Comparative study of full state variables and time-delay coordinates OGY chaos control for bi-stable vortex induced vibration energy harvesters

A bi-stable spring component is proven to be able to improve the utilizable power from a vortex induced vibration (VIV) energy harvesting system at low speed water flows. However, it is also shown that chaotic vibrations might occur and drastically reduce the utilizable power when water flow velocity varies. Hence, an appropriate controller is required to maintain high-energy orbit vibrations when the system experiences chaos. The OGY chaos control method seems to be potential in this case since it only requires a small perturbation in a structural parameter. However, the requirement of a priori knowledge of all state variables makes the control design tedious and cost-expensive. To overcome this shortcoming, the time-delay coordinates have been proposed. As a tradeoff, the design and implementation might become more complicated. This paper carries out a comparative study between the two methods of using the full state variables and the time-delay coordinates to stabilize the chaotic responses of a bi-stable VIV energy harvesting system by means of the OGY method.