Mathias Hüsing

Development of a multifunctional robot end- effector system for automated manufacture of textile preforms

In addition to the well-known application fields of composite materials in the aircraft industry, sport cars and wind energy, there are further potential applications e.g. rail, automobile and machine construct. In contrast to dry technology (prepreg), wet technology using reinforced textile preforms offers a cost-effective production of composite structures. These are due to low cost materials, easier storage conditions and automation possibilities. In this work, a new multifunctional robot end-effector system for automated manufacture of textile preforms is developed, designed and implemented. The robot end-effector system consists of an adaptive end-effector (AEE) to grasp, manipulate and lay-up the composite fabric onto a flat or curved mold and a novel double tool changer (DTC) to drape the fabric in the mold. The AEE is modular designed and features local passive and active degrees of freedom (DOF) to adapt the fabric geometry to the mold geometry. Furthermore, it is integrated with eight gripper elements with different grasp principles, such as ice-gripper or needle-gripper. Robots using DTC can carry two small tools (in this case two rollers to drape the fabric) and interchange them in the working position. With AEE and DTC, many manual processes in the production chain of textile preforms can be automated and can also be applied to the cost-efficient production of fibre composite parts. The application of this robot end-effector will be demonstrated by the production of a convertible car roof (CCR) with a pilot plant.

Self-optimising Production Systems

One of the central success factors for production in high-wage countries is the solution of the conflict that can be described with the term “planning efficiency”. Planning efficiency describes the relationship between the expenditure of planning and the profit generated by these expenditures. From the viewpoint of a successful business management, the challenge is to dynamically find the optimum between detailed planning and the immediate arrangement of the value stream. Planning-oriented approaches try to model the production system with as many of its characteristics and parameters as possible in order to avoid uncertainties and to allow rational decisions based on these models. The success of a planning-oriented approach depends on the transparency of business and production processes and on the quality of the applied models. Even though planning-oriented approaches are supported by a multitude of systems in industrial practice, an effective realisation is very intricate, so these models with their inherent structures tend to be matched to a current stationary condition of an enterprise. Every change within this enterprise, whether inherently structural or driven by altered input parameters, thus requires continuous updating and adjustment. This process is very cost-intensive and time-consuming; a direct transfer onto other enterprises or even other processes within the same enterprise is often impossible. This is also a result of the fact that planning usually occurs a priori and not in real-time. Therefore it is hard for completely planning-oriented systems to react to spontaneous deviations because the knowledge about those naturally only comes a posteriori.

Reconfigurable handling system

The demand for more versatile assembly and handling systems to facilitate customized production is gaining in importance, especially with regard to the constantly-increasing cost pressure, to expansion of the range of product versions and the shortening of innovation cycles. As a cost-effective approach for frequently changing assembly tasks, a novel manipulation concept has been developed by combining given robot technologies. This new handling system has a modular and adaptable layout, which consists of several mobile arms to manipulate the object in six-dimensional Cartesian space. After grasping, when the arms are attached to the object, the mechanical architecture is similar to parallel manipulators or cooperating robots. As the mounting and gripping points of the arms can easily be changed, the manipulator can be reconfigured so as to match the user’s preferences and needs. In addition to the kinematic adaption the regarding task, the hardware and new functions can be reconfigured as well. Contact elements, measurement and assembly devices as well as testing modules can easily be in integrated in the concept. A modular automatic control concept combined with a self-optimizing planning tool helps the user to find the optimal configuration and realize it in an economic way.

Reconfigurable Self-optimising Handling System

Demand for more versatile assembly and handling systems to facilitate customised production is gaining in importance. A new handling principle has been developed as a cost-effective approach to adapt to component-dependent tasks. It is based upon the gripping and movement of objects by multiple arms within a parallel kinematic structure. This structure combines the advantages of a system of co-operating robots with a simplified drive concept, in which the number of drives used is sharply reduced. On this basis, a modular assembly platform is being developed which, in addition to the kinematic units, also facilitates the integration of measurement, testing and joining modules. The modular concept also creates the conditions for a versatile, demand-driven layout of multiple kinematic units. This facilitates not only cooperative handling of large components using several gripping points, but also the transfer of objects handled between the individual units. These features of adaptivity are the basis for self-optimisation, which then can be implemented within a suitable control system.

