Numerical and Experimental Investigation of a Single-Axis Parallel Active Vibration Mount for Helicopter Seats Using Vibration Standards

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Amin Fereidooni ◽  
Silas Graham ◽  
Eric Chen ◽  
Viresh Wickramasinghe
Keyword(s):  
Vibration Isolation ◽  
Experimental Results ◽  
Least Mean Square ◽  
Axis Parallel ◽  
Active Vibration ◽  
Iso 2631 ◽  
The Given ◽  
Nonlinear Numerical Model ◽  
Good Agreement ◽  
Helicopter Vibration

Abstract This paper presents the experimental and numerical investigation of a single-axis replicate of a patented multi-axis active vibration isolation seat mount. Following the design of the multi-axis system, this single axis vibration isolation mount uses a flexible elastomer support placed in parallel with an electromagnetic actuator. This mount is designed to reduce the N/rev harmonic vibration of a helicopter using a filtered-X least mean square (FXLMS)-based controller. To improve the efficiency of the FXLMS controller for this application, the ISO-2631-1 Wk filter is added. Employing this modified controller, the experimental setup is tested using a payload mass representative of a 95th percentile pilot. The experimental results confirm the effectiveness of the proposed design in canceling the unwanted helicopter vibration, where the active mount effectively reduces the vibration representative of a Bell-412 helicopter by 69.37% (−10.28 dB, g-rms). In order to develop a better understanding of the problem, the system is also modeled from first principles in simulink. The comparison between the nonlinear numerical model and the experimental results demonstrates a good agreement between the two approaches. Moreover, it is shown that the addition of the ISO-2631-1 Wk filter improves the transient performance of the FXLMS controller for the given helicopter vibration profile.

Investigation of Efficiency of Vibration Isolation for Cabins of Self-Propelled Machines

1996 ◽  
Vol 15 (4) ◽  
pp. 157-160
Author(s):  
Mikhail (Yudimovich) Liberman
Keyword(s):  
Experimental Research ◽  
Vibration Isolation ◽  
Experimental Results ◽  
Vibration Isolators ◽  
Elastic Elements ◽  
Oscillatory Energy ◽  
Good Agreement

A method for calculation of the efficiency of vibration isolating systems, which are used in self-propelled machines, is presented. The influence of parameters of vibration isolating systems (masses and stiffnesses of foundation, load and elastic elements of vibration isolators, losses of oscillatory energy in elements of system) on efficiency of vibration isolation is determined. Good agreement is found between theoretical and experimental results. Results of experimental research for vibration isolating systems, which are used in real machines (excavator and tractor), are presented.

Development of Six Degrees of Freedom Vibration Isolation System for Microgravity Environment

1995 ◽  
Author(s):  
Toshiyuki Suzuki ◽  
Koji Tanida ◽  
Akira Tanji ◽  
Koichi Okubo
Keyword(s):  
Degrees Of Freedom ◽  
Vibration Isolation ◽  
Parabolic Flight ◽  
Microgravity Environment ◽  
External Disturbances ◽  
Isolation System ◽  
Vibration Isolation System ◽  
Six Degrees Of Freedom ◽  
Active Vibration ◽  
Good Agreement

Abstract An active vibration isolation system, under development for use in microgravity environment, provides electromagnetic suspension by means of voice coils arranged in pairs to control the translational and rotational movements of the payload, three pairs of which cover the three axes to ensure control of payload movement in all six degrees of freedom. A series of tests performed on this system in microgravity environment created by parabolic flight proved that external disturbances in frequencies above 0.1 Hz were effectively reduced by applying the system. Also, good agreement was obtained between the measured performance and results of numerical simulation.

Nonlinearity of Maglev Actuator and Adaptive Vibration Control Using Improved FxLMS Algorithm

2013 ◽  
Vol 390 ◽  
pp. 434-439 ◽  
Author(s):  
Yan Li ◽  
Lin He ◽  
Chang Geng Shuai
Keyword(s):  
Vibration Isolation ◽  
Least Mean Square ◽  
Isolation System ◽  
Vibration Isolation System ◽  
Fxlms Algorithm ◽  
Active Vibration ◽  
Spectrum Excitation ◽  
Least Mean Square Algorithm ◽  
Adaptive Vibration Control ◽  
Active Vibration Isolation

Maglev actuator is excellent for active vibration isolation, with non-contact form, low stiffness and rapid response. However, the actuators nonlinearity has to be restrained by the control algorithm. In this paper, the nonlinearity of maglev actuator was studied through theoretical analysis and experiment. An improved multi-channel FxLMS(filtered-x least mean square) algorithm was proposed, which considers the nonlinearity-induced harmonic frequency as extra line-spectrum excitation to control. Experiments showed that the improved FxLMS algorithm could efficiently compensate the nonlinearity of the actuators, thus had better effect when used in active vibration isolation system with non-linear actuators, compared with the traditional FxLMS method.

