Temperature Field Regulation in Thermal Cutting for Layered Manufacturing

1999 ◽  
Vol 121 (3) ◽  
pp. 440-447 ◽  
Author(s):  
N. Fourligkas ◽  
C. Doumanidis
Keyword(s):  
Temperature Field ◽  
Thermal Processing ◽  
Pole Placement ◽  
Time Variability ◽  
Material Structure ◽  
Source Power ◽  
Modeling And Control ◽  
Thermal Sensing ◽  
Process Disturbances ◽  
And Control

A general thermal modeling and control methodology for thermal processing of layered materials for rapid prototyping technologies is established in this article. An analytical multivariable model of lumped temperature outputs generated by heat inputs on a surface grid is developed, based on Green’s function and state-space descriptions. The few independent parameters needed in such a linearized formulation are experimentally identified, and their time-variability reflects the heat transfer nonlinearities and process disturbances. A robust controller with thermal feedback is designed by pole placement methods, to obtain a specified dynamic temperature field yielding the desired material structure and properties. The regulated thermal processing is optimized in real time by proper heat source power modulation and torch guidance through a simulated annealing strategy. Its performance is tested on both the computer model and a laboratory station, using robotically guided plasma-arc cutting and infrared thermal sensing, in regulating the sensitized zone during blanking of an elementary contour pattern on stainless steel.

Dynamic Modeling and Control of Dual Wheeled Mobile Robots Compliantly Coupled to a Common Payload

1999 ◽  
Vol 121 (3) ◽  
pp. 457-461 ◽  
Author(s):  
Thurai Vinay ◽  
Bradley Postma ◽  
Theo Kangsanant
Keyword(s):  
Mobile Robots ◽  
Pole Placement ◽  
Nonlinear Controller ◽  
Wheeled Mobile Robots ◽  
Adaptive Controllers ◽  
Modeling And Control ◽  
Self Tuning ◽  
The Individual ◽  
And Control ◽  
Placement Technique

Lagrange formalism is applied to derive a dynamic model, and design a nonlinear controller for two nonholonomic, differentially steered, wheeled mobile robots compliantly linked to a common payload. The resulting multivariable system model is of a large order and can be block decoupled by selective state feedback into five independent subsystems, two of which effectively represent the deviation dynamics of the individual robots from a prescribed path; two others represent their forward motion dynamics; while the fifth describes the payload dynamics. Controllers for each of the robot subsystems, including self-tuning adaptive controllers for the nonlinear deviation dynamics subsystems, are designed by the pole-placement technique. System performance is then evaluated via simulation for the case where each robot is undergoing curvilinear motion.

Modeling and control of rapid thermal processing

1992 ◽  
Author(s):  
Charles D. Schaper ◽  
Young M. Cho ◽  
Poogyeon Park ◽  
Stephen A. Norman ◽  
Paul Gyugyi ◽  
...  
Keyword(s):  
Thermal Processing ◽  
Rapid Thermal Processing ◽  
Modeling And Control ◽  
And Control

Scan Welding: Thermal Modeling and Control of Material Processing

1999 ◽  
Vol 121 (3) ◽  
pp. 417-424 ◽  
Author(s):  
G. Korizis ◽  
C. Doumanidis
Keyword(s):  
Real Time ◽  
Thermal Control ◽  
Joint Surface ◽  
Material Structure ◽  
Real Time Control ◽  
Welding Temperature ◽  
Modeling And Control ◽  
Gas Tungsten Arc ◽  
Time Control ◽  
And Control

This article provides a thermal analysis of scan welding, as a redesign of classical joining methods, employing computer technology to ensure the composite morphologic, material and mechanical integrity of the joint. This is obtained by real-time control of the welding temperature field by a proper dynamic heat input distribution on the weld surface. This distribution is implemented in scan welding by a single torch, sweeping the joint surface by a controlled reciprocating motion, and power adjusted by feedback of infrared temperature measurements in-process. An off-line numerical simulation of the thermal field in scan welding is established, as well as a linearized multivariable model with real-time parameter identification. An adaptive thermal control scheme is thus implemented and validated both computationally and experimentally on a robotic Gas-Tungsten Arc Welding setup. The resulting productivity and quality features of scan welding are comparatively analyzed in terms of material structure and properties of the joint.

Distributed-Parameter Design of Virtual Source Thermal Processing Methods

1995 ◽  
Author(s):  
Charalabos Doumanidis ◽  
Nikolaos Fourligkas
Keyword(s):  
Thermal Processing ◽  
Distributed Parameter ◽  
Material Structure ◽  
Process Conditions ◽  
Virtual Source ◽  
Real Time Control ◽  
Source Power ◽  
Time Control ◽  
Thermal Techniques ◽  
Line Design

Abstract In thermal manufacturing methods, visualization of the thermally generated distributions of material structure and properties in the products forms the basis for the development of a methodology for off-line design of the process conditions in virtual-source thermal techniques. These are implemented by timesharing a single heat source, scanning the external surface of the processed part to generate a flexible heat input distribution, and thus a specified temperature field yielding the desired thermal quality of the product. A numerical simulation of generic thermal processing is developed, integrating a solid conduction description to a flow model in molten regions. This computational model is validated by a comparative thermal study and is used for the design of the virtual source power and trajectory in rapid prototyping of laminated objects with specified geometric tolerances. Virtual-source processing based on real-time control with infrared thermal feedback is currently simulated for other thermal manufacturing processes.

Modeling and Control of Timeshared and Scanned Torch Welding

1994 ◽  
Vol 116 (3) ◽  
pp. 387-395 ◽  
Author(s):  
C. C. Doumanidis
Keyword(s):  
Thermal Characteristics ◽  
Distributed Parameter ◽  
Weld Quality ◽  
Modeling And Control ◽  
Quality Regulation ◽  
Pipe Welding ◽  
Part Surface ◽  
Decoupled Control ◽  
Process Disturbances ◽  
And Control

Optimization of the weld quality and productivity requires in-process identification and simultaneous regulation of several thermal characteristics of the joint. Since in traditional single-torch welding only a few process variables can be modulated in real-time, multiple source configurations are implemented by a rapidly reciprocated (timeshared) GTAW torch to obtain decoupled control of the weld geometry, structure and properties. Further, to widen the range of achievable weld features, a scanning motion of the torch on the entire part surface generates the necessary heat distribution for any specified thermal field in the weld, which is observed through surface temperature measurements. Analytical, numerical, and experimental thermal modeling techniques are employed for the design of multivariable adaptive and distributed-parameter controllers, applied to girth and flange welding simulations, and tested in seam pipe welding experiments, for rejection of process disturbances and for weld quality regulation performance.

Sign in / Sign up

Export Citation Format

Share Document