Showing papers on "Dynamic Vibration Absorber published in 1995"

Dynamics of Structures: Theory and Applications to Earthquake Engineering

Abstract: I. SINGLE-DEGREE-OF-FREEDOM SYSTEMS. 1. Equations of Motion, Problem Statement, and Solution Methods. Simple Structures. Single-Degree-of-Freedom System. Force-Displacement Relation. Damping Force. Equation of Motion: External Force. Mass-Spring-Damper System. Equation of Motion: Earthquake Excitation. Problem Statement and Element Forces. Combining Static and Dynamic Responses. Methods of Solution of the Differential Equation. Study of SDF Systems: Organization. Appendix 1: Stiffness Coefficients for a Flexural Element. 2. Free Vibration. Undamped Free Vibration. Viscously Damped Free Vibration. Energy in Free Vibration. Coulomb-Damped Free Vibration. 3. Response to Harmonic and Periodic Excitations. Viscously Damped Systems: Basic Results. Harmonic Vibration of Undamped Systems. Harmonic Vibration with Viscous Damping. Viscously Damped Systems: Applications. Response to Vibration Generator. Natural Frequency and Damping from Harmonic Tests. Force Transmission and Vibration Isolation. Response to Ground Motion and Vibration Isolation. Vibration-Measuring Instruments. Energy Dissipated in Viscous Damping. Equivalent Viscous Damping. Systems with Nonviscous Damping. Harmonic Vibration with Rate-Independent Damping. Harmonic Vibration with Coulomb Friction. Response to Periodic Excitation. Fourier Series Representation. Response to Periodic Force. Appendix 3: Four-Way Logarithmic Graph Paper. 4. Response to Arbitrary, Step, and Pulse Excitations.Response to Arbitrarily Time-Varying Forces. Response to Unit Impulse. Response to Arbitrary Force. Response to Step and Ramp Forces. Step Force. Ramp or Linearly Increasing Force. Step Force with Finite Rise Time. Response to Pulse Excitations. Solution Methods. Rectangular Pulse Force. Half-Cycle Sine Pulse Force. Symmetrical Triangular Pulse Force. Effects of Pulse Shape and Approximate Analysis for Short Pulses. Effects of Viscous Damping. Response to Ground Motion. 5. Numerical Evaluation of Dynamic Response. Time-Stepping Methods. Methods Based on Interpolation of Excitation. Central Difference Method. Newmark's Method. Stability and Computational Error. Analysis of Nonlinear Response: Central Difference Method. Analysis of Nonlinear Response: Newmark's Method. 6. Earthquake Response of Linear Systems. Earthquake Excitation. Equation of Motion. Response Quantities. Response History. Response Spectrum Concept. Deformation, Pseudo-Velocity, and Pseudo-Acceleration Response Spectra. Peak Structural Response from the Response Spectrum. Response Spectrum Characteristics. Elastic Design Spectrum. Comparison of Design ad Response Spectra. Distinction between Design and Response Spectra. Velocity and Acceleration Response Spectra. Appendix 6: El Centro, 1940 Ground Motion. 7. Earthquake Response of Inelastic Systems. Force-Deformation Relations. Normalized Yield Strength, Yield Strength Reduction Factor, and Ductility Factor. Equation of Motion and Controlling Parameters. Effects of Yielding. Response Spectrum for Yield Deformation and Yield Strength. Yield Strength and Deformation from the Response Spectrum. Yield Strength-Ductility Relation. Relative Effects of Yielding and Damping. Dissipated Energy. Energy Dissipation Devices. Inelastic Design Spectrum. Applications of the Design Spectrum. Comparison of Design and Response Spectra. 8. Generalized Single-Degree-of-Freedom Systems. Generalized SDF Systems. Rigid-Body Assemblages. Systems with Distributed Mass and Elasticity. Lumped-Mass System: Shear Building. Natural Vibration Frequency by Rayleigh's Method. Selection of Shape Function. Appendix 8: Inertia Forces for Rigid Bodies. II. MULTI-DEGREE-OF-FREEDOM SYSTEMS. 9. Equations of Motion, Problem Statement, and Solution Methods. Simple System: Two-Story Shear Building. General Approach for Linear Systems. Static Condensation. Planar or Symmetric-Plan Systems: Ground Motion. Unsymmetric-Plan Building: Ground Motion. Symmetric-Plan Buildings: Torsional Excitation. Multiple Support Excitation. Inelastic Systems. Problem Statement. Element Forces. Methods for Solving the Equations of Motion: Overview. 