Duffing equation

The Duffing equation is a non-linear second-order differential equation used to model certain damped and driven oscillators. The equation is given by

\ddot{x} %2B \delta \dot{x} %2B \alpha x %2B \beta x^3 = \gamma \cos (\omega t)\,

where the (unknown) function x=x(t) is the displacement at time t, \dot{x} is the first derivative of x with respect to time, i.e. velocity, and \ddot{x} is the second time-derivative of x, i.e. acceleration. The numbers \delta, \alpha, \beta, \gamma and \omega are given constants.

The equation describes the motion of a damped oscillator with a more complicated potential than in simple harmonic motion (which corresponds to the case β=δ=0); in physical terms, it models, for example, a spring pendulum whose spring's stiffness does not exactly obey Hooke's law.

The Duffing equation is an example of a dynamical system that exhibits chaotic behavior. Moreover the Duffing system presents in the frequency response the jump resonance phenomenon that is a sort of frequency hysteresis behaviour.

Parameters

Methods of solution

In general, the Duffing equation does not admit an exact symbolic solution. However, many approximate methods work well:

In the special case of the undamped (\delta = 0) and undriven (\gamma = 0) Duffing equation, an exact solution can be obtained using Jacobi's elliptic functions.

External links