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DOI: 10.1186/s10033-019-0376-0

Study on Rollover Index and Stability for a Triaxle Bus

Zhilin Jin, Jingxuan Li, Yanjun Huang & Amir Khajepour 

Abstract: Vehicle rollover, and its resulting fatalities, is an actively researched topic especially for multi-axle vehicles in the field of vehicle dynamics and control. This paper first presents a new rollover index for a triaxle bus to accurately evaluate its rollover possibility and then discusses the influence laws of the vehicle rollover dynamics to explore the mechanism of its stability. First, a six degree of freedom rollover model of the triaxle bus is developed, including lateral, yaw, roll motion of the sprung mass of the front/rear axle, and roll motion of the unsprung mass of the front/rear axle. Next, some key parameters of the vehicle rollover model are identified. A new rollover index is deduced according to the basics of vehicle dynamics, to predict vehicle rollover risk for the triaxle bus, which is verified by TruckSim. Furthermore, the influence laws of vehicle rollover dynamics by vehicle parameters and road parameters are discussed based on the simulation results. More importantly, the results show that the new method of modeling can precisely describe the rollover dynamics of the studied bus, and the proposed new index can effectively evaluate the rollover possibility. Therefore, this study provides a theoretical basis to improve anti-rollover ability for triaxle buses.

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https://cjme.springeropen.com/articles/10.1186/s10033-019-0376-0

DOI: 10.1186/s10033-019-0378-y

Modeling and Configuration Design of Electromagnetic Actuation Coil for a Magnetically Controlled Microrobot

Xiaolong Jing & Weizhong Guo 

Abstract: Non-contact actuated microbeads have attracted a lot of attention in recent years because of its enormous potential in medical, biological, and industrial applications. Researchers have proposed a multitude of electromagnetic actuation (EMA) systems consisting of a variety of coil pairs. However, a unified method to design and optimize a coil pair according to technical specifications still does not exist. Initially, this paper presented the modeling of an untethered ferromagnetic particle actuated by externally applied magnetic field. Based on the models, a simple method of designing and optimizing the EMA coil pair according to technical specifications, was proposed. A loop-shaped coil pair generating uniform magnetic and gradient fields was chosen to demonstrate this method clearly and practically. The results of the optimization showed that the best distance to radius ratio of a loop-shaped coil pair is 1.02 for a uniform magnetic field and 1.75 for a uniform gradient field. The applicability of the method to other shapes of coil configuration was also illustrated. The best width to distance ratio for a square-shaped coil pair is 0.558 and 0.958 for uniform magnetic and gradient fields, respectively. The best height to width ratio and distance to width ratio for a rectangle-shaped coil pair is h/w = [0.9,1.1], d/w = [0.5,0.6] for uniform magnetic field and h/w = [1.0,1.2], d/w = [0.9,1.1] for uniform gradient field. Furthermore, simulations of a microparticle tracking the targeted trajectory were conducted to analyze the performance of the newly designed coils. The simulations suggested the ability of manipulating microparticles via the coils designed by our proposed method. The research mainly proposed a unified design and optimization method for a coil pair, which can support researchers while designing a specific coil pair according to the technical requirements. This study is aimed at researchers who are interested in EMA system and microrobots.

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https://cjme.springeropen.com/articles/10.1186/s10033-019-0378-y

DOI: 10.1186/s10033-019-0377-z

Dynamic and Static Characteristics of Double Push Rods Electromechanical Converter

Xuping Wang, Long Quan, Shiyi Luan & Xiaoqing Xu 

Abstract: Due to the influence of material characteristics and winding power, single output electromagnet has limited ability to improve the dynamic characteristic of electro-hydraulic valve. Therefore, an electromechanical converter with double push rods is proposed in this paper, which can simultaneously output two electromagnetic forces, can push or pull the valve core and sleeve according to the current direction and realize rapid operation of load. According to the electromagnetic principle and the magnetic circuit analysis method, the mathematical model and equivalent circuit of the electromechanical converter with double push rods are established. Through the finite element simulation model of the electromechanical converter with double push rods with the same magnetization directions, the changing rules of its magnetic field distribution and force–displacement behaviors are studied and analyzed. According to the analysis results, the electromagnetic mechanical parameters and mechanical structure of the electromechanical converter with double push rods are determined, and the prototype is made. The test platform for the push-pull characteristics of the electromechanical converter with double push rods is built, and its static and dynamic characteristics are tested and analyzed. The results show that the thrust and pull output characteristics of the internal and external push rods are basically consistent with the simulation output, and proportional to the current density of the coil; the push-pull hysteresis of internal and external push rods output force is less than 5%; and the dynamic time response characteristics of the displacement and force are obtained. The hysteresis effect of output force is improved effectively through the H bridge drive control circuit modulated by PWM. Compared with the displacement response of a single-winding electromagnet with a similar volume, it can effectively improve the dynamic displacement response. Follow-up work will further optimize the structure of the electromechanical converter and test the corresponding pilot valve. The research results provide a new theory for improving the output characteristics of electro-hydraulic pilot valve and have an extremely high engineering application value and broad application prospect.

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https://cjme.springeropen.com/articles/10.1186/s10033-019-0377-z

DOI: 10.1186/s10033-019-0373-3

Neural Network-Based Adaptive Motion Control for a Mobile Robot with Unknown Longitudinal Slipping

Gang Wang, Xiaoping Liu, Yunlong Zhao & Song Han 

Abstract: When the mobile robot performs certain motion tasks in complex environment, wheel slipping inevitably occurs due to the wet or icy road and other reasons, thus directly influences the motion control accuracy. To address unknown wheel longitudinal slipping problem for mobile robot, a RBF neural network approach based on whole model approximation is presented. The real-time data acquisition of inertial measure unit (IMU), encoders and other sensors is employed to get the mobile robot’s position and orientation in the movement, which is applied to compensate the unknown bounds of the longitudinal slipping using the adaptive technique. Both the simulation and experimental results prove that the control scheme possesses good practical performance and realize the motion control with unknown longitudinal slipping.

