Determination of the Six Degrees of Freedom of a Moving Civil-Engineering Vehicle

The development of multirotor vehicles can often be a dangerous and costly undertaking due to the possibility of crashes resulting from faulty controllers. The matter of safety in such activities has primarily been addressed through the use of testbeds. However, testbeds for testing multirotor vehicles with suspended loads have previously not been reported. In this study, a simple yet novel testing platform was designed and built to aid in testing and evaluating the performances of multirotor flying vehicles, including vehicles with suspended loads. The platform allows the flying vehicle to move with all six degrees of freedom (DOF). Single or three-DOF motions can also be performed. Moreover, the platform was designed to enable the determination of the mass properties (center of mass and moments of inertia) of small multirotor vehicles (which are usually required in the development of new control systems). The applicability of the test platform for the in-flight performance testing of a multirotor vehicle was successfully demonstrated using a Holybro X500 quadcopter with a suspended load. The test platform was also successfully used to determine the mass properties of the vehicle.

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In-situ measurement technologies for flow behaviour and contact status of fibre-reinforced thermoplastics during forming with a six degree of freedom press

MATEC Web of Conferences ◽

10.1051/matecconf/201819007004 ◽

2018 ◽

Vol 190 ◽

pp. 07004

Author(s):

Birk Wonnenberg ◽

Franz Dietrich ◽

Klaus Dröder

Keyword(s):

Degrees Of Freedom ◽

Optical Measurements ◽

Image Processing Algorithm ◽

Forming Process ◽

Contact State ◽

Six Degrees Of Freedom ◽

Reinforced Plastics ◽

Reinforced Thermoplastics ◽

Six Degree Of Freedom

The paper presents investigations on a forming process, which is implemented in a forming press based on a Stewart platform. In contrast to common forming techniques, this buildup offers not only one but six degrees of freedom. This is of particular interest when it comes to the forming of materials that show significant anisotropic behaviour such as fibre-reinforced plastics. Therefore, an experimental setup is presented to record characteristic variables during the forming process of fibre-reinforced thermoplastics. The contact state is of particular interest for this kind of forming process because it changes continuously in shape and position as the forming process progresses. For this purpose, temperatures at different places in the tool are recorded to provide information about the flow velocity of the material and the contact state between tool and workpiece. This allows the determination of the exact time and position of the contact between material and forming tool as well as the duration of this contact. The results are compared with optical measurements analysed by image processing algorithm and process forces measured by load cells.

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A Six-Degree-of-Freedom Test System for the Study of Joint Mechanics and Ligament Forces

Journal of Biomechanical Engineering ◽

10.1115/1.2794196 ◽

1995 ◽

Vol 117 (4) ◽

pp. 383-389 ◽

Cited By ~ 6

Author(s):

J. M. Hollis

Keyword(s):

Degrees Of Freedom ◽

Test System ◽

Testing System ◽

Joint Mechanics ◽

Six Degrees Of Freedom ◽

Position Feedback ◽

Six Degree Of Freedom ◽

Good Agreement

A joint testing system was designed to transmit a specified motion or force to a joint in all six degrees of freedom (d.o.f.) using a spatial linkage system for position feedback. The precise reproducibility of position provided by this method of position feedback allows determination of in situ ligament forces for external joint loadings. Load on the structure of interest is calculated from six d.o.f. load cell output after the loaded position is reproduced with all other structures removed. In a test of this system, measured loads showed good agreement with applied loads.

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A Gyro-Free System for Measuring the Parameters of Moving Objects

Measurement Science Review ◽

10.2478/msr-2014-0036 ◽

2014 ◽

Vol 14 (5) ◽

pp. 263-269 ◽

Cited By ~ 3

Author(s):

Dimitar Dichev ◽

Hristofor Koev ◽

Totka Bakalova ◽

Petr Louda

Keyword(s):

Degrees Of Freedom ◽

Moving Objects ◽

Measuring System ◽

Measurement Channel ◽

Measuring Instruments ◽

Additional Measurement ◽

Free System ◽

Six Degrees Of Freedom ◽

Measurement Concept

Abstract The present paper considers a new measurement concept of modeling measuring instruments for gyro-free determination of the parameters of moving objects. The proposed approach eliminates the disadvantages of the existing measuring instruments since it is based, on one hand, on a considerably simplified mechanical module, and on the other hand, on the advanced achievements in the area of nanotechnologies, microprocessor and computer equipment. A specific measuring system intended for measuring the trim, heel, roll, and pitch of a ship has been developed in compliance with the basic principles of this concept. The high dynamic accuracy of this measuring system is ensured by an additional measurement channel operating in parallel with the main channel. The operating principle of the additional measurement channel is based on an appropriate correction algorithm using signals from linear MEMS accelerometers. The presented results from the tests carried out by means of stand equipment in the form of a hexapod of six degrees of freedom prove the effectiveness of the proposed measurement concept

