Optimal control of an induction heating process using automatic differentiation

We consider an optimal control problem arising in an induction heating process. The main difficulty is to obtain accurate and efficient derivatives of the discrete form of the cost function. In this work we use automatic differentiation. Unlike numerical differentiation based on finite differences, derivatives generated by automatic differentiation are free of truncation error. Numerical results show the performance of the method in terms of accuracy and computational efficiency. Copyright © 2005 John Wiley & Sons, Ltd.     

Flow modeling of the VARTM process including progressive saturation effects

Modeling of vacuum based liquid composite molding methods (e.g., VARTM) relies on good understanding of closely coupled phenomena. The resin flow depends on the preform permeability, which in turn depends on the local fluid pressure; the preform compaction behavior, and the membrane stresses in the vacuum bag. It has also been shown that for many preforms there is a significant unsaturated region behind the flow front, and that the flow in this region affects the overall flow behavior of the process. Studies of preform compaction have shown that the preform stiffness, as well as being non-linear and exhibiting significant hysteresis, is dependant on the fluid saturation. For this reason most researchers model the preform compaction based on the pressure-compaction behavior of saturated preforms during unloading. This assumption leads to an effective discontinuity in preform thickness at the flow front, which is not observed in actual experiments. In this paper an improved compaction model incorporating the saturation dependence of the compaction pressure in the partially saturated region, is used in a one-dimensional model of the VARTM process. The model gives physically more realistic results for the thickness in the flow front region, and an improved model for the consolidation of the preform at the end of infusion.     

Optimal control of an induction heating Process for thixoforming

We investigate in this paper a numerical method to control the temperature of an induction heating process through electric current parameters such as frequency and current voltage imposed to the terminals of the inductor. We consider in this paper an optimal control problem arising in an induction heating process. The control parameters are here the frequency and the voltage supply. More precisely, We seek a sinusoidal voltage function whose amplitude varies in time. For this, we use a two-dimensional induction heating model that involves a phase transition in which the magnetic field has only one nonvanishing component. The procedure can be extended to more sophisticated models without major modification of the optimal control problem. We present a numerical control algorithm and discuss numerical experiments that prove the efficiency of the procedure.     

Rapid reinforcement for fusion mass-spliced fibers using low-power induction heating

A rapid reinforcement method using low-power induction heating is developed. The reinforcement of a mass-spliced fiber ribbon unit comprising five graded-index multimode fibers was completed in 30 sec with good performance by supplying 30 W of electric power.     

Fatigue damage development in new fibre metal laminates made by the VARTM process

This paper investigates the tensile and fatigue properties of a newly developed fibre metal laminate (FML) manufactured using the vacuum assisted resin transfer moulding (VARTM) method. This manufacturing method allows the glass fibre reinforced epoxy and 2024‐T3 aluminium FML to be prepared at lower cost than conventionally manufactured FMLs. However, in order for the resin to infiltrate the FML, the metal sheets need to be perforated. These perforation holes act as crack initiators and reduce the FML's performance. Tension and fatigue test results of three different designs are reported and compared to mechanical property predictions. Additionally, single sheet Al alloy specimens were tested in order to analyse the influence of the drilling method.     

Rapid welding of stainless steel wires using ultra-high frequency induction heating

In this study, JIS SUS202 stainless steel wires are rapidly welded by induction heating using a current at a frequency of 2?MHz. The effects of the heating parameters on the mechanical properties and microstructures of the joint are investigated. After induction welding, the main structures in the joint of the 202 stainless steel wires are austenite and ferrite. The amount of ferrite increases by increasing the heating temperature or heating time. Moreover, the tensile strength of the joint is superior for a higher welding temperature.     

Multiresponse optimization of a multistage manufacturing process using a patient rule induction method

Most manufacturing industries produce products through a series of sequential stages, known as a multistage process. In a multistage process, each stage affects the stage that follows, and the process often has multiple response variables. In this paper, we suggest a new procedure for optimizing a multistage process with multiple response variables. Our method searches for an optimal setting of input variables directly from operational data according to a patient rule induction method (PRIM) to maximize a desirability function, to which multiple response variables are converted. The proposed method is explained by a step-by-step procedure using a steel manufacturing process as an example. The results of the steel manufacturing process optimization show that the proposed method finds the optimal settings of input variables and outperforms the other PRIM-based methods.     

