Case Studies on the Use of Two and Three Degree of Freedom Models to Understand Fundamental Vibration Behavior of Complex Systems

2014 ◽  
Author(s):  
Ryan D. Hodge ◽  
Caner Demirdogen
Keyword(s):  
Complex System ◽  
Natural Frequency ◽  
Lessons Learned ◽  
Degree Of Freedom ◽  
Modal Testing ◽  
Vibration Absorber ◽  
Engine Component ◽  
Three Degree Of Freedom ◽  
Base Structure ◽  
Simple Models

Mathematical models of simple two and three degree of freedom vibrating systems are beneficial to ease understanding of a complex system by providing an opportunity to readily identify the effect of one degree of freedom on another. When dealing with short timelines in industry, simple models provide the opportunity to quickly develop potential solutions to excessive vibration issues or understand unexpected results. Simple models are not always appropriate and may have significant uncertainties but such an option may still add value when compared to the time and effort required to develop larger, detailed models. This paper presents two cases regarding the use of simple models to develop understanding of a complex system. In each case, the focus is on the insights that can be gained from a simple model rather than the detailed calculations and calibrations necessary to ensure its complete accuracy. Case 1 employs a two degree of freedom system to relate how an experimental modal test of an engine component can be affected by the base structure on which it is mounted. This study directly relates to the experimental modal testing of large engine components which are tested both in laboratories and on engines. Two charts are presented to evaluate the error of a measured natural frequency as a function of both the mass and natural frequency of the component to be tested and the base structure. Case 2 utilizes a three degree of freedom system built in a commercial finite element analysis (FEA) code and solved via a multi-disciplinary optimizer to determine the ideal parameters of a vibration absorber to effect the greatest possible reduction in vibration levels of a component. The lessons learned from this study are applicable to developing a vibration absorber to be installed on an engine component that is being excited by global modes of a generator set. Both cases display the significant lessons that can be learned from extremely simple systems.

scholarly journals Adaptive Torsional Tuned Vibration Absorber for Rotary Equipment

Vibration ◽  
2019 ◽  
Vol 2 (1) ◽  
pp. 116-134 ◽  
Author(s):  
Taher Abu Seer ◽  
Nader Vahdati ◽  
Oleg Shiryayev
Keyword(s):  
Natural Frequency ◽  
Degree Of Freedom ◽  
Vibration Absorber ◽  
Torsional Vibrations ◽  
Rotating System ◽  
Laboratory Test Results ◽  
Innovative Solution ◽  
Bond Graph Modeling ◽  
Rotary Equipment ◽  
Tuned Vibration Absorber

This paper proposes an innovative solution to suppress torsional vibrations in any rotating machinery with a variable frequency of excitation, or a variable natural frequency. The adaptive torsional tuned vibration absorber (ATTVA) was designed using an integrated electromagnetic circuit, which can adapt its natural frequency to match the varying natural frequency of any Multi Degree of Freedom (MDOF) rotating system. A two degree of freedom rotating system was modeled along with the integrated ATTVA using the bond graph modeling technique. Simulation results showed that torsional vibrations can be easily attenuated by controlling the capacitance shunted to the voice coil circuit. The ATTVA was designed, fabricated and evaluated on a test rig in the laboratory. Test results revealed good matching between the mathematical model and the experimental data. Experiments were performed with different configurations of the ATTVA, and the experimental results showed reasonable suppression in vibration magnitude at the desired frequency.

Optimal Parameters and Characteristics of a Three Degree of Freedom Dynamic Vibration Absorber

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Mariano Febbo
Keyword(s):  
Simulated Annealing ◽  
Vibration Reduction ◽  
Observation Point ◽  
Degree Of Freedom ◽  
Vibration Absorber ◽  
Optimal Parameters ◽  
Dynamic Vibration Absorber ◽  
Rotational Mode ◽  
Dynamic Vibration ◽  
Three Degree Of Freedom

The present study is devoted to the determination of the optimal parameters and characteristics of a three degree of freedom dynamic vibration absorber (3 DOF DVA) for the vibration reduction of a plate at a given point. The optimization scheme uses simulated annealing and constrained simulated annealing, which is capable of optimizing systems with a set of constraints. Comparisons between a 3 DOF DVA and multiple (5) 1 DOF DVAs show a better performance of the former for vibration reduction. Regarding the characteristics of the optimal 3 DOF DVA, numerical tests reveal that the absorber is robust under variations of the observation point and for 10% variations of its mass, stiffness and damping. From the analysis of parameter changes of the plate, it is found that the optimal 3 DOF DVA is almost insensitive to a mass change, and sensitive to a change of Young’s modulus for low frequencies. In this case, a decrease in Young’s modulus causes a decrease in its effectiveness, and an increase improves it. The study of the effect of the 3 DOF DVA location on its effectiveness reveals that the requirements of closeness of the absorber to an antinode of the bare primary structure and to the observation point improve its performance. Additionally, for a rotational mode of the 3-DOF DVA about some axis, the effectiveness of the absorber at a given frequency can be notably increased if it is located at a position of the primary system with an in-phase or out-of- phase motion of the attachment points according to the rotational-mode characteristics of the 3-DOF DVA at this frequency.

scholarly journals Development of a Compound Speckle Interferometer for Precision Three-Degree-of-Freedom Displacement Measurement

Sensors ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 1828
Author(s):  
Hung-Lin Hsieh ◽  
Bo-Yen Sun
Keyword(s):  
Speckle Interferometry ◽  
Degree Of Freedom ◽  
Heterodyne Interferometry ◽  
Beam Splitting ◽  
Speckle Interferometer ◽  
Real World Applications ◽  
Three Degree Of Freedom ◽  
Contact Displacement ◽  
Displacement Measurements ◽  
Measurement Capabilities

