Dynamics of a Spinning Disk

2016 ◽  
Vol 83 (6) ◽  
Author(s):  
Daolin Ma ◽  
Caishan Liu
Keyword(s):  
Coulomb Friction ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Classical Mechanics ◽  
Rolling Friction ◽  
Friction Model ◽  
Rolling Velocity ◽  
Six Degrees Of Freedom ◽  
Spinning Disk ◽  
Coulomb Friction Law

A spinning disk on a rough horizontal surface is a familiar example presented in the textbooks of classical mechanics. Recent studies have revealed that this simple system would exhibit an intriguing phenomenon that cannot be well examined by existing theories. Reason for that is due to the lack of reasonable understanding for the influence of combined sliding and rolling friction on the disk dynamics. To unveil how the two types of friction affect the disk motion, this paper presents a combined investigation of experiments and simulations on the dynamics of a spinning disk. We employed a pair of high-speed cameras to perform omnidirectional measurements for the six degrees-of-freedom in describing the disk motion. Numerical calculations are implemented under an integrated model including both the Coulomb friction law and a viscous rolling friction model. Exposure for the details of the disk motion in experiments and simulations sheds light on a novel mechanism underlying the rolling friction: the rolling friction exhibits viscosity relating to the square of rolling velocity.

Design, Construction and Control of a Remotely Operated Vehicle (ROV)

2011 ◽  
Author(s):  
Alireza Marzbanrad ◽  
Jalil Sharafi ◽  
Mohammad Eghtesad ◽  
Reza Kamali
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Remotely Operated Vehicle ◽  
Six Degrees Of Freedom ◽  
Depth Sensors ◽  
Control Schemes ◽  
On Line ◽  
Operation Unit ◽  
And Control ◽  
Design Construction

This is report of design, construction and control of “Ariana-I”, an Underwater Remotely Operated Vehicle (ROV), built in Shiraz University Robotic Lab. This ROV is equipped with roll, pitch, heading, and depth sensors which provide sufficient feedback signals to give the system six degrees-of-freedom actuation. Although its center of gravity and center of buoyancy are positioned in such a way that Ariana-I ROV is self-stabilized, but the combinations of sensors and speed controlled drivers provide more stability of the system without the operator involvement. Video vision is provided for the system with Ethernet link to the operation unit. Control commands and sensor feedbacks are transferred on RS485 bus; video signal, water leakage alarm, and battery charging wires are provided on the same multi-core cable. While simple PI controllers would improve the pitch and roll stability of the system, various control schemes can be applied for heading to track different paths. The net weight of ROV out of water is about 130kg with frame dimensions of 130×100×65cm. Ariana-I ROV is designed such that it is possible to be equipped with different tools such as mechanical arms, thanks to microprocessor based control system provided with two directional high speed communication cables for on line vision and operation unit.

Design and Testing Outline for a Free Running Model of a High Speed Craft

2020 ◽  
Author(s):  
Xinguo Wang ◽  
Jack Bonoli ◽  
Madeline Cohen ◽  
Mirjam Fürth
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Six Degrees Of Freedom ◽  
High Interest ◽  
Outdoor Environments ◽  
Free Running ◽  
Industry Professionals ◽  
Design And Testing ◽  
Very High ◽  
Testing Plan

Hydrodynamics of High Speed Craft is a topic of very high interest for recreational boaters and industry professionals alike. This project aims to be a first step toward conducting such experiments in exposed outdoor environments. This paper will outline a preliminary design and testing plan of a free running model of a high speed craft. The proposed free running model will be subjected to all six degrees of freedom, self propelled, autonomously controlled, and will be exposed to weather elements.

Theory and Method of Dynamic Modeling for Multilayer Vibration Isolation System

2000 ◽  
Author(s):  
Liao Dao-Xun ◽  
Lu Yong-Zhong ◽  
Huang Xiao-Cheng
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Vibration Isolation ◽  
Rigid Bodies ◽  
Design Calculation ◽  
Isolation System ◽  
Dry Land ◽  
Vibration Isolation System ◽  
Six Degrees Of Freedom ◽  
Floating Raft

Abstract The multilayer vibration isolation system has been widely applied to isolate vibration in dynamic devices of ships, high-speed vehicles forging hammer and precise instruments. The paper is based on the coordinate transformation of space general motion for mass blocks (rigid bodies) and Lagrangian equation of multilayer vibration isolation system. It gives a strict mathematical derivation on the differential equation of the motion for the system with six degrees of freedom of relative motion between mass blocks (including base). The equations are different from the same kind of equations in the reference literatures. It can be used in the floating raft of ships in order to isolates vibration and decrease noise, also used in design calculation of the multilayer vibration isolation for dynamic machines and precise instruments on the dry land.

