Numerical Control

This paper is the latest in a short series on the origins, processes and effects of performativity in the public sector. Performativity, it is argued, is a new mode of state regulation which makes it possible to govern in an 'advanced liberal' way. It requires individual practitioners to organize themselves as a response to targets, indicators and evaluations. To set aside personal beliefs and commitments and live an existence of calculation. The new performative worker is a promiscuous self, an enterprising self, with a passion for excellence. For some, this is an opportunity to make a success of themselves, for others it portends inner conflicts, inauthenticity and resistance. It is also suggested that performativity produces opacity rather than transparency as individuals and organizations take ever greater care in the construction and maintenance of fabrications.

We have used a differential spectroscopy technique to measure and characterize the optical absorbance spectrum of a 2500 A symmetrically strained Ge Si superlattice. Using X-ray diffraction we found that the average periodicity of the superlattice in the growth direction is 11 atomic layers, to measure the strain and disorder of the superlattice, and to show that the superlattice is pseudomorphic with its Geo.75Sio.25 buffer substrate with a precision of 2 x 10 3. At room temperature, the absorption coefficient increases linearly with photon energy above the band edge, exceeding 104 cm ~ at 1.55 lam. Because the band-edge electronic structure is fundamentally different in nature from either that of Si or Ge, we argue that conventional models for absorption versus photon energy in bulk semiconductors may not apply to this kind of Ge-Si superlattice.

This paper investigates the capital structure choices that firms make in their initial year of operation, using restricted-access data from the Kauffman Firm Survey. Contrary to many accounts of startup activity, the firms in our data rely heavily on external debt sources such as bank financing, and less extensively on friends and family-based funding sources. This fact is robust to numerous controls for credit quality, industry, and business owner characteristics. The heavy reliance on external debt underscores the importance of well functioning credit markets for the success of nascent business activity.

The late-stage demixing following spinodal decomposition of a three-dimensional symmetric binary fluid mixture is studied numerically, using a thermodynamicaly consistent lattice Boltzmann method. We combine results from simulations with different numerical parameters to obtain a unprecendented range of length and time scales when expressed in reduced physical units. (These are the length and time units derived from fluid density, viscosity, and interfacial tension.) Using eight large (256 3 ) runs, the resulting composite graph of reduced domain size l against reduced time t covers 1 l 10 5 , 10 t 10 8 . Our data is consistent with the dynamical scaling hypothesis, that l(t) is a universal scaling curve. We give the first detailed statistical analysis of fluid motion, rather than just domain evolution, in simulations of this kind, and introduce scaling plots for several quantities derived from the fluid velocity and velocity gradient fields. Using the conventional definition of Reynolds number for this problem, Re φ = ldl/dt, we attain values approaching 350. At Re φ 100 (which requires t 10 6 ) we find clear evidence of Furukawa's inertial scaling (l ∼ t 2/3 ), although the crossover from the viscous regime (l ∼ t) is both broad and late (10 2 t 10 6 ). Though it cannot be ruled out, we find no indication that Re φ is self-limiting (l ∼ t 1/2 ) at late times, as recently proposed by Grant and Elder. Detailed study of the velocity fields confirm that, for our most inertial runs, the rms ratio of nonlinear to viscous terms in the Navier Stokes equation, R 2 , is of order ten, with the fluid mixture showing incipient turbulent characteristics. However, we cannot go far enough into the inertial regime to obtain a clear length separation of domain size, Taylor microscale, and Kolmogorov scale, as would be needed to test a recent 'extended' scaling theory of Kendon (in which R 2 is self-limiting but Re φ not). To obtain our results has required careful steering of several numerical control parameters so as to maintain adequate algorithmic stability, efficiency and isotropy, while eliminating unwanted residual diffusion. (We argue that the latter affects some studies in the literature which report l ∼ t 2/3 for t 10 4 .) We analyse the various sources of error and find them just within acceptable levels (a few percent each) in most of our datasets. To bring these under significantly better control, or to go much further into the inertial regime, would require much larger computational resources and/or a breakthrough in algorithm design. † Present address: Optics Section,

In the domain of manufacturing, computer numerically controllers (CNC) technology is a major contributor to the production capacity of the enterprises. The advances in CNC technology coupled with enhancements in computing systems have provided the basis to re-examine the way in which computer-aided systems (CAx) can be used to enable global manufacturing. Interoperability of the various components of the CAx chain is therefore a major prerequisite for manufacturing enterprises for becoming strategically agile and consequently globally competitive. Being interoperable, resources can be utilized interchangeably in a plug-and-produce manner. Over the last 8 years the eminence of a STEP standard for machining entitled STEP-NC (numerical control) has become a well-known vehicle for research to improve the level of information availability at the CNC machine tool. In this paper, the authors introduce the background to the evolution of CNC manufacturing over the last 50 years and the current standards available for programming. A review of the literature in interoperable CNC manufacturing is then provided relating to milling, turn-mill and other NC processes. The major part of the paper provides a strategic view of how interoperability can be implemented across the CAx chain with a range of standards used to regulate the flow of information. Finally, the paper outlines the advantages and major issues for future developments in interoperability, identifying future key requirements and limiting factors.

