Design and Analysis of a Closed-Loop Single-Workstation PPC System

Methods at control engineering can be integrated with methods of production engineering to improve robustness and performance of production systems, while making dynamic analysis tractable and improving understanding of complex behavior. In this paper a discrete, dynamic model of a single workstation is developed, including characteristic equations of transfer functions that are useful in choosing control parameter values according to desired dynamic performance and response. Nonlineartties such as dependence of capacity on WIP and delay in adjusting capacity due to work rules are modeled and incorporated into the dynamic analysis. Examples are presented of control parameter selection and resulting performance.     

Control-Theoretic Analysis of a Closed-Loop PPC System

An analysis of a production planning and control system with closed-loop control of backlog and work-in-progress is presented in this paper, illustrating integration of methods of control engineering with methods of production engineering. The architecture of the system is described and a control-theoretic dynamic model is developed that includes uncertainties in capacity and work input that result from equipment failures, rush orders, etc. Transfer function analysis is used to model dynamic relationships between system inputs and variables including backlog and work-in-progress. The results are used to select control laws for desired system performance and to calculate system response.     

基于模糊小脑模型神经网络的直线伺服跟踪控制研究

在高精度直线伺服跟踪控制系统中,为使输出响应快速地跟踪输入指令,需要克服系统滞后、未建模动态、不确定性以及负载变化的影响,文中提出了一种模糊小脑模型神经网络(FCMAC)直接逆控制的方案,可动态地克服这些影响.文中给出了较详细的原理分析及实现过程.仿真结果表明,该方法能够明显提高直线伺服系统的快速跟踪能力,并使系统具有较强的适应性和鲁棒性.     

三自由度并联机床动态有限元分析

对并联机床进行动态性能分析有着重要意义。应用工程分析软件,建立了一种三自由度并联机床整机的有限元模型,对整机进行了模态分析,提取了整机前十阶固有频率和振型。为了解各阶频率对机床动载荷的响应情况,在模态分析的基础上对整机进行了谐响应分析,得到了动平台、球铰、滑鞍等关键部位的频率位移响应曲线。分析结果表明,机床的第2阶和第4阶固有频率对机床动态性能影响最大。球铰结合部为机床结构中薄弱环节,由此提出了机床结构优化设计建议,将球形铰链更换为虎克铰链,从而提高了机床的动态性能。     

快速瞬态响应的弧焊逆变器研究

结合弧焊逆变器对控制方法和主电路控制建模要求的提高，指出了动特性改善和改进逆变器系统快速瞬态响应指标的一致性。列出了几种VRM研究中提高快速瞬态响应性能的方法，特别对V^2控制方法进行了详细分析。通过对脉冲MIG焊的具体分析，对BUCK变换器中的相关控制方法在弧焊逆变嚣中应用的可行性和存在的困难进行了讨论。     

Contact condition modelling for machining fixture setup processes

Manufacturing automation often requires high precision and highly accurate equipment to achieve satisfactory performance. In many cases, precision and accuracy depend highly on the surface contact conditions between machine components. Described in this paper is the modelling of the response frequency of a modular fixturing system with multiple components in contact, and it has demonstrated that it is possible to monitor the contact conditions based on a fixture system's dynamic response frequencies. The virtual spring element based on the Hertz theory is used to recapitulate the fixture contact conditions in the finite element modelling. Possible contributing factors to contact conditions, such as material properties, surface finish, hardness and the contact area between the workpiece and fixture device, are investigated in the estimation of the virtual spring constant. Experimental analysis is also conducted to verify the analytical model. The application of this model can be used for control, monitoring, and design of general clamping devices in many manufacturing processes.     

影响测微仪测头临界脱离频率因素的研究

为了改善电感测微仪测头的动态响应性能,找出测头的临界脱离频率,对影响测微仪测头临界脱离频率的因素进行了理论分析,并通过试验台对测头的刚度、质量及预压量等因素对其产生的影响进行了验证。试验结果表明：在对电感测微仪测头的设计中,合理增加刚度和预压量、减少活动部分的质量可以提高测头的动态响应性能。     

基于有限元的140 kN摩擦焊机主轴箱响应面优化分析

以140 kN连续驱动摩擦焊机主轴箱为研究对象,应用有限元分析软件对主轴箱进行了静、动态相关特性的分析。为提高主轴箱综合力学性能,并实现主轴箱箱体材料的合理利用,以箱体壁厚等7个结构参数为设计变量进行了中心复合实验设计。根据得到的数据结果,基于Kriging插值法建立了主轴箱的响应面模型,并对各设计变量进行了灵敏度分析。利用多目标遗传算法完成了主轴箱的优化设计,与原结构方案相比主轴箱箱体减重16.6%,实现了焊机轻量化设计。经过对主轴箱响应面模型拟合精度的校验,验证了CCD实验法与Kriging插值法相结合可高效精准地完成主轴箱响应面模型的建立。因此这一优化方法同样适用于其他类型的机床零部件的设计。     

