Research On Control Characteristics And Application Of Digital Pump Based On Discrete Variable Technology

Hydraulic transmission and control as one of the key technologies for transmission and motion control of large equipment is widely used in key fields such as manufacturing,aerospace,and construction machinery.The hydraulic pump is an important core component of the hydraulic system,which directly affects the efficiency of the hydraulic system and the performance of the whole machine.With the rapid development of science and technology,the technical requirements of hydraulic systems have been continuously improved.Traditional hydraulic pump systems are sensitive to pollution,low in efficiency,susceptible to interference and other control problems becoming increasingly prominent,which cannot meet the technical requirements for high reliability and high-performance hydraulic control systems in related application fields.Therefore,carrying out the research work of the new hydraulic pump system is the key technical way to break through the bottleneck of the function and performance of the existing hydraulic system.Compared with traditional hydraulic technology,digital hydraulic technology has certain advantages in anti-interference,energy saving,fault tolerance and versatility.Parallel digital pump is a new type of variable displacement pump discrete displacement control with religious application prospects.However,there are still deficiencies in the research on its variable control method,variable shock suppression method,and fault tolerance.This thesis was supported by the National Natural Science Foundation of China “Research on the Formation Mechanism of Discrete Variable Control Hydraulic Shock and Its Suppression Method”(No.51405183)and the Ministry of Industry and Information Technology’s project “Digital Hydraulic Technology Innovation for Advanced Construction Machinery and the Construction of Industrial Technology Public Service Platform”(No.2020009611).Related researches are carried out on the characteristics and applications of digital pump variable control,and the digital pump variable control method and variable shock suppression method are proposed,the digital pump steering hydraulic system and its control strategy are constructed,the fault tolerance performance of the system is studied.The research on the combination of system theory-bench-vehicle experiment provides a theoretical basis and application basis for the application of discrete digital pumps.The main research work are as follows:A digital pump variable control method based on flow discrete technology was proposed.The variable mechanism of the digital pump was clarified,and the coding method of the displacement of the digital pump unit is determined.To improve the antidisturbance of the displacement change of the digital pump,a variable-threshold hysteresis control method based on the extended state-number phase plane partition was proposed,and the feasibility of the proposed control method and the digital variable method was verified by simulation and experiment.At the same time,it was found that when the state changes of multiple pump units were in opposite directions,a relatively obvious variable shock phenomenon would occur,which points out the direction for the follow-up research work.The method for suppressing the variable shock of digital pump was studied.It was proposed that the control configuration based on dual mode can significantly improve the displacement control accuracy under the same number of combined units,thereby reducing the variable impact amplitude.A timing compensation control strategy based on NSGA-II algorithm to identify the optimal delay time was proposed,and the time parameters were optimized through multi-software co-simulation.The torque and pressure shock were reduced by 34.83% and 17.51%,respectively.The accumulator was used to further smooth the pressure impact,and the key parameters were optimized through orthogonal experiment.A digital pump steering hydraulic system and its control strategy were proposed.To achieve the balance control between system energy consumption and pressure fluctuation,a displacement control strategy based on model identification and cost function was proposed.To further improve the applicability of the control strategy,a flow matching and feedback control strategy for the phase plane partition of the extended state number based on deviation control was proposed.The control parameters of the phase plane partition were optimized by the fuzzy controller.The variable threshold hysteresis control and time sequence control were used to realize the smooth matching control of the flow.For the problem that the system cannot respond quickly to the reverse deviation,the limiting and anti-saturation control were proposed.The results showed the effectiveness of the designed control strategy above,and the proposed digital pump variable system was remarkable.The fault redundant control countermeasure of digital pump steering hydraulic system was proposed.The fault reconstruction scheme of the pump unit pressure buildup and pressure relief were analyzed respectively,and the fault redundancy control countermeasure was proposed based on the parameter measurement method.The simulation analysis verified that the digital pump steering hydraulic system can identify the fault and automatically the online mode switch which can be used for emergency steering and improve the survivability of the system.The experimental bench and loader prototype were independently developed and the performance of the steering hydraulic system with digital pump was verified.The experimental bench of the digital pump steering system and the prototype of the loader were built.The control system and the selection of key components were designed.The effectiveness of the proposed displacement feedforward control strategy based on model identification and cost function,the flow matching and feedback control strategy based on ESPPD,and the fault redundancy control strategy were verified by experiments.