Morten Kristiansen

Aalborg University · Department of Materials and Production

In this paper, we investigate the problem of scheduling a 6 DOF robotic arm to carry out a sequence of spray painting tasks. The duration of any given painting task is process dependent and fixed, but the duration of an “intertask”, corresponding to the process of relocating and reorienting the robot arm from one painting task to the next one, is i...

Edge effects in laser forming influence the possible tolerances that can be achieved with laser forming. Edge effects arise due to uneven temperature profiles along the laser scan line. It has been suggested that an increased cooling rate can minimize the occurrence of edge effects. This work will examine the effect of increased cooling to reduce e...

The quality of robotic laser welded parts is related to the joint location, the trajectory of the laser focal point and the process parameters. By performing in-process monitoring, it is possible to acquire sufficient process knowledge for post-inspection to evaluate the geometrical weld quality. The existing solutions for such systems operate alon...

Laser forming is a process capable of bending sheet metal only with the laser beam and without a physical interaction with the part. The part is formed by small and local deformations by the laser beam and it is done in increments with each pass of the laser. This incremental forming makes it difficult to ensure a smooth deformation field, which ca...

Galvanometric laser scanner (GLS) systems are widely used for materials processing due to their high precision, processing velocity, and repeatability. However, GLS systems generally suffer from scan field distortions due to joint and task space relationship errors. The problem is further pronounced in robotic applications, where the GLS systems ar...

Offshore foundations are subject to fatigue due to wind and wave loads during their lifetime. Post-weld treatment is a group of techniques well known to improve the fatigue life. This study investigates how this is applicable for large structures, i.e. a 2.4 meter jacket T-node. A large scale empirical study was performed and results were obtained...

High-frequency mechanical impact (HFMI) treatment is a well-documented post-weld treatment to improve the fatigue life of welds. Treatment of the weld toe must be performed by a skilled operator due to the curved and inconsistent nature of the weld toe to ensure an acceptable quality. However, the process is characterised by noise and vibrations; h...

Laser forming is a contactless thermal forming process that can be applied for both single and double-curved geometries. When it comes to prototyping and small batch production, laser forming has the potential to compete with conventional sheet-metal forming processes; however, an investigation of the relationship between process parameters, hardne...

Laser marking is a non-contact technique, which achieves colouring by using a laser beam to increase surface oxidation. Controlling the amount of heat induced into the part is essential in ensuring the desired degree of oxidisation. However, the induced heat is not only dependent on the process parameters, but also on the surface absorption, which...

High-frequency mechanical impact (HFMI) treatment is a well-documented post-weld treatment to improve the fatigue life of welds. Treatment of the weld toe must be performed by a skilled operator due to the curved and inconsistent nature of the weld toe to ensure an acceptable quality. However, the process is characterised by noise and vibrations; h...

Grain refinement and the avoidance of columnar solidification is a great challenge in the deep penetration laser welds of thick-section steels. Further knowledge about the heat distribution and the temperature gradients in laser welds is vital for future attempts on the grain refinement of such welds. In this study, a comparative investigation was...

This paper presents a novel solution for precision draping of prepreg composite fabrics onto double curved molds. Our contributions relate to system design, including hardware and software components, and to system integration. On the hardware side, design and implementation of a drape tool with up to 120 suction cups positioned individually by lin...

The laser forming process is characterized by high temperature gradients and localized deformation. The process uses a laser to introduce thermal strains. The localized deformation along with the high temperature gradients is introduced iteratively which creates a complex and dynamic forming process. To understand the dynamic behavior of the proces...

Laser forming is a non-contact forming method. By control of different process parameters, different forming mechanisms can be achieved. The forming mechanisms allows for bending, compression and buckling. Process control to ensure correct combination and usage of each forming mechanism is still an open issue. Present work is an attempt to implemen...

This paper presents “Autonomous Industrial Mobile Manipulation” (AIMM) as a research topic and emerging technology for modern industry. The motivation for this work is that the underlying concepts and required technologies exist; now it is time to put the AIMM technology to the test in real-world industrial environments. The context for AIMM is mob...

