摘要
多路阀作为挖掘机上的关键部件,它的性能与功能直接决定了挖掘机的性能与功能。目前国内市面上的中小型挖掘机用多路阀绝大多数都具有两个特点:一是非电控形式,即对多路阀的操作都是手动直接操纵阀芯动作;二是单阀芯控制方式,即执行机构的进油和回油都是通过一根阀芯来控制。这些特点使得挖掘机难以实现大幅度节能、远程遥控作业、机群协同作业等功能。本课题的研究对象是国内最新引进的一款基于负载口独立控制的挖掘机用新型电液比例多路阀,由于它采用了新颖的结构设计,融合了电子技术,为挖掘机的大幅度节能和远程遥控作业等智能化操作提供了前提条件。本文在建立阀的数学模型的基础上,对其控制策略展开研究,为该阀在国内的设计、生产提供理论指导。
本文结合液压挖掘机分析研究了该阀的结构组成、工作原理以及相关的硬件软件构成,并将该阀与传统换向阀对液压执行机构的控制方式进行了比较,指出该阀在控制液压回路上比传统换向阀显示出更大的灵活性。以流体力学和经典控制理论为基础,建立了该阀的数学模型,指出了该阀在先导阀-主阀环节的传递函数与经典阀控对称缸传递函数的差别,对该阀的动态特性进行了分析,讨论了影响该阀动态特性的主要参数;在此基础上,提出使用常规PID控制策略对该阀的主阀芯实施位置控制,仿真结果表明常规PID控制策略适应性不好,难以满足控制要求。引入模糊控制策略,设计了模糊控制器,常规模糊控制的仿真结果表明使用模糊控制策略对主阀芯位置进行控制是可行的,且系统的动态响应品质较好,但是存在较大的稳态误差;基于规则修改的模糊控制对系统的动态响应品质有所改善,但是仍不能消除稳态误差;Fuzzy-PID双模模糊控制器结合了模糊控制和PID控制的优点,系统不仅具有较好的动态响应特性,而且彻底的消除了稳态误差。以铲斗液压操纵回路为代表,建立了该阀及其相关挖掘机液压系统的Amesim/Matlab联合仿真模型,通过实验检测铲斗油缸大腔、小腔压力并与联合仿真模型的仿真结果对比分析,验证了联合仿真模型的正确性,同时也间接证明了该阀采用Fuzzy-PID双模模糊控制策略是行之有效的。
As the key part on the excavator, the multitandem valve's performance and function directly determine the performance and function of the excavator. Most of the multitandem valves used on the excavator in domestic market have two characteristics. The first characteristic is non-electronic-control, that means the operation of multitandem valve is done via directly controlling the spool by hand. The second characteristic is single spool control mode, that means the oil which flow in and out the actuator is controlled by one single spool. These two characteristics make the excavator hard to fulfill large-scale energy saving, and other performance like remote control task and excavator group cooperation task. The paper has done some research on a new type of electronic-hydraulic proportional multitandem valve based on independent control of actuator ports, which is a latest overseas production used on the excavator. For adopting a creative structure design and integrating the electronic technology, it can provid the excavator's large-scale energy saving and intelligence operation like remote control with premise condition. Based on establishing the mathematical model of the valve, the paper did research on its control strategy, which could provide instruction for the valve's designing and production in home.
Combined the excavator, analyzed the structure construction, work principle of the valve and the relevant hardware and software construction,made a comparison research on the control mode of the hydraulic actuator between the valve and the traditional change valve, pointed out that the valve is more flexible than the traditional change valve on controlling the hydraulic loop.Based on hydrodynamics and classical control theory, established the mathematical model of the valve, pointed out the difference between the transfer function of pilot valve to main valve and the transfer function of classical valve control symmetry cylinder, analyzed the dynamic characteristic of the valve, discussed the main parameters that influence the dynamic characteristic of the valve. On the basis of this, put forward the opinion that use normal PID controller to control the displacement of the main spool, the simulation result show that the adaptability of PID control is not good and hard to meet the control demands.Introduced fuzzy control strategy, designed a fuzzy controller.The simulation result of normal fuzzy control strategy show that it is feasible to use fuzzy control strategy to control the displacement of the main spool, and the dynamic response quality of the system is fairly good,but there is a big steady state error.The fuzzy control strategy based on modifying fuzzy rules can improve the dynamic response quality of the system, but also can not eliminate steady state error. The Fuzzy-PID dual-mode fuzzy control strategy combined the virtue of fuzzy control and PID control, the system not only has a good dynamic response quality, but also eliminate steady state error thoroughly. As the bucket hydraulic loop for representation, established a Amesim/Matlab union simulation model of electronic-hydraulic proportional valve and the relevant excavator hydraulic system. Through testing the piston chamber pressure and the rod chamber pressure of the bucket actuator and comparing it to the simulation result, testified the correctness of the model, meanwhile, it also indirectly proved that Fuzzy-PID dual mode fuzzy control strategy can be used on this valve.
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