Abstract:
This paper describes the development and flight testing of a compact, re-configurable, rotary-wing micro air (MAV) vehicle capable of sustained hover and could potentially be launched from a 40mm grenade launcher. Launching the vehicle as a projectile over the target area could significantly improve the mission range for these energy-constrained platforms. The MAV design features coaxial rotors with foldable blades, and a thrust-vectoring mechanism for pitch and roll control. Yaw control was accomplished by using a specialized counter-rotating motor system comprised of two independently controlled motors. Passive unfolding of the coaxial rotor blades in flight utilizing centrifugal force was demonstrated. A cascaded feedback control strategy was implemented on a 1.7 gram custom-designed autopilot. Systematic wind tunnel tests were conducted with the vehicle on a single degree of freedom stand, which proved the ability of the controller to reject wind gusts up to 6 m/s and stabilize the vehicle during the powered axial descent phase. Different phases of the gun-launched flight sequence were independently verified through targeted flight tests. Free f light testing conducted both indoors and outdoors verified that the vehicle could hover and fly forward in moderate winds. In-flight drop tests were conducted by throttling down the vehicle from a high altitude to attain high axial decent speeds followed by recovery using the rotor thrust to aggressively brake the descent and achieve a stable hover. Finally, the vehicle was launched vertically from a pneumatic cannon followed by a stable projectile phase utilizing the f ins, passive rotor unfolding, and final transition to a stable hover from arbitrarily large attitude angles demonstrating the robustness of the controller, as well as all the sub-systems of the vehicle operating in perfect harmony.