State Estimation of Drive-by-Wire Chassis Vehicle Based on Dual Unscented Particle Filter Algorithm

Accurate vehicle dynamic information plays an important role in vehicle driving safety.However,due to the characteristics of high mobility and multiple controllable degrees of freedom of drive-by-wire chassis vehicles,the current mature application of traditional vehicle state estimation algorithms can not meet the requirements of drive-by-wire chassis vehicle state estimation.This paper proposes a state estimation method for drive-by-wire chassis vehicle based on the dual unscented particle filter algorithm,which make full use of the known advantages of the four-wheel drive torque and steer angle parameters of the drive-by-wire chassis vehicle.In the dual unscented particle filter algorithm,two unscented particle filter transfer information to each other,observe the vehicle state information and the tire force parameter information of the four wheels respectively,which reduce the influence of parameter uncertainty and model parameter changes on the estimation accuracy during driving.The performance with the dual unscented particle filter algorithm,which is analyzed in terms of the time-average square error,is superior of the unscented Kalman filter algorithm.The effectiveness of the algorithm is further verified by driving simulator test.In this paper,a vehicle state estimator based on dual unscented particle filter algorithm was proposed for the first time to improve the estimation accuracy of vehicle parameters and states.

Picosecond Laser Surface Texturing of a Stavax Steel Substrate for Wettability Control

In this investigation,a picosecond laser was employed to fabricate surface textures on a Stavax steel substrate,which is a key material for mold fabrication in the manufacturing of various polymer products.Three main types of surface textures were fabricated on a Stavax steel substrate:periodic ripples,a two-scale hierarchical two-dimensional array of micro-bumps,and a micro-pits array with nanoripples.The wettability of the laser-textured Stavax steel surface was converted from its original hydrophilicity into hydrophobicity and even super-hydrophobicity after exposure to air.The results clearly show that this super-hydrophobicity is mainly due to the surface textures.The ultrafast laserinduced catalytic effect may play a secondary role in modifying the surface chemistry so as to lower the surface energy.The laser-induced surface textures on the metal mold substrates were then replicated onto polypropylene substrates via the polymer injection molding process.The surface wettability of the molded polypropylene was found to be changed from the original hydrophilicity to superhydrophobicity.This developed process holds the potential to improve the performance of fabricated plastic products in terms of wettability control and easy cleaning.

Influence of Component Size on the Corrosion Behavior of Ti6Al4V Alloy Fabricated by Electron Beam Powder Bed Fusion

The electrochemical behavior of Ti-6Al-4V with 1 mm and 16 mm thickness prepared by electron beam powder bed fusion(EB-PBF)was investigated in phosphate buffered saline.Electrochemical results showed that EB-PBF Ti-6Al-4V with a larger component size was more resistant to corrosion compared to the smaller component,because of less acicularαʹphase content and moreβphase content.As a non-equilibrium phase in the“high-energy state”,αʹphase has a greater susceptibility to corrode and reduces the corrosion resistance of the material,whileβphase improves corrosion resistance of titanium alloys.The results show that the phase composition has a more significant effect on the corrosion performance than the grain size.

多变量半自适应预测控制系统架构

针对模型因素引起的预测控制性能退化问题,本文提出一种多变量半自适应预测控制系统架构.该架构将传统的控制模式改变为测试模式,变传统的设定值控制为区间控制,从而实现了测试过程中输出变量的约束满足.所提出的半自适应预测控制体系架构能够在确保生产正常进行的前提下,实现过程的开环测试,提高测试效率,并通过极大化测试信号的幅值来确保测试过程的信噪比.进一步地,将该框架从约束预测控制扩展到双层结构预测控制,引入平衡系数实现经济效益与测试之间的平衡.本文提及的测试方法是一种在线开环测试,避免了闭环测试过程中测试输入信号与不可测噪声的相关性问题.仿真实例验证了该方法的有效性.

Femtosecond laser-induced surface wettability modification of polystyrene surface

In this paper, we demonstrated a simple method to create either a hydrophilic or hydrophobic surface. With femtosecond laser irradiation at different laser parameters, the water contact angle (WCA) on polystyrene’s surface can be modified to either 12.7° or 156.2° from its original WCA of 88.2°. With properly spaced micro-pits created, the surface became hydrophilic probably due to the spread of the water droplets into the micro-pits. While with properly spaced micro-grooves created, the surface became rough and more hydrophobic. We investigated the effect of laser parameters on WCAs and analyzed the laser-treated surface roughness, profiles and chemical bonds by surface profilometer, scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). For the laser-treated surface with low roughness, the polar (such as C—O, C=O, and O—C=O bonds) and non-polar (such as C—C or C—H bonds) groups were found to be responsible for the wettability changes. While for a rough surface, the surface roughness or the surface topography structure played a more significant role in the changes of the surface WCA. The mechanisms involved in the laser surface wettability modification process were discussed.

Understanding network travel time reliability with on-demand ride service data

Travel time reliability is of increasing importance for travelers, shippers, and transportation managers because traffic congestion has become worse in major urban areas in recent years. To better evaluate the urban network-wide travel time reliability, five indices based on the emerging on-demand ride service data are proposed:network free flow time rate(NFFTR), network travel time rate(NTTR), network planning time rate(NPTR), network buffer time rate(NBTR), and network buffer time rate index(NBTRI). These indices take into account the probability distribution of the travel time rate(i.e., travel time spent for the unit distance, in min/km) of each origindestination(OD) pair in the road network. We use realworld data extracted from DiDi-Chuxing, which is the largest on-demand ride service platform in China. For demonstrative purposes, the network-wide travel time reliability of Beijing is analyzed in detail from two dimensions of time and space. The results show that the road network is more unreliable in AM/PM peaks than other time periods, and the most reliable time period is the early morning. Additionally, we can find that the central region is more unreliable than other regions of the city based on the spatial analysis results. The proposed network travel time reliability indices provide insights for the comprehensive evaluation of the road network traffic dynamics and day-to-day travel time variations.

Laser sintering of Cu nanoparticles on PET polymer substrate for printed electronics at different wavelengths and process conditions

This study explores the feasibility of different laser systems to sinter screen-printed lines from nonconductive copper nanoparticles(Cu NPs)on polyethylene terephthalate polymer film.These materials are commonly used in manufacturing functional printed electronics for large-area applications.Here,optical and thermal characterization of the materials is conducted to identify suitable laser sources and process conditions.Direct diode(808 nm),Nd:YAG(1064 nm and second harmonic of 532 nm),and ytterbium fiber(1070 nm)lasers are explored.Optimal parameters for sintering the Cu NPs are identified for each laser system,which targets low resistivity and high processing speed.Finally,the quality of the sintered tracks is quantified,and the laser sintering mechanisms observed under different wavelengths are analyzed.Practical considerations are discussed to improve the laser sintering process of Cu NPs.