【作者】 刘伟；

【导师】 杨华勇； 徐兵；

【作者基本信息】 浙江大学 ， 机械电子工程， 2012， 博士

【摘要】 液压控制系统是挖掘机的重要组成部分,其性能好坏直接关系到整机的操控性和节能性。传统负载敏感系统通过最高负载压力反馈实现系统的压力闭环控制,满足系统所需的流量和压力要求。而电液流量匹配控制系统采用开环控制的方式,在控制电比例泵输出系统所需流量的同时控制电比例阀动作,且不需要预设泵与最高负载之间的压力裕度。该开环控制方式提高了系统的柔性,增加了系统的控制自由度,使挖掘机的操控性和节能性进一步提升成为可能。电比例泵和电比例阀之间的流量匹配控制方法及其在工程机械中的应用,是电液流量匹配控制系统的研究重点和难点。本论文以典型负载敏感系统作参照对比,研究电液流量匹配控制系统的流量匹配控制方法和特性,并将电液流量匹配控制系统应用于2吨挖掘机试验样机,选题具有广泛的工程应用背景和重要的学术研究价值。本文提出一种基于压力流量的复合控制方法,基于该方法的阀前补偿多路阀电液流量匹配控制系统融合了电液负载敏感系统电反馈压力闭环控制和普通电液流量匹配控制系统流量开环控制的优势,可根据不同工况实现系统压力闭环控制和流量开环控制的切换。当系统过流匹配时,电液流量匹配控制系统选用压力闭环控制方式,否则选用开环控制方式。该控制方法解决了基于阀前补偿多路阀的电液流量匹配控制系统过流引起的系统溢流与能耗问题,并有效抑制了执行机构瞬间停止或切换产生的压力冲击。典型挖掘工况试验表明,与传统负载敏感系统相比,采用压力流量复合控制方法的电液流量匹配控制系统节能达10%,工作效率提高10%。本文研制了挖掘机电液流量匹配控制系统试验样机,建立了基于AMESim和Adams软件的相应虚拟样机软件平台。提出了一种基于旁路流量卸荷阀的流量控制方法,采用该方法的阀前补偿多路阀电液流量匹配控制系统在系统过流时,旁路流量卸荷阀开启卸荷过多流量,有效解决了系统溢流与能耗问题。与传统负载敏感系统相比,带旁路流量卸荷阀的电液流量匹配控制系统稳定性得到增强,压力裕度减小0.6～0.7MPa,阶跃动态响应时间缩短0.5s左右。另外,针对基于LUDV(德语：Lastdruck Unabhangige Durchfluss Verteilung;中文：负载独立流量分配)多路阀的电液流量匹配控制系统,提出了一种改进节能性的控制方法,该方法使最大流量需求执行机构对应的控制阀口全开,同时使其他执行机构的控制阀口开度根据操控指令按比例增大,从而降低阀口的压力损失。典型挖掘工况试验结果表明,与LUDV负载敏感系统相比,采用该控制方法的电液流量匹配控制系统压力裕度降低了约0.8-1MPa,节能达到12%。本论文研究成果为应用电液流量匹配控制技术改善挖掘机等工程机械的操控性和节能性提供了理论支撑和工程应用示范。论文的主要研究内容如下：第一章,介绍了现有挖掘机典型液压控制系统的原理及特性,并由此引出了新型液压控制系统——电液流量匹配控制系统；阐述了电液流量匹配控制系统的研究背景和国内外研究现状,指出了本课题的研究目的和意义,概述了本论文的主要研究内容。第二章,分析了基于阀前补偿多路阀的电液流量匹配控制系统原理及特性,研制了挖掘机综合试验装置和试验样机,建立了虚拟样机联合仿真模型,对比研究了系统的响应、节能和稳定性能。重点解决了系统的流量饱和和过流匹配控制问题,设计了抗流量饱和控制器,提出了压力流量的复合控制方法。第三章,阐述了带旁路流量卸荷阀的阀前补偿多路阀电液流量匹配控制系统原理及特性,研究了不同流量匹配关系对挖掘机控制特性和系统能耗的影响。试验分析流量饱和工况系统的控制特性,并设计抗流量饱和流量分配器。对比分析了带旁路流量卸荷阀的电液流量匹配控制系统与负载敏感系统的响应性、节能性和稳定性。第四章,分析了电液流量匹配控制系统的流量误差因素及其影响。试验研究了系统负载压力对电比例泵流量特性的影响,并采取了基于压力特性的开环流量补偿方法,通过试验数据表对系统流量进行线性插值补偿。为适应高精度系统和工况要求,提出基于油缸速度的间接流量闭环控制方法,并对挖掘机单执行机构动作和复合动作进行变负载、变速度工况特性试验研究。第五章,分析了LUDV多路阀电液流量匹配控制系统的原理及特性。以阀前补偿多路阀系统为对比,详细阐述了LUDV多路阀电液流量匹配控制系统的动静态流量与压力特性。建立了基于Adams和AMEsim软件的机液耦合仿真模型。提出了改进节能性的阀口控制策略,仿真与试验对比研究了LUDV负载敏感系统和电液流量匹配控制系统的响应、稳定和节能性。第六章,对本论文所作的研究工作进行总结,给出主要的研究结论,指出课题的创新点,并对未来的研究工作进行展望。更多还原

