04-02-2013, 11:30 AM
GETTING STARTED WITH LOTUS SUSPENSION ANALYSIS
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Introducing Lotus Suspension Analysis
Overview
This chapter introduces you to the Lotus Suspension Analysis Tool and
explains the normal uses for it. It also introduces the tutorials that we’ve
included in this guide to get you started working with Lotus Suspension
Analysis (LSA).
What is Lotus Suspension Analysis?
LSA is a design and analysis tool that can be used for both the initial layout of a
vehicle suspensions hard points, and also the design and orientation of suspension
bushes for the tuning of the compliant behaviour.
Models are created and modified through a 3d-viewing environment. This allows
hard points and bushes to be ‘dragged’ on screen and graphical/numerical results
updated in ‘real time’. A template-based approach to the modelling allows users to
create their own suspension models, supplementing the ‘standard’ suspension
templates provided.
Normal Uses of Lotus Suspension Analysis
LSA is used by both designers and analysts alike for the layout of the suspension
hard point positions, in order that the required kinematic behaviour is achieved. Any
number of results can be displayed graphically, (e.g. Camber angle, Toe angle),
against bump motion, roll motion or steering motion. These results are updated in
‘real time’ as the suspension hard points are moved. The inclusion of compliant
bushes to the kinematic model allows the tuning of bush properties to be carried out,
to achieve required compliant response for items such as lateral force steer.
Overall Concepts
LSA has two main display and analysis modes, 2D and 3D, and it is possible to
import a 2D model into 3D.
Suspensions can be articulated in individual bump/rebound, roll and steering modes
or a combination mode that allows all three articulation types to be mixed. The
steering modes are relevant to the 3D mode only.
LSA uses templates to identify specific 3D suspension types. These templates define
the number of parts, the number of points and connectivity of the parts. A large
number of ‘standard’ templates are include with the installation, whilst users can
create their own or modify existing ones to model kinematic suspension types not
catered for.
Coordinate system
The LSA co-ordinate system is a right-handed system the origin of which must be in
front of the car and coincide with the vehicle longitudinal centre line.
Y-axis is across the car track, and the +ve direction being towards the right side
when sitting in the car. Suspensions can be defined as right side or left side as
required.
X-axis is along the vehicle wheel base and positive toward the rear of the car.
Z-axis is the vertical height and positive upwards.
When inputting suspension hard point data you must ensure that all co-ordinates are
consistent with the origin you have selected and be aware that all suspension hard
point output generated by LSA will be relative to that origin. The only restrictions are
that the X-Z plane must pass through the centre of the car and the origin must be in
front of the car. The co-ordinate system origin need not be coincident with the
ground plane.
About the Tutorials
The remainder of this guide is structured around a series of tutorials that introduce
you to the features of Lotus Suspension Analysis. Each tutorial builds on what was
learnt in those before it and are thus linked such that the user should work through
them in the order presented. The essential steps required to complete the tutorial
have been bulleted as shown below.
Starting the Application
To start Lotus Suspension Analysis from the main Start menu, point to Programs
and then Lotus Engineering Software, then Lotus Suspension Analysis
(Interactive). If the program fails to start or the menu item is missing from your start
menu, firstly confirm that the software has been installed correctly. You can browse
for the application directly, the executable file name is Shark.exe. As the program
starts, the start up ‘splash’ screen will be displayed, before the main application
window is opened.
Displaying Graphical Results
Graphs are used to display analysis results for any of the calculated results. To open
a graph, select Graphs / New-Open. The created window will show the current model
results for a particular parameter, e.g. camber angle. To change the displayed
parameter for a particular graph select the graph with the right mouse button and
pick the required parameter from the displayed list. The right mouse menu also
contains options for setting axis scales and general viewing options such as zoom
and autoscale.
Any number of graphs can be open at the same time, the positions and sizes of
which can be modified and saved by the user for future use. Some exporting options
are also available, as export to Excel…
Displaying Text Results
The text results for the currently defined suspension model can be displayed in a
scrollable text window, Results / Formatted SDF… This lists an echo of the input
data and tabulated/headed suspension derivatives. This provides a convenient
reporting medium for numerically summarising the suspension properties.
Saving Data Files
Models can be saved in the conventional way using the File / Save or File / SaveAs
menu items. You will always be warned about overwriting existing model files. Data
files will include all suspension hard point data, compliant bush properties and model
parameters. What it does not necessarily include is the template definition. A data
file can refer to the template via an entry number, if the 'include User Templates in
Data File' option is not checked. For further information on the definition and storing
of suspension templates, see the template sections in this document.