Controlling vibrations of a cutting process using predictive control

Unwanted vibrations in machining are detrimental to the equipment and the quality of the result. Notably chatter vibrations due to the regenerative effect are difficult to control and limit the achievable results. Typically, active and passive means are employed to prevent chatter from happening. This work proposes a predictive control strategy that actively uses information about the system past to predict future disturbances. Using those predicitions allows to counter the regenerative effect more effectively. The strategy is tested in simulation and improves the dynamic stability of the system greatly. It is robust with respect to quantitative errors in the disturbance predictions.     

The structure and properties of NiAl formed by SHS using induction heating

Intermetallic NiAl has the potential to be used for elevated temperature applications. To date different ignition techniques have been utilized to synthesize NiAl and produce coatings. Self-propagating high-temperature synthesis (SHS) has been developed as a relatively simple route to obtain intermetallics. This paper considers using induction heating to preheat and ignite the synthesis directly and investigates the effect of processing parameters on the phase transformation, microstructures and properties of Ni/Al compacts synthesized by SHS. The results show that single phase NiAl can be produced by induction heating whilst processing parameters such as heating rates and green densities have a significant effect on the properties and structures of sintered products.     

Computer modeling of temperature field in sintering carbide composites using induction and radiation heating

A computer model has been elaborated for the temperature field in a high-temperature furnace for sintering ceramic powder samples under induction and radiation heating conditions. For numerical solution of the set of equations describing the induction and radiation heating processes a finite-element method is used in combination with a finite-difference procedure in time, which is based on Newton-Raphson technique, and a radiosity method is used in modeling the radiation heat transfer. The temperature field in the furnace in the process of sintering has been numerically studied. The numerical results are compared to the data of temperature measurements at the infiltrator surface during the sintering of a composite blend with a silicon-carbide matrix. Based on the agreement between the calculated and experimental results, the computer model is inferred to be adequate.     

内加热固化环氧玻璃钢管制造系统

为提高环氧玻璃钢管生产的效率和质量,研制了仅用一台机床就能完成管道缠绕、固化和脱膜三道工序的集成制造系统.介绍了制造系统机床结构和工作原理,建立了缠绕运动控制和管道固化过程的数学模型.缠绕部分采用嵌入式多任务运动控制器实现主轴和小车的同步运动控制和缠绕逻辑控制.固化部分采用内加热固化工艺,由嵌入式工控机和PLC实现固化控制.利用有限元软件对管道固化过程的温度和固化度分布进行了数值模拟以优化固化工艺参数,并对该系统生产的管道进行了性能检测试验.实践应用表明采用内加热固化工艺可实现环氧玻璃钢管高效工业化制造.     

Analytical equivalent impedance for a planar circular induction heating system

A set of analytical expressions is derived for the equivalent impedance in a planar circular induction heating system, used for example in home appliances. The induction system consists of an n-turn planar winding loaded by a conductive material. Expressions that describe the frequency dependence of impedance are provided. The influence of load conductivity, load permeability, and geometrical dimensions is also considered. Validation of the proposed model is carried out through experimental measurements.     

Stability of cylindrical shells in axial compression and heating in a set of localized regions

A theoretical and experimental study is made of the static stability of a cylindrical shell compressed in the axial direction during rapid heating in a set of small circular regions. The approach used is based on the Bubnov—Galerkin method and introduction of the concept of generalized solutions for stability equations with variable parameters, which makes it possible to find an analytic solution to the problem. Satisfactory agreement is obtained between the analytical and experimental results.     

Thermal and electromagnetic parameters of a high-frequency discharge in induction heating of a gas

A procedure for determining the thermal and electrophysical parameters of an hf induction discharge burning inside a short induction heater is proposed.Kazan Technological University. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 2, pp. 248–252, March–April, 1995.     

