Observer-based second order sliding mode control for tethered quadrotor transportation

Quadrotor has been widely applied on tethered transportation due to its advantages of safety, low cost, easy operation and high mobility. However, a precise trajectory tracking control is hard to achieve due to the long tether and tethered payload, specially during the maneuvering motion, which is a classical underactuated system. Based on the above questions, a new double-loops observer-based second order sliding mode control(OBSOSMC) scheme is proposed for tethered quadrotor transportation. The dynamics equation of the quadrotor was established based on Newton's Second Law and Euler-Lagrange mechanic. The payload is regarded as disturbance, and observers are designed in both position loop and attitude loop under which the disturbance can be precisely and directly compensated in the designed second order sliding mode control(SOSMC). The asymptotic stability of the closed loop system based on proposed OBSOSMC is theoretically proved by the Lyapunov stability method. The effectiveness of the proposed OBSOSMC scheme is proved by comparing Classical PID and SOSMC in two different practical experiments.