切削振动时滞主动控制研究

发布时间：2019-03-28 19:33

【摘要】：切削作为一种主要的金属加工方式，广泛地存在现代制造业中。切削加工中的振动，尤其是颤振是制约其加工效率与精度的主要因素之一。为了提高加工质量与生产效率，有必要对切削振动实现有效地控制。本文将以车削和铣削过程为研究对象，建立一个具有时滞特性的系统加工动力学方程。由于切削动力学方程是具有时滞的微分方程，具有无穷多个特征根,全部求解其特征根具有非常大的难度。本文首先使用特征根方法讨论传统的单时滞反馈控在车削过程中的稳定域问题；在此基础上，对单时滞反馈控制进行了时域仿真，指出了其优点和不足。然后利用离散法，将车削动力学方程等效为一个标准的离散状态空间方程，基于线性二次型最优控制原理设计多时滞控制器，并对控制效果进行数值模拟验证。结果证明文中提出的时滞主动控制器能有效提高车削过程的稳定性，扩大稳定切削区域。同时讨论了控制时滞对控制效率及控制力的影响。相比于车削过程，铣削过程的复杂性不仅在于系统中时滞的存在，还在于由于铣削过程中刀齿旋转切削运动的周期性，这导致铣削动力学方程中的系数呈周期性变化。本文首先上使用半离散法讨论了状态时滞控制在铣削过程中的可行性；然后将铣削动力学方程的时变周期系数在一个周期内进行平均化处理，使之成为定常系数的时滞微分方程，基于此设计了双时滞主动控制器。随后讨论了双时滞在铣削振动控制中对控制效率的影响，并探讨了时滞不稳定区域与铣削系统分叉特性之间的联系。同时发现铣削系统在特定转速下发生倍周期分叉时，，时滞控制器将会失效。为了解决这一问题，文中将最低控制目标调整为定值，在一定程度上解决了时滞控制器失效的问题。
[Abstract]:As one of the main metal working methods, cutting is widely used in modern manufacturing industry. Vibration, especially flutter, is one of the main factors that restrict the machining efficiency and precision. In order to improve machining quality and production efficiency, it is necessary to control cutting vibration effectively. In this paper, taking turning and milling process as the research object, a system machining dynamics equation with time-delay characteristic is established. Since the cutting dynamics equation is a differential equation with time-delay and has infinitely many characteristic roots, it is very difficult to solve all the characteristic roots. In this paper, the characteristic root method is used to discuss the stability domain of the traditional feedback control with single time delay in turning process. Based on this, the time domain simulation of the feedback control with single time delay is carried out, and the advantages and disadvantages of the control are pointed out. Then using the discrete method, the turning dynamics equation is equivalent to a standard discrete state space equation. Based on the linear quadratic optimal control principle, a multi-time-delay controller is designed, and the control effect is verified by numerical simulation. The results show that the time-delay active controller proposed in this paper can effectively improve the stability of turning process and enlarge the stable cutting area. At the same time, the influence of control time delay on control efficiency and control force is discussed. Compared with the turning process, the complexity of the milling process lies not only in the existence of time delay in the system, but also in the periodicity of the rotary cutting motion of the cutter teeth in the milling process, which leads to the periodic variation of the coefficients in the dynamic equation of milling. In this paper, the feasibility of state delay control in milling process is discussed by using semi-discrete method. Then, the time-varying periodic coefficients of the milling dynamics equation are averaged in a period to make it a delay differential equation with constant coefficients. Based on this, an active controller with double delays is designed. Then, the influence of double time delay on control efficiency in milling vibration control is discussed, and the relationship between the unstable region of time delay and the bifurcation characteristics of milling system is discussed. At the same time, it is found that the time delay controller will fail when the period doubling bifurcation occurs in the milling system at a specific speed. In order to solve this problem, the minimum control objective is adjusted to a fixed value to solve the problem of time-delay controller failure to a certain extent.
【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TB535

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