Abstract: According to the characteristics of construction machine such as hydraulic excavator, the necessity of torque compensation control system for diesel engine under the alternating load is analyzed. Based on the structure of parallel hydraulic-electrical hybrid system, a hydraulic control model mainly composed of pump, motor and accumulator is established, and the corresponding control method is developed. The engine torque control experiment is performed on a test rig where a 485 model diesel engine with full-range speed governor is used as control object. With the engine speed control lever being fixed in simulation and experiment process, the test data such as engine torque, engine speed, load torque and accumulator pressure show that the hydraulic control model can appropriately represent the real device characteristics. It also illustrates that the engine torque and speed can be controlled in steady state in various load conditions to make the engine more efficient. The contrast of different load testing indicates that the fuel consumption rate is reduced by 10%-20%, and the short-time overloading capability of the whole system is increased over 60%.

Key words: Alternating load, Diesel engine, Energy saving, Hybrid power, Torque compensation