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1、翻译文献：INVESTIGATION ON DYNAMIC PERFORMANCE OF SLIDE UNIT IN MODULAR MACHINE TOOL （对组合机床滑台动态性能的调查报告）文献作者：Peter Dransfield,出处： Peter Dransfield, Hydraulic Control System-Design and Analysis of TheirDynamics, Springer-Verlag, 1981翻译页数：p139144l 英文译文： 对组合机床滑台动态性能的调查报告【摘要】这一张纸处理调查利用有束缚力的曲线图和状态空间分析法对组合机床滑台的
2、滑动影响和运动平稳性问题进行分析与研究，从而建立了滑台的液压驱动系统一自调背压调速系统的动态数学模型。通过计算机数字仿真系统，分析了滑台产生滑动影响和运动不平稳的原因及主要影响因素。从那些中可以得出那样的结论，如果能合理地设计液压缸和自调背压调压阀的结构尺寸.本文中所使用的符号如下： s1-流源，即调速阀出口流量； Sel滑台滑动摩擦力 R一滑台等效粘性摩擦系数： I1滑台与油缸的质量 12自调背压阀阀心质量 C1、c2油缸无杆腔及有杆腔的液容； C2自调背压阀弹簧柔度； R1, R2自调背压阀阻尼孔液阻， R9自调背压阀阀口液阻 Se2自调背压阀弹簧的初始预紧力； I4, I5管路的等效液感
3、 C5、C6管路的等效液容： R5, R7-管路的等效液阻； V3, V4油缸无杆腔及有杆腔内容积； P3, P4油缸无杆腔及有杆腔的压力 F滑台承受负载， V滑台运动速度。本文采用功率键合图和状态空间分折法建立系统的运动数学模型，滑台的动态特性可以能得到显著改善。一、引言 在组合机床正常工作中，滑台运动速度的大小和它的方向以及所承受负载的变化都将以程度不同地影响其工作性能。特别是在工进过程中。滑台上负载的突然消失引起的前进以及负载的周期性变化而引起的运动不平稳性，都将影响被加工件的表面质量，在严重的情况下会使刀具折断掉。根据大连机床厂要求，作者采用有束缚力的曲线图和状态空间分析法建立组合机床
4、滑台的新型液压驱动系统一自调背压调速系统的动态数学模型。为了改善滑台的动态特性，有必要去分析找出滑台产生前冲和运动不平稳的原因以及主要的影响因素，但那必须通过计算机数字仿真和研究得出最后的结果。二、动态数学模型 组合机床滑台的液压驱动系统一自调背压调速系统的工作原理图如图I所示。这个系统是用来完成工进一停止一快退”的工作循环。当滑台在工进时，三位四通换向阀处于图示右位，油泵的供油压力在滥流阀的有效作用下近似地几乎保持恒定，该油液流经过换向阀和调速阀后进入油缸的无杆腔，以推动滑台向前移动；与此同时，从油缸有杆腔排出的压力油经自调背压阀和换向阀流回油箱了。在这个过程中，两个单向阀和溢流阀的工作状态
5、始终都没有任何变化。对与象组合机床滑台的液压驱动系统一自调背压调速系统这样的复杂非线性的系统，为了便于研究它的动态特性，建立一个仅着重考虑主要影响因素的合理简单的动态数学模型是尤其重要的12。从理论分析和试验研究的列举中可以得知：该系统的过程时间是远大于调速阀的过程时间的，当油缸无杆腔有效承压面积很大时，调速阀出口流量的瞬时的超调反映为滑台运动速度的变化是很小的2。为了更加拓宽和深入研究系统的动态特性，使研究工作能在微型计算机上有效地进行，本文章对原模型2做进一步简化处理，假定调速阀在系统的整个通过过程中输出时候恒定的流量，这被看作其为流源。这样，系统的动态模型的结构简图如图2所示，它是由油缸
6、、滑台，自凋背压阀和联接管路等组成。 功率键合图是一功效流图，它是按着系统的能量传递方式，以实际结构为基础，用集中参数把子系统之间的作用关系抽象地表示为阻性元R、容性元C和感性元I的三种作用元。采用这种方法建模物理概念清晰，结合状态空间分析法可以较准确地描述和分析线性系统，该方法在时域中研究复杂非线性系统动态特性的一种有效的方法。 根据自调背压调速系统各元件的主要特性和建模规则1，得出了图3所示的系统的功率键合图。图中每根键上的半箭头表示功率流向，构成功率的两个变量是力变量（油压P或作用力F）和流变量（流量q或速度v）。O结点表示在系统中属于并联连接，各键上的力变量相等而流变量之和为零；1结点
7、表示在系统中属于串联连接，各键上流变量相等而力变量之和为零。TF表示不同能量形式间的变换器，TF下标注的字母表示力变量或流变量的转换比值。键上的短横杠表示该键上两变量间的因果关系。全箭头表示控制关系。在三种作用元中容性元和感性元的力变量与流变量之间具有积分或微分关系，因此，根据图3可推导出具有九个状态变量的复杂非线性状态方程。本文对滑台动态特性的研究是从滑台的前冲和运动平稳性两方面入手，用四阶定步长Runge-Kutta法在IBM-PC微型计算机上进行数字仿真,仿真结果分别如图4和图5所示。三、滑台前冲 滑台前冲现象是作用在滑台上的负载突然消失（如钻削工作的情况)引起的。在此过程中，滑台的负载
8、F、运动速度V、油缸两腔压力P3和P4的变化可从图4仿真结果看出。当滑台在负载的作用下匀速运动时，油缸无杆腔油液压力较高油液中聚集了大量的能量。当负载突然消失时，该腔油压随之迅速降低，油液从高压态转入低压态的过程中向系统释放很多能量，致使滑台高速向前冲击。然而，滑台的前冲使油缸有杆腔油液受压引起背压升高，从而消耗掉系统中的一部分能量，对滑台的前冲起到一定的抑制作用。应当看到，在所研究的系统中，自调背压阀的入口压力要受到油缸两腔油压的综合性作用。在负载消失的瞬间，自调背压阀的压力将会迅速地上升，并稳定地处在高于初始背压的数值以上。从图中可见，自调背压调速系统在负载消失瞬间油缸背压力升高的幅度大于
9、传统的调速系统，所以，其油缸有杆腔中油液吸收的能量就多；结果，滑台的前冲量比传统调速系统要小大约20%。可见采用自调背庄调速系统作为驱动系统的滑台在抑制前冲方面具有良好的特性，其中自调背压阀起了很大作用。四、滑台的运动平稳性 当作用于滑台上的负载作周期变化时（比如说铣削加工的情况），滑台的运动速度将要产生一定的波动。为于保证加工质量的要求，必须尽可能地减小其速度波动的范围。而从讨论问题的方便性出发来说，假设负载按正弦波的规律变化，从而得到的数字仿真结果如图5所示。由此可见这个系统与传统的调速系统有着相同的变化规律以及非常接近的数值数字。其中的原因是负载的变化幅度不大，油缸两腔的压力也就没有较大
10、变化，从而最终导致自调背压阀的作用不够明显显示。五、改善措施 通过研究的结果表明，以自调背压调速系统作为驱动系统的滑台，其动态特性要比传统的调速系统好的。要减少滑台的前冲量，就必需在负载消失的瞬间时候迅速提高油缸有杆腔的背压力；要提高滑台的运动平稳性就需增加系统的刚性，主要措施在于减小油液的体积。从系统的结构得知，油缸有杆腔与排油管之间有一很大的容积，如图6a所示。它的存在方面延迟和衰减了自调背压阀的作用，另一方面也降低了系统的刚性，它会限制了前冲特性和运动平稳性的进一步改善。因此，改善滑台动态特性可从两个方法进行处理：即改变油缸容积和改变自调背压阀结构尺寸。通过一系统结构性参数的仿真计算以及
11、结果的比较可以得出这样的结果：当把油缸有杆腔与排油管间容积V4同无杆腔与进油管间容积V3之比由原来的5.5改为1时，如图6b所示，同时，把自调背压阀阀芯底端直径由原来的10mm增加为13mm,阻尼三角槽边长从原来的lmm减小到0.7mm时，可使滑台的前冲量减小30%,过渡过程时间明显缩短了，滑台的运动平稳性也将会得到很大的改善。六、结论 通过理论上的分析和计算机仿真研究实验,很明显的是自调背压调速系统作为组合机床滑台的驱动系统是很有推广使用价值的。影响滑台动态特性的主要因素是油缸内部结构性和自调节背压阀的尺寸。假如能对其进行合理设计，可使滑台的动态特性得到显著地改善。同时，也说明了采用有束缚力
