Control Of Mechanical Vibrations Research Articles

Mechanical Characteristics and Vibration Control of Railway Signal Relay

Introduction: In order to solve the problems of time-consuming and poor effects of traditional mechanical vibration control methods for the relay, the mechanical characteristics and vibration control of railway signal relays are studied in this paper. Based on the analysis of the mechanical characteristics of railway signal relays, the mechanical characteristic parameters of the relay, such as contact force, initial pressure, contact clearance, and overtravel are explored. On this basis, mechanical vibration control is completed based on particle swarm optimization. Methods: First, sensors are used to collect the data on the railway signal relay, and the mechanical vibration control model of the railway signal relay is built. Then, the structure of the PID vibration controller and LQR vibration controller in the model is analyzed. Finally, the controller parameters are adjusted through particle swarm optimization to improve the mechanical vibration control effect of the relay. Results: The simulation results show that the average signal-to-noise ratio of the method is 67dB, the collected data has low noise, and the control time is short, which is 1.4 s. Conclusion: The displacement of the railway signal relay controlled by the method is always less than 0.15 mm, and the control effect is good, which can be widely used in practice.

A method for converting the existing mechanical zoom optical system to the focus tunable lens zoom optical system

The focus tunable lens (FTL), an emerging device, has brought a new development direction for the research of zoom optical systems, and the zoom lens designed with this lens has more advantages in response speed and mechanical vibration control than the conventional mechanical zoom system. However, there is a relative lack of design methods and computational theories for this type of system at present, and there is a lack of initial structure patents for reference. To solve this problem, this paper proposes a method that can convert the existing conventional mechanical zoom system into an FTL zoom system, and we first introduce the equivalent group element substitution theory for optical systems, then we design a computational screening algorithm for the equivalent FTL group element. We performed an example demonstration to illustrate the details of this method, and we finally obtain one FTL zoom optical system with an F/# of 4, a total length of 120 mm, and an 8 mm image plane. The whole design process is smooth, and the system structure is stable.

Study on Mechanical Vibration Control of Limit Cycle Oscillations in the Van der Pol Oscillator by means of Nonlinear Energy Sink

Study on Mechanical Vibration Control of Limit Cycle Oscillations in the Van der Pol Oscillator by means of Nonlinear Energy Sink

Subband reinforced adaptive feedback control algorithm in mechanical vibration control

In mechanical vibration control, the conventional least mean square (LMS)-based adaptive feedback control algorithm can hardly lead to a satisfying suppression of tonal vibrations when the disturbance is composed of multiple harmonics. The convergence rate of the conventional LMS-based adaptive feedback algorithm is analyzed, and it is revealed that the convergence rate is significantly affected by the magnitude product of the control channel and the disturbance. The smaller the magnitude product, the slower the convergence speed. Based on this analysis, a subband reinforced adaptive feedback control algorithm is proposed to increase the convergence rate in the frequency band of weak controllability. In this algorithm, the components of slow convergence rate are first extracted from the error signal with subband filters and then controlled independently to achieve fast attenuation. The role of these subband filters is to increase the magnitude product of associated components. Numerical and experimental results have shown that the reinforced adaptive control algorithm is effective and the tonal components, including those of weak controllability, are suppressed almost in the whole frequency range. The proposed algorithm can achieve better vibration attenuation than the conventional LMS-based adaptive feedback algorithm when the disturbance contains multiple harmonics.

Influence of temperature on the passive control of a rotating machine using wires of shape memory alloy in the suspension

This paper deals with the passive control of mechanical vibrations of rotating machines using wires of shape memory alloys (SMA). Unlike other classes of smart materials, the proposed technique allows for simpler mechanical construction and offers new technological possibilities. Both numerical simulations and experimental tests have been performed in the present investigation. The numerical results reveal that the SMA wires can reduce the amplitude of lateral vibrations of a rotating shaft to acceptable levels, as shown by time responses and orbit curves. Experimentally, it has been demonstrated that SMA wires confirm the simulation results regarding the reduction of the lateral vibration of a rotor system. It has also been verified that the temperature of the SMA wire can be employed to tune the vibration control system. In this context, passive control architecture is recommended in order to take advantage from an intrinsic characteristic of SMA wires.