10. Free Vibration. Natural Vibration Frequencies and Modes. Systems without Damping. Natural Vibration Frequencies and Modes. Modal and Spectral Matrices. Orthogonality of Modes. Interpretation of Modal Orthogonality. Normalization of Modes. Modal Expansion of Displacements. Free Vibration Response. Solution of Free Vibration Equations: Undamped Systems. Free Vibration of Systems with Damping. Solution of Free Vibration Equations: Classically Damped Systems. Computation of Vibration Properties. Solution Methods for the Eigenvalue Problem. Rayleigh's Quotient. Inverse Vector Iteration Method. Vector Iteration with Shifts: Preferred Procedure. Transformation of kA A = ...w2mA A to the Standard Form. 11. Damping in Structures.Experimental Data and Recommended Modal Damping Ratios. Vibration Properties of Millikan Library Building. Estimating Modal Damping Ratios. Construction of Damping Matrix. Damping Matrix. Classical Damping Matrix. Nonclassical Damping Matrix. 12. Dynamic Analysis and Response of Linear Systems.Two-Degree-of-Freedom Systems. Analysis of Two-DOF Systems without Damping. Vibration Absorber or Tuned Mass Damper. Modal Analysis. Modal Equations for Undamped Systems. Modal Equations for Damped Systems. Displacement Response. Element Forces. Modal Analysis: Summary. Modal Response Contributions. Modal Expansion of Excitation Vector p (t) = s p(T). Modal Analysis for p (t) = s p(T). Modal Contribution Factors. Modal Responses and Required Number of Modes. Special Analysis Procedures. Static Correction Method. Mode Acceleration Superposition Method. Analysis of Nonclassically Damped Systems. 13. Earthquake Analysis of Linear Systems.Response History Analysis. Modal Analysis. Multistory Buildings with Symmetric Plan. Multistory Buildings with Unsymmetric Plan. Torsional Response of Symmetric-Plan Buildings. Response Analysis for Multiple Support Excitation. Structural Idealization and Earthquake Response. Response Spectrum Analysis. Peak Response from Earthquake Response Spectrum. Multistory Buildings with Symmetric Plan. Multistory Buildings with Unsymmetric Plan. 14. Reduction of Degrees of Freedom. Kinematic Constraints. Mass Lumping in Selected DOFs. Rayleigh-Ritz Method. Selection of Ritz Vectors. Dynamic Analysis Using Ritz Vectors. 15. Numerical Evaluation of Dynamic Response. Time-Stepping Methods. Analysis of Linear Systems with Nonclassical Damping. Analysis of Nonlinear Systems. 16. Systems with Distributed Mass and Elasticity. Equation of Undamped Motion: Applied Forces. Equation of Undamped Motion: Support Excitation. Natural Vibration Frequencies and Modes. Modal Orthogonality. Modal Analysis of Forced Dynamic Response. Earthquake Response History Analysis. Earthquake Response Spectrum Analysis. Difficulty in Analyzing Practical Systems. 17. Introduction to the Finite Element Method.Rayleigh-Ritz Method. Formulation Using Conservation of Energy. Formulation Using Virtual Work. Disadvantages of Rayleigh-Ritz Method. Finite Element Method. Finite Element Approximation. Analysis Procedure. Element Degrees of Freedom and Interpolation Function. Element Stiffness Matrix. Element Mass Matrix. Element (Applied) Force Vector. Comparison of Finite Element and Exact Solutions. Dynamic Analysis of Structural Continua. III. EARTHQUAKE RESPONSE AND DESIGN OF MULTISTORY BUILDINGS. 18. Earthquake Response of Linearly Elastic Buildings. Systems Analyzed, Design Spectrum, and Response Quantities. Influence of T 1 and r on Response. Modal Contribution Factors. Influence of T 1 on Higher-Mode Response. Influence of r on Higher-Mode Response. Heightwise Variation of Higher-Mode Response. How Many Modes to Include. 19. Earthquake Response of Inelastic Buildings. Allowable Ductility and Ductility Demand. Buildings with "Weak" or "Soft" First Story. Buildings Designed for Code Force Distribution. Limited Scope. Appendix 19: Properties of Multistory Buildings. 20. Earthquake Dynamics of Base-Isolated Buildings. Isolation Systems. Base-Isolated One-Story Buildings. Effectiveness of Base Isolation. Base-Isolated Multistory Buildings. Applications of Base Isolation. 21. Structural Dynamics in Building Codes. Building Codes and Structural Dynamics. International Building Code (United States), 2000. National Building Code of Canada, 1995. Mexico Federal District Code, 1993. Eurocode 8. Structural Dynamics in Building Codes. Evaluation of Building Codes. Base Shear. Story Shears and Equivalent Static Forces. Overturning Moments. Concluding Remarks. Appendix A: Frequency Domain Method of Response Analysis.Appendix B: Notation.Appendix C: Answers to Selected Problems.Index.

