Active Multi-Axle Steering of Heavy Goods Vehicles

在加拿大、澳大利亚、美国和欧洲进行的研究表明，带有两个或更多拖车的长组合车辆（LCV）可以显著减少道路拥堵，提高安全性，提高运输成本效率，减少燃料使用和温室气体排放，并显著减少路面磨损。不幸的是，三个主要的实际障碍阻碍了LCV在英国的采用：（i）机动性差;（ii）高速稳定性差;（iii）可逆性差。(i)英国货运网络中的许多环形和狭窄的道路对于传统的LCV来说是不可能通过的。改善LCV的低速机动性的一种方法是使拖车和/或牵引车驱动轴转向。已经为刚性卡车和牵引车/半挂车开发了简单的“被动”转向系统。这样的系统将车轮转向角设置为与车辆几何形状成固定关系：角度不随速度而变化。最近的研究表明，被动转向系统通过减少切入，大大提高了牵引车/半挂车组合的低速机动性。它们还能显著降低轮胎侧向力/从而降低轮胎磨损并减少路面损坏。这对于在城市地区运输货物非常重要，因为车辆需要以低速通过急弯和小直径弯道。(ii)高速稳定性对于许多传统的LCV也是一个问题，因为横向加速度随着每个连续的拖车而被放大。这可能导致在规避机动过程中过早翻转。虽然被动转向将改善LCV的低速机动性，但申请人最近已经表明，这种系统降低了高速偏航稳定性，增加了向后放大并降低了操纵性。因此，在LCV上安装被动转向系统可能会进一步降低其已经很差的高速稳定性。为了在高速下克服这些问题，可以使用主动转向系统来代替被动转向。在主动系统中，当车辆处于运动中时，转向关系是变化的，以在所有速度下实现最佳性能。虽然这样的系统还没有被开发用于重型车辆，但它们已经成功地应用于汽车和SUV上：例如德尔菲的“Quadrasteer”系统安装在GMC SUV上。Quadrasteer提高了低速时的机动性，并改善了高速时的操控性和稳定性。通过在一般的HGV和特别是LCV上使用主动转向可以获得类似的益处。(iii)最后，传统LCV的可逆性差将严重限制英国现有货运码头和装卸码头基础设施的使用。然而，主动转向可以被设计为帮助驾驶员倒车复杂的多单元车辆。申请人的初步研究表明，主动转向可以改善牵引车/全挂车组合的可逆性，然而，仍然需要开发适合其他车辆组合（例如牵引车/半挂车和LCV）的算法。因此，本项目中要解决的主要研究挑战是开发用于LCV的主动转向技术。一旦原型技术已经开发和测试，它将有可能评估的成本和效益，实施主动转向的LCV在英国。这项研究将建立在以前的工作，主动转向系统的卡车在剑桥大学工程系。它将涉及理论控制系统的开发;使用现有的实验性重型货车单元对控制概念进行现场测试;原型致动器硬件开发和实验室测试;以及详细的成本/效益分析。该研究将由该大学的两名博士后研究人员与重型车辆行业公司联盟的工程师合作进行。

Studies performed in Canada, Australia, USA and in Europe have shown that long combination vehicles (LCVs), with two or more trailers can significantly reduce road congestion, improve safety, improve transportation cost efficiency, reduce fuel use and greenhouse gas emissions and significantly reduce road surface wear. Unfortunately three major practical barriers prevent adoption of LCVs in the UK: (i) poor manoeuvrability; (ii) poor high speed stability; and (iii) poor reversibility.(i) Many of the roundabouts and narrow roads in the UK's freight transportation network would be impossible for conventional LCVs to negotiate. One way to improve the low speed manoeuvrability of an LCV would be to steer the trailer and/or tractor drive axles. Simple 'passive' steering systems have been developed for rigid trucks and tractor/semi-trailers. Such systems set the road wheel steer angles in a fixed relationship to the geometry of the vehicle: the angles do not change with speed. Recent studies have shown that passive steering systems substantially improve the low-speed manoeuvrability of tractor/semi-trailer combinations by reducing cut-in. They also significantly reduce lateral tyre forces / leading to lower tyre wear and reduced road surface damage. This is important for transporting goods in urban areas where vehicles need to negotiate sharp corners and small diameter roundabouts, at low speeds.(ii) High speed stability is also a problem for many conventional LCVs since lateral accelerations are amplified with each successive trailer. This can lead to premature roll-over during evasive manoeuvres. While passive steering would improve the low speed manoeuvrability of LCVs, the applicants have recently shown that such systems reduce high-speed yaw stability, increase rearward amplification and degrade handling. Consequently fitting a passive steering system to an LCV is likely to further degrade its already poor high-speed stability. To overcome these problems at high speeds an active steering system could be used instead of passive steering. In an active system the steering relationship is varied while the vehicle is in motion to achieve optimal performance at all speeds. While such systems have yet to be developed for heavy vehicles, they have been successfully employed on cars and SUV's: eg Delphi's 'Quadrasteer' system fitted to GMC SUV's. Quadrasteer increases manoeuvrability at low speeds and improves handling and stability at high speeds. Similar benefits could be gained by using active steering on HGVs in general and LCVs in particular.(iii) Finally, the poor reversibility of conventional LCVs would severely restrict the use of existing freight terminals and loading dock infrastructure in the UK. However active steering could be designed to assist drivers to reverse complex multi-unit vehicles. Preliminary research by the applicants has shown that active steering can improve the reversibility of tractor/full trailer combinations, however, algorithms to suit other vehicle combinations, such as tractor/semi-trailers and LCVs, still need to be developed.The main research challenges to be addressed in this project are therefore to develop active steering technologies for LCVs. Once prototype technologies have been developed and tested it will be possible to assess the costs and benefits of implementing active-steering on LCVs in the UK.The research will build on previous work on active steering systems for lorries performed in Cambridge University Engineering Department. It will involve theoretical control system development; field testing of control concepts using existing experimental heavy goods vehicle units; prototype actuator hardware development and laboratory testing; and a detailed cost/benefit analysis. The research will be performed by two postdoctoral researchers in the university, working in collaboration with engineers from a consortium of companies in the heavy vehicle industry.