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.

Partial demagnetization fault (PDF) is a common problem for permanent magnet synchronous motor (PMSM). The PMSM usually operates under complex working conditions (dynamic speed and various load), leading to the difficulty in robust PDF diagnosis. Hence, how to reliably and accurately diagnose PDF under complex working conditions has become a key issue in ensuring its safe operation. To address this issue, a robust PDF diagnosis method for PMSM is proposed based on radial air-gap flux density in this article. First, the d -axis magnetic network model of PMSM is established to extract the fault feature from the radial air-gap flux density. Then, by subtracting the offline-calculated radial air-gap flux density of stator current excitation from the online measured value, the open-circuit radial air-gap flux density can be calculated. Next, the equiangular interval resampling method is used to obtain the open-circuit radial air-gap flux density with respect to rotor position angle. Finally, through analysis of open-circuit radial air-gap flux density in angular coordinates, not only PDF can be detected and the fault degree can be estimated, but also the demagnetized PM can be located under complex working conditions. Both the simulation and experimental results validate the effectiveness of the proposed PDF diagnosis method.

The dual-motor drive is common in many heavy-duty swinging arm servo systems. A well-tuned dual-motor drive can provide better stability and durability than the regular single motor servo. However, the backlash is usually unavoidable in the heavy transmission chains. In this article, the issues provoked by the backlash are resolved by a virtual average motor model and a simple anti-backlash torsion torque. The transient performance is guaranteed by the dual-motor synchronous drive, and the anti-backlash strategy is only enabled when the load is approaching the reference position. The challenge is that the motion system structure is transforming during this transition. The model predictive control combined with the extended state observer is applied to get adaptive in this scenario. The expected effect is that the servo can track the desired position with high precision and high response. The scheme is comprehensively validated and evaluated in an experimental servo setup with a dual-motor drive.

The stator-PM motor has an advantage with its simple and firm rotor, which is suitable when being applied to automotive applications. This paper proposes a novel structure for a variable reluctance (VR) resolver by using the concept of the stator-PM. This novel VR resolver shares a similar operation principle with the conventional VR resolver by injecting a 10 kHz excitation signal at low-speeds. Alternatively, at higher speeds, the stator-PM can produce motional back-EMF to support position measurement without the need for electrical excitation. The motional back-EMF can also reduce decoding computation. In addition, higher frequency signal excitation is not required for position measurement at higher speeds. This feature is beneficial for extremely high-speed motor applications. As a sensor, an inexpensive and low-amount ferrite magnet is used in the prototype to satisfy the low-cost requirements of the automotive industry.

Magnetic equivalent circuit (MEC) modeling is a challenging work to machines with novel structures, although it is an effective tool in the design process. The parameterized dynamic MEC modeling method is developed in this paper for the analysis of a novel rotor-segmented axial-field switched reluctance machine (RS-AFSRM). The ``parameterization'' is the feature leading the general MEC models in each interval of the rotor position, and the ``dynamic'' characteristic depends on the change of the flux patterns in the air region with the rotor displacement. By the proposed MEC model, the RS-AFSRM is analyzed on the smooth transition with efficient computation. The results obtained through the developed MEC models are verified by both the static and motion-coupled analyses.

High-resistance connection (HRC) is a common electrical fault for the electric machine drive system. This fault can lead to the increased power loss and heat, thus possibly causing the damage of the electric machine drive system due to the excessive temperature. Hence, this paper firstly proposes a vector control strategy of the surface-mounted permanent magnet synchronous machine (PMSM) drive system with the HRC fault to minimize the copper loss. The mathematical model of the PMSM with the HRC is presented in abc stationary frame. The function relationship between the copper loss and the direct axis current, quadrature axis current, stator resistance and the additional resistance due to the HRC is established and analyzed. The expression of the direct axis current which minimizes the copper loss is deduced under the condition of the HRC in one phase and two phases. Consequently, the proposed vector control strategy for the surface-mounted PMSM driving system is achieved. Both the simulation and experimental results show that the proposed method not only preserves the performance of the conventional vector control method, but also can effectively reduce the copper loss, thus protecting the PMSM from the damage due to the increased temperature possibly caused by the HRC fault.