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Liu, Zhihong
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A New Flux Weakening Control Strategy for IPMSM (Interior Permanent Magnet Synchronous Machine) in Automotive Applications

CATARC-Zhihong Liu, Lei Zhang, Denggao Huang, Erxi Liu, Zhongwen Zhu, Xu Wang
  • Technical Paper
  • 2020-01-0466
To be published on 2020-04-14 by SAE International in United States
As one of the core components of electric vehicles(EV), the drive motor system has a significant impact on the EV operation performance. The interior permanent magnet synchronous motor (IPMSM) has a wide range of applications in EV, due to its high efficiency, high power density, high torque current and wide speed range. In the field of EV, motor control system is required to have a high operating range. IPMSM operates at constant torque mode below rated speed and constant power mode above rated speed. The back electromotive force(Back-EMF) generated by the rotor in the constant power mode causes the inverter output voltage to saturate. Therefore, it is necessary to ensure that the controller is still operating in the linear region by applying a flux weakening(FW) current to the stator.This paper propose an optimal FW path control strategy based on a state space consisting of a direct-axis current and a cross-axis current, bounded by maximum torque per ampere (MTPA) curve, maximum current curve, and maximum torque per voltage (MTPV) curve. The approach is founded on the…
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SOC Estimation Based on an Adaptive Mixed Algorithm

CATARC-Denggao Huang, Zhongwen Zhu, Zhihong Liu, Xu Wang, Cheng Li
Chang’an University-Runqin Liu
  • Technical Paper
  • 2020-01-1183
To be published on 2020-04-14 by SAE International in United States
SOC (State of charge) plays an important role in vehicle energy management, utilization of battery pack capacity, battery protection. Model based SOC estimation algorithm is widely regarded as an efficient computing method, but battery model accuracy and measuring noise variance will greatly affect the estimation result. This paper proposed an adaptive mixed estimation algorithm. In the algorithm, the recursive least squares algorithm was used to identify the battery parameters online with a second-order equivalent circuit model, and an adaptive unscented Kalman method was applied to estimate battery SOC. In order to verify the effect of the proposed algorithm, the experimental data of a lithium battery pack was applied to build a simulation model. The results show that the proposed joint algorithm has higher estimation accuracy and minimum root mean square error than other three algorithms.
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Theoretical and Experimental Investigation on Power Loss of Vehicle Transmission Synchronizers with Spray Lubrication

SAE International Journal of Advances and Current Practices in Mobility

TU Darmstadt-Zhihong Liu, Ye Shen, Stephan Rinderknecht
  • Journal Article
  • 2019-01-0028
Published 2019-01-15 by SAE International in United States
Besides optimal engine systems, high-efficiency vehicle transmissions are generally also required to improve fuel economy in automotive applications. For the energy loss analysis in transmissions, most research focused on the major mechanical components, such as gears, bearings and seals, while the other mechanical losses, like synchronizer losses, were usually not considered. With increasing number of synchronizers in modern transmissions, a recent study indicates that the power loss analysis of synchronizers should also be developed and appended for a more accurate investigation on overall power losses in transmissions. The function of synchronizer is to equalize the different rotational speeds of shafts and gear wheels by frictional torques, for which the synchronizer must be cooled and lubricated in order to enhance the service life. With the supplement of lubricants, fluid friction is generated due to the differential speed, when the synchronizer is in neutral position. This fluid friction can be principally regarded as load-independent synchronizer power loss. In this paper, fluid states and fluid dynamics in synchronizers with spray lubrication are analyzed analogously to multiple-plate clutches. Based…
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Modelling of Power Losses of Transmission Synchronizers in Neutral Position

IMS,Technische Universität Darmstadt-Ye Shen, Zhihong Liu
TU Darmstadt-Stephan Rinderknecht
Published 2018-04-03 by SAE International in United States
Developing an energy-efficient powertrain system is a solution for environment-friendly vehicles. Furthermore, it also enhances the performance of vehicles. In powertrain system, transmission plays an important role in terms of vehicle dynamic performance and energy consumption. Therefore, a lot of researches have been conducted on modelling power losses inside the transmission. Basically, the power losses in transmission consist of bearing losses, drag torque losses on gear blank that is immersed in the oil and gear mesh losses due to the sliding frictional force on gear flank. According to some experiments in the latest literatures, power losses of synchronizers cannot be neglected, when its shift sleeve is in neutral position. Principally, power losses of synchronizers in neutral position mainly come from load independent drag torque. The drag torque is generated by the shear torque of lubrication in the gap (or gaps) between synchronizer ring and synchronizer cone, which are rotating at different speed. In this paper, a drag torque model of synchronizer units in neutral position is built up based on mechanism of tribology lubrication. Several…
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New Apparatus and Method for Forming Tailor Welded Blanks

Northwestern University-Brad Kinsey, Zhihong Liu, Jian Cao
Published 1999-03-01 by SAE International in United States
Tailor welded blanks offer a unique opportunity to reduce manufacturing costs, decrease vehicle weight, and improve the quality of stampings through the consolidation of multiple formed, then welded, parts into a single stamping. However, tearing near the weld line often occurs in this type of blank when formed with a traditional deep drawing process. Therefore, some adaptation to the existing sheet metal forming process must be developed in order to reap the numerous benefits available from tailor welded blanks. In this paper, numerical simulation are presented for a newly contrived tailor welded blank forming process where several hydraulic mechanisms apply distinct clamping forces along the weld line during forming. Excellent results demonstrate the effectiveness of the proposed method.
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