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- Alhusin Alkhdur, Abdullah, 1980-
(författare)
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Toward a Sustainable Human-Robot Collaborative Production Environment
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This PhD study aimed to address the sustainability issues of the robotic systems from the environmental and social aspects. During the research, three approaches were developed: the first one an online programming-free model-driven system that utilises web-based distributed human-robot collaboration architecture to perform distant assembly operations. It uses a robot-mounted camera to capture the silhouettes of the components from different angles. Then the system analyses those silhouettes and constructs the corresponding 3D models.Using the 3D models together with the model of a robotic assembly cell, the system guides a distant human operator to assemble the real components in the actual robotic cell. To satisfy the safety aspect of the human-robot collaboration, a second approach has been developed for effective online collision avoidance in an augmented environment, where virtual three-dimensional (3D) models of robots and real images of human operators from depth cameras are used for monitoring and collision detection. A prototype system is developed and linked to industrial robot controllers for adaptive robot control, without the need of programming by the operators. The result of collision detection reveals four safety strategies: the system can alert an operator, stop a robot, move away the robot, or modify the robot’s trajectory away from an approaching operator. These strategies can be activated based on the operator’s location with respect to the robot. The case study of the research further discusses the possibility of implementing the developed method in realistic applications, for example, collaboration between robots and humans in an assembly line.To tackle the energy aspect of the sustainability for the human-robot production environment, a third approach has been developed which aims to minimise the robot energy consumption during assembly. Given a trajectory and based on the inverse kinematics and dynamics of a robot, a set of attainable configurations for the robot can be determined, perused by calculating the suitable forces and torques on the joints and links of the robot. The energy consumption is then calculated for each configuration and based on the assigned trajectory. The ones with the lowest energy consumption are selected.
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| 2. |
- Ratanathavorn, Wallop
(författare)
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Dissimilar joining of aluminium to ultra-high strength steels by friction stir welding
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Multi-material structures are increasingly used in vehicle bodies to reduce weight of cars. The use of these lightweight structures is driven by requirements to improve fuel economy and reduce CO2 emissions. The automotive industry has replaced conventional steel components by lighter metals such as aluminium alloy. This is done together with cutting weight of structures using more advanced strength steels. However, sound joining is still difficult to achieve due to differences in chemical and thermal properties. This research aims to develop a new innovative welding technique for joining aluminium alloy to ultra-high strength steels. The technique is based on friction stir welding process while the non-consumable tool is made of an ordinary tool steel. Welding was done by penetrating the rotating tool from the aluminium side without penetrating into the steel surface. One grade of Al-Mg aluminium alloy was welded to ultra-high strength steels under lap joint configuration. Different types of steel surface coatings including uncoated, hot-dipped galvanised and electrogalvanised coating have been studied in order to investigate the influence of zinc on the joint properties. The correlation among welding parameters, microstructures, intermetallic formation and mechanical properties are demonstrated in this thesis. Results have shown that friction stir welding can deliver fully strong joints between aluminium alloy and ultra-high strength steels. Two intermetallic phases, Al5Fe2 and Al13Fe4, were formed at the interface of Al to Fe regardless of surface coating conditions. The presence of zinc can improve joint strength especially at low heat input welding due to an increased atomic bonding at Al-Fe interface. The formation of intermetallic phases as well as their characteristics has been demonstrated in this thesis. The proposed welding mechanisms are given based on metallography investigations and related literature.
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