A new global robust optimal sliding mode control approach for trajectory tracking of 2-DOF Quanser Helicopter

In this paper, a new design control strategy for finite-time trajectory tracking of Unmanned Aerial Vehicles (UAVs) is proposed. First, an optimal control based on the LQR technique is designed for the nominal system. To ensure the control robustness, Sliding Mode Control (SMC) is combined with the above LQR control method. Combining these two methods lies in the fact that the robust controllers tackle the uncertainties when the optimal controller performances are unaffected. Second, as the performance of the SMC greatly depends on the choice of the sliding surface, a novel method based on the resolution of a Sylvester equation is proposed. The main contribution of this paper is that the novel proposed control scheme is chattering free. Rigorous stability analysis for the closed-loop system is given and proves that the proposed control scheme generates a sliding mode by successfully reducing the effect of uncertainties and disturbances that cause chattering. The effectiveness of the proposed control scheme is validated through experimental results, which substantiate that the combination of SMC with the LQR method result in not only reduced tracking error but also improved tracking response with minimisation of the chattering phenomenon.