Analytical and experimental investigations into active control of wave transmission through gearbox struts

2000 ◽  
Author(s):  
Ion Pelinescu ◽  
Balakumar Balachandran
Keyword(s):  
Active Control ◽  
Wave Transmission ◽  
Experimental Investigations

Adaptable pneumatic shock absorber

2018 ◽  
Vol 25 (3) ◽  
pp. 711-721 ◽  
Author(s):  
Rami Faraj ◽  
Cezary Graczykowski ◽  
Jan Holnicki-Szulc
Keyword(s):  
Active Control ◽  
Smart Materials ◽  
Shock Absorber ◽  
High Efficiency ◽  
Low Cost ◽  
Electronic System ◽  
Experimental Investigations ◽  
Adaptation Mechanism ◽  
Impact Absorption ◽  
Pneumatic Shock

Recent progress in the field of sensors, actuators, and smart materials allows the construction of more and more efficient controllable pneumatic dampers for shock absorption. Typically, such devices apply online semi-active control techniques, which utilize electromagnetic, piezoelectric, or magnetostrictive valves. As a result, they are characterized by a high efficiency of impact absorption, but simultaneously by a complicated construction and a specialized electronic system. The alternative solutions are semi-passive absorbers that ensure a similar performance by using a much simpler, low-cost construction and a less complicated adaptation mechanism. This paper introduces an adaptable semi-passive single-chamber pneumatic shock absorber, SOFT-DROP, which provides the optimal impact absorption and energy dissipation after a single reconfiguration performed at the beginning of the process. The high effectiveness of the proposed concept is proved in numerical and experimental investigations of the device. Moreover, the proposed semi-passive damper is also compared against already known pneumatic absorbers that utilize semi-active control methods. Ultimately, the device might be used in an airdrop system for delivery of light packages.

Passive and Active Control of Solar Array Vibrations Induced by the Change of Thermal Input

1999 ◽  
Author(s):  
L. Tabacchi ◽  
M. C. Natori
Keyword(s):  
Active Control ◽  
Closed Loop ◽  
Point Of View ◽  
Pole Placement ◽  
Solar Array ◽  
Space Structures ◽  
Experimental Investigations ◽  
Flexible Space Structures ◽  
Satellite Attitude ◽  
Cyclic Temperature

Abstract The behaviour of large and flexible space structures, if compared with compact and rigid ones, is largely influenced by thermal loads in orbit. In this paper, the control of a spacecraft attitude disturbance, induced by cyclic temperature variations in the solar array substructures, is investigated. Both passive and active control techniques have been considered to reduce the vibration amplitude. A new version of tension mechansim powered by constant force springs is compared with a previous mechanism from the point of view of induced disturbances in the satellite attitude. A new algorithm for closed-loop pole placement of a symmetric, second order dynamical system is presented, and results of closed-loop numerical simulations are shown. Finally, experimental investigations are discussed and the relative results are presented.

An Active-Passive Piezoelectric Absorber for Structural Vibration Control Under Harmonic Excitations With Time-Varying Frequency, Part 1: Algorithm Development and Analysis

2001 ◽  
Vol 124 (1) ◽  
pp. 77-83 ◽  
Author(s):  
R. A. Morgan ◽  
K. W. Wang
Keyword(s):  
Active Control ◽  
High Performance ◽  
Piezoelectric Materials ◽  
Negative Resistance ◽  
Electrical Circuit ◽  
Structural Vibration ◽  
Experimental Investigations ◽  
Electrical Networks ◽  
Practical Applications ◽  
Harmonic Excitations

It has been shown that piezoelectric materials can be used as passive electromechanical vibration absorbers by shunting them with electrical networks. Semi-active piezoelectric absorbers have also been proposed for suppressing harmonic excitations with varying frequency. However, these semi-active devices have limitations that restrict their practical applications. The approach presented here is a high performance active-passive alternative to semi-active absorbers. By utilizing a combination of a passive electrical circuit and active control actions, the system is synthesized for adaptive variable frequency narrowband disturbance rejection. The active control consists of three parts: an inductor tuning action, a negative resistance action, and a coupling enhancement action. In the current paper (Part 1), the control algorithm is developed and analyzed. Part 2 of the paper contains experimental investigations and parametric studies of the new absorber design.

scholarly journals Experimental Investigations on Wave Transmission at Submerged Breakwater with Smooth and Stepped Slopes

2015 ◽  
Vol 116 ◽  
pp. 713-719 ◽  
Author(s):  
Lokesha ◽  
N.B. Kerpen ◽  
S.A. Sannasiraj ◽  
V. Sundar ◽  
T. Schlurmann
Keyword(s):  
Wave Transmission ◽  
Experimental Investigations ◽  
Submerged Breakwater

Experimental investigations on active control of multifrequency helicopter vibrations using discrete model predictive sliding mode control

2017 ◽  
Vol 232 (15) ◽  
pp. 2898-2909
Author(s):  
Xunjun Ma ◽  
Yang Lu ◽  
Fengjiao Wang
Keyword(s):  
Active Control ◽  
Discrete Model ◽  
Sliding Mode ◽  
Structural Response ◽  
Test System ◽  
Experimental Investigations ◽  
Least Mean Square ◽  
Single Input Single Output ◽  
Control Approach ◽  
Practical Applications

The presented experimental results illustrate the recent advances in the reduction of multifrequency vibrations of helicopter fuselage using an active control of structural response system. Recently, to cancel the multifrequency helicopter vibrations, a hybrid control approach has been proposed combining the filtered-x least mean square algorithm with a discrete model predictive sliding mode controller. To verify its effectiveness and self-adaptability, a set of active control experiments of structural response are conducted on a free–free elastic beam, which simulates a helicopter in flight. Considering that the helicopter vibrations in practical applications are much more complex, the further experiments of real-time active control are performed using a model helicopter test system. Higher discrete frequency components, which are actually of concern, are selected as the control objectives during the tests. The algorithm’s control effects are sufficiently checked by single-input single-output and multiple-input multiple-output tests under different excitation conditions. For many cases the attenuation of measured response exceed level of 20 dB, with maximum reduction reaching 34.1 dB. These two sets of tests confirm that the active control system is practical for canceling the multifrequency helicopter vibrations.

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