theory:sensor_technology:st11_finite_element_models

*The values of the model entities (the lumped elements) are not straightforward to determine in all cases. This can be due to the fact that an element represents a phenomenon which can not be localised intuitively, that it represents a non-linear effect or that it is difficult to be represented in a single element. Examples are cases where all the vibrational modes of a plate have to be considered, when the shape of a structure is very complicated or when there is no analytical solution to a certain non-linear differential equation. In that case modelling must be based on the motional differential equations directly.*

The Finite Element Method (FEM) is based on spatial segmentation of a structure where each segment is described by its coupled differential equations. Software packages like ANSYS, COMSOL, CoventorWare and FEMLAB are available for numerical evaluations and provide graphical representations of the results.

However, this method has several drawbacks. The finite element method is a low-level interpretation of the physical behaviour. To combine them into macroscopic overviews of device characteristics, large capacity with respect to memory and calculation speed is required. It is very hard to maintain the systems overview since the links between physical domains have become invisible. In many cases, the designer has to limit himself to a FEM analysis of only a part, one or two domains, of the problem to limit the complexity of the problem. To understand the relation between design parameters and performance in FEM analysis it has become the skill of the scientist, rather than the power of the tool as we have seen with the lumped element method.

These are the chapters for the Sensor Technology course:

- Chapter 1: Measurement Theory
- Chapter 2: Measurement Errors
- Chapter 3: Measurement Domains
- Chapter 4: Circuits, Graphs, Tables, Pictures and Code
- Chapter 5: Basic Sensor Theory
- Chapter 6: Sensor-Actuator Systems
- Chapter 7: Modelling
- Chapter 8: Modelling: The Accelerometer - example of a second order system
- Chapter 9: Modelling: Scaling - why small things appear to be stiffer
- Chapter 10: Modelling: Lumped Element Models
- Chapter 11: Modelling: Finite Element Models
- Chapter 12: Modelling: Transducer Characterization by Impedance Spectroscopy ← Next
- Chapter 13: Modelling: Systems Theory
- Chapter 14: Modelling: Numerical Integration
- Chapter 15: Signal Conditioning and Sensor Read-out
- Chapter 16: Resistive Sensors
- Chapter 17: Capacitive Sensors
- Chapter 18: Magnetic Sensors
- Chapter 19: Optical Sensors
- Chapter 20: Actuators - an example of an electrodynamic motor
- Chapter 21: Actuator principles for small speakers
- Chapter 22: ADC and DAC
- Chapter 23: Bus Interfaces - SPI, I
^{2}C, IO-Link, Ethernet based - Appendix A: Systematic unit conversion
- Appendix B: Common Mode Rejection Ratio (CMRR)
- Appendix C: A Schmitt Trigger for sensor level detection

theory/sensor_technology/st11_finite_element_models.txt · Last modified: 2017/10/10 18:39 by glangereis