| The electro-hydraulic power source consists of an electric motor and a hydraulic pump and it is used to provide power for a hydraulic system.The hydraulic pump is a core component in the electro-hydraulic power source and its major constituents include the piston pump,gear pump and vane pump.In comparison with other hydraulic pumps,the axial piston pump is superior because of its high pressure,high efficiency,long life and easily-controlled variables.The electric motor is used as the driving device of the electric-hydraulic power source,which drives the hydraulic pump to rotate.Through the electric motor to change the speed of the pump,the power consumption of the system could be further reduced.Along with the enhancement of people’s environmental awareness and the rapid development of industry,the requirement towards a highly energy efficient hydraulic power source is in increasing demand.It needs not only to reduce the loss of system energy consumption by changing speed,but also to further optimize the structure of the axial piston pump to achieve small flow pulsation,low noise requirements.In this dissertation,the research is based on two parts: optimizing the structure of the axial piston pump and driving the proportional constant pressure pump with variable speed.This thesis is supported by the National Natural Science Foundation Project(51575374 and 50775156).This thesis conducts the research from the perspective of energy-saving of electro-hydraulic power source,the optimizing the port plate structure of piston pump and variable speed control piston pump are put forward to construct low power consumption power source.In order to achieve this goal,based on the theoretical analysis,the research is developed from three aspects,modeling analysis,simulation calculation and experiment.The program of flow area is designed in MATLAB and the simulation model of plunger pump is established in AMESim.The accuracy of the model is verified by test method.Then the model of piston pump is further optimized.After simulation,trial manufacture and test,the three-port axial piston pump is successfully developed.The three-port axial piston pump has a considerable performance with the double-pump.On the basis of the study,the characteristics of the variable speed electro-hydraulic power source were studied.Based on the theoretical research and simulation model,the test bench was set up.Variable frequency motor and servo motor were used to drive the proportional constant pressure pump to realize the pressure and flow compound control and the energy consumption is further reduced in non-working time.The contents of this dissertation are as follows:In Chapter One,it mainly introduced the background of the study,and summarized the literature review on the current studies of the energy-saving noise reduction axial piston pump.It was concluded that the major method towards energy-saving and noise reduction was to optimize the flow structure.Furthermore,we analyzed the development of the axial piston pump variable rotating speed and variable displacement controlled hydraulic power source.From the current study and the literature review,we coined the idea of structuring the variable rotating speed controlled proportional constant pressure pump as the electric-hydraulic power source.In Chapter Two,an axial piston pump simulation model was established based on the single plunger model,variable mechanism dynamic model and kinematic pair leakage model to investigate the pressure fluctuations and power testing.The study showed that when the output flows were consistent,with the rate of change in the variable rotating speed pressure fluctuations smaller than the variable displacement;when the variable rotating speed was combined with the variable displacement to control the system,the pump with a high rotating speed and a small displacement had a small pressure fluctuation.In contrast,the pump with a low rotating speed and a large displacement had a lower energy consumption level.The flow structures of the axial piston pump were further optimized to deliver a smaller outflow fluctuation,hence improving the volumetric efficiency.In Chapter Three,it dealt with the energy efficiency in a low idle rotation hydraulic system.The inverter,three-phased induction motor drive and proportional constant pressure pump constituted electric-hydraulic power source were mainly applied in a large power hydraulic system.Under the pressure holding condition,the rotating speed of the electric motor was reduced from 1,500 r/min to 300 r/min,and the energy consumption level by 31%;Under the constant pressure mode,the rotating speed of the electric motor was decreased from 1,500r/min to 450 r/min,and the energy consumption level was decreased by 3 kW under variable rotating speed and displacement.The result revealed that the total energy consumption level was greatly reduced through the low idling system.The auxiliary improvement of the pump was achieved by adding an accumulator in the main circuit,which solved the problem of the poor system flow dynamic properties during the frequency conversion process.It reduced the starting time of the inverter from 1 s to 0.2 s,and the stopping time of the inverter from 1.2 s to 0.7 s.According to the simulation and experimental analysis,such power source could fulfill compound control,fast response and high energy efficiency,thus completely replacing the P-Q pump.Furthermore,the closed loop control enabled a system flow error of less than 0.5% under the pressure-loading disturbance,which could achieve constant power control.In Chapter Four,we tackled the achievement of the high energy efficiency in low idling of the electric motor through the servo motor and proportional constant pressure pump comprised electric-hydraulic power source.Such power source was mainly applied in a high control precision and small power hydraulic system.The rotating speed and output dynamic response of the servo motor were fast and highly precise,so the system had a fast flow control dynamic response.Furthermore,the PD control was applied to the system pressure,resulting in a fast response,small overshoot and strong anti-interference ability.The impact of the change in the loading pressure on the system output flow could be neglected through the compensation control of the rotating speed of the servomotor.Moreover,the use of a combination of the proportional constant pressure pump and variable rotating speed was also capable of fulfilling high energy efficiency under mixed conditions such as high pressure small flow,pressure holding,variable displacement and rotating speed.Based on the simulation and experimental testing,such electro-hydraulic power source could completely substitute the electro-hydraulic proportional pump,which in turn reduced the costs of the entire system.In Chapter Five,we aimed to solve the problem of the asymmetry of the flows of the duo chambers within the closed circuit pump control differential cylinder.The idea was to alter the flow structure based on the original axial piston pump model.The major approaches included adjusting its flow kidney-shaped plate groove to have one side as inner and outer rings in parallel groove,and the other side as a three-port flow structure consisting of a single kidney-shaped groove flow plate.The flow structure was then optimized,based on the theory of the asymmetry of the simulation experiment;the three-port pump’s viability was assessed through simulated model.In light of this,with reference to A10VSO-45 axial piston pump’s structure,we designed the flow structure,oil suction structure,cover and other corresponding parts and underwent trial tests.Such three-port pump was superior to the referred original pump in pressure fluctuations,volumetric efficiency,noise level and many other parameters.It made it suitable for the power source of the pump control differential cylinder and also simplified the hydraulic system structure.Therefore,the goal of energy efficiency was reached.In Chapter Six,we drew a conclusion of the dissertation.It also pointed out the innovative points in the dissertation and addressed how the future study can be carried out. |
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