# An Experimental Validated Control Strategy of Maglev Vehicle-Bridge Self-Excited Vibration
## 5 Numerical and Experimental Validation
### Experimental Validation  
The experiments were carried out on the maintenance platform of the Tangshan maglev test line, as shown in Figure 12. The levitation control system (Beijing Enterprises Holdings Maglev Technology Development Co., Ltd, Beijing, China) consists of a Pulse Width Modulation(PWM)  
Figure 11: The numerical verification for vibration suppression method, which is activated at \(t\) = 4 s: (**a**) the displacement of bridge; (**b**) the displacement of electromagnet; (**c**) the estimated displacement of electromagnet, and (**d**) the contrast signals of the estimated and the real displacement of electromagnet.  
Figure 10: The overall nonlinear dynamic model with ten modules.  
chopper, suspension modules and Power PC-based digital processor. The digital process is capable of performing the proposed vibration control algorithm.  
All experimental data were obtained from the monitoring terminal of the notebook computer and the Ethernet-based suspension monitoring network. The data sampling rate was 200 samples per second. The whole weight of the vehicle is 8 ton during experiment.  
The full-scale maglev train consists of ten modules, ten air-springs and one cabin. The ten modules are distributed along the length direction of the vehicle symmetrically. For the bridge subsystem, the length of bridge is 18 m, and its mass per meter is about 2.4 ton. The field measurement indicates that its modal damping ratio is about 0.02. Considering the accuracy and reliability of the numerical model in Section 5.1 is close to the real maglev system, we expected the conclusion obtained by the numerical simulation to be validated by the field experiment.  
Figure 13 shows the results of self-excited vibration when performing field tests on a maintenance platform. The self-excited vibration appeared when \(t<1\) s. It can be found that the signals of acceleration, levitation gap and current fluctuate violently. The electromagnet vibration degraded the stability of the suspension control and ride comfort of vehicle.  
At \(t=1\) s, the proposed control strategy was activated. After a short regulation, the signal's fluctuation of the levitation gap and the acceleration of electromagnet were attenuated greatly.  
Figure 12: Field experiments on a full-scale maglev train at Tangshan maglev engineering experiment base.  
Figure 13: The experimental verification for vibration suppression method, which is activated during [1 3] and [5.5 8]: (**a**) the levitation gap; (**b**) the acceleration of electromagnet; (**c**) the magnetic flux; and (**d**) the switch signal.  
At \(t=3\) s, the control scheme was switched to the traditional cascaded-controller, the self-excited vibration aroused gradually. At \(t=5.5\) s, the control scheme was switched to proposed control strategy again, and the resonance disappear once more.  
According to Figures 11 and 13, both the results of the numerical simulation and field experiment indicate that the proposed control scheme is capable of weakening the amplitude of the self-excited vibration to zero in two seconds.  
At the same time, we also find that the experimental signals are much more irregular when compared with the signals obtained by the numerical simulation, which mainly results from the high-frequency noise from the eddy-current sensors and the inconsistent between the adjacent levitation units.