Distributed-Parameter Control of the Heat Source Trajectory in Thermal Materials Processing

1996 ◽  
Vol 118 (4) ◽  
pp. 571-578 ◽  
Author(s):  
C. Doumanidis ◽  
N. Fourligkas
Keyword(s):  
Temperature Field ◽  
Heat Source ◽  
Real Time ◽  
Welding Process ◽  
Thermal Control ◽  
Distributed Parameter ◽  
Material Structure ◽  
Parameter Control ◽  
Real Time Control ◽  
Distributed Parameter Control

In thermal manufacturing processes performed by a localized, sequentially moving heat source, simultaneous regulation of multiple thermal quality characteristics requires real-time control of the temperature field developed through the distributed heat input on the part surface. Such control of the thermal field to a desired distribution employs infrared sensing and feedback of the surface temperature hill, to modulate the torch power and motion in-process. The torch trajectory is guided in real time by an efficient optimization algorithm based on the concept of moving complexes. This distributed-parameter control strategy is developed using a numerical simulation model of thermal processing, and its performance is evaluated experimentally in heat treatment of thin stainless steel plates. The thermal controller is applied to the new scan welding process, in which it drives the torch in a reciprocating motion along the weld, yielding a uniform and smooth temperature field, and thus a favorable material structure and mechanical properties. Application of such thermal control to various other material processing methods is also investigated.

Scanned Orbital Welding: Thermal Modeling and Lumped Adaptive Control

1999 ◽  
Vol 121 (4) ◽  
pp. 393-399
Author(s):  
H. Sfetsos ◽  
J. Angelis ◽  
C. Doumanidis
Keyword(s):  
Temperature Field ◽  
Reference Model ◽  
Thermal Control ◽  
Distributed Parameter ◽  
Stainless Steel Surface ◽  
Orbital Welding ◽  
Distributed Parameter Control ◽  
Welding Torch ◽  
Temperature Feedback ◽  
Self Tuning

Scan orbital welding of cylindrical vessel, flange, and piping parts is performed by their rapid revolution under a radially or axially translated heat source, with its power modulated so as to implement a specified thermal distribution. Thus, the plasma-arc welding torch sweeps the stainless steel surface to generate a desirable temperature field and the concomitant material features. A numerical simulation of the thermal field is developed for off-line analysis. On this basis, a lumped thermal regulator of the heat-affected zone, employing infrared temperature feedback at a single spot, as well as standard PI, gain scheduling, and self-tuning control algorithms is tested. The thermal model is also employed for real-time torch efficiency identification and compensation. The numerical reference model serves as the basis for an in-process adaptive thermal control system to regulate the temperature field, using thermal feedback from the infrared pyrometer. A distributed-parameter control strategy, with guidance of the torch motion and power by a new weighted attraction strategy to randomly sampled points, is tested on scan-welded flanges. The regulator is validated computationally and experimentally, and its applicability to other scanned processing of materials is considered.

Thermal Manufacturing Process Control by Lumped Mimo and Distributed-Parameter Methods

1995 ◽  
Vol 117 (4) ◽  
pp. 625-632 ◽  
Author(s):  
C. C. Doumanidis
Keyword(s):  
Real Time ◽  
Power Distribution ◽  
Thermal Characteristics ◽  
Thermal Control ◽  
Distributed Parameter ◽  
Material Structure ◽  
Manufacturing Process Control ◽  
Part Surface ◽  
Regulation Strategies ◽  
Continuous Power

A variety of geometric, material structure, and stress/distortion attributes are needed to characterize the quality of thermally manufactured products. Because of in-process sensing difficulties and transportation lags, these features must be regulated in real time through appropriate thermal outputs, measured by non-contact infrared pyrometry. In thermal processes with a localized, sequentially moving heat source, the necessary heat input distribution on the part surface is supplied by an innovative timeshared or scanned torch modulation, in a raster or vector pattern. A unified lumped multivariable and a distributed-parameter quasilinear modeling formulation provide a design methodology and real-time reference for the development of finite- or infinite-state adaptive thermal control systems. These controllers modulate the power and motion of a single torch, supplying distinct concentrated heat inputs or a continuous power distribution on the part surface, so as to obtain the specified thermal characteristics or the entire temperature field. These regulation strategies are computationally tested and implemented experimentally in arc welding, but their applicability can be extended to a variety of thermal manufacturing processes.

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.

Sign in / Sign up

Export Citation Format

Share Document