Optimum parameters of a dynamic vibration absorber of non-traditional form have been derived for suppressing vibration of a single degree-of-freedom system due to ground motion. The reduction of transmission of motion from the support to... more
Optimum parameters of a dynamic vibration absorber of non-traditional form have been derived for suppressing vibration of a single degree-of-freedom system due to ground motion. The reduction of transmission of motion from the support to the mass of the structure is compared for the cases of using the traditional and the proposed dynamic absorbers. Under the optimum tuning condition of the absorbers, it is proved analytically that the proposed absorber provides a larger suppression of resonant vibration amplitude of the primary system excited by ground motion than the traditional absorber.
The present article proposes the closed-form solution for analytical prediction of stability lobes in internal turning process. The passively damped boring bar is modeled as a cantilevered Euler-Bernoulli beam with constant cross... more
The present article proposes the closed-form solution for analytical prediction of stability lobes in internal turning process. The passively damped boring bar is modeled as a cantilevered Euler-Bernoulli beam with constant cross sectional properties in which a Tuned Mass Damper (TMD) is embedded for the purpose of chatter suppression. The non-dimensional equations of motion are derived, assuming that the boring bar dynamics is well-represented by the fundamental mode of vibration. The stability of equivalent two-DOF dynamic model, i.e. boring bar with TMD, is analyzed in frequency domain. The closed-form expressions for critical depth of cut and spindle speed are presented in terms of boring bar and TMD characteristics. The proposed solution considers the effects of boring bar's structural damping and cutting geometry of insert on the stability behavior of passively damped cutting tool. An unconstrained optimization method is utilized to compute the most optimal set of tuning parameters for anti-chatter TMD. In order to improve the boundary of stability in a global sense, maximization of minimum critical depth of cut is selected as the objective of optimization. The superior performance of anti-chatter TMD is compared to H∞ and H2 TMDs for a wide range of applications. Moreover, the achieved results show a remarkable improvement of stability boundary compared to recent research works.
Mechanical systems with flexible dynamics often suffer from vibration induced by changes in the reference command or from external disturbances. The technique of adding a vibration absorber has proven useful at eliminating vibrations from... more
Mechanical systems with flexible dynamics often suffer from vibration induced by changes in the reference command or from external disturbances. The technique of adding a vibration absorber has proven useful at eliminating vibrations from external disturbances and rotational imbalances. In this paper, the application of a Dynamic Vibration Absorber for suppression of chatter vibrations in the boring manufacturing process is presented. The boring bar is modelled as a cantilever Euler–Bernoulli beam and the DVA is composed of a mass and a spring and elements. After formulation of the problem, the optimum specifications of the absorber such as spring stiffness, absorber mass and its position are determined. The analog-simulated block diagram of the system is developed and the effects of various excitations such as step, ramp, etc. on the absorbed system are simulated. In addition, chatter stability is analysed in dominant modes of boring bar.
Dynamic vibration absorbers are commonly designed and tuned to suppress vibrations of one vibration mode of a vibrating structure even it is a multi degree-of-freedom (MDOF) or continuous structure. Resonance at other vibration modes of... more
Dynamic vibration absorbers are commonly designed and tuned to suppress vibrations of one vibration mode of a vibrating structure even it is a multi degree-of-freedom (MDOF) or continuous structure. Resonance at other vibration modes of the structure may still occur if the exciting force has a wide frequency band. A subsystem approach is proposed for analysis of the added stiffness and damping of vibration absorbers to the primary structure to which they are attached. The transfer function between the counteracting force from the vibration absorber and the vibration amplitude can then be derived for the comparison of their counteracting forces to the primary system. The major advantage of using the proposed method is that different designs of vibration absorber can be analysed separately from the primary system and therefore the dynamics characteristics of different designs of vibration absorber can be compared efficiently.
