Aerodynamic modeling and design optimization of a variable-pitch variable-camber piezocomposite rotor

Multi-rotor vehicles either use complex mechanisms to control blade pitch angle or use the rotor speed to control the thrust and torque to attain stability, and control. An alternate approach to attain thrust and torque control is by morphing the blades without the use of complex mechanisms, and without varying the rotor speed. This method may require fewer mechanical components, could lead to higher efficiency, and achieve rapid change in thrust. In this context, a variable—camber, variable-pitch hybrid piezocomposite rotor prototype is modeled, optimized, and experimentally tested on a single degree of freedom test setup. The mechanism-free compliant blades are actuated with the Macro-Fiber Composite actuators. First, the baseline aerodynamic model to predict thrust and torque coefficients is presented. The experiments are used to identify the so-called unknown coefficients of an empirical model, and to identify a physics-based correction formula to account for flow induced deformations on the compliant blades. The refined aerodynamic model is used to conduct parametric analyses to predict the thrust and torque coefficients as a function of pitch and the excitation by the piezocomposite actuators. The model is then used for design optimization leading to several optimal designs based on a limited parameter space. Three objective functions are evaluated: Maximizing thrust, minimizing torque, and maximizing thrust-to-torque ratio. The aerodynamic characteristics of these designs are also presented.