Heading control of a novel finless high-speed supercavitating vehicle with an internal oscillating pendulum

2020 ◽  
pp. 107754632094834
Author(s):  
Mojtaba Mirzaei ◽  
Hossein Taghvaei
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Sliding Mode ◽  
Six Degrees Of Freedom ◽  
Supercavitating Vehicles ◽  
Supercavitating Vehicle ◽  
High Speeds ◽  
Heading Control ◽  
Heading Angle ◽  
Control Surfaces

High-speed supercavitating vehicles are surrounded by a huge cavity of gas and only a small portion of the nose and the tail of the vehicle are in contact with the water which leads to a considerable reduction in skin friction drag and reaching very high speeds. High-speed supercavitating vehicles are usually controlled by the cavitator at the nose which controls the pitch and depth of the vehicle and the control surfaces or fins which control the roll and heading angle of the vehicle using the bank-to-turn maneuvering method. However, control surfaces have disadvantages such as the high drag force and ineffectiveness due to the supercavity. Therefore, the purpose of the present study is to eliminate the fins from high-speed supercavitating vehicles and propose a new bank-to-turn heading control of this novel finless high-speed supercavitating vehicle which is composed of the cavitator at the nose and an oscillating pendulum as the internal actuator. Sliding mode control as a robust method is used for the six-degrees-of-freedom model of this finless high-speed vehicle against exposed disturbances. Some design criteria for the design of the internal pendulum in this finless supercavitating vehicle are presented for the damping coefficient, pendulum mass, and radius.

An Experiment for the Study of Free-Flying Supercavitating Projectiles

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Peter J. K. Cameron ◽  
Peter H. Rogers ◽  
John W. Doane ◽  
David H. Gifford
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Measurement Techniques ◽  
Theoretical Models ◽  
Dynamics Simulation ◽  
Small Scale ◽  
Successful Operation ◽  
Six Degrees Of Freedom ◽  
Impact Location ◽  
Simulation Based

Applications and research utilizing supercavitation for high-speed underwater flight has motivated study of the phenomenon. In this work, a small scale laboratory experiment for studying supercavitating projectiles has been designed, built, and tested. Similar existing experimental work has been documented in literature but using large, elaborate facilities, or has been presented with ambiguous conclusions from test results. The projectiles were 63.5 mm in length and traveled at speeds on the order of 145 m/s. Measurement techniques are discussed and used to record projectile speed, supercavity dimensions, and target impact location. Experimental observations are compared with a six degrees-of-freedom dynamics simulation based on theoretical models presented in literature for predicting supercavity shape and hydrodynamic forces on the supercavitating projectile during flight. Experimental observations are discussed qualitatively, along with quantitative statistics of the measurements made. Successful operation of the experiment has been demonstrated and verified by agreement with theoretical models.

Measurement of Six Degrees of Freedom Head Kinematics in Impact Conditions Employing Six Accelerometers and Three Angular Rate Sensors (6aω Configuration)

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
Yun-Seok Kang ◽  
Kevin Moorhouse ◽  
John H. Bolte
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Angular Displacement ◽  
Angular Rate ◽  
Angular Acceleration ◽  
Head Impact ◽  
Six Degrees Of Freedom ◽  
Head Kinematics ◽  
Impact Tests ◽  
Remote Location

The ability to measure six degrees of freedom (6 DOF) head kinematics in motor vehicle crash conditions is important for assessing head-neck loads as well as brain injuries. A method for obtaining accurate 6 DOF head kinematics in short duration impact conditions is proposed and validated in this study. The proposed methodology utilizes six accelerometers and three angular rate sensors (6aω configuration) such that an algebraic equation is used to determine angular acceleration with respect to the body-fixed coordinate system, and angular velocity is measured directly rather than numerically integrating the angular acceleration. Head impact tests to validate the method were conducted using the internal nine accelerometer head of the Hybrid III dummy and the proposed 6aω scheme in both low (2.3 m/s) and high (4.0 m/s) speed impact conditions. The 6aω method was compared with a nine accelerometer array sensor package (NAP) as well as a configuration of three accelerometers and three angular rate sensors (3aω), both of which have been commonly used to measure 6 DOF kinematics of the head for assessment of brain and neck injuries. The ability of each of the three methods (6aω, 3aω, and NAP) to accurately measure 6 DOF head kinematics was quantified by calculating the normalized root mean squared deviation (NRMSD), which provides an average percent error over time. Results from the head impact tests indicate that the proposed 6aω scheme is capable of producing angular accelerations and linear accelerations transformed to a remote location that are comparable to that determined from the NAP scheme in both low and high speed impact conditions. The 3aω scheme was found to be unable to provide accurate angular accelerations or linear accelerations transformed to a remote location in the high speed head impact condition due to the required numerical differentiation. Both the 6aω and 3aω schemes were capable of measuring accurate angular displacement while the NAP instrumentation was unable to produce accurate angular displacement due to double numerical integration. The proposed 6aω scheme appears to be capable of measuring accurate 6 DOF kinematics of the head in any severity of impact conditions.

