Enhanced Sliding Mode Wheel Slip Controller for Heavy Goods Vehicles

This paper introduces an improved version of a sliding mode slip controller for pneumatic brake system ofheavy goods vehicles, HGVs. Using the Fast Actuating Brake Valve, FABV, allows to adopt advance control approaches forwheel-slip controllers which provide features such as fast dynamic response, stability and robustness. In this paper, the slidingmode algorithm which was developed for the speed dependent wheel slip control using the FABV hardware is analysed andimproved. The asymptotic convergence properties of the control algorithm are proven using Lyapunov stability theory and therobustness of the method is investigate

Circadian changes and sex-related differences in fetal heart rate parameters

BACKGROUND: Previous researchers have studied circadian changes in the fetal heart rate (FHR) on small sample sizes and in a strictly controlled environment. This study was undertaken to investigate these changes during the late second and third trimesters, using a portable fetal electrocardiogram recording device (Monica AN24) in pregnant women in home and hospital environments with unrestricted mobility. METHODS: This was a prospective cohort study of 54 pregnant women with uncomplicated singleton pregnancies between 25 and 40 weeks gestation. FHR recordings were made up to 16 h at home or in the hospital setting in the United Kingdom. FHR data over 90 min periods were averaged and the day (7:00 am-11:00 pm) and night (11:00 pm-7:00 am) data from the same individual were compared. Data were examined for evidence of sex-related differences. RESULTS: During the night, there was a significant reduction in basal heart rate (bFHR) and a significant increase in short term variation (STV) and long term variation (LTV) (P < 0.05). Basal FHR decreased (P < 0.002), whereas LTV increased (P = 0.014) with advancing gestation. Male fetuses showed greater day: night variation than females regardless of gestation (P = 0.014). There was a higher bFHR in fetuses monitored during the day in hospital (P = 0.04). CONCLUSION: This study demonstrates that there are sex-, environment and time-related differences in the FHR parameters measured. These differences may need to be considered taken when interpreting FHR data

Comparison of diurnal variations, gestational age and gender related differences in fetal heart rate (FHR) parameters between appropriate-for-gestational-age (AGA) and small-for-gestational-age (SGA) fetuses in the home environment

Objective To assess the influence of gender, time of the day and gestational age on fetal heart rate (FHR) parameters between appropriate-for-gestational-age (AGA) and small-for-gestational age (SGA) fetuses using a portable fetal ECG monitor employed in the home setting. Methods We analysed and compared the antenatal FHR data collected in the home setting on 61 healthy pregnant women with singleton pregnancies from 24 weeks gestation. Of the 61 women, 31 had SGA fetuses (estimated fetal weight below the tenth gestational centile) and 30 were pregnant with AGA fetuses. FHR recordings were collected for up to 20 h. Two 90 min intervals were deliberately chosen retrospectively with respect to signal recording quality, one during day-time and one at night-time for comparison. Results Overall, success rate of the fetal abdominal ECG in the AGA fetuses was 75.7% compared to 48.6% in the SGA group. Based on randomly selected episodes of heart rate traces where recording quality exceeded 80% we were able to show a marginal difference between day and night-time recordings in AGA vs. SGA fetuses beyond 32 weeks of gestation. A selection bias in terms of covering different representation periods of fetal behavioural states cannot be excluded. In contrast to previous studies, we neither controlled maternal diet and activity nor measured maternal blood hormone and heart rate as all mothers were monitored in the home environment. Conclusion Based on clinically unremarkable, but statistically significant differences in the FHR parameters between the AGA and SGA group we suggest that further studies with large sample size are required to assess the clinical value of antenatal fetal ECG monitoring

A Numerical and experimental study on the crash behavior of the extruded aluminum crash box with elastic support

Thin-walled structures like crash boxes may be used as energy absorption members in automotive chassis. There have been many studies addressing the behaviors of energy absorption members on frontal crash. These researches have attempted to predict the energy absorption and maximum impact load in shell structures. The energy absorption and maximum impact load depend on many parameters including boundary condition, history of plastic deformation during metalworking, geometry; and material and impact energy (i.e. mass and velocity of the striker). This study examined the crash behavior of square tube made of the extruded aluminum alloy 6063T4 using an elastic boundary condition -instead of rigid boundary condition- on the bottom of a crash box, In addition, the effect of elastic boundary condition on energy absorption of square tubes under the impact load was investigated both numerically and experimentally. Results showed that using elastic boundary could change the deformation mode and decrease the maximum impact load. Further, a high correlation between the numerical and experimental results validated the findings of the study

High-temperature tensile behavior and high-cycle fatigue properties of Mg-7Li-1Zn alloy

The use of light steels such as magnesium alloys is increasing due to their suitable mechanical behavior in various industries (e.g., automotive, aerospace, and electronic engineering). In this regard, pure magnesium is one of the most earth-abundant metals and has unique properties such as high strength-toweight ratio and very high recyclability. Among magnesium alloys, magnesium compounds and various percentages of lithium are known as one of the most popular engineering metals due to their high formulation capability. Also, significant features of magnesium-lithium alloy include its high elongation beside the low density. The results of previous studies indicate that annealing at 350 degrees C for 3 h leads to the same physical properties in different directions for Mg-7Li-1Zn alloy. The main aim of this research is to investigate the static properties at different temperatures and the high-cycle fatigue behavior of this alloy. To this end, Optical Microscopy (OM) observations and X-ray Diffraction (XRD) analysis were employed to determine the metallurgical properties of the material. Next, tensile and fatigue test specimens were fabricated according to ASTM E21 and ASTM E466 standards, respectively. Tensile tests were performed at the temperature of the room, 150, 200, and 300 degrees C. The key parameters were extracted and compared to that of pure Mg. Eventually, force-controlled axial fatigue tests were carried out on pure Mg and Mg-7Li-1Zn specimens under a loading frequency of 10 Hz and fully reversed loading. The experimental results reveal that fatigue strength of Mg-7Li-1Zn alloy is much higher than pure magnesium (i.e., the fatigue life improvement of 400% occurs by utilizing Mg-7Li-1Zn in compared with fatigue life of pure Mg at the maximum loading of 50 MPa). (c) 2020 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the Innovative Manufacturing, Mechatronics & Materials Forum 2020