Parkinson's patients suffer from severe tremor due to an abnormality in their central oscillator. Medications used to decrease involuntary antagonistic muscles contraction can threaten their life. However, mechanical vibration absorbers... more
Parkinson's patients suffer from severe tremor due to an abnormality in their central oscillator. Medications used to decrease involuntary antagonistic muscles contraction can threaten their life. However, mechanical vibration absorbers can be used as an alternative treatment. The objective of this study is to provide a dynamic modeling of the human hand that describes the biodynamic response of Parkinson's patients and to design an effective tuned vibration absorber able to suppress their pathological tremor. The hand is modeled as a three degrees-of-freedom (DOF) system describing the flexion motion at the proximal joints on the horizontal plane. Resting tremor is modeled as dual harmonic excitation due to shoulder and elbow muscle activation operating at resonance frequencies. The performance of the single dynamic vibration absorber (DVA) is studied when attached to the forearm and compared with the dual DVA tuned at both excitation frequencies. Equations of motion are derived and solved using the complex transfer function of the non-Lagrangian system. The absorber's systems are designed as a stainless steel alloy cantilevered beam with an attached copper mass. The dual DVA was the most efficient absorber which reduces
A non-traditional dynamic vibration absorber is proposed for the minimization of maximum vibration velocity response of a vibrating structure. Unlike the traditional damped absorber configuration, the proposed absorber has a linear... more
A non-traditional dynamic vibration absorber is proposed for the minimization of maximum vibration velocity response of a vibrating structure. Unlike the traditional damped absorber configuration, the proposed absorber has a linear viscous damper connecting the absorber mass directly to the ground instead of the main mass. Optimum parameters of the proposed absorber are derived based on the fixed-point theory for minimizing the maximum vibration velocity response of a single-degree-of-freedom system under harmonic excitation. The extent of reduction in maximum vibration velocity response of the primary system when using the traditional dynamic absorber is compared with that using the proposed one. Under the optimum tuning condition of the absorbers, it is proved analytically that the proposed absorber provides a greater reduction in maximum vibration velocity response of the primary system than the traditional absorber.
In this article, the Hinf optimization design of a hybrid vibration absorber (HVA), including both passive and active elements, for the minimization of the resonant vibration amplitude of a single degree-of-freedom (sdof) vibrating... more
In this article, the Hinf optimization design of a hybrid vibration absorber (HVA), including both passive and active elements, for the minimization of the resonant vibration amplitude of a single degree-of-freedom (sdof) vibrating structure is derived by using the fixed-points theory. The optimum tuning parameters are the feedback gain, the tuning frequency, damping and mass ratios of the absorber. The effects of these parameters on the vibration reduction of the primary structure are revealed based on the analytical model. Design parameters of both passive and active elements of the HVA are optimized for the minimization of the resonant vibration amplitude of the primary system. One of the inherent limitations of the traditional passive vibration absorber is that its vibration absorption is low if the mass ratio between the absorber mass and the mass of the primary structure is low. The proposed HVA overcomes this limitation and provides very good vibration reduction performance even at a low mass ratio. The proposed optimized HVA is compared to a recently published HVA designed for similar propose and it shows that the present design requires less energy for the active element of the HVA than the compared design.
The optimal design parameters of a Dynamic vibration absorber (DVA) in a vibrating bar were discussed in this paper. It has been controlled passively by a Dynamic vibration absorber which consists of a mass and two springs in parallel. A... more
The optimal design parameters of a Dynamic vibration absorber (DVA) in a vibrating bar were discussed in this paper. It has been controlled passively by a Dynamic vibration absorber which consists of a mass and two springs in parallel. A bar, which is fixed at the left end and free at the right end is subjected to a harmonically excited force being positioned at the free end. To define the motion of a bar with a DVA, the equation of motion for a bar was derived by using a method of variation of parameters. To define the optimal design conditions of a DVA, the reduction of a vibrational intensity which is known as the time averaged power flow was evaluated and discussed. The possibility of reduction of the vibrational intensity was found to depend on the mass of a DVA, the positions, and the stiffness of two combined springs. Keywords— Passive control; a method of variation of parameters; the force transmissibility; a Dynamic Vibration Absorber (DVA); spring stiffness; I. INTRODUCTION In the industrial fields, lots of machines and structures had been troubled by vibration and unbalance. Numerous attempts have been made to control the vibrations of the machines in operation in the past decades. Hence the fast and the accurate motions of the machine are known to be the optimal design parameters. In the high speed operation, the vibration which may occurs at each parts of machine should be controlled actively or passively for the stability of the machine structure. The vibration problems of machines and structures had been studied by lots of researchers. The vibration energy flow and the dynamic response of a beam, plate, shell or some compound system have been analyzed. By using a model of an elastic beam, the vibrational intensity and control skills had been presented [1]-[3]. Furthermore, the complex frame which is the assembly of several beams and plates had been used to analyze and control the vibration characteristics [4]-[5]. The Active control method had been proven to become the convenient control method for the known forcing frequency zone [6]-[8]. The passive control of the vibrations of the machine tools had been introduced [9]-[12].
