Marcus Perner

Clarifying vibrational issues of an advanced automated fiber placement production plant

Advanced Fiber Placement is the technology being used to manufacture large-area, high quality parts of fiber composite materials. Due to the large-scale the production cycles are long and the parts become very expensive. One promising approach for improvement is to increase the desired laying accuracy to avoid degraded parts combined with higher laying speed. This paper deals with vibrations caused by operating plant components which reduce the production accuracy and speed for composites. Therefore, vibrational issues concerning single and linked elements of the production plant are in focus. Accordingly, the test setup consisting of autonomous data logger, and sensing elements is illustrated. Different scenarios to gain measurement data are studied. The recorded data is analyzed to explore the source of vibration. The vibrations origin is based on eigenfrequencies and the related eigenmodes are excited by operation. Based on the analyzed data an optimized plant layout is proposed. The use of additional sensors and smart structures technology is discussed.

Smart device for advanced robot-based automation: The system design

Articulated robots are one of the major components in automation. They provide a large operation area in relation to their constructed size. Due to the serial structure the weight of each drive engine is carried by the axis and has to be moved along. To follow the increasing demands in aviation industry higher speed and precision are addressed in production. Higher speed excites vibrations that affect the part quality. Therefore, this paper presents an approach for a smart device with one additional axis. The axis compensates for lateral vibrations relative to the layup direction. Mainly, the design of the mechanism is illustrated within this paper. The system consists of a lever mechanism to enlarge the displacement of the actuator, and a motion platform to support the pressure roller. Finally, the paper concludes with issues about the integration into the robots structure and ideas for further applications.

An Approach for Autonomous Damage Detection by Means of Modal Fingerprints

This article discusses whether elastic and plastic impacts and scratches caused by applied forces (e.g., car bump, key scratch etc.) to a parked vehicle can be distinguished by an autonomous system. The authors assume that a force impact to a vehicle stimulates characteristic frequencies in the vehicle body shell components that can be used to distinguish the given damages. Eight piezoelectric film sensors made of polyvinylidene fluoride mounted at the inside of the vehicle body shell components doors, bumpers, bonnet, and tailgate are used as the sensing element. An experimental modal analysis of several vehicle components is performed to identify characteristic frequencies. The results are used to compute the best sensor position in order to detect all considered eigenfrequencies of the component. A constructed model set up for force generation was used to record reference data. Derived features of the reference signals are computed and assessed to their relevance of distinguishing the damages on the vehicle.

Static and quasi-static behavior of an adaptive system to compensate path errors for smart fiber placement

Smart fiber placement is an ambitious topic in current research for automated manufacturing of large-scale composite structures, e.g. wing covers. Adaptive systems get in focus to obtain a high degree of observability and controllability of the manufacturing process. In particular, vibrational issues and material failure have to be studied to significantly increase the production rate with no loss in accuracy of the fiber layup. As one contribution, an adaptive system has been developed to be integrated into the fiber placement head. It decouples the compaction roller from disturbances caused by misalignments, varying components’ behavior over a large work area and acceleration changes during operation. Therefore, the smart system axially adapts the position of the compaction roller in case of disturbances. This paper investigates the behavior of the system to compensate quasi-static deviations from the desired path. In particular, the compensation efficiency of a constant offset, a linear drift with constant gradient and a single-curved drift is studied. Thus, the test bed with measurement devices and scenarios is explained. Based on the knowledge obtained by the experimental data, the paper concludes with a discussion of the proposed approach for its use under operating conditions and further implementation.

Relation between repeatability and speed of robot-based systems for composite aircraft production through multilateration sensor system

Fiber composites are becoming increasingly important in different fields of lightweight application. To guarantee the estimated demand of components made of carbon fiber reinforced plastics the use of industrial robots is suggested in production. High velocity of the layup process is addressed to significantly increase the production rate. Today, the layup of the fiber material is performed by gantry systems. They are heavy weight, slow and the variety of possible part shapes is limited. Articulated robots offer a huge operational area in relation to their construction size. Moreover, they are flexible enough to layup fiber material into different shaped molds. Thus, standard articulated robots are less accurate and more susceptible to vibration than gantry systems. Therefore, this paper illustrates an approach to classify volumetric errors to obtain a relation between the achievable speed in production and precision. The prediction of a precision at a defined speed is the result. Based on the measurement results the repeatability of the robotic unit within the workspace is calculated and presented. At the minimum speed that is applicable in production the repeatability is less than 30 mm. Subsequently, an online strategy for path error compensation is presented. The approach uses a multilateration system that consists of four laser tracer units and measures the current absolute position of a reflector mounted at the end-effector of the robot. By calculating the deviation between the planned and the actual position a compensated motion is applied. The paper concludes with a discussion for further investigations.