Experimental investigation of an autonomous flap for load alleviation

Abstract

This paper presents an experimental aeroservoelastic investigation of a novel load al-leviation concept using trailing edge aps. These aps are autonomous units, which are self-powered and self-actuated, using trailing edge tabs, thereby demonstrating advantages in comparison with conventional ap systems in terms of wiring and structural integration. The aps are free-oating and mass underbalanced, such that they may utter at operation velocities unless suppressed by their own control system. This makes the system very re-sponsive for turbulence and control action. In the wind tunnel campaign presented in this paper, the limit cycle behavior of autonomous, free-oating aps was investigated. It has been shown that limit cycle oscillation can be reached either through structural limiters or by control actions of the trailing edge tabs. In the latter case, the amplitude of the limit cycle oscillation is adjustable to the required energy output. An energy balance of har-vested power and power consumption for actuators and sensing system was made showing that the vibration energy of limit cycle oscillations can be used to keep the amplitude of the limit cycle constant, while the electric batteries that power the load alleviation system are being charged.