| Since the advent of hydraulic excavator,it has been widely used in all kinds of excavation construction occasions,and it has become one of the most important construction machinery.Because of the overall efficiency of the traditional fuel excavator is low,which will cause a lot of noise pollution and air pollution in the excavation operation,and it is not suitable for the construction operation of hospitals and tunnels and other special occasions,so electric excavator is bound to become the future development trend.Yet the traditional constant speed volumetric speed control system has a fixed motor speed and low motor efficiency,so improving the efficiency of electric excavator has become a new development direction of electric excavator.In order to improve the efficiency of the motor and reduce the overflow loss of the hydraulic system,this paper takes an electric excavator as the research object,and studies the power matching between the motor and the fixed displacement pump,and the electro-hydraulic flow matching of the hydraulic system.Firstly,the advantages and disadvantages of common power supply schemes and power source speed control system of electric excavator are compared and analyzed.A general scheme of using mobile power vehicle as power supply mode and frequency conversion speed control of asynchronous motor to drive quantitative pump is proposed,and a set of electro-hydraulic flow matching control system scheme based on pump valve synchronization is designed for the excavator.Secondly,the power loss of the asynchronous motor is analyzed.Through the analysis of the T-shaped equivalent circuit of the asynchronous motor,the mathematical model of the efficiency of the asynchronous motor is derived.In order to improve the efficiency of motor frequency conversion operation,a power matching method of motor and quantitative pump based on the optimal efficiency of motor is proposed,so that the output flow of hydraulic pump can meet the demand of hydraulic system,and the efficiency of motor is optimal.Then,In order to reduce the overflow loss of hydraulic system,according to the working principle of the LUDV multi-way valve,a method of matching the electro-hydraulic flow of the LUDV system is proposed.According to the signal value of the handle,the target speed of each actuator and the total demand flow of the system are calibrated,and the demand speed of the motor is obtained.The target speed of the motor and the set pressure of the main relief valve are controlled according to the relationship between the demand speed and the limit speed at 600r/min and 1800r/min of the pump.At the same time,the preset pressure drop of main valve is 1.9MPa,and the spool displacement of LUDV multi-channel valve is controlled to make corresponding changes,so as to realize accurate flow matching and reduce the overflow loss of the system.Finally,the co-simulation model of electro-hydraulic flow matching control of excavator LUDV system is established by using AMESim and MATLAB/Simulink software,and the co-simulation analysis of the system is carried out.The simulation results show that:（1）when the demand speed n0 is less than 600 r/min,the pump output flow is greater than the system demand flow,and the setting pressure of the main relief valve is 1.9 MPa higher than the load sensing pressure,so that the excess flow overflows from the main relief valve,and the movement speed of the actuator is equal to the target speed;（2）when 600 r/min≤n0≤1800 r/min,the pump output flow is equal to the system demand flow,the actuator moves according to the set target speed,and the system has no overflow loss;（3）when n0>1800r/min,the system flow is saturated,at this time,the system has no overflow loss,the movement speed of each actuator decreases proportionally at the same time,and the movement of the actuator will not interfere;（4）after the efficiency optimal control of the motor,the efficiency of the motor is higher than that before the optimization,and the energy saving of the system is improved. |
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