As a new strategy for magnetic levitation envisioned in 1990s, the Inductrack system with permanent magnets aligned in Halbach arrays has been intensively studied and applied in many projects in different countries. To analyze such a system, most previous investigations have utilized steady-state Inductrack models, which commonly assume ideal sinusoidal magnetic field, fixed levitation gap, constant traveling speed, steady-state induced current and averaged magnetic force. However, due to the nonlinear, time-varying and motion-dependent electro-magneto-mechanical coupling in an Inductrack Maglev system, the dynamic behaviors are naturally complicated with transient responses, which in most cases can hardly be predicted with accuracy and fidelity by a steady-state Inductrack model.

Presented in this paper is a benchmark 2-DOF transient Inductrack model that is derived from the first laws of nature, without any assumption of the above-mentioned steady-state quantities. The model is built based on general transient response scenarios and with the consideration of practical issues, such as the finite dimensions of the on-board magnet arrays, the transient effects of the induced currents in the coils on the track, and the interaction forces between each magnet block and each track coil. It is found from thorough derivation that the Inductrack dynamic system is governed by a set of nonlinear integro-differential equations. As demonstrated by numerical simulations with the transient model, unstable vibrations in the levitation direction can occur, particularly when the vehicle is coasting at low traveling speeds. This phenomenon is accordance with the well-known “negative damping” effect discovered in traditional electrodynamic suspension systems for Maglev transportation.

To resolve the issue of instability, feedback control is implemented in the Inductrack Maglev system. In the development, active coils are wound around the on-board permanent magnets to generate an added and controllable source magnetic field. In this preliminary investigation, the proposed controller design process takes two main steps. First, a simple PID controller is set and tuned based on the basic lumped-mass dynamic system, which computes the required control force. Second, the nonlinear current-force correlation is obtained from a lookup table that is pre-calculated by a truncated version of the full transient Inductrack model, and this output current is served as the actual input of the entire Inductrack dynamic system. With the implemented feedback controller, the numerical examples show that the vertical oscillation of the vehicle can be effectively stabilized in a short time at various traveling speeds. Although only a 2-DOF transient model is used here, the modelling technique and the feedback control method developed in this work are potentially applicable to more complicated Inductrack Maglev systems.


Transient Vibration and Feedback Control of an Inductrack Maglev System

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

IMECE2020 - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.