Dipole states and coherent interaction in surface-acoustic-wave\xa0coupled phononic resonators

Manipulation of mechanical motion at the micro-scale has been attracting continuous attention, leading to the successful implementation of various strategies with potential impact on classical and quantum information processing. We propose an approach based on the interplay between a pair of localised mechanical resonators and travelling surface acoustic waves (SAW). We demonstrate the existence of a two-sided interaction, allowing the use of SAW to trigger and control the resonator oscillation, and to manipulate the elastic energy distribution on the substrate through resonator coupling. Observation of the vectorial structure of the resonator motion reveals the existence of two coupling regimes, a dipole-dipole-like interaction at small separation distance versus a surface-mediated mechanical coupling at larger separation. These results illustrate the potential of this platform for coherent control of mechanical vibration at a resonator level, and reciprocally for manipulating SAW propagation using sub-wavelength elements.

A Rapid Method Connecting Vibrating Structure Size, Piezo-Actuator Size, and Control Voltage for Noise Level Reduction on Oil Drilling Platforms

Scientific studies dealing with mechanical vibration attenuation by means of piezoelectric actuators are mostly focused on special details of structure modeling through finite elements and the amount of attenuation that can be achieved. However, a little explored issue in the scientific literature is the size of the actuator in relation to the size of the vibrating structure and the voltage applied to the piezoelectric actuator in order to achieve optimum vibration attenuation. This paper presents a theoretical and experimental study of mechanical vibration control of an aluminum plate with attached piezoelectric actuator. The aluminum plate was clamped at all four sides and a piezoelectric actuator based on lead zirconium titanate (PZT) was positioned at its center. Its natural frequency was close to 50 Hz, which is a frequency being constantly present on oil drilling platforms, producing annoying sound. The contribution of this paper is the determination of the relationship between the areas of the aluminum plate and the PZT actuator associated with the voltage value applied to the piezo-actuator for the purpose of vibration attenuation. The work demonstrates the possibility of the development of open-loop control using finite elements, to attenuate the vibration via piezoelectric actuator plates. This method makes it possible to vary the electric voltage across the piezoelectric actuator and/or the actuator dimensions involved, leading to the best attenuation condition. Numerical simulations and experimental results show the relation between size of the PZT actuator and the electric field which must be applied for best attenuation.

SEISMIC COMPARATIVE STUDY ON TMD STRUCTURE: AN OVERVIEW

In larger context of civil engineering use of mechanical vibration control device is very often in present days, so this paper will provide the successful implementation specification of TMD to reduce the vibration induced due earthquake ground motion, with computer stimulated model & dynamic responses are obtained for seismic loading with & without TMD which drastically reduces seismic response such as lateral displacement, story drift, base shear, overturning moment. Even actual behavior study on structure has been carried by inducing ground motion to the structure by considering time history data of El-Centro & recent earthquake (2014) which happened in India.

Active Mechanical Vibration Control of Rotary Compressors for Air-conditioning Systems

Recent power electronics and variable-frequency motor drive technologies have been applied to air conditioners to improve efficiency and power density. However, the mechanical vibrations and acoustic noise resulting from the compressor still remain as a serious problem. This paper presents the development and implementation of an online disturbance state-filter for the suppression of multiple unknown and time-varying vibrations of air conditioning systems. The proposed design has a form of the state-filter based on a Luenburger-style closed-loop speed observer. An active vibration decoupling strategy with an estimated disturbance is provided, which manipulates a motor torque command. Since the proposed estimation does not require any additional transducers or hardware for obtaining real-time information upon disturbances, it is suitable for retrofitting industrial air conditioners.

