The last two decades has seen the emergence of new phenomena being observed in all areas of nonlinear dynamics. Principal among these has been chaotic vibrations; random-like motions produced from completely deterministic systems. It has been known that this phenomena exists in low order systems such as simple one degree-of-freedom mechanical problems, however very little research has been directed towards more complex mechanical systems such as rotating multi-body systems.

This seminar will outline the speaker's PhD research project concerning an investigation to identify possible chaotic instabilities occurring in nonlinear mechanical systems involved with the dynamics of rotating multi-body systems. In particular, results for a three dimensional rigid body with internal moving parts and energy dissipation will be primarily presented. This is analogous to a nutation damper system used for stability in dual-spin spacecraft. Numerical and analytical results will be presented, identifying chaotic phenomena in this model when the rotor is subjected to a sinusoidally varying torque for a range of forcing amplitude and frequency. Such a torque, in practice, may arise under malfunction of the control system or from an unbalanced rotor. The motion is studied using the current techniques of time history, phase space, frequency spectrum, Poincare map analysis and Lyapunov characteristic exponents analysis.

Three recently developed methods of feedback control will then be introduced to eliminate the chaotic instabilities in the Dual-Spin spacecraft system and numerical simulations will show the effectiveness of each method. Similar results for a rotating body with energy dissipation and a torsional driveline incorporating a Hooke's Joint will also be briefly outlined.