Adhesive Bonding of an Aluminum Alloy with and without an Oxide Layer in Atmospheres with Different Oxygen Contents

Aluminum surfaces in a normal atmosphere are always coated with a native oxide layer. To prevent a new layer from forming after this oxide layer has been removed, an environment without oxygen must be created. This work uses a new method of doping an inert gas atmosphere with highly reactive silane to ensure technical freedom from oxygen. The influence of the surrounding atmosphere and the influence of the oxide layer on the tensile strength of an aluminum-aluminum joint are investigated. For this purpose, 2-component adhesives are used whose curing mechanisms are fundamentally not based on the reaction with the surrounding atmosphere. The tests are carried out in normal, pure argon, and an oxygen-free argon/silane atmosphere. The experiments show that the surrounding atmosphere influences the strength of the bonded joint. Compared to the oxidized surfaces, the joints of the deoxidized surfaces show a higher tensile strength under constant ambient conditions

Research on Gentle Loosening of Solidified Bolted Joints for Complex Capital Goods

The consideration of sustainability is increasingly becoming a focus in research and production. For example, the recycling process for products that are no longer usable should be optimally prepared by separating materials by type as far as possible. In addition, products should be made usable again by repair or replacement if only sub-components fail. In the case of complex capital goods, like aircraft engines, it is mandatory to preserve the product since damage to the joining partners can lead to immense costs. A decisive factor in this context are assembly connections, which have a major influence on the complexity of disassembly. Concerning this matter, detachable connections, like screwed joints, have many advantages for service, repair and recycling compared with permanent fixing solutions. They can reduce assembly time, simplify maintenance processes, and greatly reduce maintenance time and costs. However, during a product's life cycle, threaded connections can corrode, leading to damage or even failure of the bolted joints. Beyond that, they can solidify and often only be disassembled destructively. In this article, we present an approach to improve the loosening of operational solidified screwed connections. It is well known that vibrations during operation can reduce the preload force of the connections. We exploit this aspect by inducing vibrations through micro impacts to alleviate the loosening torque of the solidified bolted connection. Depending on the direction of the vibration (torsional or axial), that can ensure a gentle and component-friendly disassembly to a greater or lesser extent in contrast to destroying the screw by drilling or shearing and splitting with the risk of damaging the product being maintained. The designed experimental setup with a piezo actuator allows us to investigate the amplitude and frequency of the induced vibrations for the required disassembly force. The results show that our approach enables component-conserving disassembly, as the forces can be significantly reduced

Aerodynamic Feeding 4.0: A New Concept for Flexible Part Feeding

In modern production environments, the need for flexible handling systems constantly increases due to increasing uncertainties, shorter product life cycles and higher cost pressure. Part feeding systems are vital to modern handling systems, but conventional solutions are often characterized by low flexibility, high retooling times, and complex design. Therefore, in previous research, multiple approaches towards aerodynamic feeding technology were developed. Using air instead of mechanical chicanes to manipulate workpieces, aerodynamic feeding systems can achieve high feeding rates while at the same time being very flexible and reliable. Still, the complexity of the workpieces that can be oriented relies on the number of aerodynamic actuators used in the system. Previously developed systems either used one nozzle with a constant air jet or one nozzle and an air cushion, allowing a maximum of two orientation changes. This work presents a new concept for an aerodynamic feeding system with higher flexibility (with regard to the workpiece geometry) and drastically reduced retooling times compared to conventional feeding systems. In contrast to previous implementations of aerodynamic feeding systems, using only one air nozzle or an air cushion, the new concept uses multiple, individually controllable air nozzles. Using a simulation-based approach, the orientation process is divided into several basic rotations - from a random initial orientation to the desired end orientation - each performed by a distinct nozzle. An optimization algorithm is then used to determine an optimal layout of the air nozzles, enabling the feeding system to feed any desired workpiece, regardless of the initial orientation. With the proposed concept, high flexibility, low retooling times and relatively low costs are expected, setting up aerodynamic feeding as an enabler for changeable production environments

Combined Structural and Dimensional Synthesis of a Parallel Robot for Cryogenic Handling Tasks

The combined structural and dimensional synthesis is a tool for finding the robot structure that is suited best for a given task by means of global optimization. The handling task in cryogenic environments gives strong constraints on the robot synthesis, which are translated by an engineering design step into the combined synthesis algorithm. This allows to reduce the effort of the combined synthesis, which provides concepts for alternative robot designs and indications on how to modify the existing design prototype, a linear Delta robot with flexure hinges. Promising design candidates are the 3PRRU and 3PRUR, which outperform the linear Delta (3PUU) regarding necessary actuator force

Battery system development - Assembly planning between lightweight design and high volume production

Battery systems of electric vehicles suffer from low energy densities as well as high masses and geometrical complexity. The absence of standards for battery cells and peripheral components in combination with large and distributed design spaces within passenger vehicles open up innumerable possibilities to design battery systems. The results are product specific and uneconomical assembly systems. This paper describes the work of the TU Braunschweig to create a methodology that generates and evaluates modular and easy to assemble battery systems based upon user requirements. This methodology gathers and links requirements between the priorities "lightweight design" and "high volume production" including a partly automated generation of CAD data. The generated concepts are directly used for assembly planning. The presented methodology therefore represents a simultaneous engineering approach that shortens development time and supports design engineers as well as process planners