A Simple Novel Approach to Active Vibration Isolation With Electrohydraulic Actuation*

2003 ◽  
Vol 125 (1) ◽  
pp. 125-128 ◽  
Author(s):  
Yisheng Zhang ◽  
Andrew Alleyne
Keyword(s):  
Vibration Isolation ◽  
Difficult Problem ◽  
Experimental Results ◽  
Problem Representation ◽  
Tracking Problem ◽  
Loop Closure ◽  
Novel Approach ◽  
Active Vibration ◽  
Traditional Approaches ◽  
Active Vibration Isolation

This paper describes a novel reformulation of a classical active vibration isolation problem, explicitly accounting for the dynamics of the actuator. By utilizing a clever reformulation of the problem rather than the traditional approaches, a very difficult problem can be transformed into a relatively easy one. Subsequently, any reasonable loop closure methodology can be used to achieve the necessary performance. The traditional approaches usually consider a regulation problem, whereas the focus here will be on generating a tracking problem to achieve the same results: reduced transmission of vibration. Experimental results are included to demonstrate the effectiveness and advantages of the proposed problem representation.

The evaluation of two methods for active vibration damping using RUS Hexapod platform

2018 ◽  
Vol 41 (5) ◽  
pp. 1207-1215 ◽  
Author(s):  
Nael Nashawati ◽  
Chadi Albitar ◽  
Alaa Dib
Keyword(s):  
Vibration Isolation ◽  
Control Method ◽  
Least Mean Square ◽  
Spherical Joint ◽  
Low Frequencies ◽  
Feed Forward Control ◽  
Joint Structure ◽  
Active Vibration Damping ◽  
Fuzzy Logic Method ◽  
Active Vibration

This paper presents a study on active vibration Isolation using RUS (revolute joint, universal joint, spherical joint) structure of Stewart platform, as it is less expensive and easier to build than PSS (prismatic joint, spherical joint, spherical joint) structure, which is used a lot in this field. Two control methods are proposed; the fuzzy logic method and the adaptive feed forward control method with multiple error least mean square. Results are evaluated using the SimMechanics toolbox under Matlab 2014 with white noise signals to simulate vibrations. In addition, practical measured accelerations are applied and results are evaluated. Both strategies use a proportional–integral–derivative (PID) controller in parallel to control displacements of the Hexapod as vibrations at low frequencies generate high variations in displacements. The results prove that using a Hexapod with RUS structure can degrade vibrations and guarantee a good behavior for many applications, which is the main aim of this research.

Dynamics Enhancements of Advanced LIGO Multi-Stage Active Vibration Isolators and Related Control Performance Improvement

2012 ◽  
Author(s):  
Fabrice Matichard ◽  
Ken Mason ◽  
Richard Mittleman ◽  
Brian Lantz ◽  
Ben Abbott ◽  
...  
Keyword(s):  
Vibration Isolation ◽  
Experimental Results ◽  
Dynamical Response ◽  
Control Performance ◽  
Vibration Isolators ◽  
Multi Stage ◽  
Final Design ◽  
Active Vibration ◽  
And Performance ◽  
Isolation Systems

The control bandwidth and performance of active vibration isolation systems are usually directly related to the system dynamic characteristics. In this paper, we present results from a 4 years study carried out to improve the dynamical response and control performance on the two-stage isolator designed for Advanced LIGO detectors. The paper will focus on the platform’s first stage to illustrate prototyping, optimization, final design and the experimental results obtained during this program. The system concept, architecture and prototype will be presented. The factors initially limiting the prototype’s performance will be analyzed. Solutions based on sensors relocation, payload reduction, structural stiffening and passive techniques to damp the residual high frequency flexible modes will be presented. Experimental results obtained with the prototype will be compared with the system’s final version. The series of improvement obtained help not only to increase the system’s bandwidth, robustness and performance but also to simplify and speed up the control commissioning, which is very important for the Advanced LIGO project that will be using 5 of these platforms in each of its 3 detectors.

