The Altair Multi Body Solutions 2019 release comes with new functionalities and
several enhancements. This version consists of the following highlights:
Optimize mechanisms with MotionSolve
Topology Viewer
Multi-Disciplinary tools
Leaf Spring Builder enhancements
New Full Vehicle Events
Enveloping Tire Contact
MDL Library Update Notice
Other enhancements
Resolved issues
Optimize Mechanisms with MotionSolve
Multi-body systems can now be optimized directly through MotionSolve. The 2019
version comes with an optimization capability native to the solver, all within the
MotionView environment. It uses MotionSolve’s Design Sensitivity Analysis (DSA) for
calculating sensitivities for use in gradient based algorithms. This is coupled to
SLSQP, a well known gradient based optimization algorithm.
To assist with the MotionSolve optimization, the following new features are available:
MotionSolve Python API
A python library in which the optimization problem is expressed. A model
can be built and executed using this Python library. The rich set of
functionalities available in Python and its application libraries can be
easily integrated with MotionSolve capabilities to provide an open,
extensible and incredibly powerful set of multi-body simulation
capabilities.
You can export a MotionView model to Python format as follows from the
File menu (File > Export > Solver Deck). You can also run simulations from the
Run panel using this file.
Guides you through the entire optimization process in MotionView by
enabling you to select design variables, create responses, define
objectives and constraints, solve the optimization problem, and review
results.
The new Multi-Disciplinary Tools can be used to help you easily build analytical
models for certain sub-systems, such as cams and gears, along with other utilities
that work across different application such as HyperMesh and HyperGraph.
The Multi-Disciplinary Tools can include an analysis to extract loads for all types
of forces, and imported in HyperMesh. In HyperMesh, the Multi-Disciplinary Tools
provides utilities to transfer CAD, mesh, lines, and nodes to MotionView.
Leaf Spring Builder
Canvas view controls
You can now pan, zoom, and fit the view of leaf shapes on the canvas in
the Leaf Spring Builder. You can also save hard copies of the leaf
shapes to a variety of graphic file formats including
.jpeg, .png, and
.pdf.
Friction option added to Contact Properties
The Friction option has been added to Contact
Properties, which allows you to specify different coefficients of
friction for different contacts. In previous releases, the friction
properties you defined on the General tab were employed for all
contacts.
Enter loaded leaf shapes
The Leaf Spring Builder now supports entering leaf shapes in the loaded,
design position. Often CAD for vehicles shows the leaf springs in the
loaded, design position rather than in a free position. To allow for
easy creation of a leaf spring model from CAD data, the Leaf Spring
Builder now supports the design shape condition. Once you enter the
loaded leaf shapes and the axle loading, the Leaf Spring Builder will
distribute the axle load among the leaves to produce a spring model that
you can use directly in the vehicle.
Points orient Leaf Spring Beam elements
Beam elements are now oriented using MotionView points, allowing you to
easily modify the shape of a leaf in MotionView by moving the points. In
previous releases, beam elements were oriented using Euler angles.
Changing the leaf shape in MotionView required you to modify the point
locations and the beam Euler angles.
Support for non-rectangular leaf sections
You can now enter a radius for leaf spring cross-sections. The Leaf
Spring Builder considers the radius when computing the beam mass and
area moments of inertia Ixx, Iyy, and Izz. Using a non-zero radius will
have a lower mass and lower bending stiffness compared to a rectangular
section (radius = 0). Figure 2.
New velocity output for leaf contacts
The translational velocities used when calculating inter-leaf and tip
liner contact forces are now output. In previous releases, only
displacements were output. The F2, F3, and F4 channels are the X, Y, and
Z displacement. The F6, F7, and F8 channels are the X, Y, and Z
velocity. The Z direction is the normal contact force, while X and Y are
the in plane directions for friction.
Create inter-leaf contact between leaves that are not immediate
neighbors
Leaves that are not neighbors in the stack which overlap along the
length of the spring with the potential for contact are now recognized,
and appropriate interleaf contacts are created. In previous releases,
overlap was not recognized.
Build leaf springs when the spring seat is not parallel to the
x-axis
You can now build leaf spring models when the spring seat is not
parallel to the x-axis. In previous releases, the leaf shape data you
entered required the x-axis to be parallel to the spring seat where the
axle clamps to the spring. Once imported into MotionView, you then
rotated the leaf-spring, so the spring seat was not parallel to the
x-axis. This was inconvenient when, for example, your leaf shape data
was in vehicle coordinates and the spring seat was not parallel to the
vehicle’s longitudinal axis. Figure 3.
Contact properties parametric to datasets in the leaf spring system
In previous releases, if you had leaf spring system loaded in MotionView
and wanted to change the contact properties, you had to edit the contact
properties for every contact or return to the Leaf Spring Builder and
modify the properties, and then rebuild the leaf spring system.
