Continuous ant colony filter applied to online estimation and compensation of ground effect in automatic landing of quadrotor

The automatic landing of a quadrotor is often associated with model uncertainties, measurement noises, and ground effect phenomenon. To mitigate these challenges, the accurate estimation of states especially the height above the ground, and its rate of change is vital. Moreover, the error of ground effect model can also be estimated and compensated during landing. In this paper, the recently developed continuous ant colony filter is implemented for integrated estimation of states and parameters. The estimated states are used in height control loop. To investigate the closed loop performance of the filter, two control strategies, a classical proportional-integral-derivative controller and a sliding mode controller are utilized and their performance are compared in the presence of ground effect compensation and without it. Also, the error of ground effect model is estimated and compensated in landing algorithm. Finally, a landing procedure is proposed including a ground effect estimation phase before the touchdown. The simulation results show that the proposed algorithm effectively improves the landing performance when the ground effect is properly compensated. Moreover, small estimation errors, obtained from the simulations, prove the good performance of the new filter in states and parameters estimation.