Corresponding author; email: sahalu@ccse.kfupm.edu.sa 相似文献
• • The finite element method is used for qualitative comparison of different machine tool structure concepts during the conceptual and design stages. Only after completion of the prototype may the parameters of the prototype model be adjusted for the purpose of obtaining quantitative indicators.
• • Dynamics are analyzed by parameter identification of the oriented transfer function model. The dominant degree of freedom is naturally selected by experiment and not from hypotheses about the behavior of structures obtained from mathematical manipulations such as expansion of the model according to the finite element method. If necessary another machine tool structure may be modelled; in this way hypotheses are drawn about the stability of the reconstructed prototype.
Such a procedure has been applied and verified on the machine tool structure of a horizontal machining center. Results for static rigidity and dynamic stability have been obtained from the model and experiments performed on the prototype. The following techniques have been used:
• • finite element method for qualitative identification of static behavior,
• • self-excitation of the machine,
• • digital signal processing on the FFT basis,
• • smoothing of curves and digital filtration,
• • function fitting of the transfer function (modal analysis),
• • coefficient calculus and oriented transfer function,
• • stability assessment of the fitted model under different machining conditions, and
• • modelling of the regenerative machining effect by cutting.
Necessary tests have been done by instruments required for the use of the above techniques.
Such a combined static-dynamic criteria procedure for structuring a machine tool enables efficient follow-up of all results and facilitates necessary future expansion, the utilization of universal equipment, the combination of modelling and experiments, and the synthesis of simple models of the examined machine with behavior identical to the machine. The well-known machining system dynamic stability theories are applied to such models. 相似文献
The robot simulator described in this paper has the following special features:
• • When a robot motion is prescribed by the VAL-G language, the result can be seen on a CRT display in several patterns.
• • High-speed dynamic display which can almost keep up with real-time movements.
• • A shaded as well as wire-frame picture is used for the high-speed display entioned above.
• • Supported by the solid modeler, any robot and environment can be used with this system.
• • The preparation of a precise interference checker based on an analytical methods.
This paper is a report on the development of the robot simulator. 相似文献
The paper describes an Adaptive Control Optimization (ACO) system for turning operations. The system continuously chooses Optimal Cutting Data (OCD), taking into account both economical criteria and technical limitations.
The system operates at three different levels:
• • Advanced Process Monitoring
• • Adaptive Control Constraint (ACC)
• • Adaptive Control Optimization (ACO).
Two commercial monitoring systems perform process monitoring. In addition, five independent measurement systems have been developed.
A dedicated vision system has been installed in the lathe to measure the tool flank wear between cuts. The flank wear data are utilized to predict the tool life. Based upon these predictions economical optimum cutting data can be calculated at the ACO level.
To obtain in-process real-time control of the metal cutting process the cutting forces are measured during machining. The forces are measured with conventional piezoelectric force transducers which are located between the turret housing and the cross-slide. The measured force signals are processed by a dedicated microcontroller at the ACC level and cutting data adjustments are fed back to the machine control.
A vibration measurement system, which either can be connected to an accelerometer or use the dynamic force signal from the piezoelectric force transducer, is part of a vibration control module at the ACC level. An ultra-fast signal processor performs the signal analysis.
The remaining two measurement systems—a high frequency tool signal analysis system and a power spectra analysis system—are mentioned in the paper but not further discussed.
Finally, the paper deals with how the strategies at the three different levels will be combined, in order to form an AC system. The monitoring tasks will always reside in the background and be activated if any failure occurs. The ACO subsystem will act as a path-finder and suggest cutting data. The active control tasks will, however, be carried out at the ACC level. 相似文献
These LSI circuits and system have several functions
• • The new Parcor LSI circuit has the circuits needed by the Parcor synthesis algorithm. It has a 64 kbit speech data ROM, output low pass filter and preamplifier. Using only this LSI circuit, 30 s to 60 s of speech can be synthesized.
