Title

Dynamic Modeling of Friction Stir Welding for Model Predictive Control

Keywords

Model predictive control, Friction stir welding, Heat source method, Temperature control, Temperature models

Abstract

Controlling temperature in Friction Stir Welding (FSW) is important for consistent post-weld properties. PID temperature control of FSW has been previously implemented once the process is at a quasi-steady state, but has not worked well during either starting transients or during process changes that significantly alter the system dynamics. This work develops models and theories for the application of Model Predictive Control (MPC) to FSW and assesses temperature predication capabilities in simulation.

Two different model forms are developed for MPC and are evaluated in simulation. The first model is a first-order plus dead time (FOPDT) model. The second is the Hybrid Heat Source model that combines the heat source method and a 1D discretized thermal model of the FSW tool. Model parameters are determined by fitting model predictions to weld data. This is done both manually and via optimization-based curve fitting. The models’ fits are compared quantitatively by calculating the mean-subtracted SSE (MSSSE) and average absolute derivative error. The manually tuned parameter sets result in a better fit by both metrics for both models. The FOPDT model matches the post-startup-transient data better than the Hybrid Heat Source, and is expected to have superior control in this region of the weld. The Hybrid Heat Source model is expected to have superior temperature control during the startup transient.

Original Publication Citation

http://www.sciencedirect.com/science/article/pii/S1526612516300603

Document Type

Peer-Reviewed Article

Publication Date

2016-08-01

Permanent URL

http://hdl.lib.byu.edu/1877/3626

Publisher

Journal of Manufacturing Processes, Elsevier

Language

English

College

Ira A. Fulton College of Engineering and Technology

Department

Chemical Engineering

University Standing at Time of Publication

Assistant Professor