Optimal control based design of output coupled power split hydraulic hybrid
Abstract
Hydraulic hybrid power trains/vehicles (HHV) achieve higher power density, better utilization of regenerative braking due to faster storage of brake energy in hydraulic accumulators, much lower installation cost and no recycling problems compared to its electric counterpart. The goal of this thesis is to investigate the potential of fuel savings of hydraulic hybrid power trains compared to electric hybrid vehicles. This thesis utilizes optimal control for both system design and control. As a result, a novel design optimization method to minimize fuel consumption is proposed for hydraulic hybrid vehicles. The configuration chosen for this study is output-coupled power-split (OCPSD) hydraulic hybrid architecture. All general design variables in OCPSD are considered including standing gear ratio of planetary gear train, primary unit size, and secondary unit size, volume of accumulator, minimum system working pressure, axle ratio, primary gear ratio and secondary gear ratio. Deterministic dynamic programming (DDP) is chosen to create an optimal controlled environment for this type of transmission. DDP is a classic and powerful approach in optimal control theory to solve multi-stage decision problems and the global optimum can be guaranteed. Redundancy of design parameters and equivalence between two layouts of OCPSD are investigated to help reduce design space. A design of experiment is conducted in order to find the optimal design for a chosen representative drive cycle and fuel economy is compared between optimal and static design. Finally the result of a parameter variation study is discussed.
Degree
M.S.M.E.
Advisors
Ivantysynova, Purdue University.
Subject Area
Automotive engineering|Mechanical engineering
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