Adaptive-passive vibration control system

Abstract: A passive-adaptive vibration control system is provided wherein various elements of the system may be adapted on-line in response to sensed vibrations. A spring/weight vibration absorber (160, 165) is attached to a vibrating body, such as the drum (115) of a laundry machine (100), to absorb energy generated by the drum, to minimize the transmission of vibrations to a structure, such as the body of the machine (100) in mechanical communication with the drum. The mass of the weight (160) of the vibration absorber may be adjusted, on-line, to compensate for sensed vibrations. A vibration sensor (170) is connected to the vibrating body so as to sense the level of vibration above a desired level and to send a signal representative of that vibration to an electronic controller (180). The electronic controller (180) is designed to instruct an actuator arrangement (182, 184) to adapt the mass of the weight to compensate for the sensed vibration. For example, the weight (160) may be a chamber, the mass of which may be adjusted by adding or releasing a fluid to or from the chamber via the actuator arrangement (182,184) under the control of the controller (180).

Tunable Active Vibration Absorber: The Delayed Resonator

Abstract: This paper elaborates upon a novel concept, the Delayed Resonator, a tunable active vibration absorber. This technique uses a control which has a time delayed feedback of the absorber mass displacement. The substance of this process is in that the absorber completely removes oscillations from the primary structure. Two very strong features that should be mentioned are : (a) the excitation frequency range can vary over a semi-infinite interval, and (b) the absorber can be tuned in real time. These are the unique characteristics of the technique distinguishing it from the others. Stability issues of the primary system combined with the Delayed Resonator are addressed following Nyquist and root locus methods. In particular, the absorption performance for cases with time varying excitation frequency is studied. The primary focus of this paper is on the analysis of transient absorption behavior of the Delayed Resonator during its tuning. An example case is provided which considers a step change in the excitation frequency. A well-pronounced manifestation of the tunability feature of the Delayed Resonator is observed. The superiority of the Delayed Resonator absorber over the conventional a priori tuned absorbers is also demonstrated.

Active systems and devices including active vibration absorbers (AVAS)

Abstract: A flexibly-mounted active vibration absorber (AVA) which has a secondary controllable mass M3. If the passive resonance of mass M2 of the tuned absorber is insufficient to control the input vibration, a secondary mass M3 is vibrated at a frequency, amplitude and phase sufficient to make up the deficiency in mass M2. Many embodiments are described which depict variations on the first spring used for flexibly mounting the AVA, the actuators used to drive the AVA, and the attachment features for attaching to a vibrating member. Further, in another aspect, means for counterbalancing the moments produced by the AVA are described.

Silica-containing vibration damper and method

Abstract: A method for vibrationally damping an article that is subject to resonant vibrations comprises the steps of providing a vibration damper and applying the vibration damper to the article to damp the resonant vibrations. The vibration damper comprises an acrylate viscoelastic vibration damping material and an effective amount of hydrophobic silica. The invention also relates to vibration dampers that utilize the acrylate viscoelastic vibration damping material as well as articles that incorporate the vibration dampers.

