Direct Yaw Moment Control for Distributed Drive Electric Vehicle Handling Performance Improvement

For a distributed drive electric vehicle（DDEV） driven by four in-wheel motors, advanced vehicle dynamic control methods can be realized easily because motors can be controlled independently, quickly and precisely. And direct yaw-moment control（DYC） has been widely studied and applied to vehicle stability control. Good vehicle handling performance： quick yaw rate transient response, small overshoot, high steady yaw rate gain, etc, is required by drivers under normal conditions, which is less concerned, however. Based on the hierarchical control methodology, a novel control system using direct yaw moment control for improving handling performance of a distributed drive electric vehicle especially under normal driving conditions has been proposed. The upper-loop control system consists of two parts： a state feedback controller, which aims to realize the ideal transient response of yaw rate, with a vehicle sideslip angle observer; and a steering wheel angle feedforward controller designed to achieve a desired yaw rate steady gain. Under the restriction of the effect of poles and zeros in the closed-loop transfer function on the system response and the capacity of in-wheel motors, the integrated time and absolute error（ITAE） function is utilized as the cost function in the optimal control to calculate the ideal eigen frequency and damper coefficient of the system and obtain optimal feedback matrix and feedforward matrix. Simulations and experiments with a DDEV under multiple maneuvers are carried out and show the effectiveness of the proposed method： yaw rate rising time is reduced, steady yaw rate gain is increased, vehicle steering characteristic is close to neutral steer and drivers burdens are also reduced. The control system improves vehicle handling performance under normal conditions in both transient and steady response. State feedback control instead of model following control is introduced in the control system so that the sense of control intervention to drivers is relieved.

The association between Tai Chi exercise and safe driving performance among older adults： An observational study

Background: Age-related cognitive and physical decline can impair safe driving performance. Tai Chi exercise benefits cognitive and physical function and may influence safe driving performance in older adults. The primary aim of this observational study was to compare cognitive processes and physical function related to safe driving performance among older adult Tai Chi practitioners to normative reference values.Secondary aims were to examine relationships between Tai Chi exercise habits, cognitive processes, and physical function related to safe driving performance and to explore potential predictors of safe driving performance.Methods: The Driving Health Inventory, the Driving Scenes Test, other driving-related cognitive and physical measures, and self-reported measures including the Mindful Attention Awareness Scale(MAAS) and the Vitality Plus Scale(VPS) were collected from current Tai Chi practitioners(n = 58; age 72.9 ± 5.9 years, mean ± SD) with median >3 years Tai Chi practice.Results: Compared to normative reference values, participants performed better on numerous cognitive measures including the Driving Scenes Test(p < 0.001, d = 1.63), maze navigation(p = 0.017, d = 0.27), the Useful Field of View Test(p < 0.001, r = 0.15), and on physical measures including the Rapid Walk Test(p < 0.001, r = 0.20), and the Right Foot Tapping Test,(p < 0.001, r = 0.35). Participants scored higher than normative reference values on MAAS and VPS(p < 0.001, d = 0.75; p = 0.002, d = 0.38, respectively). Statistically significant correlations were found between several study measures. The digit span backward test was the strongest predictor of safe driving performance(β = 0.34,p = 0.009).Conclusion: Tai Chi exercise has the potential to impact cognitive processes and physical function related to safe driving performance. Further study using randomized controlled trials, structured Tai Chi exercise doses, and driving simulator or on-road driving performance as outcome measures are warranted.

Five characteristics of China textile industry performance in 2017 Former and present driving forces transferred significantly

According to the 2017 Summary Conference of China National Textile and Apparel Council(CNTAC)held on January 22nd to 23rd,in the first 11 months of 2017,the overall operation of China’s textile industry showed a steady growth rate,stable domestic demand growth。

A Study on Performance and Reliability of Urethral Valve Driven by Ultrasonic-vaporized Steam

The aim of this study is to investigate the performance and reliability of urethral valve driven by ultrasonic-vaporized steam.The performance model of urethral valve is established to analyze the driving and opening/closing performances of urethral valve.The reliability model of urethral valve is obtained,and the reliability simulation algorithm is proposed to calculate the reliability index of urethral valve.The numerical simulation and experimental results show that urethral valve has a good opening/closing performance,the driving performance can be improved by increasing ultrasonic intensity,radiation area and ultrasonic frequency,and the corrosion and aging of driving bags are the weak links of urethral valve.