Full and partial penetration welding using high power lasers exhibit different melt pool geometries. The main difference is that full penetration welds tend to widen at the root side. In recent years, full penetration laser welding has been modeled using sophisticated multiphase numerical models. However, less computationally-complex thermo-mechani...

The mechanical system used for remote laser processing can contain as much as 9 degrees of freedom (DOF). In this paper, a sample based motion planning algorithm for such remote laser processing equipment is presented. By construction robot configurations through a sampling strategy redundancy is inherently taken into account and the path is ensure...

This paper presents a framework for task sequencing of redundant remote laser processing equipment. The task sequencing algorithm is based on generating sets of robot configuration samples on all processing contours. The sequencing is done by using a solver for the equality constrained generalized traveling salesman problem (E- GTSP) to find the sh...

It has previously been shown that the stability of the remote fusion cutting (RFC) process can be increased by modifying the intensity profile of the laser by means of a diffractive optical element (DOE). This paper investigates the quality of remote DOE cutting (RDC) conducted with a 3kW single mode fiber laser in 0.5mm stainless steel. An automat...

The manufacturing of large steel structures involves welding thick-section steels. Using hybrid laser welding, it is possible to reduce production costs significantly. However, avoiding solidification cracks in the weld is difficult when welding thick-section steels. In this study, a number of experiments were performed on the hybrid laser welding...

In a current laser welding production process of components of stainless steel, a butt joint configuration may lead to failures in the form of blowouts, causing an unacceptable welding quality. A study to improve the laser welding process was performed with the aim of solving the problem by designing a suitable pattern of multiple small laser spots...

Laser forming of sheet metal has the potential to add to the growing repertoire of laser processing. This is of particular interest for flexible manufacturing and rapid prototyping. A factor limiting the practical use is the planning of the process parameters, such as laser scan path, laser power, laser scan speed, laser spot size, dwell time, etc....

To reduce the costs of the fabrication of offshore wind turbine foundations it is necessary to investigate new fabrication technologies. Hybrid laser arc welding is a potentially well-suited process for this because it requires less groove preparation to achieve deep weld penetration and lower heat input, compared to traditional arc welding. A skir...

Laser keyhole welding is widely used in industry due to its large welding depth and low heat input. For some industrial cases it is necessary to widen the beam to cover the joint configuration, which instead results in a lower intensity and surface conduction welds. The introduction of the high-power single mode fiber laser makes it possible to dea...

Hybrid laser-arc welding of thick-section steel requires high power lasers, appropriate process parameters, and alternative techniques for obtaining deeper penetration. Conventional techniques for increasing penetration/efficiency include groove beveling, preheating, and the use of pre-set gap, but they are costly and inconvenient. Therefore, inves...

When considering remote laser cutting, the literature often discusses two methods: remote fusion cutting (RFC) and remote ablation cutting. It has previously been hypothesised that remote cutting can be conducted by modifying the intensity profile of the laser beam by means of a diffractive optical element. In this study, the effect of travel speed...

The set of incident angles, that yields stable cuts when conducting remote fusion cutting (RFC), is of great importance when scheduling multiple cuts on a work piece. This is due to their ability to determine how much the laser beam can be moved by angling the cutting head instead of translating it. This paper investigates how the stability of the...

Remote fusion cutting (RFC) is an interesting industrial process compared to traditional laser cutting. It is because traditional laser cutting is limiting travel speed and accessibility due to the required positioning of the cutting head just above the workpiece for providing a cutting gas pressure. For RFC this pressure is created by the vapor, w...

From an industrial point of view, in a laser cutting-welding production chain, it is of great importance to know the influence of the attainable laser cut quality on the subsequent hybrid laser arc welding process. Many studies have been carried out in the literature to obtain lower surface roughness values on the laser cut edge. However, in practi...

