Entwicklung einer Parallelkinematischen Struktur für den 3C Anwendungsbereich
Final Report Abstract
The intention of this knowledge transfer project arose from the CRC 562. The main topic of the project concerned methods for the development of a production device for the flexible automation in assembly of computer, communication and consumer electronics (3C). To this end, methods for a decision-making procedure were developed for designing mechanisms which extend the functionality of a conventional industrial robot. The extension mechanism should be able to govern out the deficiencies of the production device, like the degree of freedom, with respect to the assembly tasks. At first, the requirements’ analysis for designing extension mechanisms was addressed. Assembly operations were investigated so that a sample application could then be defined. For this purpose, the project partner ABB made a fundamental contribution to this investigation, since it is a manufacturer of 3C products, such as industrial electronics, and a supplier of robotic automation solutions. The sample application comprises the joining process as well as the handling operation, which was implemented as a pick-and-place operation. The joining process was used to define forces at the end-effector, whereas the latter defines the motion of the joints. The requirements were used to evaluate available robots, focused on parallel robots, and to deduce their deficiencies. A tool was developed that is based on an Excel database to manage the collected data. It comes along with a method to analyze the level of compliance of a robot system with respect to the requirements. Amongst the considered robots, some prototypic parallel robots of the collaborative research centre CRC 562 (Robotic Systems for Handling and Assembly), such as PARAPLACER, TRIGLIDE or HEXAII, were taken into account. In general, the work profited from the insights of the CRC 562, especially from the insights of the project field A about design and modeling of parallel robots. Since the project should be focused on the product portfolio of ABB, a FlexPicker robot, which is associated to the class of delta robots, was selected to be extended. It turned out, that this structure must be extended by three additional, rotational degrees of freedom. The classification of different, rudimentary design principles of the extension mechanism was subsequently done. Conceivable extension mechanisms were developed for this purpose and clustered by considering the configuration of their power trains and axes. In total, sixteen different concepts were investigated by means of a developed decision analysis method. The framework of this method was based on the analytic hierarchy evaluation process. To this end, suitable criteria, such as expected costs, mechanical stress of wires or accuracy, were analyzed with respect to the concepts’ functionalities. After setting up comparison matrices and making judgments between the concepts, the method was used to reduce the amount of solutions to six beneficial concepts. To refine the associated judgments, the criteria impact of the extension mechanism on the FlexPicker robot as well as the maximum needed torque of its motors were investigated more precisely. For this purpose, the dynamics of the entire structure was computed following the Newton-Euler and the Lagrange formalism. The dynamic models came along with pre-designs of the concepts so that realistic results could be obtained. The analysis resulted in the choice of an inline-wrist mechanism with motors directly attached to its axes as extension mechanism. The process followed up for the final mechanical design of the mechanism was supported by a developed method to analyze the sensitivity of different design parameters with respect to their influence on the stress impact on the FlexPicker robot, like the position or the mass of included components. This yielded detailed information about the relation between the design parameters and the results of the previous stress analysis to improve the entire design. Finally, possibilities for future developments were presented to enhance the benefit of the analysis. Two main aspects were identified which address an analysis of combined power train concepts as well as an automated optimization method to connect the location of the desired trajectory within the workspace of the entire robot with the stress impact of the additional mechanism on the structure of the robot. The presented methods are individually utilizable for other mechanical systems than robots. The design of the developed tools and processes facilitates their easy adaptation or extension. Thus, in conclusion, the primary outcome of the project is a universal analysis tool chain for designing and evaluating mechanical systems which have an influence on other, structurally coupled systems. It includes a tool for visualizing and quantifying the deficiencies of mechanical systems by considering the level of compliance of their specifications with respect to predefined requirements. It also includes a task-dependent decision making method with adaptable comparison matrices and judgments for mechanical systems which differ in their structural design and thus in their kinematics and dynamics. For this purpose, an approach for quantifying significant dynamical criteria is available. Moreover, a method is presented to optimize the components’ mass distribution of a mechanical structure by analyzing the sensitivity of design parameters.
Publications
- Analysis of the Mass Distribution of a Functionally Extended Delta Robot. In: RCIM - Robotics and Computer-Integrated Manufacturing
Volume 31, February 2015, Pages 111-120
Borchert, G.; Battistelli, M.; Runge, G. and Raatz, A.
(See online at https://doi.org/10.1016/j.rcim.2014.08.003)
