【作者】 李松；

【导师】 宋锦春；

【作者基本信息】 东北大学 ， 机械电子工程， 2019， 博士

【摘要】 高精密数控车床和车削中心是高精度、高效率的自动化机床,在复杂零件的批量生产中发挥着重要作用。精密导轨系统可以实现精密进给,是高精密数控车削中心不可或缺的运动部件。其不仅要求有非常高的静态和运动直线度,而且要求有高刚度、高阻尼等的特性,在运动速度极低的情况下要求运动平稳、无爬行。因此,课题分析和综合了现有导轨系统的优缺点,采用闭式液体静压导轨作为课题机床X、Z两个进给轴的运动支承部件。同时选用树脂混凝土床身以达到良好的减振性能和热稳定性。为实现课题静压导轨系统的技术目标。从基本设计参数出发,以Z轴导轨系统结构为基础,优化了适用Z轴进给系统的双面薄膜反馈不等面积矩形油腔闭式静压导轨系统的各个结构参数。得到了导轨支承系统的静态刚度量值;推导了矩形油腔静压支承运动阻尼系数的计算公式,通过建立对置导轨的运动方程、双面薄膜的运动方程和闭式静压支承两个油路的流量方程,得到了闭式导轨系统的增量微分方程组,通过拉氏变换得到不等面积矩形油腔静压支承系统的传递函数。从而得到了负载大小和负载频率对闭式静压支承系统刚度和精度的影响规律。闭式静压导轨系统的精度不止要求支承油膜有较大的静刚度和动刚度,还需要机械结构拥有足够的刚度。利用ANSYS软件,建立了静压导轨系统导轨压板和底座的模型,分析了压板和底座的静态受力和变形情况,指出了部分设计的不足之处;同时,对压板和底座进行了模态分析,得到了压板和底座的前四阶振型和对应的频率,为避免机床加工时的共振提供依据。为了研究支承油腔的微观流动规律和各个机构因素的影响规律。建立了不同几何特征的矩形支承油腔的模型,通过设置不同的边界条件和系统参数,得到了油腔深度、四个过渡角圆角、支承表面速度等因素对导轨内静压压力分布、流场速度和方向以及温度分布的影响。从而得到了油腔深度,过渡区域的加工参数和轴进给最大速度的参考范围,同时为系统冷却的要求提供参考。双面薄膜反馈闭式静压支承理想状态下得到的计算静刚度和动刚度都很大,完全满足机床导轨的精度要求。而实际加工过程中,很难保证导轨间隙、薄膜厚度、薄膜节流间隙、油路压缩性等因素的影响,有可能会造成刚度偏低或是不稳定现象。为了实现导轨支承间隙的主动控制,课题设计了基于伺服位置控制的静压支承系统,得到了伺服阀控制的静压支承间隙系统的传递函数。为了使系统的响应能更准确更快,课题采用多方法讨论粒子群优化算法(MMAPSO)对系统传递函数的PID控制进行优化,课题选择了 PSO、LDIWPSO、CLPSO和MMAPSO四种算法进行对比。优化结果表明,经过MMAPSO算法优化后,PID的响应时间明显缩短,相比其他算法,MMAPSO具有最快的收敛速度和收敛精度,获得的PID综合效果最好。为验证基于伺服位置闭环控制的经验导轨系统的承载能力和刚度,仿照课题机床Z轴导轨静压腔的结构及参数,搭建了基于伺服位置闭环控制的静压导轨系统实验台。由于条件限制,仅对一侧油腔的导轨系统的位置进行控制,考虑到伺服阀和外界干扰因素的影响,伺服位置控制取得了较好的控制效果,实现了导轨系统极大的刚度需求,并且抗超载能力极强。更多还原

【Abstract】 High-precision digital controlled lathes or turning centers are referred as automatic lathes that have high precision and efficiency.They play a critical role in quantity production of complex parts.Guideway system,as an important part of these machines,must satisfy such requirements such as high static and kineticstraightness accuracy,strong stiffness,large damping,and steady motion(no creeping)in low velocity.Therefore,this research analyzes the guideway systems in literature and proposes a novel concept that employs closed hydrostatic guide way as supporting part of X and Z direction feed shaft.In addition,lathe beds are made of resin concrete in order to get good vibration damping performance and heat stability.In order to build the system,we design differential rectangle chamber with double thin-film feedback for Z shaft.We also calculate its static stiffness and kinetic damping of the hydrostatic supporting system.We obtain differential equations of the guideway system by establishing kinematic equations of the guideway and double thin film,and flow equations.Next,the system transfer function is obtained by performing Laplace transform.The effects of load size and frequency on the system precision are further investigated.The guideway system needs not only thin film to have high static and kinetic stiffness,but also mechanical structure does.This research establishes the models of clip and base and analyzes their static force and deformation by ANSYS.In addition,we also implement modal analysis and obtain their vibration mode of first four orders and corresponding frequencies in order to avoid resonance during production.In order to study the micro flow in chamber and the effects of each part,we establish the model of different rectangle chambers.The effects of chamber depth,four circular bead and supporting surface velocity on static pressure distribution,flow distribution and temperature distribution are investigated by defining different boundary conditions and system parameters.We obtain the range of these parameters which are used for designing cooling systems.The static and kinetic stiffness of hydrostatic supporting with double thin-film feedback is high in ideal conditions,which satisfies requirements of high-precision guideway system.However,in practice the stiffness may be low or even the system is not steady because of the effects of guide gap,film thickness and throttling gap,and oil compressibility.In order to control the gap of guideway,this research employs servo valve as control element and calculates the corresponding transfer function.In order to improve the performance,PSO,LDIWPSO,CLPSO and MMAPSO algorithms are used to optimize PID parameters.Results show that MMAPSO algorithm could reduce the settling time greatly and has fastest convergence rate and precision.To test the rigidity and bearing capacity of the guide way system adopted the servo position closed-loop control theory,which the test bench was modelled on the topic of Z axis machine tool guideway structure and parameters.Only the one side position was controlled by servo valve in the guideway system due to some constraints.Considering the servo valve and interference factors,a good control effect was achieved and the great stiffness requirement was satisfied.At the same time,the system has a strong ability to resist the overload.更多还原