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https://cjme.springeropen.com/articles/10.1186/s10033-019-0373-3

DOI: 10.1186/s10033-019-0374-2

Mesoporous TiO2 Nanofiber as Highly Efficient Sulfur Host for Advanced Lithium–Sulfur Batteries

Xinyu Shan, Zuoxing Guo, Xu Zhang, Jie Yang & Lianfeng Duan 

Abstract: Currently, lithium–sulfur batteries suffer from several critical limitations that hinder their practical application, such as the large volumetric expansion of electrode, poor conductivity and lower sulfur utilization. In this work, TiO2 nanofibers with mesoporous structure have been synthesized by electrospinning and heat treating. As the host material of cathode for Li–S battery, the as prepared samples with novelty structure could enhance the conductivity of cathode composite, promote the utilization of sulfur, and relieve volume expansion for improving the electrochemical property. The initial discharge capacity of TiO2/S composite cathode is 703 mAh/g and the capacity remained at 652 mAh/g after 200 cycles at 0.1 C, whose the capacity retention remains is at 92.7%, demonstrating great prospect for application in high-performance Li–S batteries.

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https://cjme.springeropen.com/articles/10.1186/s10033-019-0374-2

DOI: 10.1186/s10033-019-0375-1

Sound Source Localisation for a High-Speed Train and Its Transfer Path to Interior Noise

Jie Zhang, Xinbiao Xiao, Xiaozhen Sheng & Zhihui Li 

Abstract: Noise is one of the key issues in the operation of high-speed railways, with sound source localisation and its transfer path as the two major aspects. This study investigates both the exterior and interior sound source distribution of a high-speed train and presents a method for performing the contribution analysis of airborne sound with regard to the interior noise. First, both exterior and interior sound source locations of the high-speed train are identified through in-situ measurements. Second, the sound source contribution for different regions of the train and the relationships between the exterior and interior noises are analysed. Third, a method for conducting the contribution analysis of airborne sound with regard to the interior noise of the high-speed train is described. Lastly, a case study on the sidewall area is carried out, and the contribution of airborne sound to the interior noise of this area is obtained. The results show that, when the high-speed train runs at 310 km/h, dominant exterior sound sources are located in the bogie and pantograph regions, while main interior sound sources are located at the sidewall and roof. The interior noise, the bogie area noise and the sound source at the middle of the coach exhibit very similar rates of increase with increasing train speed. For the selected sidewall area, structure-borne sound dominates in most of the 1/3 octave bands.

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https://cjme.springeropen.com/articles/10.1186/s10033-019-0375-1

DOI: 10.1186/s10033-019-0372-4

Damage Tolerance Assessment of a Brake Unit Bracket for High-Speed Railway Welded Bogie Frames

Bing Yang, Hao Duan, Shengchuan Wu & Guozheng Kang 

Abstract: The brake unit bracket of a bogie frame is an important load-carrying component, particularly under emergency start/stop conditions. Conventional infinite/safe life approaches provide an over-conservative recommendation for the allowable strength and lifetime, which hinders the lightweight design of modern railway vehicles. In this study, to ensure the reliability and durability of a brake unit bracket, an attempt was made to integrate the nominal stress method and an advanced damage tolerance method. First, a complex bogie frame was modelled using solid elements instead of plate and beam elements. A hot spot stress region on the bracket was found under an eight-stage load spectrum obtained from the Wuhan–Guangzhou high-speed railway line. Based on the probability of foreign damage, a semi-elliptical surface crack was then assumed for residual life assessment. The results obtained by the cumulative damage and damage tolerance methods show that the brake unit bracket can operate for over 30 years. Moreover, even if a 2-mm depth crack exists, the brake unit bracket can be safely operated for more than 2.27 years, with the hope that the crack can be detected in subsequent maintenance procedures. Finally, an appropriate safety margin was suggested which provides a basis for the life prediction and durability assessment of brake unit brackets of high-speed railways.

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https://cjme.springeropen.com/articles/10.1186/s10033-019-0372-4

DOI: 10.1186/s10033-019-0371-5

Flow Field and Temperature Field of Water-Cooling-Type Magnetic Coupling

Lei Wang, Zhenyuan Jia, Yuqin Zhu & Li Zhang 

Abstract: At present, the water-cooling simulation of the water-cooled magnetic coupler is based on the water-cooled motor and the hydraulic coupler, which cannot accurately characterize the temperature distribution of the rotating water-cooled coupling of the coupler. Focusing on rotating water cooling radiating, the present paper proposes simulating the water cooling temperature field as well as the flow field through the method of combining fluid-solid coupled heat transfer and MRF (Multiphase Reference Frame). In addition, taking an 800 kW magnetic coupling as an example, the paper optimizes the shape, number, cooling water inlet speed‚ and so on‚ of the cooling channel. Considering factors such as the complete machine’s temperature, and drag torque, it is proved that the cooling effect is best when there are 36 involute curved channels and when the inlet speed is 3 m/s. Further, through experiments, the actual temperature values at six different positions when 50 kW and 70 kW thermal losses differ are measured. The measured values agree with the simulation results, proving the correctness of the proposed method. Further, data have been collected during the entire experimental procedure‚ and the variation in the coupling’s temperature is analyzed in depth, with the objective of laying a foundation for the estimation of the inner temperature rise as well as for the optimization of the structural design.

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