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ETD Abstract Container

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Control of arc weld thermal cycles

Farson, Dave F.
http://rave.ohiolink.edu/etdc/view?acc_num=osu1387446228

Abstract Details

1987, Doctor of Philosophy, Ohio State University, Electrical and Computer Engineering.

In this dissertation, control of weld cooling rates using measurements of weld pool width was studied. Cooling rate controls were designed using an observer-based approach and their performance was tested using numerical simulation. In the observer-based control approach, weld pool width measurements from a welding process are compared to weld width predictions from a welding heat flow model and any error between the two is used to "adjust" the heat flow model. The heat flow model also produces estimates of weld centerline cooling rate which are then used in a feedback control implementation. Two types of observer-based cooling rate controls were formulated and simulation-tested in this dissertation: dynamic and static. Dynamic observers are based upon a dynamic model of the welding heat flow process while static observers use a steady state welding heat flow model. Two different dynamic observers and three different static observers were formulated and studied. The dynamic welding heat flow model upon which the dynamic observers are based was tested by comparing various model outputs with measured steady-state values of these outputs from welding tests. The response of weld width to step arc current perturbations was also studied. With some modification, the model was found to match the cooling rate and pool width data acceptably well. Observer-based feedback cooling rate controls were designed with the aid of a welding heat flow simulation. The compensator design approaches for both dynamic and static observer-based controls was similar. The system response was modeled in piece-wise linear fashion by ARMA models, and the resulting models were used to design compensators yielding to desirable closed-loop response. During control operation, appropriate compensator parameters were selected based upon the system operating point. The response of the observer-based controls was simulated at a variety of operating points and the robustness of the controls was studied. These tests showed that all of the observer formulations except one exhibited acceptable robustness. Finally, multivariable control of the welding process was simulated. In these tests, weld pool width and centerline cooling rate were feedback-controlled simultaneously by varying arc current and travel speed.

Robert J. Mayhan (Advisor)
285 p.
Electrical Engineering

Recommended Citations

Citations

  • Farson, D. F. (1987). Control of arc weld thermal cycles [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1387446228

    APA Style (7th edition)

  • Farson, Dave. Control of arc weld thermal cycles. 1987. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1387446228.

    MLA Style (8th edition)

  • Farson, Dave. "Control of arc weld thermal cycles." Doctoral dissertation, Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1387446228

    Chicago Manual of Style (17th edition)

osu1387446228
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© 1987, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.