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Research Papers

Height Control in Laser Cladding Using Adaptive Sliding Mode Technique: Theory and Experiment

[+] Author and Article Information
Meysar Zeinali

Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, N2L 3G1, Canadazeinali@uwaterloo.ca

Amir Khajepour

Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, N2L 3G1, Canadaakhajepour@uwaterloo.ca

J. Manuf. Sci. Eng 132(4), 041016 (Aug 06, 2010) (10 pages) doi:10.1115/1.4002023 History: Received June 24, 2009; Revised June 07, 2010; Published August 06, 2010; Online August 06, 2010

A closed-loop control of the laser cladding process is desired due to difficulties encountered in depositing a layer with acceptable quality from both geometrical and metallurgical point of views. One of the main parameters to achieve the desired geometry in laser cladding process is the height of the deposited layers. In this paper, a real-time measurement and control of the clad height is presented. Due to complex nature of the process and presence of uncertainties, a robust and adaptive sliding mode control is proposed and implemented to control the clad height. The velocity of the substrate is used as a control input while the molten pool height, which is obtained using a charge-coupled device (CCD) camera and an image processing algorithm is used as a feedback signal. Stability of the controller is proven in the presence of time-varying uncertainties and the performance of the closed-loop system is validated by simulation and experiments. The experimental results are promising and show that the geometrical accuracy of the deposited layers can be improved significantly.

Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of laser cladding process and substrate surface roughness

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Figure 2

Configuration of laser cladding setup

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Figure 3

Comparison of model output and actual process output for: (a) well-identified parameters and (b) slightly approximated parameters

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Figure 4

Convergence of system trajectories to sliding surface: (a) system trajectories in state space and (b) sliding function behavior in time domain

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Figure 5

Chattering-free control input, and convergence of process height to the desired height for time-varying uncertainty

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Figure 6

Comparison of system trajectories convergence

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Figure 7

Convergence of system trajectories to sliding surface

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Figure 8

Chattering-free control input and convergence of clad height to the desired height

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Figure 9

Controller performance for the step command

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Figure 10

Convergence of S(t) to zero after a large change in clad height

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Figure 11

Block diagram of the proposed controller with uncertainties estimation

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Figure 12

Image processing results: (a) original image of melt pool and (b) processed image of melt pool

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Figure 13

Control system performance to a simple linear reference input

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Figure 14

Control system performance in tracking step reference input

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Figure 15

Control system performance in tracking multiple step reference input

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Figure 16

Control system performance in tracking sinusoidal reference input

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Figure 17

Substrate with two slots

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Figure 18

Deposition of a clad layer on substrate with two slots: (a) slot with 0.3 mm and (b) slot with 0.6 mm

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