A novel cross directional register modeling and feedforward control in multi-layer roll-to-roll printing

For the adaption of roll-to-roll printing method to the printed electronics, it is mandatory to increase the resolution of register control. Therefore, it is desired to derive a mathematical model for register and to develop a controller to reduce the register error. The cross direction register error was derived considering both the lateral motion of a moving web and the transverse position of a printing roll. And a feedforward control method was proposed to cancel out the disturbance of CD register from upstream span. The proposed controller could be used to improve the performance of the CD register controller in a large area roll-to-roll printing machine. The mathematical modeling and proposed control method were validated by numerical simulations and experimental verifications in various operating conditions using a multi-layer direct gravure printing machine. These results show that the proposed feedforward control scheme greatly improves the control performance of register control in overcoming the upstream disturbances.     

A mathematical model to predict surface roughness and pattern thickness in roll-to-roll gravure printed electronics

The roll-to-roll printing processes have recently been applied for the manufacturing of printed electronics due to their advantages, such as their high-throughput capabilities and low associated costs. In a roll-to-roll printing machine, a web or substrate is moved from an unwinding roll to a winding roll. During printing, the operating tension is important for correct substrate handling to prevent substrate defects, such as wrinkles, scratches and breaks. Accordingly, the operating conditions of the moving web can affect the quality of the printed pattern. In this study, a mathematical model has been developed to predict the thickness and surface roughness of printed patterns. Because the dynamics of roll-to-roll printing systems are complicated and non-linear, a statistical model is preferred. A full factorial method has been used with four independent variables: operating tension, print speed, ink viscosity and theoretical transfer volume. This model accurately predicted the surface roughness and thickness of the printed pattern.     

A position measurement system for precision alignment of roll-to-roll printing and sensitivity analysis of thermal deformation

Roll-to-roll processing in the field of printed electronics is the process of creating electronic circuits or devices on a roll of flexible plastic or metal foil, and it can be used in the manufacture of many products, such as RFID tags, solar cells, and flexible display panels, at a much lower cost than that in the semiconductor lithography process. This process is also more efficient in producing electronic devices in a large volume than semiconductor lithography. As with lithography, roll-to-roll processing also needs to achieve accurate layer-to-layer alignment in fabricating multi-layered circuits or devices. This alignment precision, in fact, is a critical factor in determining the integration and performance of printed electronics. In other words, it is essential to achieve highly precise alignment in roll-to-roll printing for the full commercialization of printed electronics. To that end, this study proposes an alignment pattern that is directly printed on a web as a solution that can enhance the alignment precision in roll-to-roll printing. Based on this, the study also proposes a web position measurement system using optical measurement instruments and verifies its applicability and reliability. Considering the fact that tension on the web and heat generated in the process of curing may deform the web, we conducted experiments and simulations to analyze the measurement sensitivity when the web is actually deformed and we present the results of the study.     

Preview control of web position in roll-to-roll printing using alignment patterns

In printed electronics systems, the roll-to-roll process is a next-generation process technology that may be applied to the production of various electronic products such as flexible electronic devices, solar cells, and display panels. The process allows for production at low unit cost and high speed. As a factor for improving the print quality, there are ink viscosity, printing speed, printing pressure, and alignment precision. Among these factors, alignment precision, a critical factor in the performance of an electronic circuit, is the accurate alignment of layers in a multi-layered structure. In our previous study, we suggested a measurement method for improving the alignment precision by using an optical pre-measuring device and an alignment pattern that is printed by roll-to-roll printing process. In the measuring system, when a web is transported in the web feed direction, the optical pre-measuring device measures the quantity of light reflected by the alignment pattern. A lateral position can be aligned accurately based on the measured signal. However, because the position is measured in advance in the web feed direction, it is not applicable to a real-time printing system, and when the lateral position is measured using the optical pre-measuring device, a lateral position error, that is generated by disturbances induced by tension acting on the web and the vibration of the motor, can be estimated. A motor driven linear translation stage for lateral direction is used to minimize the lateral position errors in roll-to-roll systems. In this paper, we propose a preview control system to reflect the measured lateral position error to the printing result at the appropriate time for improving the alignment precision in roll-to-roll printing. As a control method, using roll-to-roll model, the system of disturbance, lateral angle and lateral position can be expressed as a state-space equation. Based on this equation, a preview controller to find the optimal value of state and control error is designed in a similar method to the conventional preview control method used for the active suspension system of a vehicle. Then, the alignment results are verified using another optical measuring device of a web transport system.

