The current research of autonomous vehicle motion control mainly focuses on trajectory tracking and velocity tracking. However, numerous studies deal with trajectory tracking and velocity tracking separately, and the ...The current research of autonomous vehicle motion control mainly focuses on trajectory tracking and velocity tracking. However, numerous studies deal with trajectory tracking and velocity tracking separately, and the yaw stability is seldom considered during trajectory tracking. In this research, a combination of the longitudinal–lateral control method with the yaw stability in the trajectory tracking for autonomous vehicles is studied. Based on the vehicle dynamics, considering the longitudinal and lateral motion of the vehicle, the velocity tracking and trajectory tracking problems can be attributed to the longitudinal and lateral control. A sliding mode variable structure control method is used in the longitudinal control. The total driving force is obtained from the velocity error in order to carry out velocity tracking. A linear time-varying model predictive control method is used in the lateral control to predict the required front wheel angle for trajectory tracking. Furthermore, a combined control framework is established to control the longitudinal and lateral motions and improve the reliability of the longitudinal and lateral direction control. On this basis, the driving force of a tire is allocated reasonably by using the direct yaw moment control, which ensures good yaw stability of the vehicle when tracking the trajectory. Simulation results indicate that the proposed control strategy is good in tracking the reference velocity and trajectory and improves the performance of the stability of the vehicle.展开更多
Metallised polypropylene film capacitors(MPPFCs)are widely used in power electronics and are generally degraded by elevated temperatures.This work aims to determine the relationships between the structural changes of ...Metallised polypropylene film capacitors(MPPFCs)are widely used in power electronics and are generally degraded by elevated temperatures.This work aims to determine the relationships between the structural changes of MPPFC and the microstructural variations of the PP film during the thermal ageing of MPPFC at 100℃ for 38 days.The capacitance of MPPFC has a slight decrease during thermal ageing.However,the breakdown voltage of the MPPFC decreases by 39.4%by the ageing.The partial discharge(PD)number of MPPFC increases linearly with ageing time.The tear-down analysis of the MPPFC reveals that the molecular structure of the PP film has not been altered but has led to molecular chain scission and the generation of some polar fragments/groups.Meanwhile,the relative permittivity of the PP films rises as the ageing time increases.Moreover,thermal ageing causes the conversion of aluminum to alumina in the metallised electrode,which is hydrophilic for polar groups and leads to an adhesion effect between the metallised electrodes and the PP film.Contact angle measurements prove that the surface hydrophilicity of the PP sample increased after thermal ageing.Therefore,the PD/breakdown voltage in the MPPFC increases/decreases due to the uneven adhesion of the metallised PP film.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.51575103,11672127,U1664258)Fundamental Research Funds for the Central Universities of China(Grant No.NT2018002)+1 种基金China Postdoctoral Science Foundation(Grant Nos.2017T100365,2016M601799)the Fundation of Graduate Innovation Center in NUAA(Grant No.k j20180207)
文摘The current research of autonomous vehicle motion control mainly focuses on trajectory tracking and velocity tracking. However, numerous studies deal with trajectory tracking and velocity tracking separately, and the yaw stability is seldom considered during trajectory tracking. In this research, a combination of the longitudinal–lateral control method with the yaw stability in the trajectory tracking for autonomous vehicles is studied. Based on the vehicle dynamics, considering the longitudinal and lateral motion of the vehicle, the velocity tracking and trajectory tracking problems can be attributed to the longitudinal and lateral control. A sliding mode variable structure control method is used in the longitudinal control. The total driving force is obtained from the velocity error in order to carry out velocity tracking. A linear time-varying model predictive control method is used in the lateral control to predict the required front wheel angle for trajectory tracking. Furthermore, a combined control framework is established to control the longitudinal and lateral motions and improve the reliability of the longitudinal and lateral direction control. On this basis, the driving force of a tire is allocated reasonably by using the direct yaw moment control, which ensures good yaw stability of the vehicle when tracking the trajectory. Simulation results indicate that the proposed control strategy is good in tracking the reference velocity and trajectory and improves the performance of the stability of the vehicle.
基金Major Research Plan of the National Natural Science Foundation of China,Grant/Award Number:92166206Fundamental Research Funds for the Central Universities,Grant/Award Number:2022CDJQY-014Ministry of Education of China through the 111 project,Grant/Award Number:BP0820005。
文摘Metallised polypropylene film capacitors(MPPFCs)are widely used in power electronics and are generally degraded by elevated temperatures.This work aims to determine the relationships between the structural changes of MPPFC and the microstructural variations of the PP film during the thermal ageing of MPPFC at 100℃ for 38 days.The capacitance of MPPFC has a slight decrease during thermal ageing.However,the breakdown voltage of the MPPFC decreases by 39.4%by the ageing.The partial discharge(PD)number of MPPFC increases linearly with ageing time.The tear-down analysis of the MPPFC reveals that the molecular structure of the PP film has not been altered but has led to molecular chain scission and the generation of some polar fragments/groups.Meanwhile,the relative permittivity of the PP films rises as the ageing time increases.Moreover,thermal ageing causes the conversion of aluminum to alumina in the metallised electrode,which is hydrophilic for polar groups and leads to an adhesion effect between the metallised electrodes and the PP film.Contact angle measurements prove that the surface hydrophilicity of the PP sample increased after thermal ageing.Therefore,the PD/breakdown voltage in the MPPFC increases/decreases due to the uneven adhesion of the metallised PP film.
