Minimizing the truncation error in assumed modes models of structures

The assumed modes approach is a widely used technique in modeling of distributed systems. Such models often consist of a large number of modes. For controller design purposes these models are simplified by truncating the modes that lie out of the bandwidth of interest. Truncation can alter zeros of the system. This paper presents a method of minimizing the truncation error by adding a second order term to the truncated model. This extra term is determined such that the in-bandwidth error is minimized in an optimal H/sub 2/ sense. The technique is extended to multivariable systems.