     

Analysis of dynamic thermal characteristic of register of roll-to-roll multi-layer printing systems

Register control is essential in the roll-to-roll printing of organic thin-film transistors. Specifically, microscale accuracy is required in the control of the overlay printing register. To achieve such precise control, the characteristics of the substrate under the operating conditions, such as the drying temperature and the tension applied to the substrate, should be considered. In this study, the variations of the elastic modulus and thermal deformation with the drying temperature were investigated, and the correlations among the change in the thermal characteristic of the substrate, the tension, and register error were also analyzed. The results of the analyses showed that the thermal deformation produced by the temperature change generated tension and register error, with the effect increasing with increasing drying temperature. System identification techniques were further used to develop a register model for estimating the register error due to thermal and elastic strains. The maximum estimation ability of 86.27% of the developed model is higher than that of a conventional register model.     

对象参考参数自适应时滞补偿器

基于模型参考自适应控制原理,提出对象参考参数自适应时滞补偿器,以线性大时滞不确定被控对象为参考模型综合出自适应律,使预估补偿器的参灵敏逐步逼近被控对象的参数直至相等,仿真研究表明,在参数不匹配和出现负荷扰动的情况下,参数自适应时滞补偿器均有良好的预估补偿能力。     

Robust Motion Control for Robotic Assembly Tasks using Variable Structure Control Scheme

The success of robot assembly tasks depends heavily on its ability to handle the interactions which take place between the parts being assembled. In this paper, a robust motion-control method is presented for robot manipulators performing assembly tasks in the presence of dynamic constraints from the environment. Using variable structure model reaching control concept, the control objectives is first formulated as a performance model in the task space. A dynamic compensator is then introduced to form the switching function such that the sliding-mode matches the desired model. A simple variable structure control law is suggested to force the system to reach and stay on the sliding mode so that the specified model is achieved.The proposed method is applied to control the prismatic joint of a selective compliance assembly robot-arm type robot for the insertion of printed circuit board into an edge connector socket. Various amounts of interaction forces are generated during the operation. Experimental and simulation results demonstrated the performance of the variable structure model reaching control approach. In comparison, it is shown that the popular position controllers such as proportional plus derivative control and proportional plus derivative with model-based feedforward control are not suitable for achieving good trajectory tracking accuracy in assembly tasks which experience potential interaction force.     

压力传感器动态误差修正方法的FPGA实现

为了实时修正由于压力传感器动态特性引起的动态误差,提出了一种基于IIR数字补偿滤波器的FPGA实现方案.该方案首先依据压力传感器动态标定时的输入和输出数据利用改进的最小二乘算法建立全面描述传感器系统的数学模型,继而运用零极点配置方法重新配置模型零极点得到最优IIR补偿器模型及参数,其次在保证补偿器性能无失真或失真很小的基础上使用MATLAB工具量化补偿器模型参数,最后在以FPGA为控制核心的数据采集及存储系统的基础上应用量化的IIR补偿器模型参数设计了IIR补偿器软核,从而实现传感器动态误差的实时修正.实验结果表明:该方案能够实时有效地修正传感器动态误差.     

一种可保证瞬态特性的改进的鲁棒模型参考自适应控制

针对典型的鲁棒模型参考自适应控制中瞬态性能无法得到保障的问题, 提出一种改进的鲁棒模型参考自适应控制器. 该控制器在标准的鲁棒自适应控制中加入??_∞ 补偿器, 以抑制闭环自适应系统中参数估计误差和不确定扰动对系统输出跟踪性能造成的不利影响. 理论分析和仿真验证表明, 所提出的控制器不但保留了典型鲁棒模型参考自适应控制的理想特性, 并且通过设计适当的??∞ 补偿器使得闭环系统的瞬态性得到了较大的改善, 其改善的程度依赖于??∞ 补偿器性能指标的大小.

