Anisotropic vs. isotropic friction: New theoretical results verified experimentally exhibited by a horizontal pendulum on the rotating disk

The paper presents the investigation of the dynamics of a horizontal pendulum on the rotating disk under isotropic and anisotropic friction. The studied system can serve as an archetypal system for the investigation of numerous practical problems, like disk brake design or clutch dynamics. A dimensionless mathematical model of the system is derived. Two potentially counterintuitive behaviors of the system are demonstrated and explained. For an isotropic system, it is shown that above certain critical disk rotational speed , systems transient response became oscillatory. An estimate for the non-oscillatory transient response time-constant is given. For the anisotropic friction case , the basic mechanism behind the periodic orbit is explained utilizing the reduced-order parametric model (ROPM) of the counterpart linearized system . It is shown, that for certain conditions, the analyzed system is analogical to a mass-variable damper oscillator with its end kinematically excited by a periodic velocity profile . The direction field of the nonlinear system is estimated with numerical computation . Both analytical and numerical findings are tested by experimental results carried out on a specially constructed dedicated laboratory stand. • Nonlinear dynamics of the horizontal pendulum on the rotating disk is investigated. • Oscillatory transient response is observed for the system with isotropic friction. • The periodic orbit mechanism for anisotropic friction conditions is explained. • A reduced-order model analogical to a mass-variable damper system is derived. • Analytical and numerical results are validated by laboratory experiments.