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Dustin Marshall Jose Mojica Ken Ross John Hedengren Brigham Young University Friction Stir Welding Control: Feasibility Study
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Friction Stir Welding Control: Feasibility Studyapmonitor.com/wiki/uploads/Main/apm_fsw_15Nov11.pdf · Friction Stir Welding Control Overview Friction Stir welding is a solid state

Jun 14, 2020

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Page 1: Friction Stir Welding Control: Feasibility Studyapmonitor.com/wiki/uploads/Main/apm_fsw_15Nov11.pdf · Friction Stir Welding Control Overview Friction Stir welding is a solid state

Dustin MarshallJose MojicaKen Ross

John HedengrenBrigham Young University

Friction Stir Welding Control: Feasibility Study

Page 2: Friction Stir Welding Control: Feasibility Studyapmonitor.com/wiki/uploads/Main/apm_fsw_15Nov11.pdf · Friction Stir Welding Control Overview Friction Stir welding is a solid state

Friction Stir Welding Control Overview

Friction Stir welding is a solid state metal joining process

A rotating tool creates heat and plasticizes the metal.  This allows the metal to be “stirred” around.

Page 3: Friction Stir Welding Control: Feasibility Studyapmonitor.com/wiki/uploads/Main/apm_fsw_15Nov11.pdf · Friction Stir Welding Control Overview Friction Stir welding is a solid state

Friction Stir Welding Applications

Page 4: Friction Stir Welding Control: Feasibility Studyapmonitor.com/wiki/uploads/Main/apm_fsw_15Nov11.pdf · Friction Stir Welding Control Overview Friction Stir welding is a solid state

Feasibility Study Objectives Develop Simplified Model of FSW Process

PDE of Tool Heat Transfer

Investigate feasibility of FSW model‐based control 2‐3 weeks of effort Explore feasibility through simulation Compare model to run data Demonstrate in simulation

PID (Proportional Integral Derivative Control) MPC (Model Predictive Control)

Detail projected effort / costs to implement MPC Develop implementation plan

Page 5: Friction Stir Welding Control: Feasibility Studyapmonitor.com/wiki/uploads/Main/apm_fsw_15Nov11.pdf · Friction Stir Welding Control Overview Friction Stir welding is a solid state

FSW Process Model ‐ FOPDT Model #1 of FSW Process – Step Up in Power

First Order Plus Dead‐Time (FOPDT) Model Model predictions on same Aluminum data Gain (Kp): 131.7 °C/hp Time Constant (taup): 16.5 sec Dead‐time (thetap): 1 sec

Page 6: Friction Stir Welding Control: Feasibility Studyapmonitor.com/wiki/uploads/Main/apm_fsw_15Nov11.pdf · Friction Stir Welding Control Overview Friction Stir welding is a solid state

FSW Process Model ‐ FOPDT Model #1 of FSW Process – Step Down in Power

First Order Plus Dead‐Time (FOPDT) Model Model predictions on same Aluminum data Gain (Kp): 120 °C/hp Time Constant (taup): 20‐30 sec Dead‐time (thetap): 1 sec

Page 7: Friction Stir Welding Control: Feasibility Studyapmonitor.com/wiki/uploads/Main/apm_fsw_15Nov11.pdf · Friction Stir Welding Control Overview Friction Stir welding is a solid state

FSW Process Model – PDE Model Model #2 of FSW Process

PDE of Tool Heat Transfer Demonstrate model predictions on Aluminum Fit PDE model to process data

Estimate Fraction of Energy to Tool to Match Temperature

Page 8: Friction Stir Welding Control: Feasibility Studyapmonitor.com/wiki/uploads/Main/apm_fsw_15Nov11.pdf · Friction Stir Welding Control Overview Friction Stir welding is a solid state

FSW Temperature Control Current Practice

PID Control Start‐up procedure

Constant rotational speed Manual adjustments to guide temperature

Z Axis Force

Proposed Control Strategy Model based control Automatic control through start‐up

Limit overshoot Keep process within constraints

Rate of change limits for motor power (HP) Rate of change limits for tip temperature

Page 9: Friction Stir Welding Control: Feasibility Studyapmonitor.com/wiki/uploads/Main/apm_fsw_15Nov11.pdf · Friction Stir Welding Control Overview Friction Stir welding is a solid state

Comparing PID and MPCTempe

rature (°C)

Objective Order (#1=most important)#1: Observe rate of change limit#2: Move to new set point quickly#3: Minimize HP movement

Page 10: Friction Stir Welding Control: Feasibility Studyapmonitor.com/wiki/uploads/Main/apm_fsw_15Nov11.pdf · Friction Stir Welding Control Overview Friction Stir welding is a solid state

Model Predictive ControlTempe

rature (°C)

Power (H

P)

#2 Drive to Target

#1: Rate of change limits

#3: Minimum Power Changes

Page 11: Friction Stir Welding Control: Feasibility Studyapmonitor.com/wiki/uploads/Main/apm_fsw_15Nov11.pdf · Friction Stir Welding Control Overview Friction Stir welding is a solid state

Operate Within ConstraintsTempe

rature Rate (°C/sec)

Page 12: Friction Stir Welding Control: Feasibility Studyapmonitor.com/wiki/uploads/Main/apm_fsw_15Nov11.pdf · Friction Stir Welding Control Overview Friction Stir welding is a solid state

Rate of Change for PID and MPCTempe

rature Rate (°C/sec)

Page 13: Friction Stir Welding Control: Feasibility Studyapmonitor.com/wiki/uploads/Main/apm_fsw_15Nov11.pdf · Friction Stir Welding Control Overview Friction Stir welding is a solid state

Recommendations Model Predictive Control has advantages for:

Start‐up Large load changes Constrained control ‐MV or CV tuning

Start control studies now with FOPDT model Interface with PLC through OPC connection to RS Linx Existing equipment sufficient

Address complex modeling / control issues Seek funding for a graduate student Investigate multi‐variable control