Comparison of various quaternion-based control methods applied to quadrotor with disturbance observer and position estimator

• Several attitude controllers using quaternion were designed to control quadrotor.
• Several position controllers were designed to control quadrotor.
• The disturbance observer and the state-space estimator were designed.
• The comparison of performance of combinations of controllers was carried out.
• The external disturbance was applied in the verification process.

The aim of this article is to design and verify various control techniques for a quadrotor using a quaternion representation of the attitude. All attitude controllers use a quaternion error to compute control signals that are calculated from an actual quaternion and a desired quaternion obtained from a position controller. Attitude and position control laws are computed using a PD, LQR and backstepping control technique.All combinations of controllers will be verified by simulation. We add noise, apply an actuator restriction and use a different sampling period for position and attitude feedback signals to get the simulation closer to real conditions.Moreover, external disturbances were implemented into the simulation; hence a disturbance observer along with a position estimator will be designed to improve the performance of the presented controllers.The performance of all combinations of controllers was evaluated using various quality indicators, such as the integral of absolute errors and total thrust, settling times and also maximum overshoots when external disturbance was applied. Some of the controllers exhibit very similar behaviour, so we chose the three best controllers for each scenario used in the simulation.