Model Simplification and Preparation for MHARNESS Co-simulation

 

This tutorial is a step-by-step demonstration on how to prepare and perform a full aircraft simulation. We go through how to simplify CAD geometry of cable-packs down to lines to be used in MHARNESS, and the steps to prepare a model for a co-simulation with EMA3D and MHARNESS.

MHARNESS is a transmission line solver that enables the user to simulate levels on individual electronics pins at equipment interface. MHARNESS requires special geometry to be present in the model in order to define where the transmission lines are to be located. This training goes through how to create this geometry from the CAD.

To download the training documents: Click HERE

CADfix and EMA3D HIRF Training

HIRF_tail_cropped

 

By Eric Miller

Click Here to download training file. The Training can also be viewed below.

The purpose of this training module is to build familiarity with the basic functions of CADfix and EMA3D.
By building a very simple plane model, you will learn basic geometry creation and modification
techniques. Due to the limited nature of this training module, many CADfix techniques won’t be shown.
In later modules, more advanced techniques will be explored.

Almost everything in CADfix can be done using either a GUI (graphic user interface) or using a command
line input. In this training, both methods will be shown for the applicable steps. Often, beginning users
find the GUI easier than the command line. However, the command line can greatly increase efficiency
and more naturally lends itself to the creation of user-written macros.

Once the plane geometry is constructed, you will follow the steps to turn the CADfix model into an
EMA3D simulation. The process shown in this module is intentionally left basic to prevent tedium.

Note: This training was made using CADfix 10 SP2.0

Download Training File

Introduction to EMA3D and CADfix

By Eric Miller

airplane-model-before- lightning-EM-simulation airplane-after-lightning-simulation

Click Here to download training files

In aircraft development, significant resources are spent to ensure safety during a lightning strike. Experiments are very costly and it’s impossible to measure every interesting quantity at every location. With lightning simulations, a more complete data set can be taken (all field values can be known
in any location). Simulation data can greatly help guide the designs and tests to demonstrate compliance with FAA regulations such as 25.981 (fuel tank ignition prevention).

In this training, a simple aircraft is created using basic geometry. The aircraft is created using CADfix and is prepared for an EMA3D simulation. The simulation case is a component A lightning strike on the wingtip and opposite wingtip detachment. In the process, the user is introduced to some of the most commonly used tools in CADfix including easy-to-use GUI’s and the more powerful command line. The training also covers how to prepare the model for an EMA3D simulation, running the simulation, and some provided post-processing options. This training is a great place to start to learn how to effectively use CADfix and EMA3D.

 

Download Training Files

Aircraft P-Static

F22 model for Aircraft P-Static simulation and testing

By Anthony Supino

Aircraft Precipitation static (Aircraft P-Static) is a term used to describe interfering noise resulting from the redistribution of charge on an operating aircraft. As an aircraft moves through the air, it acquires charge until sufficient voltage levels are reached to initiate a discharge. This discharge may occur between different parts of the aircraft or between the aircraft itself and the external environment. The noise or “static” resulting from these discharges can cause interference to sensitive aviation equipment resulting in the possible loss of communicate or navigation capabilities for several minutes.

There are several areas in which EM simulation can support Aircraft P-static design and certification programs. The following gives some of the steps that are the most amenable to analysis or that require the most time of the electromagnetic effects groups involved. Full documentation for how to approach P-static mitigation is given in SAE ARP5672 “Aircraft Precipitation Static Certification”. Also useful is the recent article: “A Critical Review of Precipitation Static Research since the 1930’s” by Rod Perala, PhD.

See further down in this article for an example EMA3D simulation demo, including simulation CAD files, a step-by-step instruction document and a video describing every step.

1.     Discharger Sizing and Placement Simulation and Analysis

E-Field Plot for Aircraft P-Static Simulation

First, perform charging rate determination considering the mission profile from all sources, including: engine charging, ice crystals, cloud particles, dust, and other sources. This charging rate will determine the number and size of the dischargers.

Next, use the existing CAD model to perform EM field modeling to locate the optimal discharge locations based on maximum E-field enhancement (see the demo below).

2.     Specify parts and installation

Determine the specific model number and installation instructions (including tolerance and electrical bonding requirements) for each candidate discharger. Specify the installation location on the aircraft.

3.     Prescribe Surface treatments

Specify the physical properties of surface treatments for outer-mold-line locations in order to minimize P-static disruption to systems and to assist in discharge to the assigned wicks. Specify the thickness and location of necessary coatings. Discuss any needed bonding requirements in addition to any surface coatings.

4.     P-Static Antenna Optimization

Review the existing antenna locations to determine if there are improvements necessary due to P-static concerns and required wick placement. Full-wave EM simulation can estimate the fields or “noise” due to the discharges and how they couple to antennas.

