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

DOI:  10.5075/epfl-thesis-11350

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

DOI:  10.1109/TTE.2024.3416870

Authors: Denis Tudor

Abstract:
In the last decades, transportation demand growth has played a major role in the increase of global CO ₂ footprint. At the same time, a number of countries have scheduled measurable and substantial cutback of CO ₂ emissions by 2050. As the transportation sector has a significant carbon footprint, this process has triggered the need to develop new transportation alternatives. These can be split in two main categories: low-speed and high-speed transportation systems. While there are existing sustainable alternatives for low-speed (or medium-speed) transportation systems (i.e., electric vehicles, electric trains), the only high-speed transportation system that exists at this moment is the aviation. In terms of CO ₂, the emissions produced by the aviation sector are significant and, even though there are alternatives to aircrafts powered by fossil fuels (i.e., solar-based synthetic fuels or electric), they are technologically in their infancy.
Hyperloop could potentially represent a freight or passenger alternative to fossil-fuel powered aviation especially for intra-continental travels. The hyperloop comprises a network of capsules traveling at sub-sonic speed in a low-pressure constrained environment (i.e., a tube) embedding a set of rails for propulsion, levitation/suspension and guidance. The main advantages of a hyperloop system are associated to its energy efficiency and consequent sustainability gains produced by the large reduction of the drag aerodynamic losses and the adoption of a fully electric drivetrain.
One of the major challenges for the hyperloop is the construction of a radically new infrastructure involving extensive phases comprising feasibility studies, land expropriations, permits and civil constructions. Regarding the capsule design, the main challenge is conceiving and developing a solution that would eventually reduce the price of the infrastructure and leverage low-maintenance procedures. A major role here is played by the drivetrain system (i.e., propulsion, levitation and battery energy storage system).
Within this context, the thesis focuses on the development of various optimization frameworks to assess the optimal performance of the Hyperloop capsules propulsion with respect to their kinematic/propulsion models and the operation in the depressurized environment. Then, the thesis discusses how to optimally scale-down the hyperloop system in order to design reduced-scale mock-ups to be used in a fast-prototyping process of this new transportation system. The last part of the thesis illustrates an experimental testing facility under construction at the EPFL campus.

Published in: EPFL

Date of publication: January 18, 2023

DOI:  10.5075/epfl-thesis-9519

Authors: Denis Tudor; Tony Govoni; Malicia Leipold;  Mario Paolone

Abstract:
The thorough development of the hyperloop system does require the availability of reduced-scale models. They can be used for the fast prototyping of various components, as well as for studying critical phenomena that takes place in this peculiar transportation system without the need to develop complex and expensive full-scale setups. In this respect, in this paper, we present a process for the optimal assessment of the scaling factor; it is to be used for the development of a reduced-scale hyperloop model, starting from the knowledge of the technical characteristics of its full-scale counterpart. The objective of the proposed process is the minimisation of the difference between the normalized power profiles associated with the reduced-scale and full-scale models of a hyperloop capsule traveling along a pre-defined trajectory with a pre-determined speed profile. By considering the hyperloop full-scale model as a reference, we propose a set of equations that link the above-mentioned metric with the constraints dictated by the kinematics of the hyperloop capsule, the capsule’s battery-energy storage and propulsion systems, the capsule’s aerodynamics, and the operating environmental conditions. We then derive a closed-form expression for the assessment of the optimal scaling factor and eventually use it to study the scaled-down version of an application example of a realistic hyperloop system.

Published in: 2022 IEEE 25th International Conference on Intelligent Transportation Systems (ITSC)

Date of publication: October 08-12, 2022

DOI:  10.1109/ITSC55140.2022.9921742

Authors: Denis Tudor;  Mario Paolone

Abstract:
We present an operational-driven optimal-design framework of a Hyperloop system. The novelty of the proposed framework is in the problem formulation that links the operation of a network of Hyperloop capsules, the model of the Hyperloop infrastructure, and the model of the capsule’s propulsion and kinematics. The objective of the optimisation is to minimize the energy consumption of the whole Hyperloop system for different operational strategies. By considering a network of energy-autonomous capsules and various depressurization control strategies of the Hyperloop infrastructure, the constraints of the optimisation problem represent the capsule’s battery energy storage system response, the capsule’s propulsion system and its kinematic model linked with the model of the depressurization system of the Hyperloop infrastructure. Depending on the operational scheme and lengths of the trajectories, the proposed framework determines optimal operating pressures of the Hyperloop infrastructure between 1.5-80 mbar along with the maximum capsules cruising speeds. Furthermore, the proposed framework determines maximum operational power of the capsule’s propulsion system in the range between 1.7-5 MW with a minimum energy need of 25 Wh/passenger/km.

Published in: Transportation Engineering

Date of publication: September, 2021

DOI:  10.1016/j.treng.2021.100079

Authors: Denis Tudor;  Mario Paolone

Abstract:
In this article, we focus on the assessment of the optimal design of the propulsion system (PS) of an energy-autonomous Hyperloop capsule supplied by batteries. The novelty in this article is to propose a sizing method for this specific transportation system and answer the question whether the energy and power requirements of the Hyperloop propulsion are compatible with available power-electronics and battery technologies. By knowing the weight of a predetermined payload to be transported along predetermined trajectories, the proposed sizing method minimizes the total number of battery cells that supply the capsule’s propulsion and maximizes its performance. The constraints embed numerically tractable and discrete-time models of the main components of the electrical PS and the battery, along with a kinematic model of the capsule. Although the optimization problem is nonconvex due to the adopted discrete-time formulation, its constraints exhibit a good numerical tractability. After having determined multiple solutions, we identify the dominant ones by using specific metrics. These solutions identify PSs characterized by energy reservoirs with an energy capacity in the order of 0.5 MWh and a power rating below 6.25 MW and enable an energy consumption of 10-50 Wh/km/passenger depending on the length of the trajectory.

Published in: IEEE Transactions on Transportation Electrification

Date of publication: November 6, 2019

DOI:  10.1109/TTE.2019.2952075