Design and implementation of a general tracking controller for Friction Stir Welding processes

Oakes, Thomas; Landers, Robert G.

doi:10.1109/acc.2009.5160405

Cited by 12 publications

(3 citation statements)

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“…Axial force is a major process parameter that generates friction between the tool and the workpiece. A constant axial force is essential to generate friction and avoid surface voids and wormhole formation during welding, which requires a force controller in the process [52]. Tool force control generates better quality and strength weld joints [53].…”

Section: Process Parametersmentioning

confidence: 99%

A Review of Optimization and Measurement Techniques of the Friction Stir Welding (FSW) Process

Prabhakar,

Korgal,

Shettigar

et al. 2023

JMMP

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This review reports on the influencing parameters on the joining parts quality of tools and techniques applied for conducting process analysis and optimizing the friction stir welding process (FSW). The important FSW parameters affecting the joint quality are the rotational speed, tilt angle, traverse speed, axial force, and tool profile geometry. Data were collected corresponding to different processing materials and their process outcomes were analyzed using different experimental techniques. The optimization techniques were analyzed, highlighting their potential advantages and limitations. Process measurement techniques enable feedback collection during the process using sensors (force, torque, power, and temperature data) integrated with FSW machines. The use of signal processing coupled with artificial intelligence and machine learning algorithms produced better weld quality was discussed.

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Section: Process Parametersmentioning

confidence: 99%

A Review of Optimization and Measurement Techniques of the Friction Stir Welding (FSW) Process

Prabhakar,

Korgal,

Shettigar

et al. 2023

JMMP

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“…They implemented force controlled welding and presented welds with a constant axial force. Oakes et al [14] developed a dynamic process model relating the travel speed, spindle FSW Tool Weld FSW Tool speed and plunge depth to the axial force and implemented a force controller that tracks both constant and sinusoidal desired forces.…”

Section: Rotationmentioning

confidence: 99%

“…Phase lag due to time delay Closed-loop control of axial force by vertical tool position adjustments has not been implemented on our previous testbed (CNC mill) due to system limitations (i.e., lack of ability to adjust the vertical tool position in real-time), but has been employed previously by other researchers [11][12][13][14]. Figure 16 shows the block diagram of the axial force control system implemented in this work.…”

Section: Closed-loop Controllermentioning

confidence: 99%

Combined Temperature and Force Control for Robotic Friction Stir Welding

Fehrenbacher

Smith

Duffie

et al. 2014

Journal of Manufacturing Science and Engineering

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Use of robotic friction stir welding (FSW) has gained in popularity as robotic systems can accommodate more complex part geometries while providing high applied tool forces required for proper weld formation. However, even the largest robotic FSW systems suffer from high compliance as compared to most custom engineered FSW machines or modified computer numerical control (CNC) mills. The increased compliance of robotic FSW systems can significantly alter the process dynamics such that control of traditional weld parameters, including plunge depth, is more difficult. To address this, closed-loop control of plunge force has been proposed and implemented on a number of systems. However, due to process parameter and condition variations commonly found in a production environment, force control can lead to oscillatory or unstable conditions and can, in extreme cases, cause the tool to plunge through the workpiece. To address the issues associated with robotic force control, the use of simultaneous tool interface temperature control has been proposed. In this paper, we describe the development and evaluation of a closed-loop control system for robotic friction stir welding that simultaneously controls plunge force and tool interface temperature by varying spindle speed and commanded vertical tool position. The controller was implemented on an industrial robotic FSW system. The system is equipped with a custom real-time wireless temperature measurement system and a force dynamometer. In support of controller development, a linear process model has been developed that captures the dynamic relations between the process inputs and outputs. Process validation identification experiments were performed and it was found that the interface temperature is affected by both spindle speed and commanded vertical tool position while axial force is affected primarily by commanded vertical tool position. The combined control system was shown to possess good command tracking and disturbance rejection characteristics. Axial force and interface temperature was successfully maintained during both thermal and geometric disturbances, and thus weld quality can be maintained for a variety of conditions in which each control strategy applied independently could fail. Finally, it was shown through the use of the control process model, that the attainable closed-loop bandwidth is primarily limited by the inherent compliance of the robotic system, as compared to most custom engineered FSW machines, where instrumentation delay is the primary limiting factor. These limitations did not prevent the implementation of the control system, but are merely observations that we were able to work around.

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