State-dependent Riccati equation control for small autonomous helicopters

This paper presents a flight control approach based on a state-dependent Riccati equation and its application to autonomous helicopters. For our experiments, we used two different platforms: an XCell-90 small hobby helicopter and a larger vehicle based on the Yamaha R-Max. The control design uses a six-degree-of-freedom nonlinear dynamic model that is manipulated into a pseudolinear form where system matrices are given explicitly as a function of the current state. A standard Riccati equation is then solved numerically at each step of a 50 Hz control loop to design the nonlinear state feedback control law online. In addition, the state-dependent Riccati equation control is augmented with a nonlinear compensator that addresses issues with the mismatch between the original nonlinear dynamics and its pseudolinear transformation.