Numerical Analysis On Non-linear Characteristics Of Air Spring System Of High-speed Maglev Vehicle And Its Dynamic Response Negotiating The Vertical Curves

Air spring suspension system has advantages of large vertical flexibility,adjustable stiffness and damping,constant suspension height and excellent performance of high frequency vibration isolation,which widely used in the maglev second suspension systems.Taking a newly domestic designed air spring and high-speed maglev as the research object,the complex non-linear air spring models of high–speed maglev with considering the bellows,the level valve,the orifice,the auxiliary reservoirs,the emergency spring and the supplementary spaces were established by simulation software AMESim.The high-speed maglev dynamic models with considering the active controllers and based on a new type of levitation frame were set up by multibody dynamics software SIMPACK.Using the common interface FMI to exchange the simulation data between the air spring suspension system and the high-speed maglev system in real time.Based on the vertical non-linear air spring model,the non-linear characteristics of level valve which depend on the deadband and the delay time were simulated.The static stiffness,dynamic stiffness and dynamic damping were calculated.The non-linear relationships between the vertical characteristics of air spring and air spring's structural parameters were studied.Besides,the support mode of air spring suspension system of high-speed maglev and the detailed vertical curve setting methods and parameters selection were introduced.The dynamic responses of the maglev vehicle negotiating the small-radius vertical curved track with low speed were compared to the results of adopting linear air spring model.The results showed that expansion amount of linear air spring equivalent model is obviously less than the non-linear air spring.The non-linear air spring model shoud be applied when it comes to maglev vehicle dynamics simulation especially for the design of the air spring suspension.The effects of different bellow volumes,auxiliary reservoir volumes,orifice diameters and the level valve on vertical maglev vehicle stability at the speed of 300\400\500\600 km/h were calculated.The results indicated that sperling index decreases approximately linearly with the increase of the volume of the bellow.While the volume of auxiliary reservoirs is between 10 L and 50 L,the sperling index declines with the augment of the auxiliary reservoirs volumes.It has limit influence on sperling index when the auxiliary reservoirs volume is over 50 L.While the diameter of the orifice changes from 0 mm to 24 mm,the sperling index declines with the increasing of the orifice diameter.It has little influence on sperling index when the orifice diameter is over 24 mm.When the deadband of level valve is smaller than 10 mm,the vehicle sperling index decreases with increase of the deadband.When the deadband is higher than 10 mm,the sperling index is almost constant under the change of deadband as well as car-body acceleration is hardly altered with different delay time.It meaned that the delay time has no effect on sperling index when it only considers high-frequency excitation of vehicle system.