Adaptive Least-Mean Square Feed-Forward Control With Actuator Saturation by Direct Minimization

2005 ◽  
Author(s):  
Lei Zuo ◽  
Samir A. Nayfeh
Keyword(s):  
Vibration Isolation ◽  
Actuator Saturation ◽  
Ground Vibration ◽  
Lms Algorithm ◽  
Mean Square ◽  
Least Mean Square ◽  
Control Effort ◽  
Isolation System ◽  
Active Vibration ◽  
The Cost

The least-mean squares (LMS) adaptive feedforward algorithm is used widely for vibration and noise cancellation. If reference signals become large enough to saturate that actuators, the filter coefficients in such algorithms can diverge. The leaky LMS method limits the controller effort by augmenting the objective function by a weighted control effort, and is known to attain good performance and avoid growth of filter coefficients for well-chosen weights. We propose an algorithm that seeks to directly minimize the mean-square cost in the presence of saturation. We derive the true stochastic gradient of the cost for systems with saturation with respect to the filter coefficients and obtain an adaptation rule very close to that of the filtered-x algorithm, but in the proposed algorithm, the reference filter is a time-varying modification of the secondary channel. In simulations of an active vibration isolation system with actuator limits subject to random ground vibration, the leaky LMS algorithm attains its best performance with actuation weights small enough to allow significant actuator saturation but large enough to prevent divergence. The proposed algorithm attains performance better that attained by the leaky LMS algorithm, and does not require the selection of weights.

Parallel Vibration Isolation Platform Using Magnetorheological Technology

2014 ◽  
Vol 574 ◽  
pp. 596-602 ◽  
Author(s):  
Qiang Wang ◽  
Zhao Bo Chen ◽  
Mehdi Ahmadian ◽  
Wen Tao Liu
Keyword(s):  
Vibration Isolation ◽  
Mr Damper ◽  
Mr Dampers ◽  
Nonlinear Hysteresis ◽  
Output Force ◽  
Axis Parallel ◽  
Active Vibration ◽  
Parallel Platform ◽  
Long Stroke ◽  
Large Output

Within this work, a six-axis parallel vibration isolation platform with semi-active control ability is investigated. Traditional magnetorheological (MR) dampers could supply large output force and long stroke, but it also comes with a large self-weight. This problem is more serious when several MR dampers are needed in a parallel platform. Firstly, a double-piston MR damper have been developed, which will brings a small self-weight feature to the damper. Hyperbolic tangent model have been used to describe damper's nonlinear hysteresis. Using six of this double-piston MR damper, a parallel vibration isolation platform based on a cubic Stewart platform mechanism has been designed. Dynamical model of this platform has been built and simulated. Numerical simulation results in frequency domain indicate that the parallel semi-active vibration isolation platform has desirable vibration isolation properties in all six axes.

Inducing Frictional Force to Enhance the Transient Response in Beams

2019 ◽  
Vol 22 (2) ◽  
pp. 88-93
Author(s):  
Hamed Khanger Mina ◽  
Waleed K. Al-Ashtrai
Keyword(s):  
Numerical Analysis ◽  
Transient Response ◽  
Frictional Force ◽  
Damping Ratio ◽  
Experimental Results ◽  
Damping Capacity ◽  
Tightening Force ◽  
Contact Areas ◽  
Good Agreement ◽  
Ansys Workbench

This paper studies the effect of contact areas on the transient response of mechanical structures. Precisely, it investigates replacing the ordinary beam of a structure by two beams of half the thickness, which are joined by bolts. The response of these beams is controlled by adjusting the tightening of the connecting bolts and hence changing the magnitude of the induced frictional force between the two beams which affect the beams damping capacity. A cantilever of two beams joined together by bolts has been investigated numerically and experimentally. The numerical analysis was performed using ANSYS-Workbench version 17.2. A good agreement between the numerical and experimental results has been obtained. In general, results showed that the two beams vibrate independently when the bolts were loosed and the structure stiffness is about 20 N/m and the damping ratio is about 0.008. With increasing the bolts tightening, the stiffness and the damping ratio of the structure were also increased till they reach their maximum values when the tightening force equals to 8330 N, where the structure now has stiffness equals to 88 N/m and the damping ratio is about 0.062. Beyond this force value, increasing the bolts tightening has no effect on stiffness of the structure while the damping ratio is decreased until it returned to 0.008 when the bolts tightening becomes immense and the beams behave as one beam of double thickness.

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