Hybrid Dynamic Substructuring in the Industry of Home Appliances

Vibro-acoustic comfort is becoming increasingly important in residential homes. Noise levels in household appliances are attracting attention from manufactures and customers. In addition, manufacturers have identified the acoustic performance as a means to improve their position over competitors. The design and vibro-acoustic performance together contribute to the customer’s perception of a premium product, and hence its value on the market.   In industrial practice products are usually subdivided into the subsystems that are delegated to either in-house manufacturing departments or external suppliers. In the industry of household appliances one can imagine that the core parts are developed by the manufacturers themselves, whereas the supplementary accessories like electric motors, compressors, mechatronic systems, etc. are outsourced to specialist external suppliers. Considering the vast amount of active systems in today’s household appliances, the resulting sound would become a sheer cacophony without proper NVH engineering. In order to assess the dynamics of subsystems with respect to their performance in the complete product, methods are required to integrate their dynamic contributions in a physically correct way. Dynamics Substructuring is a powerful engineering concept to model and analyze a dynamic system in term of its components or substructures. Smaller substructures could be solved individually and synthesized by satisfying the coordinate compatibility and force equilibrium at the substructures’ interfaces.   Today, substructuring is well established practice in analytical and numerical domain; however the expansion to the experimental domain has not yet been widely adopted. Many of these efforts have failed because the substructuring calculation can be very sensitive to experimental uncertainty and truncation of the subcomponents models. The novel methodology within this project aims towards the development of new hybrid numerical/experimental substructuring approach which will significantly improve the quality of dynamical models in term of consistency and efficiency. This requires a methodology that allows the implementation of experimentally measured models into a numerical modeling environment or assembling subsystems regardless of their modeling nature. Hence, this hybrid model implements realistic description of the experimental model, combined with extensive DoF-space and consistency associated with the numerical model.  Usually hybrid formulation is developed within frequency domain where it is difficult to address data contamination and ill conditioning. By extending the hybrid approach to modal domain it will be possible to apply smoothing process using FRF synthesis algorithm and by comparing modal parameters to identify the outliners from the data.   The applicability of proposed hybrid modeling approach will be extended by development of more complex interface dynamics models. Usually analyzed simplified point connections will be extended to more complex line and surface connections. This will be possible by development of new innovative measuring algorithms for direct and indirect measurement of usually omitted rotational degrees of freedom. New method for indirect reconstructions of rotational degrees based on full displacement field measurement using high-speed camera will present completely new methodology for interface dynamics description. Hence, the projects goals are orientated towards reliable modeling of complex real-life systems that are integral part of today’s household appliances.

Today, substructuring is a well-established practice in the analytical and numerical domain; however, the expansion to the experimental domain has not yet been widely adopted. Many of these efforts have failed because the substructuring calculation can be very sensitive to experimental uncertainty and truncation of the subcomponents models. The novel methodology within this project aims at the development of a hybrid numerical/experimental substructuring approach, which will significantly improve the quality of the dynamic models in terms of consistency and efficiency. This result will enable the reliable modeling of complex real-life systems that are an integral part of today’s household appliances.   The proposed research program of the project is also of great importance for, the establishment of substructuring methods as a successful and effective scientific approach. Together with the potential of hybrid substructuring, the presented methodology offers great opportunities for the early-phase engineering of sound and vibration problems. This is especially beneficial in applications where certain subcomponents may be difficult to model due to ill-characterized materials or an intricate geometry. By using the hybrid approach simplified numerical models can be constructed that in connection with dynamics testing make it possible to couple this subcomponent with the rest of the model.

The project will have direct effects on partners, as it will result in an increased number of researchers, enhanced cooperation and synergy effects between research institution and industry. The research proposal directly addresses the European Council Directive 86/594/EEC that presents the framework on noise emitted by household appliances. This directive encourages manufacturers and importers to produce less vibration and quieter appliances. Today, the co-partner in the project, GORENJE, is acting on the global home-appliances market and competes with global companies such as Bosch, Miele, AEG, etc. With the implementation of the proposed project new knowledge will be established that will reduce the cost of product development, circumventing the need to build up detailed numerical models of subcomponents and enable effective vibroacoustic optimization of products. This will enable GORENJE to develop silent and low-vibration products that will help to reduce the exposure to noise pollution in residential homes. This kind of home appliances, with higher added value, will result in growth of GORENJE market share on European and global scale.  Hence, the project is also important in term of providing new jobs.   By participating in the project, the laboratory LADISK (UL, FS) will expand its competencies and in this way strengthen his position as a research and development partner. This will reflect in promotion of national academic and technical community in terms of publishing in scientific journals.