     

A novel dead time compensator for stable processes with long dead times

This paper presents a new and simplified approach for the design of dead time compensators for processes with long dead times. The approach is based on a modified structure of the Smith predictor that allows the user to isolate the disturbance and set-point responses and thereby, provide a two-degrees-of-freedom control scheme. The proposed structure is easy to analyze and tune. Using an estimation of the dead time and process model of the plant, the proposed compensator is left with two tuning parameters that determine the closed-loop performance and robustness. The performance of the proposed compensator is compared with the most recent dead time compensator appeared in the literature. The method is evaluated on two simulated processes and a computer-interfaced pilot-scale two tank heating system to demonstrate the practicality and utility of the proposed scheme.     

凹印机多色套准系统自抗扰解耦控制

针对凹版印刷机对套准控制高精度和高稳定性的要求,提出了一种利用自抗扰控制(active disturbance rejection control,ADRC)技术设计多色套准系统解耦控制器的方法.首先,根据无轴传动模式下多色套准系统的工作机理,建立了多色套准系统的非线性耦合数学模型,并根据ADRC解耦规则推导了套准系统的解耦模型,得到了套准系统的阶数和静态解耦模型.其次,在套准系统阶数和静态解耦模型的基础上,利用ADRC策略对套准系统解耦控制器进行了设计.最后,仿真结果表明,所设计的ADRC解耦控制器能够很好地对各种系统干扰进行补偿,实现了多色套准系统的高精度控制,具有比PID控制器更好的控制性能.     

Robust tuning of dead-time compensators for processes with anintegrator and long dead-time

Presents a simple criterion for tuning a dead time compensator for plants with an integrator and long dead time. The criterion is based on the definition of a closed-loop performance and considers that the model of the process is not precisely known. Using an estimation of the dead time and velocity gain of the plant, the proposed control law has only one tuning parameter that determines the closed-loop performance and robustness. By tuning this parameter it is possible to attain some robust performance specifications. In order to compare the proposed criterion with previous algorithms proposed in the literature, a comparative analysis of robustness is presented. Some simulation examples demonstrate the good properties of the proposed compensator     

基于时延动态补偿的网络控制器的设计

在网络控制系统中由于网络带宽的限制,不可避免地使网络系统产生网络诱导时延,从而导致系统性能下降甚至不稳定。文章针对延时不确定使得Smith预估补偿控制效果差的问题,提出了新的Smith补偿控制算法,根据控制器反馈信息对网络延时进行动态补偿,并与模糊PI控制方法相结合,构成Smith预估模糊PI控制器,使得闭环控制系统即使在模型失配的情况下,仍具有较高的稳定性、较强的鲁棒性。仿真结果表明,该方法可行有效。     

Dynamic anti‐windup method for a class of time‐delay control systems with input saturation

An anti‐windup‐based approach is newly attempted to deal with time‐delay control systems with input saturation. Following the anti‐windup paradigm, we assume that controllers have been designed beforehand for time‐delay control systems based on existing design techniques which will show desirable performance. Then, an additional compensator is designed to provide graceful performance degradation under control input saturation. By taking the difference of controller states in the absence and presence of input saturation as a performance index, a dynamic compensator which minimizes it is derived. The resulting anti‐windup compensator is expressed in plant and controller parameters. The proposed method not only provides graceful performance degradation, but also guarantees the stability of the overall systems. Illustrative examples are provided to show the effectiveness of the proposed method. Copyright © 2000 John Wiley & Sons, Ltd.     

基于系统输出的嵌套饱和系统抗饱和补偿器设计

针对嵌套输入饱和系统的吸引域扩大问题,本文提出了一种基于系统输出的抗饱和补偿器激发策略,将被控系统输出信号经性能补偿器馈入到抗饱和补偿器激发环节中,形成蕴含系统实时性能信息的抗饱和激发新机制,克服了传统抗饱和激发机制无法直接反映系统性能的缺点.基于上述抗饱和控制新框架,本文建立了抗饱和补偿器及性能补偿器存在的充分条件,并依此构建了优化问题求解最优补偿器增益以实现扩大闭环系统吸引域的目的.仿真结果表明本文方法的有效性.     

