【作者】 周勇；

【导师】 陈吉红； 彭芳瑜；

【作者基本信息】 华中科技大学 ， 机械制造及其自动化， 2008， 博士

【摘要】 高速加工技术要求数控机床的进给驱动系统具有高速度和高加速度,在高速度和高加速度运行工况下,进给驱动机构的动态特性将对机床的加工质量和效率产生显著影响,对现有的控制理论和方法提出了极大的挑战。在此情况下,必须深入研究进给驱动机构的动力学行为特性,并且这种动力学特性也必须在伺服控制和数控运动指令中加以考虑。本文以一种新型的进给驱动方式-重心驱动为对象,对高速进给驱动系统的动力学行为特性及其高精度运动控制策略进行了深入研究,主要包括以下几方面内容:建立了重心驱动机构的动力学模型,从理论上证明了理想的重心驱动方式能够抑制各轴运动时产生的回转振动和弯曲,从而实现稳定驱动。通过对重心驱动机构的参数化建模,分析了不同设计参数变化对重心驱动机构动力学性能的影响,研究结果为重心驱动机构的设计提供了原则。基于UG和ADAMS建立了高速进给驱动机构的整体动力学仿真平台,利用实验模态分析验证了仿真模型的有效性。通过对重心驱动方式与传统驱动方式的运动仿真对比表明,重心驱动方式在高加速度情况下优势突出,有效地抑制了振动,尤其是在轮廓拐角处,获得了比传统驱动方式高得多的运动精度,并进行了实验验证。建立了一种基于有限元方法的时变的进给驱动机构转子-丝杠系统扭转动力学模型,通过考虑移动部件位置和工件质量变化对系统扭转振动特性的影响规律进行了定量仿真研究。研究结果表明移动部件位置的变化对其扭转振动固有频率有显著影响,而工件质量变化虽然对其也有影响,但没有前者显著。考虑转子-丝杠系统的扭转动力学建立了其伺服驱动系统的数学模型,并设计了IIR陷波滤波器对其前两阶扭转振动模态进行了补偿,分析了扭转模态变化对陷波滤波控制的影响。为了使陷波滤波器能适应扭转模态的变化,提出了基于增益调度和基于神经网络的自适应陷波滤波控制方法,实例分析证明了这两种方法的有效性。基于数控机床进给驱动机构的动力学特性,分析了其物理约束条件,并针对NURBS曲线插补和小线段插补的几何与运动学约束,建立了运动指令的混合约束条件。基于混合约束条件,实现了插补过程的前瞻控制与自律规划。在华中世纪星HNC-22MF型数控系统上对所提出的插补算法进行了实验验证,证明了所提出方法的有效性。以重心驱动平台为例建立了数控进给驱动系统的机电联合仿真模型,改进了一种进给驱动系统动态性能的评价方法,在此基础上提出了一种两阶段的伺服参数调整方法。实例研究表明,利用该方法可有效地减少在实验平台上的调整过程。对传统驱动方式与重心驱动方式的动态性能进行了仿真对比研究,结果表明,采用重心驱动方式能够实现更高的位置环和速度环增益,即能实现更高的伺服控制带宽。更多还原

【Abstract】 The high speed machining (HSM) requires that the feed drives of CNC machine tools have high speed and high acceleration. In such operation condition, the dynamic characteristic of the drive framework will have an important influence on machining quality and efficiency and challenge current control methods in machine tool. Therefore, the dynamic behavior of the drive framework should be researched deeply and considered in the servo control and the CNC motion command. A new feed drive, Drive at Center of Gravity (DCG), is researched as an object, including its dynamic behavior and high precision motion control strategy. The main contributions of this dissertation are shown as follows:The perfect DCG could eliminate the turnover vibration and distortion to get a smooth movement, which is proved theoretically by building the dynamic model of DCG in this thesis. The effect of changeable design parameters on the dynamic performance of DCG is analyzed by building parameter model. The results provide important design principles for DCG. A whole dynamic simulation platform of high speed feed drive is built based on UG and ADAMS. The validity of simulation model is validated using experimental mode analysis. The motion simulation results comparing a DCG with a traditional feed drive indicate that DCG has an outstanding advantage to restrain the vibration in a high acceleration. Especially in the corner of the contour, the DCG acquires preponderant precision. The experiments in the DCG platform validate the characteristic.A numerical analysis to the torsion vibration of time-varying rotor-screw feed drive system on the basis of finite element method is presented to get an insight for the effect of in-time moving position of the table and changeable work-piece mass on the free vibration characteristic of the system. The results obtained demonstrate that the natural frequencies are notably changed with the position change of the table movement.Considering the torsion dynamic of rotor-screw system, the mathematic model of servo drive system that utilizes IIR notch filter to compensate the torsion vibration of first two orders is built. Moreover, the effects of changing torsion modes on notch filter are analyzed. In order to adapt the changing modes, adaptive notch filters that are based on gain scheduling and neural net respectively are presented. Example analysis validates the two adaptive notch filters. Combining the geometrical and kinematic constraint conditions of NURBS interpolation and little line interpolation with the physical constraint conditions that are based on the dynamic characteristic of machine tool feed drive, the mixed constraint conditions are built for the motion command. Look-ahead control and autonomic scheduling are realized according to the mixed constraint conditions during the interpolaton process. The presented interpolation algorithms that are applied in the HNC-22MF CNC system are validated experimentally. The results indicate that the algorithms are viable.A mechatronic integrated simulation model for a CNC feed drive that takes example by DCG platform is building. Based on an improved evaluation method of dynamic performance for feed drives proposaled by this thesis, a two-stage tuning method of servo parameter is presented. A case study shows that this method simplifies the test process effectively in the experimental platform. Moreover, the dynamic performances comparing a DCG with a traditional feed drive are simulated. The results indicate that DCG can realize higher position loop gain and higher velocity loop gain, namely has a higher servo control bandwidth.更多还原