scholarly journals A network-based perspective on coherent structure detection from very-sparse Lagrangian data

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Giovanni Iacobello ◽  
David E. Rival
Keyword(s):  
Coherent Structure ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Coherent Motion ◽  
Modeling And Control ◽  
Structure Detection ◽  
Spatio Temporal ◽  
Lagrangian Data ◽  
And Control ◽  
Lagrangian Flow

Coherent structure detection (CSD) is a long-lasting issue in fluid mechanics research as the presence of spatio-temporal coherent motion enables simpler ways to characterize the flow dynamics. Such reducedorder representation, in fact, has significant implications for the understanding of the dynamics of flows, as well as their modeling and control (Hussain, 1986). While the Eulerian framework has been extensively adopted for CSD, Lagrangian coherent structures have recently received increasing attention, mainly driven by advancements in Lagrangian flow measurement techniques (Haller, 2015; Hadjighasem et al., 2017). Lagrangian particle tracking (LPT), in particular, is widely used nowadays due to its ability to quantity fluid-parcel trajectories in three-dimensional volumes (Schanz et al., 2016).

Decentralized Control of a Tower Crane

1999 ◽  
Author(s):  
Kiyoshi Takagi ◽  
Hidekazu Nishimura
Keyword(s):  
Decentralized Control ◽  
Three Dimensional ◽  
Reduced Order Model ◽  
Flexible Structure ◽  
Order Model ◽  
Modeling And Control ◽  
Reduced Order ◽  
Tower Crane ◽  
Three Dimensional Models ◽  
And Control

Abstract This paper deals with modeling and control of a crane mounted on a tower-like flexible structure. A fast transfer of the load causes the sway of the load rope and the vibration of the flexible structure. Our object is to control both the sway and the vibration by the inherent capability of the tower crane. This paper makes its three-dimensional models for simulation and reduced-order-model in order to design the decentralized control system. Then, we design the decentralized H∞ compensator and verify the efficiency by simulations and experiments.

scholarly journals Three-Dimensional Modeling and Control of a Tethered UAV-Buoy System

2021 ◽  
Author(s):  
Ahmad Kourani ◽  
Naseem Daher
Keyword(s):  
Control System ◽  
Three Dimensional ◽  
Vertical Motion ◽  
Robotic System ◽  
Three Dimensions ◽  
Spherical Coordinate ◽  
Nonlinear Dynamical ◽  
Modeling And Control ◽  
Three Dimensional Modeling ◽  
And Control

Abstract This work presents the nonlinear dynamical model and motion controller of a system consisting of an unmanned aerial vehicle (UAV) that is tethered to a floating buoy in the three-dimensional (3D) space. Detailed models of the UAV, buoy, and the coupled tethered system dynamics are presented in a marine environment that includes surface-water currents and oscillating gravity waves, in addition to wind gusts. This work extends the previously modeled planar (vertical) motion of this novel robotic system to allow its free motion in all three dimensions. Furthermore, a Directional Surge Velocity Control System (DSVCS) is hereby proposed to allow both the free movement of the UAV around the buoy when the cable is slack, and the manipulation of the buoy’s surge velocity when the cable is taut. Using a spherical coordinate system centered at the buoy, the control system commands the UAV to apply forces on the buoy at specific azimuth and elevation angles via the tether, which yields a more appropriate realization of the control problem as compared to the Cartesian coordinates where the traditional x- , y- , and z -coordinates do not intuitively describe the tether’s tension and orientation. The proposed robotic system and controller offer a new method of interaction and collaboration between UAVs and marine systems from a locomotion perspective. The system is validated in a virtual high-fidelity simulation environment, which was specifically developed for this purpose, while considering various settings and wave scenarios.