12、的曲线图和状态空间分析法研究复杂非线性液压系统的动态特性是既方便又有效的方法。【附】英文原文翻译文献：INVESTIGATION ON DYNAMIC PERFORMANCE OF SLIDE UNIT IN MODULAR MACHINE TOOL （对组合机床滑台动态性能的调查报告）文献作者：Peter Dransfield,出处： Peter Dransfield, Hydraulic Control System-Design and Analysis of TheirDynamics, Springer-Verlag, 1981翻译页数：p139144INVESTIGATION ON
13、 DYNAMIC PERFORMANCE OF SLIDE UNIT IN MODULAR MACHINE TOOLPeter DransfieldThis paper deals with the investigation for slide units impact and motion stability in modular machine tool fay means of the method of power bond graph and state space analysis. The dynamic mathematical model of self-adjusting
14、 back pressure speed control system used to drive slide unit is established. Main reasons and affecting factors for slide unit impact and motion unstability are analysed through computer digital simulation, It is concluded from those that, if the structural dimensions of hydraulic cylinder and back
15、pressure valve are designed rationally, the slide units dynamics will markedly be improved.NOMENCLATURESfflow sourceSeisliding friction force in slide unitRequivalent viscous friction coefficient in slide unitIimass of slide unit and cylinderhmass of SABP valve spoolCi,C2hydraulic capacitances of ro
16、d chamber and non-rod chamber in cylinder re-spec-tivelyC3spring compliance of SABP valveRrR2hydraulic resistances of damping holesR9hydraulic resistance of orifice of SABP valveSe2presetting force of spring in SABP valveI4J5equivalent liquid inertia in pipe linesCCgequivalent hydraulic capacitances
17、 in pipe lines equivalent hydraulic resistances in pipe linesV-j Voil-containing volumes in non-rod chamber and rod chamber respectivelyP,r:, P-ioil pressures in non-rod chamber and rod chamber respectivelyFload acted on slide unitVslide unit velocity* Department of Mechanical Engineering, Dalian Ur
18、.iversity of Technology, Dalian. China.INTRODUCTIONDuring operation of modular machine tool, the changes of slid units speed and load acted on it in both magnitude and direction will affect working performar.ee to a different extent Particularly the impact caused by sudden vanishing of load and the
19、motion unstability due to periodical change of load in operation will affect the surface quality of the workpiece machined, and the tool would be broken off under serious conditions, By using the method of power bond graph and state space analysis, the dynamic mathematical model of the system used t
20、o drive slide unit is established, that is called as self-adjusting back pressure speed control system and abbreviated to SABP system. In order to improve slide units dynamics, it is necessary to find out the main reasons and affecting factors, that must be based on computer digital simulation and s
21、tudy on the results.DYNAMIC MATHEMATICAL MODELThe schematic diagram of SABP system is shown in Fig.l, the system is used to perform the cycle of feeding, stopping and returning. Four way control valve works in the right position during slide units feeding. The supply pressure of the pump is approxim
