TY - GEN
T1 - Fuel economy comparisons of series, parallel and HMT hydraulic hybrid architectures
AU - Du, Zhekang
AU - Cheong, Kai Loon
AU - Li, Perry Y
AU - Chase, Thomas R
PY - 2013
Y1 - 2013
N2 - Since hydraulic hybrid vehicles are power dense and do not require costly batteries, they have the potential to achieve high fuel economy and performance and at low cost. The three main classes of hydraulic hybrid architectures are series, parallel and hydro-mechanical (HMT) or power-split. These architectures have intrinsic differences in transmission efficiencies and effectiveness in engine management. This paper compares the fuel economies and performance of these architectures and validates these features. Using a Toyota Prius like engine and chassis as common factors, fuel economies are compared for the 'optimal' design for each architecture which considers both the physical designs and the engine/energy management. Physical design variables include pump/motor sizes and gear ratios. The effect of pump/motors efficiencies, extra gears and different engine efficiency maps are also studied. To improve computational efficiency in evaluating fuel economy, engine operation is restricted to several operating modes and the accumulator pressure is assumed to be constant. These simplifications enable the Lagrange multiplier method to be employed so as to quickly determine the optimal engine management control and the resulting fuel economy for each design iteration. Full optimal control computations without the simplifying assumptions for the optimized design for each architecture (using dynamic programming) verify that, despite these simplification, the estimated fuel economies are close. It is shown that hybrid HMT offers the best fuel economy for various hydraulic efficiencies, followed by parallel and series architectures. However, the difference between HMT and parallel architectures diminishes if the engine has a wide efficient speed range of operation. It is also shown that an extra mechanical gear ratio can significantly increase fuel economy for all three architectures.
AB - Since hydraulic hybrid vehicles are power dense and do not require costly batteries, they have the potential to achieve high fuel economy and performance and at low cost. The three main classes of hydraulic hybrid architectures are series, parallel and hydro-mechanical (HMT) or power-split. These architectures have intrinsic differences in transmission efficiencies and effectiveness in engine management. This paper compares the fuel economies and performance of these architectures and validates these features. Using a Toyota Prius like engine and chassis as common factors, fuel economies are compared for the 'optimal' design for each architecture which considers both the physical designs and the engine/energy management. Physical design variables include pump/motor sizes and gear ratios. The effect of pump/motors efficiencies, extra gears and different engine efficiency maps are also studied. To improve computational efficiency in evaluating fuel economy, engine operation is restricted to several operating modes and the accumulator pressure is assumed to be constant. These simplifications enable the Lagrange multiplier method to be employed so as to quickly determine the optimal engine management control and the resulting fuel economy for each design iteration. Full optimal control computations without the simplifying assumptions for the optimized design for each architecture (using dynamic programming) verify that, despite these simplification, the estimated fuel economies are close. It is shown that hybrid HMT offers the best fuel economy for various hydraulic efficiencies, followed by parallel and series architectures. However, the difference between HMT and parallel architectures diminishes if the engine has a wide efficient speed range of operation. It is also shown that an extra mechanical gear ratio can significantly increase fuel economy for all three architectures.
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M3 - Conference contribution
AN - SCOPUS:84883530912
SN - 9781479901777
T3 - Proceedings of the American Control Conference
SP - 5954
EP - 5959
BT - 2013 American Control Conference, ACC 2013
T2 - 2013 1st American Control Conference, ACC 2013
Y2 - 17 June 2013 through 19 June 2013
ER -