LIMITLESS Research Project
Linear Induction Motor Drive for Traction and Levitation in Sustainable Hyperloop Systems
Academic Partner
Implementation Partner
Description
According to the Swiss strategy on mobility (“Avenir de la mobilité en Suisse, Cadre d’orientation 2040 du DETEC”), future transportation systems should be sustainable, efficient and based on light infrastructures. While this strategy is aligned with global trends in the transportation sector, it poses several technical challenges.
A promising solution are high-speed trains, notably based on Hyperloop technology. Composed of two main elements, an electric vehicle and a controlled environment confined infrastructure, the Hyperloop has the potential to disrupt intra-continental travels, while being sustainable at the same time. While high-speed solutions, such as Maglev, exist, the cost of their infrastructure is prohibitive as it requires an active and sophisticated rail.
Swisspod’s efforts focus on flipping the Maglev concept by integrating the energy reservoir in the vehicle propelled by an optimally-designed Linear Induction Motor (LIM) that makes the infrastructure passive. The major limitation of an energy-autonomous vehicle is its range. Since current battery energy densities cap at a few hundreds of Wh/kg, the autonomy is limited by mass constraints and the efficiency of LIMs. The LIM is a good candidate for high-speed travel when compared to its rotating equivalent.
However, current LIM solutions are known to be less energy efficient and have a lower power factor than rotating motors. Those limitations are associated with LIM’s finite length. Although nowadays Power Electronics (PE) make available efficient power converters, the use of conventional solutions faces fundamental challenges to reach high-speeds. The goal of this project is to overcome these limits.
Publications
2025
Authors:
Simone Rametti
Abstract:
To meet the Paris Agreement target of limiting global warming to 1.5°C, the International Energy Agency stresses the urgent need for rapid and transformative actions in all sectors. In 2022, transportation accounted for about 25% of global CO2 emissions, making decarbonization a critical priority. Among transportation modes, rail is the least carbon-intensive and is expanding significantly worldwide. High-speed rail, in particular, provides a viable alternative to short- and medium-haul flights, helping reduce aviation-related emissions. Innovative, sustainable transportation technologies are gaining interest as complementary solutions to rail expansion. They diversify land transportation and help reduce aviation-related emissions. Governments, especially the European Commission, have shown renewed commitment to advancing high-speed systems. This political interest has brought back interest in established but underutilized technologies like Hyperloop and maglev trains. The propulsion of maglev and Hyperloop systems is typically achieved using Linear Electrical Machines (LEMs), which are types of electrical machines that produce linear motion by generating a direct and contactless thrust force along a straight-line path. Among various types of LEMs, Linear Induction Motors (LIMs) stand out as promising candidates for maglev propulsion. LIMs correspond to the linear counterpart of conventional Rotating Induction Motors (RIMs) and may offer significant advantages compared to other LEMs, such as simpler construction, lower cost, and scalability. However, LIMs have traditionally been restricted to low-speed, short-haul applications due to their lower efficiency and gravimetric force densities than other LEMs. This thesis explores the potential of LIMs for medium- to high-speed maglev ground transportation systems, focusing on the integration of Propulsion and Levitation (PL) or Propulsion and Guidance (PG) functionalities into a single motor for an all-in-one maglev system. The core of the thesis is the development of a highly accurate and computationally efficient analytical model of LIMs that allows for the calculation of motor electromagnetic fields, forces, and efficiency. The proposed analytical model has been validated through comparisons with Finite Element Analysis (FEA) simulations and measurements from a custom-made experimental platform, demonstrating excellent accuracy and superior computational efficiency compared to FEA models. The proposed analytical model is utilized in the thesis to enhance the performance of Single-Sided LIMs (SLIMs), focusing particularly on increasing their gravimetric force densities, and to demonstrate the potential of SLIMs for a MHS maglev system with PL or PG functionalities integrated into the same motor. The thesis also proposes an optimization framework for the design of SLIMs, in which the developed analytical model and the performance enhancement techniques mentioned above have been combined into a multiobjective optimization problem. The objective is to maximize the Levitation-to-Weight Ratio (LWR) and the efficiency of SLIMs for a reduced-scale Hyperloop prototype operated at the EPFL Hyperloop test infrastructure. Finally, a control strategy is proposed to achieve a decoupled, simultaneous, and electromagnetic drag-less control of PL in SLIMs, thereby unlocking their potential to combine these functionalities into a single motor.
Published in: EPFL
Date of publication: August 4, 2025
Authors:
Simone Rametti;
Lucien Pierrejean;
André Hodder;
Mario Paolone
Abstract:
Thanks to the rapid growth of multiphase drives (MPDs), multiphase (MP) rotating electrical machines have gained popularity in the scientific community, demonstrating several advantages compared to traditional three-phase ones. Although MP rotating machines have been extensively studied in the literature, little research has been carried out on MP linear electrical machines and their application in the transportation sector. In this context, this article proposes a highly accurate and computationally efficient analytical model of MP single-sided linear induction motors (SLIMs) validated through comparison with finite-element analysis (FEA) simulations over a large interval of operational speeds (i.e.,
0 m/s < v < 150m/s). The proposed model, obtained by extending the one published in previous works by the authors, is used to analyze the performance of different MP SLIMs in terms of forces (i.e., thrust and normal force) and efficiency. A comparison with a three-phase SLIM is presented too. Furthermore, the effect of an iron appendix installed at the rear of the motor, which has been shown to increase the levitation force of SLIMs at high speed, has been added to the presented analysis. The results of the analysis demonstrate that an MP supply greatly affects the forces developed by the SLIMs and represents a solution to integrate propulsion and levitation (PL) functionalities into a single LIM for magnetic levitation (maglev) vehicles.
