Path Force Control for Friction Stir Welding Processes


In Friction Stir Welding (FSW) processes, force control can be used to achieve good welding quality. This paper presents the systematic design and implementation of a FSW path force controller. The path force is modeled as a nonlinear function of the FSW process parameters (i.e., plunge depth, tool traverse rate, and tool rotation speed). An equipment model, which includes a communication delay, is constructed to relate the commanded and measured tool rotation speed. Based on the dynamic process and equipment models, a feedback controller for the path force is designed using the Polynomial Pole Placement technique. The controller is implemented in a Smith Predictor–Corrector structure to compensate for the inherent equipment communication delay and the controller parameters are tuned to achieve the best closed loop response possible given equipment limitations. In the path force controller implementation, a constant path force is maintained, even in the presence of gaps, and wormhole generation during the welding process is eliminated by regulating the path force.

Meeting Name

ASME 2008 Dynamic Systems and Control Conferences (2008: Oct. 20-22, Ann Arbor, MI)


Mechanical and Aerospace Engineering

Keywords and Phrases

Closed loop response; Communication delays; Controller parameter; Dynamic process; Equipment models; Feedback controller; Force controller; Friction stir; Nonlinear functions; Polynomial pole placement; Process parameters; Smith predictor-corrector; Systematic designs; Tool rotations; Traverse rate; Welding process; Welding quality; Controllers; Dynamic programming; Dynamical systems; Electric welding; Equipment; Force control; Friction; Friction stir welding; Gas welding; Rotation; Process control

International Standard Book Number (ISBN)


Document Type

Article - Conference proceedings

Document Version


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© 2009 American Society of Mechanical Engineers (ASME), All rights reserved.

Publication Date

01 Oct 2009