Sensor-Aktor-Schicht

Sensor-actor coating – Enabler for temperature control on tool surfaces Temperature control in aluminum die casting is crucial for sustainable processes and high product quality. Knowledge of the temperature in the loaded contact zone is required during production process. Therefore, a sensor coating consisting of a base insulation coating, two sensor layers and an insulating wear protection coating is applied by means of physical vapor deposition (PVD). Temperature measurement bases on the thermoelectric effect. In addition to isolated temperature measurement, the PVD sensor coating can be combined with a thermally sprayed (TS) actor coating. The TS actor coating consists of insulation coatings and a heater coating, generating heat based on the function of a resistive heater. To investigate the sensor-actor function, the combined coating was exposed to thermal cycling tests in this study. The combination of PVD sensor coating and TS actor coating was successfully applied. The TS actor coating tempered the surface with high dynamics. At the same time, the PVD sensor coating measured the temperature at the surface with short response time. In thermal cycling tests, the sensor function showed a comparable temperature profile to reference measurements with an infrared sensor. By means of the sensor-actor coating, temperature can be measured at contact surface and heat can be applied if necessary. The sensor-actor coating offers the opportunity to control temperature in primary and forming processes, for machine elements or for processing temperature-sensitive materials.     

基于模糊内模-PID的包装机热封切刀温度控制

目的 包装机热封切刀温度控制系统存在非线性、大滞后性等特点,传统PID控制的效果也越来越无法满足工艺生产的要求,为了提高包装机热封切刀温度控制的速度和精度,进而提高封口的质量,以提高产品包装效率和品质。方法 在传统的PID控制的基础上,通过结合模糊控制和内模控制理论的先进控制算法,提出模糊内模-PID控制算法的包装机热封切刀温度控制系统。内模控制能够使PID控制器参数进行简化,同时模糊控制的引入能够实现控制器参数的在线调整,将该新型控制算法应用到包装机热封切刀温度控制系统中,并与传统控制进行对比。结果 通过Matlab仿真软件搭建模内模-PID控制的包装机热封切刀温度控制系统仿真平台,仿真结果表明,系统响应速度、精度、超调量、抗扰动能力等比传统控制系统性能更加优良。结论 通过仿真验证了模糊内模-PID控制在热封切刀温度控制系统上的有效性和可行性,能够在温度控制系统中表现出优良的性能指标。     

基于PLC的全自动给袋式包装机称量控制系统研究

目的 针对给袋式包装机称量控制系统中由于物料与电磁振动给料机的振动存在一定非线性与时变性的缺点,提出一种基于PLC的模糊PID称量控制系统。方法 基于PLC的特点设计一种基于PLC的模糊PID控制方法,将称量误差与误差变化率作为系统的输入,采用西门子S7-200系列PLC对称量系统模糊PID控制策略的实现进行分析设计,实现对PID 3个参数的实时改变;基于Matlab对控制系统进行仿真分析,并通过联机运行以验证控制效果。结果 给袋式包装机称量系统的计量偏差不超过0.5%,且仿真结果表明模糊PID较传统PID的控制效果更好。结论 基于PLC的包装机称量系统模糊PID控制系统实际控制稳定,具有很强的鲁棒性,提高了包装机称量过程的稳定性和称量精度,其精度控制为0.5%左右。     

Integration of solar thermal energy into processes with heat demand

An integration of solar thermal energy can reduce the utility cost and the environmental impact. A proper integration of solar thermal energy is required in order to achieve it. The objective of this study is to maximise the solar thermal energy delivered to the process. It is a result of trade-off between the captured solar thermal energy and maximal energy delivered to the process (process demand). Two novel curves are introduced to present this trade-off: (i) The Captured Solar Energy Curve (CSEC), which represents the available amount of heat from solar source and (ii) The Minimal Capture Temperature Curve (MCTC), indicating the minimal temperature making the heat transfer feasible. The crossing point of these two curves presents the minimal temperature of the capture being still sufficiently high to be usable for processes. The suitability of these curves for using in combination with standard heat integration methods is analysed and evaluated. The capture potential is revealed in full when the CSEC and MCTC are used with the Grand Composite Curve. In Total Site Profiles, the heat recovery is first maximised and then the CSEC and MCTC tool is applied. The implementation of CSEC and MCTC approach is illustrated by two case studies.     