Vibration isolation system including a passive tuned vibration absorber

Abstract: An isolation system (20) including the combination of an elastomeric mount (25) for attachment between a structure (24) and a vibrating member (22) and further including at least one passive tuned vibration absorber (TVA) (32) attached in the proximity the elastomeric mount (25) but on the structure side thereof. The resonant frequency f r of the passive TVA (32) is tuned to a resonant frequency f r just below the predominant operating frequency f o of the vibrating member (22), such that the resonance of the tuned vibration absorber (32) makes the structure (24) appear dynamically stiffer. In particular the ratio of f r /f o is in the range of between about 0.90 and 0.90. In one embodiment, the passive TVA (32) attaches directly to the inner member (28) of the elastomeric mount (25) and clamps the TVA assembly (43) to the structure (24) and clamps the structure (24) to the elastomeric mount (25). In another embodiment, the passive TVA (32) is clamped to the structure (24) at a point where it cooperates with the elastomeric mount (25) to reduce transmitted vibration, preferably the TVA (32) is attached at a point within last 20% of the end of the beam-like structure (24).

Inertial piezoceramic actuators for smart structures

Abstract: An inertial actuator, also known as a proof mass actuator (PMA), applies structural forces by reacting against an inertial mass. This paper introduces a class of recently developed piezoceramic PMA and its application to reduce vibration and structure-borne noise. The design incorporates displacement amplification to efficiently achieve low resonant frequency. A method is presented for assessing the efficiency of a piezoceramic PMA and comparing the power density of competing PMA technologies (ie, voice-coil vs. piezoceramic vs. magnetostrictive). The performance of the PMA is demonstrated by measuring the force generated against an infinite impedance and measurements on a structure representative of a turbo-prop fuselage. The experimental testing demonstrates the validity of a simple vibration absorber model in understanding PMA performance on complex structures.

Vibration control of plates by plate-type dynamic vibration absorbers

Abstract: In this paper, a new plate-type dynamic vibration absorber is presented for controlling the several predominant modes of vibration of plate (mainplate) under harmonic excitation, which consists of a plate (dynamic absorbing plate) under the same boundary condition as the main plate and with uniformly distributed connecting springs and dampers between the main and dynamic absorbing plates. Equations of motion of the system in the modal coordinates of the main plate become equal to those of the two-degrees-of-freedom system with two masses and three springs. Formulas for optimum design of the plate-type dynamic vibration absorber are presented using the optimum tuning method of a dynamic absorber in two-degrees-of-freedom system, obtained by the Den Hartog method. Moreover, for practical problems regarding large-scale plates, an approximate tuning method of the plate-type dynamic absorbers with several sets of concentrated connecting springs and dampers is also presented. The numerical calculations demonstrate the effectiveness of the plate-type dynamic absorbers.

Design Considerations for Delayed-Resonator Vibration Absorbers

Abstract: This paper elaborates on a novel concept, the delayed resonator, as a tunable active vibration absorber with an emphasis on the design features. This technique uses a control that has a time-delayed feedback of the absorber mass displacement. The substance of this process is in that the absorber completely removes oscillations from the harmonically excited primary structure. Seminal features of this method are the excitation frequency range can vary over a \Isemi-infinite interval\N, and the absorber can be \Ituned in real time\N. These characteristics uniquely distinguish it from the other techniques. Stability issues of the primary system combined with the delayed resonator are addressed following Nyquist and root locus methods. In particular, the absorption performance for cases with time-varying excitation frequency is studied. An analysis of transient absorption behavior of the delayed resonator during the tuning phase is presented. An example case is taken that considers a step change in the excitation frequency. The superiority of the delayed-resonator absorber over the conventional a priori tuned absorbers is also demonstrated. The highlight of the paper is at the design aspect of this novel absorber. A selection template is proposed for the designer to achieve a desirable frequency-tuning property for the absorption. A set of simulation verifications is included in the text.

Vibration control of a ropeway carrier by passive dynamic vibration absorbers

Abstract: Swing of a ropeway carrier is easily caused by wind and it is very difficult to reduce. In this paper, several types of dynamic vibration absorbers for a ropeway carrier are analyzed theoretically, and a general theory is formulated. A method of optimum tuning is obtained and the index (equivalent mass ratio) which indicates the effect of the absorber is defined. When the dynamic vibration absorber is located at the center of oscillation, swing is not reduced at all. The center of oscillation is the point that is located at the distance of equivalent length of the pendulum from the center of suspension (fulcrum). The absorber should be located as far as possible from the center of oscillation.

Hand operated impact implement having tuned vibration absorber

Abstract: A hand operated impact implement having a tuned vibration absorber includes a head for impacting an object, a handle connected to the head, and a tuned vibration damper attached to the handle and/or head to damp overall handle/head vibration of the impact implement after impacting an object.

