Semi-active Vibration Reduction Research Articles

Research on semi-active vibration reduction of offshore wind turbine structure combined eddy current theory with tuned mass dampers

At present, the offshore wind power gradually shows a development trend towards the profound ocean with characteristic of larger capacity, higher tower and longer blades. Therefore, the offshore wind turbine (OWT) is more vulnerable to extreme loads and may lead to the negative influence of structural vibration safety. In this research, a new semi-active eddy current tuned mass damper (SEC-TMD) was proposed for the vibration control of OWT structures and its vibration reduction effect under multiple kinds of dynamic loads was also discussed. Firstly, taking one actual 3.0 MW OWT supported by bucket foundation as object, the SEC-TMD was designed based on the linear quadratic optimal control (LQR) algorithm and bounded Hrovat optimal control algorithm in order to obtain the optimal control force of structural vibration systems. The relationship between damping coefficient and magnetic conductivity spacing was further fitted to achieve variable damping control of SEC-TMD. Secondly, the theoretical model of 3.0 MW OWT structure installed with SEC-TMD was established and the effectiveness of the established theoretical model was verified through the comparison on modal analysis between the theoretical calculations and measured data identification. Finally, the vibration reduction effect of SEC-TMD on the measured OWT structure under wind-wave, seismic and vibration amplification conditions was analyzed and compared with the results calculated from the other passive dampers including EC-TMD and TLCD. It is shown that the maximum reduction percentage of peak value for vibration displacement and acceleration on the tower top can respectively reach 31.93 %, 44.11 %, 30.20 % and 54.57 %, 33.94 %, 31.75 % under three above conditions. Comparing with EC-TMD and TLCD, the better vibration reduction effect indicates that the proposed SEC-TMD has good engineering application value for the vibration suppression of OWT.

Multidiscipline Design Optimization for Large-Scale Complex Nonlinear Dynamic System Based on Weak Coupling Interfaces

For high-tech manufacturing industries, developing large-scale complex nonlinear dynamic systems must be taken as one of the basic works, formulating problems to be solved, steering system design in a more preferable direction, and making correct strategic decisions. By using effective tools of big data mining, Dynamic Design Methodology was proposed to establish a technical platform for Multidiscipline Design Optimization such as High-Speed Rolling Stock, including three key technologies: analysis graph of full-vehicle stability properties and variation patterns, improved transaction strategy of flexible body to MBS interface, seamless collaboration with weldline fatigue damage assessments through correct Modal Stress Recovery. By applying the above methodology, a self-adaptive improved solution was formulated with optimal parameter configuration, which is one of the more favorable options for higher-speed bogies. While within a velocity (140–200) km/h at λe < 0.10, car body instability’s influence on ride comfort can be easily improved by using a semi-active vibration reduction technique between inter-vehicles through outer windshields. Comprehensive evaluations show that only under rational conditions of wheel-rail matching, i.e., 0.10 ≥ λeN > λemin and λemin = (0.03–0.06), can this low-cost solution achieve the three goals of low track conicity, optimal route planning, and investment benefit maximization. So, rail vehicle experts are necessary to collaborate and innovate intensively with passenger transportation and steel rail ones. Specifically, by adopting rail grinding treatment, occurrence probability is controlled at 85% and 5% for track conicity of (0.03–0.10) and (0.25–0.35). By optimizing routing planning, operating across dedicated lines of different speed grades can achieve self-cleaning of central hollow tread wear over time. According to the inherent rigid-flex coupling relationship, geometric nonlinearities of worn wheel-rail contact should be avoided as much as possible for HSR practices. Only under weak coupling interfaces in the floor frame can the structural integrity of an aluminum alloy car body be ensured.

Research on semi-active control of long and large-span continuous beam bridge vibration reduction considering system fault tolerance

In order to reduce the seismic response of long and large-span continuous beam bridge, this paper carried out a study on vibration reduction control of long and large-span continuous beam bridge, and magnetorheological dampers are used to provide control force for the control scheme. Based on the LQR classic optimal active control algorithm, a semi-active control algorithm considering system fault tolerance is proposed. When some dampers fail, the fault-tolerant control algorithm provides compensation output to the control system, so that the control system can still maintain the expected control effect. The actual engineering example of a long and large-span continuous beam bridge is selected, and a finite element analysis program is written. The semi-active vibration reduction control of the long-span continuous beam bridge is calculated and analyzed in various combinations of working conditions. The calculation results show that the method in this paper has achieved good results in controlling the seismic response of the bridge structure.

