This paper presents a high-precision transfer system of time and RF frequency via the fiber optic link based on secure encryption. On the basis of the two-way time transfer of optical fiber, a security strategy composed of an SM2 encryption algorithm is introduced, which can resist the security risk of time information being tampered with. The experimental results show that the developed picosecond-precision fiber-optic time transfer equipment can ensure high stability while realizing the encryption function. Time synchronization stability in terms of time deviation (TDEV) of 1 PPS can reach around 10.7 ps at 1 s and 7.1 ps at 10 s averaging time. The stability of the 10 MHz frequency can reach around 4.7 × 10−12 at 1 s and 1.1 × 10−12 at 10 s averaging time. There is no significant difference in time transfer accuracy, compared with unencrypted conditions. Furthermore, this paper realizes a ring time transfer network via a 150 km fiber-optic link with three nodes using three devices. The TDEV of 1PPS can reach around 20.8 ps at 1s averaging time. This paper provides a reference to establish a high-precision, safe, and stable time synchronization fiber network in the future.
Abstract.As the great differences of the electric energy consumption are generated when electric vehicle (EV) accelerates in different ways, this research studies on the difference of energy consumption per distance when accelerating in a multiacceleration way and single-acceleration way, on the basis of the theory research, an EV is taken as the research object and the energy consumption per kilometre is used as the objective function, an optimization design method for the EV acceleration way is presented. The optimization method is used to optimize the acceleration curve of the NEDC drive cycle and the optimum acceleration curve is obtained. In order to verify the energy saving effect of the optimum acceleration curve, the EV test of optimum curve is conducted. The experiment results show that compared with the NEDC curve, the energy consumption per kilometre of the No.1-5 optimum curve is reduced by 14.6%, 13.5%, 6.2%, 6.7% and 1.9% respectively.
IntroductionRecent study shows that the short driving range of EV is one of the essential factors that hinder its popularization [1], while its energy consumption during the acceleration process has a significant impact on its driving range. According to the theory of EV [2], when the vehicle parameters and road conditions are unchanging, the energy consumption of EV during the accelerating process mainly depends on its speed and acceleration. Therefore, it is necessary to find out the relationship between the speed and acceleration of EV and the its electric energy consumption in different acceleration processes, thereby providing a foundation for designing an energy-saving acceleration curve for EV. Relevant scholars have done a lot of researches in this field. For example, WU X[3] and ZHANG R [4] analyzed the relationship between the output power of battery pack and the speed and acceleration of EV based on the experimental data which was obtained through the vehicle experiment in urban areas and expressways; HUANG [5] and PAN[6] studied the changes of the energy consumption of EV when it accelerated with a few constant accelerations, the results showed that the energy consumption increased with values of acceleration increasing. The influence on energy consumption of EV while taking different accelerating curves which represented different driver behavior was also researched by some scholars [7][8][9]. The results showed that the acceleration curve with lower demand for speed and smooth changes on acceleration consumed less energy. In summary, most of the relevant literatures analyzed the influence on energy consumption when EV accelerated with different single-acceleration curve. However, few literatures studied the effects on energy consumption with multi-acceleration curve and the optimal design method of multi-acceleration curve for EV, therefore, it is difficult to
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