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Emissivity compensated spectral pyrometry for varying emissivity metallic measurands
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för automation och datateknik. (PTW)ORCID-id: 0000-0002-2824-0271
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för process- och produktutveckling. (PTW)ORCID-id: 0000-0001-5734-294X
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för automation och datateknik. (PTW)ORCID-id: 0000-0001-5608-8636
Chalmers.
2014 (Engelska)Ingår i: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 25, nr 2, s. 025010-Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

A novel method for converting electromagnetic spectral radiance information into emperature measurements is presented. It allows for varying spectral emissivity of the metallic measurand during the course of the measurement. Such variations are due to e.g. thermal oxidation or temperature dependent emissivity. Based on the assumption that emissivity changes with time and temperature in a continuous manner, it is further assumed that an emissivity estimate at one sample instance can be derived from the estimated emissivity found at the previous samples together with updated spectral information. This leads to successive recalculations of spectral emissivity together with corresponding temperature values. The proposed algorithm has been proven to give accurate temperature estimates from a measurement based on data captured by a standard UV-Vis spectrophotometer even for an oxidizing Ti-6Al-4V specimen in a temperature range between 900K and 1400K. The method however, is not limited to these wavelength- or temperature-ranges.

Ort, förlag, år, upplaga, sidor
2014. Vol. 25, nr 2, s. 025010-
Nyckelord [en]
Emissivity Compensated Spectral Pyrometry
Nationell ämneskategori
Robotteknik och automation
Forskningsämne
TEKNIK, Produktions- och materialteknik
Identifikatorer
URN: urn:nbn:se:hv:diva-5607DOI: 10.1088/0957-0233/25/2/025010ISI: 000332697800010Scopus ID: 2-s2.0-84892898937OAI: oai:DiVA.org:hv-5607DiVA, id: diva2:649429
Anmärkning

Del av lic.  

Tillgänglig från: 2013-09-18 Skapad: 2013-09-18 Senast uppdaterad: 2019-05-10Bibliografiskt granskad
Ingår i avhandling
1. Instrumentation and estimation for high temperature control
Öppna denna publikation i ny flik eller fönster >>Instrumentation and estimation for high temperature control
2013 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Within a variety of industrially relevant high temperature production processes such as welding, heat treatment and metal deposition, the quality of the manufactured component is largely affected by how well parameters can be controlled during processing. These parameters might be, in the case of metal deposition, power input, material feed, or a parameter which is common for all of the aforementioned processes: material temperature. The ability to correctly measure, or in other ways estimate process parameters is vital in order to successfully control high temperature processes such as above 700 degrees Celsius. In this work, instrumentation and estimation solutions adapted to high temperature control are proposed and implemented with a focus on the laser metal wire deposition process. Special attention is given to temperature measurements on specimens with varying emissivity as commonly found in high temperature processes. A calibration procedure for a single-wavelength pyrometer is also presented together with a general discussion on limitations of such a system for measurands with varying emissivity. A new method for non-contact emissivity compensated temperature estimations using a spectrometer is presented. Simulations and industrially relevant experiments have been carried out validating the method. The theoretical framework for the developed method will be further investigated in the future together with additional experimental validation. In addition to temperature measurements, a method for real-time process control of laser metal wire deposition has been developed and implemented with good results. This control scheme estimates and controls the tool-to-workpiece distance based on resistance measurements. Such measurements allow for placement of instruments outside of the processing chamber and easy integration into existing equipment. Future work will be directed towards incorporation of resistance measurements into an iterative learning control scheme. Also, improvement on the resistance-distance model and further investigation into suitable signal processing methods for the resistance signal will be pursued.

Ort, förlag, år, upplaga, sidor
Göteborg: Chalmers Reproservice, 2013. s. 156
Serie
R - Department of Signals and Systems, Chalmers University of Technology, ISSN 1403-266x ; R017
Nyckelord
Additive Manufacturing, Automation, Emissivity, Emissivity Compensated Spectral Pyrometry, Laser Metal Wire Deposition, Metal Deposition, Pyrometry, Resistance Feedback Control, Thermometry, Varying Emissivity
Nationell ämneskategori
Robotteknik och automation
Forskningsämne
TEKNIK, Produktions- och materialteknik; TEKNIK, Fysik
Identifikatorer
urn:nbn:se:hv:diva-5602 (URN)
Presentation
2013-09-25, C118, Högskolan Väst, Trollhättan, 09:25 (Engelska)
Opponent
Handledare
Forskningsfinansiär
EU, FP7, Sjunde ramprogrammet, 266271
Tillgänglig från: 2013-09-25 Skapad: 2013-09-18 Senast uppdaterad: 2016-02-08Bibliografiskt granskad
2. Non-intrusive instrumentation and estimation: Applications for control of an additive manufacturing process
Öppna denna publikation i ny flik eller fönster >>Non-intrusive instrumentation and estimation: Applications for control of an additive manufacturing process
2015 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

For integration of additive manufacturing into industrial production, there is a need for capable yet robust automation solutions. Such solutions are to ensure consistent process outputs, both with regard to deposit geometry and material properties. In this thesis, instrumentation and control solutions have been investigated for the laser metal wire deposition additive manufacturing process. This particular process is promising with regard to e.g. high deposition rates and negligible material waste. However, due to its inherent dynamics, it requires automatic control in order to prove competitive. A large number of process parameters affect the resulting quality of the deposit. Successful control of these parameters is crucial for turning laser metal wire deposition into an industrially tractable process. This requires relevant and reliable process information such as the temperature of the deposit and the positioning of the tool relative to the workpiece. Due to the particular requirements of instrumenting the process, only non-intrusive measurement methods are viable. In this thesis, such measurement solutions are presented that advance automatic control of the laser metal wire deposition. In response to the need for accurate temperature measurements for the process, a new temperature measurement method has been developed. By adopting the novel concept of temporal, rather than spectral, constraints for solving the multispectral pyrometry problem, it opens up for temperature measurements which compensates for e.g. an oxidising deposit. For maintaining a good deposition process in laser metal wire deposition, control of tool position and wire feed rate is required. Based on measurements of resistance through the weld pool, a simple yet well performing control system is presented in this thesis. The control system obtains geometrical input information from resistance measurements made in-situ, and feeds this information to an iterative learning controller. This results in a robust, cheap and practical control solution for laser metal wire deposition, which is suitable for industrial use and that can easily be retrofitted to existing equipment.

Ort, förlag, år, upplaga, sidor
Göteborg: Chalmers University of Technology,, 2015. s. 98
Serie
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie, ISSN 0346-718X ; 3829
Nyckelord
Additive Manufacturing, Automation, Emissivity, Emissivity Compensated Spectral Pyrometry, Laser Metal Wire Deposition, Metal Deposition, Pyrometry, Resistance Feedback Control, Thermometry
Nationell ämneskategori
Bearbetnings-, yt- och fogningsteknik
Forskningsämne
TEKNIK, Produktions- och materialteknik
Identifikatorer
urn:nbn:se:hv:diva-7428 (URN)9789175971483 (ISBN)
Opponent
Handledare
Tillgänglig från: 2015-03-06 Skapad: 2015-03-06 Senast uppdaterad: 2016-02-08Bibliografiskt granskad

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Hagqvist, PetterSikström, FredrikChristiansson, Anna-Karin

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