An active balancing method based on two flyback converters is proposed for series-connected battery pack. Balanced energy can be transferred between the whole battery and any single cell. The proposed topology reduces the number of energy storage components, the volume and the cost of the balancing system. And it has the characteristics of fast balancing speed and high balancing efficiency. Based on the topology, a dual-objective hybrid control strategy is proposed, which can reduce the highest voltage and boost the lowest voltage in the charging or discharging process of the cells in one sampling period, so as to improve the balancing speed. Simulation and experimental results show that the proposed method has a good balancing effect and can significantly improve the consistency of series battery pack. This work is potentially significant in terms of improved reliability of battery packs and savings of costs and lives in safety-critical applications.
Permanent magnet linear synchronous motors (PMLSM) has the advantages of high speed, high thrust density, high power density, high power factor and high reliability. In order to save permanent magnet (PM) materials and reduce magnetic leakage, a new type of PMLSM with Halbach consequent-pole (HCP) structure is presented, which has great potential for application to the ropeless elevator system. By using extensive finite element analysis (FEA), the electromagnetic properties of the proposed HCP-PMLSM, including magnetic field, back electromagnetic force (back-EMF), thrust force and cogging force are simulated and compared with the consequent pole PMLSM (CP-PMLSM) and surface-mounted pole PMLSM (SP-PMLSM). The comparison results show that the proposed HCP configuration can reduce substantial PM material and increase the air-gap magnetic field effectively. Then, the influence trend of HCP parameters such as pole thickness, pole width ratio, auxiliary PM width and magnetism angle, are studied and analyzed for evaluating the output performance in HCP-PMLSM. On this basis, Response surface method (RSM) is employed to optimize the HCP parameters with the target of maximum average thrust, minimum thrust ripple, and highest PM utilization. Furthermore, a double-sided pole shift method was proposed to significantly suppress the thrust fluctuation of HCP-PMLSM. Lastly, experimental results are provided to verify the investigation.
In this paper, the optimal linear filtering problem for linear discrete-time stochastic systems with random matrices, correlated noises and packet dropouts is studied where the random matrices are real and appear both in the the state and measurement equations. Using an equivalent transformation for random matrices and some results presented in this paper, an optimal linear filter for the system under consideration is developed. The developed optimal filter has a recursive pattern, and its computational complexity does not change with time. Number examples with simulation results are given to examine the performance of the developed optimal linear filter. INDEX TERMS Optimal linear filtering, discrete-time, networked control system, random matrix, packet dropout.
Two-degree-of-freedom motors are capable of producing linear, rotary, and helical motion, and thus have widespread applications in special industries. In this paper, a new concept-static coupling effect-is studied in the 2-degree-of-freedom direct drive induction motor (2DoFDDIM). The proposed approach is based on the image method and the 3D finite element method. The image method model is established to analyse its reasons and predict the main effects, which are then verified by the proposed 3D finite element static coupling model and experiments. The induced voltages and currents are produced in the static part and induced torque or force is obtained, even though the static part is not energized. It is concluded that the static coupling effect increases with the supply frequency and is influenced by the stator winding configuration. Thus, the existence of the static coupling effect is confirmed, which must be taken into account in future optimization and precise control of the 2DoFDDIM.Index Terms: induction motor, image method, static coupling effect, 3D finite element method, 2-degreeof-freedom.
This study proposes a hybrid feature convolutional neural network (HFCNN) model for the complete description of three-dimensional (3D) point cloud features. The HFCNN confers sensitivity to the local, global, and single-point properties simultaneously by a feature vector space expansion. Wherein, a pointwise convolutional network sub-model realises the extraction of the local features by using a pointwise convolutional operator to process point cloud data directly. To consider the global properties of the point cloud, a central-point radiation model is constructed as an input of the feature layer in a nonnetwork form. Meanwhile, the single-point behaviour is characterised by the solo point coordinate information in the network. Within the constructed solo-local-global feature space, i.e. the fusion of single point feature, local feature and global feature, the HFCNN model can handle 3D point cloud data with unstructured and unordered properties. The HFCNN can be directly applied to the point cloud classification and segmentation without the modification of the CNN structure and training procedure. The experimental results have shown the effectiveness of the proposed model in prediction of class labels and point-by-point labels.
Lithium battery has become the main power source of new energy vehicles due to its high energy density and low self-discharge rate. In the actual use of the series battery pack, due to the internal resistance and self-discharge rate of batteries and other factors, inconsistencies between the individual cells are unavoidable. Such inconsistencies will reduce the energy utilisation rate and service life of the battery pack, and even endanger the safety of the battery systems. To improve the consistency of the series battery pack, a novel balancing method based on the flyback converter is proposed in this study. The flyback converter with a simple and reliable structure is used to realise the energy transfer between the whole battery pack and any single cell. Compared with the traditional balancing topology, the topology proposed in this study reduces the number of components and the volume of the balancing system, and only needs one set of control signals on the converter primary side, thus reducing the control difficulty. The experimental results show the effectiveness of the novel balancing method. (a) Charging process of converter primary, (b) RCD buffer circuit absorbs the spike voltage, (c) Discharging process of converter secondary inductor
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