PECULIARITIES OF CATASTROPHIC LANDING OF QUADROCOPTER

Abstract

Most articles on quadrocopter unmanned flight implicitly assume that all four pairs of electric
motor-screw and control scheme are intact. In practice, there are often some or other problems in
the sequence: control circuit – motor-screw. This work is devoted to the consideration of the
features of the landing of a pilotless quadrocopter in the event of failure of one of four pairs of
electric motor-screw. The main features of the emergency landing of the quadrocopter are
determined by mathematical modelling. In good condition, the nasal and tail motors create the
moment of forces that the quadrocopter rotates relative to the vertical axis clockwise. Therefore,
after the emergency cut-off of the nasal electric motor, the yaw angle begins to decrease. At the
same time the tail engine will create a moment at which the pitch angle begins to decrease
(quadrocopter "lowers" the nose). The Jaw and Pitch create a gyroscopic moment of forces, which
begins to rotate the quadrocopter relative to the longitudinal axis, that is, there is a Roll. Having
made a little more than one turn relative to the transverse axis, the quadrocopter begins to rotate
in the opposite direction and in the future the Pitch changes in the vicinity -150º. The
quadrocopter makes almost five turns in the negative direction around the longitudinal axis and
falls to the ground by the right engine. After the emergency shutdown of the tail motor, the pitch
angle begins to increase (the quadrocopter "lowers" the tail). By making more than one turn in a
positive direction relative to the transverse axis, the quadrocopter starts to rotate in the opposite
direction, and in the future the Pitch fluctuates in the vicinity of + 150º. The quadrocopter makes
almost five turns in a positive direction around the longitudinal axis and falls to ground by the left
engine. In good condition, the right and left motors create the moment of forces that the
quadrocopter rotates relative to the vertical axis counterclockwise. Beside this, after the
emergency cut-off of the right electric motor, the roll angle begins to increase (quadrocopter
"lowers" the right side). The Yaw and Roll create a gyroscopic moment of forces, which begins to
rotate the quadrocopter relative to the transverse axis. Having made a little more than one turning
relative to the longitudinal axis, the quadrocopter begins to rotate in the opposite direction and in
the future the Roll fluctuates in the vicinity +150º. The quadrocopter makes almost five turns in
the positive direction around the transverse axis and falls to the ground by the nasal engine. After
the emergency cut-off of the left electric motor, the roll angle begins to decrease (quadrocopter
"lowers" the left side). By making more than one turn in a negative direction relative to the
longitudinal axis, the quadrocopter starts to rotate in the opposite direction, and in the future the
Roll fluctuates in the vicinity of -150º. The quadrocopter makes almost five turns in the negative
direction around the transverse axis and falls to the ground by the tail engine. The horizontal
speed at the moment landing, as well as the angles is unpredictable.
The methods of safe landing of a quadrocopter in the event of failure of one of the four pairs
of motor-screw are proposed. The basis of the proposed methods is to use a parachuting effect.
The parachuting achieved by forced off the power of the motor, which is located at the opposite
end of the same yoke as faulty motor. As a result, the quadrocopter vertical speed at the moment
landing is reduced significantly and is approaching a relatively safe value. The horizontal
components of the speed all the time will be zero, that is, the quadrocopter will fall vertically
down. The angles of the roll and pitch during the fall are zero, that is, the quadrocopter always
land on the chassis.

Key words: quadrocopter, altimeter, 3-axis gyroscope, 3-axis accelerometer, 3-axis
magnetometer, control.