Hinf and H2 optimization problems with respect to a dynamic vibration absorber (DVA) in a single degree-of-freedom (sdof) system are classical optimization problems and solutions to them were found about half a century ago. Numerical... more
Hinf and H2 optimization problems with respect to a dynamic vibration absorber (DVA) in a single degree-of-freedom (sdof) system are classical optimization problems and solutions to them were found about half a century ago. Numerical solutions to the Hinf and H2 optimization problems with respect to DVA for a multi-degree-of-freedom (mdof) or continuous system can be found in the literature but their analytical solutions have not yet been found. In this article, we report the derivation of an analytical solution to the Hinf and H2 optimization problems of DVA applied to suppress random vibrations in plate structures. Analytical formulae are also proposed to express the optimal tuning frequency and damping ratios of the absorber. The established theory improves our understanding of the effects of different parameters including the mass, damping and tuning ratios and also the point of attachment of the absorber on the vibration absorption by the absorber. Numerical results show the usefulness of the optimization solutions in comparison to solutions suggested by other researchers based on other approaches to the problem.
The H2 optimum parameters of a dynamic vibration absorber of non-traditional form are derived to minimize the total vibration energy or the mean square motion of a single degree-of-freedom (sdof) system under random force excitations. The... more
The H2 optimum parameters of a dynamic vibration absorber of non-traditional form are derived to minimize the total vibration energy or the mean square motion of a single degree-of-freedom (sdof) system under random force excitations. The reduction of the mean square motion of the primary structure using the traditional vibration absorber is compared with the proposed dynamic absorber. Under optimum tuning condition, it is shown that the proposed absorber when compared with the traditional absorber, provides a larger suppression of the mean square vibrational motion of the primary system.
The H N optimum parameters of a dynamic vibration absorber (DVA) with ground-support are derived to minimize the resonant vibration amplitude of a single degree-of-freedom (sdof) system under harmonic force excitation. The optimum... more
The H N optimum parameters of a dynamic vibration absorber (DVA) with ground-support are derived to minimize the resonant vibration amplitude of a single degree-of-freedom (sdof) system under harmonic force excitation. The optimum parameters which are derived based on the classical fixed-points theory and reported in literature for this non-traditional DVA are shown to be not leading to the minimum resonant vibration amplitude of the controlled mass. A new procedure is proposed for the H N optimization of such a dynamic vibration absorber. A new set of optimum tuning frequency and damping of the absorber is derived, thereby resulting in lower maximum amplitude responses than those reported in the literature. The proposed optimized variant DVA is also compared to a ground-hooked damper of the same damping capacity of the damper in the DVA. It is proved that the proposed optimized DVA has better suppression of the resonant vibration amplitude of the controlled system than both the traditional DVA and also the ground-hooked damper if the proposed design procedure of the variant DVA is followed.