On-chip cell sorting system using laser-induced heating of a thermoreversible gelation polymer to control flow

We have developed a microfabricated fluorescence-activated cell sorter system using a thermoreversible gelation polymer (TGP) as a switching valve. The glass sorter chip has Y-shaped microchannels with one inlet and two outlets. A biological specimen containing fluorescently labeled cells is mixed with a solution containing a thermoreversible sol-gel polymer. The mixed solution is then introduced into the sorter chip through the inlet. The sol-gel transformation was locally induced by site-directed infrared laser irradiation to plug one of the outlets. The fluorescently labeled target cells were detected with sensitive fluorescence microscopy. In the absence of a fluorescence signal, the collection channel is plugged through laser irradiation of the TGP and the specimens are directed to the waste channel. Upon detection of a fluorescence signal from the target cells, the laser beam is then used to plug the waste channel, allowing the fluorescent cells to be channeled into the collection reservoir. The response time of the sol-gel transformation was 3 ms, and a flow switching time of 120 ms was achieved. Using this system, we have demonstrated the sorting of fluorescent microspheres and Escherichia coli cells expressing fluorescent proteins. These cells were found to be viable after extraction from the sorting system, indicating no damage to the cells.     

Measurement of localized heating in the focus of an optical trap

Localized heating in the focus of an optical trap operating in water can result in a temperature rise of several kelvins. We present spatially resolved measurements of the refractive-index distribution induced by the localized heating produced in an optical trap and infer the temperature distribution. We have determined a peak temperature rise in water of 4 K in the focus of a 985-nm-wavelength 55-mW laser beam. The localized heating is directly proportional to power and the absorption coefficient. The temperature distribution is in excellent agreement with a model based on the heat equation.     

Wettability control by laser texturing process generating localized gold nanoparticles on polymeric thin films

In this work a new approach is introduced for surface properties control by laser texturing process. By UV laser irradiation, we are able to control the surface wettability of a chitosan polymeric film in which is introduced a chloroauric acid salt by immersion. Specifically the UV irradiation is responsible for the creation of gold nanoparticles at the irradiated surface of the polymeric film. This photolytic process allows us to localize and design accurately surface patterns and moreover to tune metallic particle size in the range of nanoscale. After the characterization of our gold textured surfaces by atomic force and scanning electron microscopies, we demonstrate the link between wettability surface properties and gold nanoparticles size. The experimental results indicate the influence of the laser intensity, the irradiation time and the polymer film thickness (by increasing the gold concentration) on the gold nanoparticle density and size.     

嵌入加强筋的缝合泡沫夹芯结构复合材料VARTM工艺树脂充填模拟及验证

在缝合泡沫夹芯结构复合材料的泡沫中嵌入轻质的加强筋板,可以在不增加缝合密度并且在只增加较少质量的前提下,增强复合材料制品整体的强度和刚性。文中对真空辅助树脂传递模塑成型(VARTM)工艺树脂在嵌入加强筋的缝合泡沫夹芯结构复合材料预成型体中充填过程进行模拟和验证研究。采用一种矩形流道模型代替沿加强筋与泡沫空隙间的树脂流动,并对其等效渗透率及孔隙率进行计算;通过PAM-RTM软件模拟了嵌入加强筋板的缝合泡沫夹芯结构VARTM工艺的树脂充填过程,并建立了流动可视化实验装置与模拟对比,结果表明模拟与实验相当吻合。而模拟与实验的结果均表明加强筋的引入可以在局部加强树脂沿厚度方向的流动,但是会延缓树脂对整个预成型体的充填。     

Intelligent heating control of a new ice-free anemometer

The wind industry has grown over the years along with the collective desire to produce clean energy. High wind potential sites are often located in northern regions where harsh climatic conditions arise. The performance of anemometers, which provide essential measurements to wind turbine operation and wind resource assessment, is then jeopardized by ice build-up and snow accumulation. These conditions result in the need for heated instruments able to remain ice-free regardless of weather conditions while minimizing energy consumption. The main objective of this work was to develop an intelligent heating control for a new generation of ice-free anemometers. The controller is based on vision recognition of ice build-up on the cups of the anemometer using a neural network. Heating power is applied according to the icing state and the icing history of the instrument. Primary results have shown that, for a completely ice-free performance, the developed controller uses an average of less than two thirds of the energy consumed by common control systems similar to those used by other ice-free anemometers available on the market.     

Statistical process monitoring using an empirical Bayes multivariate process control chart

In this paper, we describe the theory underlying an empirical Bayesian approach to monitoring two or more process characteristics simultaneously. If the data is continuous and multivariate in nature, often the multivariate normal distribution can be used to model the process. Then, using Bayesian theory, we develop techniques to implement empirical Bayes process monitoring of the multivariable process. Lastly, an example is given to illustrate the use of our techniques. Copyright © 2001 John Wiley & Sons, Ltd.