In this paper a novel architecture for a blended hydraulic hybrid power split transmission was presented. A compact SUV was used as a reference vehicle following the UDDS driving schedule. A baseline manual transmission, a conventional series hybrid PST, and the novel blended hybrid PST were modeled and simulated in the reference vehicle. Instantaneous optimization and dynamic programming were then used to optimally control all three transmissions in order to remove control as a factor affecting fuel consumption. The manual transmission achieved a fuel economy of 7.89 1/100 km. The series hybrid PST was able to reach a fuel economy of 7.34 1/100 km, a 7.0% improvement over the baseline manual transmission. Finally the blended hybrid PST achieved a fuel economy of 7.28 1/100 km which corresponds to an improvement of 7.7% and 0.8% over the manual and series hybrid PST transmissions respectively. The blended hybrid PST consumed 15.9% less energy than the series hybrid PST suggesting further improvements may be seen as engine efficiency improves. Fuel economy improvements in this paper are somewhat lower than that seen in some other studies. These discrepancies may be attributed to several factors. First the hydraulic units were sized to meet the maximum performance of a mechanical transmission instead of being sized to meet a certain drive cycle. This resulted in the hydraulic units being oversized for the UDDS cycle on which the comparisons were made. For different drive cycles the absolute fuel economies, and the differences in fuel economies between architectures, would be expected to change. This study also compared two optimally controlled hybrid transmissions to an optimally controlled baseline transmission. Other studies have compared a simulated hybrid architecture against real world fuel economies of a baseline vehicle which may lead to an overestimation in fuel economy improvements. How close an implementable control scheme can reach optimally controlled results was not investigated in this paper. It is likely the three architectures studied will each come within a different percentage of their optimal fuel consumption when controlled with an implementable controller. Further the two hybrid transmissions may more fairly be compared against automatic transmissions which are known to have lower efficiencies than manual transmissions. Regardless of the fuel economy results, the blended hybrid PST still presents some interesting advantages over series hybrid PST's. These include a significantly more efficient architecture due to the possibility of operating at a pressure lower than the accumulator's pressure. Improved operator feel is also a considerable advantage in automotive applications. Further the use of two smaller units connected to the wheels allows for higher speed application which is especially relevant to on-road vehicles. These advantages, coupled with the findings in this paper, indicate the blended hybrid PST has potential and merits further study.
Investigation and Energetic Analysis of a Novel Blended Hydraulic Hybrid Power Split Transmission
2014
12 Seiten, Bilder, 11 Quellen
Aufsatz (Konferenz)
Englisch
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