STEP-NC (formalized as ISO 14649 and ISO 10303 AP238) is a new interface (or language) standard for the CAD -CAM -CNC chain, currently under establishment by ISO TC184 SC1 and SC4. Upon completion, it will replace ISO 6983, so called M & G codes used for CNC since 1950s. As the new language is being established, a new CNC controller called STEP-CNC (STEP-compliant CNC), capable of carrying out various intelligent tasks using the new language as an input, receives worldwide attention. Shop-floor programming (SFP) system is a computer-assisted part programming system interfaced with STEP-CNC. Its primary function is to generate part program in ISO 14649 (or STEP AP238) to machine the part geometry given by STEP AP203 or AP224 file. In this paper, we first present an architecture for the SFP system, followed by implementation technology including: (1) STEP physical file interpretation, (2) feature recognition, (3) process planning, (4) part program generation, and (5) verification. The developed methodology was implemented in a prototype called PosSFP, and tested with Korea STEP-NC system. q

This paper studies a class of real-rational matrix bilateral Diophantine equations (BDE) arising in numerous control problems. A necessary and sufficient solvability condition is derived in terms of state-space realizations of rational matrices involved in the equation. This condition is given in terms of a constrained matrix Sylvester equation and is numerically tractable. An explicit state-space parametrization of all solutions

In analyzing the transcriptional networks that regulate development, one ideally would like to determine whether a particular transcription factor binds directly to a candidate target promoter inside the living embryo. Properties of the Caenorhabditis elegans elt-2 gene, which encodes a gut-specific GATA factor, have allowed us to develop such a method. We previously have shown, by means of ectopic expression studies, that elt-2 regulates its own promoter. To test whether this autoregulation is direct, we fused green fluorescent protein (GFP) close to the C terminus of elt-2 in a construct that contains the full elt-2 promoter and the full elt-2 zinc finger DNA binding domain; the construct is expressed correctly (i.e., only in the gut lineage) and is able to rescue the lethality of an elt-2 null mutant. Multicopy transgenic arrays of this rescuing elt-2::GFP construct were integrated into the genome and transgenic embryos were examined when the developing gut has 4 -8 cells; the majority of these embryonic gut nuclei show two discrete intense foci of fluorescence. We interpret these fluorescent foci as the result of ELT-2::GFP binding directly to its own promoter within nuclei of the developing gut lineage. Numerous control experiments, both genetic and biochemical, all support this conclusion and support the specificity of the binding. The approach should be applicable to studying other transcription factors binding target promoters, all within the living C. elegans embryo.

Selenium shares many chemical facets with sulphur but differs from it in the redox potential, especially of the Se 2− /S 2− oxidation state. The higher chemical reactivity of the deprotonated selenol has been used by Biology in the synthesis of the amino acid selenocysteine and its DNA-encoded incorporation into specific positions of proteins to enhance their structural role or their activity. Since selenocysteine is a steric isomer of cysteine, numerous control mechanisms have been developed which prevent cross-intrusion of the elements during biosynthesis and insertion. As described in this review, these fidelity steps occur at the genetic, biochemical and physiological level.

Stepping motors are widely used in robotics and in the numerical control of machine tools where they have to perform high-precision positioning operations. However, the variations of the mechanical configuration of the drive, which are common to these two applications, can lead to a loss of synchronism for high stepping rates. Moreover, the classical open-loop speed control is weak and a closed-loop control becomes necessary. In this paper, fuzzy logic is applied to control the speed of a stepping motor drive with feedback. A neuro-fuzzy hybrid approach is used to design the fuzzy rule base of the intelligent system for control. In particular, we used the ANFIS methodology to build a Sugeno fuzzy model for controlling the stepping motor drive. An advanced test bed is used in order to evaluate the tracking properties and the robustness capacities of the fuzzy logic controller.

Several methods have been developed for the computerized generation of space-filling curves, but these curves have never been used for NC tool-path generation. The paper discusses the application of space-filling curves as tool paths for sculptured-surface machining. Tool paths that are space-filling curves, single-direction conventional paths, and 2-direction conventional paths are compared. The efficiency ratings of the paths require further testing, but the preliminary conclusions are favourable for space-filling curves.

