Introduction of Dyanamically Substructured Systems (DSS)

What is DSS

Dynamically substructured system (DSS) is used for dynamics testings. A DSS contains both numerical and physical components, which aims to provide a more realistic, real-time testing approach for dynamic systems than hitherto been possible. It enables full-size, critical components of a complete system to be physically tested in real-time, within a laboratory environment, whilst the remainder of the system is modelled numerically.

The benefits of DSS testing

The reasons for using this hybrid testing method can arise from two situations:

1. Some components of an emulated system are too difficult to be described mathematically, due to unmodelled dynamics or complicated nonlinearities; in this case, these components can be tested physically, so that inaccurate modelling is prevented during a testing.
2. Some components of an emulated system are inconvenient or expensive to be realistically tested within a laboratory environment (e.g. the bridge, wind tunnel, building); in this case, these components can be tested numerically, so that difficult or unrealistic physical tests can be avoided.

Applications of DSS

The applications of DSS testing can be found in various fields including civil engineering, aerospace and automotive, etc. Some examples are:

• Testing of part of a building on a shaking table to study its dynamics during earthquake.
• Testing of the aerodynamics of a car at a high speed.

DSS control problem

The performance of a DSS is evaluated by assessing if the difference between responses of the DSS and the target emulated system is small enough. This is usually hard to be assessed because the emulated system is assumed to be unavialable. However, this difference is reflected by the sychronization error of the interface signals between the numerical and physical substructures. The sychronization of the substurctures is the key control problem of a DSS and a high fidelity conroller is required to cope with the uncertainties and nonlinearties within the physical substructure. The control of a DSS can be viewed as a regulation problem measured disturbance rejection. Here the testing signal is viewed as the measured disturbance; the sychronization error is viewed as the output; some acutators attached to the physical substructure are used to provide input signals.

Examples

Example 1 - A quasi-motorcycle test rig.

Testing mode 1: the vehicle body with suspension struts is tested as the physical substructure; the front/rear wheels are tested as the numerical substructure.

Testing mode 2: the vehicle body with suspension struts is tested as the numerical substructure; the front/rear wheels are tested as the physical substructure.
back to top

Example 2 - A small scale train test rig.