液压缸制动过程中能量回收系统的研究

发布时间：2018-04-26 10:48

  本文选题：制动过程 + 动能回收　； 参考：《太原理工大学》2017年硕士论文

【摘要】：工程机械中,如挖掘机、装载机等常常由液压缸驱动,这些液压缸频繁的启动与制动,为了防止制动过程中的冲击,液压缸通常采用液压制动阀进行制动。系统在制动时动能会以热能的形式耗散在节流口上,从而导致油液的温度升高,制动性能下降。特别对需频繁制动的系统影响更大。采用液压阀制动的同时会造成大量的能量损失,不利于节能。为了使执行元件快速平稳的制动,尽量减小缓冲腔的压力冲击,并把制动过程的能量进行回收再利用,国内外学者做出了很多研究。如从提高发动机燃油效率、改进液压系统结构和优化发动机-负载功率匹配控制策略等角度进行分析,但制动过程中能量损问题依旧存在。针对需频繁启动与制动的高速重载液压系统存在的制动冲击和能量损耗问题,首先对现有的制动系统进行归纳整理,结合负载敏感双向制动回路的结构特点及工作原理,提出一种以蓄能器为储能元件,通过蓄能器压力控制液压变压器中变量泵的排量,使负载达到平稳制动和能量回收的系统。画出原理图,并结合数学模型阐述了系统的工作原理和控制方法。利用这种无节流损失的控制方式有效的降低了压力冲击和能量损耗。在满足制动特性,同时兼顾能量回收效率的前提下,对制动回路中的主要元件蓄能器、液压变压器、切断阀做出基本介绍,分析其工作原理和数学模型,并进行选型和参数的匹配,对切断阀的结构进行设计,画出结构原理图,最后通过液压变压器、蓄能器、切断阀相互配合,满足系统的要求。给定工况的条件下,在AMESim软件中对制动能量回收系统进行仿真,设置系统参数,得到液压缸制动腔及蓄能器压力、变量泵排量变化、蓄能器体积等的仿真曲线图,分析结果表明该系统能实现负载的快速平稳制动并回收大部分动能。文中还讨论了在不同负载质量、不同初速度的情况下系统的制动特性和能量回收效率,研究结果表明,该系统对不同工况具有较强的适应能力。与负载敏感制动系统进行对比,充分证明了新型系统的在制动和能量回收方面的优越性。指出影响系统的能量损失和能量回收效率的因素,主要包括机械摩擦损失、泄漏损失、粘性阻尼损失及控制过程中的损失等。对其进行分析计算,得到系统能量回收的总效率达63.24%。在通过对系统模型进行仿真,详细分析和研究液压变压器排量、减速器的转动惯量、蓄能器的初始压力及体积、切断阀的参数设置对制动能量回收系统的具体影响,对最终液压元件参数的优化和确定提供理论依据。
[Abstract]:In construction machinery, such as excavators, loaders and so on, often driven by hydraulic cylinders, these cylinders frequently start and brake, in order to prevent the impact of the braking process, hydraulic brake valves are usually used to brake the cylinder. The kinetic energy of the system will be dissipated on the throttle in the form of heat energy during braking, which will lead to the increase of oil temperature and the decrease of braking performance. Especially for the need for frequent braking system more impact. The use of hydraulic valve brake will cause a large amount of energy loss at the same time, which is not conducive to energy saving. In order to make the actuator brake quickly and smoothly, reduce the pressure shock of the buffer chamber as much as possible, and recycle the energy of the braking process, scholars at home and abroad have made a lot of research. For example, from the point of view of improving engine fuel efficiency, improving hydraulic system structure and optimizing the control strategy of engine load power matching, the energy loss problem still exists in the braking process. Aiming at the problems of braking shock and energy loss existing in high speed and heavy load hydraulic system which need to start and brake frequently, the existing braking system is summarized and sorted, and combined with the structural characteristics and working principle of load sensitive bidirectional braking circuit. A system is proposed in which the accumulator is used as the energy storage element and the displacement of the variable pump in the hydraulic transformer is controlled by the accumulator pressure, so that the load can achieve a steady braking and energy recovery. The working principle and control method of the system are described by drawing the schematic diagram and combining with the mathematical model. This control method with no throttling loss can effectively reduce the pressure shock and energy loss. On the premise of satisfying the braking characteristics and taking into account the efficiency of energy recovery, the main components of the brake circuit, accumulator, hydraulic transformer and cut-off valve, are introduced, and their working principle and mathematical model are analyzed. The structure of the cut-off valve is designed, and the schematic diagram is drawn. Finally, the hydraulic transformer, accumulator and cut-off valve cooperate with each other to meet the requirements of the system. Under given working conditions, the braking energy recovery system is simulated in AMESim software, and the system parameters are set up. The simulation curves of brake chamber and accumulator pressure, variable pump displacement, accumulator volume and so on are obtained. The analysis results show that the system can realize fast and steady braking of load and recover most of kinetic energy. The braking characteristics and energy recovery efficiency of the system under different load mass and different initial speed are also discussed. The results show that the system has strong adaptability to different working conditions. Compared with the load sensitive braking system, the advantages of the new system in braking and energy recovery are fully proved. It is pointed out that the factors affecting the energy loss and energy recovery efficiency of the system mainly include mechanical friction loss, leakage loss, viscous damping loss and loss in the control process. The total energy recovery efficiency of the system is 63.24. Through the simulation of the system model, the effects of hydraulic transformer displacement, the moment of inertia of reducer, the initial pressure and volume of accumulator, the parameter setting of cutting valve on the braking energy recovery system are analyzed and studied in detail. It provides a theoretical basis for the optimization and determination of the final hydraulic component parameters.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH137.51

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