In this study, we have investigated the effects of different insert radii of cutting tools, different depths of cut and, different feed rates on the surface quality of the workpieces depending on various processing parameters. Properly, the AISI 1030 steel is processed at a digitally controlled computerised numerical control(CNC) turning lathe without using cooling water with three different insert radii (0.4, 0.8, and 1.2 mm) of cemented carbide cutting tools, coated with three layer coating materials (outermost is TiN) applied by the chemical vapour deposition CVD technique. The effects of five different depths of cut (0.5, 1, 1.5, 2, 2.5 mm) and five different feed rates/advancing steps (0.15, 0.2, 0.25, 0.30, 0.35 mm/rev) on the surface roughness values have been investigated by a turning process while from the cutting parameters the cutting speed is kept constant at (300 m/min). It is seen that the insert radius, feed rate, and depth of cut have different effects on the surface roughness. In the experiments, the minimum average surface roughness has been obtained using the cutting tools of maximum insert radius (1.2 mm). The surface roughness have been improved by 293% when the insert radius (0.4 mm) was increased by 200% (1.2 mm). When the feed rate (0.35 mm/rev) was reduced by 133% (0.15 mm/rev), the surface roughness have been improved by 313%, and by reducing the depth of cut (0.5 mm) by 400% (0.25 mm), an amelioration of 23% has been obtained on the surface roughness.

Multiphase processes, such as the uptake of gases by clouds or the production of gas phase halogens from particulate halides are of increasing importance for the understanding of the tropospheric system. Mass transfer and chemical reactions modify the concentrations of stable compounds and oxidants in either phase. The parcel model SPACCIM is presented which combines a complex multiphase chemical model with a detailed microphysical model. For this purpose, a new coupling scheme is implemented. The description of both components is given for a fine-resolved particle/drop spectrum. The SPACCIM approach allows the coupling of multiphase chemical models with microphysical codes of various types. An efficient numerical solution of such systems is only possible utilizing the special structure. An implicit time-integration scheme with an adapted sparse solver for the linear systems is applied. Its numerical efficiency and robustness is analyzed for two scenarios and versions of different complexity of the multiphase chemistry mechanism CAPRAM. The sensitivity of simulation results against variations in the particle/droplet size resolution, the coupling time step and numerical control parameters is discussed. Guidelines for an ''optimal'' choice of control parameters are derived from this sensitivity study. The coupling scheme operation is always robust and reliable. Model simulations are compared with several measurements from the FEBUKO field campaign. Simulated and measured results show a reasonable agreement. r

Almost all of the existing studies on product architecture adopt the research framework of comparing the advantages and disadvantages of modular architecture with those of integral architecture. In this paper, we attempt to propose an evolutionary perspective of product architecture. In order to consider the evolution of a product architecture, we analyze the history of Fanuc numerical controllers regarding the evolution of NC architecture from 1962 to 1997. Then we can derive the following hypotheses concerning the evolution of the product architecture. First, the product architecture basically evolves from the integral architecture to the module architecture, and then in the direction of open architecture. Second, in specific circumstances this change does not always progress in the same direction. When epoch-making technology, such as the microprocessor, is incorporated into the product system the direction of the progress in architecture may be reversed from the module to the integral.

Progression through the cell cycle is driven by cyclin-dependent kinases (CDKs) whose activity is controlled by regulatory subunits called cyclins. The expression of cyclins is subject to numerous controls at multiple levels, not least at the level of transcription. As a first step to unravel the mechanisms that regulate expression of B-cyclins in plants, we undertook the identification of the required promoter elements of the Arath;CycB1;1 gene. A detailed analysis of different promoter fragments consisted in analysing their ability to mediate cell cycle-dependent transcriptional oscillations of the gus reporter gene in transformed BY-2 cell lines. We showed that different promoter regions took part in transcriptional activation. Furthermore, 202 bp upstream of the ATG were sufficient to induce M-phase-specific expression. This region contains an 18 bp sequence including a Myb-binding core (AACGG) which is able to activate reporter gene without leading to M-phase-specific expression. Electrophoretic mobility shift assays showed that this 18 bp sequence specifically binds protein complexes from Arabidopsis cell suspension enriched either in G1 or G2 phase. Furthermore, the Myb core, AACGG, was characterized as necessary for the binding of proteins. DNA affinity purification of the complexes bound to the 18 bp sequence allowed the isolation of three different complexes and two proteins from these complexes were identified by mass spectrometry analyses. A new putative Myb transcription factor and a hypothetical protein, HYP containing with a leucine zipper and Myctype dimerization domains were identified. When over-expressed in plants, HYP factor is able to trans-activate the expression of gus reporter gene downstream from the −202 promoter fragment as well as the endogenous CycB1;1 gene.

