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Hallandale, FL, United States

Miller J.I.,Brake Kingdom | Henderson L.M.,University of Cambridge | Cebon D.,University of Cambridge
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science | Year: 2013

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. © 2012 IMechE.

Miller J.I.,Brake Kingdom | Cebon D.,University of Cambridge
Vehicle System Dynamics | Year: 2013

Progress in reducing actuator delays in pneumatic brake systems is opening the door for advanced anti-lock braking algorithms to be used on heavy goods vehicles. However, little has been published on slip controllers for air-braked heavy vehicles, or the effects of slow pneumatic actuation on their design and performance. This paper introduces a sliding mode slip controller for air-braked heavy vehicles. The effects of pneumatic actuator delays and flow rates on stopping performance and air (energy) consumption are presented through vehicle simulations. Finally, the simulations are validated with experiments using a hardware-in-the-loop rig. It is shown that for each wheel, pneumatic valves with delays smaller than 3ms and orifice diameters around 8mm provide the best performance. © 2013 Copyright Taylor and Francis Group, LLC.

Hartley J.,Tata Motors | Day A.,Tata Motors | Campean I.,Tata Motors | McLellan R.G.,Brake Kingdom | Richmond J.,Tata Motors
SAE Technical Papers | Year: 2010

Tata Motors Limited plan to launch a range of full electric vehicles (FEVs) to the European market. Regenerative braking is advantageous in maximising range between recharging, but presents challenges of acceptable performance, weight, cost and the 'blending' of regenerative braking with friction braking. Control systems for regenerative braking have been developed by manufacturers to enable recuperation of kinetic energy which would otherwise be converted to heat and wasted through the use of friction brakes. This paper presents the approach taken by Tata Motors Ltd. to optimise the design and operation of a regenerative braking system to maximise range and energy efficiency. The Tata Ace EV is a Class N1 light commercial FEV with drive to the rear wheels only. This presents the challenge of harvesting energy from the axle which contributes a varying amount of the vehicle braking effort depending upon load. It is essential to maintain stability during braking, so premature rear-wheel-lock must be avoided at all times, particularly in low adhesion conditions. Road vehicles must be capable of high decelerations which cannot currently be achieved with conventional regenerative braking alone. Multi-mode braking enables higher decelerations to be generated by combining regenerative and friction braking. This in turn requires careful design of the control architecture to create a conventional brake pedal 'feel' such that the blend between regenerative and friction braking is imperceptible to the driver. Energy recuperation is strongly influenced by vehicle usage. A vehicle travelling at constant speed on motorways may produce very little reusable braking energy because brake applications are infrequent. A vehicle travelling downhill may produce excessive braking energy which may have to be dumped. It has been suggested [1] that vehicle usage which promotes the repeated recuperation of small amounts of energy (e.g. the New European Drive Cycle test schedule, Figure 1) makes the best use of a regenerative braking system to maximise range (distance between recharges). Energy recovered through regenerative braking is fed to a storage device and it is the ability of this device to receive and release energy which determines the power capability of the regenerative braking system. The Tata Ace vehicle powertrain system has been modelled in full with an accelerator pedal based regenerative braking system. Proportional regenerative braking to replicate engine braking on overrun has been applied when the accelerator pedal is released, with results suggesting that high levels of regenerative braking on the accelerator pedal can be detrimental to energy efficiency. Copyright © 2010 SAE International.

Miller J.I.,Brake Kingdom | Cebon D.,University of Cambridge
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science | Year: 2012

Heavy vehicles have sluggish pneumatic brake actuators that limit the control bandwidth of their anti-lock braking systems. In order to implement more effective braking controllers, it is proposed that high-bandwidth, binary-actuated valves are directly placed on the brake chambers. This article details investigations made into modelling and controlling heavy-vehicle pneumatic brake actuators with a view towards implementing the novel brake actuator design. One-dimensional flow theory is combined with simple thermodynamic arguments for polytropic systems to describe the charging and discharging of a brake chamber. Particular attention is paid to the simulation of perceptible vibrations caused by the piston's motion at relatively low charging pressures, using a hysteresis model. The resulting equations are linearized and used to design a closed-loop pressure controller for the actuator. Finally, the non-linear performance limits of the valves, caused by dead-zones and time delays, are investigated using a describing function analysis. © 2011 IMechE.

The U.K. Government's Sustainable Growing Media Task Force has produced a roadmap for the future development of sustainable growing media in the U.K. Widely acknowledged as both perceptive and accurate and offering pragmatic solutions, the task force chairman's report Towards sustainable growing media (Knight, 2012) has been welcomed by all sides of the horticultural industry in the U.K. This paper discusses the key points that have emerged from the task force'swork.

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