Function model

Résumé

In systems engineering, software engineering, and computer science, a function model or functional model is a structured representation of the functions (activities, actions, processes, operations) within the modeled system or subject area. A function model, similar with the activity model or process model, is a graphical representation of an enterprise's function within a defined scope. The purposes of the function model are to describe the functions and processes, assist with discovery of information needs, help identify opportunities, and establish a basis for determining product and service costs. History The function model in the field of systems engineering and software engineering originates in the 1950s and 1960s, but the origin of functional modelling of organizational activity goes back to the late 19th century. In the late 19th century the first diagrams appeared that pictured business activities, actions, processes, or operations, and in the first half of the

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https://en.wikipedia.org/wiki/Function_model

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A functional model of software and its application in troubleshooting, design and reuse

EPFL1996

Chargement

Modelling, Simulations and Characterization of NEMS accelerometers based on graphene

Daniel Moreno Garcia

Accelerometers are widely used in industrial applications and consumer electronics. We can find them in automotive crash detection or fitness trackers. The majority are based on piezoresistive or capacitive effect which are limited by their large size. This negatively influences their utility in emerging applications such as Internet of Things and biomedical applications. NEMS (Nanoelectromechanical systems) are presented as a possible solution for this problem. The accelerometers used in this project are made of a suspended graphene membrane and an attached silicon proof mass. They were fabricated by KTH researchers. We study the possibility of measuring accelerations by monitoring the changes in the device resonant frequency. If proven, to the best of our knowledge, they would be the first ultra-miniaturized and sensitive resonant accelerometer. To do so, we built a functioning model of the accelerometers by combining a theoretical framework and finite element simulations. The chip was placed on a piezo-shaker and measurements were conducted using a Laser Doppler Vibrometer. To complement the study, further measures were taken with an Atomic Force Microscope and a Digital Holographic Microscope. The results show a good match between theory and simulations. However, the acceleration measurements in the device show higher signals not related with accelerations. We proved they were related to displacements and theorized that they were caused by internal chip forces. Horizontal forces on the accelerometer frame could eclipse the effect of the accelerations on the resonant frequency. We suggest the use of a more rigid chip frame as a potential solution.

2020

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Creating Virtual Prototypes of Complex MEMS Transducers Using Reduced-Order Modelling Methods and VHDL-AMS

Torsten Mähne

In this chapter the creation of "virtual prototypes" of complex micro-electro-mechanical transducers is presented. Creating these behavioural models can be partially automatised using a reduced-order modelling (ROM) method. It uses modal decomposition to represent the movement of flexible structures. Shape functions model the energy conservation and full coupling between the different physical domains. Both modal shapes and shape functions for strain energy and lumped capacitances of the structure can be derived in a highly automated way from a detailed 3D finite elements (FE) model available from earlier design stages. Separating the generation of the reduced-order models (ROM) from the same FE model but for different operation directions circumvents current limitations of the used ROM method. These sub~models are integrated into a full model of the transducer. VHDL-AMS is used to describe additional strong coupling effects between the different operation directions, which are not considered by the used ROM method itself. The application of this methodology on a commercially-available yaw rate sensor as an example for a complex transducer demonstrates the practical suitability of this approach.

Springer2006

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