Analysis of planetary gear hybrid powertrain system part 2: Output split system


In recent studies, various types of multi-mode electric variable transmissions for hybrid electric vehicles have been proposed. A multi-mode electric variable transmission consists of two or more different types of a planetary gear hybrid powertrain system (PGHP), which can change power flow type using clutches to improve transmission efficiency. Input split systems are generally used for the single-mode powertrain because of their overall superiority, but other power split systems such as output split and compound split systems can be used in the dual-mode powertrain. In this study, we analyze the power transmission characteristics of output split systems, and evaluate their fuel economies in the FTP72 cycle, acceleration performance, and constant vehicle speeds. These results enable the selection of appropriate systems for a dual-mode powertrain.

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α :

ratio of lever length of MG1 to lever length of input from output

R :

planetary gear ratio, ring/sun


reduction gear ratio of engine

R O :

reduction gear ratio of output shaft

R MG1 :

reduction gear ratio of MG1

R MG2 :

reduction gear ratio of MG2


engine torque

T O :

output shaft torque

T MG1 :

MG1 torque

T MG2 :

MG2 torque

ω ENG :

engine speed

ω O :

output shaft speed

ω MG1 :

MG1 speed

ω MG2 :

MG2 speed

η MG1 :

charging efficiency of motor 1

η MG2 :

discharging efficiency of motor 2


power split ratio, power to the electric pass/total power

γ :

speed ratio of input speed to output speed

γ DTP :

speed ratio of input speed to output speed when speed of MG1 or MG2 is zero


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Correspondence to H. Yang.

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Yang, H., Kim, B., Park, Y. et al. Analysis of planetary gear hybrid powertrain system part 2: Output split system. Int.J Automot. Technol. 10, 381–390 (2009).

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Key Words

  • Transmission efficiency
  • Hybrid electric vehicle
  • Planetary gear
  • Output split