This paper reviews and summarizes Maglev train technologies from an electrical engineering point of view and assimilates the results of works over the past three decades carried out all over the world. Many researches and developments concerning the Maglev train have been accomplished; however, they are not always easy to understand. The purpose of this paper is to make the Maglev train technologies clear at a glance. Included are general understandings, technologies, and worldwide practical projects. Further research needs are also addressed.

Review of maglev train technologies

A device for controlling the relative position between a movable platen and a stator, with linear motions, for example in the 200 to 300 mm range, being provided in one or two of the degrees of freedom and precision control in the 10 nm range being provided in six degrees of freedom. Linear motion is provided by adjacent pairs of magnetic arrays and coil arrays, with the magnetic array of each pair preferably being mounted to the platen and the coil array to the stator. Both arrays have smooth mating surfaces spaced by a predetermined gap. Adjacent magnets of each magnetic array are oppositely poled and each coil array has multiple phases, the pitches of the two adjacent arrays preferably being substantially equal. The weight of the platen may be supported by the magnetic and coil arrays or separate magnets may be provided for this purpose.

Magnetic positioning device

Vibration isolation system combining zero-power magnetic suspension with springs

A new vibration isolation system using negative stiffness realized by active control technique is proposed in this paper. The serial connection of a normal spring and a suspension system with negative stiffness enables the isolation system to have low stiffness for vibration from the ground and high (theoretically infinite) stiffness against direct disturbance acting on the isolation table. A control method of realizing negative stiffness with a linear actuator is presented in an analytical form. The validity of this method is confirmed experimentally with an apparatus equipped with a voice coil motor. It is also confirmed experimentally that high stiffness against direct disturbance on the isolation table can be achieved in the proposed vibration isolation system.

Vibration Isolation System Using Negative Stiffness

This paper presents the development of an active 3-degree-of-freedom (DoF) vibration isolation system using zero-power magnetic suspension. The developed system is capable to suppress direct disturbances and isolate ground vibrations of the 3-DoF motions, associated with vertical translational and rotational modes. Two categories of control strategy for the actuators are proposed, i.e., local control and mode control. The latter method allows to overcome limitations of the poor performances for rotational modes exhibited by the former. A mathematical model of the system is derived and each DoF motion is treated separately for the control system. It is demonstrated analytically that the infinite stiffness to static direct disturbances can be generated and the resonance peak due to floor vibration can effectively be suppressed for the system. Moreover, the experiments have been carried out to measure the static and dynamic responses of the isolation table to direct disturbances, and transmissibility characteristic of the isolator from the floor. The results indicate good vibration isolation and attenuation performances, and show the efficacy of the developed isolator for industrialization

Development of a three-axis active vibration isolator using zero-power control

A power-saving electromagnetic suspension system has been developed in which electromagnets with permanent magnets are used to suspend the vehicle. The electromagnets are controlled to maintain air gap length so that the attractive force by the permanent magnet always balances the total weight of the vehicle and its loads, based on modern control theory. This technology realizes a significantly power-saving system in which the electromagnetic coil current required to keep a vehicle levitating was extremely small, ideally zero. The 8-kg weight test vehicle with 4-kg load could be levitated continuously over 8 h, without recharging the on-board 1300-mAh batteries. This technology realized a completely contact-free material transportation system when combined with a contact-free driving system using linear motors. The attractive force characteristics of a permanent magnet with control electromagnets and the newly developed electromagnet control system that can eliminate power collecting devices from the electromagnetic suspension system are described. >

A new MAGLEV system for magnetically levitated carrier system

An electromagnetic suspension system has been developed that cuts off electric power-collecting devices from a magnetically levitated vehicle. This system makes it possible to transport materials with no mechanical contact at all between the vehicle and ground facilities. A control system for linear induction motors used in the magnetically levitated carrier system is described. The system was developed to transport materials in an environment which must be kept free from even microscopic dust motes and trivial noise. The linear induction motor control method used for positioning a vehicle at the station is described along with several kinds of switches without any mechanical motion in the ground facilities. A supervisory control system for the magnetically levitated carrier system is also discussed. >

M. Morishita

Papers

A new MAGLEV system for magnetically levitated carrier system

A linear induction motor control system for magnetically levitated carrier system