Figures
Explore figures and images from publications
Fig 3 - uploaded by Yao Su
Content may be subject to copyright.
Computing logic of three allocation frameworks. FD-based framework (dashed blue arrows) converts the nonlinear allocation problem to a linear mapping, and acquires a least-square solution by setting Z Z Z = 0 in the general solution. QP-based framework (dotted orange arrows) transforms the allocation problem to a constrained QP with Taylor expansion, but it only generates an approximate solution. The nullspace-based framework (solid green arrows) formulates the constrained QP problem with extra constraints, and projects the approximate solution onto the nullspace of the allocation matrix to obtain an exact solution.

Computing logic of three allocation frameworks. FD-based framework (dashed blue arrows) converts the nonlinear allocation problem to a linear mapping, and acquires a least-square solution by setting Z Z Z = 0 in the general solution. QP-based framework (dotted orange arrows) transforms the allocation problem to a constrained QP with Taylor expansion, but it only generates an approximate solution. The nullspace-based framework (solid green arrows) formulates the constrained QP problem with extra constraints, and projects the approximate solution onto the nullspace of the allocation matrix to obtain an exact solution.

Source publication
Article
Full-text available
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...

Context in source publication

Context 1
... section starts with outlining two commonly used allocation methods based on FD and QP respectively. Their advantages and disadvantages are discussed. This motivates us to propose a novel nullspace-based allocation framework that combines the merits of the two existing methods. The computing logic of these three allocation frameworks are shown in Fig. ...

Similar publications

Article
Full-text available
This paper presents a multi-unmanned aerial vehicle (UAV)-assisted mobile edge computing system, where multiple UAVs are used to serve mobile users. We aim to minimize the overall energy consumption of the system by planning the trajectories of UAVs. To plan the trajectories of UAVs, we need to consider the deployment of hovering points (HPs) of UA...
Preprint
Full-text available
Providing both the vertical take-off and landing capabilities and the ability to fly long distances to aircraft opens the door to a wide range of new real-world aircraft applications while improving many existing applications. Tiltrotor vertical take-off and landing (VTOL) unmanned aerial vehicles (UAVs) are a better choice than fixed-wing and mult...
Preprint
Full-text available
Tracking position and orientation independently affords more agile maneuver for over-actuated multirotor Unmanned Aerial Vehicles (UAVs) while introducing undesired downwash effects; downwash flows generated by thrust generators may counteract others due to close proximity, which significantly threatens the stability of the platform. The complexity...
Chapter
Full-text available
According to the reliability requirement of the Flight Control Computer for Unmanned Aerial Vehicle (UAV), a design scheme is proposed to ensure its reliability by using tri-redundancy technology. Further, by selecting appropriate redundant mode and the architecture model of the triple redundant flight control computer is established in this paper....
Article
Full-text available
The safety of unmanned aerial vehicle (UAV) flights depends on many factors, such as the absence of failures or malfunctions of aviation equipment, the absence of exposure to adverse environmental phenomena, and the absence of errors by the aircraft crew and engineering personnel. In uncontrolled airspace by the internal affairs authorities, when t...

