CST STUDIO SUITE

Electromagnetic Design and Analysis of Sensors

www.cst.com

The electromagnetic fi eld and its accurate measurement plays an important role in a wide range of sensor applications. CST STUDIO SUITE® allows the simulation of electromagnetic fi elds in such devices and uses a range of state-of-the art Finite Element Method (FEM) and other complementary simulation methods. The user can choose the best method for effi ciently modelling the sensor at hand. This is combined with an easy-to-use but powerful graphical user interface, comprehensive CAD and EDA import and application-oriented workfl ows.

Eddy current sensors Magnetic fl ux lines in a shaded-ring linear position sensor.

Electromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of Sensors

www.cst.com

Virtual Prototyping

Performance, cost and reliability – these critical factors are ultimate-ly responsible for the success or failure of a sensor project. Virtual prototyping allows the performance of a sensor design to be investi-gated early in the design process, without the time and costs associ-ated with traditional prototyping. These virtual prototypes can also be modifi ed easily, in order to compare different design concepts, and to characterize the effect of manufacturing tolerances and ther-mal variations.

Field Visualization

Electromagnetic fi eld simulation offers the designer a unique in-sight into the operation of a sensor which cannot be easily achieved in measurement. Visualization of phenomena such as electric and magnetic fi elds and eddy currents can help further understand the behavior of the device and suggest possible improvements to the de-sign. Simulation can also be used to ascertain the effect of unwanted nearby objects on the fi eld and electrical parameters in the sensor.

Permanent magnet sensors Magnetic fi eld vectors in the fl ux collector of a permanent magnet angular position/torque sensor.

Optimization

A successful sensor design is one that achieves the necessary level of sensitivity while minimizing the device’s size, cost and power con-sumption. However, the number of interdependent elements and design variables in a typical sensor means that optimizing a sensor manually can be a daunting task. The built-in local and global opti-mizers in CST STUDIO SUITE can be used to automatically optimize numerous design parameters, including the geometry, material properties and signal characteristics, in order to improve the perfor-mance of the sensor.

Modeling and CAD Data Import

A major strength of CST STUDIO SUITE in the simulation pro-cess of sensors is the import of complex geometries. Numerous 2D/3D CAD formats are supported, including Pro/E, STEP, DXF and CATIA, as well as EDA formats such as Mentor Graphics Expedition, Gerber and ODB++.

www.cst.comwww.cst.com

Imported models can be easily modifi ed and even parameter-ized for later optimization. For engineers working in large teams, CST STUDIO SUITE can also monitor the imported fi le in order to check for changes in the original model and notify the user. In other words, the effect of changes to the sensor’s environment can be easily established with little user effort.

As an alternative, the geometry can be created with the powerful modeling tools in CST STUDIO SUITE. This provides an increased lev-el of control of the model geometry. Automation using VBA macros can further enhance this process, allowing the automated construc-tion of, for example, complex winding systems. Models created in CST STUDIO SUITE can also be exported for use in other engineer-ing design tools.

0

0,00005

0,0001

0,00015

0,0002

0,00025

0,0003

0,00035

0,0004

0 0,02 0,04 0,06 0,08 0,1 0,12 0,14 0,16 0,18 0,2

Q-s

ensi

tivity

/ 1/

mm

Frequency / MHz

Q-factor sensitivity

Inductive sensors Q-Sensitivity of the inductive proximity sensor with maximum

at 100 kHz.

A comprehensive range of sources and material models is required to cover the simulation of many types of sensor, including non-linear magnetic materials.

The Best Tool for the Job

A key element in an effi cient simulation workfl ow is the choice of the appropriate solver for the problem. CST STUDIO SUITE offers a complete range of solvers from static to full-wave with differing lev-els of physical modelling. These solvers are all linked and are avail-able in the same interface, simplifying the workfl ow for simulations that involve multiple solvers.

The simulation workfl ow in CST STUDIO SUITE for a proximity sensor, for example, might involve an initial stage confi rming the operating range of the sensor, followed by a more detailed analysis of the design. In the fi rst stage, approximations may be made to en-able rapid simulation and parametric analysis, which makes the ef-fi cient magneto-quasi-static solver. Once the initial design concept is ready, a more detailed analysis is carried out by upgrading the coil to a fully-wound model and simulating with a full-wave solver. This can account for the displacement current and eddy currents as well as proximity effects in the winding.

