Model Of Table Research Articles

Mathematical Model of a CNC Rotary Table Driven by a Worm Gear

This paper proposes a mathematical model of a CNC rotary table driven by a worm gear. The CNC rotary tables are generally utilized as rotary axes of 5-axis machining centres. In this study, a mathematical model which can simulate dynamic behaviours of rotary table is proposed. The model consists of inertia of motor, spur and worm gears, and table. Axial displacement of the worm is also considered into the model. Various motions are measured and simulated to confirm effectiveness of the model. As the results show, the proposed model can simulate step response, rotational fluctuations, and influence of unbalanced mass.

Numerical Model of Seepage Around Planned Water Reservoir in Kamieniec Ząbkowicki

Abstract With a view to protecting areas lying near the Nysa Kłodzka river and in order to reduce flood wave in Wrocław Waterway System, construction of a water reservoir near Kamieniec Ząbkowicki is being planned. After analysing the hydrology and hydraulics of the river Nysa Kłodzka and the function of reservoirs in Kamieniec Ząbkowicki cascade, a numerical seepage model, based on finite element method (FEM) and taking into account bedrock geology, drainage design and dam sealing, has been proposed. Boussinesq’s mathematical model was used to calculate unconfined groundwater table and vector field of seepage velocity. Building a numerical terrain model and visualisation of the water table in GIS tools enabled presenting calculation results in 3-D space.

Dynamic model of NC rotary table in angle measurements with time series

In this study, a dynamic model of absolute time grating, a novel kind of displacement sensor, is established in order to apply the absolute time grating sensor, instead of the optical grating sensor, as an angle encoder to the full closed-loop numerical control (NC) rotary table. Time series analysis is employed in the dynamic model, and given the series of past measured angles, therefore, the dynamic model can be used to forecast the next future measured angle. As a result, the original absolute signal sampled in equal time intervals of an absolute time grating sensor can be transformed into continuous incremental pulses for a full closed-loop NC rotary table. When the current angle is deduced, the latest measured angle of the time series is interpolated as standard quantity to compensate for the last forecast error. In this way, the forecast error can be corrected between neighboring sampling periods, and cumulative errors can be eliminated. The forecasting accuracy of incremental pulses for the time grating sensor can reach ±3″ which validates the dynamic model in improving the performance of the time grating displacement sensor in dynamic measurement.

ウォームギヤと平歯車を用いた回転軸駆動機構の数学モデル

This paper proposes a mathematical model of CNC rotary table driven by worm and spur gears. Proposed mathematical model has 4 degrees of freedom; rotational angle of motor, rotational angle of worm shaft, axial displacement of worm shaft, and rotational angle of table. Backlashes of spur and worm gear are also introduced into the model. Mass and inertias are calculated from designed drawings, and Coulomb's and viscous frictions are identified by matching motor torque curves under sine wave motions. Frequency response of the driving mechanism is also measured to identify axial and rotational stiffness. In order to confirm the effectiveness of proposed model, an experimental set-up consists of the rotary table and personal computer with a DSP board is modeled. Step response, rotational fluctuation, and influence of unbalanced mass are measured and simulated. As the results, it is confirmed that the proposed model can well simulate actual behaviors.

Study on the rainfall and aftershock threshold for debris flow of post-earthquake

Due to the special condition of provenance and disaster environment after "5 center dot 12" Earthquake, the probability and conditions of the occurrence of gully debris flow change greatly after the event, which make it difficult to prevent disaster effectively. In this study the hydrological model of ground water table in loose sediment is established. According to infinite slope theory, the safety factor of deposits is defined as the ratio of resistance force to driving force. The starting condition of post-earthquake gully debris flow is clearly studied by analyzing the effects of rainfall intensity, seismic strength, slope gradient and mechanical properties on the balance of accumulation body. Then the formulas of rainfall and aftershock threshold for starting of gully debris flow are proposed, and an example is given to illustrate the effect of rainfall, aftershocks and their coupling action on a debris flow. The result shows the critical rainfall intensity decreases as the lateral seismic acceleration and channel gradient increases, while the critical intensity linearly increases as the friction angle increases.

