Research On Time-sharing Detecting Method Of Low Speed Maglev Train Gap Sensor

The low-speed maglev train is different from ordinary urban rail vehicles.It uses electromagnetic force to suspend the vehicle body above the track.It has many advantages such as strong climbing ability,small turning radius,low noise,stable operation,and small environmental pollution.It's an ideal type of urban rail transit.Suspension control system is the key to the maglev train.The gap sensor is an important part of the levitation control system.Research on it plays a positive role in the development of maglev technology.The gap sensor of the low-speed maglev train uses a way of three probes to detect the gap,there is mutual inductance between any two probes.When the sensor is calibrated,the magnetic coupling between the three probes has been calculated into the calibration data.The output of the three-way probe depends on each other.If one probe worked out,the magnetic field distribution around the other two-way probes has changed,the output of the two-way probe will also have detection error.Time-sharing detection method was adopted to make the output of the three probes independent from each other,and the detection error will also be eliminated.For the detection error,this paper analyzed how dose the eddy current gap sensor work.The equivalent circuit between detection coil and track was annlyzed.The equivalent inductance empirical formula of one and three coil was deduced under the eddy current field.Maxwell was used to establish the 3D model between the three probes and the track.The equivalent inductance of the detection coil is simulated and analyzed,and the detection error data was given under certain fault conditions.The data shows that the detection error caused by magnetic coupling is greater than the error that suspension system allowed.And then,the time-sharing detection method of the gap sensor was studied.Finally,the cooperative control scheme was selected as the time-sharing detection method of the gap sensor from four schemes.The input of excitation was controlled by program,the output of detection coil was controlled by switch,The simulation results show that the sampling frequency of the time-sharing detection method using the cooperative control scheme is high and impulse voltage is low,and the output of any coil is independent from each other.Finally,the experimental platform was built.The experimental results show that the time-sharing detection method of cooperative control can effectively eliminate the detection error caused by magnetic coupling.