A novel approach to cognitive automation of assembly processes is introduced. An experimental assembly cell with two robots has been designed to proof the concept. The cell’s numerical control – termed a cognitive control unit (CCU) – is able to simulate human information processing at a rule-based level of cognitive control on the basis of the SOAR cognitive architecture. Thus the CCU can plan assembly processes autonomously and can react to changes in assembly processes due to increasing number of products that have to be assembled in a large variety in production space as well as changing or uncertain conditions. To develop a “Humanoid-Mode” for automated assembly systems similar to the H-metaphor for automated vehicles human assembly strategies where identified in empirical investigations and formulated as production rules. When the CCU is enriched with these production rules underlying human heuristics, a significant increase of the predictability of a robot when assembling products can be achieved.

In this paper, two methods are used to recognize the roughing features in an intermediate workpiece, which is obtained by gluing the finishing features onto the original component. The first method is based on the physical states of equilibrium and hence is referred to as the equilibrium method. This method recognizes features originating from convex inner loops. The second method, referred to as the concavity method, uses the concavity of vertices, edges and faces to detect features and the interactions between them. The features are represented as volumes and are classified according to a feature taxonomy. In this taxonomy, a new class of features, i.e. free features, is included. Examples of such features are blend, edge and vertex volumes. Edge and vertex volumes are combined with face volumes to form face machining features. The methodology is illustrated by recognizing the features in two industrial components. ᭧

Private landowners are often de facto stewards of biodiversity and ecosystem services. In California's Sierra Nevada foothills, ranchers frequently present the only defense against biological invasions in private rangelands. Although ranchers' land management goals (e.g., the desire to control invasive species) can be consistent with ecosystem protection, practical constraints often limit their success. Considerable research on the invasive weed, yellow starthistle (Centaurea solstitialis L.), has produced numerous control strategies. Nevertheless, the range of this noxious weed continues to increase. We used surveys and interviews to document the weed control efforts of 202 ranchers and to identify practical limitations to their efficacy. Overall, 86% of ranchers who had experienced yellow starthistle infestation had attempted control, using one or more of 19 methods. Early response reduced negative effects from yellow starthistle. Control methods learned from agricultural advisors were reported more effective than those learned elsewhere. Limitations to yellow starthistle control in our study population resulted from incomplete information regarding control methods, complexity of weed control in heterogeneous landscapes, inconsistent application of methods, and lack of long-term planning for weed control. Such hindrances make it difficult for landowners to implement control methods promoted by researchers. This gap between science and practice contributes to the continued increase of yellow starthistle within the study region. To shrink this gap, researchers and agricultural advisors can incorporate environmental heterogeneity into applied agricultural research, use land stewards' knowledge and experience, and increase public education.

In this paper, a data acquisition system that simultaneously allows the recording of cutting forces and cutting tool position (coordinates X, Y and Z) is presented. Thus, the geometry of the surface being machined and the values of the cutting forces generated during the surface milling can be correlated. In this manner, two usual problems in milling experimentation are solved. First, those derive from the continuous changes in the feed rate value due to the special look ahead functions (being on-line applied by the numerical control in all high-speed milling centres), which affects the correlation between part geometry and forces. Second, those originate by the presence of unexpected stocks coming from previous semi-finishing operations, which changes the value of cutting forces respect to those calculated taking into account the theoretical tool engagement into the part. The objective of this work is the development of a diagnostics tool for allowing the detection of potential milling problems by researchers, making more profitable the performance of machining test on real complex parts. This tool can be used in the optimization of the milling of test-parts, machining real geometries that incorporate problems different from those observed in the linear tests at constant linear feeds (in end-milling conditions). The final goal of the system is the generation of cutting forces maps as a function of the geometry of real workpieces, which is an advance respect the usual forces recording in function of time or tool rotation typical of linear machining tests. In order to do that, the system incorporates a dynamometric plate for the measurement of the three components of the cutting force, as well as an acquisition card connected to the analog output of the position control loops. After machining, the file containing position and force data is postprocessed and chromatic and vector maps are generated. The force analysis utility has been applied to three cases, in order to assess its feasibility in machining research projects. The first example shows a reduction of the number of tests and therefore machining time (even by 18 times) in the validation of a mechanistic cutting force model. Second example is focused on the detection of unexpected tool engagement conditions in complex parts. And the last one addresses to the milling of thin walls, for investigation of static and dynamic milling problems.

