Rotating orbits of pendulum in stochastic excitation

A method to extract energy from an excitation which is stochastic in nature is presented. The experimental rig comprises a pendulum, and a vertical excitation is provided by a solenoid. The control input assumed in the form of a direct current motor, and another motor, used in reverse, acts as a generator. The stochastic excitation has been achieved by varying the time interval between switching the RLC circuit on and off according to a random distribution. Such non-linear vertical excitations act on an oscillatory system from which a pendulum is pivoted. The Pierson-Moskowitz spectrum has been chosen as the random distribution while an inverse transform technique has been used for generation of the random excitation signal in LabVIEW environment. Moreover, a bang-bang control algorithm has been implemented to facilitate rotational motion of the pendulum. Experimental observations have been made for various noise levels of vertical excitations, and their implication on energy generation has been discussed. A positive amount of energy has been extracted for a minimal amount of the control input.