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3.6 KiB
Markdown
72 lines
3.6 KiB
Markdown
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title = "Comparison and classification of high-precision actuators based on stiffness influencing vibration isolation"
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author = ["Thomas Dehaeze"]
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Tags
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: [Vibration Isolation]({{< relref "vibration_isolation" >}}), [Actuators]({{< relref "actuators" >}})
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Reference
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: <sup id="aad53368e29e8a519e2f63857044fa46"><a href="#ito16_compar_class_high_precis_actuat" title="Shingo Ito \& 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>
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Author(s)
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: Ito, S., & Schitter, G.
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Year
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: 2016
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## Classification of high-precision actuators {#classification-of-high-precision-actuators}
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<div class="table-caption">
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<span class="table-number">Table 1</span>:
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Zero/Low and High stiffness actuators
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</div>
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| **Categories** | **Pros** | **Cons** |
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|----------------|---------------------------|-----------------------------|
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| Zero stiffness | No vibration transmission | Large and Heavy |
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| Low stiffness | High vibration isolation | Typically for low load |
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| High Stiffness | High control bandwidth | High vibration transmission |
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## Time Delay of Piezoelectric Electronics {#time-delay-of-piezoelectric-electronics}
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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.
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## Definition of low-stiffness and high-stiffness actuator {#definition-of-low-stiffness-and-high-stiffness-actuator}
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- **Low Stiffness** actuator is defined as the ones where the transmissibility stays below 0dB at all frequency
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- **High Stiffness** actuator is defined as the ones where the transmissibility goes above 0dB at some frequency
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{{< figure src="/ox-hugo/ito16_low_high_stiffness_actuators.png" caption="Figure 1: Definition of low-stiffness and high-stiffness actuator" >}}
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## Low-Stiffness / High-Stiffness characteristics {#low-stiffness-high-stiffness-characteristics}
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- The low stiffness actuators achieve smooth transition from active isolation to passive isolation.
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- 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.
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## Controller Design {#controller-design}
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{{< figure src="/ox-hugo/ito16_transmissibility.png" caption="Figure 2: Obtained transmissibility" >}}
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## Discussion {#discussion}
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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".
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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**.
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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.
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# Bibliography
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<a id="ito16_compar_class_high_precis_actuat"></a>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 [↩](#aad53368e29e8a519e2f63857044fa46)
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## Backlinks {#backlinks}
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- [Actuators]({{< relref "actuators" >}})
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