【Abstract】 Hydraulic system is an important part of excavator, and its performance is highly related to the operability and energy-saving of machinery. In the conventional load-sensing (LS) systems, the requirements of systems flow and pressure are met by closed-loop pressure control with the feedback of maximum load pressure. However, in the electrohydraulic flow matching control (EFMC) systems, when the electro-proportional valve opens, the electro-proportional pump supplies the required flow by open-loop flow control, and the pressure difference between the system pressure and maximum load pressure is not needed to be preset. Therefore, the flexibility and controllability of EFMC systems are improved. The control methods for flow matching between the electro-proportional pumps and electro-proportional valves are great challenges to mobile machinery. In this thesis, the characteristics and control methods of EFMC systems have been investigated and applied to a2-ton prototype excavator, as compared with the conventional LS system.In this thesis, a new method of pressure and flow compound control was proposed. Using the method proposed, the EFMC systems based upon pre-compensation multi-way valves had the advantages of closed-loop pressure control in electrohydraulic LS systems and the advantages of open-loop flow control in general EFMC systems. Therefore, the closed-loop pressure control and open-loop flow control could be chosen under different working conditions. When the flow of the EFMC system was excessive, closed-loop pressure control was used in the system, or alternatively open-loop flow control was adopted, hence the problems of energy loss and overflow could be solved. Moreover, the pressure shock of the system was effectively surpressed when the actuators instantaneously stopped or quickly switched. When compared with the conventional LS system in excavating test mode, the energy consumption of the EFMC system was reduced by10%and the efficiency was increased by10%in the EFMC system. An experimental prototype of a2-ton excavtor equipped with the EFMC system was developed, and a corresponding virtual prototype model was built based on AMEsim and Adams. Moreover, a new method for flow control was proposed by adding a bypass unloading valve in the EFMC system. According to the system pressure and maximum load pressure, the unloading valve could be opened to discharge excessive flow, hence the problems of overflow and energy loss could be effectively solved. Compared with the conventional LS system, the pressure margin of the EFMC system was reduced by0.6-0.7MPa and the step response time was shortened about0.5s in the EFMC system with the unloading valve, as well as the stability of the system was enhanced. Furthermore, a new control method for improving the energy efficiency has been proposed for the EFMC systems based on LUDV (Load Independent Flow Distribution) multi-way valves (LUDV-EFMC). Adopting the new method, when the flow demand of the actuator was highest, the corresponding control valve was fully opened, and the opening of the other valves were proportional to operator signals. The experimental results showed that, compared with the LUDV LS system in excavating test mode, the pressure margin of LUDV-EFMC was reduced by0.8-1MPa and energy consumption was decreased by12%in the LUDV-EFMC system. All research results could be used as references for the further investigation and application.The thesis is outlined as follows:In chapter1, the principles and characteristics of typical hydraulic systems in existing excvavtors were summarized, and a new kind of hydraulic system-the EFMC system was introduced. The research background and current research progress of EFMC systems were reviewed all over the world. Then, the main research objective, significance and topic of the study in the thesis were presented and discussed.In chapter2, the principles and characteristics of the pre-compensation EFMC (PC-EFMC) system were analyzed. The experimental prototype of the excavator was developed, and the virtual prototyping co-simulation model was built. The response, energy efficiency and stability of the PC-EFMC system were all investigated when compared with the conventional LS system. As key problems, the flow saturation and overhead flow matching control were solved. The controller with the capability of anti-saturation was designed, and the method of the pressure and flow compound control was proposed.In Chapter3, the principles and characteristics of the PC-EFMC system with an unloading valve as a bypass were analyzed in detail. The influences of different flow matching relationships on the operation characteristics and the energy loss of the excvavtor were studied. The system characteristics were experimentally investigated under the condition of flow saturation. The controller with the capability of anti-saturation was developed. The performance of response, energy efficiency and stability all were analyzed comparatively between the LS system and the PC-EFMC system with an unloading valve.In chapter4, the factors and impact of flow error in EFMC systems were analyzed. The influence of load pressure on the flow characteristics of the electro-proportional pump was experimentally studied, and an open-loop compensation method was presented to solve the effect based on pressure characteristics. With the experimental datasheet, the system flow was compensated by linear interpolation. To meet the requirements of high-precision system and working condition, a control method of indirect flow close-loop based on the cylinder velocity was proposed. Then, the velocity characteristics of single and compound action were experimentally investigated with different loads and reference velocities.In chapter5, the EFMC system based on LUDV multi-way valves (LUDV EFMC) was analyzed on the principle and characteristics. The dynamic, static flow and pressure characteristics of the LUDV EFMC system were studied in detail, as compared with the PC-EFMC system. Based on Adams and AMEsim, the simulation model of hydraulic-mechanical was built. A new control method for improving the energy efficiency has been proposed. Compared with the LUDV LS system, the response characteristics, energy efficiency and stability of LUDV EFMC system of the excavator were analyzed under the conditions of different actions and loads.In chapter6, all the research contents are summarized, and some new views are put forward in the future.更多还原