Update Content - 2020-10-15
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@@ -4,7 +4,7 @@ author = ["Thomas Dehaeze"]
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### Backlinks {#backlinks}
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Backlinks:
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- [Identification and decoupling control of flexure jointed hexapods]({{< relref "chen00_ident_decoup_contr_flexur_joint_hexap" >}})
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@@ -12,7 +12,7 @@ Tags
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: [Stewart Platforms]({{< relref "stewart_platforms" >}}), [Flexible Joints]({{< relref "flexible_joints" >}})
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Reference
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: ([McInroy 1999](#org5efb28a))
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: ([McInroy 1999](#orgfc7fa52))
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Author(s)
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: McInroy, J.
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@@ -20,7 +20,7 @@ Author(s)
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Year
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: 1999
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This conference paper has been further published in a journal as a short note ([McInroy 2002](#org4990a96)).
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This conference paper has been further published in a journal as a short note ([McInroy 2002](#org7752c60)).
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## Abstract {#abstract}
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@@ -42,22 +42,22 @@ The actuators for FJHs can be divided into two categories:
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1. soft (voice coil), which employs a spring flexure mount
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2. hard (piezoceramic or magnetostrictive), which employs a compressive load spring.
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<a id="org5279430"></a>
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<a id="orgd835559"></a>
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{{< figure src="/ox-hugo/mcinroy99_general_hexapod.png" caption="Figure 1: A general Stewart Platform" >}}
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Since both actuator types employ force production in parallel with a spring, they can both be modeled as shown in Figure [2](#org6b356c7).
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Since both actuator types employ force production in parallel with a spring, they can both be modeled as shown in Figure [2](#org26f1840).
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In order to provide low frequency passive vibration isolation, the hard actuators are sometimes placed in series with additional passive springs.
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<a id="org6b356c7"></a>
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<a id="org26f1840"></a>
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{{< figure src="/ox-hugo/mcinroy99_strut_model.png" caption="Figure 2: The dynamics of the i'th strut. A parallel spring, damper and actuator drives the moving mass of the strut and a payload" >}}
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<a id="table--tab:mcinroy99-strut-model"></a>
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<div class="table-caption">
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<span class="table-number"><a href="#table--tab:mcinroy99-strut-model">Table 1</a></span>:
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Definition of quantities on Figure <a href="#org6b356c7">2</a>
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Definition of quantities on Figure <a href="#org26f1840">2</a>
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</div>
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| **Symbol** | **Meaning** |
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@@ -74,11 +74,11 @@ In order to provide low frequency passive vibration isolation, the hard actuator
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| \\(v\_i = p\_i - q\_i\\) | vector pointing from the bottom to the top |
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| \\(\hat{u}\_i = v\_i/l\_i\\) | unit direction of the strut |
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It is here supposed that \\(f\_{p\_i}\\) is predominantly in the strut direction (explained in ([McInroy 2002](#org4990a96))).
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It is here supposed that \\(f\_{p\_i}\\) is predominantly in the strut direction (explained in ([McInroy 2002](#org7752c60))).
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This is a good approximation unless the spherical joints and extremely stiff or massive, of high inertia struts are used.
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This allows to reduce considerably the complexity of the model.
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From Figure [2](#org6b356c7) (b), forces along the strut direction are summed to yield (projected along the strut direction, hence the \\(\hat{u}\_i^T\\) term):
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From Figure [2](#org26f1840) (b), forces along the strut direction are summed to yield (projected along the strut direction, hence the \\(\hat{u}\_i^T\\) term):
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\begin{equation}
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m\_i \hat{u}\_i^T \ddot{p}\_i = f\_{m\_i} - f\_{p\_i} - m\_i \hat{u}\_i^Tg - k\_i(l\_i - l\_{r\_i}) - b\_i \dot{l}\_i
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@@ -168,6 +168,6 @@ In the next section, a connection between the two will be found to complete the
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## Bibliography {#bibliography}
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<a id="org5efb28a"></a>McInroy, J.E. 1999. “Dynamic Modeling of Flexure Jointed Hexapods for Control Purposes.” In _Proceedings of the 1999 IEEE International Conference on Control Applications (Cat. No.99CH36328)_, nil. <https://doi.org/10.1109/cca.1999.806694>.
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<a id="orgfc7fa52"></a>McInroy, J.E. 1999. “Dynamic Modeling of Flexure Jointed Hexapods for Control Purposes.” In _Proceedings of the 1999 IEEE International Conference on Control Applications (Cat. No.99CH36328)_, nil. <https://doi.org/10.1109/cca.1999.806694>.
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<a id="org4990a96"></a>———. 2002. “Modeling and Design of Flexure Jointed Stewart Platforms for Control Purposes.” _IEEE/ASME Transactions on Mechatronics_ 7 (1):95–99. <https://doi.org/10.1109/3516.990892>.
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<a id="org7752c60"></a>———. 2002. “Modeling and Design of Flexure Jointed Stewart Platforms for Control Purposes.” _IEEE/ASME Transactions on Mechatronics_ 7 (1):95–99. <https://doi.org/10.1109/3516.990892>.
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