Accuracy improvement of wire-EDM by real-time wire tension control

In this paper, a closed-loop wire tension control system for a wire-EDM machine is presented to improve the machining accuracy. Dynamic models of the wire feed control apparatus and wire tension control apparatus are derived to analyze and design the control system. PI controller and one-step-ahead adaptive controller are employed to investigate the dynamic performance of the closed-loop wire tension control system. In order to reduce the vibration of wire tension during wire feeding, dynamic absorbers are added to the idle rollers of wire transportation mechanism. Experimental results not only demonstrate that the developed control system with dynamic absorbers can obtain fast transient response and small steady-state error than an open-loop control system, they also indicate that the geometrical contour error of corner cutting is reduced with approximately 50% and the vertical straightness of a workpiece can be improved significantly.     

电机械执行器驱动压差可控型多路阀特性研究

现有负载敏感多路阀,由于压力补偿器受到液动力等因素的影响,存在流量控制精度低等问题。以阀后补偿多路阀为研究对象,应用补偿压差调控原理,设计由伺服电机与滚珠丝杠组成的电-机械压差控制单元,增设于压力补偿器之上,构建新型压差可控型多路阀。阐明新型压差可控型多路阀的工作原理,在SimulationX仿真平台上建立了多路阀联合仿真模型,进行仿真分析。结果表明:伺服电机采用转矩控制模式,控制电机输出转矩,对补偿器阀芯施加附加力,可以在0~3.5 MPa范围内对主阀节流口压差进行连续控制;而且可以对液动力进行估算与补偿,提高了流量的控制精度;此外,在电-机械压差控制单元非控制和控制两种状态下,伺服电机转动惯量越小,滚珠丝杠导程越大,对补偿器响应特性影响越小,压差控制动态响应越好。     

变量柱塞泵的键合图建模和动态仿真研究

本文分析总结了国内外以往各种有关变量柱塞泵的研究和存在的问题。在此基础上利用能以统一的功率流方式处理多能量域并存系统的键合图建模技术建立了一个简化的非线性变量柱塞泵动态数学模型。模型中的许多结构参数的处理取决于泵模型的选取。在本研究中,使用的是Parker公司的PVP76型恒压变量柱塞泵。针对其中一些影响较小的非线性项和因素进行了近似线性化处理和忽略。然后使用MATLAB／SIMULINK进行动态仿真,结果表明该泵的动态数学模型是令人满意的。最后通过变化一些重要的结构参数来分析其对系统动态响应的影响程度,为系统优化提供了理论依据。     

汽车主动悬架系统的有限频域输出反馈控制

为进一步提升汽车悬架系统动力学性能，提出一种基于启发式两步法的静态输出反馈控制方法。为了更好地研究悬架动力学行为，建立一种经典的1/4车主动悬架系统模型用于控制分析与设计。考虑到人体对4~8 Hz频内的垂直振动异常敏感，给出一种有限频域下的性能判据作为控制设计的指导。同时，在控制设计中考虑了悬架行程和轮胎动位移两种机械硬约束，以保证悬架系统的动力学稳定性。由于难以在线获取实际悬架系统中所有状态信息，提出一种新的基于启发式两步法的有限频域输出反馈控制方法。数值仿真及台架试验结果表明：与传统的全频域输出反馈方法相比，该方法具有更好的控制性能。     

Dynamics of ultra-high-speed (UHS) spindles used for micromachining

Micromachining dynamics commonly dictate the attainable accuracy and throughput that can be obtained from micromachining operations. The dynamic behavior of miniature ultra-high-speed (UHS) spindles used in micromachining critically affects micromachining dynamics. As such, there is a strong need for effective techniques to characterize the dynamic behavior of miniature UHS spindles. This paper presents a systematic experimental approach to obtain the speed-dependent two-dimensional dynamics of miniature UHS spindles through experimental modal analysis. A miniature cylindrical artifact with 5 mm overhang is attached to (and rotating with) the spindle to enable providing the dynamic excitations to and measuring the resulting motions of the spindle. A custom-made impact excitation system is used to reproducibly excite the spindle dynamics up to 20 kHz while controlling the impact force. The resulting radial motions of the spindle are measured in two mutually perpendicular directions using two independent fiber-optic laser Doppler vibrometers (LDVs). To ensure the mutual orthogonality of the measurements, the two lasers are aligned precisely using an optical procedure. A frequency-domain filtering approach is used to remove the unwanted spindle motion data from the measurements, thereby isolating the dynamic response. The spindle dynamics is then represented in the form of frequency response functions (FRFs). A global curve-fitting technique is applied to identify natural frequencies and damping ratios. The developed approach is demonstrated on a miniature UHS spindle with aerodynamic bearings, and dynamic characteristics are analyzed at different spindle speeds and collet pressures. The spindle speed is shown to have a significant effect on dynamic response, especially at higher spindle speeds, while the collet pressure is observed not to have any significant effect on the spindle dynamics. It is concluded that the presented approach can be used to characterize the dynamics of miniature UHS spindles effectively.     