A gradient method for viscoelastic behaviour identification of damped sandwich structures

The damping properties estimation assumes a viscoelastic model calibrated from experiments and simulations. This Note presents a gradient method for viscoelastic behaviour identification of damped sandwich structures devoted to the passive control of mechanical vibration. The method combines experimental data, numerical simulations realized with a complex non-linear eigenvalue solver using the asymptotic numerical method, and optimal control for the identification of viscoelastic parameters. An automatic differentiation tool is used to get numerical derivatives exact up to the machine precision with minimal user effort. Results are presented for a sandwich beam with a frequency dependent viscoelastic core.

Active control of mechanical vibrations

Recent advances in digital signal processing and actuation technology have opened the door to applying active control to reducing mechanical vibrations and acoustic noise. Because these techniques work best at lower frequency, they complement conventional passive damping techniques, which are most effective at higher frequencies. Engineers in Lucent Technologies' Advanced Technology Systems have been developing active vibration and noise control systems for the Defense Advanced Research Project Agency (DARPA) and the Department of Defense (DoD) since 1988. This paper describes the design methodology of active control, the class of problems that responds best to this solution, and the complementary nature of active and passive vibration reduction strategies. It also gives a guide for when, where, and how to use active control to solve practical vibration problems.

仮想的なパラメータ変動を用いたロバスト安定性解析方法―保守性を低減化した解析方法の提案

In this paper, a robust stability analysis problem is considered. μ-Analysis is a useful tool in order to guarantee stability robustness, but obtained results by conventional procedures are sometimes conservative. On the other hand, to guarantee stability robustness of active control systems in space is extremely important. A new robust stability analysis procedure by using virtual parametric variations is proposed in order to carry out tight evaluation of the stability robustness for active control systems. Performance of the proposed procedure is verified by an example of a mechanical vibration control system.

On a Dynamic Variable Structure Control Approach for the Active Control of Mechanical Vibrations

In this paper we will consider asymptotic stabilization using both static and dynamic variable structure controllers for the active control of mechanical vibrations. The proposed approach is mainly based on geometric input-output linearization, and is applied to a mechanical system with one degree of freedom, which uses an electro-hydraulic actuator. Computer simulations are used to show that the dynamic variable structure control system proposed exhibits robust behavior in the face of external disturbances and parameter variations.

Pre-tensioned Layer Damping as a New Approach for Vibration Control of Elastic Beams

A new approach for suppression and control of mechanical vibration in elastic beams undergoing cyclic motion is presented. The proposed model is based on the idea of generating axial uniform damping forces on the surface of the vibrating structure. Equation of motion and expression for system damping of the new model are derived, where the effectiveness of this model for reducing lateral vibration of a base excited beam is theoretically determined at different force levels. The analysis included the first five mode shapes, and the performance at different boundary conditions is also discussed. The theoretical model is verified experimentally, and the technique used to generate the superficial forces is explained. A comparison between theoretical and experimental results is shown. It is found that the higher the generated superficial force value, the higher the attenuation percentage. The new model is characterized by its simplicity, which enhances its reliability and reduces its cost, as it provides the desired results with higher reliability and reasonable cost, compared with other approaches of active and intelligent structural designs.

Synthesis and implementation of sensor-less active shunt controllers for electromagnetically actuated systems

Electromagnetic transducers have been used extensively for active feedback control of mechanical vibration. In this paper, to reduce vibration, we demonstrate a new technique where an electrical impedance is connected to the terminals of an electromagnetic transducer. By measuring the coil terminal voltage and applying a related current, or vice-versa, vibration in the mechanical host system can be controlled. The task of impedance design is cast as a standard multi-input-multi-output (MIMO) control problem to facilitate synthesis by standard methods such as linear quadratic regulator (LQR) or H/sub 2/. Potential applications include: vehicle suspension systems, vibration isolation platforms, and the control of enclosed-sound fields. Active admittance or impedance controllers require no external sensors. The presented techniques are verified experimentally through the application to a single-degree-of-freedom (DOF) system.