Inductive sensors Full 3D CAD model of an inductive proximity sensor.

Accurate modeling of winding can be created by VBA macro…

… or defi ned analytically using stranded coil models.

Displacement, eddy current and proximity effects in the windings can be calculated by

full-wave simulation. Here, the proximity effect is shown.

www.cst.com

SimulationExperiment

Imag

inar

y pa

rt o

f diff

eren

tial f

lux

Real part of differential flux

-0.5

0

0.5

-2

-1.5

-3

-2.5

-1

-1 0 1 2 3 4 5

Post-Processing

Nearly all sensor simulations require a common set of parametric and post-processing capabilities. CST STUDIO SUITE offers a clear and simple workfl ow for data visualization and data processing, with the ability to perform complex sequences of post-processing tasks automatically. Linearity and other Q-measures can be de-rived automatically, and post-processing templates can be used to derive numerous other values. Field quantities can be extracted and plotted at points, along complex user-defi ned curves and fac-es, and in volumes. Combined with integrated parametric analy-ses, the user may easily see the effects of changes in material and geometrical properties.

Lissajous fi gure Simulated versus measured lissajous characteristics for the TEAM 8

NDT Benchmark.

Advanced Workflows

System Assembly and Modelling (SAM) is a general framework that permits advanced simulations of more complex problems and al-lows the user to tailor the workfl ow to your needs. It also enables notorious numerical hurdles in sensor simulation to be surmounted. In non-destructive testing (NDT), mesh noise may dominate the numerical problem. Using SAM, elegant solutions may be applied to combine multiple solutions and to alleviate the effect of mesh. There are a large number of applications for SAM, including nested design parameter optimizations and the solution of multi-physics problems involving thermal or structural mechanical phenomena, linking EM fi eld results into multiphysics simulations.

Non-destructive testing Eddy current visualization around a fl aw detected by an NDT eddy current testing device.

Electromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of Sensors

www.cst.com

Complete Technology All the solvers in CST STUDIO SUITE and circuit simulation tools are integrated in a common user interface, and data can be automatically

transferred from one simulation to another using SAM.

Electromagnetic fi eld simulation offers numerous different types of data, but how can it be used at each step in the design process? CST STUDIO SUITE can be used to design and optimize touchscreens like those shown above from scratch, but it can also be implemented in existing workfl ows by taking advantage of the import/export features. In this case, the electrode systems

were imported from an EDA tool and the fi nger was imported from a CAD model. These were parameterized and linked to a circuit simulation. System Assembly and Modeling was then used to simulate the behavior of the sensor for multiple fi nger positions and automatically optimize the sensor.

Case Study: Touchscreen Design Workflow

Electromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of SensorsElectromagnetic Design and Analysis of Sensors

www.cst.comwww.cst.com

Features

Modeling

ó Built-in model creation and parameterization tools ó Import/export tools (including STEP, Pro/E and EDA formats) ó Numerous source models, including magnets and coils ó Non-linear magnetic materials ó Surface impedance materials

Simulation

ó Automatic 2D and 3D meshing and mesh adaption ó Electrostatic and magnetostatic solvers ó Non-linear and quasi-static solvers ó Full-wave FEM solvers ó Multiphysics capabilities – thermal and structural mechanics ó Coupling to built-in circuit simulation

Results processing

ó 1D, 2D and 3D results visualization ó Post-processing: fi elds at points, on faces and along user-defi ned lines;

calculation of integrals, fl ux, forces, etc. ó Sensitivity and yield analysis

Automation

ó Fully-integrated parametric and optimization modules ó System Assembly and Modelling (SAM) ó Project management, design variation comparison, etc. ó Automation via VBA macros ó Distributed computing

Trademarks

CST, CST STUDIO SUITE, CST MICROWAVE STUDIO, CST EM STUDIO, CST PARTICLE STUDIO, CST CABLE STUDIO, CST PCB STUDIO, CST MPHYSICS STUDIO,

CST MICROSTRIPES, CST DESIGN STUDIO, CST BOARDCHECK, PERFECT BOUNDARY APPROXIMATION (PBA), CST EMC STUDIO, and the CST logo are trademarks or

registered trademarks of CST in North America, the European Union, and other countries. Other brands and their products are trademarks or registered trademarks of their

respective holders and should be noted as such.

CST – Computer Simulation Technology AG, Bad Nauheimer Str. 19, 64289 Darmstadt, Germany