The article discussed the sensitivity of a certain problems of linear control theory, including pole assignment, full state feedback linear quadratic control and H∞ control. It was demonstrated that the mathematical formulation and the splitting of the problem into subproblems are essential factors in the conditioning of these problems. It was also shown that standard approaches implemented in numerical toolboxes, which present widely accepted approaches in numerical control, may face problems due to ill conditioning. Some of these problems can be avoided by reformulating the problem, but several open problems remain. To assess the accuracy of calculations and to trust numerical results, such condition and accuracy estimates should accompany computational procedures and must be included in the corresponding computer codes. Users must be aware of possible difficulties accompanying the computational process and know how to avoid them. The issues should also become an essential part of the curriculum for scientist and engineers in learning how to use and develop modern computational software.

To accomplish timing recoverylsynthesis in highspeed communication systems, a 24-b numerically controlled oscillator (NCO) IC using a circuit design technique called true single-phase clock (TSPC) pipelined CMOS has been fabricated in a standard 1.2-pm CMOS process. The device achieves a maximum tested input clock rate of 700 MHz, which results in an output frequency tuning range from dc up to 350 MHz with a 41.7-Hz tuning resolution and a peak-to-peak phase jitter of 1.4 ns. The 1.7 x 1.7-mm2 IC dissipates 850 mW with a single 5-V supply, which is substantially lower than similar ECL and GaAs devices.

Tension control of an aluminum strip in a strip processing line is the focus of this paper. A continuous strip processing line is truly a large-scale complex interconnected dynamic system with numerous control zones to transport the strip while processing it. In this paper, two aspects affecting the tension behavior of the strip in the entire processing line have been studied. First, a model that accurately represents the dynamics of the strip in accumulator spans is derived from the first principles. Second, an estimated decoupled state feedback controller is designed for the linearized dynamics of controlled spans. The state estimates are obtained using a Luenberger observer. Convergence of the state and estimation errors is shown. Some remarks on detection of actuator faults using a linear observer for interconnected systems are also given.

Tree root systems, which play a major role in below-ground carbon (C) dynamics, are one of the key research areas for estimating long-term C cycling in forest ecosystems. In addition to regulating major C fluxes in the present conditions, tree root systems potentially hold numerous controls over forest responses to a changing environment. The predominant contribution of tree root systems to below-ground C dynamics has been given little emphasis in forest models. We developed the TRAP model, i.e. Tree Root Allocation of Photosynthates, to predict the partitioning of photosynthates between the fine and coarse root systems of trees among series of soil layers. TRAP simulates root system responses to soil stress factors affecting root growth. Validation data were obtained from two Belgian experimental forests, one mostly composed of beech (Fagus sylvatica L.) and the other of Scots pine (Pinus sylvestris L.). TRAP accurately predicted (R = 0.88) night-time CO 2 fluxes from the beech forest for a 3-year period. Total fine root biomass of beech was predicted within 6% of measured values, and simulation of fine root distribution among soil layers was accurate. Our simulations suggest that increased soil resistance to root penetration due to reduced soil water content during summer droughts is the major mechanism affecting the distribution of root growth among soil layers of temperate Belgian forests. The simulated annual rate of C input to soil litter due to the fine root turnover of the Scots pine was 207 g C m −2 yr −1 . The TRAP model predicts that fine root turnover is the single most important source of C to the temperate forest soils of Belgium.

This report describes an interpreter which reads numerical control code and produces calls to a set of canonical machining functions. The interpreter is a software system written in the C++ programming language. The output of the interpreter may be used to drive 3-axis to 6-axis machining centers. Input to the interpreter is RS274 code in the dialect defined by the Next Generation Controller (NGC) project, with modifications. The interpreter may be compiled as a stand-alone computer program or may be integrated with the NIST Enhanced Machine Controller (EMC) control system. Input can come from a file or from a user typing on a computer keyboard. Output commands can either be printed for future use or be executed directly on a machining center. The report includes a full description of the RS274/NGC input language and the canonical machining functions called by the interpreter. It is a complete users manual.

The problem of tandem production lines composed of multiple unreliable workstations producing a single part type with holding (inventory and storage space) and shortage costs is considered. Given the numerous control mechanisms introduced in recent years, it is a difficult task to evaluate which mechanism is best suited for a specific application. Using simulation, design of experiments and response surface methodology, various homogenous lines controlled by Kanban, CONWIP and the hybrid Kanban/CONWIP control mechanisms are optimized and then compared. It is observed that the hybrid mechanism always outperforms CONWIP and Kanban when storage space and inventory costs are considered explicitly. However, hybrid is equivalent to CONWIP when storage space costs are not considered explicitly but rather aggregated with the inventory costs in the holding costs as usually found in the literature. Furthermore, with the increase of storage space cost and the number of workstations, Kanban outperforms CONWIP.

tions which perform specific operations such as calibrate on, calibrate off, pulse, etc. The data readout format and timing are handled in detail by the hardware but controlled by the software, allowing such options as faster readouts for accelerator testing and easy construction of special test signal patterns for checkout and troubleshooting. ACKNOWLEDGMENT Throughout the design and construction of the MEH instrument, virtually the entire staff of the Laboratory for Astrophysics and Space Research has made some contribution. However, the authors would like to mention the following individuals in particular.

