$J_{ri}$	Rotor inertia of $i^{th}$ quad-rotor [kg·m${}^2$]
g	Acceleration due to gravity [m/s${}^2$]
$D_{Xi}$	Uncertainty in $\ddot{X}$ dynamics of $i^{th}$ quad-rotor [m/s${}^2$]
$D_{Yi}$	Uncertainty in $\ddot{Y}$ dynamics of $i^{th}$ quad-rotor [m/s${}^2$]
${\Omega }_{ri}$	Overall speed of the propellers of $i^{th}$ quad-rotor [rad/s]
$I_{xi,}{I}_{yi,}{I}_{zi}$	Moments of $i^{th}$ quad-rotor inertia in X, Y and Z coordinates [kg·m${}^2$]
$m_{Qi}$	Mass of $i^{th}$ quad-rotor [kg]
$M_{\varphi }$ ${}_i$	Roll moment of $i^{th}$ quad-rotor [Nm]
$M_{\theta }$ ${}_i$	Pitch moment of $i^{th}$ quad-rotor [Nm ]
$M_{\psi }$ ${}_i$	Yaw moment of $i^{th}$ quad-rotor [Nm ]
${\theta }_i$	Pitch angle of $i^{th}$ quad-rotor [rad]
${\varphi }_i$	Roll angle of $i^{th}$ quad-rotor [rad]
${\psi }_i$	Yaw angle of $i^{th}$ quad-rotor [rad]
$X_i,Y_i,Z_i$	Position of $i^{th}$ quad-rotor in earth coordinates [m]
${\dot{X}}_i,{\dot{Y}}_i,{\dot{Z}}_i$	Velocity of $i^{th}$ quad-rotor in earth coordinates [m/s]
${\ddot{X}}_i,{\ddot{Y}}_i,{\ddot{Z}}_i$	Accelerations of $i^{th}$ quad-rotor in earth coordinates [m/s${}^2$]