Double‐pendulum vibration isolator with three‐dimensional isolation

Newly developed miniature wireless inertial measurement units (IMUs) hold great promise for measuring and analyzing multibody system dynamics. This relatively inexpensive technology enables non-invasive motion tracking in broad applications, including human motion analysis. The second part of this two-part paper advances the use of an array of IMUs to estimate the joint reactions (forces and moments) in multibody systems via inverse dynamic modeling. In particular, this paper reports a benchmark experiment on a double-pendulum that reveals the accuracy of IMU-informed estimates of joint reactions. The estimated reactions are compared to those measured by high precision miniature (6 dof) load cells. Results from ten trials demonstrate that IMU-informed estimates of the three dimensional reaction forces remain within 5.0% RMS of the load cell measurements and with correlation coefficients greater than 0.95 on average. Similarly, the IMU-informed estimates of the three dimensional reaction moments remain within 5.9% RMS of the load cell measurements and with correlation coefficients greater than 0.88 on average. The sensitivity of these estimates to mass center location is discussed. Looking ahead, this benchmarking study supports the promising and broad use of this technology for estimating joint reactions in human motion applications.

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Feasibility of Two-Dimensional Control for Ship-Mounted Cranes

Volume 6B: 18th Biennial Conference on Mechanical Vibration and Noise ◽

10.1115/detc2001/vib-21454 ◽

2001 ◽

Cited By ~ 1

Author(s):

Eihab M. Abdel-Rahman ◽

Ali H. Nayfeh

Keyword(s):

Natural Frequencies ◽

Three Dimensional ◽

Major Axis ◽

Double Pendulum ◽

Spherical Pendulum ◽

Safe Operation ◽

Control Effort ◽

Pendulum System ◽

Out Of Plane ◽

The One

Abstract We test the feasibility of employing an exclusively planar control effort to suppress unsafe ship-mounted crane pendulations induced by sea motions. The new crane configuration, designed to apply the control effort, is modeled and the proposed control effort, employing Coulomb friction and viscous damping, is applied. The three-dimensional nonlinear dynamics of the crane is then investigated. The new crane configuration, dubbed Maryland Rigging, transforms a crane from a single spherical pendulum to a double pendulum system. The upper pendulum, a pulley riding on a cable suspended from the boom, is constrained to move over an ellipsoid. The major axis of the ellipsoid is the boom and the foci are the two points at which the riding cable attaches to it. The lower pendulum, the payload suspended by a cable from the pulley, continues to act as a spherical pendulum. Due to the geometry of the ellipsoid, the natural frequencies of the crane in the plane of the boom (in-plane) are almost equal to the out-of-plane natural frequencies. The model is used to examine the response of a Maryland rigged crane to direct, in-plane, harmonic forcing. The frequency of the excitation is set almost equal to the crane’s lowest natural frequency. It is found that under this excitation and due to the one-to-one internal resonance between the lowest in-plane and out-of-plane natural frequencies, significant out-of-plane motions are induced by applying a purely in-plane forcing. Thus an in-plane control mechanism is not adequate for safe operation of the crane. To guarantee safe operation of a ship-mounted crane, one must apply both in-plane and out-of-plane control efforts.

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Accuracy of Wearable Sensors for Estimating Joint Reactions

Journal of Computational and Nonlinear Dynamics ◽

10.1115/1.4035667 ◽

2017 ◽

Vol 12 (4) ◽

Cited By ~ 2

Author(s):

Ryan S. McGinnis ◽

Jessandra Hough ◽

Noel C. Perkins

Keyword(s):

Degrees Of Freedom ◽

Wearable Sensors ◽

Three Dimensional ◽

Correlation Coefficients ◽

Human Motion ◽

Load Cell ◽

Great Promise ◽

Human Motion Analysis ◽

Double Pendulum ◽

Inverse Dynamic

Miniature wireless inertial measurement units (IMUs) hold great promise for measuring and analyzing multibody system dynamics. This relatively inexpensive technology enables noninvasive motion tracking in broad applications, including human motion analysis. This paper advances the use of an array of IMUs to estimate the joint reactions (forces and moments) in multibody systems via inverse dynamic modeling. In particular, this paper reports a benchmark experiment on a double-pendulum that reveals the accuracy of IMU-informed estimates of joint reactions. The estimated reactions are compared to those measured by high-precision miniature (6 degrees-of-freedom) load cells. Results from ten trials demonstrate that IMU-informed estimates of the three-dimensional reaction forces remain within 5.0% RMS of the load cell measurements and with correlation coefficients greater than 0.95 on average. Similarly, the IMU-informed estimates of the three-dimensional reaction moments remain within 5.9% RMS of the load cell measurements and with correlation coefficients greater than 0.88 on average. The sensitivity of these estimates to mass center location is discussed. Looking ahead, this benchmarking study supports the promising and broad use of this technology for estimating joint reactions in human motion applications.