Optimal Active Vibration Absorber: Design and Experimental Results

Abstract: An optimal active vibration absorber can provide guaranteed closed-loop stability and control for large flexible space structures with collocated sensors/actuators. The active vibration absorber is a second-order dynamic system which is designed to suppress any unwanted structural vibration. This can be designed with minimum knowledge of the controlled system. Two methods for optimizing the active vibration absorber parameters are illustrated: minimum resonant amplitude and frequency matched active controllers. The Controls-Structures Interaction Phase-1 Evolutionary Model at NASA LaRC is used to demonstrate the effectiveness of the active vibration absorber for vibration suppression. Performance is compared numerically and experimentally using acceleration feedback.

Feedback enhanced adaptively tuned vibration absorber

Abstract: An apparatus has a mass suspended between two mounting plates by a separate springs to form a resonant structure that absorbs vibration in a structural member to which the mounting plates are attached. Permanent magnets are fixed to opposite sides of the mass. A sensor produces a signal indicating the frequency of the vibration. A feedback circuit receives the signal from the sensor and produces an output signal having first component frequency which corresponds to a harmonic of the frequency of the vibration. The output signal is applied to a separate voice coil adjacent to each permanent magnet. The magnetic fields produced by the output signal flowing through the voice coils interact with the magnetic fields from the permanent magnets to generate forces that act on the mass in a manner that increases the impedance of the absorber to the vibration in the structural member.

Free-wheel absorber

Abstract: The invention relates to a system for damping torsional vibrations which are initiated by a crankshaft of an internal combustion engine, consisting of an absorber mass arranged on the crankshaft end in such a way as to be movable to a limited extent. According to the invention the vibration damping is distinguished by a free-wheel absorber (1) in which an absorber mass (11) is combined with a drive member and this unit is guided via a free-wheel unit (8) on the hub (3). This results in effective damping of torsional vibrations over a large speed range of the internal combustion engine.

Tuned dynamic vibration absorber

Abstract: A vibration absorber is provided for reducing noise and vibration emanating from an electric motor, or another vibrating object, and the surrounding structure to which it is mounted. The vibration absorber has a beam with a mass secured thereto. The vibration absorber is mounted externally to the motor, in a direction perpendicular to an axis of torsional vibration of the motor. The absorber is tuned to have a resonant frequency corresponding to the torsional vibrational frequency of the motor.

Adaptively tuned vibration absorber

Abstract: An apparatus for absorbing vibrations in a structural member, such as in an aircraft fuselage, has first and second plates for attaching to the structural member. A mass, which is suspended between the plates, includes a first block connected to the first plate by a first spring and a second block connected to the second plate by a second spring. The springs may be formed by metal straps which allow the mass to move along one axis or by rods which allow two axis movement of the mass. One sensor produces a signal indicating vibration of the structural member and another sensor produces a signal indicating vibration of the mass. A mechanism connected to the first and second block responds to a control signal by varying a distance between the first and second block to alter stiffness of the first and second springs. A control circuit receives the signals from the sensors and produces the control signal which causes the mechanism to alter the spring stiffness so that the spring and the mass resonate to absorb vibration of the structural member.

Experimental comparison of piezoelectric and constrained-layer damping

Abstract: A qualitative comparison between a piezoelectric vibration absorber and a constrained layer damping treatment is presented. Piezoelectric materials convert mechanical strains into electrical charge. Dissipation of the charge results in attenuation of vibration. The damping is concentrated to a single mode by constructing a piezoelectric absorber. The damped vibration absorber is comprised of the piezoelectric material and a passive electronic shunt. Previous research has applied the piezoelectric absorber to one-dimensional structures. This paper applies the absorber to a two-dimensional planar problem. The simple mathematical description of the absorber is modified for the two-dimensional problem. An analytical means of estimating the effectiveness of the piezoelectric absorber is derived. The effectiveness is estimated for an electronics chassis box subjected to random excitation. A typical constrained layer damping treatment is also analytically designed for the problem. The piezoelectric absorber and the constrained layer damping treatment are experimentally applied to identical boxes. Results show that the piezoelectric absorber can provide vibration suppression comparable to that obtained by the constrained layer damping treatment.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Active vibration control via electromagnetic dynamic absorbers

Abstract: An actively controlled electromagnetic absorber is considered for reducing the chatter in a boring bar. The absorber is suspended inside the free end of the boring bar and consists of a mass with four poles, each pole having a coil attached to it. In the present study, the magnetic force, which is inherently a nonlinear function of current and air gap, is approximated using linearized model. The dynamic characteristic of the boring bar is modeled using Timoshenko beam finite elements, while a lump parameter model is used for the absorber. Two approaches are used in the controller design. The first approach uses full state feedback with quadratic performance index. The second approach uses direct output feedback based on the results of the first approach. The effects of residual modes and spillover on the performance of the overall system are discussed for the two approaches. Simulation results show that a significant increase on the boring bar damping ratio can be achieved by using the proposed electromagnetic absorber.