CNC feature-based programming with STEP-NC standard extends the collaborative model of manufacturing data exchange all along the numerical data chain. This paper considers the mutations related to this approach from the manufacturing system level to the industrial enterprise as a whole. The eXtended Manufacturing Integrated System concept is introduced to fill in the gap of the current manufacturing data exchange bottleneck. It is composed of eXtended CAD and eXtended CNC systems to link the CAD model to the real machined part through the Manufacturing Information Pipeline. The contributions associated with these concepts are demonstrated through a validation platform implemented on industrial CNC manufacturing equipments.

With an increase in the diameters of aluminum alloy thin-walled tubes (AATTs) and a decrease in their bending radii, wrinkling characteristics and its prediction under multi-die constraints have become a key problem urgently to be solved for improving the forming quality in numerical control (NC) bending of AATTs with large diameters. Thus in this paper, considering the characteristics of the bending processes, based on the ABAQUS software environment, a 3D elastic-plastic finite element model and a wrinkling energy prediction model under multi-die constraints are established and their reliabilities are validated, respectively, in which, the appropriate choosing of forming parameters is achieved to guarantee no excessive thinning and flattening in the processes even if wrinkling borders on occurring. By combining the two models, variation relationships of the maximum wrinkling factor with different compressed deformation zones and forming ratios, and effects of clearances and friction between different dies and tubes on the maximum wrinkling factor are obtained, and then an investigation into the wrinkling characteristics is carried out for the processes. It is found that the larger the diameters of AATTs, the larger the wrinkling sensitive zones (WSZs), and there is a larger possibility of wrinkling in the bending segments of WSZs than in the straight ones; the larger the effects of clearances and friction between different dies and tubes on wrinkling.

There are currently no analytical methods available which determine the exact arc length for NURBS curves and for this reason, a smooth feedrate profile with desired trajectory cannot be achieved. Numerical methods used to calculate the arc length are time-consuming processes which make generating a feedrate profile with desired accelerations difficult in real-time. This paper introduces a look-ahead trajectory generation method which determines the deceleration stage according to the fast estimated arc length and the reverse interpolation of each curve at every sampling time. This results in a feedrate trajectory generation with jerk-limited acceleration profiles for the NURBS curves. The feedrate profile is adjusted dynamically according to the geometrical path constraint determined by chord error for the curved path. A NURBS curve by two different kinematics conditions was used as a means to test the feasibility of the developed interpolation scheme and command generator.

This work focuses on developing an application based on the information contained in the numerical control (NC) kernel for surface roughness monitoring of the part in process. A human-machine interface (HMI) was developed in order to facilitate the interaction between the operator and the NC kernel with a graphical user interface working in the computer numerically controlled (CNC) screen. Experimentation was carried out in order to obtain the data to be modeled with artificial neural networks for surface roughness average parameter (Ra) predictions. Finally, a compact solution was implemented through global user data (GUD). Data from the HMI and from the kernel are collected in the GUD and analyzed with the artificial neural network. The application provides the surface roughness average parameter of the part in process and gives optimized parameters to the operator. Verification tests were carried out, showing accurate results. The use of the application developed in this research ensures the surface roughness Ra requirement, improves cutting parameters, reduces manual finishing operations and unacceptable parts at the end of the manufacturing process, and provides a solution implemented in the machine tool CNC screen without the need of any other external sensors.

Abstract An algorithm for generating tool positions for three-axis mill cutter paths on parametric surfaces is presented. The novelty of this algorithm is in its use of a surface subdivision technique as an alternative to the traditional APT-style iterative approaches ...

The present study addresses the modal synthesis of dynamic responses or receptances, which can be considered as a major issue in vibratory or acoustic design. A new method termed ''method of orthocomplement'' offers to increase the accuracy of modal superposition. Two apparently independent domains are considered: first, the numerical control of round-off errors in finite-dimensional models; second, the regularization of modal boundary discontinuities in infinitedimensional formulations. Concerning the finite-dimensional systems, using the proposed method in conjunction with pseudo-inversion theorems, proves that ''inertia relief corrections'' remedy modal truncation problems in singular floating systems, just as static corrections do for simply supported systems. The proof is based on hitherto unpublished expressions of inertial contributions in terms of orthogonal projectors. It is worth noting that such expressions present by themselves some technical interest. Modal formulae being delivered in closed form, a thorough analysis of errors becomes possible. Special ''spectrograms'' are introduced to appraise the convergence of ordinary or modified modal sums. When applied to infinite-dimensional modal boundary discontinuities, the method of orthocomplement eliminates the Gibbs oscillations that affect the ordinary spectral sums, and produces the same corrected formulae as it did for finite-dimensional examples. Effective solutions for the computation of vibratory or acoustic boundary receptances, are developed in that way. The paper once again illustrates how orthogonal projectors can contribute to the determination of static corrections. Future applications to coupling problems, model reduction and modal synthesis are briefly presented at the end of the text. r

