Simultaneous energy harvesting and gust alleviation for a multifunctional composite wing spar using reduced energy control via piezoceramics

This article examines the concept and design of a multifunctional composite sandwich structure for simultaneous energy harvesting and vibration control. The intention is to design a composite wing spar for a small unmanned aerial vehicle which is able to harvest energy itself from ambient vibrations during normal flight along with available sunlight. If the wing experiences any strong wind gust, it will sense the increased vibration levels and provide vibration control to maintain its stability. The proposed multifunctional composite wing spar integrates a flexible solar cell array, piezoelectric wafers, a thin film battery, and an electronic module into a composite sandwich structure. The piezoelectric wafers act as sensors, actuators, and harvesters. The basic design factors are discussed for a beam-like multifunctional wing spar with energy harvesting, strain sensing, and self-controlling functions. The configurations, locations, and operating modes of piezoelectric transducers are also discussed for optimal power generation. The equivalent electromechanical representations of a multifunctional wing spar is derived theoretically and simulated numerically. Special attention is given to the self-contained gust alleviation with the goal of using available energy harvested from ambient vibrations. A reduced energy control law is implemented to reduce the actuation energy and the dissipated heat. This law integrates saturation control with a positive strain feedback controller and is represented by a positive feedback operation amplifier and a voltage buffer operation amplifier for each mode. This study builds off of our previous research and holds promise for improving unmanned aerial vehicle performance in wind gusts. Here, we also include, but not use, a flexible solar panel in our modeling.