  Achieving short-distance flight helps improve the efficiency of humanoid
robots moving in complex environments (e.g., crossing large obstacles or
reaching high places) for rapid emergency missions. This study proposes a
design of a flying humanoid robot named Jet-HR2. The robot has 10 joints driven
by brushless motors and harmonic drives for locomotion. To overcome the
challenge of the stable-attitude takeoff in small thrust-to-weight conditions,
the robot was designed based on the concept of thrust vectoring. The propulsion
system consists of four ducted fans, that is, two fixed on the waist of the
robot and the other two mounted on the feet, for thrust vector control. The
thrust vector is controlled by adjusting the attitude of the foot during the
flight. A simplified model and control strategies are proposed to solve the
problem of attitude instability caused by mass errors and joint position errors
during takeoff. The experimental results show that the robot's spin and dive
behaviors during takeoff were effectively suppressed by controlling the thrust
vector of the ducted fan on the foot. The robot successfully achieved takeoff
at a thrust-to-weight ratio of 1.17 (17 kg / 20 kg) and maintained a stable
attitude, reaching a takeoff height of over 1000 mm.