Friction Damping Modeling in High Stress Contact Areas Using Microslip Friction Model

2008 ◽  
Author(s):  
Francisco J. Marquina ◽  
Armando Coro ◽  
Alberto Gutie´rrez ◽  
Roberto Alonso ◽  
David J. Ewins ◽  
...  
Keyword(s):  
Coulomb Friction ◽  
High Stress ◽  
Friction Model ◽  
Imperial College ◽  
Rotor Blades ◽  
Contact Method ◽  
Friction Damping ◽  
Common Solution ◽  
Coulomb Friction Law ◽  
Microslip Friction

It is well known that friction is really important to reduce amplitudes of vibration of rotor blades. Underplatform dampers are a common solution for introducing friction damping, but there are also other friction damping sources on blades that are produced in places with high normal loads and small relative displacements (e.g. lockplates and blade-disc joints). Several approaches based on the classical Coulomb friction law have been used in order to model the friction damping at those interfaces, but their results are not accurate enough for those cases with small displacements where high normal loads appear. This paper presents simulations of typical cases of friction on rotor blades (underplatform dampers, lockplates and blade root) using a method based on macroslip and the method developed by ‘Industria de TurboPropulsores’ (ITP) based on microslip (InTerPart MIcroslip COntact method), and their comparison with experimental results obtained with several tests performed at Imperial College London (IC). The comparison shows that, for cases with high normal loads and small displacements, the ITPMICO method obtains further more accurate results than based-on-macroslip one.

A Dynamic Simulation of Wave Impact Loads on Offshore Floating Platforms

1976 ◽  
Vol 98 (2) ◽  
pp. 550-557
Author(s):  
J. G. Giannotti
Keyword(s):  
Structural Analysis ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Impulsive Loading ◽  
Impact Loads ◽  
Offshore Platforms ◽  
Wave Impact ◽  
Six Degrees Of Freedom ◽  
Marine Vehicles ◽  
Floating Platforms

Some of the most critical loads to consider in developing design criteria for offshore platforms are those caused by wave hydrodynamic impact. The effect of these loads can be of a local nature in the form of plating damage as a result of impulsive loading, or it can be felt on the overall structure in the form of induced vibration, and increased bending moments and shears. Traditionally, the prediction of these loads has been highly empirical and designers have had to rely heavily on conservative factors of safety in order to account for the lack of confidence in these predictions. The current degree of sophistication of advanced techniques of structural analysis such as the finite element method has not been matched by equally sophisticated loads prediction methods. Consequently, the advantages offered by the computerized structural analysis schemes are considerably reduced due to the unacceptable load inputs. This paper fills part of this void by presenting an analytical model for predicting wave impact loads for the design of offshore platforms. The method is based on the Payne Impact Program which has been used before for predicting impact pressures and loads acting on high speed marine vehicles. The model simulates six-degrees-of-freedom and allows impacts at any wave heading. As inputs it requires geometric information, sea state definition, and a description of the relative motion of platform and wave. It is particularly suited to allow analysis of the results in probabilistic form, so that the severity and frequency of occurrence of impacts can be predicted.

Multiple-Body Collision Algorithms for Computational Simulation of High-Speed Air-Delivered Systems

2015 ◽  
Vol 17 (2) ◽  
pp. 564-593 ◽  
Author(s):  
Robert E. Harris ◽  
Peter A. Liever ◽  
Edward A. Luke ◽  
Jonathan G. Dudley
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Computational Simulation ◽  
Rigid Bodies ◽  
Flight Simulation ◽  
Dispersion Pattern ◽  
Reduced Order ◽  
Six Degrees Of Freedom ◽  
Collision Response ◽  
Engineering Level

AbstractCurrently, there exists a lack of confidence in the computational simulation of multiple body high-speed air delivered systems. Of particular interest is the ability to accurately predict the dispersion pattern of these systems under various deployment configurations. Classical engineering-level methods may not be able to predict these patterns with adequate confidence due primarily to accuracy errors attributable to reduced order modeling. In the current work, a new collision modeling capability has been developed to enable multiple-body proximate-flight simulation in the Loci/CHEM framework. This approach maintains high-fidelity aerodynamics and incorporates six degrees of freedom modeling with collision response, and is well-suited for simulation of a large number of projectiles. The proposed simulation system is intended to capture the strong interaction phase early in the projectile deployment, with subsequent transfer of projectile positions and flight states to the more economical engineering-level methods. Collisions between rigid bodies are modeled using an impulse-based approach with either an iterative propagation method or a simultaneous method. The latter is shown to be more accurate and robust for cases involving multiple simultaneous collisions as it eliminates the need to sort and resolve the collisions sequentially. The implementation of both the collision detection methodology and impact mechanics are described in detail with validation studies to demonstrate the efficiency and accuracy of the developed technologies. The studies chronologically detail the findings for simulating simple impacts and collisions between multiple bodies with aerodynamic interference effects.

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