Full Computational EM Example of Aircraft P-Static Simulation

Here, we provide CAD files, a step-by-step instruction document and a video describing every step. Contact EMA for more details or with any questions. The demo files can be downloaded from here. The video and instruction document are embedded below:


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EMI from a Slot in a Box

By Cody Weber and Bryon Neufeld

Benchmark Simulation Using EMA3D

It is important to demonstrate that EM simulation packages can reproduce measured data for problems of interest. EMI from a slot is a common EMC concern. This demonstration compares an EMA3D simulation to an existing measurement in the literature.

The electromagnetic interference (EMI) from a slot in a rectangular box has been explored using a FDTD technique and compared to measurements.[1] An FDTD simulation software, EMA3D,  has been used to analyze a similar problem and the results are presented herein. The simulation files, results and plotting scripts have been provided to assure the validity of the EMA3D modeling results.

EMA3D Model Setup

Mesh size: Δx = 1 cm, Δy = 0.5 cm, Δz = 1 cm
A thin wire with termination impedances of R1 = 50 Ω, and R2 = 47 Ω was used to model the source line (green line). A thin gap formalism was used to model the slot (blue line) with a width of 1 mm. Box surfaces (Lx = 22 cm, Ly = 14 cm, Lz = 30 cm) were modeled as perfect electrical conductors (PEC). A Gaussian pulse voltage source with amplitude 1 mV was used at the R1 end of the thin wire.
A box with a slot ready for EMI from a slot simulation

EMA3D Simulation Setup

A far-field electric field approximation was used to determine the electric field at a 3 m distance from the slot in the benchmark.[1] EMA3D has the ability to obtain far-field approximations similar to the ones performed in the paper. Because the problem is relatively small for the computing resources available, the actual electric field was computed at the 3 m distance. Only the y component of the electric field was considered.
This shows where the EMI measurement occurs from the slot

EMA3D Results Vs. Results in Benchmark [1]

 Comparison of EMI from a Slot experiment to simulation

Comparison of experiment to simulation

The plots demonstrate that the EMA3D simulation results compare well to the benchmark results. Every cavity-mode and slot generated resonance produced in the benchmark problem is captured in the EMA3D results for delivered power and electric field at 3 m.

Video Demonstration of EMA3D Modeling the Slotted Box

Instruction Document to Reproduce the Results

 

1.M. Li, J. Nuebel, J. L. Drewniak, R. E. DuBroff, T. H. Hubing, T. P. Van Doren, “EMI from Cavity Modes of Shielding Enclosures – FDTD Modeling and Measurements,”  IEEE Transactions on Electromagnetic Compatibility, Vol. 42, No. 1, pp. 29 – 38, Feb. 2000

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DO-160 Cable Susceptibility Test and Simulation

By Jennifer Kitaygorsky, PhD and Anthony Supino

Click here to download the training data files

In DO-160 chapter 22 (and sometimes chapter 20) testing, it is often advantageous to use simulation to help understand what is happening inside of cable shields and equipment. DO-160 test waveforms that are injected onto complex cable harnesses will induce currents and voltages on the pins at equipment interfaces. EMA3D is a useful tool in understanding what the pin levels are as a result of the transfer impedance of the cable while capturing the effects of cable shields, branches and multiple conductors.

We often find ourselves doing this type of simulation during design phases or after a test failure. The purpose is not to replace the required box testing; rather, it is to help reduce the risk of failure and to help determine the cause of failures.

This training shows a DO-160 type measurement of a 22 AWG twisted shielded pair, and compares the test results with simulation results.

This measurement is for training purposes only. In actual DO-160 testing, waveforms defined in the DO-160 document are typically used.

A double exponential current waveform resembling lightning component A, but with 400 mA amplitude, is injected onto the shield of the cable. The cable shield was grounded to an aluminum sheet placed 2 inches below the cable, such that the current path was from the cable shield to the aluminum sheet, back to the generator ground. The open circuit voltage (VOC) was then measured at the end of the cable opposite the injection point. For this configuration, the only way for any current and voltage to couple to the twisted pair inside the shield is through the shield transfer impedance. The schematic of the measurement is shown below. A full demo video of the test, test setup, and the simulation can be viewed below.

DO-160 test setup

 

And here is the training for how to create the model:

The simulation training and data files can be downloaded here. The data files from the measurement are named “measCurrent.dat” and “measVoltage.dat”. Once the simulation is completed, the results can be compared with the measurement. Please contact EMA if you have any questions about the test setup, test results, or the training manual.

CAD import + healing + simplification for EM analysis

 

An important part of working with actual CAD is being able to import the geometry to prepare for computer-engineering (CAE) and simulation. EMA3D uses CADfix in order to prepare for simulation. CADfix allows for automatic healing, defeaturing and simplification.