22、ately constant under the action of pressure relief valve, the oil through the control valve and pressure compensated flow control valve enters the non-rod chamber to put slide unit forward. At the same time, the oil from the rod chamber is discharged through SABP valve and directional control valve
23、to tank. In this process, the state of two check valves and pressure relief valve is not changed, To establish the mathematical model as reasonably and simply as possible, consideration must be focused on main affecting factors for a complex non-linear system such as the SABP system. It is illustrat
24、ed by theoretical analysis and test result , that the transient time of the system is much longer than that of the flow control valve, and the flowrate overshoot of the valve in transients affects very small to slide unit speed because of the ;large effective sectional area of non-rod chamber in cyl
25、inder. For investigating the systems dynamics widely and deeply, the initial modeltn is further simplified in this paper, and so the study can be efficiently made with microcomputer. It is assumed that the flowrate through the flow control valve isconstant in the whole transient process, and is deno
26、ted to a flow source.Fig.2 shows the structure diagram of the dynamic model of the system, it is composed of cylinder, slide unit, SABP valve and pipe line; etc.By using the method of power bond graph and state space analysis in this paper, the dynamic mathematical model of the system is to be estab
27、lished- The power bond graph is a power flow diagram, which expresses abstractly the actions among sub-systems as three effects, i.e. resistance effect, capacitive effect and inertia effect, according to the way of energy transform, on the basis of practical structure and by means of method of lumpe
28、d parameters. The model is characterized by a clear conception in physics, and non-linear system can be accurately analysed in combination with method of state space analysis, thus it is a effective method used in the dynamic investigation of complex non-linear system in thetimedomain.From main perf
29、ormances of components in SAEP system, the power bond graph of the system has been formed by means of the rule of model establishing and is shown in Fig.3. Half arrow in each bond indicates a direction of power How, two variahles of power are effort variable and flow variable. O-junction illustrates
30、 algebraic summation of flow variables at common effort, i.e. parallel connection, 1-junction does algebraic summation of effort variables at common flow, i.e. series connection. The symbol TF represents power transformer between two types of energy, and transforming modulus between efforts or flows
31、 is noted below the symbol TF. Short transverse bar across one end of each bond shows causality between two variables. A full arrow expresses a control action. Among three actions, there is an integration or differential form in capacitive effect and inertia effect between two variables. So state eq
32、uation may be derived from Fig.3, there are nine state variables in this complex nonlinear equation. Studying on the slide units dynamics is started with impact and motion stability. The equation is simulated by using the method of 4th order Runge-Kutta integration procedure on IBM-PC computer. Fig.
