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Simulation: Vertical rotation trajectory tracking performance comparison between three allocation methods on the overactuated UAV platform. (F for FD-based framework, Q for QP-based framework, N for nullspace-based framework)

Simulation: Vertical rotation trajectory tracking performance comparison between three allocation methods on the overactuated UAV platform. (F for FD-based framework, Q for QP-based framework, N for nullspace-based framework)

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Article
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Multirotor copters with full six Degree of Free-dom(DoF) maneuvering are often overactuated. The control allocation of overactuated UAV platforms can have an infinite number of solutions due to their redundancy. The most common allocation framework is based on Force Decomposition(FD), which provides a robust least-square solution and is easy to imp...

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... to Section V-A, three allocation frameworks are implemented on the overactuated UAV platform in experiment to track the vertical rotation trajectory as shown in Fig. 8. Starting at 10 s, the FD-based allocation framework results in instability. As the joint angles β 1 and β 3 approach ± π 2 (i.e., the second joint of the top and bottom gimbals), these two gimbals become singular and ill-conditioned. For the QPbased framework, the singularity problem is solved by adding constraints on the rate of ...

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Citations

... On the other hand, the authors in [5] show that for the fixed propeller overactuated heptarotor they designed, the minimum energy solution is guaranteed to break at least one of the actuation constraints. To avoid actuation constraints, the authors in [6] suggest a null space-based approach to find feasible control inputs to achieve a desired force and moment. Their approach optimizes the incremental control input added to the currently applied controls. ...
... The optimization is relaxed by adding an error term, assumed to be in the null space of the allocation matrix. Similar to [6], the authors in [7] suggest to allocate incremental control inputs added to the currently applied controls; however, their proposed overactuated platform had only thrust constraints, and thus it was possible to operate away from actuation limits. ...
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p>This paper presents a novel optimization-based full-pose trajectory tracking method to control overactuated multi-rotor aerial vehicles with limited actuation abilities. The proposed method allocates feasible control inputs to track a reference trajectory, while ensuring the tracking of the reference position, and while tracking the closest feasible attitude. The optimization simultaneously searches for a feasible trajectory and corresponding feasible control inputs from the infinite possible solutions, while ensuring smooth control inputs. The proposed real-time algorithm is tested in extensive simulation on multiple platforms with fixed and actuated propellers. The simulation experiments show the ability of the proposed approach to exploit the complex set of feasible forces and moments of overactuated platforms while allocating smooth feasible control inputs.</p
... However, the limited range of the tensioned cables or spherical joints used to connect quadcopters and the tool frame significantly constrains the achievable attitudes. Our group has proposed modular vectored thrust units made of quadcopters and passive mechanisms without angle range limits or constraints for two realizations, one DoF hinge [28,29] or two DoF gimbal [30,31]. These modular vectored thrust units overcome the constraints of the limited orientations between the quadcopters and the main frame in [25][26][27], and enable creating new multirotor aerial platforms for unique capabilities and performance. ...
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... Overactuated aerial vehicles were considered in [19] and the thrust allocation problem was examined using a quad-copter on a dual-axes gimbal configuration followed by singularity avoidance methods. ...
... The controller (22) stabilizes the system dynamics(19) for small deflections. ...
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... As introduced in Section I, the unmodeled dynamics are not considered in the nominal controller framework and they can only be compensated by the integral operation of the tracking controller. Therefore, even if additional inputs are included or the allocation is changed to another allocation method [13]- [15], [25], as long as the goal is to solve for the control inputs from (30), the control performance will be difficult to improve. ...
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