Unstable nonlinear systems often display an oscillatory behaviour that can be analysed in an approximate manner using some frequency‐domain techniques employed in linear systems analysis. The nonlinear part of the system usually provides an energy dissipation mechanism, such that the response of the unstable linear subsystem does not tend to infinite magnitudes, but instead remains in a bounded, constant amplitude oscillation called a limit cycle. The describing function analysis consists of a solution for the frequency and amplitude of the limit‐cycle oscillation (LCO). A typical aeroservoelastic (ASE) system can exhibit nonlinear oscillatory behaviour. The concept of absolute stability of passive feedback systems with a static nonlinearity is very useful in the design of stabilizing controllers. It is based on the application of Nyquist‐like stability criteria to nonlinear feedback systems. The uncertain linear parameters and the nonlinear operator driving the aeroelastic system can be handled by using a structured uncertainty model.
Nonlinear Oscillatory Systems and Describing Functions
Adaptive Aeroservoelastic Control ; 203-216
2016-04-04
14 pages
Article/Chapter (Book)
Electronic Resource
English
Multiple-input describing functions and nonlinear system design
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