33、4 and Fig.5 illustrate the results respectively.SLIDE UNIT IMPACTSlide units impact phenominon results from loads vanishing in the transients, for example, the situation of drilling through workpiece, Fig.4 expounds the variations of the load and speed of slide unit, the pressures of chambers in cyl
34、inder. When slide unit motions evenly under the action of load, the oil pressure in non-rod chamber is very high, and there is a lot of hydraulic energy accumulated in side. The pressure decreases at once with loads discharging rapidly. During the process of oil pressure converting from high to low,
35、 the system absorbs some of the energy, so slide unit impacts forward with high speed. And then the oil in rod chamber is141compressed to increase back pressure, some of the energy is consumed, which plays a part of restraining the impact of the slide unit. It must be noted that inlet pressure of SA
36、BP valve telys on the interaction of pressures of two chambers, and increases rapidly at the instant of loads vanishing, and then stabilizes at some value greater than initial one. This pressure is also greater than one of traditional speed control system, therefore the energy can be absorbed much m
37、ore in the rod chamber. In result, the impact of slide unit in SABP system is 20% lawer than in traditionals. It is thus clear that slide unit with SABP system for driving has a good performance in restraining the impact and SABP valve plays an important part in that,MOTION STABILITYWhen load acting
38、 on slide unit varies periodically, such as the situation of milling, slide units speed will bring about some pulse. In order to meet the requirements of manufacturing quality, the magnitude of the speed pulse must be reduced as small as possible. The variation of the load is assumed to be of sine w
39、ave, in order to simplify discussion of the problem, The result of digital simulation is shown in Fig.5 It can be seen that, the response of the system is the sameas traditionls and the differences between them are very small. The reason for this is that the variation of the load is not targe, there
40、 the pressures in chambers vary very little that is, the effect of the SABP valve is not obvious.IMPROVEMENTIt is shown by studying, that dynamics of slide unit which used SABP speed control system as driving system is better than that of traditional system. To reduce the slide units impact, the bac
41、k pressure of rod chamber has to be increased rapidly in the transients of loads vanishing; on the other hand, to enhance the slide units motion stability, it is necessary to raise the system rigidity. However, main recommendation lies in decreasing the volume of oil. It is known from system structu
42、re that, there is a lot of oil-containing volume between the rod chamber and drain pipe as shown in Fig.6a. Because the volume exists, not only the effect of SABP valve is delayed and reduced, hut also the rigidity of the system is decreased. Therefore, it is hindered to further improve the impact a
43、nd motion stability. To make the slide unit dynamics better, the structural dimensions of cylinders chamber and the SABP valve must be designed suitably. Based on simulations under the various structural dimensions and comparison among the results, the following two measures can be taken for improve
44、ments:the ratio between volumeV4 and V3 is changed from 5.5 to 1 approximately, as shown in Fig,6b;142the bottom diameter of spool of the SABP valve is increased from 10 mm to 13 mm and.the length of side of triangular damping slot is decreased from 1 mm to 0.7mm the slide unites impact quantity can
45、 be reduced by 30%, and the time of dynamic response is shortened. In addition, slide units motion stability may be improved obviously. It is thus evident that improvements are very effective.CONCLUSIONSBy the way of theoretical analysis and computer simulating investigation, it is obvious that the
46、SABP speed control system used as slide units driving system in modular machine tool is valuable for popularization and utilization, Main factors affecting the slide unit dynamics are the structural dimensions of the cylinder and the SABP valve. In the case of rationally designing, the slide unit dy
47、namics may be obviously improved. Meanwhile, it is shown that the method of power bond graph and state space analysis is a very convenient and effective method in studying dynamics of complex non-linear hydraulic system.REFERENCES1 Peter dransfield Hydraulic Control System-Design and Analysis of Their Dynamics Springer-Verlag, 19812 Dong Bengang, Zhang Zhixiang, Investigation on impact property of selfadjusting back pressure speed control system. Machine tool & Hydraulics No.2, 1987 GuangZhou, China, (in Chinese).
