Design and Testing of a Shrouded Rotor Micro Air Vehicle with Anti-torque Vanes

The design and testing of a shrouded rotor micro-aerial vehicle that demonstrates an improved hover efficiency and payload capability is described. The vehicle consists of a single fixed pitch rotor with axisymmetric vanes placed in the rotor downwash to adequately counter the rotor torque. A carbon fiber shroud enclosing the rotor is integrated into the vehicle in conjunction with the vanes. The vehicle weighs 257 gm. The main rotor has a diameter of 24 cm with a two bladed coupled hingeless rotor-Hiller stabilizer bar that reduces rotor plane movements and exhibits enhanced maneuverability. Attitude control was achieved by a swashplate connected to the stabilizer bar. Hover stand studies were conducted to determine an efficient blade planform and to compare the performance of an isolated and a shrouded rotor. The anti-torque effectiveness of the vanes was measured. The hingeless rotor introduced significant cross coupling between pitch and roll which was eliminated by optimally phasing the stabilizer bar with respect to the blade pitching axis. At an operating RPM of 3000, the optimum phasing was determined to be 40 degrees. Hiller bar profile losses were minimized by suitably adjusting the paddle collective. Bench top and suspension tests were conducted to measure the vehicle yaw response in and out of ground effect. The vehicle is currently undergoing pitch/roll response testing.