Research On Control Features Of Distributed Variable Displacement Hydraulic Hybrid System

With the environment and energy issues becoming more and more critical,the new energy technology exerts an increasing tremendous fascination on people(is preferred by people increasingly).As a crucial branch in the field of new energy,the hydraulic hybrid system has great potential in saving energy.Nowadays it generally uses variable piston pump/motor to be the core component of the hydraulic hybrid system.Due to the fact that the core component has a multitude of disadvantages such as slow response rate,poor anti-interference performance,poor reliability and extremely high cost,it greatly limits the promotion and application of the hydraulic hybrid technology.The development of digital electronic technology makes the integration;the lightweight,low energy consumption and high reliability of the communications equipment keep improving.At present,the digital technology has become the mainstream in the automatic control field and more and more industrial products are changing to digital direction.Introducing discretization thought to the hydraulic variable control system.On the one hand,it can reduce the cost;improve the reliability of hydraulic system.On the other hand,it can make the control principle in line with the physical properties of the hydraulic components and also it can improve the control precision and rapidity,especially it can solve the minimum controllable displacement of the variable pump and variable zero point jitter problem of the secondary component completely.In this dissertation,it based on the distributed variable secondary component to put forward a distributed variable displacement control according to the distributed control theory and the digital electronic technique.Combined with the project supported by the National Natural Science Foundation of China " Distributed Variable Displacement Hydraulic Impact Mechanism and Its Inhibition in Hydraulic Hybrid System"(Fund Number:51405183),this dissertation researches on the control features of the distributed variable displacement hydraulic hybrid system.By analyzing and studying the hydraulic hybrid system in depth,it shows the traditional hydraulic control system uses the speed control mode mostly which is based on flow control.however the control system is complex and control parameters are unstable under the complex and multi-load condition,Therefore,the distributed variable hydraulic hybrid system in this dissertation adopts distributed variable torque control.Compared with the traditional hydraulic control system,torque control has a multitude of advantages such as multi-load coordinated control,simple system structure,high efficiency and energy saving,but meanwhile the interference caused by pressure fluctuation in the torque control is more direct.Therefore,it is indispensable to analyze the torque impact phenomenon caused by pressure fluctuation in depth.According to its mechanism,improve the control algorithm and optimize control structure to acquire superior control quality of the distributed variable hydraulic control system.This dissertation combines the three ideals of theoretical models,simulation analysis and experimental research by constructing the mathematical model of the main components in the distributed variable hydraulic hybrid system,deducing mathematical formula,designing torque control algorithm and making mathematical analysis about energy conversion and regeneration of the system.It provides a theoretical basis for the distributed variable hydraulic hybrid system.It uses AMESim platform to create the models of the distributed variable hydraulic hybrid system.Based on the theoretical work analyze the simulation results under different conditions,which verify the correctness of the theoretical model.Furthermore,it can obtain the affect on the quality control system from different parameters in the system and improve the parameters matching principle to adapt to the multi working conditionsOn the basis of simulation analysis,a semi physical simulation experiment platform with distributed variable hydraulic hybrid system is developed on the platform of light-duty trucks,carry out some experimental examines on the simulation experiment platform under different conditions and observe the capacitive and inductive loads’ effects on the quality control system.Analyze and improve the impact and buffeting phenomenon,low speed brake hysteresis system;Grasp the response regularity by establishing dynamic model of reversing valve group;Add the step sequence consistency compensation algorithm to the distributed variable control system to improve the torque impact caused by the pressure jump.Moreover,through the in-depth analysis of the secondary component,extend the distributed variable combination sequence reasonably,reduce the minimum step variable gradient and decrease the pressure overshoot by using the phenomenon of working pressure compatibility,which can improve the system-buffeting phenomenon and optimize the control quality of the distributed variable control system.Furthermore,it lays the foundation for its application.The proposed research will offer a theoretical basis for realizing full digitalization of hydraulic system,and develop a new approach to the hybrid and energy saving technique in hydraulic system.