Control of a cylindrical PVTOL vehicle: Global non-linear velocity tracking control considering aerodynamics

In the following paper, a non-linear control law is designed for a three degree-of-freedom "hovering rocket". The proposed control problem is similar to the classic planar vertical take-off and landing (PVTOL) control problem introduced by Hauser et al. (1992). However, the dynamic model of the "hovering rocket" used for controller design includes a description of vehicle aerodynamics such that the designed controller will enable tracking at velocities where aerodynamics effects are significant. The controller design is based on an innovative extension to the published idea of using feedback to cast the system's closed-loop dynamics into a stable cascade structure; see Sepulchre et al. (1997) and Olfati-Saber (2002). Approximations to the system's aerodynamics are made to enable control design. An innovative control law is proposed that minimizes the norm of the interconnection term between closed-loop subsystems and enables trade-off between horizontal and vertical tracking performance. Global stability of this control law is proven. Simulation results demonstrate aggressive tracking performance, superiority of the improved cascade control design, and robustness of the controller to approximations necessary for controller design.