China
Africa
Explore chapters and articles related to this topic
Articulated Towers
Published in Patrick Bar-Avi, Haym Benaroya, Nonlinear Dynamics of Compliant Offshore Structures, 2017
Patrick Bar-Avi, Haym Benaroya
This problem has similarities to that of an inverted spherical pendulum with additional considerations;Buoyancy force is included.Drag force, proportional to the square of the relative velocity between the fluid and the tower, needs to be considered.Fluid inertia and added mass forces due to fluid and tower acceleration are part of the loading environment.Vortex shedding and wave slamming forces are considered.Current and wind forces are included.Earth angular velocity is included.
Deployment, Station-Keeping, and Retrieval of a Flexible Tether Connecting a Satellite to the Shuttle
Published in Arun K. Banerjee, Flexible Multibody Dynamics, 2022
The purpose of having a shuttle-borne tethered satellite is, of course, to do station-keeping, with a small satellite to look at the earth from an altitude where the satellite cannot stay by itself due to atmospheric drag. The analysis presented here is based on Ref. [8]. Consider the spherical pendulum shown in Figure 2.13. Let it represent a rigid rod model of a tether of length L attached to an orbiting body moving in a circular orbit with angular speed ω. Rotations through an orbit in-plane angle θ followed by an out-of-plane angle ϕ describe the orientation of the tether. To keep the angles θ and ϕ small, we consider a pumping control of the tether, much like a yo-yo toy.
Static and dynamic accuracy determination of a three-dimensional motion analysis system
Published in Steve Haake, The Engineering of Sport, 2020
L.W. Alaways, M. Hubbard, T. M. Conlan, J.A. Miles
Because it is somewhat unsatisfying to use static accuracy calculations as estimates of the tracking accuracy for targets in motion, we need a test target which moves. In addition, its motion must be known very precisely. The target can then be tracked experimentally and the trajectory compared with the theoretical motion to determine directly the dynamic tracking accuracy. The known trajectory should be fully three-dimensional motion and have frequency content comparable to the targets for which the standard is being developed. A spherical pendulum fits these requirements.
Modelling and control of a spherical pendulum via a non–minimal state representation
Published in Mathematical and Computer Modelling of Dynamical Systems, 2021
Ricardo Campa, Israel Soto, Omar Martínez
Let us define , with , as the vector of joint coordinates of the spherical pendulum. Moreover, let be the Euler parameters describing the orientation of the pendulum frame with respect to the base frame, as a function of . Thus, according to (14) and the composition rule for rotations mentioned in the previous section, can be computed by as
A Smart Tower Crane to Mitigate Turbulent Wind Loads
Published in Structural Engineering International, 2021
Mohamed Hechmi El Ouni, Nabil Ben Kahla, Saiful Islam, Mohammed Jameel
In the literature, various approaches have been proposed by researchers to model tower crane dynamics. Ref. [3] introduced a flexible rotary crane with three kinds of motion (rotation, load hoisting, and boom hoisting), where only the joint between the boom and the jib was assumed to be flexible. Ref. [4] simplified the crane system to a pendulum subjected to several base excitations. Ref. [5] modeled the boom crane as a spherical pendulum with a lumped mass having two degrees of freedom. It was subjected to base excitations and the study reported the instabilities in the payload motion. Ref. [6] proposed a beam model based on a point mass carriage traversing a simply supported Euler–Bernoulli beam. Ref. [7] studied the dynamic behaviors of a tower crane using a rigid body model with discrete springs, assuming that the payload was suspended by a massless cable from a horizontally moving support. Ref. [8] investigated the dynamic behavior of a tower crane under seismic excitation based on a model with three degrees of freedom. All these studies neglected the flexibility of the crane and they are generally based on assumptions and simplifications, which are appropriate for the analysis of the payload motion. However, when the objective is to analyze the structural dynamics of the tower crane, a more detailed modeling of the tower crane structure is required and its flexibility must be considered. Finite element modeling is widely used to model the crane using space truss or frame elements. Ref. [9] proposed a two-dimensional finite element model of a crane. Ref. [10] performed a finite element analysis of the frictional slip of slings in a heavy lift. Ref. [11] studied the modal properties and dynamic responses of tower cranes by the linear finite element method taking into account the cable passages over intermediate pulleys, which significantly affect the static tensions and dynamic properties of tower cranes. Ref. [12] performed free vibration analysis of a tower crane using commercial finite element software. Ref. [13] performed the numerical and experimental dynamic analysis of a tower crane to determine the dynamic properties. Ref. [14] performed the dynamic analysis of a tower crane jib using ANSYS. Ref. [15] studied the wind-induced vibration response of a tower crane based on the linear virtual excitation method. Ref. [16] studied the fatigue behavior of a tower crane by the finite element method.