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Determination of Hydrodynamic Parameters for Remotely Operated Vehicles

Volume 7: Ocean Engineering ◽

10.1115/omae2016-54642 ◽

2016 ◽

Cited By ~ 6

Author(s):

Ole A. Eidsvik ◽

Ingrid Schjølberg

Keyword(s):

Numerical Simulations ◽

Degrees Of Freedom ◽

Analytical Data ◽

Relative Difference ◽

Accurate Estimate ◽

Six Degrees Of Freedom ◽

Hydrodynamic Parameters ◽

Planar Motion Mechanism ◽

Rotational Degrees Of Freedom

In this paper the hydrodynamic parameters that characterize the behavior of a typical unmanned underwater vehicle are evaluated. A complete method for identifying these parameters is described. The method is developed to give a brief and accurate estimate of these parameters in all six degrees of freedom using basic properties of the vehicle such as dimensions, mass and shape. The method is based on both empirical and analytical results for typical reference geometries (ellipsoids, cubes, etc.). The method is developed to be applicable for a wide variety of UUV designs as these typically varies substantially. The method is then applied to a small observation class ROV. The results are first verified using an experimental method in which the full scale ROV is towed using a planar motion mechanism. An additional verification is performed with numerical simulations using Computational Fluid Dynamics and a radiation/diffraction program. The method shows promising results for both damping and added mass for the tested case. The translational degrees of freedom are more accurate than the rotational degrees of freedom which are expected as most empirical and analytical data are for translational degrees of freedom. The case study also reveals that the relative difference between the numerical simulations and the experimental results are similar to the relative difference between the proposed method and the experiment.

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Recent Contributions Under the Bureau of Ships Fundamental Hydromechanics Research Program

Journal of Ship Research ◽

10.5957/jsr.1959.3.2.47 ◽

1959 ◽

Vol 3 (02) ◽

pp. 47-64

Author(s):

M. St. Denis ◽

J.P. Craven

Keyword(s):

Research Program ◽

Degrees Of Freedom ◽

Bending Moment ◽

Elastic Response ◽

Inertial System ◽

Ship Motions ◽

Six Degrees Of Freedom ◽

The Third ◽

Ship Performance

The third main nautical objective, Seakeeping, refers to that aspect of ship performance in which the seaway enters in a dominant manner and affects fundamentally the character of the problem. In the section on Control [3],1 a pattern was introduced according to which seakeeping was related to the uncontrolled as well as the controlled oscillations which take place with reference to a ship's inertial system. But, more broadly speaking, seakeeping includes all of the following subjects:Description of the seaway.Determination of the forces imposed by the seaway on the vessel—the excitation (hydrodynamic loadings, wave bending moment, slamming forces, and so on).Determination of the response of the ship in her six degrees of freedom (ship motions).Prediction of the perils to which a ship may be exposed (capsizing, foundering, safety at sea).Prediction of the loss in speed she will sustain in heavy weather.Evaluation of the amount of stabilization necessary to prevent unacceptable or undesirable displacements and accelerations. The elastic response and strength of a vessel's structure, though not included under seakeeping, depend, nevertheless, in an essential manner thereon.

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A new methodology for the determination of the workspace of six-DOF redundant parallel structures actuated by nine wires

Robotica ◽

10.1017/s0263574706003055 ◽

2006 ◽

Vol 25 (1) ◽

pp. 113-120 ◽

Cited By ~ 27

Author(s):

Carlo Ferraresi ◽

Marco Paoloni ◽

Francesco Pescarmona

Keyword(s):

Degrees Of Freedom ◽

New Method ◽

Parallel Structure ◽

Graphical Form ◽

Six Degrees Of Freedom ◽

Parallel Structures ◽

Six Dof ◽

Force Reflection ◽

Master Device

The WiRo-6.3 is a six-degrees of freedom (six-DOF) robotic parallel structure actuated by nine wires, whose characteristics have been thoroughly analyzed in previous papers in reference. It is thought to be a master device for teleoperation; thus, it is moved by an operator through a handle and can convey a force reflection on the operator's hand. A completely new method for studying the workspace of this device, and of virtually any nine-wire parallel structure actuated by wire is presented and discussed, and its results are given in a graphical form.

