Model-in-the-Loop Testing

Abstract

Physical testing is used extensively to characterize mechanical systems. However, in many cases, mathematical models are now available that adequately describe the behaviour of part of the test specimen. Thus, test systems can be conceived which split the specimen into a physical part, and a virtual part, i.e. a real-time computer simulation. This has the potential to enhance convenience and reduce cost. The term ‘model-in-the-loop’ (MiL) has been used in the automotive industry to describe this concept. In this paper, a general framework for MiL system analysis is described. Two detailed examples are given. These concern the integration of numerical aerodynamic and tyre models into car test rigs. In the first case, the analytical results are validated by data from a real system. It is clear that particular demands are placed on the actuation and sensing systems if the numerical and real parts of the specimen are to interact correctly to give a realistic response for the complete system. Acceptable realism is achieved in the case of the aerodynamic model example. However, the results are less satisfactory in the tyre model example where both actuator response and sensor noise are limiting factors.