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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.

The typical approach for body load simulation during 7-Post testing has been to match body motion and forces for a known suspension setup condition, and then to maintain the applied body loads for subsequent tests with different setups. However, in order for the test to remain valid across a wide range of vehicle setups, the applied body loads may need to be varied to match the specific test car. A significant component of the body load comes from aerodynamic downforce, which can be calculated during a 7-Post test based on vehicle body position and previously recorded wind tunnel test data. This paper discusses a method to generalize the 7-Post inputs by updating the aerodynamic force content automatically during each test run. The paper begins by discussing validation of an active aerodynamic force control scheme on a MTS 320 7-Post road simulator with a NASCAR Sprint Cup vehicle.

Hybrid vehicle simulation methods combine physical test articles (vehicles, suspensions, etc.) with complementary virtual vehicle components and virtual road and driver inputs to simulate the actual vehicle operating environment. Using appropriate components, hybrid simulation offers the possibility to develop more accurate physical tests earlier, and at lower cost, than possible with conventional test methods. MTS Systems has developed Hybrid System Response Convergence (HSRC), a hybrid simulation method that can utilize existing durability test systems and detailed non-real-time virtual component models to create an accurate full-vehicle simulation test without requiring road load data acquisition. MTS Systems and Audi AG have recently completed a joint evaluation project for the HSRC hybrid simulation method using an MTS 329 road simulator at the Audi facility in Ingolstadt, Germany.