Nonlinear identification of laser welding process

Xiaodong Na, Yu Ming Zhang, Yu Sheng Liu, Bruce Walcott

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


It has been well recognized that weld pool geometry plays a critical role in fusion welding process such as laser welding. In this study, the authors establish a standard diode laser welding system and perform a series of experiments to investigate correlations between welding parameters and the weld pool geometry. Custom digital camera for image acquisition and software for image processing are implemented in the system to obtain the surface width of the weld pool. Experimental data has demonstrated significant nonlinearity in the diode laser welding process. The authors thus propose a continuous Hammerstein identification methodology to approximate this process. A single-input-single-output (SISO) nonlinear continuous model is then identified and validated for the diode laser welding process using the experimental data. Because by nature laser welding is a heat transferring process in which the heat applied to a unit length of the work-piece along the weld seam is inversely proportional to the travelling speed, the model takes the reciprocal of welding speed as the input and the top surface width as the output. For this methodology, all experiments need to be dynamic and be conducted using either Step or PRTS (pseudo-random ternary signal) inputs. In a revised and simplified version, the linear dynamics is identified first from a single dynamic experiment and then used in the identification of the nonlinearity with other static response experiments. The validation proves both identification methods are capable of predicting the surface width of the weld pool.

Original languageEnglish
Article number5208260
Pages (from-to)927-934
Number of pages8
JournalIEEE Transactions on Control Systems Technology
Issue number4
StatePublished - Jul 2010

Bibliographical note

Funding Information:
Manuscript received April 15, 2007; revised May 22, 2009; accepted June 04, 2009. Manuscript received in final form June 18, 2009. First published August 18, 2009; current version published June 23, 2010. Recommended by Associate Editor A. Isaksson. This work was supported in part by the National Science Foundation under Grant CMMI-0527889 and the Natural Science Foundation of China under Grant 60540420641.


  • Hammerstein
  • Identification
  • Laser
  • Model
  • Nonlinear
  • Welding

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Electrical and Electronic Engineering


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