Browse Topic: Overdrive transmissions
This study investigates the post-failure flight dynamics of a 1200 lb classical octocopter under single motor inoperative condition using nonlinear time-domain simulations with a baseline feedback controller. A physics based propulsion sizing strategy is developed using IEC duty cycle definitions where continuous requirements are derived from nominal hover with margin and short time capability is used to accommodate elevated post failure loads. The selected motor satisfies both regimes and enables transient overdrive without excessive weight penalty. Simulation results in hover and forward flight at the best range speed showing that the vehicle can recover from any single motor failure and retrim using inherent redundancy without fault identification. However, recovery involves significant transient attitude excursions and altitude loss, and requires substantial increases in motor power, with multiple motors exceeding S1 power limits. Post-failure maneuver simulations indicate retained controllability with some degradation and increased coupling. These simulations demonstrate that the proposed motor sizing enables necessary operation post-failure while avoiding unnecessary oversizing.
The main objective of this project was to compare the fuel consumption and dynamic performances of direct-drive and overdrive transmission tractors. Fuel consumption was evaluated at constant high speed and on various road profiles, while the dynamic performance was assessed on various road profiles only. The SAE Fuel Consumption Test Procedure (J1526) was used for constant high speed fuel consumption track test evaluations. The direct-drive transmission tractor consumed less than the overdrive transmission tractor, even though it was heavier. The testing on various road profiles was conducted using a towing dynamometer, for comparing the dynamic capability of the tractors when simulating the same towing load on two hilly road profiles: the Townes Pass path (in the Rocky Mountains) and the Saguenay path (in the Saguenay region of Quebec). Each tractor was to haul the set load along the given path while trying to attain 90 km/h speed. Results from the test showed almost identical dynamic performance for the Saguenay road profile. For the Townes Pass road profile, which has a steeper grade, the overdrive transmission tractor showed, to some extent, better dynamic performance than the direct drive tractor. Direct-drive transmissions are more efficient than overdrive transmissions, if they are geared correctly. The advantage is obvious in top gear, which was the case for the high constant speed test. The overall ratio (transmission plus differential) is higher for the tractors with overdrive transmission, and they provide better startability and gradeability. The tests on the two different road profiles partially confirmed this assumption, especially for the Saguenay route.
Heavy trucks increasingly employ lighter-weight materials and sleeker shapes-not just for body but major chassis components as well-to trim fuel consumption and emissions. It should come as no big surprise that the “heavy hitter” in boosting heavy-vehicle fuel efficiency is the hybrid powertrain, be it the electric or hydraulic variety. But, as many industry experts will tell you, hybridization does not benefit all medium- and heavy-duty vehicles equally. “There are technologies out there today and expected in the next five years that can help achieve what the president [Barack Obama] said was a 25% fuel-consumption reduction. That's his aim; I think it's achievable,” said Dr. Andrew Brown Jr., Executive Director and Chief Technologist for Delphi Corp. These technologies include hybrid powertrains, clean diesel technology, improved aerodynamics, low rolling resistance tires, and lightweight designs.
Provide standard shift pattern guidelines for manual transmission shift controls in light, medium, and heavy trucks and buses.
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