60 research outputs found
Differential-Flatness and Control of Quadrotor(s) with a Payload Suspended through Flexible Cable(s)
We present the coordinate-free dynamics of three different quadrotor systems
: (a) single quadrotor with a point-mass payload suspended through a flexible
cable; (b) multiple quadrotors with a shared point-mass payload suspended
through flexible cables; and (c) multiple quadrotors with a shared rigid-body
payload suspended through flexible cables. We model the flexible cable(s) as a
finite series of links with spherical joints with mass concentrated at the end
of each link. The resulting systems are thus high-dimensional with high
degree-of-underactuation. For each of these systems, we show that the dynamics
are differentially-flat, enabling planning of dynamically feasible
trajectories. For the single quadrotor with a point-mass payload suspended
through a flexible cable with five links (16 degrees-of-freedom and 12
degrees-of-underactuation), we use the coordinate-free dynamics to develop a
geometric variation-based linearized equations of motion about a desired
trajectory. We show that a finite-horizon linear quadratic regulator can be
used to track a desired trajectory with a relatively large region of
attraction
Hybrid Modeling of Deformable Linear Objects for Their Cooperative Transportation by Teams of Quadrotors
his paper deals with the control of a team of unmanned air vehicles (UAVs), specifically quadrotors, for which their mission is the transportation of a deformable linear object (DLO), i.e., a cable, hose or similar object in quasi-stationary state, while cruising towards destination. Such missions have strong industrial applications in the transportation of hoses or power cables to specific locations, such as the emergency power or water supply in hazard situations such as fires or earthquake damaged structures. This control must be robust to withstand strong and sudden wind disturbances and remain stable after aggressive maneuvers, i.e., sharp changes of direction or acceleration. To cope with these, we have previously developed the online adaptation of the proportional derivative (PD) controllers of the quadrotors thrusters, implemented by a fuzzy logic rule system that experienced adaptation by a stochastic gradient rule. However, sagging conditions appearing when the transporting drones are too close or too far away induce singularities in the DLO catenary models, breaking apart the control system. The paper’s main contribution is the formulation of the hybrid selective model of the DLO sections as either catenaries or parabolas, which allows us to overcome these sagging conditions. We provide the specific decision rule to shift between DLO models. Simulation results demonstrate the performance of the proposed approach under stringent conditions.This work has been partially supported by spanish MICIN project PID2020-116346GB-I00, and project KK-2021/00070 of the Elkartek 2021 funding program of the Basque Government. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 777720
Control Synthesis for an Underactuated Cable Suspended System Using Dynamic Decoupling
This article studies the dynamics and control of a novel underactuated
system, wherein a plate suspended by cables and with a freely moving mass on
top, whose other ends are attached to three quadrotors, is sought to be
horizontally stabilized at a certain height, with the ball positioned at the
center of mass of the plate. The freely moving mass introduces a 2-degree of
underactuation into the system. The design proceeds through a decoupling of the
quadrotors and the plate dynamics. Through a partial feedback linearization
approach, the attitude of the plate and the translational height of the plate
is initially controlled, while maintaining a bounded velocity along the and
directions. These inputs are then synthesized through the quadrotors with a
backstepping and timescale separation argument based on Tikhonov's theorem
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