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15th World Congress of the International Federation of Automatic Control, 2002

作者： Zhang, Y.M. Liu, Y.C. Welding Research Laboratory Center for Robotics and Manufacturing Systems Department of Electrical and Computer Engineering College of Engineering University of Kentucky LexingtonKY40506 United States

ISBN: (纸本)9783902661746

This paper addresses the development of an adaptive control system for keyhole arc welding process. The system developed adjusts the amperage of the peak current to achieve the desired peak current period under varying manufacturing conditions. A nominal model is selected from models identified using experimental data and is used as the a prior model of the controlled process. A predictive control algorithm has been designed for the nominal model structure. Closed-loop control experiments have been conducted to verify the effectiveness of the developed system under varying set-point and varying travel speed. Copyright © 2002 IFAC.

关键词： Adaptive control systems

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STOCHASTIC MODELLING AND ANALYSIS OF DYNAMIC PLASMA REFLECTION

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IFAC Proceedings Volumes 2002年第1期35卷 271-276页

作者： Y.M. Zhang Y. Ma Center for Robotics and Manufacturing Systems and Department of Electrical and Computer Engineering College of Engineering University of Kentucky Lexington KY 40506 USA

Keyhole arc welding is a cost-effective process to weld thick materials. To successfully apply this process, the state of the keyhole must be accurately detected and used in feedback control. In this paper, the dynamic behavior of the plasma reflection is described using the reflection arc angle (RAA). It is found that the RAA series can be considered an autoregressive moving-average (ARMA) process. The parameters of the ARMA are recursively estimated using the extended least squares algorithm. It is found that the recursive estimates of the model parameters change as the state of the keyhole changes. A discriminator has been proposed to determine the state of the keyhole based on the recursive estimates of the model parameters.

关键词： Autoregressive moving average (ARMA) least squares algorithm impulse transfer function

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MODELING AND CONTROL OF KEYHOLE ARC WELDING PROCESS

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IFAC Proceedings Volumes 2002年第1期35卷 151-156页

作者： Y.M. Zhang Y.C. Liu Welding Research Laboratory Center for Robotics and Manufacturing Systems and Department of Electrical and Computer Engineering College of Engineering University of Kentucky Lexington KY 40506 USA

关键词： Adaptive control manufacturing processes identification predictive control

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Fuzzy classification of plasma reflection for keyhole sensing and control

Fuzzy classification of plasma reflection for keyhole sensin...

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IEEE Conference on Control Technology and Applications (CCTA)

作者： B.E. Losch YuMing Zhang Department of Electrical and Computer Engineering and Center for Robotics and Manufacturing Systems University of Kentucky Lexington KY USA

Keyhole arc welding (KAW) can achieve deeper, narrower penetration than other arc welding processes. If KAW can be controlled in such a way as to minimize the heat input and the size of the weld pool while insuring full penetration, KAW could be an effective and affordable technology to improve the welding of thick materials. The key to developing such a controlled process is the development of a sensor that can detect the development of the keyhole. Preliminary studies have indicated that monitoring the plasma reflection could lead to a practical and accurate sensor for monitoring the keyhole development. Fuzzy logic provides a method for analysing this dynamic process in real time.

关键词： Fuzzy control Reflection Plasma welding Monitoring Size control Temperature control Thickness control Process control Plasma materials processing Fuzzy logic

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DETERMINING KEYHOLE STABILITY FOR PLASMA ARC WELDING PROCESS CONTROL

DETERMINING KEYHOLE STABILITY FOR PLASMA ARC WELDING PROCESS...

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ASME 1999 International Mechanical engineering Congress and Exposition, IMECE 1999

作者： Zhang, Shaobin Zhang, YuMing University Of Kentucky Center For Robotics And Manufacturing Systems Department Of Electrical Engineering LexingtonKY40506 United States

ISBN: (纸本)9780791816462

Stability of the keyhole plays a fundamental role in producing quality welds in keyhole plasma arc welding. Currently, keyhole size is assumed to be a measurement of its stability. To verify this idea, keyhole and weld pool were simultaneously imaged from the opposite side of the welding torch. Experimental results revealed that the width of the keyhole was not correlative with the stability of the keyhole: as long as the keyhole mode was maintained, the width remained constant despite the changes in the welding current and speed. However, it can be used to estimate the lower limit of the pool width for preventing keyhole collapse. also, the upper limit of the pool width for preventing bum-through is approximately fixed for given applications. Hence, in this sWdy, pool width, its upper limit, and keyhole width were used to determine the margins of the process from collapse and bum-through. To measure the state of the stability of the keyhole process, the stability distance and stability factor were proposed. Based on the imaging system used, the state of the stability can be monitored in real-time. © 1999 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Welds

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PRECISION SENSING OF ARC LENGTH IN GTAW BASED ON ARC LIGHT SPECTRUM

PRECISION SENSING OF ARC LENGTH IN GTAW BASED ON ARC LIGHT S...

