Based on the theory that any chaotic attractor contains an infinite number of unstable periodic orbits. Chaotic dynamics then consists of a motion where the system state moves into one of these orbits, but because of their instability swiftly shifts to another one, and so forth. Control of chaos then is based on applying certain small perturbations to the system, making sure that it stays within one particular orbit and doesn't shift to another one.
The two most popular approaches are OGY (Ott, Grebogi and Yorke) method, and Pyragas continuous control.