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Underactuated Waypoint Tracking of a Fixed-Wing UAV
(Journal article; Peer reviewed; Tidsskriftartikkel, 2013)
In this paper a new method of performing waypoint tracking is shown for underactuated fixed-wing UAVs. The position error can be mapped onto the desired axis using a desired rotation matrix, while the velocity error can be mapped to the desired axis using a desired angular velocity. With all errors defined along one axis, the tracking problem is easily solved using only one thruster. A velocity ...
Underactuated Control of Quadrotors with Collision Avoidance
(Journal article; Peer reviewed; Tidsskriftartikkel, 2013)
In this paper a saturated controller is derived that solves the translational control problem for underactuated quadrotors. The controller is applied to multiple quadrotors during a formation reconfiguration where the quadrotors move from an initial position to a desired position. The null-space-based behavioral control method is a popular method for avoiding collisions between mobile agents, and ...
Real-Time Particle Tracking using a Formation of UAVs
(Journal article; Peer reviewed; Tidsskriftartikkel, 2013)
In this paper the problem of real-time particle tracking is studied. Using sensor measurements, a formation of UAVs autonomously find the closest point with high particle density where they enter a holding pattern. After converging to the holding pattern, one UAV will remain, while the rest will go looking for other maxima. To avoid collisions between the UAVs during the mission, a controller is ...
A Decoupled Approach for Flight Control
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016)
A decoupling method for flight control is presented that greatly simplifies the controller design. By approximating the higher order derivatives of the angle of attack and sideslip, it enables a rotation controller and a speed controller to be derived independently of each other, and thus gives access to a vast number of controller solutions derived for general classes of rotational and translational ...
Subsumption architecture applied to flight control using composite rotations
(Peer reviewed; Tidsskriftartikkel; Journal article, 2016-03-19)
In this paper the subsumption theory is applied to flight control through composite rotations where multiple tasks can be defined as simple rotations. The tasks can then be arranged as a hierarchy, where the primary task is always fully pursued, and conflicting lower level tasks are removed by the primary rotation. The concept is applied to a group of uavs that move through an urban terrain while ...
PD+ based trajectory tracking of the underactuated quadrotor platform using dual quaternions
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-29)
We address the problem of state feedback trajectory tracking of the underactuated quadrotor platform in the dual quaternion framework through a PD+ tracking controller. The control law negates the need of generating a desired attitude trajectory as the translational error is mapped directly onto the rotational actuators through a virtual frame. More precisely, we show uniform practical asymptotic ...
Dual quaternion control: a review of recent results within motion control
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-24)
This paper presents a review of recent results in the field of dual quaternion based motion control. In addition, we derive two control laws for trajectory tracking control of a fully actuated rigid-body based on the resemblance of dual quaternion kinematics and dynamics to the quaternion based rotational kinematics and dynamics. A velocity error sliding surface and an integrator backstepping ...
Control of Spacecraft Formation with Disturbance Rejection and Exponential Gains
(Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
We address the problem of state feedback translational motion control of a spacecraft formation through a modified sliding surface controller using variable gains and I^2 action for disturbance rejection. The exponential varying gains ensure faster convergence of the state trajectories during attitude maneuver while keeping the gains small (and the system less stiff) for station keeping. Integral ...
Modelling and simulation of interaction forces in tugboat-assisted docking of large marine vessels
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-11-22)
In this paper, we address modelling and simulation of dynamics involved in docking of large marine vessels with aid of tugboats, with the aim of providing a tool for improved design of control algorithms for autonomous docking operations. Mathematical models of the docking vessel and tugboats in 3DOF are derived, with a special focus on realistic interactions through towline, contact and friction ...
Take-Home Exams in University Mathematics and Science Subjects: Some Ethical Considerations
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024)
This article addresses some challenging perspectives related to offering take-home exams in mathematics at university level. The challenges arose during work on a previous article where four perspectives originating from Bjerrum Nielsen’s framework (2003) were used to analyze universities’ assessment methods during the Covid lockdown in our country. The perspectives had some ethical considerations ...