In this study, a compound speckle interferometer for measuring three-degree-of-freedom (3-DOF) displacement is proposed. The system, which combines heterodyne interferometry, speckle interferometry and beam splitting techniques, can perform precision 3-DOF displacement measurements, while still having the advantages of high resolution and a relatively simple configuration. The incorporation of speckle interferometry allows for non-contact displacement measurements by detecting the phase of the speckle interference pattern formed from the convergence of laser beams on the measured rough surface. Experiments were conducted to verify the measurement capabilities of the system, and the results show that the proposed system has excellent measurement capabilities suitable for future real-world applications.

scholarly journals Analytical Investigation on Torque of Three-Degree-of-Freedom Electromagnetic Actuator for Image Stabilization

2021 ◽  
Vol 11 (15) ◽  
pp. 6872
Author(s):  
Chien-Sheng Liu ◽  
Yi-Hsuan Lin ◽  
Chiu-Nung Yeh
Keyword(s):  
Power Efficiency ◽  
Rotation Angle ◽  
Analytical Investigation ◽  
Degree Of Freedom ◽  
Electromagnetic Actuator ◽  
3D Fem ◽  
Image Stabilization ◽  
Large Rotation ◽  
Spherical Motor ◽  
Three Degree Of Freedom

In keeping with consumers’ preferences for electromagnetic motors of ever smaller power consumption, it is necessary to improve the power efficiency of the electromagnetic motors used in unmanned aerial vehicles and robots without sacrificing their performance. Three-degree-of-freedom (3-DOF) spherical motors have been developed for these applications. Accordingly, this study modifies the 3-DOF spherical motor proposed by Hirata’s group in a previous study (Heya, A.; Hirata, K.; Niguchi, N., Dynamic modeling and control of three-degree-of-freedom electromagnetic actuator for image stabilization, IEEE Transactions on Magnetics 2018, 54, 8207905.) to accomplish a 3-DOF spherical motor for camera module with higher torque output in the large rotation angle. The main contribution of this study is to improve the static torque in the X- and Y-axes with an improved electromagnetic structure and a particular controlling strategy. In the structural design, eight symmetrical coils with specific coil combination are used instead of conventional four symmetrical coils. In this study, the development of the proposed 3-DOF spherical motor was constructed and verified by using a 3D finite-element method (3D FEM). The simulation results show that the proposed 3-DOF spherical motor has higher torque output in the large rotation angle when compared to the original 3-DOF spherical motor.

Three-Degree-of-Freedom Parallel Robot Arm

2006 ◽  
Author(s):  
Martin Hosek ◽  
Michael Valasek ◽  
Jairo Moura
Keyword(s):  
Parallel Robot ◽  
Degree Of Freedom ◽  
Motion Path ◽  
Angular Orientation ◽  
Robot Arm ◽  
Flat Panel Display ◽  
End Effector ◽  
Cluster Tools ◽  
Manufacturing Applications ◽  
Three Degree Of Freedom

This paper presents single- and dual-end-effector configurations of a planar three-degree of freedom parallel robot arm designed for automated pick-place operations in vacuum cluster tools for semiconductor and flat-panel-display manufacturing applications. The basic single end-effector configuration of the arm consists of a pivoting base platform, two elbow platforms and a wrist platform, which are connected through two symmetric pairs of parallelogram mechanisms. The wrist platform carries an end-effector, the position and angular orientation of which can be controlled independently by three motors located at the base of the robot. The joints and links of the mechanism are arranged in a unique geometric configuration which provides a sufficient range of motion for typical vacuum cluster tools. The geometric properties of the mechanism are further optimized for a given motion path of the robot. In addition to the basic symmetric single end-effector configuration, an asymmetric costeffective version of the mechanism is derived, and two dual-end-effector alternatives for improved throughput performance are described. In contrast to prior attempts to control angular orientation of the end-effector(s) of the conventional arms employed currently in vacuum cluster tools, all of the motors that drive the arm can be located at the stationary base of the robot with no need for joint actuators carried by the arm or complicated belt arrangements running through the arm. As a result, the motors do not contribute to the mass and inertia properties of the moving parts of the arm, no power and signal wires through the arm are necessary, the reliability and maintenance aspects of operation are improved, and the level of undesirable particle generation is reduced. This is particularly beneficial for high-throughput applications in vacuum and particlesensitive environments.

Kinematics of a New High-Precision Three-Degree-of-Freedom Parallel Manipulator

2006 ◽  
Vol 129 (3) ◽  
pp. 320-325 ◽  
Author(s):  
Farhad Tahmasebi
Keyword(s):  
Power Dissipation ◽  
Inverse Kinematics ◽  
Parallel Manipulator ◽  
Degree Of Freedom ◽  
Base Plane ◽  
Degree Polynomial ◽  
Payload Capacity ◽  
Half Angle ◽  
Three Degree Of Freedom ◽  
Direct Kinematics

Closed-form direct and inverse kinematics of a new three-degree-of-freedom (DOF) parallel manipulator with inextensible limbs and base-mounted actuators are presented. The manipulator has higher resolution and precision than the existing three-DOF mechanisms with extensible limbs. Since all of the manipulator actuators are base mounted, higher payload capacity, smaller actuator sizes, and lower power dissipation can be obtained. The manipulator is suitable for alignment applications where only tip, tilt, and piston motions are significant. The direct kinematics of the manipulator is reduced to solving an eighth-degree polynomial in the square of the tangent of the half-angle between one of the limbs and the base plane. Hence, there are at most 16 assembly configurations for the manipulator. In addition, it is shown that the 16 solutions are eight pairs of reflected configurations with respect to the base plane. Numerical examples for the direct and inverse kinematics of the manipulator are also presented.

Sign in / Sign up

Export Citation Format

Share Document