Control orientated synthesis of high-performance piezoelectric shunt impedances for structural vibration control

Piezoelectric transducers are commonly used as strain actuators in the control of mechanical vibration. One control strategy, termed piezoelectric shunt damping, involves the connection of an electrical impedance to the terminals of a structurally bonded transducer. When subject to deflection, charge generated in the transducer flows through the external impedance developing a counteractive voltage across the terminals. Many passive, nonlinear, and semiactive impedance designs have been proposed that maximize this counteractive effect. This paper introduces a new technique for the design and implementation of piezoelectric shunt impedances. By considering the transducer voltage and charge as inputs and outputs, the design problem is reduced to a standard linear regulator problem enabling the application of standard synthesis techniques such as LQG, H/sub 2/, and H/sub /spl infin//. The resulting impedance is extensible to multitransducer systems, is unrestricted in structure, and is capable of minimizing an arbitrary performance objective. Experimental comparison to a resonant shunt circuit is carried out on a cantilever beam. Previous problems such as ad hoc tuning, limited performance, and sensitivity to variation in structural resonance frequencies are significantly alleviated.

Modal coupling in one-dimensional electromechanical structured continua

A passive continuously distributed control of mechanical vibrations is proposed. The piezoelectric actuators are interconnected by a linear electric transmission line. We introduce coupling and internal resonance criteria to determine the optimal choices for electric parameters. These criteria can be found decomposing the differential operator appearing in the linear evolution equations according to a partition of the state vector into mechanical and electrical parts. The results we find allow for the design of an experimental set up.

Application of Internal Model Based Controller to Active Vibration Suppression System

More and more attention has been attracted to active vibration control with intelligent materials such as piezoelectric materials, etc. This paper deals with the problem of active vibration control of mechanisms. An internal model based controller is suited for regulation problems with periodic disturbance or tracking problems with periodic input. It has the ability to reject periodic disturbances, at the same time it is robust to parameter perturbation. In this paper an internal model principle is introduced, and simulations are carried out to show its features. In addition, the control strategy is implemented for active vibration suppression of a flexible four bar linkage bonded with piezoelectric materials as sensors and actuators. When the mechanism rotates, periodic inertial forces serve as a disturbance to induce vibration along the flexible coupler. The purpose of the experiment is to suppress this vibration using a piezoelectric actuator. The experimental system is built up with computer, A/D and D/A converter, piezoelectric sensor and actuator, low-pass filter, voltage amplifier and charge amplifier. Encouraging results are gained when the strategy is implemented in the experiments.

Applications of electro-rheological fluids in vibration control: a survey

Electro-rheological (ER) fluids are now regarded as one of the most versatile of the materials available for building smart structures and machines. In principle, ER fluids promise an elegant means of providing continuously variable forces for the control of mechanical vibrations. In practice, the development of industrial devices has been hampered by the unavailability of suitable ER fluids. Prompted by recent advances in ER fluid development this paper provides a comprehensive survey of ER devices for vibration control. The key modes of operation are identified and progress towards a unified approach to visualizing the macroscopic behaviour is summarized before presenting a comprehensive survey which includes contributions to the identification of ER fluid dynamics and the application of feedback control. The discussion of results includes some thoughts on future trends.

Active Control of Mechanical Vibrations in a Circular Disk

Mechanical vibration is a common phenomenon observed in the operation of many machines and arises from the inertia effect of machine parts in motion. While many control system design methods for distributed parameter systems have already been proposed in the literature, generally they are either based on truncated models and, as a result, suffer from computational and “spillover” difficulties or require distributed parameter actuators which are rarely available in reality. Therefore, there is a definite need for the development of a class of controllers which can be realized by spatially discrete sensors and actuators and whose design specifically includes stabilization and control of all the higher frequency vibration modes. To address this need, we propose the design of linear compensators whose design is based on root locus arguments for infinite dimensional systems. Since the design is not based on finite dimensional models of the plant to be controlled, we expect it to perform well for those distributed parameter systems for which sufficiently accurate data on pole and zero locations can be obtained. In this paper we apply this approach to control mechanical vibrations in those physical systems which can be accurately modeled as a flexible circular disk. Computer simulation results indicate that all the predominant lower frequency vibrations can be efficiently eliminated by just a few pairs of colocated sensor and actuator.