【作者】 李毅波；

【导师】 黄明辉；

【作者基本信息】 中南大学 ， 机械工程， 2013， 博士

【摘要】 重型模锻装备是国家的战略基础制造装备,为国民经济各行业的高端装备提供大型主承载构件与锻件,在国家重大工程、国防建设中发挥着不可替代的作用。随着200～800MN重型模锻压机的先后建立,我国已经基本具备了生产大型整体锻件的条件,但由于系统集成层面上研究工作的薄弱或缺失,我国重型模锻装备的设计、制造和运行控制等方面缺乏系统科学的整体评判准则,无法进行整体功能与可靠度预测,致使我国重型模锻装备的性能提升与高效运行受到极大的局限与束缚,严重影响模锻件产品的品质；与此同时,锻件整体精密化的发展趋势要求采用新的成形工艺实现大型锻件的高性能制造。等温模锻由于可以显著降低材料的变形抗力、改善金属的流动状态和内部组织而成为锻件精密成形的关键技术。该工艺要求压力保持时间达500s以上,这意味着重型模锻压机需要在低速的情况下进行驱动和运行,而超大惯量系统在低速下运行时极易出现爬行或抖动,严重影响产品质量,迫切需要解决装备运行的确定性与高稳定性问题。基于此目的,本文以生产大型整体精密化锻件的等温模锻压机为研究对象,在建立重型模锻压机系统动力学、液压控制系统、材料成形过程模拟及解决模型间数据实时交互的基础上,形成重型模锻压机多学科集成仿真模型与装备整体性能的评估与预测方法,并从装备-工艺交互作用下的材料性能演变层面出发,实现对装备低速运行过程的主动优化控制,对提高重型模锻装备动态运行性能和锻件品质具有重要的理论意义和工程应用价值。论文的主要研究内容如下：1)重型模锻压机超静定冗余约束消减的系统动力学建模重型模锻压机超静定复合承载的结构形式给系统带来过多的冗余约束,针对不同超静定冗余结构特征,分别提出“以力代副、以简代副、以柔代刚”的建模方法,实现冗余约束的消减或消除；针对重型模锻压机组合预应力承载结构特点,提出一种简单的预载荷施加的方法,实现预应力构件的准确建模；在上述研究的基础上,形成重型模锻压机系统动力学建模的一般方法。基于系统动力学模型的动态性能仿真结果与实测结果对比验证了模型与方法的正确性。2)重型模锻压机低速液压控制系统的联合建模与参数优化针对等温模锻工艺所提出的装备低速稳定运行要求,提出以“电子泵驱动+伺服阀控+压力补偿+比例支撑平衡”为基本结构的伺服液压驱动方案,实现系统快速响应与低速小流量的补偿控制；PID或智能PID控制作为本方案的主要控制手段,其关键为控制器参数的优化,为此,本文提出采用遗传算法自动整定控制器参数的统一方法,仿真分析验证了其效果；在建立各子系统数学、物理模型的基础上,建立低速运行液压控制系统的联合仿真模型；最后通过实验验证模型的正确性和系统的可靠性。3)“装备运行-材料成形”过程交互及多学科集成建模与分析材料成形过程的复杂性及计算结果的离散性决定了成形载荷很难直接与成形装备联合仿真模型耦合。为实现装备运行与材料成形过程的实时交互,本文提出“主应力”法建立面向多学科集成的材料成形过程变形抗力模型并通过实验对模型进行优化；联合装备运行时的系统动力学和液压控制模型,建立基于锻造全过程的重型模锻压机多学科集成仿真模型；基于该模型,系统研究重型模锻压机低速运行时的动态特性,揭示各种参数对系统低速运行时的稳定性影响规律。研究表明：非线性摩擦是影响重型模锻压机低速稳定性的关键因素。4)基于摩擦反馈补偿的重型模锻压机低速运行稳定性控制为降低非线性摩擦对系统低速运行时的稳定性影响程度,论文首先建立重型模锻压机动态特性测试系统并进行摩擦力测试；基于摩擦力特征研究,提出一种修正的Lugre摩擦模型并采用最小二乘法、最小范数搜索法和遗传算法对摩擦力动、静态参数进行辨识；针对常规PID补偿控制无法同时满足扰动抑制和响应速度要求的问题,提出采用两自由度PID、模糊自适应PID及鲁棒自适应控制方法对系统摩擦力进行补偿控制。补偿控制效果的对比研究表明：模糊PID控制的补偿效果最优,压机最低稳定运行速度0.005mm/s,速度波动率<20%。更多还原

