Nonlinear robust control of tail-sitter aircrafts in flight mode transitions

Abstract

In this paper, a nonlinear robust controller is proposed to deal with the flight mode transition control problem of tail-sitter aircrafts. During the mode transitions, the control problem is challenging due to the high nonlinearities and strong couplings. The tail-sitter aircraft model can be considered as a nominal part with uncertainties including nonlinear terms, parametric uncertainties, and external disturbances. The proposed controller consists of a nominal H ∞ controller and a nonlinear disturbance observer. The nominal H ∞ controller based on the nominal model is designed to achieve the desired trajectory tracking performance. The uncertainties are regarded as equivalent disturbances to restrain their influences by the nonlinear disturbance observer. Theoretical analysis and simulation results are given to show advantages of the proposed control method, compared with the standard H ∞ control approach.

Simulation of the Transition Phase for an Optimally-Controlled Tethered VTOL Rigid Aircraft for AirborneWind Energy Generation

“…The AP-2 aircraft was not initially designed for VTOL, but we want to see what happens if we modify it by adding vertical takeoff-landing capabilities. We assume that there are four propellers mounted to make the quadrotor conventional shape, so that the aircraft will behave as a tail-sitter aircraft, i.e., a VTOL aircraft that takes off and lands on its tail, then tilts horizontally for forward flight [25]. Also, we assume that the aircraft rotors or propellers are foldable.…”

“…Normally a transition phase is difficult to be formulated and solved. There are some papers solving the transition phase from hovering to forward flight for several Unmanned Aerial Vehicles (UAVs) using several control techniques [25][26][27][28][29], and the back-way transition from forward flight to hovering for a tail-sitter UAV [29]. Also, for a flapping vehicle [30] there is a paper that simulates the transition phase using optimal control to minimize the time interval for this phase [31].…”

Disturbance Observer-Based Backstepping Control of Tail-Sitter UAVs

“…Flight tests with manual and fully autonomous flight modes show a minimal altitude drop between different flight modes. Li et al [16] presented a robust nonlinear controller for flight mode transition between hovering to level-flight mode where tail-sitter aircraft model with uncertainties including nonlinear terms, external disturbances, and parametric uncertainties. Zhou et al [17] proposed novel trajectory planning algorithms for a UAV under the constraints of system positioning accuracy while correcting the error during the flight process of a UAV.…”

Data-driven model-free sliding mode learning control for a class of discrete-time nonlinear systems

“…Nonlinear systems are extensively used in industry. Almost all actual control plants are nonlinear, such as aircrafts (Li et al, 2018), robots (Baek et al, 2019), industrial processes (Aksu and Coban, 2019), so it is significant to study on the control of the nonlinear systems. In addition, almost all the control algorithms need to be implemented by computers, so it is more meaningful to study the control of discrete-time nonlinear systems.…”