An underactuated mechanical system (UMS) is a system which has fewer independent control actuators than degrees of freedom to be controlled. Control of UMS is considered as one of the most active fields of research because of its diverse engineering applications. This survey reviews UMS from its history to the state-of-the-art research on modelling, classification, control, and to some extent, provides some unique insights for bottleneck issues and future research directions.

/pdf/a-survey-of-underactuated-mechanical-systems-4tw16vhjoz.pdf

A Survey of Underactuated Mechanical Systems

Autonomous vertical landing on an oscillating platform: an internal-model based approach

This brief presents a backstepping-based controller with input saturations, applicable for the hover flight of an unmanned aerial vehicle (UAV). A dynamic model for a generic UAV is introduced that is valid for quasi-stationary conditions, with quaternion formulation of the kinematics equations. Based on this model, a backstepping design formulation is deduced for UAV hover control, and its global asymptotic stability is demonstrated. In order to cope with limitations due to reduced actuation, saturations are introduced in the control design, and the stability of the modified control solution is verified. Simulation results are presented for the hover stabilization of an airship UAV, which are demonstrative of the excellent performance of the proposed controller and illustrate its robustness in face of wind disturbances.

Hover Control of an UAV With Backstepping Design Including Input Saturations

In this paper, a mixed robust feedback linearization with linear GH controller is applied to a non linear quadrotor unmanned aerial vehicle. An actuator saturation and constrain on state space output are introduced to analyse the worst case of control law design. The results show that the overall system becomes robust when weighting functions are chosen judiciously. Performance issues of the controller are illustrated in a simulation study that takes into account parameter uncertainties and external disturbances as well as measurement noise.

http://ieeexplore.ieee.org/iel5/10375/32977/01545112.pdf

Robust feedback linearization and GH/sub /spl infin// controller for a quadrotor unmanned aerial vehicle

This note develops a nonlinear output-feedback controller to force a nonminimum phase, underactuated vertical take-off and landing aircraft to globally asymptotically track a reference trajectory generated by a reference model. The control development is based on a global exponential observer, some global coordinate transformations, Lyapunov's direct method and an extension of the backstepping technique. Interestingly, the proposed methodology also yields new results for the previously studied problems of stabilization and output tracking or regulation. Numerical simulations illustrate the effectiveness of the proposed controller.

On global tracking control of a VTOL aircraft without velocity measurements

We study robust hovering control of vertical/short takeoff and landing (V/STOL) aircraft. For hovering control, we can model a V/STOL aircraft as a planar vertical takeoff and landing (PVTOL) aircraft. We use an optimal control approach to design a robust hovering control. The resulting control is a nonlinear state feedback whose robustness is demonstrated by numerical simulations.

https://www.researchgate.net/profile/Robert_Brandt/publication/3332082_Robust_hovering_control_of_a_PVTOL_aircraft/links/0c960518862e82925f000000.pdf

W. Zhang

Papers

Robust hovering control of a PVTOL aircraft