Integration of a complex control system into a numerical process model for the simulation of ring rolling processes

在环件轧制过程的常规有限元模拟中，必须在模拟之前定义整个过程中所有刀具的运动。由于在实际过程中，所有的运动都是由复杂的闭环控制系统根据实际的过程变量和预先选择的控制策略进行自适应控制的，所以不可能预先规定所有的运动。因此，在研究的第一部分，将工业控制器的复杂控制算法集成到环件轧制的数值过程模型中。为此，环件轧制设备制造商提供的预编译版工业控制器已被耦合到环件轧制的有限元模拟中。在该模型中，刀具的所有平移和旋转速度都根据当前传感器的值(位置、力和力矩)调整为执行器，这些值是在有限元仿真中计算的。此外，该控制考虑了机器的力和扭矩限制，同时考虑了用户的初始要求(滚动策略、期望的环圈生长速度和几何形状)。这种新的方法首次能够模拟完整的环件轧制过程，具有真实的机器特定的运动历史，而不使用实验中的运动学变量。由于工业控制系统被设计为在机器的功率极限下执行该过程，因此力和力矩的正确估计在反馈控制仿真中是至关重要的。由于这些值并不总是被准确预测，建议的第二阶段的主要目标是研究和改进有限元模型中的力和力矩计算。一方面，这涉及到对热场计算的评估和必要时的改进。另一方面，必须评估在什么条件下，辊缝之间可能发生的静态软化机制对流动行为有显著影响。通过辊缝之间运行时间大小不同的实验，将分析两种软化行为截然不同的材料。利用这些实验的模拟，可以通过提取不同元素的局部热历史和力学历史来计算再结晶。由于在某些情况下，虽然力的计算是正确的，但模拟扭矩与实验结果不一致，因此需要验证轧制力矩测量的准确性。由于所提供的工业控制器只包含一个相关的工业滚动策略作为黑盒，因此并不总是能够确定仿真和实验之间存在微小差异的原因。此外，这种方法的另一个缺点是控制算法不能被增强和修改。因此，将实现一种具有类似于工业控制器的技术上合理的控制算法的模型。

In conventional Finite Element Simulation of the ring rolling process the motions of all tools have to be defined for the entire process prior to simulation. Since in the real process all motions are adaptively controlled by sophisticated closed-loop control systems according to actual process variables and preselected control strategies, it is not possible to prescribe all motions beforehand. Therefore, in the first part of the investigation the complex control algorithms of an industrial controller have been integrated into a numerical process model of ring rolling. For this purpose, a precompiled version of an industrial controller, which was provided by the manufacturer of ring rolling mills, has been coupled to the FE simulation of ring rolling. Within the model all translational and rotational velocities of the tools are adapted as actuators according to current sensor values (positions, forces and torques), which are calculated within the FE simulation. Furthermore, the control considers the force and torque restrictions of the machine while taking into account initial user requirements (rolling strategy, desired ring growth rate and geometry). The new approach enables for the first time the simulation of a complete ring rolling process with realistic machine specific kinematic history without using kinematic variables from the experiment. Since industrial control systems are designed to perform the process at the power limit of the machine, a correct estimation of forces and torques is of utmost importance in feedback controlled simulation. As these values were not always accurately predicted, the main goal of the second phase of the proposal is to investigate and improve the force and torque calculation in FE model. On the one hand this involves evaluation and if necessary improvement of the thermal field calculation. On the other hand it must be evaluated under which conditions static softening mechanisms, which might occur between the roll gaps, influence the flow behavior significantly. Two materials with highly different softening behaviors will be analyzed by experiments with large and small runtimes between the roll gaps. Using the simulations of these experiments the recrystallization can be calculated by extracting the local thermal and mechanical history of distinct elements. Since in some cases, the simulated torque differs from the experimental results though forces are computed correctly, the accuracy of the rolling torques measurement should be verified. As the provided industrial controller contains only one relevant industrial rolling strategy as a black-box, it is not always possible to identify the reasons for the minor differences between simulations and experiments. Furthermore, another drawback of this approach is that the control algorithms cannot be enhanced and modified. Therefore, a model with technologically reasonable control algorithms similar to the industrial controller will be implemented.