Drivers＇ smart advisory system improves driving performance at STOP sign intersections

STOP signs are often physically blocked by obstacles at the corner, forming a safety threat. To enhance the safety at an un-signalized intersection like a STOP sign intersection, a radio frequency identification （RFID） based drivers smart advisory system （DSAS） was developed, which provides drivers with an earlier warning message when they are approaching an un- signalized intersection, tn this research, a pilot field test was conducted with the DSAS alarm on an approach towards a STOP sign intersection in a residential area in Houston, Texas. The designed test route covers all turning movements, including left turn, through movement, and right turn. GPS units recorded test drivers＇ driving behaviors. A self-devel- oped MATLAB program and statistically significant difference t-test were applied to analyze the impacts of the DSAS messages on drivers＇ driving performance, in terms of approaching speed profile, acceleration/deceleration rates, braking distance, and possible extra vehicle emissions induced by the introduction of the DSAS message. Drivers＇ preference on the DSAS was investigated by a designed survey questionnaire among test drivers. Results showed that the DSAS alarm was able to induce drivers to drive significantly slower to approach a STOP sign intersection, perform smaller fluctuation in acceleration/deceleration rates, and be more aware of a coming STOP sign indicated by decelerating earlier. All test drivers preferred to follow the DSAS alarm on roads for a safety concern. Further, the DSAS alarm caused the reduction in emission rates through movement. For a general observation, more road tests with more participants and different test routes were recommended.

Human Performance in Critical Scenarios as a Benchmark for Highly Automated Vehicles

Before highly automated vehicles(HAVs)become part of everyday traffic,their safety has to be proven.The use of human performance as a benchmark represents a promising approach,but appropriate methods to quantify and compare human and HAV performance are rare.By adapting the method of constant stimuli,a scenario-based approach to quantify the limit of(human)performance is developed.The method is applied to a driving simulator study,in which participants are repeatedly confronted with a cut-in manoeuvre on a highway.By systematically manipulating the criticality of the manoeuvre in terms of time to collision,humans’collision avoidance performance is measured.The limit of human performance is then identified by means of logistic regression.The calculated regression curve and its inflection point can be used for direct comparison of human and HAV performance.Accordingly,the presented approach represents one means by which HAVs’safety performance could be proven.

Evaluation of intersection conflict warning system at unsignalized intersections:A review

Unsignalized intersections are identified as the critical locations due to higher number of road crashes at these locations.The primary causes of crashes at unsignalized intersections are limited sight distance,incorrect assessment of gaps by drivers on the minor road,and higher speeds of vehicles on the major road.In an effort to improve safety and reduce the severity of crashes at unsignalized intersections,an intelligent transportation system(ITS)called the intersection conflict warning system(ICWS)has been developed.The ICWS consists of an activated warning sign and sensors that detect vehicles approaching the intersection.This paper aims to summarize the performance evaluation of ICWS that has been published in the literature.The review commences with an overview of the purpose of designing and installing ICWS at unsignalized intersections.It then discusses driving performance measures considered to evaluate the effectiveness of ICWS in three different environments,i.e.,real world,driving simulator,and simulations,and their results are presented.The paper also discusses the type of sensors used to detect vehicles approaching the intersection and their accuracy in vehicle detection.The results reveal that ICWS had substantially improved driver behaviour.In the presence of ICWS,drivers resulted in shorter reaction time,lower approach speed,increased critical gap acceptance,and reduction in conflicts.An improvement in the performance of ICWS can be achieved by educating drivers about the sign,maintaining system reliability,and further examining the effect of various traffic factors,driver factors,and environmental factors on ICWS.The findings of this study can help researchers and engineers to design a better ICWS that can greatly enhance driving performance and safety at unsignalized intersections.