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Fredrik Sikström

Universitetslektor

Anställd på Avdelningen för produktionssystem.

Forskar inom området teknik, elektroteknik och elektronik, produktionsteknik.


Forskningsområde/forskningsintresse

Mitt forskningsområde är automation med speciell inriktning mot reglerteknik och processövervakning av svetsprocesser.

Undervisning/handledning

Jag undervisar maskin- och elkraftsingenjörer i reglerteknik samt maskiningenjörer i automatiseringsteknik. Jag handleder doktorander som biträdande handledare samt examinerar examensarbeten på kandidat och magisternivå.

Nyckelord

Svetsautomation, svetsövervakning, reglerteknik, systemidentifiering modellering.


Publikationer


A study on change point detection methods applied to beam offset detection in laser welding

Publicerat

A study on change point detection methods applied to beam offset detection in laser welding

This paper presents an experimental study where a photodiode integrated into a laser beam welding tool is used to monitor laser beam spot deviation...

Adaptive control of the filler wire rate during laser beam welding of squared butt joints with varying gap width

Publicerat

Adaptive control of the filler wire rate during laser beam welding of squared butt joints with varying gap width

Adding filler wire control to autogenous laser beam welding of squared butt joints offers a means to widen up the tight fit-up tolerances associate...

Beam offset detection in laser stake welding of tee joints based on photodetector sensing

Publicerat

Beam offset detection in laser stake welding of tee joints based on photodetector sensing

This paper presents an experimental study where a photodetector is used in a laser beam welding tool to monitor beam deviations (beam offsets) in...

Detecting beam offsets in laser welding of closed-square-butt joints by wavelet analysis of an optical process signal

Publicerat

Detecting beam offsets in laser welding of closed-square-butt joints by wavelet analysis of an optical process signal

Robotized laser beam welding of closed-square-butt joints is sensitive to the positioning of the laser beam with respect to the joint since even a...

Robust vision-based joint tracking for laser welding of curved closed-square-butt joints

Publicerat

Robust vision-based joint tracking for laser welding of curved closed-square-butt joints

Robotized laser beam welding of closed-square-butt joints is sensitive to how the focused laser beam is positioned in relation to the joint, and...

Vision based beam offset detection in laser stake welding of T-joints using a neural network

Publicerat

Vision based beam offset detection in laser stake welding of T-joints using a neural network

This paper presents an experimental study where a vision camera integrates coaxially into a laser beam welding tool to monitor beam deviations (bea...

In-process Monitoring and Control of Robotized Laser Beam Welding of Closed Square Butt Joints

Publicerat

In-process Monitoring and Control of Robotized Laser Beam Welding of Closed Square Butt Joints

In robotized laser welding of technical zero gap closed square butt joints it is critical to position the laser beam correct with regardsto the...

Spectroscopic monitoring of laser blown powder directed energy deposition of Alloy 718

Publicerat

Spectroscopic monitoring of laser blown powder directed energy deposition of Alloy 718

Experimental explorations of a spectrometer system used for in-process monitoring of the laser blown powder directed energy deposition of Alloy 718...

Barriers for industrial implementation of in-process monitoring of weld penetration for quality control

Publicerat

Barriers for industrial implementation of in-process monitoring of weld penetration for quality control

The research conducted sheds a light on the question why robust in-process monitoring and adaptive control are not fully implemented in the welding...

Monitoring of Varying Joint Gap Width During Laser Beam Welding by a Dual Vision and Spectroscopic Sensing System

Publicerat

Monitoring of Varying Joint Gap Width During Laser Beam Welding by a Dual Vision and Spectroscopic Sensing System

A vision and spectroscopic system for estimation of the joint gap width in autogenous laser beam butt welding is presented. Variations in joint gap...

Prediction of penetration in one-sided fillet welds by in-process joint gap monitoring : an experimental study

Publicerat

Prediction of penetration in one-sided fillet welds by in-process joint gap monitoring : an experimental study

The challenge to predict variations in penetration depth in one-sided fillet welds during robotized gas metal arc welding has been addressed by a...

Vision and spectroscopic sensing for joint tracing in narrow gap laser butt welding

Publicerat

Vision and spectroscopic sensing for joint tracing in narrow gap laser butt welding

The automated laser beam butt welding process is sensitive to positioning the laser beam with respect to the joint because a small offset may resul...

Evaluation of non-contact methods for joint tracking in a laser beam welding application

Publicerat

Evaluation of non-contact methods for joint tracking in a laser beam welding application

The use of automated laser welding is a key enabler for resource efficient manufacturing in several industrial sectors. One disadvantage with laser...

Joint tracking in zero gap laser beam welding using a vision sensor

Publicerat

Joint tracking in zero gap laser beam welding using a vision sensor

The paper describes a robust vision sensor system that can find very narrow gaps between metal sheets to be butt welded together. The use of...

Model based feedback control of gas tungsten arc welding : An experimental study

Publicerat

Model based feedback control of gas tungsten arc welding : An experimental study

In order to obtain high structural integrity and joint performance in welding a transient heat conduction model has been utilized to design a model...

