as input saturation are synthesized by the quadratic programming.Finally,numerical simulations demonstrate that the proposed controller addresses all the control goals and constraints well.