• • The new ADM LSI circuit has encoding and decoding circuits, a 64 kbit speech data ROM and RAM control circuit. The record and synthesis system can be easily constructed with this LSI circuit and RAM.
• • The recording watch system consists of the watch LSI circuit with the ADM system and the analogue LSI circuit.
In the Parcor system, various high quality and low data-rate speech outputs are obtainable. The ADM system is applied for recording and synthesizing. By applying these systems to meet market needs, it is possible to achieve good cost performance in a simple system. 相似文献
• • Migration of the files to a DBMS
• • Extend the file system to support DBMS-like features
Both migration and extension of the file system are costly solutions and actually depend on existing capabilities of the components. Problems may occur when the federated schema becomes too large. The schema might be split up into smaller federated schemes (loosely coupled FBDS). 相似文献
• - Many studies have not measured vibration, or have not measured it thoroughly enough.
• - Confounding variables such as posture have not been entirely controlled for, because well-matched control groups do not exist.
• - Health data have tended to be binary incidence data rather than continuous scale data, reducing the sensitivity of the studies.
The pilot study has produced procedures to overcome these difficulties. 相似文献
• Does increasing input size improve sequential efficiency and speedup?
• To what extent do high communications latencies reduce average parallelism and speedup?
• Does migrating running threads between processors improve average parallelism and speedup at all latencies?
• - One method that can be used to compare new surfaces. It uses a static device developed at the INRS and it is based on the evaluation of a coefficient of dynamic friction between a sample of a new oiled surface and an elastomer. This method is well-adapted to the needs of standardisation work;
• - Another method that can be used to evaluate slippage in the field where the surfaces are often worn and polluted with a specific product. It uses a portable device developed in Sweden and it is based on the continuous evaluation of a coefficient of dynamic friction over a variable distance between the surface to be tested and an elastomer.
These two methods which present well-correlated results are described in this publication, and their distinctly different uses will be underlined. 相似文献
The field of sociotechnical systems theory (STS) focuses on exactly these kinds of issues. Rather than subscribing to the usual view of technological determinism — that a complex human-machine system is designed solely with respect to optimization of technical criteria — the goal of STS is to jointly optimize both human and technological considerations in system design and operation. The spirit of STS has much in common with recent work in cognitive systems engineering that advocates the design of joint cognitive systems in which machines serve as flexible, context-sensitive resources for human problem solving. Furthermore, a focus on design teams necessitates the study of the relationship between group work and technology as studied in the field of computer-supported cooperative work (CSCW). This paper briefly reviews current research in sociotechnical systems theory, computer-supported cooperative work, and cognitive systems engineering and proposes a framework for integrating operational concerns into the concurrent engineering process. Relevance to industry
To be competitive, organizations need to effectively manage human and technological resources. A key issue is the nature of the information and technological infrastructure that both enables and supports ‘best practice’ across the enterprise. This paper describes such an approach in the context of the ‘operational enterprise’ and provides both a philosophical stance as well as specific examples of software support. 相似文献
1. • for curve tracing algorithms, where a truncated series is used to approximate the curve of intersection of two surfaces
2. • to define nth degree geometric continuity, for arbitrary
Author Keywords: power series; curve; surface; intersection problems; curve tracing; geometric continuity 相似文献
- • a visual sensor called Optical Sensor for the Control of Autonomous Robots (OSCAR) which delivers a retinal angular position signal. A new, miniature (10 g), piezo-based version of this visual sensor is presented here;
• an inertial sensor which delivers an angular head velocity signal.
