Planning performance based contracts of repairable system using discrete event simulation

This paper investigates a discrete event simulation approach for managing performance based contracts of repairable systems. We focus on an integrated service delivery environment where the manufacturer develops capital-intensive systems and also provides after-sales support. We propose a simulation model to calculate system availability comprehending four performance drivers: life time distribution, repair time distribution, spare parts inventory, and repair facility. This simulation model allows the service supplier to minimize the total cost by optimizing the four performance drivers. In this simulation model, the failure time and repair time can follow arbitrary distribution. This will allow the customer to monitor the supplier’s service through comparing the actual availability and its theoretical value. The costs of three maintenance policies also can be studied under the performance based contracts framework. Two cases are considered in this paper. One is a system containing single unit, one warehouse, and one repair center. Another is a system containing two fleets with different installed units, two spare part warehouses with one for each fleet, and a central repair depot.     

Modeling and optimization of a reluctance accelerator using DOE-based response surface methodology

This paper introduces experiment-based modeling and optimization of a reduced-scale Electromagnetic launcher (EML) using the Design of experiments (DOE) technique. Response surface models describing the velocity and kinetic energy of the launched projectile were developed using the Box–Behnken method with design variable transforms, and an Analysis of variance (ANOVA) was conducted to refine the models by removing statistically insignificant terms. A bi-objective optimization problem with the maximum velocity and maximum kinetic energy as objects was considered, and a Pareto front was obtained using the generated response surfaces as the solution of the problem. Verification tests on the optimal design points were conducted to demonstrate the validity of the developed models.

     

Multiple-response optimization for micro-endmilling process using response surface methodology

In the present trend, new fabrication methods for producing miniaturized components are gaining popularity due to the recent advancements in micro-electro mechanical systems. Micro-machining differs from the traditional machining with the small size tool, resolution of x?Cy and z stages. This paper focuses RSM for the multiple response optimization in micro-endmilling operation to achieve maximum metal removal rate (MRR) and minimum surface roughness. In this work, second-order quadratic models were developed for MRR and surface roughness, considering the spindle speed, feed rate and depth of cut as the cutting parameters, using central composite design. The developed models were used for multiple-response optimization by desirability function approach to determine the optimum machining parameters. These optimized machining parameters are validated experimentally, and it is observed that the response values are in good agreement with the predicted values.     

Evaluation of flow characteristics in labyrinth weirs using response surface methodology

Labyrinth weirs can increase the flow discharge capacity for a specific head and width by increasing the weir length. This paper studies the flow behavior of labyrinth weirs using Flow-3D® software. The main goal is to evaluate the capability of the response surface methodology (RSM), especially central composite design (CCD), to describe the performance of labyrinth weirs. Traditional and RSM-CCD methodologies are applied using experimental data of previous researchers and numerical data of the present study, respectively. Results show that RSM-CCD can produce an acceptably accurate model for the discharge coefficient of labyrinth weirs with only a small fraction of the data required for the traditional model. In addition, the discharge coefficient of a labyrinth weir decreases by increasing head and decreasing sidewall angle due to the inflow contraction and nappe interference in inlet and outlet cycles, respectively. The discharge efficiency can be up to 4.5 times higher for a labyrinth weir compared to a linear weir. Finally, a new method is introduced for designing labyrinth weirs.     

西门子S7-200PLC在冲床送料及加工中的应用

针对空调电动机端盖类零件,利用西门子S7-200PLC(CPU224)对多工位连续模冲床的送料机构及加工实现自动控制,提高了冲床送料及加工的自动化水平和可靠性.     

Technology for the control of quality in automated manufacturing

This paper reviews the present status of technology for the quality assurance of products produced by flexible automation parts-manufacturing. Two examples of practical systems that represent typical products (rotational and prismatic work-pieces) are described with particular emphasis on control functions relevant to product quality     

PDM and ERP integration methodology using digital manufacturing to support global manufacturing

Global manufacturing companies must implement manufacturing engineering with proper consideration given to the manufacturing process and resources that are appropriate for the particularities of each manufacturing site. Particularly for effective enterprise resource planning (ERP) system implementation under a global manufacturing environment, the product data management (PDM) integration for product data is one of the important keys to success. For such product data integration, engineering bill of materials (EBOM) needs to be transformed to manufacturing bill of materials (MBOM), but the MBOM transformation must be done in such a way as to fit the particularities of each manufacturing site. In this process, a methodology appropriate for integration and transformation is required. This paper proposes digital manufacturing as the key tool of data integration between PDM and ERP. Digital manufacturing, as a technology possessing the physical and logical computer modeling and simulation technique for actual manufacturing, provides the methodology for transforming EBOM to MBOM that fits the particularities of each manufacturing site, based on the process and resource models which reflect the particularities of each manufacturing site. It also provides the methodology for MBOM verification and the process and resource model integration. Using such method, the MBOM and the process and resource data, verified and appropriate for each manufacturing site, can be sent to the ERP system.     