Dynamic model of a centerless grinding machine based on an updated FE model

Centerless grinding operations present some characteristic features that make the process especially susceptible to regenerative chatter instabilities. Theoretical study of these vibrations present some difficulties due to the large amount of parameters involved in the process and, in addition, such a study requires a precise determination of dynamic properties of the particular machine under study. Taking into account the important role of the dynamic characteristics in the process, in this paper both analytic and experimental approaches are used with the aim of studying precisely the vibration modes participating in the response. Using as reference results obtained from an experimental modal analysis (EMA) performed in the machine, the finite element (FE) model was validated and improved using correlation and updating techniques. This updated model was used to obtain a state space reduced order model with which several simulations were carried out. The simulations were compared with results obtained in machining tests and it was demonstrated that the model predicts accurately the dynamic behavior of the centerless grinding machine, especially concerning on chatter.     

基于响应面法的长管道水下液压系统优化设计

针对海上钻井平台上带长管道的水下液压系统进行研究,建立该系统的简化数学模型,对系统的时域响应进行分析。应用AMESim仿真软件对该系统进行建模并分析其动态特性,得出不同管长、管径、油液黏度以及弹性模量条件下的系统响应曲线;分析蓄能器的位置对系统动态特性的影响。利用基于响应面法的Box-Behnken试验设计方法分析各因素对系统动态响应时间的影响程度,得出各因素与响应时间的数学模型。对系统进行参数优化设计,得到最佳的管长、管径、油液黏度、弹性模量及蓄能器位置的优化设计方案。优化结果与原设计对比后发现,优化设计的响应时间仅为原模型动态响应时间的34.9%,极大提高了系统的响应时间,为水下液压系统带长管道系统设计提供了参考。     

High temperature damping behavior of plasma sprayed NiCoCrAlY coatings

There is a trend to design the turbine coating and the substrate as in integral, layered, engineering assembly. Under the harsh environment of the turbine engine, a failure in one component can quickly lead to failure in other components. Materials that are used in structural applications are prone to mechanical vibration, which, when not attenuated, will lead to fatigue of components and shortening of life cycle. Therefore, it is necessary to examine the thermal stability and dynamic mechanical properties of coatings under dynamic conditions. In addition to these noise reduction and vibration amplitude control motivated objectives, however, mechanical energy dissipation processes also find intrinsic applications in cases for which a thorough understanding of the mechanisms responsible for the damping response of the material is required. This article describes the damping behavior and mechanisms that exist in plasma sprayed NiCoCrAlY coatings.     

基于参数优化的电液位置控制系统的最优控制

为提高电液位置控制系统的控制精度，改善系统的动态性能，建立了参数的最优控制指标，优化后得到最优参数，利用最优参数建立电液位置控制系统最优传递函数，对原系统进行优化，应用数值仿真方法，并对优化前后系统的动态性能进行了对比分析。仿真结果表明，优化后系统的超调量和响应时间大幅减小，系统的动态性能得到改善。     

Using material behavior models to develop process control strategies

Advances in material behavior modeling have enabled the explicit incorporation of material phenomena into process design and control methodologies. A new approach to material behavior modeling, in which stability analysis has been combined with the analysis of activation energy, can be used to identify processing regimes within which the material behavior is essentially deterministic and is amenable to process control. This articles illustrates the application of this dynamic material modeling approach through the example of deformation processing of a δ-TiAl alloy. Additionally, a new control-system design strategy explicitly based on the knowledge of the state of the material under hot-deformation conditions is explored.

     

电液伺服系统无模型轨迹跟踪控制算法的研究与实现

对于具有往复运动特征的电液伺服系统，由于存在很强的非线性，依靠模型分析，求解将是十分复杂的，本文提出了一种基于Fourier级数的无模型的电液伺服系统轨迹跟踪控制算法，该算法轨迹跟踪问题在Fourier空间转化为调节器问题，并给出了控制器的详细设计及系统的稳定性分析，最后给出控制器在注塑机上的实际应用，实验结果表明该方法对改善注塑机动模的运动特性有较好的效果。     

直驱式泵控电液伺服系统建模与动态特性分析

为研究直驱式泵控电液伺服系统的动态特性,分析了系统的工作原理,分别建立了泵控和阀控两种控制系统的数学模型并进行了动态响应的理论分析和比较研究.搭建了一个包含交流伺服电机—定量泵为动力源的伺服驱动系统实验台,可以进行两种控制系统的性能实验.对实验系统进行了动态响应的数字模拟和实验研究,结果表明,由于泵控系统液压固有频率较...