提高波纹管式制冷器稳定性的设计

针对波纹管式自调节流制冷器普遍存在稳定性差的问题,通过对此类制冷器最核心的部件——波纹管自调机构的受力分析,对制冷器的预留位移量这个核心参数进行优化设计,增强了制冷器的自调能力,从设计上避免制冷器不自调或流量变化现象的发生,改善了长期困扰自调式制冷器的间歇性喷液现象,提高了制冷器的稳定性,并通过实验得到了论证。     

焊线机超声波闭环控制

超声波是焊线机焊接过程中的重要参与元素,超声波控制效果决定着焊接的品质和速度。在分析超声换能器频率特性和电流响应的基础上,给出了频率自动跟踪和电流受控输出的闭环控制方案,提高了超声波效率,缩短了响应时间,增强了超声波输出的稳定性。实验结果表明,此方法实现了受控的上升时间和较小的超调     

Relay-based critical point estimation of a process with the PID controller in the loop

The proposed procedure is implemented without breaking the loop with the controller in operation, by activating a cascade of band-pass filters in series with a relay in the inner loop and a notch filter in the outer loop. A highly accurate estimate of the critical point of a process G_p(s) is obtained in the presence of measurement noise and load disturbance. The effectiveness of the proposed procedure is illustrated using a test batch consisting of stable, integrating and unstable processes, including dead-time.     

Persistent excitation condition within the dual control framework

Model Predictive Control framework is currently used in many different fields of expertise. The inherent part and very often also the main bottleneck is the model of a process used for the computation of predictions.Due to many reasons e.g. ageing, from time to time there exists a need to adjust/re-identify (if there was already some kind of a model-based controller) or to construct a brand new model (in other cases). Frequently, the process generating the data is under some kind of control, imposing thus problems when classical open loop identification methods are considered. The need for models identified from the data gathered in a closed-loop fashion and a request for possible re-identification of the model parameters lead to the emerge of dual control where the problems of control and system identification are addressed simultaneously.In this paper, we present a new algorithm based on the persistent excitation condition when the minimal eigenvalue of the information matrix is maximized in order to have sufficiently exciting optimal control signal satisfying the control requirements.     

GRAPHICAL TECHNIQUE FOR MODELING INTEGRATING (Non–SELF-REGULATING) PROCESSES WITHOUT STEADY-STATE PROCESS DATA

Model-fitting techniques for controller tuning that require the process to be initially at steady state cannot generally be used with integrating (non–self-regulating) processes. To address this issue, a graphical model-fitting technique is detailed and demonstrated for determination of first order plus dead time integrating model parameters from integrating process response plots. The resulting model parameters can be used directly in a range of tuning correlations designed specifically for integrating processes. The advantage of this technique is that it requires only two periods of constant manipulated and disturbance variables sustained just long enough for the process variable to respond and establish a clear slope. This is an important benefit because integrating processes generally cannot be maintained at an initial steady state as required when using techniques published for self-regulating processes. The result is an industry-friendly method. The method is demonstrated for level control in a pumped tank, a classical challenge in industrial practice. Both a simulation and a bench-scale experimental system are used in the demonstration studies.     

Simultaneous closed-loop tuning of cascade controllers based directly on set-point step-response data

This study presents a novel closed-loop tuning method for cascade control systems, in which both primary and secondary controllers are tuned simultaneously by directly using set-point step-response data without resorting to process models. The tuning method can be applied on-line to improve the performance of existing underperforming cascade controllers by retuning controller parameters, using routine operating data. The goal of the proposed design is to obtain the parameters of two proportional-integral-derivative (PID)-type controllers, so that the resulting inner and outer loops behave as similarly as possible to the appropriately specified reference models. The tuning rule and optimization problem related to the proposed design are derived. Based on the rationale behind cascade control, the secondary controller is designed based on disturbance rejection to quickly attenuate disturbances. The primary controller is designed to accurately account for the inner-loop dynamics, without requiring an additional test. In addition, robustness considerations are included in the proposed tuning method, which enable the designer to explicitly address the trade-off between performance and robustness for inner and outer loops independently. Simulation examples show that the proposed method exhibits superior control performance compared with the previous (model-based) tuning methods, confirming the effectiveness of this novel tuning method for cascade control systems.     

基于双闭环控制的供水系统

双闭环控制供水系统采用自整定模糊PID控制算法,以水泵电动机的转速和管网水压为设定参数,实现恒压供水。该系统实时控制性能良好,节能效果显著。     

Sequence-dependent batch chemical scheduling with earliness and tardiness penalties

Production volume in the specialized agricultural chemical industry is typically too small to justify the capital expenditure required for continuous processing. As such, there is a trend towards building chemical processing plants for this market segment that are batch plants. Scheduling of this type of chemical plant under just-in-time operations, where both earliness and lateness penalties are included, is critical to the efficient operation of these plants. In this paper, a heuristic scheduling procedure is developed for the problem of minimizing the total weighted earliness and tardiness costs as well as the total set-up cost for the single-stage batch chemical manufacturing environment.     

带钢冷轧闭环反馈控制最优化算法程序开发

基于多变量最优化控制的带钢闭环反馈控制模型能够充分利用弯辊和轧辊倾斜等平直度控制机构对板形偏差进行控制。闭环反馈控制的目的是使带钢实测板形与目标板形一致,闭环反馈最优化算法程序能充分利用输入信息,全面考虑多个执行机构对板形的作用,避免各控制之间的相互影响,它是该模型准确计算板形调节量的关键。为了实现自主建立带钢冷轧生产线,对某厂1 700 mm四机架四辊冷连轧机第四机架闭环反馈控制进行深入研究,根据对偶法采用C语言开发出基于多变量最优化闭环反馈计算程序并将其嵌入到可编程逻辑控制器(Programmable logic controller,PLC)中,开发出自主的基于多变量最优化闭环反馈控制模块。由该模块计算的闭环反馈平直度执行机构调节量与采用Matlab工具箱Quadprog函数计算结果一致,计算精度高。     

基于螺旋理论的Delta并联机器人自由度分析

螺旋理论以其几何概念清楚,物理意义明确,表达形式简单等优势,常被用于分析机构的自由度。按照传统的G-K(Grubler-Kutzbach)公式,能较容易地计算出串联机构的自由度,而对于一些特殊机构,尤其是含有闭环子链的复杂并联机构,往往无法便捷、正确地求解其自由度。为解决以上问题,以一种拓扑结构为[3-R(4S)1-RUPU]+R型的Delta并联机器人为研究对象,对其4S闭环子链进行了等效运动副螺旋系的求解,并判别了机构的局部自由度以及公共约束;利用修正的G-K公式,分别对原机构和等效后的机构进行了自由度的验证。结果表明:两种情形下的自由度数均为4,且自由度的性质为3平移1旋转,与实际设计相符。