基于输出反馈的双线性控制系统

非线性和不确定性是制约控制系统性能的主要因素,鉴于此,提出了一种基于偏差分离的双线性输出反馈控制策略,并给出了双线性输出反馈控制系统指数渐近稳定的充分条件.该策略由常规PID控制器和线性补偿控制器两部分组成,在线获取模型偏差信息并进行补偿控制,控制器结构简单,具有较好的工程意义.仿真结果表明了所提出的双线性输出反馈控制策略的有效性.     

数字DC/DC开关电源环路补偿器设计

建立了数字控制DC/DC开关电源闭环系统的s域小信号模型,采用数字重设计法针对给定的系统参数设计了数字补偿器。应用SISO Design Tool仿真平台,在伯德图分析和根轨迹法的基础上设计了连续域的模拟补偿器,并进行了离散化处理。在建立系统s域模型时引入了模数转换器和数字脉宽调制发生器产生的延迟效应,使补偿器的设计考虑了采样速率对系统的影响,改善了传统离散设计的误差。基于数字重设计法构建的数字补偿器实现了对脉宽调制信号的可编程精确控制,保证了变换器闭环工作良好的动态特性。仿真实验结果验证了所设计的数字补偿器的性能。     

Sag feedback based multi-roll coordinating optimal control of a low-tension roll-to-roll system

The roll-to-roll (R2R) system is crucial for manufacturing low-strength sheets. And the speed control of rolls in this multi-roll system has a significant influence on the quality of the fragile sheets. However, the previous system with tension-based feedback control methods might crack the low-tension sheets during transportation. And few studies have carried out other effective control strategies for the R2R system. In this paper, the sag of sheets between rolls is chosen to be the feedback quantity, which provides a low-tension condition. A multi-roll coordinating optimal control method for the R2R system is introduced to keep sags stable by adjusting rolls’ speeds when the linear velocity of the upstream roll changes. A multiple-input multiple-output (MIMO) linear-quadratic-integral (LQI) controller is designed for the system. Several simulations and experiments are performed to confirm its validity. The effects of the hyperparameters in the proposed controller are also investigated. Compared with the series single-input single-output (SISO) PID control method, the proposed control method does better in reducing the speed fluctuation and eliminating error propagation and amplification in the low-tension R2R system. This control method and controller meet the needs of manufacturing low-strength sheets and show potential in enhancing the performance of the R2R system.     

Statistical analysis on the effect of calendering process parameters on the geometry and conductivity of printed patterns

The quality of printed electronics products depends largely on geometrical and morphological characteristics of printed pattern, such as pattern thickness and surface roughness. In this study, we employ the calendering process in order to control the pattern thickness, surface roughness, and conductivity of printed pattern. Both pressure and heat are used to change micro structure as well as morphology of printed layer during the calendering process. The effect of process parameters including temperature, pressure, and speed are investigated by using statistical techniques. Individual effects and interaction effects of the parameters are analyzed with Analysis of Variance (ANOVA) method. The results show that the pattern thickness, surface roughness, and resistivity of printed pattern decrease with increase of temperature and pressure. We also report that temperature is the most influential factor among the parameters. This study demonstrates that the calendering process can be used to enhance the quality of printed electronics products by controlling the surface quality of printed layer.     

基于LMI和IMC的动态反馈抗饱和补偿设计

提出了一种基于线性矩阵不等式(LMI)和内模控制(IMC)的动态反馈抗饱和补偿器的设计方法,为此首先简要地介绍了基于统一框架的抗饱和补偿器设计方法,然后针对原框架计算量庞大的问题,利用模型精确的IMC结构中对象和控制器同时稳定就能保证系统闭环稳定的特性对框架进行改造,并进一步选取了具有(?)2范数形式的性能优化指标,通过整定控制器的方法来优化闭环系统的工作性能,给出了LMI形式的结果．最后给出了运用此方法设计补偿器的一个仿真实例．