Developers of EllipTool® software for high performance systems optimization
Find Out MoreEllipTool® provides a framework for analysis and optimization of high performance optical systems. It is aimed primarily at the community of developers of orbiting observatories. It comprises a set of tools and modules that allow designers to rapidly assemble a system level model that combines models of multiple physical processes, perform analyses to assess system performance against requirements, and design and implement mitigation strategies to address deficiencies. Physical processes that can be modeled include structural dynamics and thermal distortion, optical performance, dynamic disturbance sources, control systems, and in general any processes that can be modeled with linear dynamics or specific classes of nonlinear behavior.
The analyst using EllipTool®
begins by importing component models, including structural
response data and optical models. Structural response data
are generally from a Finite Element model and can include
static displacements for thermal distortion, moisture
desorption, gravity release, and other static error
sources; and Normal Modes data for dynamic response
analyses. Optical models are represented in the form of a
Linear Optical Model (LOM) that computes optical responses
as a linear function of structural perturbations. Optical
responses can include Line-of-Sight error, Wavefront
Error, and beam displacement and angle on specified
surfaces. Model import brings in the data as well as
descriptive information including units and identification
of specific components represented in the models that
enables the definition of forcing function input
locations, response regions of interest, control sensors
and actuators, and interfaces between models. Using this
descriptive information, the analyst can rapidly and
easily create a state space model representing the
structural dynamics.
The analyst typically defines
control systems and disturbances within EllipTool® once
the structural and optical models are imported.
Once all component models are created, the analyst generates the system-level model, using the EllipTool® capability to automatically identify interfaces, match units, and couple models.
Dynamic Systems Analysis Language
Once the system level model has been created, the analyst uses numerically optimized tools provided within EllipTool® for performing dynamic analysis. Tools are provided to rapidly compute Frequency Response Functions (FRFs) and time simulations of systems with very high order (10,000 states) and input/output density (thousands of inputs and outputs). Analyses that would require hours or even days with standard algorithms can be completed in minutes. FRF and time data can then be manipulated with standard linear algebra tools such as multiplication, summation, differencing, determinants, singular values decomposition, and many others.
Parameterization
The analyst gains a significant and unique capability from EllipTool® in the form of the ability to create parametrrized state space models, where the system dynamics are explicit functions of selected parameters. Functions are available to create parameterizations of structural parameters such as stiffnesses, moduli, masses, and damping. Control system gains can also be parameterized. The analyst uses the parameterized model to find optimal parameter values, to find bounding values for setting requirements, and to compute response uncertainty as a function of parameter uncertainty. The parameterization enables the computation of gradients of the dynamic system responses, which facilitates sensitivity analysis, formal design optimization using nonlinear search routines,and model updating.
The power of the tool is enhanced by the ability to parameterize component models which, when assembled into the system model, automatically produce a parameterized system model.
The standard tool is augmented by a number of optional modules that provide additional out-of-the-box analysis capability for common tasks.
EllipTD®: Thermal Distortion
(Structural-Thermal-Optical Performance,"STOP")
The analyst uses the EllipTD® module to analyze optical responses to thermal perturbations, including the effects of alignments and correction mechanisms.
EllipJitter®: Dynamic Disturbance Analysis
The analyst uses the EllipJitter® module to analyze optical responses to dynamic perturbations, including reaction wheels and Control Moment Gyros (CMGs) that create gyroscopic moments as a function of wheelspeed. The tools facilitate the identification of critical modes that drive dynamic responses. The module also includes a number of models of disturbance sources that are of interest to space-based observatories, which can be augmented by the user.
EllipIVM®: Induced Vibration Disturbance Modeling
The analyst uses the EllipIVM® module to develop models of induced vibration disturbance sources, specifically aimed at spinning reaction wheels. The module creates a disturbance model that is a combination of a tuned model (FEM) representing wheel structural dynamics, and an empirical model of disturbance forcing harmonics and random noise.
EllipTMD®:Tuned Mass Damper Design
Tuned Mass Dampers (TMDs) are a powerful technology for adding targeted damping to structural systems in a space realizable and mass efficient form. The analyst uses the EllipTMD® module to determine the optimal sizing, placement, and frequency and damping tuning for TMDs.
EllipStepper®:Stepper Motor Modeling
The analyst uses the EllipStepper®
module to analyze the optical response of the system to
stepper motor actuation for antennae, solar arrays, and
instrument mechanisms, using parameterized models of
stepper motor disturbances in the time and frequency
domains. Microstepping, a technique that minimizes induced
vibration by commanding a sequence of smaller steps
between detents, is implemented in the model.
EllipPSF®: Point Spread Function and Optical Metric Analysis
The analyst uses the EllipPSF®
module to compute Point Spread Functions (PSFs) from
wavefront error data using a numerically efficient direct
integration method. By avoiding a Fast Fourier Transform,
the technique is faster, more memory efficient, and better
able to match the detail included in the PSF to the region
of interest. The module also includes PSF-based optical
response metrics such as Strehl ratio, Modulation Transfer
Function (MTF), and Encircled Energy. The analyst uses
the module to shorten development cycles by allowing
local design iterations to proceed without requiring an
in-line optical analysis.
EllipOptimization®: Systems Optimization Functions
The analyst uses the
EllipOptimization® module to conduct univariate parameter
studies, sensitivity (gradient) analysis, and parameter
optimization using a number of routines that compute
various response metrics and their gradients.
NASTRAN
The analyst uses the
Ellip2NASTRAN® module to read standard NASTRAN output
data (static displacements, Normal Modes, element
strain energies) in various formats (f06 files, punch
files, op2 and op4 files). The analyst can also read,
manipulate, and write bulk data files using tools provided
in the module.
Linear Optical Models
The analyst uses the Ellip2Optics®
module to mport and manipulate LOMs. The module includes
algorithms for computing the effects of alignments and
compensation mechanisms into the LOM, so that the LOM can
represent, for example, the optical response of a system
where the secondary will be aligned to achieve minimum
wavefront error.
Simulink®
The analyst uses the Ellip2Simulink® module to transfer dynamic models between EllipTool® state space form and a Simulink® time domain simulation. The Simulink® model can be used to analyze time responses, including nonlinear effects, and is also useful to visualize the system interconnections.
Dr. Carl Blaurock, the principal behind Elliptical Engineering, has over two decades of experience supporting NASA flight programs, including flagship missions such as the James Webb Space Telescope (JWST) and Wide Field Infrared Survey Telescope (WFIRST), and many others such as the Global Precipitation Mission (GPM), Ice, Cloud, and land Elevation Satellite 2 (ICESat-2), Landsat-8, Lunar Reconnaissance Orbiter (LRO), Neutron star Interior Composition Explorer (NICER), Global Ecosystems Dynamic Investigation (GEDI), and the Solar Dynamics Observatory (SDO); representing a total national investment of $15B. Dr.Blaurock is the recipient of the Goddard Space Flight Center 2007 Contractor of the Year award, and, in 2014, the NASA Exceptional Public Service Medal.
The name of the company derives from the following definition of elliptical:
of,
relating to, or marked by extreme economy of speech or
writing
We have developed EllipTool® to provide that same degree of economy in the development, analysis, and optimization of complex systems dynamics models.
If you're ready to learn more about
EllipTool® and how it can enable you to do more with less
effort, please contact us by telephone or email:
919-637-5883