Simulation and Design of an Orientation Mechanism for Assembly Systems

The article focuses on methods for designing modular cable-driven orientation mechanisms that can be attached to robot systems that lack on rotational degrees of freedom. The approach yields assembly systems for high speed handling applications by reducing moving masses. For this purpose, a classification of feasible kinematic structures are given and resulting characteristics, like the orientation workspace, dexterity or its homogeneity, are analyzed. The mechanical design of a first prototype is subsequently presented along with a universal simulation tool for determining task-adapted powertrains using cables. Finally, results of first tests and possibilities for future developments are presented. © 2016 The Authors

A Comparison of Different Approaches for Formation Control of Nonholonomic Mobile Robots regarding Object Transport

Controlling the formation of several mobile robots allows for the connection of these robots to a large virtual unit. This enables a group of mobile robots to carry out tasks that a single robot could not perform. For this purpose, the use of nonholonomic mobile robots is especially useful, as they often have a higher payload and are suitable for a wider range of terrains. However, most research in the area of formation control is focused on holonomic robots, since their superior mobility allows for better control and allows for the research on more sophisticated control techniques. The remaining articles explicitly dealing with nonholonomic robots often do cover common controllers, but do not include realistic simulations or comparison of different controls on the same trajectory. Therefore, in this paper, we present a comparative analysis of two frequently used control approaches. We compare the behavior of a l-?-controller and a Cartesian reference-based controller with different types of reference value generation and pose determination. The evaluation of all resulting control schemes is based on the task of collaborative object transport. To do so, we selected performance criteria geared towards applicability in real processes. In addition, we used an error model, which takes into account the noise and accuracy of all sensors (IMU and encoder) as well as the drift in odometry caused by the slip of the robot's wheels. The comparison includes a series of simulations using two trajectories with a changing number of robots and different formation geometries. In the simulations we got slightly better results for the Cartesian control law

Design of a parallel robot with additively manufactured flexure hinges for a cryogenic work environment

Automation is ubiquitous in today's industrial landscape and is finding its way into more and more highly specialised applications - also in the field of cryopreservation. The extreme work conditions in cryobanks place exceptionally high demands on the mechanical and electronic components used. The preservation and storage of biological samples take place at temperatures between -130 °C and -196 °C using liquid nitrogen as a cooling medium. The bearings and joints used in industrial parallel kinematic robots (for example, ball bearings or Cardan joints) jam at these ambient parameters and are unsuitable for an application within a cryobank. We, therefore, develop methods and technologies to enable fully automated handling of biological samples under cryogenic working conditions. The basis for this is a parallel kinematic robot structure that allows the drives to be placed outside the cold environment. In contrast, the rest of the robot structure can be actuated in a cryogenic container. In this context, the passive joints for this parallel robot are designed as additively manufactured monolithic flexure hinges. This paper presents the design, simulation, and construction of the parallel robot and focuses on the flexure hinges fabricated using the selective laser melting process (SLM). We describe the design of the flexure hinges, their intended use in the robot, and the experimental setup used for their validation. We also compare the operating parameters recorded in experiments (such as bending angle, bending moment) with the data obtained in finite element method simulations (FEM). In addition, we describe the geometric constraints and deviations of the manufactured joints due to the manufacturing process

Design optimization of soft pneumatic actuators using genetic algorithms

Recent trends in bioinspired robotic systems are paving the way for robots to become part of our daily lives. Soft robots, which are widely recognized as the next generation of human-friendly robots, are such a trend. Soft robots are generally more adaptable, more flexible, and safer than their rigid-link counterparts. Research in soft robotics has produced a broad variety of interesting solutions for all sorts of applications ranging from medical engineering and rehabilitation over exploration to industrial handling. This diversity together with a general lack of experience in designing with soft materials has contributed to a design flow that is highly empirical in nature. For soft robots to become mass-producible in the near future, more general design and modeling methods are needed. In this article, we present a method for the design optimization of soft robot modules that effectively combines finite element modeling and gradient-free optimization. To demonstrate the feasibility of the approach, a soft pneumatic actuator is designed and optimized. Performance analysis of the optimization scheme shows the robustness of the solution in the given case

Handling of large and heavy objects using a single mobile manipulator in combination with a roller board

This paper presents a method for autonomous loading, transportation, and unloading of large objects using a nonholonomic mobile manipulator. Here, the size of the transported object is considerably larger than the size of the mobile platform, which is made possible through the use of a roller board. In this way, the mobile manipulator can handle objects that exceed the manipulator's payload. The robot can load and unload the object onto its platform using the differential kinematics of the system for a null space motion to maintain the object's position in space. In order to localise the object, we apply 3D-perception using a depth-camera. While transporting the object to its destination, the robot is considered a tractor-trailer-wheeled system and can navigate using SLAM. Kinematic modelling and practical evaluation prove that the system can potentially take over arduous transportation tasks