High-speed elevator car system semi-active horizontal vibration reduction method based on the improved particle swarm algorithm

As the field of modern high-rise buildings advances, the demand for the high-speed elevator increases. The high-speed elevator car vibration directly affects the riding comforts, among which the high-speed elevator car horizontal vibration has the most pronounced effect. Previous researches indicate that the semi-active vibration reduction method is an effective horizontal vibration reduction method for elevator car, which has the characteristics of low energy consumption, suitable for high-speed elevator, while its adaptability is relatively weak. To address the adaptability issue, we proposed a semi-active high-speed elevator car horizontal vibration reduction method based on the improved particle swarm algorithm. To verify the feasibility of the proposed method, it is applied with a magneto-rheological damper in the KLK2-type elevator from Canny Elevator Co, Ltd The horizontal vibration results are compared with ones of the passive vibration reduction method and other algorithm-based vibration reduction methods. The vibration reduction method proposed in this paper is superior to all other mentioned methods in terms of the peak-to-peak value and the A95 value of the vibration acceleration. The horizontal vibration acceleration performance of the HSEC is improved by about 70%.

Vibration reduction by stiffness modulation – A theoretical study

Semi-active vibration reduction techniques are defined as techniques in which controlled actions do not operate directly on the system’s degrees of freedom (as in the case of active vibration control) but on the system’s parameters, i.e., mass, damping, or stiffness.Cyclic variations in the stiffness of a structural system have been addressed in several previous studies as an effective semi-active vibration reduction method. The proposed applications of this idea, denoted here as stiffness modulation, range from stepwise stiffness variations on a simple spring-mass system to continuous stiffness changes on rotor blades under aerodynamic loads.Semi-active systems are generally claimed to be energetically passive. However, changes in stiffness directly affect the elastic potential energy of the system and require external work under given conditions. In most cases, such injection or extraction of energy (performed by the device in charge of the stiffness variation and denoted as the pseudo-active effect) usually coexists with the semi-active effect, which operates by redistributing the potential energy within the system in such a way that it can be dissipated more efficiently.This work focuses on the discrimination between these two effects, which is absent in previous literature. A first study on their dependence on the process parameters of stiffness modulation is presented here, with emphasis on the spatial distribution of the stiffness changes. It is shown that localized changes tend to result in a larger semi-active share of vibration attenuation, whereas a spatially homogeneous stiffness modulation only generates a pseudo-active effect.

Development status and application prospect of semi-active vibration reduction technology for down-hole drilling tools

Domestic and foreign oil companies have been constantly increasing the research and development investment in underground shock absorber, to reduce the vibration and shock of drilling tool under hard rock drilling environments, enhance the rate of penetration and decrease drilling cost under the premise of ensuring the normal life of drill string components and stable bit weight. Based on this, this paper has focused on the working principal of magneto-rheological fluid (MRF) semi-active damper, the composition of MRF and its internal parameters’ impact on the damping characteristics, combining with the status quo at home and abroad of down-hole vibration technology. Meanwhile, the test analysis of semi-active damping technology was conducted. And the results showed that semi-active vibration technology had greatly weakened the vibration level while improved the rate of penetration, guaranteed the service life of bit and other drill-string components, reduced additional tripping times and effectively solved the problems of bit weight instability and low penetration rate etc., caused by drill vibration. Therefore, in the current situation of worldwide oil price downturn, it has become increasingly prominent to reduce cost and increase efficiency, and it’s particularly necessary to research on the shock absorbers of down-hole drilling tools in China.