Elliptic jets. Part 3. Dynamics of preferred mode coherent structure

1993 ◽  
Vol 248 ◽  
pp. 315-361 ◽  
Author(s):  
Hyder S. Husain ◽  
Fazle Hussain
Keyword(s):  
Coherent Structure ◽  
Near Field ◽  
Three Dimensional ◽  
Mixing Enhancement ◽  
Hot Wire ◽  
Vortical Structures ◽  
Mass Entrainment ◽  
Time Average ◽  
And Control ◽  
Made In

The dynamics of the preferred mode structure in the near field of an elliptic jet have been investigated using hot-wire measurements. A 2:1 aspect ratio jet with an initially turbulent boundary layer and a constant momentum thickness all around the nozzle exit perimeter was used for this study. Measurements were made in air at a Reynolds number ReDe (≡ UeDe/v) = 3.5 × 104. Controlled longitudinal excitation at the preferred mode frequency (StDe ≡ fDe/Ue = 0.4) induced periodic formation of structures, allowing phase-locked measurements with a local trigger hot wire. The dynamics of the organized structure are examined from educed fields of coherent vorticity and incoherent turbulence in the major and minor symmetry planes at five successive phases of evolution, and are also compared with corresponding data for a circular jet. Unlike in a circular jet, azimuthally fixed streamwise vortices (ribs) form without the aid of azimuthal forcing. The three-dimensional deformation of elliptic vortical structures and the rib formation mechanism have also been studied through direct numerical simulation. Differential self-induced motions due to non-uniform azimuthal curvature and the azimuthally fixed ribs produce greater mass entrainment in the elliptic jet than in a circular jet. The turbulence production mechanism, entrainment and mixing enhancement, and time-average measures and their modification by excitation are also discussed in terms of coherent structure dynamics and the rib-roll interaction. Various phase-dependent and time-average turbulence measures documented in this paper should serve as target data for validation of numerical simulations and turbulence modelling, and for design and control purposes in technological applications. Further details are given by Husain (1984).

scholarly journals Modeling and Control of Underactuated Three-Dimensional Overhead Crane Systems

2021 ◽  
Vol 6 ◽  
pp. 80-85
Author(s):  
Magdi S. Mahmoud ◽  
Nezar M. Alyazidi ◽  
Abdalrahman M. Hassanine
Keyword(s):  
Three Dimensional ◽  
Vital Role ◽  
Overhead Crane ◽  
Modeling And Control ◽  
Recent Developments ◽  
Heavy Loads ◽  
And Control ◽  
Future Work

Overhead crane systems play a vital role in different factories to transport heavy loads. This paper provides an overview of recent developments in the modeling and control of three-dimensional overhead crane systems. It provides a categorized survey of the published work. Different control methodologies when applied to overhead crane are examined, outlined and assessed to aid for future work.

Three-Dimensional Dynamic Modeling and Control of Off-Centered Bridge Crane Lifts

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Anthony Garcia ◽  
William Singhose ◽  
Aldo Ferri
Keyword(s):  
Dynamic Model ◽  
Dynamic Modeling ◽  
Three Dimensional ◽  
Horizontal Motion ◽  
Bridge Crane ◽  
Suspension Point ◽  
Modeling And Control ◽  
Surrounding Environment ◽  
And Control

When cranes lift payloads off the ground, the payload may slide sideways or swing unexpectedly. This motion occurs when the payload is not directly beneath the overhead suspension point of the hoist cable. Given that cable suspension points can be hundreds of feet above the payload, it is difficult for crane operators to know if the hoist cable is vertical before lifting the payload off the ground. If an off-center lift creates substantial horizontal motion, then it can create significant hazards for the operators, the payload, and the surrounding environment. This paper develops a three-dimensional dynamic model that predicts motions of off-centered lifts.

Dynamics and control of three-dimensional dual cranes transporting a bulky payload

2020 ◽  
pp. 095440622094957
Author(s):  
Jie Huang ◽  
Kuo Zhu
Keyword(s):  
Dynamic Behavior ◽  
Nonlinear Model ◽  
Control Method ◽  
Three Dimensional ◽  
Structural Flexibility ◽  
Positioning Accuracy ◽  
Modeling And Control ◽  
Input Shaper ◽  
Dynamics And Control ◽  
And Control

The inevitable oscillations of the payload decrease the positioning accuracy and lessen the safety in dual cranes carrying a large payload. In the presence of the structural flexibility, the dynamics of dual cranes are governed by the payload swing, pitch, and twisting after considering three-dimensional motions. However, little research has been directed at the modeling and control of three-dimensional dual cranes. A dynamic model of three-dimensional dual cranes including the payload swing, pitch and twisting is described. Moreover, a combined modified extra-insensitive input shaper and four-pieces smoother method is proposed to control the swing, pitch, and twisting of the payload. The dynamic behavior of the nonlinear model and the effectiveness of the new control method are verified experimentally on dual cranes carrying a slender beam.

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