As one of the most important types of construction machinery in engineering construction, hydraulic excavator has the characteristics of high power, high fuel consumption and low energy utilization. In order to improve its working efficiency and reduce fuel consumption, excavator manufacturers and domestic universities have carried out in-depth research and made some progress. Such as using hybrid technology to improve the fuel economy of excavator, reducing energy loss through global power matching, using the control method of combining full power and variable power to reduce fuel consumption and so on.
The diesel engine is used as the power source of the hydraulic excavator to drive the hydraulic pump to work. The hydraulic energy can drive the actuators to realize the excavator working device or motor action.
For the engine, the hydraulic pump is the load. Because the engine in different environments, the characteristics are not the same. With the difference of air pressure, ambient temperature, diesel quality and grade, the external characteristics and speed regulation characteristics of the engine will change. Especially near the maximum power point, sometimes the load torque will exceed due to the change of engine characteristics, resulting in a sharp drop in speed until flameout. In order to avoid this situation, the power absorbed by the hydraulic pump is usually set at 90% of the current maximum power of the engine when the power is matched, leaving a certain power reserve for the engine, but this causes the excavator can not work at full power and the work efficiency is low.
In the ideal state, the power reserve is cancelled, and the absorbed power of the hydraulic pump is set to be greater than or equal to the output power of the engine, so that the output power of the engine can be fully absorbed and utilized by the excavator. In this way, the problem of engine speed drop should be solved first, that is, when the load suddenly increases, the engine speed will not fluctuate too much. Therefore, the excavator power limit control is proposed. The control strategy is to set the initial absorbed power of the hydraulic pump to the maximum and detect the fluctuation of engine speed.
