Research On Energy Transfermation And Its Control Strategy Of The Hybrid System In Hydraulic Excavator

As one of the widely used engineering machinery equipments,hydraulic excavator is characterized by high energy consumption and poor drainage.Researches on energy saving for the hydraulic excavator have important practical significances as far as the energy shortage and increasingly serious environmental pollution is concerned.From the current technology application of hybrid power can therefore be an effective way to save energy for the hydraulic excavator.Consideration of cost reduction and technical feasibility,this dissertation selects the lead-acid battery as auxiliary power source and intensively discusses the key issues in the hybrid power system and its control strategy of hydraulic excavator with power batteries.The main contents of researches are as follows.Fast charging technology for storage battery with Mass Theory.To take the battery as auxiliary power source for hybrid excavator,the first problems are charging slowness and short service life.Combined with Mass Theory,the fuzzy fast charging strategy with subsection optimization is presented.Taking chip TMS320F240 as the controller,the software and hardware of the charging and discharging systems are both designed to achieve the fast charging strategy.Simulation model of the storage battery is also established,and the difference between the load power with actual working conditions of 5t excavator and the average power of the engine as the input of the model.The results show that the charging strategy can effectively improve the battery charging efficiency,and greatly reduces the charging and discharging times of the battery.Estimation for residual capacity of battery with Grey Prediction.The estimation for battery residual capacity is always a difficult problem in battery controlling.Because of the severe loading conditions of the excavator,the battery which is the auxiliary power source of hydraulic excavator must withstand variable current in frequent during charging and discharging states.The estimation for residual capacity of battery is conversely difficult.Adopting the original data sequences of residual capacity in the actual hybrid excavator battery,the Grey prediction model with additive mean operator for the charging stage is proposed.In the discharging stage,the Grey prediction with variable weight and weak buffer is used for prediction and compensation of the load disturbances.The results illustrate that the proposed scheme can track the fluctuations of the original sequences of the residual capacity of the battery.Comparisons of comprehensive property of hybrid power system with mixed degree analysis.The scheme on the hybrid system structure of hydraulic excavator is analyzed and determined.The simulation model of the hybrid series system and parallel system of the hydraulic excavator are established respectively.The fuel consumption of series system and parallel system under different load conditions and mixed degrees are discussed.On the basis of these the dynamic parameter configuration of the two systems is optimized by the best saving energy mixed degree in overload condition,and he optimal dynamic parameters are therefore determined.According to the simulation analysis related with the actual situations of the series and parallel systems,the comparisons are carried out from the fuel consumption,engine operating points,and the changes of remaining power.Analysis shows that the comprehensive property of hybrid power system is better than the series system.Control strategy for parallel hybrid excavator with maximum efficiency.Control strategy researches are the key issues of hybrid power system.According to the actual working conditions of the excavator,the dynamic energy management strategy and the control strategy for charging and discharging operations with variable current of the battery are put forward with maximum comprehensive efficiency of the system.Experimental test platform is also set up to research the above strategy by simulating the actual condition.The studies reveal that the control strategy has a good energy saving effect and can evidently avoid the deep charging and discharging.The problems of slowness and deepness in charging and discharging exist in battery are settled by this dissertation effectively.Considering the overall efficiency of the hybrid system,the control strategy effectively improves the energy saving of the system.