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Advances of Virtual Testing and Hybrid Simulation in Automotive Performance and Durability Evaluation
Abstract:
Virtual testing is a method that simulates lab testing using
multi-body dynamic analysis software. The main advantages of this
approach include that the design can be evaluated before a
prototype is available and virtual testing results can be easily
validated by subsequent physical testing. The disadvantage is that
accurate specimen models are sometimes hard to obtain since
nonlinear components such as tires, bushings, dampers, and engine
mounts are hard to model. Therefore, virtual testing accuracy
varies significantly. The typical virtual rigs include tire and
spindle coupled test rigs for full vehicle tests and multi-axis
shaker tables for component tests.
Hybrid simulation combines physical and virtual components,
inputs and constraints to create a composite simulation system.
Hybrid simulation enables the hard to model components to be tested
in the lab. As a result, it greatly reduces the requirement for an
accurate analysis model and increases the chance for obtaining more
accurate results.
Mechanical Hardware-in-the-Loop? (mHIL™) is one of the hybrid
simulation approaches. It has been developed to enable actual
physical components to replace selected components for
"Real-Time" vehicle dynamic simulation. In this approach,
the virtual to physical coupling is accomplished in
"real-time" allowing an accurate vehicle dynamics
simulation to be conducted in a hybrid environment. The
disadvantage of this approach is that the "real-time"
requirement poses significant constraints on the model and test
rig.
To address the limitation of real-time techniques, an
alternative technique, Hybrid System Response Convergence (HSRC),
has been developed. The HSRC method uses an iterative approach to
develop a solution that satisfies the equations of motion for the
hybrid system. The iterative approach allows the physical and
virtual systems to run sequentially as open-loop systems, rather
than simultaneously, thus avoiding the requirement to run in
real-time. The disadvantage of this method is that an iterative
approach is more time consuming.
Another approach addressing the limitation of real-time is to
use a software named OpenFresco and a predictor-corrector algorithm
to connect dynamic analysis software and a test system. If the
solving speed cannot meet the requirement of real time, the
predictor-corrector algorithm slows down the actuator to allow more
time for the model to be solved. This approach is called soft
real-time hybrid simulation. The disadvantage of this approach is
that it still requires the hybrid simulation to be conducted at the
near "real-time" speed.