Study on semi-active suspension applied on carbody underneath suspended system of high-speed railway vehicle

Considering the coupling vibration of a flexible carbody and the underneath suspended equipment, a vertical coupled vibration model of a high-speed train was constructed. A roller test rig was conducted to validate the theoretical model. To reduce carbody elastic vibration, the semi-active vibration reduction models based on the Sky-hook and the linear quadratic regulator control strategies were proposed. The semi-active suspension system was installed between the carbody and the suspended equipment, and the influence of the semi-active suspension on carbody vibration reduction was analyzed. The results show that the semi-active suspension can significantly reduce carbody vibration, especially at high operating speeds. The higher the elastic vibration of carbody, the better the vibration reduction effect of the semi-active suspension. Compared with the passive suspension and the semi-active suspension, the semi-active suspension of the Sky-hook control has a relatively wider vibration control range, and has an obvious effect on carbody rigid and elastic vibration reduction. Although the semi-active suspension of the linear quadratic regulator control had little influence on the rigid carbody vibration, it could reduce most of the elastic carbody vibration.

From acceleration-based semi-active vibration reduction control to functional observer design

Abstract This work investigates a functional estimation problem for single input single output linear and nonlinear systems, motivated by its enabling role in acceleration-based semi-active control. Solvability of a linear functional estimation problem is studied from a geometric approach, where the functional dynamics are derived, decomposed, and transformed to expose structural properties. This approach is extended to solve a challenging nonlinear functional observer problem, combining with the exact error linearization. Existence conditions of nonlinear functional observers are established. Simulation verifies existence conditions and demonstrates the effectiveness of the proposed functional observer designs.

Optimal switch timing for piezoelectric-based semi-active vibration reduction techniques

Piezoelectric-based semi-active vibration reduction techniques typically rely on rapid changes in the electrical boundary conditions or corresponding stiffness state. Approaches such as state switching and synchronized switch damping on a resistor or an inductor require four switching events per vibration cycle, with switch timing associated with displacement extrema. Any deviation from this switch timing affects the performance of these techniques. Typical harmonic forcing analyses focus on the energy dissipation and only evaluate the performance at resonance. This study evaluates displacement reduction for harmonic excitation, both at resonance and for frequencies near resonance. Furthermore, it examines the effect of sub-optimal switch timings. Numerical simulations of a non-dimensional model are performed, and an analytical solution is derived for any switch time. This analysis shows that the optimal switch timing depends on the forcing frequency relative to the natural frequency of the structure. Thus, the classical switch time at peak displacement is only optimal when the excitation is exactly at resonance. Even when the optimal switch timing is known, uncertainties in vibration sensing cannot guarantee that switches will occur at the desired moment. Therefore, this work characterizes the degradation in vibration reduction performance when switching away from the optimal switch time based on global, non-dimensional parameters.

A Comparison of Active and Semi-Active Sliding Mode Controllers Applied in Vibration Reduction Systems

The paper presents active and semi-active vibration reduction systems applying sliding mode control systems. Calculations were completed for a laboratory system with two masses moving in a vertical direction. Support of the system is connected with the moving part of the exciter. The proposed system may be a simple model of many vibroisolated objects. In order to apply the control system of vibrations in the suspension of the upper mass, an actuator was implemented together with a spring. The role of the actuator was played by a linear inductive motor.Active and semi-active sliding mode controllers are proposed for the vibration reduction system. Theoretical analysis focused on applying of the sliding mode control in this system was carried out and, moreover, conditions to be met by the controllers were determined. The results of simulations and experiments are presented in tables and plots.

Vibration Behavior of Flexible Rotor System Mounted on MR Squeeze Film Damper With Thermal Growth Effect

