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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 = ["Thomas Dehaeze"]
+draft = false
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+
+Tags
+: [Vibration Isolation]({{< relref "vibration_isolation" >}}), [Actuators]({{< relref "actuators" >}})
+
+Reference
+: <sup id="aad53368e29e8a519e2f63857044fa46"><a class="reference-link" href="#ito16_compar_class_high_precis_actuat" title="Shingo Ito \&amp; Georg Schitter, Comparison and Classification of High-Precision Actuators  Based on Stiffness Influencing Vibration Isolation, {IEEE/ASME Transactions on Mechatronics}, v(2), 1169-1178 (2016).">(Shingo Ito \& Georg Schitter, 2016)</a></sup>
+
+Author(s)
+: Ito, S., & 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="orgffb6d7f"></a>
+
+{{< figure src="/ox-hugo/ito16_low_high_stiffness_actuators.png" caption="Figure 1: 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="org658b9e0"></a>
+
+{{< figure src="/ox-hugo/ito16_transmissibility.png" caption="Figure 2: 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
+<a class="bibtex-entry" id="ito16_compar_class_high_precis_actuat">Ito, S., & Schitter, G., *Comparison and classification of high-precision actuators based on stiffness influencing vibration isolation*, IEEE/ASME Transactions on Mechatronics, *21(2)*, 1169–1178 (2016).  http://dx.doi.org/10.1109/tmech.2015.2478658</a> [↩](#aad53368e29e8a519e2f63857044fa46)
+
+
+## Backlinks {#backlinks}
+
+-   [Actuators]({{< relref "actuators" >}})