A Novel Three-Planetary-Gear Power-Split Hybrid Powertrain for Tracked Vehicles 2018-01-1003

Tracked vehicles are widely used for agriculture, construction and many other areas. Due to high emissions, hybrid electric driveline has been applied to tracked vehicles. The hybrid powertrain design for the tracked vehicle has been researched for years. Different from wheeled vehicles, the tracked vehicle not only requires high mobility while straight driving, but also pursues strong steering performance. The paper takes the hybrid track-type dozers (TTDs) as an example and proposes an optimal design of a novel power-split powertrain for TTDs. The commercial hybrid TTD usually adopts the series hybrid powertrain, and sometimes with an extra steering mechanism, which has led to low efficiency and made the structure more complicated. The proposed three-planetary-gear power-split hybrid powertrain can overcome the problems above by utilizing the characteristics of planetary gear sets. The proposed powertrain has two outputs connected to the left and right track respectively, which can provide the accurate torque to both sides of tracks when straight driving, skid steering, or driving backwards. The paper gives the dynamic characteristic matrices to search the big pool of designs with three planetary gear sets more simple. An analytically-based method is used to classify the feasible modes into three groups which have superior dynamic features respectively. Dual-mode designs with two clutches are presented using mode-combination method. A near-optimal control rapid strategy, power-weighted efficiency analysis for rapid sizing (PEARS+), is used as the control strategy. The control results show that the novel design has better drivability and fuel economy than the series hybrid benchmark. The proposed new kind of powertrain has shown good potential which can be considered for future industrial application.