Speaker 1: In this section, we
will build upon the static
analysis by creating a rigid
body motion study, to understand
the kinematics of the front
suspension system in further
detail, starting with an
assembly model, we can focus in
on the front right corner of the
vehicle and hide the mirrored
components. We'll section the
model using the front and right
planes to make It easier to see
the components, taking a closer
look at the suspension assembly.
We see that the double wishbone
arms in blue, uh, connected to
the chassis mounting tabs have
been included to mount the
orange bell crank rocker to the
wish bones and shock absorber.
Wishbone mounting points have
been represented, had simplified
ball and socket joints for the
analysis to allow for a full
range of motion. The physical
shock absorber spring has been
excluded from the assembly as
this can be represented as a
virtual simulation element using
the simple spring equation, but
can also consider fluid damping
thus negating the need to model
the geometry. We can also see
the purple rocker linkage. If we
rotate around the model and the
wheel assembly itself, hiding
the tire and wheel, we see a
simplified body representing the
design envelope for the upright
knuckle shown in yellow. The
brake caliper and hub axles are
mounted to this body, which will
be optimized in the next
section. All joint connections
are also modeled here to
streamline the motion study
setup. We'll un-hide the
component we
hid earlier by using a handy
little button on the assembly
toolbar. And this completes the
geometry review. We can test
wheel clearances and suspension
travel by moving the wheel to
ensure all components are mated
correctly. These mates will
automatically be converted to
motion study joints, avoiding
tedious manual setup to create a
motion analysis, navigate to the
assembly tab and insert a new
motion study. Ensure the motion
addin is enabled first if the
options are not visible. All
motion study tabs are shown at
the bottom of the viewport and
clicking on a study name will
split the pane and show a custom
motion specific feature tree. Be
sure to change the study type
from animation to motion
analysis for a full feature set.
This particular study has a
number of pre-applied conditions
which are listed. We can
calculate the response using the
toolbar option on the left and
add additional simulation
elements and conditions by
working from left to right.
Options to add motors and
actuators, Springs, dampers,
forces, contact and body forces
are available. We'll step
through the setup. Gravity is
applied to the global wide
direction, but this could be
modified and flipped to simulate
a constant and uniform
acceleration load. A virtual
spring connector has been
created with a linear spring
stiffness and two load bearing
face is selected. Damping can
also be turned on here, but we
have created an explicit damper
between the same two faces with
a
damping coefficient to control
this independently solid body
contact between the wishbone and
the upright has been set to
steel dry. And this is true for
both the upper and law, wish
bones we can extract. The
contact reaction force is
correctly using this method. And
these are listed in the motion
tree. A vertical force was added
to apply loading on the wheel to
simulate a bump impact. A custom
driving function of force versus
time was used. And the data has
been imported from an Excel
sheet. In this particular
instance, the acceleration data
was obtained by mounting a
mobile phone to the engine bay
of a vehicle near the shock top
mounts and capturing
acceleration data, using a data,
logging app. The acceleration in
the Z direction from the app
corresponded to the vertical Y
acceleration of the chassis.
This was imported directly into
Excel and rearranged by dividing
the acceleration by the mass
acting over one quarter of the
vehicle to give an approximate
force acting at the wheel.
Notably the vehicle, the data
was extracted from was much
larger than the formula student
chassis, but the analysis
methodology is still the same. A
small subsection of the data has
been extracted to show the
vibration loading for 0.5
seconds. We will use this data
in the motion study by importing
the raw data from a .CSV file.
The first column represents the
time in seconds and the second
column represents the force
experienced
in Newtons. This data is
imported into the force function
builder, and we can calculate
the motion. Notice how the wheel
responds to the dynamic input.
We can scroll down to the
results folder where results
will be stored clicking the X Y
plot. We can extract the wheels
linear displacement in the Y
direction over the loading time
and choose to show a vector
arrow graphic. In the viewport.
We are presented with a plot of
the linear displacement over
time and compare this back.
Ignore the displacement scaling.
As the input data was obtained
from a much larger vehicle.
Gravity is not enabled and not
all materials are applied to
components. Navigating back to
the results folder. A previously
created reaction force graph
shows the forces experienced at
the wheel knuckle upright, which
will be used in the next phase.
And the vector on screen shows
the force load in graphically
other plots that are available,
include energy pitch, yaw and
roll graphs, angular
accelerations and much more. The
Motion study properties control
many of the solver settings
needed for robust motion
simulation and include the
number of frames per second for
smooth animations. In this case,
400 frames over 0.5 seconds
equates to 200 frames per
second. And the number of
calculation points, precise
contact between pointed geometry
and complex components can be
used when the contact resolution
slider can not release an
adequate solution. More advanced
options control the solver
integration type with a
w stiff solver being better
suited for reducing errors,
improving accuracy and updating
solver constance at each step
size, which can be modified. We
can now take the forces we
obtained and import them into
the next phase