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Effects of diffraction and radiation on a submerged sphere

International Journal of Mathematics and Mathematical Sciences ◽

10.1155/s0161171201007955 ◽

2001 ◽

Vol 28 (9) ◽

pp. 499-515

Author(s):

Matiur Rahman

Keyword(s):

Degrees Of Freedom ◽

Diffraction Problem ◽

Fluid Motion ◽

Radiation Condition ◽

Finite Depth ◽

Complex Nature ◽

Regular Waves ◽

Six Degrees Of Freedom ◽

Submerged Sphere

This paper deals with an investigation of the effects of diffraction and radiation on a submerged sphere in water of finite depthd. We assume that the fluid is homogeneous, inviscid, and incompressible, and the fluid motion is irrotational. In real situations, the submerged sphere will experience six degrees of freedom (i.e., motions); three translational and three rotational. In this paper, however, we consider a very idealized situation because of the complex nature of the physical problem. Two important motions, namely, the surge (horizontal oscillations) and the heave (vertical oscillations) motions are studied. Our attention is mainly focused on the hydrodynamic coefficients of these motions. The crux of the problem lies entirely on the determination of these coefficients which are inherently related to the determination of the motions of the submerged sphere in regular waves. This type of problem is usually solved by using potential theory, and mathematically, we look for the solution of a velocity potential which satisfies Laplace's equation along with the free surface, body surface, and bottom boundary conditions in conjunction with a radiation condition. This boundary value problem, in fact, consists of two separate problems: (a) diffraction problem and (b) radiation problem.

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First deep underground observation of rotational signals from an earthquake at teleseismic distance using a large ring laser gyroscope

Annals of Geophysics ◽

10.4401/ag-6970 ◽

2016 ◽

Vol 59 ◽

Author(s):

Andreino Simonelli ◽

Jacopo Belﬁ ◽

Nicolò Beverini ◽

Giorgio Carelli ◽

Angela Di Virgilio ◽

...

Keyword(s):

Ring Laser ◽

Degrees Of Freedom ◽

Fundamental Interest ◽

Rotational Seismology ◽

Six Degrees Of Freedom ◽

Large Ring ◽

Ring Laser Gyroscope ◽

Deep Underground ◽

Rotational Motions

<div class="page" title="Page 1"><div class="layoutArea"><div class="column"><p><span>Recent advances in large ring laser gyroscopes (RLG) technologies opened the possibility to observe rotations of the ground with sensitivities up to 10−11 rad/sec over the frequency band of seismological interest (0.01-1Hz), thus opening the way to a new geophysical discipline, i.e. rotational seismology. A measure of rotations in seismology is of fundamental interest for (a) the determination of all the six degrees of freedom that characterize a rigid body’s motion, and (b) the quantitative estimate of the rotational motions contaminating ground translation measurements obtained from standard seismometers. Within this framework, this paper presents and describes GINGERino, a new large observatory-class RLG located in Gran Sasso underground laboratory (LNGS), one national laboratories of the INFN (Istituto Nazionale di Fisica Nucleare). We also report unprecedented observations and analyses of the roto-translational signals from a tele-seismic event observed in such a deep underground environment. </span></p></div></div></div>

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Three-Dimensional Harmonic Vibrations of a Circular Beam

Journal of Applied Mechanics ◽

10.1115/1.3167628 ◽

1984 ◽

Vol 51 (2) ◽

pp. 375-382 ◽

Cited By ~ 1

Author(s):

D. E. Panayotounakos ◽

P. S. Theocaris

Keyword(s):

Degrees Of Freedom ◽

Three Dimensional ◽

Analytical Treatment ◽

Six Degrees Of Freedom ◽

Harmonic Vibrations ◽

Differential Element ◽

Circular Beam ◽

Partial Linear ◽

Linear Differential

In this paper an analytical treatment for the determination of the natural frequencies of a circular uniform beam, subjected to three-dimensional harmonic loads, is presented. Each differential element of the beam has six degrees of freedom, i.e., three translations and three rotations. This problem, in the most general case of response, is associated with a partial linear differential system composed of four coupled 3 × 1 vectorial equations. The influences of transverse shear deformation and rotatory inertia are also included in the analysis. The aforementioned solution methodology is successfully demonstrated through several numerical results.

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