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content/article/ito16_compar_class_high_precis_actuat.md

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+title = "Comparison and classification of high-precision actuators based on stiffness influencing vibration isolation"
+author = ["Dehaeze Thomas"]
+draft = false
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+
+Tags
+: [Vibration Isolation]({{< relref "vibration_isolation.md" >}}), [Actuators]({{< relref "actuators.md" >}})
+
+Reference
+: (<a href="#citeproc_bib_item_1">Ito and Schitter 2016</a>)
+
+Author(s)
+: Ito, S., &amp; Schitter, G.
+
+Year
+: 2016
+
+
+## Classification of high-precision actuators {#classification-of-high-precision-actuators}
+
+<div class="table-caption">
+  <span class="table-number">Table 1:</span>
+  Zero/Low and High stiffness actuators
+</div>
+
+| **Categories** | **Pros**                  | **Cons**                    |
+|----------------|---------------------------|-----------------------------|
+| Zero stiffness | No vibration transmission | Large and Heavy             |
+| Low stiffness  | High vibration isolation  | Typically for low load      |
+| High Stiffness | High control bandwidth    | High vibration transmission |
+
+
+## Time Delay of Piezoelectric Electronics {#time-delay-of-piezoelectric-electronics}
+
+In this paper, the piezoelectric actuator/electronics adds a time delay which is much higher than the time delay added by the voice coil/electronics.
+
+
+## Definition of low-stiffness and high-stiffness actuator {#definition-of-low-stiffness-and-high-stiffness-actuator}
+
+-   **Low Stiffness** actuator is defined as the ones where the transmissibility stays below 0dB at all frequency
+-   **High Stiffness** actuator is defined as the ones where the transmissibility goes above 0dB at some frequency
+
+<a id="figure--fig:ito16-low-high-stiffness-actuators"></a>
+
+{{< figure src="/ox-hugo/ito16_low_high_stiffness_actuators.png" caption="<span class='figure-number'>Figure 1: </span>Definition of low-stiffness and high-stiffness actuator" >}}
+
+
+## Low-Stiffness / High-Stiffness characteristics {#low-stiffness-high-stiffness-characteristics}
+
+-   The low stiffness actuators achieve smooth transition from active isolation to passive isolation.
+-   The high stiffness actuators can have a gap between the passive and active isolation vibration where the vibrations are amplified in a certain frequency band.
+
+
+## Controller Design {#controller-design}
+
+<a id="figure--fig:ito16-transmissibility"></a>
+
+{{< figure src="/ox-hugo/ito16_transmissibility.png" caption="<span class='figure-number'>Figure 2: </span>Obtained transmissibility" >}}
+
+
+## Discussion {#discussion}
+
+The stiffness requirement for low-stiffness actuators can be rephrased in the frequency domain as: "the cross-over frequency of the sensitivity function of the feedback system must be larger than \\(\sqrt{2} \omega\_r\\) with \\(\omega\_r\\) is the resonant frequency of the uncontrolled system".
+
+In practice, this is difficult to achieve with piezoelectric actuators as their first resonant frequency \\(\omega\_r\\) is **too close to other resonant frequencies to ensure close-loop stability**.
+In contrast, the frequency band between the first and the other resonances of Lorentz actuators can be broad by design making them more suitable to construct a low-stiffness actuators.
+
+
+## Bibliography {#bibliography}
+
+<style>.csl-entry{text-indent: -1.5em; margin-left: 1.5em;}</style><div class="csl-bib-body">
+  <div class="csl-entry"><a id="citeproc_bib_item_1"></a>Ito, Shingo, and Georg Schitter. 2016. “Comparison and Classification of High-Precision Actuators Based on Stiffness Influencing Vibration Isolation.” <i>IEEE/ASME Transactions on Mechatronics</i> 21 (2): 1169–78. doi:<a href="https://doi.org/10.1109/tmech.2015.2478658">10.1109/tmech.2015.2478658</a>.</div>
+</div>