Hybrid Electric Powertrain Design and Control with Planetary Gear Sets for Performance and Fuel Economy

Abstract:

Planetary gear sets (PGs) play a key role in hybrid electric vehicle (HEV) design by enabling a variety of unique architectures using a limited number of powertrain components. Leveraging the capability of this mechanical device, this study introduces an automated design process for PG-based HEV systems focusing on both fuel economy and performance. The proposed process is based on the exhaustive search of all powertrain modes that can be generated with a given set of components. It includes the derivation of speed and torque relationships and powertrain type of each mode in the design space, and mode performance analyses including forward- and backward-speed gradeability, long-hauling torque, and acceleration time for all PG gear ratio combinations. Each mode combination that meets the performance criteria and the clutches necessary for the mode transition constitute a competent design. At the end of the process, the fuel economy improvement potential of each design is evaluated using an algorithm that approximates dynamic programming optimization. The results show that light-duty truck performance requirements can be met by many two-PG HEV designs without sacrificing fuel economy. In addition to the design process, the feasibility of mode transitions and the effect of mode transitions on the fuel economy simulation results are investigated.