新型磁流变阻尼式静压导轨及其高效精密控制策略研究

In order to solve the critical issues on positioning accuracy and operating efficiency of precision machine tools affected by the system vibration due to low camping coefficient of the hydrostatic guideway-slide system along the feeding direction, the target of this project is to investigate the motion accuracy control method of hydrostatic guideway-slide system with magnetorheological damping compensation thoroughly and deeply. Initializing with simple Dahl model and extending to generalized friction-slip Maxwell model the nonlinear varying behaviors of systematic friction disturbance for hydrostatic slide during startup and shutdown or instantaneously speeding up or slowing down processes are explicated. The dynamic model of hydrostatic guideway-slide system including driving force, structural parameters, variable damping compensation and frictional characteristics of oil film is established, by which the interacting relationship between positioning accuracy of hydrostatic guideway feeding system and such factors as mechanical properties, size parameters and damping coefficient, etc. is determined. A novel variable damping configuration with adjustable magnetic field strength achieved by magnetorheological fluid is developed to probe into the mathematical description between damping compensation value and control current and then discover the influence rule of exciting current, driving force and hydro force on positioning accuracy and operating efficiency. By using controllability of the external auxiliary variable damping compensation the optimized control strategy of the hydrostatic guideway system with the novel variable damping compensation through modal filtering technology and optimal control methods is explored to implement the optimized control of the positioning accuracy of hydrostatic guideway feeding system affected by external disturbances during instantaneously changing process of speed, which could provide an effective method to ensure the machined accuracy of large type machine tools.

针对液体静压导轨系统在进给方向阻尼低导致振动而影响机床定位精度与效率的关键问题，开展磁流变阻尼补偿的液体静压导轨运动精度调控方法研究。基于Dahl模型及广义Maxwell摩擦滑移模型，研究静压滑台在高速启停或瞬时加减速过程中系统摩擦力扰动的非线性变化特征；建立包含有驱动力、结构参数、变阻尼补偿及静压油膜摩擦特性的静压导轨系统动力学模型，探明进给系统的定位精度与其机械力学特性、尺寸、阻尼等参数之间的作用关系。研制一种采用磁流变液的新型磁场强度可调的变阻尼辅助补偿构型，探究阻尼补偿值与控制电流之间的数学描述，揭示其与励磁电流、驱动力及液力载荷对定位精度与效率的影响规律；利用外辅助阻尼补偿的可控性，利用模态滤波技术和最优控制方法，探求新型可变阻尼补偿静压进给系统的优化控制策略，实现进给系统瞬时速度突变过程中及在外界扰动下对定位精度的最佳调控和效率的提升，为保证大型机床的加工精度提供一种有效方法。

本项目针对数控机床进给系统动态性能的国内外研究前沿，结合企业新产品开发和新技术发展需要，在数控机床静压导轨进给系统运动精度调控方面作了大量的理论和试验研究，基本完成了预期的研究计划，研究成果具有重要的理论和实际应用价值。本项目的研究内容如下：.通过摩擦试验得到滑动结合面间在不同热处理方式、表面粗糙度和织构化表面、速度、加速度以及润滑条件下的摩擦静、动态特性曲线，研究了滑台在高速启停或瞬时加减速过程中系统摩擦力扰动的非线性变化特征，发现非线性摩擦特性中的负梯度效应过大是引起摩擦振动现象的关键因素。采用Lugre摩擦模型描述滑动结合面间的摩擦力，研究表明在外部激励作用下结合面鬃毛变形以及摩擦力会产生振荡现象同时在一定程度上影响滑台的切向振动。.研究了液体静压导轨的非线性时滞动态响应，讨论了阻尼和外力对振动系统控制的影响。建立了包含有驱动力、结构参数、变阻尼补偿及静压油膜摩擦特性的静压导轨系统动力学模型，推导了考虑非线性因素的切向振动方程。采用数值方法求解了静液压滑块的振动方程，探明了进给系统的定位精度与其机械力学特性、尺寸、阻尼等参数之间的作用关系。.建立了磁流变液阻尼器的力学模型，分析了阻尼力滞回效应，通过加载试验研究了阻尼器的力学特性，明晰了电流-速度-阻尼力之间的关系。基于遗传算法对系统参数进行了辨识及拟合。设计了新型的磁流变阻尼器及减振控制系统，仿真分析了阻尼器磁场、流场及工况对滑台进给方向振动的影响。采用模糊控方法根据反馈的振动信号来调节阻尼器输入电流改变阻尼力，达到了实时抑振的目的。搭建了进给系统试验台，测试了工作台进给方向和法向在安装阻尼器和未加阻尼器、以及阻尼器在不同电流下的减振性能。结果表明其振幅均有明显降低。因此本项目提出的新型可变阻尼补偿流体静压进给系统的优化控制策略，能够实现进给系统瞬时速度突变过程中及在外界扰动下对定位精度的最佳调控和效率的提升，为保证大型机床的加工精度提供一种有效方法。