Abstract: Powertrain system and its energy control strategies are studied in order to improve fuel consumption of a kind of series hybrid tracked bulldozer. Mathematical models of engine’s output power, fuel consumption, and generator’s efficiency are established base on their dynamic working characteristic analysis and experimental data on test bench. By utilizing series-parallel topological structure between ultracapacitor and resistance, an ultracapacitor’s dynamic working model is setup, and its working scope of state of charge(SOC) is build. The lowest fuel consumption curve is found after above models’ optimization, and a power flowing control strategy based on the engine’s optimal fuel consumption is proposed. This power flowing control strategy is simulated under a bulldozer’s typical working duty. The variations of ultracapicitor’s charge and discharge parameters, like voltage, current, and SOC are demonstrated. The engine’s rotate speed, output torque, fuel consumption and the position of accelerate pedal are revealed comparing to these of the prototype tracked bulldozer with traditional mechanical powertrain structure. The results show that the proposed control strategy is verified well, and, the engine fuel economy can be improved 13.1% compared to the prototype one under the same typical working duty of the bulldozer.

Key words: control strategy, engine-generator, fuel economy, power following, series hybrid tracked bulldozer