Helicopter flight control using inverse optimal control and backstepping

This paper presents a hierarchical inner-outer loop-based scheme for flight control of a small unmanned helicopter in the presence of input time-delay. The controller is designed based on a two-time-scale separation architecture which includes a fast inner loop and a slow outer loop. The inner-loop (attitude controller) employs an inverse optimal control strategy, which circumvents the tedious task of numerically solving an online Hamilton-Jacobi-Bellman (HJB) equation to obtain the optimal controller. The designed controller is optimal with respect to a meaningful objective function which considers penalties for control input, angular position and angular velocity errors. The outer loop (position) controller uses the backstepping technique to control the position and keep the helicopter on track. Finally, computer simulations are conducted to validate the theoretical results and illustrate the tracking performance of the proposed control method.