Abstract:The paper presents a number of advanced solutions on electric machines and machine-based systems for the powertrain of electric vehicles (EVs). Two types of systems are considered, namely the drive systems designated to the EV propulsion and the power split devices utilized in the popular series-parallel hybrid electric vehicle architecture. After reviewing the main requirements for the electric drive systems, the paper illustrates advanced electric machine topologies, including a stator permanent magnet (stator-PM) motor, a hybrid-excitation motor, a flux memory motor and a redundant motor structure. Then, it illustrates advanced electric drive systems, such as the magnetic-geared in-wheel drive and the integrated starter generator (ISG). Finally, three machine-based implementations of the power split devices are expounded, built up around the dual-rotor PM machine, the dual-stator PM brushless machine and the magnetic-geared dual-rotor machine. As a conclusion, the development trends in the field of electric machines and machine-based systems for EVs are summarized.

The magnetostrictive strain-applied field curve typical of giant magnetostrictive materials is nonlinear and it is affected notably by prestress and temperature. A constitutive model to describe these properties is suggested in this paper. The model considered here is built on the Gibbs free energy function G(σij,Mk,T). Thermodynamic relations are used to obtain the constitutive expressions. Results based on the model show that the nonlinear property of magnetostrictive strain, the magnetization, and Young’s modulus under different prestress and temperature are in excellent agreement with experimental data. Moreover, the proposed model is convenient to be used in engineering applications since the parameters referred to the model can all be easily determined by experiments.

 -Magnetic-geared dual-rotor motor (MGDRM) is receiving increasing attention due to its advantages as a kind of pure electrical power split device for the series-parallel hybrid powertrain. This paper performs a systematic study on the analysis and control model of the complementary MGDRM. The principle of the complementary MGDRM is illustrated in detail. The torque production and flux-weakening ability of the complementary MGDRM are analyzed by the analytical method and a revised 2D FEA method. The field-oriented-control (FOC) method for the MGDRM is firstly realized in this paper. On the basis of the FOC model, the torque production and flux-weakening control in a wide speed range can be implemented. The static and dynamic performances of the MGDRM are analyzed based on the FEA and simulation models. The experiments on a prototype of the complementary MGDRM are carried out to validate the study.Index Terms-Magnetic-geared dual-rotor motor, permanent magnet motor, power split device, hybrid electric vehicle, field-oriented-control, complementary structure.

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 -The magnetic-geared dual-rotor motor (MGDRM) has been proposed as a power split device (PSD) for several years, but there is not an evaluation work for a MGDRM in a real hybrid powertrain so far. As a pilot demo, a MGDRM-based hybrid powertrain with a real engine is built and tested in a real hybrid test bench. The closed-loop speed control is developed for the MGDRM, with which two pragmatic functions of the hybrid powertrain are realized by the MGDRM: Firstly, the engine can be started by the MGDRM outer rotor no matter the vehicle is parking or travelling. Secondly, the torque coordination function of the MGDRM can help the engine to stabilize at a fixed work situation. This feature is the basement to adjust the operation and efficiency of engine. The power conversion efficiency map of the MGDRM is tested, based on which, the performance of the power split in different operating situations can be evaluated.

Terfenol-D rods, as a kind of giant magnetostrictive materials, are often used as active elements of device for antivibration application due to its superior material properties. Their magneto-mechanical responses exhibited in many experiments are nonlinear and coupled. In order to have a good understanding on their coupling characters for accurate control, the numerical simulation on dynamic behavior of a Terfenol-D rod is conducted based on a nonlinear and coupling constitutive model proposed in this paper. The results show that the constitutive model can effectively describe some intrinsic coupling phenomena observed by experiments involving the maximum magnetostrictive strain of a Terfenol-D rod changing with pre-stresses and the corresponding dynamic responses show that the frequency and the amplification of the Terfenol-D rod change with magnetic bias field and pre-stresses, which are also consistent with experimental data and cannot be captured by previous constitutive model.