Design and testing of a 1/12th-scale solid state adaptive rotor

A new approach to helicopter flight control through active blade pitch manipulation is presented. By using piezoceramic directionally attached piezoelectric (DAP) torque plates mounted between the rotor shaft and the blade root, the pitch angle of the helicopter rotor blades may be adjusted as the blades sweep the azimuth. Analytical models based on classical laminated plate theory for steady torque-plate deflection are presented. To verify the models, a 1/12th-scale two-bladed experimental test article was constructed. The test article was Froude scaled with a 122 cm total diameter and a 5.5 cm chord. Static and dynamic testing showed that blade pitch deflections could be controlled from -4 through with good correlation between theory and experiment. Dynamic testing demonstrated that the first natural frequency in pitch was greater than 2.5 with a maximum power consumption of 194 mW under the most extreme conditions, thus making it feasible for control of collective, longitudinal and lateral cyclic. Whirl-stand testing at up to 600 RPM showed that the rotor could generate thrust coefficients ranging from -0.0046 through +0.014 with little sensitivity of blade deflection to increases in rotor speed.