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Improved Temperature and Depth Control During FSW of Copper Canisters Using Feedforward Compensation

Cederqvist, Lars LU ; Garpinger, Olof LU ; Cervin, Anton LU and Nielsen, Isak (2015) Friction Stir Welding and Processing VIII In Friction Stir Welding and Processing VIII p.69-76
Abstract
The welding procedure to seal copper canisters requires variable power input throughout the 45 minute long weld cycle to keep the probe temperature within the process window. By using a cascaded loop that determines the power input requirement, the controller will not be dependent on repeatability in the necessary power input between weld cycles, and the lag time in the probe temperature measurement will not be critical. Due to fast-changing thermal boundary conditions during the downward sequence, a feedforward to the power input was designed to further improve controller performance.



In addition to the cascade controller adjusting the tool rotation rate, a depth controller is adjusting the axial force to control the... (More)
The welding procedure to seal copper canisters requires variable power input throughout the 45 minute long weld cycle to keep the probe temperature within the process window. By using a cascaded loop that determines the power input requirement, the controller will not be dependent on repeatability in the necessary power input between weld cycles, and the lag time in the probe temperature measurement will not be critical. Due to fast-changing thermal boundary conditions during the downward sequence, a feedforward to the power input was designed to further improve controller performance.



In addition to the cascade controller adjusting the tool rotation rate, a depth controller is adjusting the axial force to control the shoulder depth. The purpose is to eliminate flash due to excessive shoulder depth and to control the position of the probe tip, which influeces the size and shape of the hook defect produced. Controlling depth is challenging for several reasons, including deflection in the welding machine and thermal expansion of the weld material, and also results in cross-coupling between axial force and spindle torque. The cross-coupling was handled by another feedforward compensator that adjusts the tool rotation rate based on the commanded axial force.



The implemented controllers and feedforward compensators have been evaluated over several welds with good results, where the depth is kept within ±0.1mm when the tool reaches the joint line sequence and the probe temperature is held within ±5°C during full circumferential welds compared to a process window of ±60°C. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Chapter in Book/Report/Conference proceeding
publication status
published
subject
keywords
friction stir welding, copper, automatic control, tool depth control
in
Friction Stir Welding and Processing VIII
editor
Mishra, Rajiv S.; Mahoney, Murray W.; Sato, Yutaka and Hovanski, Yuri
pages
8 pages
publisher
John Wiley & Sons
conference name
Friction Stir Welding and Processing VIII
external identifiers
  • Scopus:84937510046
ISBN
9781119082491
language
English
LU publication?
yes
id
a19ba3f2-a1bb-4aa6-9c93-3c41cec8bdda (old id 8858380)
date added to LUP
2016-03-15 18:21:27
date last changed
2016-10-13 04:45:17
@misc{a19ba3f2-a1bb-4aa6-9c93-3c41cec8bdda,
  abstract     = {The welding procedure to seal copper canisters requires variable power input throughout the 45 minute long weld cycle to keep the probe temperature within the process window. By using a cascaded loop that determines the power input requirement, the controller will not be dependent on repeatability in the necessary power input between weld cycles, and the lag time in the probe temperature measurement will not be critical. Due to fast-changing thermal boundary conditions during the downward sequence, a feedforward to the power input was designed to further improve controller performance.<br/><br>
<br/><br>
In addition to the cascade controller adjusting the tool rotation rate, a depth controller is adjusting the axial force to control the shoulder depth. The purpose is to eliminate flash due to excessive shoulder depth and to control the position of the probe tip, which influeces the size and shape of the hook defect produced. Controlling depth is challenging for several reasons, including deflection in the welding machine and thermal expansion of the weld material, and also results in cross-coupling between axial force and spindle torque. The cross-coupling was handled by another feedforward compensator that adjusts the tool rotation rate based on the commanded axial force.<br/><br>
<br/><br>
The implemented controllers and feedforward compensators have been evaluated over several welds with good results, where the depth is kept within ±0.1mm when the tool reaches the joint line sequence and the probe temperature is held within ±5°C during full circumferential welds compared to a process window of ±60°C.},
  author       = {Cederqvist, Lars and Garpinger, Olof and Cervin, Anton and Nielsen, Isak},
  editor       = {Mishra, Rajiv S. and Mahoney, Murray W. and Sato, Yutaka and Hovanski, Yuri},
  isbn         = {9781119082491},
  keyword      = {friction stir welding,copper,automatic control,tool depth control},
  language     = {eng},
  pages        = {69--76},
  publisher    = {ARRAY(0xadfd328)},
  series       = {Friction Stir Welding and Processing VIII},
  title        = {Improved Temperature and Depth Control During FSW of Copper Canisters Using Feedforward Compensation},
  year         = {2015},
}