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Anna-Karin Christiansson

Universitetslektor

Staff member at Division of Production Systems.

Conducts research in engineering and technology, production technology.


Research area/research interest

My research focuses on measurement and control systems for production processes. The purpose is to acquire process understanding and to facilitate model verification and process control through reliable sensors that capture relevant process information. Experimental studies are performed on different manufacturing processes at PTC in cooperation with process expertise with process understanding. The aim of the research is to develop control functions for robust behaviour during varying conditions.

The additive manufacturing process is of special interest. When performing additive manufacturing, completely new components are produced by melting metal wire using welding technology. Layer upon layer of melted wire is deposited until the desired shape is reached.

Teaching/supervision

I am supervising PhD-students in production technology with special interest in issues regarding welding automation.

I have long experience of teaching feedback control and electrical technology in engineering programs.

Keywords

Welding automation, non-contact measurement, feedback control, measurement systems for welding

Publications


3D-Scanning for Weld Distortion Measuring

Published

3D-Scanning for Weld Distortion Measuring

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

A local model for online path corrections in friction stir welding

Published

A local model for online path corrections in friction stir welding

Friction stir welding (FSW) has always been associated with high forces and rigid machines Today’s trends towards joining of more complex structure...

A new Camera Model and Algorithms for higher Accuracy and better Convergence in Vision-based Pose Calculations

Published

A new Camera Model and Algorithms for higher Accuracy and better Convergence in Vision-based Pose Calculations

This paper presents novel strategies for better calibration and pose calculations of a system for determining the pose, i.e. position and...

A new Camera Model for Higher Accuracy Pose Calculations

Published

A new Camera Model for Higher Accuracy Pose Calculations

A position and orientation (pose) measurement system is being developed. The system, called PosEye, is based on a camera and by using the informati...

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

Published

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...

A unified framework for mixed continuous/discrete-time H_infinity -control

Published

A unified framework for mixed continuous/discrete-time H_infinity -control

Accuracy Investigation of a Vision Based System for Pose Measurements

Published

Accuracy Investigation of a Vision Based System for Pose Measurements

The accuracy of a pose measurement system, called PosEye, is investigated. PosEye is a system for real time measurement of the position and...

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

Published

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...

Analysis and evaluation of a general camera model

Published

Analysis and evaluation of a general camera model

A versatile General Camera Model, GCM, has been developed, and is described in detail. The model is general in the sense that it can capture both...

Automatic detection of material phase transitions from spectroscopic data

Published

Automatic detection of material phase transitions from spectroscopic data

When using a temperaturemeasurementmethod which utilizes spectral information for measuring the temperature of varying emissivity measurands, there...

Automatic Generation of Multivariable Sampled-data Controllers for Jet-engines

Published

Automatic Generation of Multivariable Sampled-data Controllers for Jet-engines

In this contribution, it is shown how multivariable sampled-data controllers can be generated for a set of linearized models. The size of this set...

Automatic in-process control of laser metal-wire deposition based on sensor feedback

Published

Automatic in-process control of laser metal-wire deposition based on sensor feedback

This paper describes alasermetaldepositionsystem that isbasedon robotizedlaserwelding andwirefiller material. The system has been found suitable fo...

Automation of a laser welding system for additive manufacturing

Published

Automation of a laser welding system for additive manufacturing

This paper presents the benefits and challenges ofusing a standard robotised laser welding cell for additive manufacturing(AM). Additive...

Automation of a robotised metal deposition system using laser melting of wire

Published

Automation of a robotised metal deposition system using laser melting of wire

This paper presents a system for full automation of free-form-fabrication of fully dense metal structures using robotized laser melting of wire. Th...

Automation of laser metal deposition for the manufacture of fully dense structures

Published

Automation of laser metal deposition for the manufacture of fully dense structures

Automation of Robotized Laser Metal-Wire Deposition

Published

Automation of Robotized Laser Metal-Wire Deposition

Camera Modelling and Calibration - with Applications

Published

Camera Modelling and Calibration - with Applications

Continuous-, discrete- and sampled-data- H∞ˆž control - a unified framework

Published

Continuous-, discrete- and sampled-data- H∞ˆž control - a unified framework

We present a unified and general framework for H∞-control in both continuous time, discrete time and combinations of these. The general result is a...

