Nonlinear control design for quadrotors

In this paper, we present a nonlinear controller design for quadrotors using dynamic inversion approach. The approach uses two loop structure to design a controller. In the outer loop, translation dynamics is used to generate the required thrust, pitch angle, and roll angle commands. The inner loop generates body rates to meet the desired attitude commands and these required thrust and body rate commands are converted into the desired angular speed of each individual DC motor. By generating the desired angular speed of individual motor, a quadrotor can be controlled in three dimensional environments. The performance of the proposed design is compared with the linear proportional-integral-derivative (PID) controller to show the effectiveness of the nonlinear design. This paper also addresses the issue of singularity problem associated with the transformation matrix using a pseudo frame algorithm.