In this paper, the feasibility of the application of a dual mass flywheel (DMF) for heavy-duty truck drivetrain systems was studied. The third engine order vibration harmonic was in the focus of analysis as one of the most significant... more
In this paper, the feasibility of the application of a dual mass flywheel (DMF) for heavy-duty truck drivetrain systems was studied. The third engine order vibration harmonic was in the focus of analysis as one of the most significant contributions to the oscillatory response in the drivetrain systems of heavy-duty trucks. Global sensitivity analysis (GSA) and Pareto optimization were used for designing torsional vibration absorbers in an operating engine speed range of 600-2000 rpm. The optimization method attempted both to minimize the oscillations of the torque at the transmission input shaft and to maximize the energy efficiency of the vibration absorber. The GSA enabled the appropriate scanning of the domain of design parameters by varying all the parameters at the same time. It provided deep insight into the design process and increased the computational efficiency of the optimization. The results obtained show the following: the solution of the bi-objective optimization problem for torsional vibration absorbers does exist; Pareto fronts were obtained and analyzed for the DMF, presenting a trade-off between the measure of the attenuation of the oscillations of the torque at the transmission input shaft and the measure of the energy efficiency of the absorber; the optimized mass inertia, stiffness and damping parameters of a DMF do exist, providing the best attenuation of the torque oscillations; the performance of a DMF was further enhanced by incorporating a torsional tuned mass damper with appropriate optimized parameters. Finally, the results show evidence of the feasibility of the application of dual mass flywheels in heavy-duty truck drivetrain systems.
An active-passive dynamic vibration absorber with acceleration feedback is proposed to minimize the impulse response of a single degree-of-freedom (SDOF) system. It has been proved that the proposed hybrid vibration absorber provides... more
An active-passive dynamic vibration absorber with acceleration feedback is proposed to minimize the impulse response of a single degree-of-freedom (SDOF) system. It has been proved that the proposed hybrid vibration absorber provides better suppression of the impulse response of a single degree-of-freedom system than the traditional passive vibration absorber. The design parameters are the feedback gain, the tuning frequency ratio, the damping ratio and the mass ratio of the absorber. The effects of these parameters on the vibration absorption of the primary structure are analysed based on the analytical model. Design parameters of both passive and active elements of the HVA are optimized for minimizing the impulse response of the primary system. The proposed control system requires only one feedback signal which can be obtained directly using an accelerometer attached onto the primary mass. The control system may be implemented using an analogue circuit connecting an accelerometer, a power amplifier and an inertial actuator mounted onto the primary system. The control system of the proposed hybrid vibration absorber is much simpler than most of the control systems used on active control of vibration absorber found in the relevant literature.
H optimization of dynamic vibration absorber in single degree of freedom (SDOF) system is a classical optimization problem and it has been solved already for a long time. However, H optimization of dynamic vibration absorber in multi... more
H optimization of dynamic vibration absorber in single degree of freedom (SDOF) system is a classical optimization problem and it has been solved already for a long time. However, H optimization of dynamic vibration absorber in multi degrees of freedom (MDOF) has not been solved yet. Some authors found out the tuning of MDOF system but the methods are always numerical solutions and they cannot provide the physics insight to the tuning parameters. In this paper, we propose an analytical transfer function to find the optimal tuning of the absorber for vibrating plate structures and some insight of the tuning parameters of the absorber are provided based on the analytical model.
In this paper, the feasibility of the application of a dual mass flywheel (DMF) for heavy-duty truck drivetrain systems was studied. The third engine order vibration harmonic was in the focus of analysis as one of the most significant... more
In this paper, the feasibility of the application of a dual mass flywheel (DMF) for heavy-duty truck drivetrain systems was studied. The third engine order vibration harmonic was in the focus of analysis as one of the most significant contributions to the oscillatory response in the drivetrain systems of heavy-duty trucks. Global sensitivity analysis (GSA) and Pareto optimization were used for designing torsional vibration absorbers in an operating engine speed range of 600–2000 rpm. The optimization method attempted both to minimize the oscillations of the torque at the transmission input shaft and to maximize the energy efficiency of the vibration absorber. The GSA enabled the appropriate scanning of the domain of design parameters by varying all the parameters at the same time. It provided deep insight into the design process and increased the computational efficiency of the optimization. The results obtained show the following: the solution of the bi-objective optimization probl...
