Research On Positive Flow Control System Of Electric Excavator Based On Variable Speed Control

Traditional engine-driven hydraulic excavators have problems such as high energy consumption,poor emissions,and high noise.With the gradual lack of resources and the continuous development of energy conservation and emission reduction and green environmental protection concepts,the use of new energy to replace traditional engines has become a hot research direction.At present,pure electric drive technology has certain advantages in improving vehicle emissions and energy efficiency.However,due to the essential difference between the structure and working conditions of the excavator,the electrification of the excavator needs to be redesigned.The existing electric excavator mainly uses the power motor to replace the engine,realizes zero emission,but does not exert the advantage of the power motor speed regulation performance,and the energy damage of the hydraulic system is still large,therefore,combined with the excavator system and work Characteristics,fully utilizing the advantages of power motors will help improve energy efficiency and system handling,and is of great significance to the development of electric excavators.The traditional electric excavator mostly adopts the throttle speed regulation system with constant rotation speed fixed displacement and constant speed variable displacement to realize the motion control of the excavator actuator.Among them,the fixed speed fixed displacement system cannot realize the hydraulic pump and the actuator.The flow between the two matches,causing a large amount of overflow loss.The fixed speed variable pump controls the movement of the actuator by changing the displacement of the variable pump to achieve the pump-load flow matching during operation.The variable pump has the disadvantages of low efficiency and small speed regulation range.Especially when the displacement is low,the efficiency of the variable pump is greatly reduced.Therefore,in view of the high energy consumption of the above electric excavators,a 1.5-ton excavator energy-saving system is taken as the research object.Based on the analysis of the traditional hydraulic excavator system,a positive-flow energy-saving control system based on variable speed is proposed.Combined with the relevant parameters of the 1.5-ton excavator,the parameters of the key components are optimized through theoretical analysis and calculation.The paper studies the flow control characteristics of the excavator multi-way valve,and proposes an actuator flow estimation method based on the handle output signal.Combined with the characteristics of the good speed regulation performance of the power motor,the positive flow of the electric excavator based on the variable speed is proposed.The control strategy of the system.According to the estimation of the flow required for the operation of the actuator,the output flow of the dosing pump is changed by changing the rotational speed of the power motor,thereby achieving the flow matching between the hydraulic pump and the actuator to reduce the energy loss caused by the overflow loss.Reduce system energy consumption.The paper further analyzes the relationship between the overload running times of the power motor and the safe running time.Based on the characteristics of the overloading operation of the power motor,the overload-based constant power operation strategy is proposed for the characteristics of the load fluctuation of a 1.5-ton excavator during operation.When the load suddenly increases,the motor runs at a constant power with a certain overload power.The motor speed decreases as the load increases,and a larger torque is output to overcome the load.By limiting the overload time,the constant power point is corrected to ensure the handling and safety of the system operation.The simulation study of constant power control strategy based on AMESim simulation model is established,and the feasibility of the scheme is verified.Based on a 1.5-ton excavator,a test platform was designed and built to test the flow matching mode and constant power mode based on variable-speed fixeddisplacement positive-flow system,and set the throttle speed regulation with the traditional fixed-speed fixed displacement.Comparative experimental study of control systems.Through the comparative analysis of the test results,it is found that in the operation of the positive flow system,energy saving can be achieved by 48.5%,and in the operation of the constant power mode,energy saving can be achieved by 33%,and the controllability and energy saving of the scheme are verified.