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title = "Review of active vibration isolation strategies"
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author = ["Dehaeze Thomas"]
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Tags
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: [Vibration Isolation]({{< relref "vibration_isolation.md" >}})
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Reference
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: (<a href="#citeproc_bib_item_1">Collette, Janssens, and Artoos 2011</a>)
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Author(s)
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: Collette, C., Janssens, S., & Artoos, K.
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Year
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: 2011
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## Background and Motivations {#background-and-motivations}
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### Passive Isolation Tradeoffs {#passive-isolation-tradeoffs}
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1DoF Equations:
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\begin{equation}
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\boxed{X(s) = \underbrace{\frac{cs + k}{ms^2 + cs + k}}\_{T\_{wx}(s)} W(s) + \underbrace{\frac{1}{ms^2 + cs + k}}\_{T\_{Fx}(s)} F(s)}
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\end{equation}
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- \\(T\_{wx}(s)\\) is called the **transmissibility** of the isolator. It characterize the way seismic vibrations \\(w\\) are transmitted to the equipment.
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- \\(T\_{Fx}(s)\\) is called the **compliance**. It characterize the capacity of disturbing forces \\(F\\) to create motion \\(x\\) of the equipment.
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In order to minimize the vibrations of a sensitive equipment, a general objective to design a good isolator is to minimize both \\(\abs{T\_{wx}}\\) and \\(\abs{T\_{Fx}}\\) in the frequency range of interest.
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To decrease the amplitude of the overshoot at the resonance frequency, **damping** can be increased.
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The price to pay is degradation of the isolation at high frequency (the roll off becomes \\(-1\\) instead of \\(-2\\)).
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**First Trade-off**: Trade-off between damping and isolation.
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To improve the transmissibility, the resonance frequency can be decreased.
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However, the systems becomes more sensitive to external force \\(F\\) applied on the equipment.
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**Second trade-off**: Trade-off between isolation and robustness to external force
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### Active Isolation {#active-isolation}
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We apply a feedback control.
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The general expression of the force delivered by the actuator is \\(f = g\_a \ddot{x} + g\_v \dot{x} + g\_p x\\). \\(g\_a\\), \\(g\_v\\) and \\(g\_p\\) are constant gains.
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<a id="table--table:active-isolation"></a>
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<div class="table-caption">
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<span class="table-number"><a href="#table--table:active-isolation">Table 1</a>:</span>
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Active isolation techniques
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</div>
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| **Feedback Signal** | **Effect** | **Applications** |
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|---------------------|------------------------------------------|------------------|
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| Acceleration | Add virtual mass | Few |
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| Velocity | Add virtual dashpot connected to the sky | Sky-Hook Damping |
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| Position | Add virtual spring connected to the sky | Sky-Hook Spring |
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## Practical Realizations {#practical-realizations}
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## Sensor Limitations {#sensor-limitations}
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## Conclusions {#conclusions}
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<a id="figure--fig:collette11-comp-isolation-strategies"></a>
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{{< figure src="/ox-hugo/collette11_comp_isolation_strategies.png" caption="<span class='figure-number'>Figure 1: </span>Comparison of Active Vibration Isolation Strategies" >}}
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## Bibliography {#bibliography}
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<style>.csl-entry{text-indent: -1.5em; margin-left: 1.5em;}</style><div class="csl-bib-body">
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<div class="csl-entry"><a id="citeproc_bib_item_1"></a>Collette, C., S. Janssens, and K. Artoos. 2011. “Review of Active Vibration Isolation Strategies.” <i>Recent Patents on Mechanical Engineeringe</i> 4 (3): 212–19. doi:<a href="https://doi.org/10.2174/2212797611104030212">10.2174/2212797611104030212</a>.</div>
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</div>
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