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The traffic speed information of an urban road network is generally estimated using the widely available taxi GPS data. However, taxi usages are preponderantly restricted to areas with high population density, which results in limited spatial coverage of collected taxi GPS data. Moreover, the traffic speeds of taxies are not guaranteed to well represent the traffic speeds of other types of vehicles. In this study, we address these issues by introducing an infinite Gaussian mixture model to estimate traffic speed distribution. The variational inference method is employed to deal with the complicated parameter estimation problem. The proposed mixture model simultaneously combines taxi GPS data, bus GPS data, and mobile phone GPS data, which not only generates the mixed traffic-speed distribution of different types of vehicles but also improves the spatial coverage and the quality of traffic speed estimation. Surprisingly, we find that the incorporation of mobile phone GPS data can considerably improve the model’s ability to sense anomalous traffic conditions. Finally, the mixed traffic-speed distribution is validated using the license plate recognition data. [ABSTRACT FROM AUTHOR]

In this letter, a novel lookup table (LUT)-based direct torque control (DTC) strategy is proposed for dual-inverter fed open winding permanent magnet synchronous motor drives. Torque and flux linkage are regulated by tracking the reference voltage vector (VV) on the space VV plane according to a simplified LUT. The simplified LUT is established by dividing the space VV plane into 19 regions and each region corresponds to a basic VV. The optimal VV can be obtained by locating the corresponding region of the reference VV, which significantly decreases the complexity of LUT design and maintains the simplicity of the DTC strategy. A group of optimal switching states that minimize the transition times is selected. Meanwhile, the elimination of the hysteresis controller can further decrease the switching frequency. Experimental results show that the torque ripple, current harmonics, and switching frequency of the proposed strategy are reduced compared with the traditional DTC strategy. [ABSTRACT FROM AUTHOR]

This article proposes a dual two-vector-based model predictive flux control (DTV-MPFC) strategy for open winding permanent magnet synchronous motor drives with two isolated voltage source inverters (VSIs). In the MPFC strategy, the reference stator flux vector can be compensated to realize field-weakening (FW) operation by controlling the value of the cost function. However, the accuracy of the cost function based FW strategy is limited when the tracking error of the stator flux vector exists. In this article, a DTV-MPFC strategy is proposed to synthesize the reference flux increment vector precisely and the FW operation boundary is kept within the linear modulation region to enhance the FW operation performance. Each inverter applies two vectors during the control period and the switching frequency of the VSIs is minimized with the proposed strategy. When the dc-link voltages of the VSIs are unequal, the number of candidate flux increment vectors and the distribution of the space vector plane are different. A generalized vector selection and duration calculation scheme is proposed to realize the DTV-MPFC strategy in this case. Experimental studies are carried out to verify the validity and effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

This paper proposes a model predictive flux control (MPFC) strategy with cost function-based field weakening (FW) strategy for permanent magnet synchronous motor (PMSM). The stator flux vector is used as the control variable and the cost function of the proposed MPFC is configured in the form of flux increment, which can reflect the saturation degree of the inverter output. A novel space flux vector plane is introduced to explain the principle of optimal switching state selection in the proposed MPFC. The voltage and current limitations of the inverter in the high-speed region are analyzed in the flux plane to reveal the objective of FW compensation. The value of the cost function is controlled with a proportional integral controller in the proposed cost function-based FW strategy. Moreover, the reference flux vector is compensated with the output of the FW controller to enlarge the operation region of the stator flux vector. With the proposed FW strategy, the operation range of the PMSM is extended and the torque output in high-speed range is increased. Experimental studies are carried out to verify the validity and effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

A simplified model predictive control (S-MPC) for open-winding permanent magnet synchronous motor system fed by two isolated power sources is proposed in order to remove the complex tuning work of weighting factors and reduce the calculation burden in the conventional MPC. Control constraints torque and flux in the conventional MPC are converted into an equivalent flux vector for the purpose of eliminating the weighting factor in the cost function. Moreover, a novel prediction strategy and a fast voltage selection scheme are presented to reduce the system calculation burden. As a result, the optimal voltage is selected through only twice evaluations. Furthermore, a switching states distribution strategy is introduced to reduce the switching frequency of a dual inverter. Comparative experiments are conducted to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper proposes a hybrid pulse width modulation (PWM) based field weakening control strategy for a hybrid-inverter-driven open-winding (OW) permanent magnet synchronous motor (PMSM) system. The hybrid-inverter consists of two voltage source inverters, one is connected to a dc voltage source and named as main inverter (MI), and the other is connected to a floating capacitor and called compensation inverter (CI). A novel hybrid PWM technique is proposed for the hybrid-inverter, in which a double-vector-based PWM is applied to the MI to reduce the switching frequency, and the conventional space vector PWM is applied to the CI to compensate the reactive power. Furthermore, a field weakening (FW) control strategy based on the hybrid PWM technique is proposed to better utilize the dc-link voltage and extend the operation range of the OW-PMSM system. Simulation and experimental studies are carried out to verify the high efficiency and wide speed range of the proposed strategy. [ABSTRACT FROM PUBLISHER]