The introduction of high-power single mode fiber lasers has given deeper and narrower welds than previously seen using lasers. In some cases, the weld becomes too narrow and must be expanded to fit the geometrical shape of a given welding task. Instead of using only one beam, it was suggested to split the beam into multiple spots placed in a prespe...

The introduction of high power single mode fiber lasers has given deeper and narrower laser welds than seen previously. In some cases the weld becomes too narrow and must be expanded to fit the geometrical shape of a given weld task. It was suggested that instead of using only one beam, the beam was split into multiple beams placed in a pre-specifi...

This paper describes a new flexible and fast approach to laser cutting called ROBOCUT. Combined with CAD/CAM technology, laser cutting of metal provides the flexibility to perform one-of-a-kind cutting and hereby realises mass production of customised products. Today’s laser cutting techniques possess, despite their wide use in industry, limitation...

To analyse advanced high power beam patterns, a method, which is capable of analysing the intensity distribution in 3D is needed. Further a measuring of scattered light in the same system is preferred. This requires a high signal to noise ratio. Such a system can be realised by a CCD-chip implemented in a camera system. Most available CCD-based sys...

This paper investigates the application potential for the technology-push manufacturing technology (TPMT) autonomous industrial mobile manipulation (AIMM), in order to link the conceptual ideas (academia) to actual manufacturing requirements (industry). The approach is based on the proposed TPMT methodology in a comprehensive industrial case study....

At the moment autonomous industrial mobile manipulation (AIMM) is a subject of major focus in development and research environments, as it is a technology with significant potential. However, we are experiencing a lack in calibration techniques, in order to obtain industrially acceptable localization and manipulation tolerances. In this paper two c...

Increased customer needs and intensified global competition require intelligent and flexible automation. The interaction technology mobile robotics addresses this, so it holds great potential within the industry. This paper presents the concepts, ideas and working principles of the mobile robot "Little Helper" - an ongoing research project at Aalbo...

Increased customer needs and intensified global competition require intelligent and flexible automation. The interaction technology mobile robotics addresses this, so it holds great potential within the industry. This paper presents the concepts, ideas and working principles of the mobile robot "Little Helper" - an ongoing research project at Aalbo...

One of the important quality issues to incorporate in development of automatic paint planning systems for robotised painting is knowledge about paint sag. Sagging can occur when a wet paint coat is applied to an inclined surface. The coat is forced by the gravitational force to flow on the surface under its own weight and the cohesive force is cont...

Knowledge acquisition of operator knowledge is mainly a silent knowledge source and it is rarely used for producing models of industrial processes, named process models. An example of a model made from operator knowledge is fuzzy logic. In the presented work methodologies to formalise and make use of acquired operator knowledge are developed and pr...

When the robots are used in the industry to perform some of the jobs and their programs are generated automatically, it is necessary to make scheduling of their tasks. This problem is new for the automated painting process, where the number of tasks often contains 100-200 paint strokes. This paper deals with two big issues when scheduling paint str...

When applying conventional industrial robots to high speed manufacturing operations, a compromise always has to be made between accuracy and speed. In many manufacturing applications it is very difficult as well as time consuming to find a good compromise. This makes it difficult to use conventional robots for high speed operations. In this paper a...

A process-planning model has been developed for welding of T-joints. The model has been used for computing control variables on a T-joint with varying root gap. This research investigates how different sources of knowledge can be produced, acquired, integrated and formalised in process-planning models. The knowledge sources investigated are empiric...

Automation of many manufacturing processes requires a process-planning model. These models are hard and time consuming to construct because they are often non-linear and the physics of the process is not completely understood. In the literature these models are usually constructed from experiments. However, the operator possesses a lot of knowledge...

With the advance in IT technology sensors and processing power exist to achieve fully automated robot programming in industrial tasks. This paper reports on the EU-project FlexPaint, which devised a methodology to automatically generate robot programs for spray painting of unknown parts. The solution uses four steps: laser triangulation sensing, ge...