Optimization on wear performance of UHMWPE composites using response surface methodology

This study examined the wear characteristics of ultra-high molecular weight polyethylene (UHMWPE) reinforced with talc particles. Analysis of variance (ANOVA) was used to construct empirical models to show the connection between control factors (filler loading, load and sliding speed) and responses (wear rate and average coefficient of friction (COF)) of UHMWPE. Response Surface Methodology (RSM) was employed to project the optimization of the control variables in order to reduce the wear of UHMWPE. It was discovered that the rate of wear and the average COF of UHMWPE could be minimized by the inclusion of talc. The SEM analyses of the worn surfaces and transfer films indicated that the degree of wear on the surface of the UHMWPE was reduced.     

A methodology for the implementation of automated measuring stations in flexible manufacturing systems

This paper presents a methodology for the inclusion of an automated measuring station in an existing flexible manufacturing system (FMS) by treating the measuring station as a workstation integrated into the FMS. This approach causes minimal distortion of the FMS work functions and does not depend on the control algorithms implemented on the system. A case study based on an FMS located at the Aeronautical Centre is presented. The FMS used in the case study is called CFF-ETSIA. This system contains the main elements needed in a FMS: two computer numerical control machine tools for machining and two industrial robots for handling and manipulating. The measuring station in the case study is implemented with one of the robots used to perform the necessary actions of measurement and manipulation.     

Effect of obstacle position on attached cavitation control through response surface methodology

Journal of Mechanical Science and Technology - The span-wise obstacle on the suction surface of a hydrofoil has been verified to be an effective passive control method for cloud cavitation. The...     

Parametric optimization of ultrasonic metal welding using response surface methodology and genetic algorithm

This paper focuses on the development of an effective methodology to determine the optimum welding conditions that maximize the strength of joints produced by ultrasonic welding using response surface methodology (RSM) coupled with genetic algorithm (GA). RSM is utilized to create an efficient analytical model for welding strength in terms of welding parameters namely pressure, weld time, and amplitude. Experiments were conducted as per central composite design of experiments for spot and seam welding of 0.3- and 0.4-mm-thick Al specimens. An effective second-order response surface model is developed utilizing experimental measurements. Response surface model is further interfaced with GA to optimize the welding conditions for desired weld strength. Optimum welding conditions produced from GA are verified with experimental results and are found to be in good agreement.     

An investigation into the aspheric ultraprecision machining using the response surface methodology

Aspheric ultraprecision machining is increasingly important to the manufacturing industry. The performance of aspheric optical components manufactured by mass-production is largely dependent on the form error of molds and dies. It is believed that productivity of a machining process could be improved if the form error is predictable. In this study, the response surface methodology (RSM) was employed to derive predictive models of rough and compensation cuttings for an aspheric convex mold, with an outer aperture of ϕ12 mm and curve height of 0.6 mm. Two control factors, the depth of cut and spindle speed, were selected for study. The 2K factorial design with four center points was adopted. Two linear models for both rough and compensation cuttings were derived experimentally based on the form errors obtained. The models adequacy was examined through ANOVA (analysis of variance) results for the surface responses. It was found that the linear model of rough cutting is adequate, reflected by the significant regress coefficients and the high R² value. However, the model of compensation cutting was found to be inadequacy.     

System identification of a composite plate using hybrid response surface methodology and particle swarm optimization in time domain

Material properties of composites are identified using a novel hybrid RSM–PSO method in this paper. Different response surface methodology (RSM) methods and particle swarm optimization (PSO) methods are studied initially on a 4 degrees-of-freedom (4DOF) dynamic system on their performance in terms of speed and accuracy. The best combination is used as a hybrid RSM–PSO method to evaluate the performance on system identification of an orthotropic plate along with a 4DOF dynamic system and an isotropic plate. The novelty of the present paper is to identify the composite plate material properties using RSM methods based on time domain signals, which is not hitherto reported in the literature. Also, whereas previous papers have used full factorial design for system identification, here CCDI is used. The input factors (design variables) are the system parameters which are to be identified and the response (objective function) is error sum-of-square of acceleration response with respect to new test system. The performance of the proposed method is also evaluated with the addition of 5% Gaussian noise to simulate the experimental errors. The system parameters of the orthotropic plate were identified with 0% and 0.25% average prediction error with zero and 5% addition of noise respectively by the proposed hybrid RSM–PSO method. It is also showed a much better performance and robustness to noise addition when compared to the other RSM methods in the literature.     