Control Design for Automation of Robotized Laser Metal-Wire Deposition

Published

Control Design for Automation of Robotized Laser Metal-Wire Deposition

In this paper a novel approach towards automation of robotized laser metal-wire deposition (RLMwD) is described. The RLMwD technique is being...

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

Published

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...

Emissivity compensated spectral pyrometry for varying emissivity metallic measurands

Published

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

Published

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...

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

Published

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...

Experimental validation of an inductive probe for narrow gap measurement based on numerical modelling

Published

Experimental validation of an inductive probe for narrow gap measurement based on numerical modelling

Experimental validation of numeric results for an inductive probe shows that narrow gaps between two plates can be measured with accuracy suitable...

Freeform Fabrication using Laser Metal-wire Deposition

Published

Freeform Fabrication using Laser Metal-wire Deposition

Friction stir welding with robot for light vehicle design

Published

Friction stir welding with robot for light vehicle design

Reducing weight is one of the enablers to design more environmentally friendly vehicles. Friction Stir Welding (FSW) supports low weight design...

Geometry control of laser metal deposition for the manufacture of complex structures in the aero industry

Published

Geometry control of laser metal deposition for the manufacture of complex structures in the aero industry

Height control of laser metal-wire deposition based on iterative learning control and 3D scanning

Published

Height control of laser metal-wire deposition based on iterative learning control and 3D scanning

Laser Metal-wire Deposition is an additive manufacturing technique for solid freeform fabrication of fully dense metal structures. The technique is...

Increased stability in laser metal wire deposition through feedback from optical measurements

Published

Increased stability in laser metal wire deposition through feedback from optical measurements

Robotized laser metal-wire deposition is a fairly new technique being developed at University West in cooperation with Swedish industry for solid...

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

Published

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...

Investigation of effects from realistic influences on inductive gap measurement

Published

Investigation of effects from realistic influences on inductive gap measurement

The influence of deviations from ideal square butt joint conditions is investigated for an improved inductive gap measurement method. Varying plate...

Investigation of path compensation methods for robotic friction stir welding

Published

Investigation of path compensation methods for robotic friction stir welding

Purpose – Friction stir welding (FSW) is a novel method for joining materials without using consumables and without melting the materials. The...

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

Published

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...

Low order sampled data H∞ control using the delta operator and LMIs

Published

Low order sampled data H∞ control using the delta operator and LMIs

A procedure for H ∞ optimization of low order controllers for discrete-time and sampled-data systems is presented in this paper. Generally, low...

Low order sampled-data H∞ control

Published

Low order sampled-data H∞ control

A method for obtaining low order sampled-data H∞ controllers is presented. The method is mainly based on a parametric static feedback controller fo...

Mixed continuous/discrete-time output feedback H∞ control : A unified approach

Published

Mixed continuous/discrete-time output feedback H∞ control : A unified approach

A Riccati equation (RE) based solution to the H∞ optimal control problem for mixed continuous/discrete-time systems is presented. The results unify...

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

Published

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...

Model order reduction methods applied to a welding model

Published

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...

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

Published

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

Modelling and Simulation for Feedback Control of Welding

Published

Modelling and Simulation for Feedback Control of Welding

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

Published

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...

Off-Line Simulation of Advanced Stereo Vision Welding Applications

Published

Off-Line Simulation of Advanced Stereo Vision Welding Applications

Resistance based iterative learning control of additive manufacturing with wire

Published

Resistance based iterative learning control of additive manufacturing with wire

This paper presents successful feed forward control of additive manufacturing of fully dense metallic components. The study is a refinement of form...

Resistance measurements for control of laser metal wire deposition

Published

Resistance measurements for control of laser metal wire deposition

A method for controlling robotized laser metal wire deposition online by electrical resistance metering is proposed. The concept of measuring the...

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

Published

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...

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

Published

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...

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

Published

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

Sampled-data H∞ˆž-control for time-varying hybrid systems

Published

Sampled-data H∞ˆž-control for time-varying hybrid systems

This paper presents sampled-data H∞ˆž-control of linear mixed continuous-time and discrete-time systems, including a mix of continuous-time and...

Sensor and control system for metal deposition using robotised laser welding.

Published

Sensor and control system for metal deposition using robotised laser welding.

Simulated Feedback Control of Metal Fusion Welding

Published

Simulated Feedback Control of Metal Fusion Welding

Research projects