Research On Suspension Controller Without Air Gap Sensor

The medium-low speed maglev train plays an important role in urban rail transit with the advantages of strong climbing ability,small turning radius,small noise,safety and comfort,low cost of construction and maintenance,etc.The suspension controller is one of the core technologies of maglev train.The reliability and stability of suspension system depend on the reliability of the air gap sensor.At present,three air gap sensors are used together to improve the reliability of levitation and the problem of passing rail joints,which also brings about high cost.This paper studies the suspension controller without air gap sensor and explores the indirect identification technology of air gap through electromagnet inductance detection to achieve low cost and high reliability.The following studies are carried out:Firstly,control strategy of single electromagnet suspension system is studied,whose mathematical model is established.The suspension controller is designed by using the control scheme of the air gap outer loop current inner loop.The working principle of the maglev chopper is analyzed and the current loop compensation network is designed to quickly follow the current command.The air gap loop controller is designed based on the equilibrium point linearization and precise linearization methods respectively.The simulation proves that the exact linearization method has the advantage of being insensitive to the disturbance force.Then,the air gap identification scheme is studied and the idea of obtaining the air gap indirectly by detecting the change rate of the inductor current and obtaining the inductance of the electromagnet is proposed.The relationship curves between inductance and air gap are analyzed by finite element.Then the simulation of air gap identification and guidance conditions are performed based on Simulink,and the feasibility of air gap identification scheme is proved.Taking into account the actual parameters of the suspension bogie,the specific realization is studied.The subtractive base-off value and the high-multiplier circuit are designed to extract the current ripple to estimate the inductance and the current micropulse extraction problem is solved.Finally,design and experiment are carried out.The suspension controller based on ARM+FPGA is designed,including signal conditioning,digital filtering,suspension control,air gap identification and other modules.The suspension control and air gap identification experiments of single electromagnet suspension system are conducted on the suspension bogie of Tongji University.The stable suspension of single electromagnet and the identification of inductance and air gap are realized with the result that the accuracy of identification is within ±5% and the air gap and inductance curves are experimentally measured.Through the research of this paper,the suspension controller without air gap sensor can accurately identify the suspension air gap for suspension control,which is expected to be realized by engineering.