【作者】 王艳伟；

【导师】 刘顺安；

【作者基本信息】 吉林大学 ， 机械电子工程， 2008， 硕士

【摘要】 本论文主要是针对液压挖掘机负荷传感系统进行的研究。首先分析了液压挖掘机液压系统的能量损失原因,本文提出了基于模糊控制策略的液压挖掘机电液负荷传感系统。其次对闭心式负荷传感系统的工作原理进行了分析和仿真研究,深入了解了系统内部的压力和流量关系,以及各元件在整个系统中所起到的作用和各参数对系统的影响,仿真结果表明原理分析正确。在此基础上对液压挖掘机负荷传感系统进行了电控改造,提出基于高速开关阀控液压泵变量缸的电液负荷传感系统,并对电液负荷传感泵控系统进行了数学建模,通过仿真分析了系统的动态性能。在综合考虑各种控制方法优劣的基础上,选用模糊控制策略作为系统的控制方法,并建立AMESim和MATLAB的联合仿真平台,对系统进行了仿真研究,结果表明模糊控制器设计效果较好,整个系统满足设计要求,在理论上是可行的。最后,搭建了电液负荷传感系统模糊控制实验台架,进行了高速开关阀的空载流量测试和模糊控制器控制效果实验。更多还原

【Abstract】 With the oil resource dwindling and people’s awareness of environmental protection increasing, major manufacturers of construction machinery take the electronic saving energy control technology as the main development direction. According to statistics, the average energy utilization rate of hydraulic excavator is only about 30 percent. Face such tremendous energy loss, the energy-saving technology has become a research hot of excavators. And as more and more electronic technologies introduced into the field of hydraulic excavator system, electronic energy-saving control technology has become one of the key development directions of hydraulic excavators.In this paper, the MATLAB and AMESim joint simulation platform is introduce- d into the research of the excavator’s hydraulic system. And using this simulation platform, models for the hydraulic and control part of the electro-hydraulic load-sensing system are built. In the process, good points of software in modeling、simulation and data processing are made full use and the foundation work for the intellectualization of hydraulic excavators is done.Hydraulic excavator is a kind of construction equipment with high power, and the energy saving controls will directly affect the economics and reliability of the excavators. This article mainly researches load sensing system’s energy saving and maneuverability of the hydraulic excavator. Through reducing the power loss on each link of the hydraulic system, we can reach the purpose of reducing heat generation and saving fuel consumption of the hydraulic system, and improving the manipulation performance of the excavator at the same time. Present research situations and development trend of hydraulic excavator’s load-sensing system are analyzed comprehensively. Also the working principle of closed load-sensing system is analyzed and simulated. Based on these, a method of electro-hydraulic load-sensing system is presented. This system controls hydraulic pump and variable cylinder by high-speed switching valve. In this paper, both PID control and fuzzy control are used. And their different effects on system are compared. Results show that the effect of fuzzy control is better. Finally, the electro-hydraulic load-sensing system based on fuzzy control is experimentally studied.Full text is divided into following parts:1. The energy loss of hydraulic excavator is analyzed. According to the hydraulic excavator’s technical requirements on hydraulic system, we know that the hydraulic load-sensing system is an ideal hydraulic system for excavator. Its development condition is summed up.2. The working principle of load-sensing system of excavator is analyzed. For understanding the influence of various inherent parameters on system, the simulation research is carried on through the AMESim software. In the load-sensing system of hydraulic excavator, the system can track the pressure difference value P of the highest load loop. In order to maintain a fixed value of P on valve orifice, pressure compensation is required for low pressure loops. But when the system achieve to the flow saturation, pressure difference P on valve orifice will change along with orifice’s opening degree of the throttle valve. So the system can prorate flow. The load-sensing pump-control system and load-sensing valve-control system are combined in hydraulic excavator. In this way, the best flow supply and good operability on hydraulic excavator are realized and hydraulic system’s performance is optimized.3. Electronic transformations of the load-sensing pump-control system are put forward in this paper, which replace the machine-fluid servo valve with high-speed on-off valve and convert pressure signals to electrical signals. After these, the response time、control accuracy and reliability of the system are improved. Also mathematical models of the system are established. Simulation analysis shows that when design the system, we should make effort to eliminate system steady-state error. Doing this can reduce the complexity of the control algorithm effectively and improve the stability、accuracy and response time of the system.4. In addition to methods design and reasonable selection of components, controller design plays an important role in the control accuracy and working reliability of the electro-hydraulic load-sensing system. So advanced control strategies should be adopted to solve all kinds of practical problems. Because the control strategy is the core of control technologies of the whole system and has great influence on load-sensing system’s performance, the research of control strategies of electro-hydraulic load-sensing system is meaningful. In this paper, the fuzzy controller of the electro-hydraulic load-sensing system is designed based on the fuzzy control theory.5. Joint simulation platform has been introduced into the simulation research of the load-sensing system of hydraulic excavator. This platform combines the hydraulic simulation software AMESim and the control simulation software MATLAB. In this paper, the simulation model of electro-hydraulic load-sensing system is established using software’s respective advantages. Also the PID controller and the fuzzy controller are designed and simulation results of two kinds of controllers are compared. Results indicate that the effect of the fuzzy controller is better and the entire system can meet design requirements and is feasible in theory.6. Combined contents of the paper, the experimental gantry is built under existing conditions in the laboratory. And corresponding hardware and software of the control system are designed. The empty-load flow measurement of the high-speed switching valve and the control effect experiment of fuzzy controller are carried on in the experimental gantry. Results show that the high-speed switching valve has good linearity and the fuzzy controller can meet the stability of the system.更多还原