MMM Tour: OUTPUT
MMM calculates over 100 engineering vehicle parameter outputs at up to 2500
combinations of steering wheel angle and vehicle sideslip angle. These outputs
are normally viewed with the MMM post-processing programs, but for detailed
study and debugging they are also written to an ASCII output file. For a
listing of outputs recorded by MMM, click
The fundamental graph constructed from MMM output is the Force-Moment Diagram.
One such diagram, in this case a CN-AY diagram, is shown at right. This diagram
reflects the entire maneuvering envelope for linearly and angularly
accelerating the vehicle. MRA has a vast amount of experience interpreting
Some of this interpretation, analogous to results obtained from skidpad tests,
has been included in the post-processing. These include plots of understeer
gradient, steering sensitivity, stability index, trimmed steering wheel angle,
trimmed vehicle sideslip angle and control gain, among others. Representative
plots are shown below.
A very useful feature of the MMM post-processing is the "Friction Circle"
program. This program allows the user to navigate a cursor around the
Force-Moment Diagram and examine the corresponding vehicle state. One such
"snapshot" is shown below.
This graphical and numeric representation of the vehicle presents the following
information at any point of interest on the Force-Moment Diagram:
Vehicle speeds, linear and angular
Vehicle steer and sideslip angles
Individual tire parameters:
Steer angle, slip angle, inclination angle
Ride position (jounce/rebound)
Tire usage (percent of maximum force capability in use)
Deflections due to compliances
MRA has developed other post-processing techniques to obtain an additional
information from the MMM output. One such capability is "trim change analysis".
This focuses on how the stability and control of the vehicle changes when the
longitudinal trim of the vehicle is changed (as in dropped-throttle, braking,
etc.). Another technique uses MMM data to approximate transient vehicle
MMM is a powerful tool to study, analyze and troubleshoot the "big picture" of
vehicle stability, control and handling. Its unique solution technique quickly
and efficiently provides a wealth of information not easily obtainable from any
other type of simulation.
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