The basis of the integration of activities related to the product life cycle is, mainly, the creation of a unique and coherent information model along all the stages in the cycle. Up to date, dimensional inspection activities have not been deeply analysed, possibly due to the fact that, their work influences are smaller than others, such us numerical analysis, materials or numerical control. However, the integration of dimensional inspection is very important for several reasons: the need of specifying the design and planning of the inspection process from the conceptual part design; the increase of use of high speed coordinate measuring machine (CMM) in the production lines; and finally, for the interest of a feedback between data inspection and manufacturing processes. This paper is a detailed proposal of an information model for inspection based on operations for CMM, which represents a consistent structure of the necessary data in an integrated product setting. 

A computer-controllable variable optical attenuator has been developed and tested that has a wide dynamic range, wide spectral range, and is suitable for applications with high peak and average power laser sources. The device is based on Fresnel transmission through two pairs of wedged plates. A 35-dB dynamic range, an insertion loss of 1%, a precision of better than 1% and beam offset and deflection of <0.5 mm and 0.5 mrad, respectively, are demonstrated. The ideal optical variable attenuator should provide wide dynamic range, wide spectral range, resettability, and high accuracy, yet exhibit a simple optical and mechanical design. We added the additional requirements that the optical variable attenuator operate with high peak and average power inputs produced by Qswitched laser sources and not significantly alter the beam profile, position, or direction. With these constraints in mind, we reviewed possible methods of applying the three fundamental interactions that can be used to attenuate optical radiation: absorption; Fresnel reflection at a surface; and interference. Attenuation by absorption and interference were eliminated as not being consistent with the requirements for high peak and average power and wide spectral range. Fresnel reflection is the basis for many forms of attenuators including those based on birefringent crystals and polarization-dependent total internal reflection.l We chose to avoid the use of crystals because of limited spectral range and optical quality. Instead we concentrated on Fresnel reflection near the critical angle in a homogeneous dielectric medium. The variable gap spacing total internal reflection attenuator 2 is spectrally sensitive and requires tight fabrication tolerances. On the other hand, a variable incident angle wedged-plate attenuator utilizing Fresnel

A novel concept to cognitive automation of robotic assembly processes is introduced. An experimental assembly cell with two robots was designed to verify and validate the concept. The cell’s numerical control—termed a cognitive control unit (CCU)—is able to simulate human information processing at a rule-based level of cognitive control. To enable the CCU to work on a large range of assembly tasks expected of a human operator, the cognitive architecture SOAR is used. On the basis of a self-developed set of production rules within the knowledge base, the CCU can plan assembly processes autonomously and react to ad-hoc changes in assembly sequences effectively. Extensive simulation studies have shown that cognitive automation based on SOAR is especially suitable for random parts supply, which reduces planning effort in logistics. Conversely, a disproportional increase in processing time was observed for deterministic parts supply, especially for assemblies containing large numbers of identical parts.

Servomotors are widely used in computerized numerically controlled (CNC) machines, hence motion control is a major topic covered in undergraduate/graduate engineering courses. Despite the fact that several syllabi include the motion dynamics topic in their courses, there are neither suitable tools available for designing and simulating multi-axis motion control nor an efficient link between theory and practice. This paper proposes an educational, open-source tool for teaching motion dynamics in multi-axis servomotor control. The tool allows students to generate multi-axis motion and export these movements for their application to a CNC machine. A simulation module is embedded for evaluating the controller performance. The proposed educational tool allows the use of the inductive pedagogic method to support student learning. Eleven lab practicals are described to show how the proposed tool can be utilized for the systematic teaching of motion dynamics.

A single beam, multiple target (SBMT) deposition system which features a rotating target holder with either elemental or simple compound targets has been developed for the production of layered thin film structures and multicomponent oxide, silicide or other compound thin films. We are employing the SBMT ion beam sputtering system for the deposition of high temperature superconducting, electro-optic and ferroelectric thin films and multilayered structures. The beam-target-substrate geometry and ion beam characteristics are designed to minimize scattering of the ion beam from the target (which results in resputtering of. and inert gas incorporation into the film) while maintaining high deposition rates. The amount of energy which is deposited into the film may be controlled by means of a secondary reactive or inert ion beam impacting on the growing film. This secondary beam may provide enough energy to promote activated processes, such as the in-situ formation of oriented crystal structures of high temperature superconducting materials. All parameters necessary to control the film properties are under computer control. A deposition cycle, defined as a number of sequential steps, may be easily modified or added to previously existing deposition cycles, thereby permitting the creation of complicated deposition procedures suitable for the production of films with highly reproducible properties for research purposes, and the in-situ fabrication of complex devices for technological applications. Examples are given of the capabilities of the technique as they apply to the production of high T, superconducting devices.