Modeling and characterization of a piezoceramic inertial actuator

Abstract: An inertial actuator (also known as a proof mass actuator) applies forces to a structure by reacting them against an "external" mass. This approach to actuation may provide some practical benefits in the active control of vibration and structure-borne noise: system reliability may be improved by removing the actuator from a structural load path; effective discrete point-force actuation permits ready attachment to curved surfaces, and an inherent passive vibration absorber effect can reduce power requirements. This paper describes a class of recently developed inertial actuators that is based on mechanical amplification of displacements of an active piezoceramic element. Important actuator characteristics include resonant frequencies, clamped force, and the drive voltage to output force frequency response function. The paper addresses one particular approach to motion amplification. the "dual unimorph," in detail. A model of actuator dynamic behavior is developed using an assumed modes method, treating the piezoelectrically-induced stresses as external forces. Predicted actuator characteristics agree well with experimental data obtained for a prototype actuator. The validated actuator dynamic model provides a tool for design improvement. Introduction Active control technology has potential applications to many noise and vibration problems, including aircraft cabin interior noise, spacecraft vibration suppression, and automobile, industrial machinery and home appliances [I-51. Practical deployment of this technology requires, among other things, the development of light, efficient, reliable. cost-effective actuators. Moving coil electrodynamic devices are inherently capable of large displacements and have been widely used as the basis for inertial actuators [6-81. Initial research by the authors had indicated the potential for piezoceramic inertial actuators to provide higher power density, better linearity and decreased power consumption, especially for moderately high frequency (100 to 10,000 Hz) applications [9]. The purpose of the research described herein was to explore the potential performance of piezoceramic inertial actuators in more detail. Both analytical and experimental aspects were addressed. Piezoceramic Inertial Actuator Conceuts Piezoelectric materials have found wide use in inertial sensor (e.g., accelerometer) applications because of high electromechanical transduction properties. These properties also make such materials excellent candidates for use in actuators. The need for rapid, highforce linear response effectively limits the materials Associate Professor of Aerospace Engineering, choice to piezoceramics [lo]. Senior Member AIAA Senior Engineer, Member AIAA Graduate Student, Student Member AIAA Professor of Mechanical Engineering An inertial actuator can be thought of as applying forces to a structure that are reacted by accelerating a supported mass. Even though piezoceramic materials . Copyright O 1995 by PCB Piezotronics. Inc. Published by are capable of providing high forces. there has been the American Institute of Aeronautics and Astronautics, little prior development of inertial actuators using them. Inc. with permission. largely because of the small strains (displacements) 3 4 4 0 American Institute of Aeronautics and Astronautics developed and high inherent stiffness. Both of these factors limit the practical performance achievable using direct piezoelectric acceleration of a given mass in the frequency range of interest. The development and use of mechanical amplification methods is essential to the practical success of piezoceramic inertial actuation. Several approaches to mechanical amplification [c.f., 1 1-15] were explored in this research. Figure 1 shows schematically three of the general concepts considered. For purposes of discussion, these may be considered to be either planar or axisymmetric.

Single mass dual frequency fixed delayed resonator (DFFDR)

Abstract: A novel concept, the delayed resonator (DR), as a tunable active vibration absorber has been introduced by the authors' group at the University of Connecticut. This unique technique uses a very simple control which has only a time delayed feedback of the absorber mass displacement. The absorber can completely remove oscillations from the primary structure when the primary is excited by a simple harmonic force. The work presented here treats a considerably more complex proposition dual frequency fixed delayed resonator (DFFDR). The device, DFFDR, is obtained by a similar delayed position feedback mechanism as in the case of DR, but this feedback imparts two (instead of one) distinct and fixed resonance frequencies. The interesting feature is in the simplicity of the control which can enforce two natural frequencies (and two corresponding natural modes), to a single mass, or single degree of freedom (SDOF) system.