We built a miniature (30 g), one degree of freedom oculomotor mechanism equipped with a micro-rate gyro and the new version of the OSCAR visual sensor. The gaze controller involves a feedback control system based on the retinal position error measurement and a feedforward control system based on the angular head velocity measurement. The feedforward control system triggers a high-speed “Vestibulo-ocular reflex” that efficiently and rapidly compensates for any rotational disturbances of the head. We show that a fast rotational step perturbation (3° in 40 ms) applied to the head is almost completely (90%) rejected within a very short time (70 ms). Sinusoidal head perturbations are also rapidly compensated for, thus keeping the gaze stabilized on its target (an edge) within a 10 times smaller angular range than the perturbing head rotations, which were applied here at frequencies of up to 6 Hz in an amplitude range of up to 6°. This high standard of performance in terms of head rotational disturbance rejection is comparable to that afforded by the human vestibulo-oculomotor system. 相似文献
The programming system used as an example in this article consists of
1. *NORSAM—finite element programming system
2. *DASA — pre- and postprocessors
3. *ELLIB—element library
Together they form a complete set of subroutines from datageneration through the necessary routines for matrix manipulation to presentation of results, including the multilevel superelement technique.
Reference to finite element programs applying the programming system concept, is given at the end of the article. Among others, programs for buckling, elasto-plastic analysis of 3-dimensional membranes and solids, nonlinear pipeline problems, acoustic field problems and transient heat conduction in solids are developed. The multilevel superelement technique has been applied in several of these application programs.
The concept of the programming system gives undoubtedly a large saving of time and resources and has proved to be more reliable than conventional methods when developing finite element programs. 相似文献
Next, the extended search technique of the design space is discussed, and an integrated example of a belt-conveyor design is presented, based on the proposed representation platform and the extended search technique. Finally, it is shown that the design of belt conveyors according to the proposed approach presents the following significant advantages:
- • • Due to the knowledge-representation scheme adopted, both qualitative and quantitative knowledge can be used within the same platform.
- • • Multiple solutions can be easily produced through user-defined design criteria. These solutions can be further modified and/or evaluated to produce more-specific designs.
- • • The required for user-input data is kept to a minimum. Due to the applied extended search method, semiautomatic design can be achieved. As a consequence, the design process is completed in less time than that required by the conventional methods.
Taking as an example the particular instance of the Electricité de France E.D.F.—3 power plant, the authors review the various functions which have to be ensured by the automatic control system. These are:
temperature, pressure, flow, radioactivity measurements processing with excess-value detection,
defect-signalling processing with chronological restitution of state changes, nuclear-fuel cartridge breakage detection
various problems, peculiar to nuclear plants, such as xenon concentration and reactivity computation, neutronic power optimization space flow control and cooling medium mass control.
This type of undertaking requires the use of a high-speed digital computing unit, provided with flexible and powerful input and output devices and designed in order that a breakdown of one of its components would not, in any case, endanger the operation and the monitoring of the nuclear power plant. 相似文献
1. 1. Participate in the evaluation of proposed FMS systems,
2. 2. Assess the impact of FMS acquisition on existing facilities,
3. 3. Assist in the identification of operational alternatives in “bottle neck” situations.
The pilot study employs a batch-oriented MRP system to provide daily updates of outstanding production center loadings on a monthly planning horizon. Two intelligent terminals are used to access a mini computer facility that executes the simulation models. The terminals have AT-compatible capabilities and are also used as data acquisition devices that support the numerically controlled operations within each work center.
The simulation models represent the 13 work centers of the firm and provide information about the average utilization of each work center, the number of parts in each queue and the average delay of parts in the queues. Future extensions of the models are planned to utilize the terminals' graphic animation capabilities to display the flow of production orders through the manufacturing facility. 相似文献
1. (1) The structure of the controller is simple. This makes it easy to tune the control system.
2. (2) The controller copes well with the detection time delay, and thus high performance is obtained even at a low rolling speed.
3. (3) The flatness error caused by the rolling force variation in mill acceleration and deceleration time would be kept to a minimum by the function to adjust roll bending force using the signal of rolling force.
Author Keywords: Multivariable systems; Flatness control; Rolling mills; Observers 相似文献