Robust and precision control for a directly-driven XY table

To provide faster, more repeatable, and stronger microelectronics bonding technology, this article presents the design and implementation of a robust and precision controller for a high-speed linear voice-coil motor, direct-drive, XY positioning table. Moreover, the dynamic design methodology of the control system for the positioning table is proposed based on electromechanical co-simulation. Using the finite-element method and dynamic analysis, the rigid–flexible coupled mechanical model of the XY table is established. With the aid of the system identification approach, the open-loop model of the control system for the X-axis table is obtained. On this basis, the proportion integration differentiation controller with incomplete derivation and the sliding mode controller (SMC) with the exponential reaching law are designed to control the X-axis table. The performances of the controllers are investigated using electromechanical co-simulations and experimental tests, and the results show that the motion overshoot and settling time are reduced using the SMC with an exponential reaching law. The SMC with the exponential reaching law also shows strong robustness against external disturbances. The experiment and co-simulation results are in good agreement, which confirms the validity and feasibility of the dynamic design methodology for a high-speed and high-accuracy positioning table based on electromechanical co-simulation.

Modeling of a Direct-Drive Table for Automatic Wire Bonder

This paper presents the modeling of a high-accuracy and high-acceleration table used for automatic wire bonder. The table is directly driven by linear voice coil motor (LVCM), and thus the mass and inertia of the motion system are significantly reduced by using a novel flexible decoupling mechanism based on flexure hinges and preloaded spring. The decoupling principle of the mechanism was introduced, and the electromechanical coupled mathematical model of Y-axis table was evaluated according to the dynamics of a mechanical mass-spring-damp system and LVCM. The model of Y-axis table was then identified with the aid of a Laser Interferometer and data acquirement card. Model validation experiments were carried out, and the results show that the model has sufficient accuracy when used to predict the performances of the real-world system under new conditions, and meanwhile it also can provide important information for the control of Y-axis table.

Phase locking scheme based on look-up-table-assisted sliding discrete Fourier transform for low-frequency power and acoustic signals

The frequency tracking performance of sliding discrete Fourier transform (SDFT)-based phase locking (PLL) scheme has been improved by supplementing a cosine look-up table (cLUT) loop. Since the SDFT algorithm is marginally stable, to avoid instability, a damping factor is introduced, which causes the steady-state error in the PLL behaviour. The addition of cLUT indirectly strengthens cosine component of SDFT output and eliminates the effect of damping factor. Consequently, the numerically controlled oscillator (NCO) yields accurate sampling frequency, and it could be utilised to generate unit sine and cosine reference signals, synchronous with the periodic input signal in power system applications. A mathematical model of the look-up table (LUT) assisted SDFT-based PLL has been developed to analyse the transient and steady-state behaviour and it substantiates the improvement in steady-state performance. The PLL exhibits second order under damped response resulting in faster acquisition and small reduction in pull-in range with zero steady-state error. The improvement in performance of the LUT-assisted SDFT PLL is investigated by simulation and experimental studies.

Temporal variability of the selected flood parameters in the Biebrza River valley

Temporal variability of the selected flood parameters in the Biebrza River valley The paper presents the application of the hydrodynamic one-dimensional model of river flow based on St Venant equations for calculation of annual floods characteristics in the Lower Biebrza River Basin situated in the Northeast of Poland. This model was combined with the Digital Elevation Model (DEM) for determining of area of flooding, its mean depth and flood volume. The model was calibrated using measurements of flood extent and verified comparing calculated flood extent to satellite images. The water level values calculated with the numerical model of flood-flow for cross-sections were next used to determine the digital model of the floodwater table in the valley. Then, inundation extent maps and water depth maps were calculated for whole area of the valley by overlaying the DEM and water table layers. This procedure, flood simulations with the hydrodynamic model and GIS analysis for determinations of inundation extent, was repeated for each day of the analyzed period of 1966-2000. A set of each year maximum calculated areas of flooding with related mean water depths and flood volumes was created and it was submitted to the trend analysis in order to determine possible change tendencies. Statistical analysis of three above described time series of annual flood characteristics was conducted with the use of moving average technique and linear regression method. Moving averages were calculate in two variants: with time step of 5 years and of 10 years. Next, linear trends were calculated by linear regression method. The results indicate that the developed hydrodynamic model of river flow combined with the DEM was useful for the calculation of annual maximum floods in the Lower Biebrza Valley and their parameters. Analysis of calculated flood parameters variability within the analyzed time period of 1961-2000 show decreasing trends for investigated area. This means that results of climate changes are perceptible in investigated area and they form serious danger to riparian wetlands.