An implicit enumeration approach to tolerance allocation in sequential tolerance control

The accuracy and precision of a manufactured dimension is largely dependent on the accuracy and precision of the technological processes selected for its execution. It is not unusual to have available several competing technological processes for execution of each manufacturing operation specified in a process plan, where it is generally assumed that as the precision of the technological process improves, the associated cost and yield of the operation increase. This paper presents an implicit enumeration approach to the selection of an optimum subset of technological processes required to execute a process plan under a. sequential (or adaptive) tolerance control strategy.     

Estimating the drift time for processes subject to linear trend disturbance using fuzzy statistical clustering

Although control charts can notify the state of out-of-control in a process by generating a signal, the indication is usually followed by a considerable amount of delay. Identifying the real time of the change in a process would provide a starting point for further investigation of an assignable cause. This paper addresses the problem of detecting the change point in different processes when the quality characteristics drift steadily away from an in-control state. For this purpose, a fuzzy statistical clustering (FSC) method is used to estimate the drift time in different processes. Since the application of an FSC method requires both in- and out-of-control values of the process parameter, a linear regression model is utilised to estimate the trend rate and then calculate the out-of-control process parameter. Through extensive simulations, the performance of the proposed change point estimation method is analysed and compared with the most recent estimators for several control charts. The results demonstrate that the proposed method is more effective in detecting the drift time through a wide range of trend rates. Furthermore, it is shown that the proposed method offers a higher estimation precision compared to conventional statistical methods.     

基于嵌入式技术的热处理多用炉控制系统

本文介绍了一种基于ARM7微处理器和μC／OS-Ⅱ操作系统的嵌入式热处理多用炉温度控制系统的设计方案。阐述了该系统硬件结构原理和设计方案。详细讨论了系统软件的层次结构、实现流程和主要任务的功能。设计了一种热电偶冷端温度硬件补偿的电路。该温控系统具有测控精度高、实时性好、功能丰富等特点。     

Thermal stress dependence of magnetic hysteretic processes in core–shell nanoparticles

The control of thermal stresses in the core–shell structures is an important task in order to understand their temperature dependent magnetization processes. This paper is dedicated to a theoretical and micromagnetic study of the thermal stresses on the hysteretic processes in core–shell nanoparticles. The analytical model can predict the thermal and elastic behavior of the core–shell nanoparticle supposed to a forced cooling process. The temperature and thermal stresses values obtained by direct computation from the analytical model were used to evaluate the magneto-elastic energy of the core–shell system. A micromagnetic model was used to compute the equilibrium positions of the particle magnetization as function of the applied field. The model allows an evaluation of the increase of the particle coercive field and of the blocking temperature as an effect of the thermal stress.     

An implicit enumeration approach to probabilistic tolerance allocation under conventional tolerance control

The accuracy and precision of a manufactured dimension is largely dependent on the accuracy and precision of the technological processes selected for its execution. It is not unusual to have available several competing technological processes for execution of each manufacturing operation specified in a process plan, where it is generally assumed that, as the precision of the technological process improves, the associated cost and yield of the operation increase. This paper presents an implicit enumeration approach to the selection of an optimum subset of technological processes required to execute a process plan under a conventional tolerance control strategy. A probabilistic approach to the problem is presented and the First Order Second Moment Method (FOSMM) is used to estimate yield for an interdependent system of functional requirements.     

Neural-fuzzy optimization of thick composites curing process

This article addresses the optimization of curing process for thick composite laminates. The proposed methodology aims at the evaluation of the thermal cycle promoting a desired evolution of the degree of cure inside the material. At the same time, temperature overshooting as well as excessive temperature and cure degree gradient through the thickness of the material are prevented. The developed approach is based on the integrated application of artificial neural networks and a fuzzy logic controller. The neural networks promptly predict the behavior of composite material during curing process, while the fuzzy logic controller continuously and opportunely adjusts the proper variations on the imposed thermal cycle. The results highlighted the efficiency of the method in comparison with the cure profiles dictated by the material suppliers. For thick laminates, a reduction of 35% of cure time and improvements of approximately 10% of temperature overshooting was obtained compared to conventional curing cycles. The method was validated by experimental tests.     

