Glossary of Control Engineering Terms - U
Under-Damped A linear system that has overshoot is said to be under-damped. This applies to 2nd-order or higher-order systems.
Unmodelled Dynamics: The real world is not simple or linear. Models will only ever be an approximation and be of a lower order than the real processes. It is important to model the essential dynamics and to some have some knowledge (or bound) of what was not modelled such that the controller will be able to cope with the unknown.
Unstable: A system is unstable when oscillations persist or grow. There are rigorous definitions of stability for linear systems - if any pole of a system has a positive real part then the system will be unstable, which leads to features on the frequency response plots (Bode, Nyquist and Nichols). For nonlinear systems it is much more difficult to define instability rigorously.
Glossary Index
[A], [B], [C], [D], [E], [F], [G], [H], [I], [J], [K], [L], [M], [N], [O], [P], [Q], [R], [S], [T], [U], [V], [W], [X, Y, Z],
Suggestions for additional entries or corrections?
Email us here.
Disclaimer
All of the information in this glossary has been carefully compiled and we believe it to be accurate. However, since any such definitions need to be placed in the context of specific applications, we assume no liability for the usage of information contained in this glossary.
