Abstract
The quadrotor has been the most popular aircraft in the last decade due to its excellent dynamics and continues to attract ever-increasing research interest. Delivering a quadrotor from a large fixed-wing aircraft is a promising application of quadrotors. In such an application, the quadrotor needs to switch from a highly unstable status, featured as large initial states, to a safe and stable flight status. This is the so-called large-scale stability control problem. In such an extreme scenario, the quadrotor is at risk of actuator saturation. This can cause the controller to update incorrectly and lead the quadrotor to spiral and crash. In this article, to safely control the quadrotor in such scenarios, the control input constraint is analyzed. The key states of a quadrotor dynamic model are selected, and a two-dimensional dynamic model is extracted based on a symmetrical body configuration. A generalized point-wise min-norm nonlinear control method is proposed based on the Lyapunov function, and large-scale stability control is hence achieved. An enhanced point-wise, min-norm control is further provided to improve the attitude control performance, with altitude performance degenerating slightly. Simulation results showed that the proposed control methods can stabilize the input-constrained quadrotor and the enhanced method can improve the performance of the quadrotor in critical states.
Highlights
Hailed for its marvelous dynamical capabilities, the quadrotor has proved to be a reliable tool in a wide array of applications such as surveillance, transportation, aerial photography, and disaster response
Problems arise in considering the potential application of delivering a quadrotor from a fixed-wing aircraft, as stabilizing a quadrotor with ‘‘large initial states’’ is a challenging issue
By quickly adjusting the quadrotor’s attitude, the dynamics is representative in a vertical plane; we call it the xoz plane
Summary
Hailed for its marvelous dynamical capabilities, the quadrotor has proved to be a reliable tool in a wide array of applications such as surveillance, transportation, aerial photography, and disaster response. This article aims at designing a stable control algorithm to safely switch the quadrotor from large initial states to a normal operating state. For this stability control problem, the control input constraint is a key factor that affects the stability of the system. It would need to use a simple strategy to stabilize the system, which is acceptable for normal quadrotors on board chips He and Han[16] proposed a control-Lyapunov function for robust control as well as a generalized point-wise minnorm control that can handle inputs and outputs in nonlinear systems with constraints. We discuss potential avenues for future work in section ‘‘Conclusion.’’
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