The parameters for each contact in MotionView are now parametric to
contact property datasets, and the contact property datasets are
children of the leaf spring system. Modifying contact properties in
datasets changes all of the contacts that parametrically depend on those
properties.
Build hockey-stick style leaf springs
You can now build leaf springs with non-planner leaf shapes, commonly
known as hockey-stick-style leaf springs. The leaf spring builder now
accepts x, y, z coordinates as input for leaf shape points.
Locate leaves using reference markers
Each leaf of the spring is now located by a reference marker in the
parent MotionView leaf spring system. Moving the reference marker
enables you to move the entire leaf.
Distribute inter-leaf contacts equally to the front and rear
You can now create inter-leaf contacts that are distributed equally to
the front and rear of the axle. In previous releases, you had to switch
contacts from front to rear to place contacts at the rear of the
axle.
Select leaf tip contact properties
You can now select contact properties for leaf tip contacts. The Leaf
Builder automatically creates non-master-leaves for leaf contacts, and
previously used default Metal-Metal contact properties. The interface
now supports selecting any contact properties the leaf property file
contains.
Test using SAE J510 procedure
Simulating the SAE J510 test procedure is now supported. In the SAE J510
test the shackle is removed, the spring is inverted with the eyes facing
downward, and was supported vertically but allowed to spread. Vertical
force is applied at the spring seat via a fixture to stroke the spring
and the force deflection curve recorded.
In the Leaf Spring Builder, gravity is inverted instead of inverting the
spring. Figure 4.
Full Vehicle Events
nPost Shaker event
An nPost Shaker event can now be added to any vehicle. Posts can be
coupled directly to the spindles or via spring-dampers to model tire
stiffness. Input force or displacement signals can be obtained from
.dac, .rsp,
.rpc, or .csv files to the
posts, and simulate the vehicle’s response to the input to assess
vehicle ride or component loads.
For models employing the AutoTire entities, the event automatically adds
a post for each wheel-tire in the model. For models not employing
AutoTires you can manually add any number of posts. The event also
supports adding auxiliary post for applying aerodynamic or other loads
directly to the vehicle chassis.
Use the Road Course Drive event to simulate a vehicle driving on a road
of your choice and assess vehicle dynamics, ride, or loads. You can
select the road to drive the vehicle over, a path for the vehicle to
follow, and a velocity profile which may be constant or specified by a
curve of speed verses distance traveled.
The path you select for the vhecile to follow can be extracted from the
road data file or specified by a curve.
The View Report option has been added to enable
you to generate a report for each full vehicle event that consists of
plots and an animation for the event.
Use the View Reports > Overlay option to plot results from multiple simulations in the
same window.
For more information, see View Reports. Figure 6. Event Report with Plots for Multiple Simulations
Enveloping Tire Contact
FIALA Tire model enhanced with Elliptical Cam Contact model
The FIALA tire model now supports an Elliptical Cam Contact model. The
Contact model is based on the Elliptical Cam Contact method described in
Pacejka’s Tire & Vehicle Dynamics Book. 3rd Edition (ISBN
978-0-08-097016-5).
The model lengthens force response to obstacles yielding more realistic
results than the typical point-follower contact method. This method
works with 2D, OpenCrg, and 3D Spline road data files.
For more information, see Elliptical Cam Contact
Model. Figure 7. Point Follower Contact vs. Elliptical Cams Contact
MDL Library Update Notice
Steering system models included in the MDL car and light truck library and
the heavy truck library will be updated in the 2019.1 release to remove the
dummy bodies. The full vehicle and half vehicle events will be modified to
not expect the dummy bodies in the steering system. The dummy bodies were
added to support computing Static Design Factors during suspension analyses
using ADAMS; however, the dummy bodies have caused user confusion and are
not required by MotionSolve.
The 2019.1 release will include a model update utility for removing the
dummy bodies from existing models created with the MDL Library steering
system. In addition, half vehicle models created from the library will not
directly support computation of static design factors using ADAMS.
Other Enhancements
MotionView
Calculate CG and inertias in the CG Inertia Summary tool
The CG Inertia Summary now calculates CG and inertias in any general
reference frame. CG can be calculated from any point, and inertias can
be calculated at any point in the model.
Import SLK files into the Data Summary tool
The SLK file can be exported from the data summary, modified in an excel
spreadsheet, and then re-imported. Expressions in the data (up to 255
characters) is also exported, thereby preserving the parametric relation
between entities. An option to export evaluated values instead of
expressions is also available.
Ease of creation of system instance
Using the Copy and Paste options, a new instance of a system can be
easily created. The new instance shares the definition with the original
instance from which it was copied. This functionality is applicable for
all definition-based entities such as Analysis, Datasets and Templates.
Any modification of the definition of the shared instance may break the
sharing based on the Create a separate definition when modifying a
shared instance settings access from Tools > Options > Build Model.