Three-dimensional models are being increasingly used as prototypes in various areas of manufacturing, research and education. They are especially useful in the evaluation of elements typical of mechanical design, but are also important in architecture, medicine, arts, etc. These models can be developed using various methods, such as mass modeling, surface planification, and rapid prototyping (RP) with removal or addition of material based on a CAD/CAM platform. This latter approach was employed in the present paper. Complex solids are formed through the association of elementary solids such as spheres, prisms, cylinders, torus, etc., and then rapid prototyping is applied involving a slicing process. A virtual model based on a CAD platform allows the determination of paths for each sliced level. These are translated into numerical control codes, and fed to a milling process of a blank, allowing the manufacturing of a 3D model.

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 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.

A computerized optical system has been constructed for the design and generation of space-variant holographic filters. Special considerations of the computerized design of the space-variant filters and the operation and performances of the system are addressed and discussed. The system was experimentally employed to generate holographic optical filters for the optical implementations of Hough transform, coordinate transformations, etc. Experimental performances of the generated space-variant filters are evaluated and discussed. P. Ambs and J. Gresser are with

The escalation in processor technologies and the corresponding reduction in costs have enabled alternative FMS control architectures to be developed without the restrictions of "fixed machine controller boundaries." These new architectures can be based upon the use of intelligent servo axes, which are desccribed in this article, as flexible numerical control (FNC). In current parlance, the FNC is a "part movement holon" within a manufacturing cell. The control architectures that can be derived from the FNC concept ate referred to as hybrid architectures and share the emerging attributes of holonics. This article details the problems that arise in the scheduling and control of FM!% in the light of hybrid control architectures. A number of traditional scheduling approaches have been devised to cope with the scheduling of parts to discrete machines, but the problem here is to ascribe the processing (machining) of part features to axis groups. This article documents how two research programs, undertaken at the CIM Centre at Swinbume University of Technology in Hawthorn, Victoria, Australia, have endeavored to address the problem of hybrid architectures and their associated scheduling.

Design of a stable controller and observer for web tension regulation in an accumulator, in web processing lines, is considered in this paper. A simplified average dynamic model that includes accumulator carriage dynamics, average web tension dynamics in accumulator web spans, and the process and exit side driven roller dynamics is considered in the study. A feedback controller together with an observer for average web tension is proposed. It is shown that the proposed feedback controller and observer results in a stable closed-loop system. Simulation results on an industrial continuous web processing line are given and discussed for the proposed controller/observer and compared with a currently used industrial controller. Applications of this research can be found in web process lines where accumulators are used to store/release material to ensure continuous operation.

The Sequenced Convex Subtraction (SCS) algorithm is a hardware based multi-pass image-space algorithm for general purpose Constructive Solid Geometry (CSG) Rendering. Convex objects combined by volu- metric intersection, difference and union are rendered in real-time without b-rep pre-processing. OpenGL stencil and depth testing is used to determine the visible surface for each pixel on the screen. This paper introduces a

commissioning are described. magnets. The bench and its performance and precision achieved during its an important issue during production measurements of large series of automated, computer-controlled operation requiring a minimum of staff, emphasis has been put on the user-friendliness of the bench and its placed outside the magnetic field without space restrictions. Particular motor, an angular encoder and a level meter, all standard components very high rotational stiffness and which is controlled from its far end by a mounted at one end of a 12.5 m long shaft which is specially designed for at room temperature. This coil, together with Hall and NMR detectors is installed inside the magnet cold bore, thus allowing the use of rotating coils integrals. The measurements will be carried out along a warm bore content of higher harmonic field components, field direction and field The magnetic measurement of more than 1300 LHC dipoles comprises the Ahstrggt ].

Since the introduction of NC technology for manufacturing systems nearly 40years ago, various approaches to its utilization have been applied. The differing paths of NC implementation and development in the USA and FRG are examined, and the selection of technological options is identified as the central factor in past technological development. However, this selection, and consequently the developmental paths, are dependent upon social, historical and market-related factors as well as technological considerations. The historical existence of a number of primary and secondary developmental paths in the US and Europe, differing in application and flexibility, can be attributed to technological choices made against a background of such varying influences.