Vibration absorber for vibration-endangered structural parts and structures

Abstract: The equipment is esp. for chimneys, masts, industrial tanks etc. with quasi-rotational-symmetrical-vibration characteristics. It comprises a liquid-filled tank whose weight, sloshing frequency and inherent damping characteristics are matched to the natural frequency of the building. The distance (A) from each enclosing wall (W) of the tank to the mid-point (M) of the surface of the liquid at the central perpendicular is approximately the same. The height to which the tank is filled can be less than the distance (A), and typically less than half of it. The tank may be square or can have a circular bottom (G), or it can be annular and divided by radial partitions.

H∞ control with pole assignment in a specified region for multi-degree-of-freedom structure using active dynamic vibration absorber

Abstract: In this study by applying H∞ control with pole assignment in a specified region a robust controller for an active dynamic vibration absorber is designed for the objective of vibration control of a multi-degree-of-freedom structure. In conventional H∞ control, the frequency weighting functions used in the criterion function have determined its vibration control performance and its stability robustness for a spillover phenomenon caused by model reduction. It is shown that this method of H∞ control with pole assignment in a specified region can yield a distinct design of a vibration control system, since poles of the closed-loop system are assigned to a specified region in the design procedure. We show the design procedures of continuous-time H∞ control with pole assignment and discrete-time H∞ control. By numerical calculations and experiments, it is shown that continuous-time H∞ control with pole assignment can suppress the observation spillover and assign the poles of the controlled modes to the left of the vertical line s = -β in the s-plane.

Vibration absorber with mount

Abstract: The vibration absorbers have mounts for radial fastening of the vibration absorber to an inside surface of a wheel rim to be used on rails. A plurality of mounts are uniformly distributed over the circumference of the inside surface and are each coupleable to the wheel rim in an acoustically good conducting manner against a surface that matches the radius of curvature of the inside surface. On each mount at least one vibration absorber consisting of a sequence, running in the radial direction, of metal and plastic plates can be coupled in an acoustically effective manner by means of a coupling surface. The vibration absorbers and mount are releasably connected with one another and have a coupling surface that is always the same and is independent of the radius of curvature of the inside surface of the wheel rim.

Stabilizing device for variable displacement axial piston pumps

Abstract: A piston for a variable displacement axial piston hydraulic pump has a vibration absorber disposed within a chamber of the piston. The vibration absorber includes a vibration absorber mass suspended between a pair of springs. The vibration absorber offsets the piston inertia created from the oscillatory displacement of the pistons for stabilizing the pump.

Balancing Machine Using Dynamic Vibration Absorber. Measurement with an Undamped Dynamic Vibration Absorber.

Abstract: A new type of balancing machine is proposed which uses a dynamic vibration absorber as a device measuring unbalance. When an unbalanced rotor rotates, centrifugal forces are generated which result in sinusoidal forces being transmitted to the supporting structure. An undamped dynamic vibration absorber is attached to the structure in the proposed machine. When it is tuned to resonate at the test rotational speed, the structure does not move at all ; the auxiliary system vibrates in such a way that the phase angle between the displacement of auxiliary mass and the sinusoidal force is exactly 180 degrees and that the product of the auxiliary mass and the amplitude of its vibration is equal to the amount of unbalance. Therefore, the motion of the auxiliary mass provides sufficient information for balancing the rotor. The principles and features of the proposed machine are investigated, and experiments are carried out using the developed apparatus. The results demonstrate the feasibility of the proposed balancing machine.

Electronic controller for an adaptively tuned vibration absorber

Abstract: An apparatus for absorbing vibrations in a structural member has a mass suspended between two mounting plates by a separate springs. The mass has two sections and a mechanism for adjusting the spacing between the sections to alter the spring stiffness. Two sensors produce first and second signals representing the vibration of the structural member and the mass. The mechanism is operated by a controller that includes separate filters for the first and second signals in which each filter has a center frequency that is tuned by a clock signal. The phase comparator produces a phase output signal indicating a phase relationship between signals from the two filters and the control signal for the mechanism is produce in response to the phase output signal. A phase locked loop produces the clock signal for tuning the filters in response to a comparison between one of the first and second signals and a signal from one of the filters.