Active Multi-Axle Steering of Heavy Goods Vehicles

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.