Research On The Magnetic Force Of Cylindrical Permanent Magnet Electrodynamic Suspension Device

In the permanent magnet electrodynamic suspension system,a permanent magnet array moved above a conductive non-magnetic guideway.The time-changing magnetic field created in the air gap between the permanent magnet array and guideway induces eddy currents in the guideway which in turn interacts with the permanent magnet array field to produce suspension and drag forces that are required for maglev transportation.This system characterized by simple structure,stable system,and high reliability,is one of the most important maglev models.However,there are no levitation forces when the vehicle has no movement relative to the guideway.This dissertation proposes a new device based on a semicircular track and cylindrical permanent magnet Halbach array that enables a vehicle to statically levitate above a guideway.Verified the feasibility of the device by theoretical research,finite element analysis,and experimental method.First of all,in this dissertation,four cylindrical permanent magnet modules are in pairs and symmetrically arranged in the track along the left and right sides.On each side,two modules are installed on the output shafts of the rotating motor with double extensions.While the maglev vehicle operates in the static state,the geometric center of the output shaft,cylindrical permanent magnet module,and semicircular guide groove have coincided in aside.The two rotating motors,which are fixed on both sides of the suspension frame and rotate in opposite directions at the same speed,drive the permanent magnet Halbach rotors.Relative movement between the permanent magnet rotors and the guide rail creates an eddy current in the rail,thereby generating the electromagnetic force.The resultant force is shown as only the vertical levitation force when there is no lateral movement.Otherwise,it includes the lateral guiding force.The working characteristics of the device are given by analyzing the levitation force and guiding force.And the finite element model of this device is established,the magnetic field characteristics and structural relationship between a permanent magnet and conductor plate are analyzed.Next,the influence of the end effect of the magnetic field on the electromagnetic force was analyzed,a special relationship between the end effect of the magnetic field and the operating characteristics of this device was found.Considering the force characteristics of the vehicle when passing the horizontal curve line,the unique operation mode of this device was given.Then,in order to calculate the electromagnetic force created by this novel device,according to the electromagnetic field theory,we create a 2-D equivalent linear model of the cylindrical permanent magnet Halbach array,build differential equations(based on the linear model)for the magnetic vector potentials,and produce the expression of the electromagnetic force per unit length by solving the equation system.By integrating the electro-magnetic force per unit length with the arc direction of the inner semicircular track,the vertical electromagnetic force created by the novel device can be determined.Once more,based on the 2D analytical expression,an optimal levitation force to weight ratio calculation function was proposed.The optimized design of the Halbach magnet by a calculation function to obtain the structural parameters,which of the same weight of the permanent magnet can produce the maximum levitation force.And analyzed the permanent magnet geometric,rotating speed,the thickness of the plate,air gap and some other parameters on the suspension characters.These parameters affect the suspension performance such as the lift-to-weight ratio,the lift-to-power losses ratio,and the suspension stiffness.Finally,a cylindrical permanent magnet electrodynamic suspension device was built in the laboratory that can support a 60 kg item.It can test the performance indexes such as electromagnetic force and power consumption under different rotation speeds,different air gaps,and different rail structures.The experimental study proves that the proposed cylindrical permanent magnet electrodynamic suspension device can realize the levitation of the vehicle in a static state.