Predicting surface quality of γ-TiAl produced by additive manufacturing process using response surface method

Electron beam melting (EBM) has been found to be a promising technology for producing complex shaped parts from gamma titanium aluminide alloys (γ-TiAl). The parts produced by this process are projected to have dimensions very close to the desired final shapes. However, the surface roughness of the parts produced by EBM is excessively rough. In many applications, it is necessary to improve the quality of manufactured parts using a convenient post process. This paper determines process parameters of end milling when it is used as a post process for the parts produced by EBM. Design of experiments has been used to study the effect of the selected input parameters of end milling (spindle speed, feed rate, depth of cut and coolant type) on the surface roughness of γ-TiAl parts. Response surface methodology is used to develop a predictive model for surface roughness. Effects of the selected milling process are investigated. This paper also optimizes the selected process parameters to minimize the value of the obtained surface roughness.     

Safety analysis of discrete event systems using a simplified Petri net controller

This paper deals with the problem of forbidden states in discrete event systems based on Petri net models. So, a method is presented to prevent the system from entering these states by constructing a small number of generalized mutual exclusion constraints. This goal is achieved by solving three types of Integer Linear Programming problems. The problems are designed to verify the constraints that some of them are related to verifying authorized states and the others are related to avoiding forbidden states. The obtained constraints can be enforced on the system using a small number of control places. Moreover, the number of arcs related to these places is small, and the controller after connecting them is maximally permissive.     

Comparison between response surface methodology and radial basis function network for core-center drill in drilling composite materials

Drilling using twist drill is the most frequently used secondary machining for fiber-reinforced composite laminates and delamination is the most important concern during drilling. The drill design and drilling parameters associated with thrust distribution on the drilling-induced delamination are presented. The core-center drill has been found to be more advantageous than the core drill in reference and practice experiences. Response surface methodology (RSM) is a very practical, economical, and useful tool for the modeling and analysis of experimental results using polynomials as local approximations to the true input/output relationship. Due to the radial basis function network’s (RBFN) fast learning speed, simple structure, local tuning, and global generalization power, researchers in the field of manufacturing engineering have been using RBFN in nonlinear manufacturing studies. The present paper compares these two techniques using various drilling parameters (diameter ratio, feed rate, and spindle speed) to predict the thrust force for a core-center drill in drilling composite materials. The obtained results indicated that RBFN is a practical and an effective way for the evaluation of drilling-induced thrust force.     

Synthesis of feedback control elements for discrete event systems using Petri net models and theory of regions

This paper describes a method for constructing a Petri-net-based controller for a discrete event system (DES) modelled by a Petri net. Assuming that an uncontrolled Petri net model of the DES and a set of forbidden state specifications are given, feedback control elements, i.e. a set of places and related transitions, with initial marking, are computed using the theory of regions, which is a formal synthesis technique for deriving Petri nets from automaton-based models. When feedback control elements are added to the uncontrolled Petri net model, the controlled (closed-loop) Petri net model of the system is obtained. The controlled Petri net model obtained is maximally permissive while guaranteeing that forbidden states do not occur. The proposed method is computationally efficient and does not suffer from the state explosion problem. Two examples are provided to show the applicability of the proposed method.     

Application of response surface methodology in controller fine-tuning

Despite the developments in advanced control techniques, the traditional PID controller is still being used in the majority of industrial processes. However, due to process non-linearities and modelling difficulties, common tuning techniques often yield tuning parameters that are not optimum. The subsequent fine-tuning stage is time-consuming because it is performed by trial and error. Several researchers have suggested that a statistically designed, experimental approach to controller tuning may be fruitful, e.g. Box and Kramer [1].

Using Response Surface Methodology (RSM), a model of the system performance as a function of the tuning parameters can be obtained. RSM can systematically lead the operator to improved tuning and provide a picture of the sensitivity of the process to the tuning parameters. The application of this technique in the fine-tuning of a simulated and real-time process is shown.