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ASME 1999 International Mechanical engineering Congress and Exposition, IMECE 1999

作者： Li, P.J. Zhang, Y.M. Welding Research And Development Laboratory Center For Robotics And Manufacturing Systems University Of Kentucky LexingtonKY40506-0108 United States Department Of Electrical Engineering University Of Kentucky LexingtonKY40506-0108 United States

ISBN: (纸本)9780791816462

This work aims at improving the measurement accuracy of arc length using the spectrum of arc light at a particular wavelength during gas tungsten arc welding with argon shield. To this end, effects of welding parameters on spectral distributions were studied. To verify the effects of base metal and arc length, the arc column was also sampled horizontally as layers for spectral analysis. Results showed that spectral lines of argon atoms are determined by arc length and independent of welding parameters other than the arc length. Based on these findings, a compact arc light sensor has been designed to measure the arc length with an adequate accuracy. A closed-loop arc length control system has been developed with the proposed sensor. © 1999 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Spectrum analysis

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Approximating state sets using circumscribing polyhedron with fewer facets

Approximating state sets using circumscribing polyhedron wit...

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IEEE Southeastcon

作者： Hian-Suan Chew L.E. Holloway Department of Electrical Engineering and Center for Robotics and Manufacturing Systems University of Kentucky Lexington KY USA

A polyhedron can be described using a set of linear constraints that bound the polyhedron. This paper considers the problem of approximating a polyhedron with a circumscribing polyhedron with fewer constraints. We discuss three methods to find such a circumscribing polyhedra, and compare the resulting approximation errors using sets of randomly generated polyhedra. The work is motivated by the problem of approximating state estimate sets for a class of uncertain dynamic systems.

关键词： manufacturing systems Robots Approximation error State estimation Uncertain systems

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Redundant actuation for improving kinematic manipulability

Redundant actuation for improving kinematic manipulability

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IEEE International Conference on robotics and Automation (ICRA)

作者： J.F. O'Brien J.T. Wen Center for Advanced Technology in Automation Robotics & Manufacturing Department of Electrical Computer & Systems Engineering Rensselaer Polytechnic Institute Troy NY USA

Parallel mechanisms frequently contain an unstable type of singularity that has no counterpart in serial mechanisms. When the mechanism is at or near this type of singularity, it loses the ability to counteract external forces in certain directions. By altering the mechanism through, for example, additional kinematic linkages, the singularity can be modified or even removed. Another approach is to actuate certain unactuated degrees of freedom. The manipulability is guaranteed to improve over the original mechanism, but the mechanism is now over-actuated. By studying a recently proposed parallel machining center, we examine the effectiveness of singularity modification through redundant actuation. As a metric, we use the condition number of the recently developed manipulability ellipsoid for general parallel mechanisms.

关键词： Kinematics Parallel robots Ellipsoids manufacturing automation robotics and automation Computer aided manufacturing Manipulators Concurrent computing systems engineering and theory Couplings

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Kinematic manipulability of general constrained rigid multibody systems

Kinematic manipulability of general constrained rigid multib...

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IEEE International Conference on robotics and Automation (ICRA)

作者： J.T. Wen L.S. Wilfinger Center for Advanced Technology in Automation Robotics & Manufacturing Department of Electrical Computer & Systems Engineering Rensselaer Polytechnic Institute RPI Troy NY USA

Extends the kinematic manipulability concept commonly used for serial manipulators to general constrained rigid multibody systems. Examples of such systems include multiple cooperating manipulators, multiple fingers holding a payload, multi-leg walking robots, and variable geometry trusses. Explicit formulas for velocity and force manipulability ellipsoids are derived and their duality explained. The concept of unstable grasp and manipulable grasp are also extended and illustrated with examples.

关键词： Kinematics Torque Ellipsoids manufacturing automation robotics and automation Computer aided manufacturing Manipulators Fingers Legged locomotion Robots

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Interval model based control of gas metal arc welding

Interval model based control of gas metal arc welding

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American Control Conference (ACC)

作者： Y.M. Zhang E. Liguo B.L. Walcott Center for Robotics and Manufacturing Systems Welding Research and Development Laboratory University of Kentucky Lexington KY US Department of Electrical Engineering University of Kentucky Lexington KY USA

A control system is developed to control pulsed gas metal arc welding process. To guarantee the desired metal transfer mode, i.e., one drop per pulse, the welding current is switched from the peak level to the background level so that an oscillation of the droplet is excited up. When the droplet moves downwards, the welding current is switched back to the peak level. The combination of the downward momentum of the oscillating droplet and the increased electromagnetic force guarantees that the droplet be detached. Instead of the duration of the background current, the waveform of the welding current is adjusted to control the melting rate of the electrode wire so that the metal transfer frequency can keep constant during welding. To simplify the control system, the ranges of the welding operational parameters are used to quantify the uncertainty in the dynamic model of the welding process. Based on the uncertainty range of the dynamic model, a single control algorithm has been developed to handle different operational parameters. Experiments confirmed effectiveness of the developed system.

关键词： Welding Electrodes Control systems Wire Feeds Electromagnetic forces Frequency Uncertainty Heat transfer Process control

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