Weihua Ma’s research while affiliated with Southwest Jiaotong University and other places

The EMS (Electromagnetic Suspension) maglev train uses active control to achieve stable levitation. The coupled vibration problem of the levitation system itself has always been a key factor limiting the development of EMS maglev train. In order to achieve vibration suppression and rapid response of the levitation control system, a double-loop PID (Proportional-Integral-Derivative) control strategy is first designed. Subsequently, a nonlinear function is used to adjust the system error, enhancing the response speed of the levitation control system. An ESO(extended state observer) is established to reduce the interference of external excitation, and an improved sliding mode switching function of the levitation control system is designed to reduce system chattering. Finally, a fast active disturbance rejection control-sliding mode control (Fast ADRC-SMC) strategy of EMS maglev train is proposed. A comparative analysis is conducted to evaluate the suppression capability and responsiveness of different control strategies under external excitations. Furthermore, the effectiveness of the Fast ADRC-SMC levitation control strategy in suppressing vibrations is validated through comparison with actual measurement data from commercially operated maglev lines. The research results indicate that the proposed Fast ADRC-SMC levitation control strategy exhibits excellent vibration suppression and rapid response capabilities, and the maximum vibration acceleration response of the levitation system is approximately 0.54 m/s ² , and the maximum vibration acceleration response of the track beam is about 0.11 m/s ² . Compared to the ADRC control strategy, the system response speed is improved by approximately 2 s.

Track irregularities are the main factors causing changes in suspension stability and vibrations in EMS (Electro-magnetic Suspension) maglev trains. Due to the scarcity of actual measurement data on EMS maglev track irregularities, this paper utilizes the principles of the mid-chord offset method to develop a track irregularity detector with a 1-m test chord length. Tests were conducted on the maglev line in Qingyuan, Guangdong. Based on the “using small to predict large” algorithm, data simulating a 3-m test chord length were output. The experimental data were processed to remove trend items and outliers, and an inverse filter was designed to counteract the amplitude gain error of the mid-chord offset method, obtaining accurate data on vertical and lateral track irregularities. The results show that the amplitude and power spectral density (PSD) fluctuations of track irregularities on the left and right rails of the measured line section are similar, with height irregularities of 2.5–3 mm and alignment irregularities of 1–1.5 mm. Periodic wavelength components related to the longitudinal spacing of sleepers, rail length, and beam span, such as 1.2 m, 6.5 m, 12.5 m, and 25 m, are evident, highlighting the need for enhanced inspection and maintenance of these structural components in engineering projects.

Linear induction motors (LIMs) are positioned head-to-tail in medium and low-speed maglev (MLSM) trains, and the interaction due to small spacing between two LIMs is not yet clear. In this work, based on the 2D electromagnetic field theory, the vector magnetic potential (VMP) of each region was solved, and the traction forces of two adjacent LIMs were derived. Subsequently, the correctness of the theoretical model was verified by simulation. Finally, the effects of the spacing, wiring type, pole pitch, speed, etc., on the traction forces of two adjacent LIMs were analyzed. The results show that the traction force of LIM1 (arranged in front) is almost unaffected by LIM2 (arranged behind LIM1), while that of LIM2 fluctuates periodically with the spacing, and the smaller the spacing, the greater the fluctuation amplitude. Meanwhile, the larger the pole pitch, the more the pole number, the greater the slip frequency, and the lower the speed, the smaller the effect of LIM1 on LIM2. When the spacing takes 1.1 to 1.6 times the pole pitch, the traction force of LIM2 is larger than that of LIM1. The achievements can provide technical support for enhancing the traction performance of the LIMs in the MLSM trains.

The wheel wear of heavy-duty locomotives is more complicated than that of other vehicles when it affects tractive force and adhesion control. The purpose of this article is to calculate wheel wear on a curved track using a co-simulation dynamic model of a heavy-duty locomotive with adhesion control. Additionally, the effect of creep threshold, decline slope, curve radius, and passing speed on wheel wear is further investigated. The findings demonstrate that wheel wear can be successfully decreased by adjusting the creep threshold and decline slope of adhesion control parameters. The wheel-rail stick-slip vibration behavior on the curve track can be eliminated by increasing the curve’s radius and passing speed, but the vertical wear at the left wheel’s flange will rise sharply with the increase of passing speed on right hand curve.

Maglev vehicles apply the entire vehicle load uniformly onto bridges through levitation forces. In assessing the dynamic characteristics of the maglev train–bridge coupling system, it is reasonable to simplify the distributed levitation force as a concentrated force. This article theoretically derives the analytical response of bridge dynamics under the action of a single constant force and conducts numerical simulations for a moving single constant force and a series of equally spaced constant forces passing over simply supported beams and two-span continuous beams, respectively. The topic of discussion is the response of bridge dynamics when different degrees of force concentration are involved. High-precision displacement and acceleration sensors were utilized to conduct tests on the Shanghai maglev line to verify the accuracy of the simulation results. The results indicate that when simplifying the distributed levitation force into a concentrated force model, a frequency ratio can be used to analyze the conditions for resonance between the train and the bridge and to calculate the critical speed of the train; the levitation distribution force of a high-speed maglev vehicle can be simplified into four groups of concentrated forces based on the number of levitation frames to achieve sufficient accuracy, with the dynamic response of the bridge being close to that under distributed loads.