Hybrid bulldozers use less fuel by providing better efficiency and fewer emissions, which was confirmed by one Caterpillar application of D7E in the market in 2010. To take advantages of the series hybrid bulldozer system, Chinese government launched similar hybrid bulldozer with independent double motor design. The Hybrid Bulldozer Power-Train system includes 14 components including motor, motor control system, engine, super capacitor to BMS and etc.
This specific hybrid architecture, compared with D7E, removes the complicated hydraulic steering system. Instead, the steering function was developed by running both traction motors, further simplifying the power-train system. A Diesel engine is used to propel the attached generator to produce AC power which is then converted to DC power and connected with the main power link (super capacitor). DC power is finally converted back to AC to propel those two independent traction motors. CAN network is applied for communication. Information could be displayed by the CAN connected instruments while components' status can be detected and diagnosed. By using remote wireless system (GPRS), the bulldozer could realize remote monitoring and remote driving functions.
The energy-saving principles with the corresponding power flow control algorithm of hybrid bulldozer are discussed. The power-train controller, based on driver's demand and vehicle situation, send torque or speed commands to the traction motors. A super capacitor was used as energy storage device. The vehicle control algorithms control the engine in the highly efficient load conditions, while the super capacitor works as a buffer to prevent the voltage from fluctuating. The results of vehicle tests show that the power follow control strategy can achieve the performances of 24% fuel efficiency.