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Two-Dimensional Control for Ship-Mounted Cranes: A Feasibility Study

Journal of Vibration and Control ◽

10.1177/1077546304031164 ◽

2003 ◽

Vol 9 (12) ◽

pp. 1327-1342 ◽

Cited By ~ 3

Author(s):

Eihab Abdel-Rahman ◽

Ali H Nayfeh

Keyword(s):

Natural Frequencies ◽

Three Dimensional ◽

Major Axis ◽

Double Pendulum ◽

Spherical Pendulum ◽

Safe Operation ◽

Control Effort ◽

Pendulum System ◽

Out Of Plane ◽

The One

We test the feasibility of employing an exclusively planar control effort to suppress unsafe ship-mounted crane pendulations induced by sea motions. The new crane configuration, designed to apply the control effort, is modeled and the proposed control effort, employing Coulomb friction and viscous damping, is applied. The three-dimensional nonlinear dynamics of the crane is then investigated. The new crane configuration, dubbed Maryland rigging, transforms a crane from a single spherical pendulum to a double pendulum system. The upper pendulum, a pulley riding on a cable suspended from the boom, is constrained to move over an ellipsoid. The major axis of the ellipsoid is the boom and the foci are the two points at which the riding cable attaches to it. The lower pendulum, the payload suspended by a cable from the pulley, continues to act as a spherical pendulum. Due to the geometry of the ellipsoid, the natural frequencies of the crane in the plane of the boom (in-plane) are almost equal to the out-of-plane natural frequencies. The model is used to examine the response of a Maryland rigged crane to direct, in-plane, harmonic forcing. The frequency of the excitation is set almost equal to the crane's lowest natural frequency. It is found that under this excitation and due to the one-to-one internal resonance between the lowest in-plane and out-of-plane natural frequencies, significant out-of-plane motions are induced by applying a purely in-plane forcing. Thus, an in-plane control mechanism is not adequate for safe operation of the crane. To guarantee safe operation of a ship-mounted crane, both in-plane and out-of-plane control efforts must be applied.

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Double‐pendulum vibration isolator or seismograph

Review of Scientific Instruments ◽

10.1063/1.1134904 ◽

1977 ◽

Vol 48 (11) ◽

pp. 1397-1399 ◽

Cited By ~ 4

Author(s):

Paul Lorrain

Keyword(s):

Double Pendulum ◽

Vibration Isolator

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3D Kinematics and Kinetics of the Golf Swing

International Journal of Sport Biomechanics ◽

10.1123/ijsb.1.3.221 ◽

1985 ◽

Vol 1 (3) ◽

pp. 221-232 ◽

Cited By ~ 46

Author(s):

Robert J. Neal ◽

Barry D. Wilson

Keyword(s):

Three Dimensional ◽

Golf Swing ◽

Joint Torque ◽

Double Pendulum ◽

Two Phase ◽

Joint Force ◽

Pendulum Model ◽

Angular Velocities ◽

Spatial Coordinates ◽

Kinematics And Kinetics

Three-dimensional kinematics and kinetics for a double pendulum model golf swing were determined for 6 subjects, who were filmed by two phase-locked Photosonics cameras. The film was digitally analyzed. Abdel-Aziz and Karara's (1971) algorithm was used to determine three-dimensional spatial coordinates for the segment endpoints. Linear kinematic and kinetic data showed similarities with previous studies. The orientation of the resultant joint force at the wrists was in the direction of motion of the club center of gravity for most of the downswing. Such an orientation of the force vector would tend to prevent wrist uncocking. Indeterminate peak angular velocities for rotations about the X axis were reported. However, these peaks were due to computational instabilities that occurred when the club was perpendicular to the YZ plane. Furthermore, the motion of the club during the downswing was found to be nonplanar. Wrist uncocking appeared to be associated with the resultant joint torque and not the resultant joint force at the wrists. Torques reported in this study were consistent with those reported by Vaughan (1981).

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Contrast Test Research on Application of Dry Friction Isolators to Vibration Isolation of Vehicle Electronic Devices

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.505-506.360 ◽

2014 ◽

Vol 505-506 ◽

pp. 360-364

Author(s):

Jun Fang Hou ◽

Rong Li Li ◽

Guang Chun Yu ◽

Tao Luo ◽

Hai Wen He

Keyword(s):

Dry Friction ◽

Vibration Isolation ◽

Electronic Device ◽

Electronic Devices ◽

Three Dimensional ◽

Wire Mesh ◽

Vibration Source ◽

Vibration Isolator ◽

Vibration Isolators ◽

Research On Application

As regards the reliability of the vehicle electronic devices on the tracklayer getting worse due to severe vibration, isolation theory and mechanical model of the GWF vibration isolator and wire-mesh vibration isolator were analyzed, and the test research on the isolation effectiveness of the two isolators applied to the isolation of the vehicle electronic devices were carried out. The test results show that the vibration source of the foundation of the electronic device is mainly from the structure resonance, and the two dry friction vibration isolators exhibit excellent isolation effectiveness on different roads and at different speed. The wire-mesh vibration isolator shows better performance than GWF vibration isolator on three-dimensional comprehensive isolation.

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