401 resultados para Brake Fade.


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National Highway Traffic Safety Administration, Washington, D.C.

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National Highway Traffic Safety Administration, Washington, D.C.

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Track defects cause profound effects to the stability of railway wagons; normally such problems are modeled for cases of wagons running at constant speed. Brake/traction torque adversely affect the wheel-rail contact characteristics but they are not explicitly considered in most of the wagon-track interaction simulation packages. This research developed a program that can simulate the longitudinal behaviour of railway wagon dynamics under the actions of braking or traction torques. This paper describes the mathematical formulation of modelling of a full wagon system using a fixed coordinate reference system. The effect of both the lateral and the vertical track geometry defects to the dynamics of wagons is reported; sensitivity of traction/brake state is analysed through a series of numerical examples.

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Investigates the braking performance requirements of the UltraCommuter, a lightweight series hybrid electric vehicle currently under development at the University of Queensland. With a predicted vehicle mass of 600 kg and two in-wheel motors each capable of 500 Nm of peak torque, decelerations up to 0.46 g are theoretically possible using purely regenerative braking. With 99% of braking demands less than 0.35 g, essentially all braking can be regenerative. The wheel motors have sufficient peak torque capability to lock the rear wheels in combination with front axle braking, eliminating the need for friction braking at the rear. Emergency braking levels approaching 1 g are achieved by supplementation with front disk brakes. This paper presents equations describing the peak front and rear axle braking forces which occur under straight line braking, including gradients. Conventionally, to guarantee stability, mechanical front/rear proportioning of braking effort ensures that the front axle locks first. In this application, all braking is initially regenerative at the rear, and an adaptive ''by-wire'' proportioning system presented ensures this stability requirement is still satisfied. Front wheel drive and all wheel drive systems are also discussed. Finally, peak and continuous performance measures, not commonly provided for friction brakes, are derived for the UltraCommuter's motor capability and range of operation.

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The BRAKE Driver Awareness Program provides evidence-based behaviour, risk, attitude and knowledge education for young drivers. BRAKE was founded during 2006 by Queensland Police Sergeant Rob Duncan and has been delivered to more than 35,000 senior secondary students since 2007. BRAKE is a participant directed program supported by resources provided at no cost. It includes eight parts able to be delivered in different configurations. BRAKE is endorsed by the Queensland Police and Queensland Ambulance Services. It is recognised by the Queensland Studies Authority as a Queensland Certificate of Education registered life skills course. This session is a must attend for secondary teachers, coordinators, staff in senior leadership positions and other stakeholders seeking a unique approach to adolescent road safety education. It will conclude with an opportunity to consider how BRAKE can be integrated into the senior secondary Health Education curriculum or pastoral care, social action and personal development programs.

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Autobiographical manuscript

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With no Channel State Information (CSI) at the users, transmission over the two-user Gaussian Multiple Access Channel with fading and finite constellation at the input, will have high error rates due to multiple access interference (MAI). However, perfect CSI at the users is an unrealistic assumption in the wireless scenario, as it would involve extremely large feedback overheads. In this paper we propose a scheme which removes the adverse effect of MAI using only quantized knowledge of fade state at the transmitters such that the associated overhead is nominal. One of the users rotates its constellation relative to the other without varying the transmit power to adapt to the existing channel conditions, in order to meet certain predetermined minimum Euclidean distance requirement in the equivalent constellation at the destination. The optimal rotation scheme is described for the case when both the users use symmetric M-PSK constellations at the input, where M = 2(gimel), gimel being a positive integer. The strategy is illustrated by considering the example where both the users use QPSK signal sets at the input. The case when the users use PSK constellations of different sizes is also considered. It is shown that the proposed scheme has considerable better error performance compared to the conventional non-adaptive scheme, at the cost of a feedback overhead of just log log(2) (M-2/8 - M/4 + 2)] + 1 bits, for the M-PSK case.

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For transmission over the two-user Gaussian Multiple Access Channel with fading and finite constellation at the inputs, we propose a scheme which uses only quantized knowledge of fade state at users with the feedback overhead being nominal. One of the users rotates its constellation without varying the transmit power to adapt to the existing channel conditions, in order to meet certain pre-determined minimum Euclidean distance requirement in the equivalent constellation at the destination. The optimal modulation scheme has been described for the case when both the users use symmetric M-PSK constellations at the input, where M = 2λ, λ being a positive integer. The strategy has been illustrated by considering examples where both the users use QPSK signal set at the input. It is shown that the proposed scheme has considerable better error performance compared to the conventional non-adaptive scheme, at the cost of a feedback overhead of just [log2 (M2/8 - M/4 + 2)] + 1 bits, for the M-PSK case.

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