Papers by Keyword: Localisation

Abstract: To respond to challenges created by an increase of product variants, multi-variant lines are used as today’s assembly systems. In these multi-variant lines different product variants with diverse lot sizes can be efficiently assembled. These assembly systems are characterized by modular structures that allow assembly system adaptation by reconfiguration.The variety of parameters to be considered from the product’s perspective and the correct allocation of different assembly modules increases the complexity when planning these systems. This complexity makes it difficult to successfully plan and implement production processes. Therefore, digital planning tools and models have to be used to schedule new product variants and to verify that the assembly is possible, given by the modules in the assembly line.Due to its ability to reconfigure, the actual assembly system is adaptable to different product variants. But these modifications are performed by the operator on the shop floor and are often neither properly documented nor communicated to the assembly planer. Thus, the configuration status in reality and the virtual model differ from each other. Using the outdated model for planning without taking into account the changes can result in an unrealizable assembly plan.To overcome this problem, the presented paper introduces a method and technical system to identify the actual assembly system configuration before the assembly planning is done. Due to the subsequent update of the virtual model depending on the actual configuration, the assembly planner is supported with the latest version of the assembly system configuration. Furthermore, the assembly planning process is improved, because possible failures are detected in advance in the virtual planning environment.

Abstract: The paper presents a proven method used for supporting the implementation management control process of RFID technologies to track the location of objects in a retail environment. Using a SWOT analysis, we identified several scenarios that guide the company in the implementation process of the technology according to its own chosen strategy. In accordance with our results, non-traditional applications of the UHF RFID technology could have a high application potential. The outcome of our work may in the future provide the basis for applying the described solution that could enable a deeper study of interactions between the allocation of product classes on the sales floor and retail customers.

Abstract: In this paper, a method for the localisation and quantification of impacts on orthotropic plates, based on the measurement of the resulting vibrational energy flow, or structural intensity, is presented. The outputs of a compact array of bonded piezo-electric sensors are digitally filtered and combined to yield a local estimate of the instantaneous vibrational energy flow. In the case of transient vibration due to an impact, two or more such estimates can be used to localise the point of impact. The use of energy flow vectors for localisation requires a priori knowledge of the material properties, but may provide more direct access to position information than conventional techniques. Furthermore, the magnitude of the measured energy flow, when combined with knowledge of the impact location, can provide a quantitative measure of impact severity. The approach is based on Kirchhoff orthotropic plate theory, and is thus applicable to low frequencies, and utilises instantaneous estimates of the local wave field to allow the estimation of the various forces, moments and velocities that are required to calculate the vibrational energy flow. The theoretical background and principles of implementation of the approach are outlined, and the effects of sensor array design on systematic errors and sensitivity to measurement noise are discussed. Numerical simulations are used to assess the effectiveness of the technique and to determine its sensitivity to noise and other errors. These simulations suggest that the obtained energy flow estimates can be used for impact localisation.

Abstract: The reported research concerns experimental investigation toward the monitoring of an aircraft panel. Guided wave propagation phenomena were used to obtain information about the state of the monitored structure. A curved aluminium panel with rivets was investigated. Piezoelectric transducer was used to excite guided waves in chosen structural element. The generated signal was amplified before applying it to the transducer in order to ensure measurable amplitude of excited guided waves. Measurement of the wave field was realized using laser scanning vibrometer that registered the velocity responses at a points belonging to a defined mesh. This contactless measurement technique allowed to investigate phenomena related to wave propagation in the aircraft panel. In the first stage, due to high complexity of the element, baseline measurements were taken. Next, a discontinuity (additional mass) was introduced on the panel surface and the measurements were repeated. Signal processing methods for features extraction from signals were proposed. These features were applied in order to detect and localize the presence anomalies in the investigated panel. The signal processing was conducted in MATLAB with the procedures developed by the authors. The used measurement technology (vibrometer) allowed to register whole wavefield of the propagating guided waves. This allowed to visualize the interaction of the waves with rivets. After introducing the discontinuity on the panel surface wave interaction with it was investigated. Two positions of the additional mass were considered. One just before the riveted stiffener and second after the stiffener. Because of this the influence of the stiffener on the damage detection abilities could be investigated. It can be concluded that the guided wave can be used for monitoring of such complex structures. The vibrometer measurements allowed learn about the guided wave propagation phenomena and perform successful damage localization.

Abstract: The tension behaviour of initially austenitic NiTi thin wall tubes was investigated using measurements of temperature and strain fields simultaneously. The first specimen was totally superelastic but the unloading was performed before the end of the loading stress plateau. The second specimen loading was performed beyond the stress plateau to allow analyzing the unloading, but was not superelastic and at a faster strain rate. Both tests show homogeneous behaviour at the beginning of the loading. Strong localisations, taking the shape of helical bands, are observed during the loading and unloading stress plateaus. To obtain quantitative energy information, allowing a better recognition of the deformation mechanisms, an estimation of the local heat sources based on image processing of the temperature fields is presented. Two methods of heat sources estimation allowing analysis of deformation mechanisms are proposed in the present paper: first during the homogeneous, then during localized stages.