Induced-shear piezoelectric actuators for rotor blade trailing edge flaps

Abstract

Much of the current rotorcraft research is focused on improving performance by reducing unwanted helicopter noise and vibration. One of the most promising active rotorcraft vibration control systems is an active trailing edge flap. In this paper, an induced-shear piezoelectric tube actuator is used in conjunction with a simple lever–cusp hinge amplification device to generate a useful combination of trailing edge flap deflections and hinge moments. A finite-element model of the actuator tube and trailing edge flap (including aerodynamic and inertial loading) was used to guide the design of the actuator–flap system. A full-scale induced shear tube actuator flap system was fabricated and bench top testing was conducted to validate the analysis. Hinge moments corresponding to various rotor speeds were applied to the actuator using mechanical springs. The testing demonstrated that for an applied electric field of 3 kV cm−1, the tube actuator deflected a representative full-scale 12 inch flap ±2.8° at 0 rpm and ±1.4° for a hinge moment simulating a 400 rpm condition. The per cent error between the predicted and experimental full-scale flap deflections ranged from 4% (low rpm) to 12.5% (large rpm). Increasing the electric field to 4 kV cm−1 results in ±2.5° flap deflection at a rotation speed of 400 rpm, according to the design analysis. A trade study was conducted to compare the performance of the piezoelectric tube actuator to the state of the art in trailing edge flap actuators and indicated that the induced-shear tube actuator shows promise as a trailing edge flap actuator.