Citations

... 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 [30,31,32]. 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. ...
... Using eight DoF input to represent the six DoF virtual inputs and has multiple solutions, including the leastsquare allocation (24) widely used in previous works [21,30,31]. Actually, it can be observed from (20) that adding any components from the nullspace of ...
Full-text available
Preprint
This paper presents the control and experiment of a novel multirotor aerial platform, which is capable of full actuation for six Degree of Freedom (DoF) motions. The platform is actuated by a number of tilting-thrust modules, each consisting of a regular quadcopter and a mechanically passive hinge. The platform in this paper has four such actuator modules, making an over-actuated system that requires input allocations in the feedback control. In addition to the common least-square method that minimizes the sum of squares of the thrusts, we propose a control allocation that minimizes the maximum thrust in a closed-form analytical solution for efficient real time computation. This allocation can achieve larger inclination angles than that by the least-square method, when thrust forces are insufficient to overcome the gravity for all poses. Simulation and real world experiments are presented to demonstrate the control of the aerial platform for six DoF motion tracking and disturbance rejection.
... 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. ...
... Given the system's attitude dynamics (19), the attitude control input τ c (22) is computed using adaptive control principles, in order to guarantee the stability of the vehicle's attitude. ...
Preprint
The control problem of a multi-copter swarm, mechanically coupled through a modular lattice structure of connecting rods, is considered in this article. The system's structural elasticity is considered in deriving the system's dynamics. The devised controller is robust against the induced flexibilities, while an inherent adaptation scheme allows for the control of asymmetrical configurations and the transportation of unknown payloads. Certain optimization metrics are introduced for solving the individual agent thrust allocation problem while achieving maximum system flight time, resulting in a platform-independent control implementation. Experimental studies are offered to illustrate the efficiency of the suggested controller under typical flight conditions, increased rod elasticities and payload transportation.
... Lyapunov guidance vector fields are developed for autonomous coordination of multiple unmanned aircraft [105], which yields feasible and globally stable paths with guaranteed target stand-off distance bounds. The loitering tracking strategy is further improved and extended in [106] and [107] by speeding the convergence process and imposing a curvature limitation, respectively. ...
Article
With the rapid development of computer technology, automatic control technology and communication technology, research on unmanned aerial vehicles (UAVs) has attracted extensive attention from all over the world during the last decades. Particularly due to the demand of various civil applications, the conceptual design of UAV and autonomous flight control technology have been promoted and developed mutually. This paper is devoted to providing a brief review of the UAV control issues, including motion equations, various classical and advanced control approaches. The basic ideas, applicable conditions, advantages and disadvantages of these control approaches are illustrated and discussed. Some challenging topics and future research directions are raised.
... 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. ...
Full-text available
Article
Overactuated multirotor unmanned aerial vehicles (UAVs) usually consist of multiple tiltable thrust actuators. The controllers are mostly designed by regarding the thrust forces and actuator tilting angles as inputs of outer-loop position and attitude controllers, while formulating an inner-loop controller for each actuator to track the thrust and angle as required by the outer-loop. This hierarchical control strategy separates the complicated combined dynamics into two relatively simple systems, and thus simplifies the control design. However, the interaction between the two systems is neglected and therefore the control performance will be degraded when the inner-loop dynamics are not sufficiently fast. This letter investigates the capability of a new overactuated multi-rotor UAV configuration, where regular quadcopters are passively hinged onto the frame as tiltable thrust actuators. Apart from the thrust force and tilting angle, each actuator has additional auxiliary torque inputs, which exhibit fast responses as they are not subject to the inner-loop actuator tilting angle dynamics. In this letter, an add-on attitude compensation control is designed exploiting the auxiliary inputs to reduce the tracking and disturbance-rejection errors from the nominal control loop. The effectiveness is demonstrated in simulation and verified by experiment.
... In the outer-loop, desired inputs of the main body from position and attitude controller are represented by virtual force and torque commands (e.g. 6 Degree-of-freedom (DoF) wrench) based on feedback linearization of the nonlinear rigid body dynamics. Then the desired force and angle of every actuator are calculated by an allocation mapper that accounts for redundant actuations to meet the desired wrench [3,[12][13][14][15]. The desired force and angle for every actuator are tracked in the inner loop by the low-level actuator control loops. ...
... 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][14][15]25], as long as the goal is to solve for the control inputs from Eq. (30), the control performance will be difficult to improve. Based on these reasons, we decided to use the auxiliary inputs to formulate a compensation loop. ...
Full-text available
Preprint
Overactuated multirotor unmanned aerial vehicles (UAVs) usually consist of multiple tiltable thrust actuators. The controllers are mostly designed by regarding the thrust forces and actuator tilting angles as inputs of outer-loop position and attitude controllers, while formulating an inner-loop controller for each actuator to track the thrust and angle as required by the outer-loop. This hierarchical control strategy separates the complicated combined dynamics into two relatively simple systems, and thus simplifies the control design. However, the interaction between the two systems is neglected and therefore the control performance will be degraded when the inner-loop dynamics are not sufficiently fast. This paper investigates the capability of a new overactuated multirotor UAV configuration, where regular quadcopters are passively hinged onto the frame as tiltable thrust actuators. Apart from the thrust force and tilting angle, each actuator has additional auxiliary torque inputs, which exhibit fast responses as they are not subject to the inner-loop actuator tilting angle dynamics. In this paper, an add-on attitude compensation control is designed exploiting the auxiliary inputs to reduce the tracking and disturbance-rejection errors from the nominal control loop. The effectiveness is demonstrated in simulation and verified by experiment.