Monitoring of laser beam welding by a non-intrusive optical sensor system using photodiodes

Publicerat

Monitoring of laser beam welding by a non-intrusive optical sensor system using photodiodes

Monitoring and control of automated laser beam welding is necessary in order to increase weld quality and to optimise the process. This paper...

Operator bias in the estimation of arc efficiency in gas tungsten arc welding

Publicerat

Operator bias in the estimation of arc efficiency in gas tungsten arc welding

In this paper the operator bias in the measurement process of arc efficiency in stationary direct current electrode negative gas tungsten arc weldi...

Vision systems for in‐process monitoring of laser beam welding

Publicerat

Vision systems for in‐process monitoring of laser beam welding

This paper addresses the issue of evaluating an optical vision system to be integrated with a 1μm laser beam welding tool for process monitoring. T...

Emissivity compensated spectral pyrometry for varying emissivity metallic measurands

Publicerat

Emissivity compensated spectral pyrometry for varying emissivity metallic measurands

A novel method for converting electromagnetic spectral radiance information into emperature measurements is presented. It allows for varying spectr...

Emissivity compensated spectral pyrometry-algorithm and sensitivity analysis

Publicerat

Emissivity compensated spectral pyrometry-algorithm and sensitivity analysis

In order to solve the problem of non-contact temperature measurements on an object with varying emissivity, a new method is herein described and...

Optical Methods for In-Process Monitoring of Laser Beam Welding

Publicerat

Optical Methods for In-Process Monitoring of Laser Beam Welding

This paper addresses the issue of evaluating and selecting optical sensors to be integrated with a 1μm laser beam welding system. The method used f...

Emissivity estimation for high temperature radiation pyrometry on Ti–6Al–4V

Publicerat

Emissivity estimation for high temperature radiation pyrometry on Ti–6Al–4V

The paper demonstrates a versatile procedure suitable for industrial implementation of temperature measurement on a hot titanium alloy. The driving...

Heat input and temperatures in welding

Publicerat

Heat input and temperatures in welding

A key feature in welding is the energy supplied, in order to join the work pieces together. For all fusion welding methods, the supplied energy is ...

Operator influence on the estimation of arc efficiency in gas tungsten arc welding

Publicerat

Operator influence on the estimation of arc efficiency in gas tungsten arc welding

In this paper the operator bias in the measurement process of arc efficiency in stationary direct current electrode negative gas tungsten arc weldi...

Model order reduction methods applied to a welding model

Publicerat

Model order reduction methods applied to a welding model

A  finite element representation modelling transient heat conduction of gas tungsten arc welding of stainless steel is used to evaluate different...

Role of fixture forces on distortion in gas tungsten arc welding : An experimental and modelling approach

Publicerat

Role of fixture forces on distortion in gas tungsten arc welding : An experimental and modelling approach

Simulation and experiments show that the fixture clamping force has a significant influence on the structural integrity of a welded workpiece. This...

Modeling and simulation aspects of feedback control in gas tungsten arc welding : An experimental study

Publicerat

Modeling and simulation aspects of feedback control in gas tungsten arc welding : An experimental study

Modeling and simulation for welding automation

Publicerat

Modeling and simulation for welding automation

Sampled-data H∞ control applied to the choice of controller order and sampling rate

Publicerat

Sampled-data H∞ control applied to the choice of controller order and sampling rate

Integration of finite element analysis and computer aided robotics for advanced programming of robotized welding

Publicerat

Integration of finite element analysis and computer aided robotics for advanced programming of robotized welding

This paper describes a promising approach where finite element analysis is combined with computer aided robotics in off-line programming of advance...

Simulation-based feedback control of welding processes

Publicerat

Simulation-based feedback control of welding processes

Fusion welding for joining of metals is an important manufacturing process widely used in industry, and very appreciated for its usefulness. This...

Tools for simulation based fixture design to reduce deformation in advanced fusion welding

Publicerat

Tools for simulation based fixture design to reduce deformation in advanced fusion welding

The traditional fusion welding and fixture simulations are performed using advanced finite element simulation tools, commonly used are e.g. MSC.Mar...

Modelling and Simulation for Feedback Control of Welding

Publicerat

Modelling and Simulation for Feedback Control of Welding

Simulated Feedback Control of Metal Fusion Welding

Publicerat

Simulated Feedback Control of Metal Fusion Welding

Simulation for Design of Automated Welding

Publicerat

Simulation for Design of Automated Welding

This paper describes a promising approach where simulations were used in the design of real-time control for automated welding. A finite element...

3D-Scanning for Weld Distortion Measuring

Publicerat

3D-Scanning for Weld Distortion Measuring

Optical three dimensional scanning for weld distortion measurements have been performed for validation, inspection, general visualization and...

Optimering av effektreglering till kedjeslipverk vid Wargöns bruk

Publicerat

Optimering av effektreglering till kedjeslipverk vid Wargöns bruk

Improved fatigue properties of welded box beams by tailored welding procedures for high penetration fillet welds

Publicerat

Improved fatigue properties of welded box beams by tailored welding procedures for high penetration fillet welds

Forskningsprojekt