A generalised power-law formulation for the modelling of damping and stiffness nonlinearities

In this paper, a single-degree-of-freedom dynamic model is described, with displacement- and velocity-dependent nonlinearities represented by power laws. The model is intended to support the dynamic identification of structural components subjected to harmonic excitation. In comparison to other analytical expressions, the data-driven estimation of the nonlinear exponents provides a large versatility, making the generalised model adaptable for a wide number of different nonlinearities in both stiffness and damping. For instance, the proposed damping formulation can naturally accommodate air drag (quadratic) damping as well as dry friction. Differently to purely data-driven methods (e.g. black boxes), the obtained model is fully inspectable. The proposed formulation is here applied to the large oscillations of a prototype highly flexible wing and fitted on its steady state response in the frequency domain. These large-amplitude flap-wise bending oscillations are known to be affected by nonlinearities in both the stiffness (nonlinear hardening) and the velocity-dependent damping terms. The model is validated against experiments for different structural configurations and input amplitudes, as both these nonlinearities are energy-dependent

Dynamic nonlinear behavioral modeling and adaptive predistortion for RF transmitters

Motivation -- Nonlinear dynamic behaviour, two-and three-box models -- Objectives and outline of the thesis -- Two-Box models, de-embedding nonlinearities and dynamic memory effects -- Transmitter prototype -- Hammerstein and Wiener model construction -- Three-box oriented nonlinear model -- Three-box model's two-stage identification procedure -- Adaptive predistortion construction using single tone signal -- Hypothetical model and adaptive predistortion -- Construction of the complete predistorted system with a two-box model -- Complete predistorted system and linearization validation with CDMA signal