Heavy goods vehicles exhibit poor braking performance in emergency situations when compared to other vehicles. Part of the problem is caused by sluggish pneumatic brake actuators, which limit the control bandwidth of their antilock braking systems. In addition, heuristic control algorithms are used that do not achieve the maximum braking force throughout the stop. In this article, a novel braking system is introduced for pneumatically braked heavy goods vehicles. The conventional brake actuators are improved by placing high-bandwidth, binary-actuated valves directly on the brake chambers. A made-for-purpose valve is described. It achieves a switching delay of 3–4 ms in tests, which is an order of magnitude faster than solenoids in conventional anti-lock braking systems. The heuristic braking control algorithms are replaced with a wheel slip regulator based on sliding mode control. The combined actuator and slip controller are shown to reduce stopping distances on smooth and rough, high friction ( μ = 0.9) surfaces by 10% and 27% respectively in hardware-in-the-loop tests compared with conventional ABS. On smooth and rough, low friction ( μ = 0.2) surfaces, stopping distances are reduced by 23% and 25%, respectively. Moreover, the overall air reservoir size required on a heavy goods vehicle is governed by its air usage during an anti-lock braking stop on a low friction, smooth surface. The 37% reduction in air usage observed in hardware-in-the-loop tests on this surface therefore represents the potential reduction in reservoir size that could be achieved by the new system.

This paper summarises the measured emergency braking performance of a tri-axle heavy goods vehicle (HGV) semitrailer fitted with a novel pneumatic slip-control braking system developed by the Cambridge Vehicle Dynamics Consortium (CVDC). Straight-line braking tests were carried out from 40km/h in order to compare a commercially available electropneumatic HGV trailer ABS system and the CVDC system, which has bi-stable valves coupled with a sliding mode slip controller. On average, the CVDC system reduced stopping distance and air use by 15% and 22% respectively compared to conventional ABS. The most significant improvements were seen on a wet basalt tile surface (with similar friction properties to ice) where stopping distance and air use were improved by 17% and 30% respectively. A third performance metric, mean absolute slip error (MSE), is introduced to quantify each braking system's ability to track a wheel slip demand. Using this metric, the bistable valve system is shown to improve wheel slip demand tracking by 62% compared to conventional ABS. This improvement potentially allows more accurate control of wheel forces during extreme manoeuvres, providing scope for the future development of advanced stability control systems.

In this paper we describe how vehicle systems and the vehicle motion control are affected by automated driving on public roads. We describe the redundancy needed for a road vehicle to meet certain safety goals. The concept of system safety as well as system solutions to fault tolerant actuation of steering and braking and the associated fault tolerant power supply is described. Notably restriction of the operational domain in case of reduced capability of the driving automation system is discussed. Further we consider path tracking, state estimation of vehicle motion control required for automated driving as well as an example of a minimum risk maneuver and redundant steering by means of differential braking. The steering by differential braking could offer heterogeneous or dissimilar redundancy that complements the redundancy of described fault tolerant steering systems for driving automation equipped vehicles. Finally the important topic of verification of driving automation systems is addressed.

No abstract

No abstract

Knowledge about the tyre to road friction is central to many vehicle functions as well as the overall performance of the vehicle. In this paper, a new real-time algorithm is presented for estimating the coefficient of friction using available on-board sensor information. A computationally efficient algorithm is presented, that reduces resources usage compared to previously published approaches. Issues connected to heavy vehicles and friction estimation is addressed, such as wind up of hub assembly and vehicle speed sensing. The performance of the algorithm is illustrated on data sets acquired from the test track recordings in winter conditions.

No abstract

No abstract