Modeling and Robust Trajectory Tracking Control for a Novel Six-Rotor Unmanned Aerial Vehicle

Chengshun Yang,Qiang Zhang,Xiaoning Huang,Zhong Yang,Shaobin Li

doi:10.1155/2013/673525

Abstract

Modeling and trajectory tracking control of a novel six-rotor unmanned aerial vehicle (UAV) is concerned to solve problems such as smaller payload capacity and lack of both hardware redundancy and anticrosswind capability for quad-rotor. The mathematical modeling for the six-rotor UAV is developed on the basis of the Newton-Euler formalism, and a second-order sliding-mode disturbance observer (SOSMDO) is proposed to reconstruct the disturbances of the rotational dynamics. In consideration of the under-actuated and strong coupling properties of the six-rotor UAV, a nested double loops trajectory tracking control strategy is adopted. In the outer loop, a position error PID controller is designed, of which the task is to compare the desired trajectory with real position of the six-rotor UAV and export the desired attitude angles to the inner loop. In the inner loop, a rapid-convergent nonlinear differentiator (RCND) is proposed to calculate the derivatives of the virtual control signal, instead of using the analytical differentiation, to avoid “differential expansion” in the procedure of the attitude controller design. Finally, the validity and effectiveness of the proposed technique are demonstrated by the simulation results.

Highlights

In the past years, unmanned aerial vehicles (UAVs) are broadly concerned and applied
A kind of rotary wing type UAVs is focused to offer the possibility of vertical take-off and landing (VOTL), omnidirectional flying, and hovering performance
We introduce, in this paper, one configuration of a six-rotor UAV composed of six rotors to solve these problems of quad-rotor

Summary

Introduction

In the past years, unmanned aerial vehicles (UAVs) are broadly concerned and applied. Quad-rotor has some potential defects such as smaller payload capacity, lack of hardware redundancy, and anticrosswind capability For this reason, we introduce, in this paper, one configuration of a six-rotor UAV (the structure as shown in Figure 1) composed of six rotors to solve these problems of quad-rotor. The analytic derivative expressions of virtual control variables are usually overly complicated or unknown especially for the uncertain systems, which limits the backstepping technique in practical applications To overcome this drawback, a rapidconvergent nonlinear differentiator (RCND) is proposed to extract the ideal angular rate differential command signals and without calculating the virtual control signal derivative z o y x zg xg og yg Figure 1: The structure of six-rotor UAV and the associated frames. The robust terms of the attitude controller can reduce the effect of disturbance reconstruction errors on the tracking capability of the six-rotor UAV.

Mathematical Modeling

SOSMDO Design

Robust Trajectory Tracking Control Strategy

Rotational Control

Simulation Results and Discussion

Conclusions