Please view the training document below to practice using CADfix for CAD to CAE workflow. The example problems are available for download here.

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EMA3D Training

ema3d main logo

EMA is pleased to provide free training in EMA3D, MHARNESSCADfix, and EMA3D for EMC. Please look at the demos below. In each case, EMA provides:

  • A document that lists every individual step and discussion of each procedure
  • Downloadable CAD geometry files so that you can repeat the exercise or extend to your specific application
  • A video in which an EMA analyst describes every step in the process

Here are the topics thus far:

Introduction to EMA3D and CADfix

Lightning simulation on a basic aircraft model
In aircraft development, significant resources are spent to ensure safety during a lightning strike. Experiments are very costly and it’s impossible to measure every interesting quantity at every location. With lightning simulations, a more complete data set can be taken (all field values can be known in any location). Simulation data can greatly help guide the designs and tests to demonstrate compliance with FAA regulations such as 25.981 (fuel tank ignition prevention).

In this training, a simple aircraft is created using basic geometry. The aircraft is created using CADfix and is prepared for an EMA3D simulation. The simulation case is a component A lightning strike on the wingtip and opposite wingtip detachment. In the process, the user is introduced to some of the most commonly used tools in CADfix including easy-to-use GUI’s and the more powerful command line. The training also covers how to prepare the model for an EMA3D simulation, running the simulation, and some provided post-processing options. This training is a great place to start to learn how to effectively use CADfix and EMA3D.

Model Simplification and Preparation for MHARNESS Co-simulation

This tutorial is a step-by-step demonstration on how to prepare and perform a full aircraft simulation. We go through how to simplify CAD geometry of cable-packs down to lines to be used in MHARNESS, and the steps to prepare a model for a co-simulation with EMA3D and MHARNESS.

MHARNESS is a transmission line solver that enables the user to simulate levels on individual electronics pins at equipment interface. MHARNESS requires special geometry to be present in the model in order to define where the transmission lines are to be located. This training goes through how to create this geometry from the CAD.

Aircraft P-Static

Aircraft P Static Simulation

Precipitation static (P-static) is a term used to describe interfering noise resulting from the redistribution of charge on an operating aircraft. As an aircraft moves through the air, it acquires charge until sufficient voltage levels are reached to initiate a discharge. This discharge may occur between different parts of the aircraft or between the aircraft itself and the external environment. The noise or “static” resulting from these discharges can cause interference to sensitive aviation equipment resulting in the possible loss of communicate or navigation capabilities for several minutes.

In this demo we provide an example EMA3D simulation, including simulation CAD files, a step-by-step instruction document and a video describing every step.

EMI from a Slot in a Box – Benchmark Simulation Using EMA3D

Comparison of EMI from a slot in a box experiment to simulation

Comparison of experiment to simulation

It is important to demonstrate that EM simulation packages can reproduce measured data for problems of interest. EMI from a slot is a common EMC concern. This demonstration compares an EMA3D simulation to an existing measurement in the literature. A full video and written demonstration are provided.

DO-160 Cable Susceptibility Test and Simulation

EMA presented this demo at EMC 2014 in Rayleigh, NC.

DO-160 test setup

This training shows a DO-160 type measurement of a 22 AWG twisted shielded pair, and compares the test results with simulation results.

This measurement is for training purposes only. In actual DO-160 testing, waveforms defined in the DO-160 document are typically used.

A double exponential current waveform resembling lightning component A, but with 400 mA amplitude, is injected onto the shield of the cable. The cable shield was grounded to an aluminum sheet placed 2 inches below the cable, such that the current path was from the cable shield to the aluminum sheet, back to the generator ground. The open circuit voltage (VOC) was then measured at the end of the cable opposite the injection point. For this configuration, the only way for any current and voltage to couple to the twisted pair inside the shield is through the shield transfer impedance. The schematic of the measurement is shown below. A full demo video of the test, test setup, and the simulation can be viewed at the link above.

Lightning Initial Attachment for Zoning

Lightning Leaders approach an aircraft

Lightning leaders near an aircraft geometry

This post describes the steps to perform lightning initial attachment for zoning. Lightning zoning for aircraft involves separating each aircraft outer surface area into a specific category based on its likelihood for lightning attachment, lightning sweep and lightning hang-on. The steps required are detailed s in SAE ARP 5414A: Aircraft Zoning. The task is divided into two sections:

  1. Determination of the initial attachment locations
  2. Zoning based on the ARP guidance using the attachment locations and the vehicle operating speeds at various altitudes

Radiated Susceptibility Analysis

CADfix interface of EMA3D. EMA3D for EMC to simulate EMC problems in avionics, including radiated susceptibility

EMA3D for EMC to simulate EMC problems in avionics, including radiated susceptibility

Radiated susceptibility analysis for electronics and avionics is an important aspect of electromagnetic environmental effects (E3) and electromagnetic compatibility (EMC) efforts.