基于模糊PID的包装机热封切刀温度控制

目的为了提高包装机热合装置压合袋口的封口质量,采用模糊自适应PID控制方法对热合机热合装置的温度进行精确控制。方法针对食品包装塑料薄膜热封的温度控制,基于模糊自适应PID控制算法设计一种自动包装机热封温度控制系统。采用变论域模糊PID实现控制参数自整定和控制规则的自调整,并将其与传统PID控制进行对比。结果模糊PID控制方法较传统PID控制方法能更稳定地控制加热温度,有效提高了温度控制的响应速度和控制精度。结论该系统在热合装置中能够精确、快速地控制温度,具有应用价值。     

高速飞行器瞬态气动热试验模拟系统

为得到高速飞行器表面各部分的热应力，应变，结构膨胀量等高温力学性能参数，须建立高速飞行器瞬态气动热试验模拟系统。针对高速飞行器气动模拟试验瞬态热控过程所具有变化复杂，高度非线性，瞬变，强耦合的特点，将模拟控制方法应用于瞬态气动热模拟控制系统。该系统能够按照高速飞行器飞行过程中表面热流和温度的瞬态连续变化对气动模拟加热过程实施快速，准确的动态控制。     

基于模糊控制的HVPE生长设备温度控制系统

氢化物气相外延（hydride vapor phase epitaxy,HVPE）工艺的关键是确保加热炉的温场恒定和高精度控制。由于HVPE生长设备温度控制过程涉及多个加热温区,以及温度测量元件和电阻加热炉温度传导引起的延迟,其温度控制存在超调过大、控制精度低和调节时间过长等问题。为实现HVPE生长设备反应室内温度的精准调控,将模糊逻辑应用到PID （proportion integration differentiation,比例积分微分）控制中,设计系统各温区的模糊自适应整定PID控制器。依据实际设备与相应技术要求,设计研发了一套基于PLC （programmable logic controller,可编程逻辑控制器）、温度控制电路以及模糊自适应整定PID控制的HVPE生长设备温度控制系统。Simulink仿真结果与实测结果表明,模糊自适应整定PID控制器可以应用于HVPE生长设备的温度控制系统,且控制效果较好。研究表明,所设计的温度控制算法与温度控制系统能够很好地满足GaN材料生长的工艺要求,具有一定的实用价值。     

基于模糊RBF神经网络的水下机械臂控制研究

针对水下复杂工作环境下机械臂控制性能易受影响,而传统控制方法效果不佳的问题,提出了一种基于模糊RBF（radial basis function,径向基函数）神经网络的智能控制器,用于精确、稳定地控制水下机械臂。考虑到在水扰动环境下,机械臂通常受到附加质量力、水阻力和浮力的影响,运用拉格朗日法和Morison方程,建立包含水动力项的二杆机械臂动力学模型,通过模糊RBF神经网络对水下机械臂动力学方程中的水动力不确定项进行总体识别并拟合,利用模糊系统启发式搜索和RBF神经网络推理速度较快的优点,使水下机械臂系统具有较高的控制精度和较强的自适应性。考虑到水动力项,采用Lyapunov稳定性理论验证了水下机械臂系统的稳定性。最后利用MATLAB对二杆机械臂进行轨迹跟踪控制仿真实验,并对比模糊RBF神经网络与常规RBF神经网络识别方法和传统模糊控制方法的控制效果。仿真结果表明：与常规RBF神经网络识别方法相比,模糊RBF神经网络控制下二杆机械臂关节1的响应时间缩短了91%,相对误差减小了88%,关节2的响应时间缩短了92%,相对误差降低了77%;与传统模糊控制方法相比,关节1的相对误差减小了65%,关节2的相对误差减小了10%。研究结果表明模糊RBF神经网络的控制效果优于常规RBF神经网络识别方法和传统模糊控制方法,可为水下机械臂的控制提供一种精度较高、较有效的方法。     

Fracture toughness of hydroxide catalysis bonds between silicon carbide and Zerodur low thermal expansion glass-ceramic

In many optical and precision engineering applications, low thermal distortion materials need to be bonded together reliably. Since high temperature bonding process ultimately introduce stresses in the bond, rendering it dimensionally instable, room temperature or near room temperature processes are preferred. Low thermal distortion materials such as silicon carbide and low thermal expansion glass ceramics are bonded at room temperature using hydroxide catalysis bonding with a silicate bonding material. The bonding procedure is explained and fracture toughness results are presented for SiC–SiC, Zerodur–Zerodur and SiC–Zerodur bonds. A surface treatment technique for hydrating the SiC surface is presented, which eliminates the need for pre-oxidized SiC surfaces when using HCB bonding. The bonds between surface treated bare SiC surfaces and thermally oxidized SiC surfaces are found to have comparable fracture toughness.     