A New Way of Grasping: PARAGRIP—The Fusion of Gripper and Robot

In this chapter a novel flexible and versatile handling concept, called PARAGRIP (Parallel Gripping), will be presented. This concept is based on a reconfigurable architecture with a modular and alterable layout. The robot system is able to handle objects with six degrees of freedom (DOF) by forming a parallel kinematic structure including several robotic arms and integrating the object as a movable platform. As many kinematic parameters, like the grasp and base points of the arms as well as the arm combination can be chosen freely, the handling system offers a fast and easy possibility to adapt the system to the requirements of the task. This adaptation can proceed before or even during manipulation. The latter is realized by regrasping, if more than three arms are available in the layout. This chapter deals with the questions, which reconfiguration possibilities are offered by this handling system and how a configuration set can be planned automatically.

Teaching in Mechanism Theory – From Hands-on Analysis to Virtual Modeling

Besides conventional lectures and exercises, application focused training provides an excellent opportunity to enhance understanding of mechanism theory. At RWTH Aachen University such training in the form of practical courses is part of the curriculum for students of mechanical engineering. This paper presents a concept for this kind of courses. At the application of cup-holders students perform hands-on analyses of the mechanisms in order to comprehend their kinematical structure and behavior. Based on this, diverse modeling approaches are used to illustrate different aspects of kinematics and design.

A General Classification for Mechanisms Regarding the Motion Task

This paper presents a general classification method for mechanisms regarding the motion task which is used for storing mechanisms in a database. This classification bases on a practical oriented concept. A motion task to be solved can be described by pre-defined characteristics in a search engine in the IGM-Mechanism encyclopaedia. Through a comparison with the saved data in the database possible mechanisms were offered as solution for the motion task. The user can choose among these possibilities to find the best mechanism.

Development of a Spherical Linkage Mechanism with the Aid of the Dynamic Spatial Geometry Program “GECKO”

In this presentation the development of a spherical linkage mechanism for passenger vehicle swivel joint tow coupling is reviewed. The idea for the swivel joint tow coupling emerged after a cooperation between the Department of Mechanism Theory and Dynamics of Machines (IGM) of the RWTH-Aachen University and a market leading manufacturer of tow bar mechanisms. Presently, the swivel joint mechanism has been patented worldwide [1]. Additionally, a prototype of the tow coupling is currently in an advanced design phase, in which the possibilities for cost optimization and suitability for series production are assessed. The dimensions of the spherical mechanism were defined using the dynamic spatial geometry program “GECKO” currently developed at IGM.

AutoHD—Automated Handling and Draping of Reinforcing Textiles

In almost all industrial sectors handling processes are automated through the use of robotic systems. However, in the manufacture of fiber-reinforced structures with complex geometries, the handling of dry, pre-impregnated semi-finished textiles is still performed mainly manually resulting in long processing times, low reproducibility and high manufacturing costs. A previous AiF research project “AutoPreforms” aimed at the automation of the entire production process of components with uniaxial curvature. The scope of this AiF research project “AutoHD” is to fully automate the draping and handling process of complex, three-dimensional fiber composite structures with high degrees of deformation and multiaxial curvature (e.g. car wings). Based on a draping simulation wrinkles can already be recognized during the draping process and counteracted by the developed mechanical structure. This is achieved by the utilization of the bending stiffness of textile semi-finished products, a flexible end-effector and a built-in optical quality assurance process. In this paper the main aspects of preforming processes are described revealing the challenges of the project. With examples of currently existing systems, the objective and innovative contribution of the project are described. The paper serves as initial presentation of the project and its solution approaches.

Synthesis and Modeling of Redundantly Actuated Parallel Kinematic Manipulators—An Approach to Efficient Motion Design

Spatial object manipulation is subject to various parameters, which can be optimized by means of suitable motion strategies. In addition, corresponding strategies can be adapted to specified handling devices enabling efficient motion design with respect to kinematic and dynamic characteristics of particular manipulators. Further optimization is provided by the application of robot redundancy, whose resolution can be adapted to efficient motion planning. In this context, parallel kinematic systems featuring kinematic redundancy or a redundant actuator concept can be operated with an optimal set of actuator parameters allowing a resource-efficient object manipulation. This contribution is devoted to the conception and modeling of redundantly actuated parallel kinematic manipulators (RA-PKM) in order to realize optimal configuration strategies and motion design. Accordingly, the structure selection and the dimensional synthesis of a translational RA-PKM are presented based on parametric kinematic and dynamic modeling. Corresponding models provide an application-oriented transformation from intuitive CAD design software to technical computing and simulation software. The developed manipulator is suitable for the comparison of different redundant and non-redundant actuator configurations as well as optimal trajectories. Concluding analyses exemplarily refer to a non-redundant 3-arm and a redundant n-arm PRPaR system.