Advances of Virtual Testing and Hybrid Simulation in Automotive Performance and Durability Evaluation

Shawn S. You; Dave Fricke

doi:10.4271/2011-01-0029

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.

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Advances of Virtual Testing and Hybrid Simulation in Automotive Performance and Durability Evaluation 2011-01-0029

SAE MOBILUS