Design of tyre force excitation for tyre–road friction estimation

Knowledge of the current tyre–road friction coefficient is essential for future autonomous vehicles. The environmental conditions, and the tyre–road friction in particular, determine both the braking distance and the maximum cornering velocity and thus set the boundaries for the vehicle. Tyre–road friction is difficult to estimate during normal driving due to low levels of tyre force excitation. This problem can be solved by using active tyre force excitation. A torque is added to one or several wheels in the purpose of estimating the tyre–road friction coefficient. Active tyre force excitation provides the opportunity to design the tyre force excitation freely. This study investigates how the tyre force should be applied to minimise the error of the tyre–road friction estimate. The performance of different excitation strategies was found to be dependent on both tyre model choice and noise level. Furthermore, the advantage with using tyre models with more parameters decreased when noise was added to the force and slip ratio.     

Optimal Control of the Tractor-Semitrailer Truck

This paper is concerned with the braking performance and the handling behavior of the tractor-semitrailer truck under optimal braking. Optimal control theory is used in order to deal with the problem and a combination of the steepest descent method and the Davidon Fletcher Powell method is used to solve it numerically. Results for some chosen braking maneuvers are obtained for a nonlinear truck model which has 14 degrees of freedom. These results show that, for the chosen maneuvers an idealized anti-skid braking is close to being optimal in the sense defined in this paper. Implementation of an idealized anti-skid braking on the tractor-semitrailer truck, however, may be not desirable.     

Comfort enhancement by an active vibration reduction system for a flexible railway car body

In order to improve the ride comfort of lightweight railway vehicles, an active vibration reduction system using piezo-stack actuators is proposed and studied in simulations. The system consists of actuators and sensors mounted on the vehicle car body. Via a feedback control loop, the output signals of the sensors which are measuring the flexible deformation of the car body generate a bending moment, which is directly applied to the car body by the actuators. This bending moment reduces the structural vibration of the vehicle car body. Simulations have shown that a significant reduction in the vibration level is achieved.     

简化FPSO在中拱中垂工况下管路应力分析

FPSO由于在深海环境下服役,受到波浪、海风、拖航等工况的影响造成中拱中垂,导致船体变形造成模块的相对运动使管道产生位移。又因为FPSO生产能力不断增强吨位不断加大,管路的复杂性和紧凑型也随着不断增大。在对FPSO管系进行应力分析时,传统中拱中垂工况需要大量的工时进行分析、验证、检查,其潜在工时达到2 500 h。本文利用行业内常用的CAESAR Ⅱ软件,通过船体变形量导致的管道附加位移和热胀位移进行结合计算出其热胀系数代替传统的工况分析方法,并验证了此方法的准确性,为FPSO管道系统生产设计提供技术借鉴。