Isocentric rotational performance of the Elekta Precise Table studied using a USB-microscope

The isocentric three-dimensional performance of the Elekta Precise Table was investigated. A pointer was attached to the radiation head of the accelerator and positioned at the geometric rotational axis of the head. A USB-microscope was mounted on the treatment tabletop to measure the table position relative to the pointer tip. The table performance was mapped in terms of USB-microscope images of the pointer tip at different table angles and load configurations. The USB-microscope was used as a detector to measure the pointer tip positions with a resolution down to 0.01 mm. A new elastic model of the treatment table was developed. This model describes the performance of the treatment table quite well except from some deviations due to backlash effects. Geometric and elastic features are described through six parameters. These parameters are calculated using the linear least squares fitting technique. A new method to ensure optimal positioning of the table relative to the accelerator is presented. This method cannot eliminate systematic errors completely. To eliminate systematic errors we suggest that geometric and elastic models of the table and accelerator gantry arm are incorporated in the dose planning system.

The Dynamic Finite Element Analysis of Table of VM1000 CNC Machining Center

The table of VM1000 CNC machining center is a box-frame structure with ribbed plate. The three-dimensional model of table based on Pro/E was built, the modal analysis and related experiments of table was completed by software of ANSYS, The dynamic performance parameter of the table is obtained, and the analysis results indicate that the design of table is available; it can be applied in practice.

テーブル間干渉を有するシステムのモデル化とモデルベースフィードフォワード補償

Force interference between multiple positioning devices with arbitrary motion profiles may deteriorate positioning performance. In this study, feedforward compensation based on an interference model of table drive systems was applied to suppress the effects of interference on positioning. The interference model was experimentally identified on the basis of frequency responses by a sinusoidal sweep method.The proposed feedforward compensation for the interference has been verified by using a prototype that consists of two table systems on a common machine stand.

Infinite factorization of multiple non-parametric views

Combined analysis of multiple data sources has increasing application interest, in particular for distinguishing shared and source-specific aspects. We extend this rationale to the generative and non-parametric clustering setting by introducing a novel non-parametric hierarchical mixture model. The lower level of the model describes each source with a flexible non-parametric mixture, and the top level combines these to describe commonalities of the sources. The lower-level clusters arise from hierarchical Dirichlet Processes, inducing an infinite-dimensional contingency table between the sources. The commonalities between the sources are modeled by an infinite component model of the contingency table, interpretable as non-negative factorization of infinite matrices, or as a prior for infinite contingency tables. With Gaussian mixture components plugged in for continuous measurements, the model is applied to two views of genes, mRNA expression and abundance of the produced proteins, to expose groups of genes that are co-regulated in either or both of the views. We discover complex relationships between the marginals (that are multimodal in both marginals) that would remain undetected by simpler models. Cluster analysis of co-expression is a standard method of screening for co-regulation, and the two-view analysis extends the approach to distinguishing between pre- and post-translational regulation.