Published in: IEEE Transactions on Magnetics
Date of publication: July 10, 2025
Authors:
Simone Rametti;
Lucien Pierrejean;
André Hodder;
Mario Paolone
Abstract:
Traditional magnetic levitation trains (maglev) generally use two or three separate systems to perform propulsion, levitation, and guidance (PLG) functionalities. Linear electromagnetic motors (LEMs) may be used for propulsion, electromagnetic suspension (EMS), or electrodynamic suspension (EDS) for levitation and guidance. Although considerable effort has been made to integrate these functionalities in a single LEM, a maglev with combined PLG is not yet available. This article proposes a solution to increase the levitation force of a single-sided linear induction motor (SLIM) at medium-to-high speed by adding an appendix of ferromagnetic material to its rear section. The appendix’s role is to conserve the magnetic flux density at the SLIM rear, which would otherwise be unexploited, and use it to generate additional levitation. The impact of the tail size on the levitation force has been modeled and added to an analytical model developed in previous works. The accuracy of the proposed model has been numerically and experimentally validated through f.e.m. and measurements from a custom-made test bench. A sensitivity analysis on the appendix length for a realistic-size SLIM is finally carried out, proving the effectiveness of the proposed solution and demonstrating the potential of SLIMs for combined PLG for medium-to-high-speed magnetic levitation vehicles.
Published in: IEEE Transactions on Transportation Electrification
Date of publication: January 15, 2025
2024
Authors:
Lucien Pierrejean;
Simone Rametti;
André Hodder;
Mario Paolone
Abstract:
Linear electromagnetic motors (LEMs) have been proposed, developed, and used to propel high-speed (i.e., speed >100 m/s) levitating vehicles. However, few real implementations have demonstrated the feasibility of these machines at such speeds. Furthermore, LEMs are expected to be enabling technologies for levitating vehicles traveling at near sonic speed, such as the hyperloop concept. This article presents a systematic review of modeling, design, and performance assessment of LEMs used (or proposed) for the propulsion of levitating high-speed vehicles. Among all the possibilities, those that have received the most attention since the 1960s, along with the first magnetic levitation train concepts, are discussed. Classified by operating principle and topology, the LEMs are compared in terms of design and performance via specific key performance indicators (KPIs). The performance of the various proposed LEMs is assessed on the basis of data available in the literature.
Published in: IEEE Transactions on Transportation Electrification
Date of publication: June 19, 2024
Authors:
Simone Rametti;
Lucien Pierrejean;
André Hodder;
Mario Paolone
Abstract:
This article describes a simultaneous and decoupled scheme for the control of levitation and propulsion forces of single-sided linear induction motors (SLIMs). The proposed control scheme utilizes a highly accurate SLIM analytical model to ensure the operation of the motor at the best efficiency point while achieving lift and thrust forces decoupling through a multi-frequency supply strategy adapted from the literature. The described control scheme has been implemented and validated in MATLAB Simulink.
Published in: 2024 IEEE International Conference on Electrical Systems for Aircraft, Railway, Ship Propulsion and Road Vehicles & International Transportation Electrification Conference (ESARS-ITEC)
Date of publication: November 26-29, 2024
Authors:
Simone Rametti;
Lucien Pierrejean;
André Hodder;
Mario Paolone
Abstract:
This article describes a field-based analytical model of single-sided linear induction motors (SLIMs) that explicitly and simultaneously considers the following effects: finite motor length, magnetomotive force mmf space harmonics, slot effect, edge effect, and tail effect. The derived closed-form solution of the system’s differential equations makes the model computationally more efficient than traditional finite element (f.e.m.) models, and therefore more suitable for SLIM design optimization processes. The computational performance and accuracy of the proposed analytical model are validated through numerical simulations (via COMSOL Multiphysics) and experimental measurements carried out through a dedicated test bench.
Published in: 2024 International Conference on Electrical Machines (ICEM)
Date of publication: September 01-04, 2024
Authors:
Simone Rametti;
Lucien Pierrejean;
André Hodder;
Mario Paolone
Abstract:
Literature on linear induction motors (LIMs) has proposed several approaches to model the behavior of such devices for different applications. In terms of accuracy and fidelity, field analysis-based models are the most relevant. Closed-form or numerical solutions can be derived, based on the complexity of the model and the underlying hypotheses. In terms of simplicity, equivalent circuit-based models (ECMs) are the most effective, since they can be easily integrated into optimization frameworks. To the best of our knowledge, the literature has not yet provided a computationally efficient LIM analytical model that considers the main characteristics of this type of motor altogether (i.e., finite motor length, magnetomotive force (mmf) space harmonics, slot effect, edge effect, and tail effect) and that is numerically and experimentally validated, especially at high speed (i.e., v = 100m/s). Within this context, this article proposes a field analysis-based pseudo-3-D model of LIMs that explicitly takes into account the above-mentioned effects. The derived closed-form solution makes the model computationally more effective than traditional f.e.m. models and, therefore, suitable to be coupled with optimization frameworks for optimal LIM design. The performance and accuracy of the proposed model are assessed through numerical simulations and experimental measurements, carried out by means of a dedicated test bench.
Published in: IEEE Transactions on Transportation Electrification
Date of publication: January 01, 2024