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Emissivity compensated spectral pyrometry: algorithm and sensitivity analysis
University West, Department of Engineering Science, Division of Automation and Computer Engineering. (PTW)ORCID iD: 0000-0002-2824-0271
University West, Department of Engineering Science, Division of Process and Product Development. (PTW)ORCID iD: 0000-0001-5734-294X
University West, Department of Engineering Science, Division of Automation and Computer Engineering. (PTW)ORCID iD: 0000-0001-5608-8636
Chalmers.
2014 (English)In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 25, no 2, 025011- p.Article in journal (Refereed) Published
Abstract [en]

In order to solve the problem of non-contact temperature measurements on an object with varying emissivity, a new method is herein described and evaluated. The method uses spectral radiance measurements and converts them to temperature readings. It proves to be resilient towards changes in spectral emissivity and tolerates noisy spectral measurements. It is based on an assumption of continuous changes in emissivity and uses historical values of spectral emissivity and temperature for estimating current spectral emissivity.

The algorithm, its constituent steps and accompanying parameters are described and discussed. A thorough sensitivity analysis of the method is carried out through simulations. No rigorous instrument calibration is needed for the presented method and is therefore industrially tractable.

Place, publisher, year, edition, pages
Bristol: IOP , 2014. Vol. 25, no 2, 025011- p.
Keyword [en]
Spectral pyrometry
National Category
Robotics
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
URN: urn:nbn:se:hv:diva-5608DOI: 10.1088/0957-0233/25/2/025011ISI: 000332697800010Scopus ID: 2-s2.0-84892836708OAI: oai:DiVA.org:hv-5608DiVA: diva2:649434
Available from: 2013-09-18 Created: 2013-09-18 Last updated: 2016-02-08Bibliographically approved
In thesis
1. Instrumentation and estimation for high temperature control
Open this publication in new window or tab >>Instrumentation and estimation for high temperature control
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
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.

Place, publisher, year, edition, pages
Göteborg: Chalmers Reproservice, 2013. 156 p.
Series
R - Department of Signals and Systems, Chalmers University of Technology, ISSN 1403-266x ; R017
Keyword
Additive Manufacturing, Automation, Emissivity, Emissivity Compensated Spectral Pyrometry, Laser Metal Wire Deposition, Metal Deposition, Pyrometry, Resistance Feedback Control, Thermometry, Varying Emissivity
National Category
Robotics
Research subject
ENGINEERING, Manufacturing and materials engineering; ENGINEERING, Physics
Identifiers
urn:nbn:se:hv:diva-5602 (URN)
Presentation
2013-09-25, C118, Högskolan Väst, Trollhättan, 09:25 (English)
Opponent
Supervisors
Funder
EU, FP7, Seventh Framework Programme, 266271
Available from: 2013-09-25 Created: 2013-09-18 Last updated: 2016-02-08Bibliographically approved
2. Non-intrusive instrumentation and estimation: Applications for control of an additive manufacturing process
Open this publication in new window or tab >>Non-intrusive instrumentation and estimation: Applications for control of an additive manufacturing process
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
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.

Place, publisher, year, edition, pages
Göteborg: Chalmers University of Technology,, 2015. 98 p.
Series
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie, ISSN 0346-718X ; 3829
Keyword
Additive Manufacturing, Automation, Emissivity, Emissivity Compensated Spectral Pyrometry, Laser Metal Wire Deposition, Metal Deposition, Pyrometry, Resistance Feedback Control, Thermometry
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-7428 (URN)9789175971483 (ISBN)
Opponent
Supervisors
Available from: 2015-03-06 Created: 2015-03-06 Last updated: 2016-02-08Bibliographically approved

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