Editing Active vibration control

{{More citations needed|date=January 2017}}
[[File:Test Bench at the Fraunhofer LBF for active vibration control.jpg|thumb|right|350px|Test bench for active vibration control at the Fraunhofer Institute LBF. A piezo driven active engine mount cancels the vibration resulting from several motors on top of the Mount by inducing countervibrations.]]
'''Active vibration control''' is the active application of force in an equal and opposite fashion to the forces imposed by external [[vibration]].  With this application, a precision industrial process can be maintained on a platform essentially vibration-free.

Many precision industrial processes cannot take place if the [[machinery]] is being affected by vibration. For example, the production of [[semiconductor]] [[Wafer (electronics)|wafers]] requires that the machines used for the [[photolithography]] steps be used in an essentially vibration-free environment or the sub-[[micrometre]] features will be blurred. Active [[vibration control]] is now also commercially available for reducing vibration in helicopters, offering better comfort with less weight than traditional passive technologies.

In  the past, passive techniques were used. These include traditional vibration [[Damping ratio|dampers]], [[shock absorber]]s, and [[base isolation]].

The typical active vibration control system uses several components:
* A [[mass]]ive platform suspended by several active drivers (that may use [[voice coil]]s, [[hydraulic]]s, [[pneumatics]], [[piezo-electric]] or other techniques)
* Three [[accelerometer]]s that measure acceleration in the three [[degrees of freedom (physics and chemistry)|degrees of freedom]]
* An [[electronics|electronic]] [[amplifier]] system that [[Amplifier|amplifies]] and [[:wikt:invert|invert]]s the [[Signal (information theory)|signals]] from the accelerometers. A [[PID controller]] can be used to get better performance than a simple inverting amplifier.
* For very large systems, pneumatic or hydraulic components that provide the high drive power required.

If the vibration is [[Frequency|periodic]], then the control system may adapt to the ongoing vibration, thereby providing better cancellation than would have been provided simply by reacting to each new [[acceleration]] without referring to past accelerations.

Active vibration control has been successfully implemented for vibration attenuation of [[Beam (structure)|beam]], [[Plate (structure)|plate]] and [[Shell (structure)|shell]] structures by numerous researchers.<ref name=":0">{{Cite book|title = Vibration control of active structures: An Introduction|last = Preumont|first = A.|publisher = Springer|year = 2011}}</ref><ref>{{Cite journal|title = Active vibration control of smart piezoelectric beams: Comparison of classical and optimal feedback control strategies|journal = Computers & Structures|date = 2006-09-01|pages = 1402–1414|volume = 84|series = Composite Adaptive Structures: Modelling and Simulation|issue = 22–23|doi = 10.1016/j.compstruc.2006.01.026|first1 = C. M. A.|last1 = Vasques|first2 = J.|last2 = Dias Rodrigues}}</ref><ref>{{Cite journal|title = Consensus positive position feedback control for vibration attenuation of smart structures|journal = Smart Materials and Structures|date = 2015-02-27|pages = 045016 (11pp)|volume = 24|issue = 4|doi = 10.1088/0964-1726/24/4/045016|first1 = Ehsan|last1 = Omidi|first2 = S. Nima|last2 = Mahmoodi|bibcode = 2015SMaS...24d5016O| s2cid=110962882 }}</ref><ref>{{Cite journal|title = Optimal placement and active vibration control for piezoelectric smart flexible cantilever plate|journal = Journal of Sound and Vibration|date = 2007-04-03|pages = 521–543|volume = 301|issue = 3–5|doi = 10.1016/j.jsv.2006.10.018|first1 = Zhi-cheng|last1 = Qiu|first2 = Xian-min|last2 = Zhang|first3 = Hong-xin|last3 = Wu|first4 = Hong-hua|last4 = Zhang|bibcode = 2007JSV...301..521Q}}</ref><ref>{{Cite journal|title = Lead-free piezoelectric materials' performance in structural active vibration control|journal = Journal of Intelligent Material Systems and Structures|date = 2014-09-01|issn = 1045-389X|pages = 1596–1604|volume = 25|issue = 13|doi = 10.1177/1045389X13510222|language = en|first1 = Anshul|last1 = Sharma|first2 = Rajeev|last2 = Kumar|first3 = Rahul|last3 = Vaish|first4 = Vishal S.|last4 = Chauhan| s2cid=110356866 }}</ref><ref>{{Cite journal|title = Active vibration control of space antenna reflector over wide temperature range|journal = Composite Structures|date = 2015-09-15|pages = 291–304|volume = 128|doi = 10.1016/j.compstruct.2015.03.062|first1 = Anshul|last1 = Sharma|first2 = Rajeev|last2 = Kumar|first3 = Rahul|last3 = Vaish|first4 = Vishal S.|last4 = Chauhan}}</ref>
For effective active vibration control, the structure should be smart enough to sense external disturbances and react accordingly. In order to develop an active structure (also known as smart structure), smart materials must be integrated or embedded with the structure. The smart structure involves sensors (strain, acceleration, velocity, force etc.), actuators (force, inertial, strain etc.) and a control algorithm ([[feedback]] or [[Feed forward (control)|feed forward]]).<ref name=":0" /> The number of smart materials have been investigated and fabricated over the years; some of them are [[Shape-memory alloy|shape memory alloys]], [[Piezoelectricity|piezoelectric]] materials, [[optical fiber]]s, [[Electro-rheological fluid damper|electro-rheological]] fluids, magneto-strictive materials.<ref>{{Cite book|title = Smart materials and structures|last = Gandhi|first = M.V.|publisher = Springer|year = 1992}}</ref>

==See also==
* [[Active noise control]]
* [[Active vibration isolation]]
* [[Magnetorheological fluid]]
* [[Noise-cancelling headphones]]

== References ==
{{Reflist}}

{{Authority control}}

{{DEFAULTSORT:Active Vibration Control}}
[[Category:Mechanical vibrations]]
[[Category:Earthquake engineering]]