Hovering control of a quadcopter using linear and nonlinear techniques

Abstract

This paper presents a comparative study on linear and nonlinear control techniques for the near-hover attitude stabilisation of a quadcopter. A dynamic model of the quadcopter is developed using Newton-Euler equations, which is inherently nonlinear. Firstly, the classical PID controller is implemented directly on the nonlinear system by decoupling the attitude dynamics and using separate controllers for each attitude variable. Linear controllers can also be implemented on this system by linearising it about an operating point, which is shown for the linear quadratic regulator (LQR). Such a linear approximation may not always retain the actual system dynamics and are not very efficient in the real world scenario. Model based nonlinear controllers prove to be superior in such instances, and one such popular technique - Feedback Linearisation using dynamic inversion is discussed in this paper. The proposed control algorithms are tested on the quadcopter model using numerical simulations in MATLAB/Simulink and analysed in terms of fall time, percentage undershoot and computation time. Copyright 2018 Inderscience Enterprises Ltd.