The work involves:

  • Determining the environment or radiating emitter field levels. The source of emission may be external to the aircraft (HIRF/EMR) or from another known emitter on the platform.
  • Analysis or testing to determine how the fields couple to cables
  • Analysis or testing to determine how the fields couple directly inside electronics enclosures
  • Analysis or testing to determine if the electronics can continue to operate normally with the imposed fields

This training is intended to simulate how radiation from an antenna couples fields into enclosures and induces currents and voltages on internal elements

Aircraft Lightning Simulation

Full-wave simulation of current density on a tiltrotor

One of the key features of EMA3D and MHARNESS is the ability to simulate an entire platform and determine the levels on individual electronics pins at equipment interface. in this aircraft lightning simulation demonstration, we show you how to do each step of this process.

EMA3D version 4 includes features that no other EM software package has: the ability to perform a co-simulation with a transmission line solver with a special lightning component that has demonstrated compelling accuracy in determining internal pin transient control levels (TCLs).

This is a step-by-step demonstration of how to perform a full aircraft simulation. We discuss how to include integrated MHARNESS cables so that the cable harness can be co-simulated with EMA3D.

CAD import + healing + simplification for EM analysis

EMA3D allows for CAD to CAE workflow with automated defeaturing and repair

EMA3D allows for CAD to CAE workflow with automated defeaturing and repair

An important part of working with actual CAD is being able to import the geometry to prepare for computer-engineering (CAE) and simulation. EMA3D uses CADfix in order to prepare for simulation. CADfix allows for automatic healing, defeaturing and simplification.

More Training to Come

Don’t see the topic you want to explore? Contact EMA, and we will add your application to our demonstration list. We will be adding new topics constantly, so be sure to check back periodically.

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Lightning Initial Attachment for Zoning

By Jennifer Kitaygorsky

This post describes the steps to perform lightning initial attachment for zoning. Lightning zoning for aircraft involves separating each aircraft outer surface area into a specific category based on its likelihood for lightning attachment, lightning sweep and lightning hang-on. The steps required are detailed s in SAE ARP 5414A: Aircraft Zoning. The task is divided into two sections:

  1. Determination of the initial attachment locations
  2. Zoning based on the ARP guidance using the attachment locations and the vehicle operating speeds at various altitudes

EMA has applied its Finite-Difference Time-Domain (FDTD) solver of Maxwell’s equations (EMA3D) in the determination of primary attachment regions on air vehicles previously. The approach is to model a lightning leader in proximity to the vehicle with a time-domain buildup of charge for which the simulation can be run to steady-state.  At steady-state, the distribution of the surface normal electric field over the vehicle is characterized.

Regions of high electric field become of interest as the potential primary attachment points for the vehicle in the E-field modeling approach. It is possible to take advantage of the time-domain nature of the solution as it approaches steady-state to characterize the rate of increase in electric field (and charge) in the regions of interest. Those areas building to a peak charge most rapidly are considered likely candidates for early streamer formation and as primary attachment locations.

This post describes step-by-step how to perform the lightning initial attachments for zoning. You can download all the files needed to try this example here. If you would like to try a demo of the EMA3D Framework, contact us.

After the initial attachment points have been assigned, EMA3D CADfix is used to easily label each zone by color on a 3D model of the aircraft. It is exportable in a variety of formats, including 3D PDF. Contact EMA if you have any questions about how you can do this, or to hire EMA analysts to perform a zoning for your aircraft.

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Radiated Susceptibility Analysis

By Cody Weber

Radiated susceptibility analysis for electronics and avionics is an important aspect of electromagnetic environmental effects (E3) and electromagnetic compatibility (EMC) efforts.

The work involves:

  • Determining the environment or radiating emitter field levels. The source of emission may be external to the aircraft (HIRF/EMR) or from another known emitter on the platform.
  • Analysis or testing to determine how the fields couple to cables
  • Analysis or testing to determine how the fields couple directly inside electronics enclosures
  • Analysis or testing to determine if the electronics can continue to operate normally with the imposed fields

This training is intended to simulate how radiation from an antenna couples fields into enclosures and induces currents and voltages on internal elements. This analysis starts with a CAD drawing of the enclosure.

CADfix interface of EMA3D. Used here for Radiated Susceptibility Analysis

Demonstration of EMA3D CADfix interface for simulating  radiated susceptibility

Toward that end, EMA provides the following training example of how to properly model the field coupling into an electronics enclosure. This is a step-by-step guide on how to do the analysis in EMA3D with a written document, a video screencast and an example enclosure CAD file.

Download the instruction document and sample geometry here and view the video demonstration below:

Do you have questions or comments about this demonstration? Send us a message and we will respond quickly.

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