Vehicle Design

The design and optimisation of a permanent magnet-assisted synchronous reluctance (PMaSynR) traction machine is described to improve its energy efficiency over a selection of driving cycles, when installed on a four-wheel-drive electrically powered vehicle for urban use, with two on-board powertrains. The driving cycle-based optimisation is defined with the objective of minimising motor energy loss under strict size constraints, while maintaining the peak torque and restricting the torque ripple. The key design parameters that exert the most significant influence on the selected performance indicators are identified through a parametric sensitivity analysis. The optimisation brings a motor design that is characterised by an energy loss reduction of 8.2% over the WLTP Class 2 driving cycle and 11.7% over the NEDC and Artemis Urban driving cycles, at the price of a 4.7% peak torque reduction with respect to the baseline machine. Additional analysis, implemented outside the optimisation framework, revealed that different coil turn adjustments would reduce the energy loss along the considered driving cycles. However, under realistic size constraints, the optimal design solutions are the same.

In this paper an electro-mechanical levelling system based on wide band-gap power electronics is proposed. The system is currently under development. Therefore, this document aims at introducing the reasons behind the choice of an electro-mechanical actuator operating at high voltage. High-level simulation models for the different parts have been developed to study the system response and to guide the design and the optimization of the various components. Preliminary results extracted from the simulating model are also provided.

Poster prsented at the 13th IEEE International Conference and Exposition on Electrical and Power Engineering (EPEi 2024). 17-19 October 2024, Iaşi, Romania. 

This poster outlines a design methodology for axial flux permanent magnet synchronous machines (AFPMs) aimed at electric vehicle applications. A simplified analytical model for electromagnetic design is proposed, also the design choices related to machine topology: stator, and rotor structures. Three rotor configurations: SPM, flux-concentrating IPM, and V-shaped IPM are compared based on peak and continuous performance, magnetic attraction forces, and demagnetization risk. The findings provide insights into optimizing AFPM design for electric drivetrains.

This article explores the optimal or near-optimal design configuration of a three-level neutral-point-clamped traction inverter for electric vehicles based on switching-cell array devices. From the definition of a suitable design optimization problem taking into account efficiency, reliability, and simplicity, the optimal solution for the leg configuration and operation is obtained under different scenarios and operating conditions. It is concluded that, in each case, the main operating conditions may decisively influence the selected design.

Multi-Moby project, funded under H2020 n° 101006953, aims at developing technology for safe, efficient and affordable urban electric vehicles. The objective of the paper is to show the results achieved in relation to structural integrity and occupant protection in the first year of the project. In a first stage simulation tools have been used to optimise the vehicle structure crashworthiness at different crash configuration based on smart use of High Strength Steels focused to simplified and affordable manufacturing processes. Once the structural behaviour met requirements and expectations, the restraint system has been developed. After design optimisation, three vehicles have been prototyped to perform three crash tests, two of them frontal, corresponding to Regulation 137 and Regulation 94, and one lateral, corresponding to Regulation 95.

In this document the work carried out as part of the HEFT project with regards to the deveopment of an ultra-light motor design for segment A+B. The multi-layer rotor topology makes possible to reduce de usage of permanent magnet leading to an important saving in the rare earth elements. Wave winding techcnology allows to develop compact and efficient stator. End winding length is reduced and high frequency losses are reduced in the copper. Involving all these techonologies a high power density motor is developed.
In this document the following issues will be covered:
1. Design Process (Design Methodology and Procedure to motor performances evaluation).
2. Preliminary sizing of the motor.
3. Optimization of the rotor
4. Continuous service evaluation.
5. Final performances evaluation and KPIs computation.

This paper presents a fast and accurate state-space model for synchronous machines taking into consideration the machine geometry, material non-linearities and core losses. The model is first constructed by storing the solutions of multiple static finite element (FE) simulations into lookup-tables (LUTs) to express the stator flux linkages as functions of the state variables, i.e., the winding currents and the rotor position. Different approaches are discussed to include the core loss into the model. A novel approach is presented for constructing a pre-computed LUT for the core loss as a function of the state variables and their time derivatives so that the loss can be directly interpolated when time-stepping the state-space model. The Simulink implementation of the proposed core-loss model shows a good match with time-stepping FE results with a 120-fold speedup in computation. In addition, comparison against calorimetric loss measurements for a 150-kVA machine operating under both sinusoidal and pulse-width modulated voltage supplies is presented to validate the model accuracy.

As the growth in electric vehicle (EV) chargers continues to push research towards compact and efficient power converters, high-frequency magnetic designs become pivotal. However, they introduce new challenges related to excessive magnetic losses and adverse parasitic components. Using planar transformers with PCB windings can address these by offering good heat dissipation, low losses, and controlled parasitics. Furthermore, interleaved winding configurations can circumvent traditional design trade-offs. Therefore, this paper presents a planar transformer design using PCB windings with novel interleaving and design aspects to minimise the losses and parasitic components of the high-frequency transformer. It aims to achieve an optimal balance between the trade-offs whilst ensuring compatibility with the target converter’s requirements and cooling system. The proposed anti-symmetrical interleaving achieves a drastic reduction of factor 8.6 in interwinding capacitance compared to conventional full-interleaving combined with low winding losses. The paper provides extensive comparison studies of different interleaving types, supported by thorough finite element simulations. The resulting design approach is applied to a 4 kW isolated dc-dc converter for level-1 EV charging. Finally, different prototypes are built and extensively characterised and validated for implementation in the EV charger. The resulting transformer features a gravimetric and volumetric power density of 15.1 kW/kg and 76.4 kW/l, respectively

Multi-Moby is an ambitious project aiming at quickly finalising the results of a cluster of ongoing and past European projects, addressing the development of technologies for safe, efficient and affordable urban electric vehicles (EVs). This paper presents the developments that have been implemented in the first half of Multi-Moby, which deals with low-cost M1 and N1 EVs, to be manufactured via low-investment and lean processes and plants. The Multi-Moby EVs have excellent passive safety characteristics, enhanced by pre-emptive active safety controllers. The vehicles can be coupled with efficient 100 V or 48 V powertrains. Fast charging is enabled by the integrated design of hybrid supercapacitor-battery cells and wall box chargers. The project will also consider low-cost automated driving solutions, with focus on gimbal-based camera systems for environmental sensing and detection.

Traction inverters play a crucial role in the growing industry of electric vehicles. On the one hand, the traction inverter design is quite challenging and needs to pursue key design goals including high efficiency, high reliability, high power density, and low weight and cost. On the other hand, a modular and scalable design methodology to cover a wide range of vehicles is highly desirable. This article explores the optimal or near-optimal design configuration of the multilevel neutral-point-clamped legs of traction inverters for three use cases: an electric motorcycle, an electric passenger car, and an electric truck. The design is based on the use of an array of switching cells. The optimal configuration and operation of the switching cells are obtained through a weighted objective function in terms of efficiency, reliability, and simplicity. The design optimization results illustrate the modularity, scalability, and suitability of the used design approach, where a single module fits all applications, and the available degrees of freedom enable the adaptation of the design to the application and operating conditions, to maximize its efficiency and reliability.