Feed-forward Control of a MIMO System for a Large-size and Lightweight Isolation Table

In this paper we propose a design method for a three-dimensional active isolation system with a low-stiffness isolation table assumed to be a large-size, lightweight isolation system. The lightweight, large-size isolation tables have been designed to be flexible. Owing to this, multi-modal vibrations appeared on the isolation table in the lower-frequency region. Therefore, a control system for considering multi-modal vibrations should be developed. We constructed a five-degree-of-freedom lumped model of the isolation table using a reduced-order physical-modeling method that is effective for controlling multi-modal vibrations. In the controller design, the performance of vibration control is obtained using a feedback controller designed using the linear—quadratic (LQ) control theory. Moreover, a feed-forward controller for a multi-input multi-output system has been added in order to obtain a high-isolation performance. Thus, a two-degree-of-freedom controller combined with LQ feed-forward controllers is designed. The usefulness of the proposed modeling method and controller are confirmed through numerical simulations and experimental results.

Modeling sublimation of ice exposed by new impacts in the martian mid-latitudes

New impacts in the martian mid-latitudes have exposed near-surface ice. This ice is observed to slowly fade over timescales of months. In the present martian climate, exposed surface ice is unstable during summer months in the mid-latitudes and will sublimate. We model the sublimation of ice at five new impact sites and examine the implications of its persistence. Even with generally conservative assumptions, for most reasonable choices of parameters it is likely that over a millimeter of sublimation occurred in the period during which the ice was observed to fade. The persistence of visible ice through such sublimation suggests that the ice is relatively pure rather than pore-filling. Such ice could be analogous to the nearly pure ice observed by the Phoenix Lander in the “Dodo-Goldilocks” trench and suggests that the high ice contents reported by the Mars Odyssey Gamma Ray Spectrometer at high latitudes extend to the mid-latitudes. Our observations are consistent with a model of the martian ice table in which a layer with high volumetric ice content overlies pore-filling ice, although other structures are possible.

Mathematical model of rotary table in control problems

Automatic control of a precision rotary table is complex. At a positional precision of 3 ″ , elastic deformation and free play have a significant influence on table operation. Correct synthesis of the automatic control system for such a table calls for a mathematical model that takes account of the characteristics of the executive mechanism and the type of electric motor. Kinematically, the SK36-1202 table contains a worm transmission, which transmits motion from the synchronous electric motor (with permanent magnets on the rotor) to the face plate. The motor is connected to the worm shaft by a clutch. As an object of control, the table is nonlinear and nonsteady. It is characterized by frictional forces, which perturb the machining process; free play in the worm transmission; and the accumulated gear error. The free play permits thermal compensation in machine-tool operation and is at least 15 ″ . The accumulated error of the worm gear is 10 ″ ‐15 ″ . In developing a mathematical model of the table’s executive mechanism, we make the following assumptions [1]. 1. The executive mechanism is subject only to elastic forces.

Virtual Reality: Viewership and Ethnographic Film

This article deals with the numerous difficulties in locating accuracy in representation. It expands C.S. Peirce's notion of the phaneron as applied to production and reception to the question of viewing of ethnographic flims. It revisits Wilton Martinez's seminal work on interpretation and ethnographic spectatorship critically. Keyan Tomaselli's model of the Phaneroscopic Table, derived from C.S. Peirce, is applied to the viewing situation itself. This article uses the metaphor of “virtual reality” to discuss the nature of iconic representation in relation to the viewer context. It examines some approaches of a variety of film theorists and reception scholars who have conducted empirical studies on reception.

A Study on the Providing Model of Table of Contents for Monography

A Study on the Providing Model of Table of Contents for Monography

A14 5軸制御マシニングセンタ用回転テーブルの数学モデルの開発(OS-1 最新工作機械(3))

A14 5軸制御マシニングセンタ用回転テーブルの数学モデルの開発(OS-1 最新工作機械(3))

526 部分空間法と周波数領域最小二乗近似を用いた除振台の低次元システム同定

A system identification technique for a vibration isolation table by using subspace method (N4SID) and Frequency-Domain Least-Squares Approximation (FDLSA) is studied in this paper. The vibration isolation table is supported by four pneumatic actuators at corners of the table. A 3DOF mathematical model of the vibration isolation table is constructed. The regulator for the pneumatic actuator is driven by a stepping motor. A procedure to obtain the minimum-order-model is proposed, and the procedure can be fully automated. Effectiveness of proposed approach is examined by experiments.