Attainable Force Approximation and Full-Pose Tracking Control of an Over-Actuated Thrust-Vectoring Modular Team UAV

Abstract

Traditional vertical take-off and landing (VTOL) aircraft can not achieve optimal efficiency for various payload weights and has limited mobility due to its under-actuation. With the thrust-vectoring mechanism, the proposed modular team UAV is fully actuated at certain attitudes. However, the attainable force space (AFS) differs according to the team configuration, which makes the controller design difficult. We propose an approximation to the AFS and a full-pose tracking controller with an attitude planner and a force projection, which guarantees the control force is feasible. The proposed approach can be applied to UAVs having multiple thrust-vectoring effectors with homogeneous agents. The simulation and experiment demonstrate a tilting motion during hovering for a 4-agent team.

Figures (11)

• Figure 1: The prototype of the proposed A4-Inc team UAV, which is a 4-agent system with one additional navigator module at the center. The agent 1 and agent 2 are placed in inconsistent orientation.
• Figure 2: The design of a single agent. The gimbal design leads to inherent distinct angle limits on $\eta_{i,x}$ and $\eta_{i,y}$, which results in different orientations in a team system and forms complicated attainable force space.
• Figure 3: The control block diagram of the team system.
• Figure 4: The spherical slices simplification of a single agent AFS. With $\sigma_x=\pi/6$, $\sigma_y=\pi/2$, agent $i$'s AFS, $\mathcal{D}_i$, is non-convex as drawn in the left figure, which can be approximated by a spherical slice $\mathcal{D}_i'$.
• Figure 5: Examples of Minkowski sum of AFSs with $n=2$, $\sigma_y = \pi/2$, and $\sigma_x < \pi/2$. For the special case that either $\sigma_x = \pi/2$ or $\sigma_y = \pi/2$, the bottom of the concated AFS is not a point but a line for consistent orientation agents or a plane for inconsistent orientation agents.