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

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. [ABSTRACT FROM AUTHOR]

The article looks into the understanding of general teacher's education in the U.S. Significantly, there has been a change in the leadership of teacher educators. The author discusses the Florida Program for doctoral candidates. Teacher education has been an important aspect in an effective program of general education in the