diff --git a/chaos/report/report.tex b/chaos/report/report.tex index 408d114..611c7df 100644 --- a/chaos/report/report.tex +++ b/chaos/report/report.tex @@ -83,30 +83,18 @@ A 2-dimensional phase space is a useful environment in which to identify the cha \end{figure} \subsection{Poincar\'{e} Map} - A Poincar\'{e} section is a 2D phase space cross-section, in this case corresponding to the repetition of a certain period, such as the natural or driving period of a forced pendulum. One draws a map between each successive point to create a Poincar\'e map, which is a useful representation of a system's behaviour in phase space. + A Poincar\'{e} section is a 2D phase space cross-section; in the case of the driven pendulum, the cross-section at a phase $\phi$ from the forcing term. One draws a map between each successive point to create a Poincar\'e map, which is a useful representation of a system's behaviour in phase space. A poincar\'e section of the driven pendulum model is shown in figure \ref{fig:model_driven_poincare}. An undriven and undamped oscillator will always return to the same point after one period, so a Poincar\'e map sampled using the period corresponding to the oscillator's natural frequency will consist of a single dot. The existence of multiple points at the same phase indicates chaotic motion. - An undriven and undamped oscillator will always return to the same point after one period, so a Poincar\'e map sampled using the period corresponding to the oscillator's natural frequency will consist of a single dot. + \begin{figure} + \includegraphics[width=6.5in]{model_driven_poincare.png} + \caption{Poincar\'e section of the damped and driven pendulum from figure \ref{fig:model_driven_phase} at $\phi=0$. Several dots are observed at this sampling phase, so the motion can be deemed chaotic.} + \label{fig:model_driven_poincare} + \end{figure} - - - - - - - - -\section{Chaos compared against Randomness} +\section{} \label{sec:reverbmap} -A random variable has no discernable pattern in its output. If a variable has a random response as a function of time, then it will appear as a random scatter in both the time domain and in phase space. A random response to the position coordinate is plotted in figure \ref{fig:random_phase}, in phase space. The random character can be see in the fact that the distribution of first-derivative responses has no discernable pattern. -A poincar\'{e} map takes a periodic input and samples the output of a variable response in phase space. If the system is periodic with that sampling period, the poincar\'{e} map will plot only a single dot, which is the same response seen after each period, e.g. figure \ref{fig:periodic_poincare}. If the response is random, the poincar\'{e} map will have a random distribution, similar to that seen in the phase map (figure \ref{fig:random_poincare}. If the response is chaotic, we expect to see a distribution of points that is not entirely random but is not confined to a single point. This further demonstrates the continuum behaviour where a chaotic variable extends the behaviour of a periodic variable but not to the point of randomness. - -The driven pendulum is a physical system that is known to exhibit chaotic behaviour. The model for this system can be expressed analytically given a small-angle approximation - - - -The phase map and poincar\'{e} map are generated from the model of a driven pendulum \begin{figure} \includegraphics[width=6.5in]{chaotic_b_time.png}