Semiactive vibration reduction devices using magnetorheological fluid (MR fluid) have proven to be effective in different engineering applications. MR squeeze film damper (MR-SFD) is one type of such devices that can be used to reduce unwanted vibration in rotary machinery. The behavior of these devices is a function of electric current, which controls the magnetic field in the lubricant and therefore causes the viscosity of MR fluid to be changed. In spite of all researches have been carried out in behavior analysis of different sorts of MR-SFDs, investigations over thermal growth effects on the efficiency of these actuators, in vibration reduction applications, are rare. In this paper, a Magnetorheological squeeze film damper (MR-SFD) has been modeled using two governing equations. First, considering the Bingham model for MR fluid (MRF), a hydrodynamic model has been presented. Second, a thermal model for the system has been modeled and used to calculate the temperature rise in the squeeze film and different damper’s components. Temperature rise in MR-SFD has been considered in this paper as a novel study. Time and frequency domain analysis using Newmark method has been performed over a finite element model of the system consisting of an unbalanced flexible rotor mounted on a pair of MR-SFDs. Obtained results show that the amplitude of rotor’s vibration is not a simple function of electrical current such that, increase in the current cannot guarantee decrease in the value of amplitude. Two major phenomena have been observed during studies; rigid dampers, and generation of new critical speed. The behavior of the rotor is deeply affected by these phenomena. The steady state response of rotor versus rotation velocity is presented for different values of electrical current, which show the effects of temperature and current on the steady state response of rotor. Generally, temperature rise results in inefficiency of MR-SFDs to suppress the vibration of the rotor, especially for rotational velocities near critical speed. Due to temperature rise, appearance of the second critical speed occurs at higher values of electrical current. In addition, it delays the “rigid damper” phenomenon causing rotor response to decrease.

Mathematical Model of a Shape Memory Alloy Spring Intended for Vibration Reduction Systems

The article discusses a prototype of a Shape Memory Alloy (SMA) spring intended for controlled vibration reduction systems. The spring has been subject to experiments and the article presents selected static and dynamic characteristics. The experiments were conducted at the Dynamics and Control of Structures Laboratory of the AGH University of Science and Technology. They permitted the formulation of a mathematical model for the SMA spring. The model takes into account the phenomena of energy accumulation and dissipation. The parameters of the spring model have been determined, based on the experimental data. The model takes into account the relationship of stiffness and damping to alloy temperature and the frequency of excitation. It has been demonstrated that the properties of the spring may be altered under controlled conditions. The spring model was then used in simulations. They served as the basis for the determination of the frequency response characteristics, which were then compared to the characteristics of a real spring. The mathematical model developed may be applied in the design of passive, semi-active, and active vibration reduction systems, as well as in the synthesis of adaptive smart vibration reduction systems.

Modified Clipped-LQR Method for Semi-Active Vibration Reduction Systems with Hysteresis

Smart materials are being applied more and more widely in semi-active vibration reduction systems. Actuators built with their use are characterized by nonlinearities and hysteretic effects. Their omission in mathematical descriptions may lead to deterioration of the vibration reduction systems. For that reason, it is important to take into account these negative phenomena associated with the actuators at the controller synthesis stage. One method for determining the control laws in semi-active vibration reduction systems that is frequently discussed in academic literature is “Clipped-LQR”. The present paper proposes modification of that method to allow inclusion in the controller synthesis of the hysteretic properties and other nonlinearities of an actuator. The method developed was verified by determining the controller for the semi-active suspension of a machine operator’s seat. A magnetorheological damper was used as an actuator. The dynamic properties of the foam covering of the operator’s seat were included in model. Simulation tests were performed on the vibration reduction system and function of vibration transmissibility was determined. The semi-active vibration reduction system tested was compared to a passive system. The considerations presented herein relate to the semi-active suspension of a machine operator’s seat, and the method presented may be applied to other controlled systems with many degrees of freedom.

Heuristic and Backstepping Control Strategies for Semiactive Suspension in Automotive Systems Equipped with MR Dampers

This paper deals with the problem of semiactive vibration reduction in a class of automotive systems. Most conventional suspensions use passive devices to absorb impacts and vibrations, which is generally difficult to adapt to the uncertain circumstances. Semiactive suspension techniques promise a solution to the above problem with some comparatively better features than active and passive suspension devices. In this work, the semiactive suspension with magnetorheological (MR) dampers is applied for the vibration attenuation. Both backstepping and heuristic control strategies are proposed. In the design of backstepping controller, the Dahl model of the MR damper is used to estimate the damping force of the semiactive device taking the control voltage and velocity inputs as variables and the semiactive control law takes into account the hysteretic nonlinearity of the MR damper. Two simple heuristic control strategies are also presented. The performance of the proposed semiactive suspension strategies are evaluated through an experimental platform for the semiactive vehicle suspension available in our laboratory.