Special Session 7: Lie Symmetries, Conservation Laws, and Other Approaches in Solving Nonlinear Differential Equations

Distributed Position and Velocity Delay Effects in a Van der Pol System with Time-periodic Feedback
Sudipto Roy Choudhury
University of Central Florida
USA
Co-Author(s):    Ryan Roopnarain
Abstract:
The effects of a distributed delay on a parametrically forced Van der Pol limit cycle oscillator are considered. Delays modeling time lags due to a variety of factors in self-excited systems, have been considered earlier in the context of modification and control of limit cycle and quasiperiodic responses. Those studies are extended here to include the effects of periodically amplitude modulated {\it distributed} delays in both the position and velocity. A normal form or `slow flow` is employed to search for various bifurcations and transitions between regimes of different dynamics, including amplitude death and quasiperiodicity. The existence of quasiperiodic solutions then motivates the derivation of a second slow flow. A detailed comparison of the results and predictions from the second slow flow to numerical solutions is made. The second slow flow is also employed to approximate the amplitudes of the quasiperiodic solutions, yielding close agreement with the numerical results on the original system. Finally, the effect of varying the delay parameter is briefly considered, and the results and conclusions are summarized.