Active vibration control

Active vibration control is the active application of force in an equal and opposite fashion to the forces imposed by external <a href="/facts/Vibration/sGgDqG71">vibration</a>. 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 <a href="/facts/Machinery/wTCxFRfs">machinery</a> is being affected by vibration. For example, the production of <a href="/facts/Semiconductor/zFf3mGTE">semiconductor</a> <a href="/facts/Wafer_(electronics)/lCBJAoUL">wafers</a> requires that the machines used for the <a href="/facts/Photolithography/FTHsauvy">photolithography</a> steps be used in an essentially vibration-free environment or the sub-<a href="/facts/Micrometre/7eDFxD2L">micrometre</a> features will be blurred. Active <a href="/facts/Vibration_control/JWUPa0lb">vibration control</a> 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 <a href="/facts/Damping_ratio/UW3RsjEd">dampers</a>, <a href="/facts/Shock_absorber/2FGD4PNh">shock absorbers</a>, and <a href="/facts/Base_isolation/rL9KnBby">base isolation</a>.
The typical active vibration control system uses several components:

<ul><li>A <a href="/facts/Mass/HHdc8XmF">massive</a> platform suspended by several active drivers (that may use <a href="/facts/Voice_coil/0Ugf4567">voice coils</a>, <a href="/facts/Hydraulic/KSIqLovc">hydraulics</a>, <a href="/facts/Pneumatics/QzkvCCpk">pneumatics</a>, <a href="/facts/Piezo-electric/65k6BDqx">piezo-electric</a> or other techniques)</li>
<li>Three <a href="/facts/Accelerometer/xxrXzrlI">accelerometers</a> that measure acceleration in the three <a href="/facts/Degrees_of_freedom_(physics_and_chemistry)/Rrjl0lnq">degrees of freedom</a></li>
<li>An <a href="/facts/Electronics/E4JhgISq">electronic</a> <a href="/facts/Amplifier/pnRgxncC">amplifier</a> system that <a href="/facts/Amplifier/pnRgxncC">amplifies</a> and inverts the <a href="/facts/Signal_(information_theory)/41YqUJ8c">signals</a> from the accelerometers. A <a href="/facts/PID_controller/7XcYk0CH">PID controller</a> can be used to get better performance than a simple inverting amplifier.</li>
<li>For very large systems, pneumatic or hydraulic components that provide the high drive power required.</li></ul>
If the vibration is <a href="/facts/Frequency/QUSbPaW8">periodic</a>, 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 <a href="/facts/Acceleration/UVDmjYvR">acceleration</a> without referring to past accelerations.
Active vibration control has been successfully implemented for vibration attenuation of <a href="/facts/Beam_(structure)/V9BPDeS8">beam</a>, <a href="/facts/Plate_(structure)/jLhVvh0T">plate</a> and <a href="/facts/Shell_(structure)/DBjRqIA1">shell</a> structures by numerous researchers.
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 (<a href="/facts/Feedback/XnuWH3zp">feedback</a> or <a href="/facts/Feed_forward_(control)/N2lyuRNm">feed forward</a>). The number of smart materials have been investigated and fabricated over the years; some of them are <a href="/facts/Shape-memory_alloy/dWInaJpt">shape memory alloys</a>, <a href="/facts/Piezoelectricity/65k6BDqx">piezoelectric</a> materials, <a href="/facts/Optical_fiber/5ruuIFbj">optical fibers</a>, <a href="/facts/Electro-rheological_fluid_damper/0W2GBq4V">electro-rheological</a> fluids, magneto-strictive materials.

Active vibration control open-in-new

Active vibration control