SDRE attitude control with global asymptotic stability for an Unmanned Helicopter

In accordance with actual different response rate of each component in Unmanned Helicopter (UMH), the overall nonlinear model was divided into inner and outer loops, and then, a “two-timescale” mathematics model was established. The paper improved and expanded state dependent riccati equation (SDRE) control approach, deriving analytical conditions for achieving global asymptotic stability with lyapunov stability theory. Proof was given. By combining improved SDRE control with nonlinear feed-forward compensation technique, the full envelop flight attitude control laws could be designed based on two-timescale affine nonlinear model. Simulation results showed that the control strategy could effectively overcome the problems that SDRE´s applicable scope was narrow and closed-loop system was local asymptotic stable. Therefore, it can be popularized to general nonlinear system´s control.