Optimum heating of cylindrical pressure vessels

A method for determining time-optimum fluid temperature changes during heating of the thick walled cylinder was presented. Optimum fluid temperature changes were determined both for the cylindrical pressure vessels without holes. Heating of the hollow cylinder will be carried out in such a way that the circumferential thermal stress at the inner surface is equal to the allowable stress value. Optimum fluid temperature changes were assumed in the form of simple time functions containing unknown parameters. The unknown parameters were determined from the condition that the circumferential thermal stress at the inner surface of the hollow cylinder without holes is equal to the allowable stress at given time points. An over-determined system of nonlinear algebraic equations was solved for unknown parameters using the least squares method. At first, the thermal stress was calculated using the discrete form of the Duhamel integral. The Finite Element Method (FEM) was used to determine the circumferential thermal stress in the second method. For practical reasons the optimum temperature in the ramp form is preferred. It is possible to increase the fluid temperature stepwise at the beginning of the heating process and then increase the fluid temperature with the constant rate. Because of the possibility of practical implementation a more appropriate is the ramp function for approximating optimum fluid temperature changes.     

Experimental and numerical investigation of the thermal behaviour of polylactic acid during the fused deposition process

Fused deposition modelling (FDM) has become the most popular additive manufacturing process worldwide since the early 2000s. However, limited understanding of its deposition process greatly hinders the future growth of the technology. In order to optimise and control the deposition process, modelling and predicting the thermal behaviour change of the material during such a process is required. In this paper, the thermal behaviour of FDM process was studied both experimentally and numerically; effects of nozzle temperature, platform temperature, extrusion speed, and layer thickness on effective diffusion time, maximum vertical distortion, and maximum thermal stress were evaluated. It is shown that the developed simulation model could predict the effective diffusion time with the error of less than 13% in 6 out of 9 experimental conditions, relatively lower than the existing simulation and theoretical prediction models. Both the experimental and numerical results suggested that polylactic acid would have the longest diffusion time at high nozzle temperature, high platform temperature, low printing speed, and high layer thickness. And the numerical model revealed that reducing extrusion temperature, slowing printing speed, decreasing layer thickness are beneficial of reducing the vertical distortion and residual thermal stress.     

Mikrowellenangepasstes Sintern von Ferriten

Microwave‐aligned sintering of ferrites Sintering of ceramics using microwaves can lead to improved material quality and productivity. The technical implementation of the microwave technology is still lacking because of different temperature distribution inside the specimen due to volumetric heating compared to conventional sintering. The development of microwave‐aligned processes require the determination of the inside temperature distribution by means of mathematic concepts. Therefore a simplified model was set up which consists of a thermodynamic and a heat source model. Heat transfer within the specimen and the periphery will be included. To govern the heat process this model was integrated into a control algorithm. The control concept was proven by experiments using nickel‐zinc‐ferrite. The system provides effective protection against thermal‐runway and incorrect temperature differences in the specimen. Simultaneously changes of temperature depending electromagnetic and thermodynamic material properties can be counter steered.     

基于模糊控制的失重秤粉体包装精度研究

目的 针对失重式包装秤控制系统控制精度低的问题,提出一种提高粉体包装称量精度的控制算法。方法 在传统PI控制基础上,增加智能模糊控制模块,利用模糊控制算法整定PI控制参数,并通过Matlab simulink分析软件对系统进行仿真。结果 相对于传统的PI控制器,模糊PI控制系统达到稳定的时间减少了44%,超调量降低了26%,系统受到干扰后达到稳定的时间减少了30%。结论 模糊PI控制系统稳定,超调量小,抗干扰能力强,能有效提高失重秤的包装控制精度。     

Energy-saving performance and economics of CO2 and NH3 heat pumps with simultaneous cooling and heating applications in food processing: Case studies

The annual saving rates of primary energy and operating cost of NH₃ and CO₂ heat pumps for seven food processes in four characteristic locations with different energy prices in the U.S. are analyzed. The modeled food processes include beer brewing, food pasteurization, fluid milk processing, cheese processing, vegetable and fruit canning, juice canning, and poultry slaughtering. The investigation focuses on the effects of the characteristics of the thermal demands, the location of the proposed systems, and the energy price structure on the savings of primary energy and the operating cost. The results indicate that the characteristics of the thermal demands are the most crucial factor. The energy price structure significantly impacts the operating cost-saving rate. The analysis shows that the annual savings of primary energy can achieve 32% in food pasteurization, 44% in beer brewing, and 35% in fluid milk processing.