Hydraulic Hybrid Excavator Differential Pressure Comoensationai Energy Recovery System And Power Control Research

Hydraulic excavator was the very important construction machinery for the national economic development. Its energy saving, emission reduction had extraordinary economic and environmental significance. The innovation of conventional component technology and improvement of the excavator hydraulic system had been matured almost. But the in-depth research on hybrid technology offered a new breakthrough for the excavator energy saving. Currently, the research of the electrical hybrid was more widely on the vehicle and some mature product had been manufactured. On the excavator, the research of the electrical hybrid technology also was the most attractive. On the contrary, the research of the hydraulic hybrid technology was scarcity. There were few research literatures from institutes and universities. Only some large international excavator corporation had begun the study of hydraulic hybrid technology on the excavator and took an optimistic view about the prospects for its application. But their research information was kept confidentially. Overall, the research of the hydraulic hybrid technology was still in its infancy and had fewer achievements. In this thesis, in order to further in-depth research and make some contribution, we considered the application of the hydraulic hybrid technology on the excavator as the main task, combined the hybrid technology with the energy recovery during the excavator working as the dynamic energy recovery system, took research on the composite structure designing, system modeling, components parameter matching and machine control method, established the appropriate experimental platform for authentication.The main research areas in this thesis included the following aspects:1. Based on the general structure and working conditions of the hydraulic excavator, the series, parallel and the mixture type of the hydraulic hybrid system were compared, and the parallel type was selected as the main study structure. The low cost double rotary motor was used to replace the high cost secondary hydraulic component for realizing the hybrid function by redesigning the parallel structure.2. Fully automated solutions were designed for excavator potential energy and kinetic energy recovery. The solutions combined with the hydraulic hybrid system were called as the dynamic energy recovery system. And the principle and control method of this new system were explained. The new dynamic energy recovery system could overcome the restrictive conditions, improve the efficiency of the energy recovery course, and reduce the loss.3. A new parameters matching method for the hydraulic hybrid system was presented. The accumulator was taken as the core component during the matching course to overcome the disadvantage of the hydraulic hybrid technology which was in low energy density and meet the power demand of the excavator working conditions.4. By analyzing and comparing the existing control strategies, the double speed point control strategy which was suitable for the hydraulic hybrid system was chosen. On this basis, variable parameter PID control, load forecasting, and the engine idling switch methods were proposed to stabilize the single speed point steady. By genetic algorithm to further improve the overall energy savings, a20%fuel savings was gained.5. A parallel hydraulic hybrid test platform was designed and established to verify the control method mentioned above. And the platform also could provide the criterion for the future control method.