Default run directory
A setting under Run panel > Simulation Settings > General tab > Default location for solver run files now offers the ability to specify a
default folder for all solver runs. This information is stored in the
model and will be available for subsequent model load.
Interface node list file in Flexprep
A list of interface nodes can be provided as a text file in the Flex
Prep tool. The text file can contain the node numbers separated by
commas or spaces. The node numbers can be spread among multiple
lines.
Flexbody damping ratio per mode
Damping ratios can now be assigned to modes individually in the
Flex Body – Modes dialog.
Single RPC file from Fatigueprep
By default, Fatigueprep hence forth will generate a single RPC file
containing all channels. An option is available to create separate files
per channel.
Friction on universal joints
An option to specify Both as a choice for Rotation constraints has been
added for friction on universal joints. With this option, friction can
be applied on both yokes simultaneously.
Import contact entity in ADM
A contact entity present in the ADM solver deck can now be imported as
an equivalent contact entity.
MotionSolve
Linearization of model about a non-steady state operating point
Several enhancements have been made to the solver such that the eigen
solution obtained when linearizing a model about a non-steady state
operating point are more robust.
Improved threshold for matrix balancing.
Improved calculation of the B matrix.
Updated algorithm for choosing independent coordinates.
Addition of extra rotational coordinates to all bodies in the
mode.
Gyroscopic effects in linear analysis
Retrieving gyroscopic effects when performing a linear analysis becomes
important when analyzing rotating systems. MotionSolve can calculate eigen-solutions that
consider gyroscopic effects for rotating systems and compute “partial”
or “full” gyroscopic effects when linearising a rotating system.
Partial: Implies that the angular
momentum term is held constant when computing
the solution. Here, is the 3x3 inertia matrix of the
body in a body-fixed frame and
is the angular velocity of the body in that frame. The
results from using this approach will typically match reference
results from OptiStruct for the same
system. This is the default used by the solver.
Full: Implies that the angular momentum
term described above is not treated as constant when computing
the solution.
You can switch between these two options (or disregard the
gyroscopic effects entirely) within the
<Param_Linear> model/command attribute.
<Param_Linear
gyroscopic =
Description
NONE
No gyroscopic effects are included in the linear
solution.
PARTIAL (default)
Angular momentum term is held constant (see
Partial description under Enhancements).
FULL
Angular momentum term is considered variable (see
Full description under Enhancements).
Parasolid support
MotionSolve now supports a newer version of
Parasolid, v. 30.0.185. This version
is consistent with what is used in MotionView to enable seamless simulations.
MotionSolve Verification Manual
The 2019 release contains a set of 12 models spanning kinematics,
dynamics, static, and linear analyses that serve as verification
problems for the MotionSolve solution. Documentation for these models is
added to the product help and the models are available in the product
installation.
Known Issues
The following known issues will be addressed in a future release as we continuously
improve performance of the software:
In certain cases, the right-click context menu may have longer loading
times.
Resolved Issues
MotionView
Export MDL Snapshot option in the Run panel is not saved in the MDL.
CADGraphics – Changing the filename erases values set in the Location
tab.
Check Model does not compute correct number of degrees of freedom for flex
bodies and NLFE bodies.
Suspect data indicates bodies that derive properties from graphics with
zero/negative mass.
Colors from the ColorMaterial property list are not read correctly into
MotionSolve XML.
Changing an FEM file in the File Graphics results in distorted
graphics.
Data in the Curve panel is not retained when changing from values to
File/math and back to values.
Cut and paste of CADGraphics in a system results in an erroneous file
path.
Application hangs when archiving a model with Templates.
Loads are not exported correctly for connections that have an origin at a
Global Origin.
Exporting a model containing entities that refer to deactivated entities
does not result in an error.
An error does not display when a connection refers to the same body.
The option to write MAF during export saves into the MDL.
Saving a model after changing a joint type that supports initial conditions
(Cylindrical, Revolute, Translation) to a different joint type results in
errors when opening the model.
The Help button accessed from Tools > Options does not work.
The max step size option in the Contacts panel, Advanced tab cannot accept
values greater than 1.0.
MotionSolve
In some cases, simulations involving modeling elements attached to the
ground body would give incorrect results or even fail. These sets of issues
have been fixed by modifying the way the grounded body is treated in
MotionSolve.
Applying rotation on a joint that is connected to a flexible body.
Saving and loading models containing CDTire, such that there are no failures
or discontinuities at the point of save/load.
For noise in tire forces dependent on an axis of rotation, the solver now
switches the Euler angles based on which axes of wheel body aligns with the
axis of rotation. This change eliminates the numerical transience, so that
choice of axes for the wheel body no longer affects the quality of the
results.
Noise reduction in inputs when fed to Control_SISO
modeling element.
The seventh parameter in the SWEEP function, the interval
over which the function becomes fully active, is now consistent with the
definition of the function.
