63 lines
2.5 KiB
Markdown
63 lines
2.5 KiB
Markdown
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title = "A soft 6-axis active vibration isolator"
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author = ["Thomas Dehaeze"]
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draft = false
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Tags
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: [Stewart Platforms]({{< relref "stewart_platforms" >}}), [Vibration Isolation]({{< relref "vibration_isolation" >}})
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Reference
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: <sup id="a48f6708d087625a42ca2375407a2bc4"><a href="#spanos95_soft_activ_vibrat_isolat" title="Spanos, Rahman \& Blackwood, A Soft 6-axis Active Vibration Isolator, nil, in in: {Proceedings of 1995 American Control Conference - ACC'95}, edited by (1995)">(Spanos {\it et al.}, 1995)</a></sup>
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Author(s)
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: Spanos, J., Rahman, Z., & Blackwood, G.
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Year
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: 1995
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**Stewart Platform** (Figure [1](#org4317d08)):
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- Voice Coil
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- Flexible joints (cross-blades)
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- Force Sensors
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- Cubic Configuration
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<a id="org4317d08"></a>
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{{< figure src="/ox-hugo/spanos95_stewart_platform.png" caption="Figure 1: Stewart Platform" >}}
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Total mass of the paylaod: 30kg
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Center of gravity is 9cm above the geometry center of the mount (cube's center?).
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Limitation of the **Decentralized Force Feedback**:
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- high frequency pole due to internal resonances of the struts
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- low frequency zero due to the rotational stiffness of the flexible joints
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After redesign of the struts:
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- high frequency pole at 4.7kHz
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- low frequency zero at 2.6Hz but non-minimum phase (not explained).
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Small viscous damping material in the cross blade flexures made the zero minimum phase again.
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<a id="org67e505c"></a>
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{{< figure src="/ox-hugo/spanos95_iff_plant.png" caption="Figure 2: Experimentally measured transfer function from voice coil drive voltage to collocated load cell output voltage" >}}
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The controller used consisted of:
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- second order low pass filter to gain stabilize the plant at high frequencies and provide steep roll-off
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- first order lead filter to provide adequate phase margin at the high frequency crossover
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- first order lag filter to provide adequate phase margin at the low frequency crossover
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- a first order high pass filter to attenuate the excess gain resulting from the low frequency zero
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The results in terms of transmissibility are shown in Figure [3](#orgf128817).
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<a id="orgf128817"></a>
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{{< figure src="/ox-hugo/spanos95_results.png" caption="Figure 3: Experimentally measured Frobenius norm of the 6-axis transmissibility" >}}
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# Bibliography
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<a id="spanos95_soft_activ_vibrat_isolat"></a>Spanos, J., Rahman, Z., & Blackwood, G., *A soft 6-axis active vibration isolator*, In , Proceedings of 1995 American Control Conference - ACC'95 (pp. ) (1995). : . [↩](#a48f6708d087625a42ca2375407a2bc4)
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