【Abstract】 Heavy forging press is the strategically foundational manufacturing equipment of our country; it provides the majority of the large load-bearing components and forgings for advanced equipments in all fields of the national economy and thus plays an irreplaceable role in major national projects and national defense construction. With the establishment of a series of huge forging presses of the forging force from200MN to800MN, we have already had the ability to produce large overall forgings. However, because of the weakness or lack of the research work at the level of system integrated, a systematic and scientific performance evaluation criterion for the design, manufacturing and running control of the heavy forging equipments is still unavailable. Due to the impossibility of overall functionality and reliability prediction for heavy presses, the improvement of running performance and operation efficiency have been largely limited and restricted and the quality of forgings have been greatly decreased. On the other hand, with the development of precise forgings, new forming method and process are required to complete the high performance manufacturing of large forgings. Because of the significant effects of reducing deformation resistance, isothermal forging technology has been the key to accurate forming of large components to improve metal flow state and internal organization performance of the materials. It is clear that the forging force must be maintained up to500seconds during the whole isothermal process, which means the heavy press must be running under extreme low speed for a long time. High inertia of the press will lead to working under unstable status, such as oscillating, crawling and jittering, thus greatly degrade the quality of the products. Therefore, it is urgent to improve the certainty and stability of the heavy press under low speed.For the above-mentioned purposes, taking isothermal forging press of large precision forgings as the object, based on model constructions of system dynamics, hydraulic control system, metal forging process and real-time data interactions among such models, a multidisciplinary integrated simulation model of the heavy forging press is established and thus a evaluation and prediction method for the overall performance of the heavy press is built up. Due to the equipment-forming interaction driven evolution research of the material properties, the model can achieve the purpose of active control of the equipment and thus is theoretically significant and valuable in engineering application for improving not only the dynamic performance of the press but also the quality of the forgings.Here are the main contents of this paper.1) Elimination of statically indeterminate redundant constraints and system dynamics modeling of the Heavy forging press.Statically indeterminate structures introduce too many redundant constraints to the system and make it too difficult to build a systematic dynamic model of the heavy press. Faced with different structures, methods of "rigid body flexible, force-generation kinematic pairs and constraints simplistic" are proposed to eliminate redundant constraints; for the pre-stressed structures, pre-load files of the levels are written and a simple method is proposed for the exact modeling of the forces. Based on such works, a general system dynamics modeling process is formed and typical models are built up to analyze the dynamic performance of the presses. Comparing the simulation results with the test ones, correctness of the modeling method and simulation models are validated in the end.2) Co-simulation and parameters optimization of the hydraulic control system of the low speed running heavy forging press.To satisfy the need of stable running under low speed, a new design of the low-speed hydraulic system with electrical variable displacement pump driving, high response servo valve controlling, hydraulic pressure compensation and magnetic proporgation support balancing system is proposed to achieve the purposes of rapid response and extreme small flow compensation control of the system. PID or novel PID controlling is the main strategy of this design, and parameters tuning and optimization of the controllers and extreme importment for improving the system’s response and control accuracy; to do so, a Genetic Algorithm is proposed and validated to automatically tuning the controllers in this paper; then, to complete the whole electro-hydraulic control system model, numeral and physical models of all the hydraulic components are built up and a full model is integrated; finally, the new design of the hydraulic system is applied to the heavy forging press and the accuracy and reliability of the system and numerical models are examined.3) Processes of equipment running and metal forging interaction based on multidisciplinary integrating modeling and stability study of the press.Complexity of mechanical characteristics and discrete of the simulation results during metal forging simulation made it too difficult to be coupled with multi-body dynamics model and hydraulic system directly. To overcome such a difficulty, a principal stress based and multidisciplinary integration oriented forging force analytically modeling method is proposed and optimized by the experiments results to establish the forging force in this paper. Joint the force with multi-body dynamic and hydraulic models, a full forging process base and equipment-forming interaction model of the low speed heavy forging press are established. Finally, dynamic properties of the press are studied systematically and nonlinear friction force is found to be the key factor that causes the system unstable.4) Stability control of the heavy forging press under extreme low speed based on the friction feedback and compensation.To reduce the influence of nonlinear friction to the stability of the press, a precision dynamic testing system is built up to obtain the friction force of the low speed running system; Based on the study of friction properties, a modified LuGre model is established, by using least squares method, minimum norm search method and genetic algorithm, parameters of the modified LuGre model are identified and validated through the experiments. In order to improve the stability of the system, normal PID, two-dof PID, fuzzy adaptive PID and robustic adaptive comprehensive control algorithm are used to establish different friction compensation methods. Comparing the control accuracy and velocity tracking errors with each other, a best compensation method is found and applied to the heavy press. Experiment results show that, the fuzzy adaptive PID control algorithm is the best one. By applying the fuzzy PID controller to the system, lowest speed of the press is about0.005mm/s and the speed fluctuation is less than20%.更多还原