Hybrid Electric Vehicles (HEVs) have been proven to be a promising solution to environmental pollution and fuel savings. The benefit of the solution is generally realized as the amount of fuel consumption saved, which by itself represents a challenge to develop the right energy management strategies (EMSs) for HEVs. Moreover, meeting the design requirements are essential for optimal power distribution at the price of conflicting objectives. To this end, a significant number of EMSs have been proposed in the literature, which require a categorization method to better classify the design and control contributions, with an emphasis on fuel economy, providing power demand, and real-time applicability. The presented review targets two main headlines: (a) offline EMSs wherein global optimization-based EMSs and rule-based EMSs are presented; and (b) online EMSs, under which instantaneous optimization-based EMSs, predictive EMSs, and learning-based EMSs are put forward. Numerous methods are introduced, given the main focus on the presented scheme, and the basic principle of each approach is elaborated and compared along with its advantages and disadvantages in all aspects. In this sequel, a comprehensive literature review is provided. Finally, research gaps requiring more attention are identified and future important trends are discussed from different perspectives. The main contributions of this work are twofold. Firstly, state-of-the-art methods are introduced under a unified framework for the first time, with an extensive overview of existing EMSs for HEVs. Secondly, this paper aims to guide researchers and scholars to better choose the right EMS method to fill in the gaps for the development of future-generation HEVs.

No abstract

SiC/SiC was processed by high repetition frequency femtosecond laser with a wavelength of 1030 nm. The experimental results were analyzed based on the finite element simulation. In the femtosecond laser ablation experiment of SiC/SiC, the processing morphologies under different laser power, repetition frequency, scanning times and scanning velocity were compared. It was found that surface oxidation is an obvious defect in the high-frequency femtosecond laser processing of SiC/SiC, which needs to be controlled. The oxidation phenomenon became more and more obvious with the increased of laser power, repetition frequency and scanning times, while it decreased with the increased of scanning velocity. The parameters of material and laser processing were input into the heat transfer module of the finite element simulation software. The simulation results could intuitively show the formation of different morphological features from the perspective of the temperature field. Finally, the surface oxidation of SiC/SiC was effectively controlled through rationally optimizing the laser processing parameters, and good morphology was obtained. The comparison between simulation and experimental results can help to understand the ablation mechanism of SiC/SiC by high-frequency femtosecond laser, and provide reference for the efficient and precise manufacture of CMC-SiC materials by pulsed laser.

Contact impedance has an important effect on micro electrical impedance tomography (EIT) sensors compared to conventional macro sensors. In the present work, a complex contact impedance effect ratio ξ is defined to quantitatively evaluate the effect of the contact impedance on the accuracy of the reconstructed images by micro EIT. Quality of the reconstructed image under various ξ is estimated by the phantom simulation to find the optimum algorithm. The generalized vector sampled pattern matching (GVSPM) method reveals the best image quality and the best tolerance to ξ. Moreover, the images of yeast cells sedimentary distribution in a multilayered microchannel are reconstructed by the GVSPM method under various mean magnitudes of contact impedance effect ratio |ξ|. The result shows that the best image quality that has the smallest voltage error U = 0.581 is achieved with measurement frequency f = 1 MHz and mean magnitude |ξ| = 26. In addition, the reconstructed images of cells distribution become improper while f < 10 kHz and mean value of |ξ| > 2400.

No abstract

Rotating machinery has extensive industrial applications, and rolling element bearing (REB) is one of the core parts. To distinguish the incipient fault of bearing before it steps into serious failure is the main task of condition monitoring and fault diagnosis technology which could guarantee the reliability and security of rotating machinery. The early defect occurring in the REB is too weak and manifests itself in heavy surrounding noise, thus leading to the inefficiency of the fault detection techniques. Aiming at the vibration signal purification and promoting the potential of defects detection, a new method is proposed in this paper based on the combination of singular value decomposition (SVD) technique and squared envelope spectrum (SES). The kurtosis of SES (KSES) is employed to select the optimal singular component (SC) obtained by applying SVD to vibration signal, which provides the information of the REB for fault diagnosis. Moreover, the rolling bearing accelerated life test with the bearing running from normal state to failure is adopted to evaluate the performance of the SVD-KSES, and results demonstrate the proposed approach can detect the incipient faults from vibration signal in the natural degradation process.

The oil film among meshing teeth is just like a spring-damping element, and it can dominate the friction and meshing characteristics of the gear pair and influence its dynamic performances further. Thus, this article focuses on a double-helical gear system and makes efforts to consider the effect of the oil film among meshing teeth more deeply, which can enhance the precision of dynamic analysis for the gear system. First, based on the elasto-hydrodynamic lubrication theory and “microtomy” method, the models of friction and meshing characteristics are developed including the friction state and spring-damping effect of the oil film among meshing teeth; then, the dynamic models of the double-helical gear system with the effect of the oil film among meshing teeth are established, and finally, the experiments are carried out to verify the value of the models developed in this article. According to the theoretical and experimental analyses, it can be seen that the dynamic model considering the effect of the oil film among the meshing teeth is more precise and practical, and the effect of the oil film should be considered in the dynamic analysis of the gear system, especially at the condition with heavy load or high speed.

No abstract