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@ -331,7 +331,6 @@ It is found that the complex dynamics is due to a misalignment between the flexi
* Mounting Procedure * Mounting Procedure
<<sec:test_struts_mounting>> <<sec:test_struts_mounting>>
** Introduction :ignore:
A mounting bench was developed to ensure: A mounting bench was developed to ensure:
- Good coaxial alignment between the interfaces (cylinders) of the flexible joints. - Good coaxial alignment between the interfaces (cylinders) of the flexible joints.
@ -340,13 +339,11 @@ A mounting bench was developed to ensure:
- Precise alignment of the APA with the two flexible joints - Precise alignment of the APA with the two flexible joints
- Reproducible and consistent assembly between all struts - Reproducible and consistent assembly between all struts
** Mounting Bench
A CAD view of the mounting bench is shown in Figure ref:fig:test_struts_mounting_bench_first_concept. A CAD view of the mounting bench is shown in Figure ref:fig:test_struts_mounting_bench_first_concept.
It consists of a "main frame" (Figure ref:fig:test_struts_mounting_step_0) precisely machined to ensure both correct strut length and strut coaxiality. It consists of a "main frame" (Figure ref:fig:test_struts_mounting_step_0) precisely machined to ensure both correct strut length and strut coaxiality.
The coaxiality is ensured by good flatness (specified at $20\,\mu m$) between surfaces A and B and between surfaces C and D. The coaxiality is ensured by good flatness (specified at $20\,\mu m$) between surfaces A and B and between surfaces C and D.
Such flatness was checked using a Faro arm[fn:1] (see Figure ref:fig:test_struts_check_dimensions_bench) and was found to comply with the requirements. Such flatness was checked using a FARO arm[fn:1] (see Figure ref:fig:test_struts_check_dimensions_bench) and was found to comply with the requirements.
The strut length (defined by the distance between the rotation points of the two flexible joints) was ensured by using precisely machines dowel holes. The strut length (defined by the distance between the rotation points of the two flexible joints) was ensured by using precisely machined dowel holes.
#+name: fig:test_struts_mounting #+name: fig:test_struts_mounting
@ -413,8 +410,6 @@ These "sleeves" have one dowel groove (that are fitted to the dowel holes shown
#+end_subfigure #+end_subfigure
#+end_figure #+end_figure
** Mounting Procedure
The "sleeves" were mounted to the main element as shown in Figure ref:fig:test_struts_mounting_step_0. The "sleeves" were mounted to the main element as shown in Figure ref:fig:test_struts_mounting_step_0.
The left sleeve has a thigh fit such that its orientation is fixed (it is roughly aligned horizontally), while the right sleeve has a loose fit such that it can rotate (it will get the same orientation as the fixed one when tightening the screws). The left sleeve has a thigh fit such that its orientation is fixed (it is roughly aligned horizontally), while the right sleeve has a loose fit such that it can rotate (it will get the same orientation as the fixed one when tightening the screws).
@ -464,11 +459,10 @@ Thanks to this mounting procedure, the coaxiality and length between the two fle
:header-args:matlab+: :tangle matlab/test_struts_1_flexible_modes.m :header-args:matlab+: :tangle matlab/test_struts_1_flexible_modes.m
:END: :END:
<<sec:test_struts_flexible_modes>> <<sec:test_struts_flexible_modes>>
** Introduction
A Finite Element Model[fn:3] of the struts is developed and is used to estimate the flexible modes. A Finite Element Model[fn:3] of the struts is developed and is used to estimate the flexible modes.
The inertia of the encoder (estimated at $15\,g$) is considered. The inertia of the encoder (estimated at $15\,g$) is considered.
The two cylindrical interfaces were fixed, and the first three flexible modes were computed. The two cylindrical interfaces were fixed (boundary conditions), and the first three flexible modes were computed.
The mode shapes are displayed in Figure ref:fig:test_struts_mode_shapes: an "X-bending" mode at 189Hz, a "Y-bending" mode at 285Hz and a "Z-torsion" mode at 400Hz. The mode shapes are displayed in Figure ref:fig:test_struts_mode_shapes: an "X-bending" mode at 189Hz, a "Y-bending" mode at 285Hz and a "Z-torsion" mode at 400Hz.
#+name: fig:test_struts_mode_shapes #+name: fig:test_struts_mode_shapes
@ -495,7 +489,6 @@ The mode shapes are displayed in Figure ref:fig:test_struts_mode_shapes: an "X-b
#+end_subfigure #+end_subfigure
#+end_figure #+end_figure
** Matlab Init :noexport:ignore:
#+begin_src matlab :tangle no :exports none :results silent :noweb yes :var current_dir=(file-name-directory buffer-file-name) #+begin_src matlab :tangle no :exports none :results silent :noweb yes :var current_dir=(file-name-directory buffer-file-name)
<<matlab-dir>> <<matlab-dir>>
#+end_src #+end_src
@ -516,8 +509,6 @@ The mode shapes are displayed in Figure ref:fig:test_struts_mode_shapes: an "X-b
<<m-init-other>> <<m-init-other>>
#+end_src #+end_src
** Measurement Setup
To experimentally measure these mode shapes, a Laser vibrometer[fn:7] was used. To experimentally measure these mode shapes, a Laser vibrometer[fn:7] was used.
It measures the difference of motion between two beam path (red points in Figure ref:fig:test_struts_meas_modes). It measures the difference of motion between two beam path (red points in Figure ref:fig:test_struts_meas_modes).
The strut is then excited by an instrumented hammer, and the transfer function from the hammer to the measured rotation is computed. The strut is then excited by an instrumented hammer, and the transfer function from the hammer to the measured rotation is computed.
@ -550,7 +541,6 @@ These tests were performed with and without the encoder being fixed to the strut
#+end_subfigure #+end_subfigure
#+end_figure #+end_figure
** Measured results
The obtained frequency response functions for the three configurations (X-bending, Y-bending and Z-torsion) are shown in Figure ref:fig:test_struts_spur_res_frf_no_enc when the encoder is not fixed to the strut and in Figure ref:fig:test_struts_spur_res_frf_enc when the encoder is fixed to the strut. The obtained frequency response functions for the three configurations (X-bending, Y-bending and Z-torsion) are shown in Figure ref:fig:test_struts_spur_res_frf_no_enc when the encoder is not fixed to the strut and in Figure ref:fig:test_struts_spur_res_frf_enc when the encoder is fixed to the strut.
#+begin_src matlab :exports none #+begin_src matlab :exports none
@ -1875,6 +1865,9 @@ exportFig('figs/test_struts_comp_enc_frf_realign.pdf', 'width', 'wide', 'height'
[[file:figs/test_struts_comp_enc_frf_realign.png]] [[file:figs/test_struts_comp_enc_frf_realign.png]]
* Conclusion * Conclusion
:PROPERTIES:
:UNNUMBERED: t
:END:
<<sec:test_struts_conclusion>> <<sec:test_struts_conclusion>>
The Hano-Hexapod struts are a key component of the developed acrfull:nass. The Hano-Hexapod struts are a key component of the developed acrfull:nass.
@ -2294,4 +2287,4 @@ actuator.cs = args.cs; % Damping of one stack [N/m]
[fn:4] Two fiber intereferometers were used: an IDS3010 from Attocube and a quDIS from QuTools [fn:4] Two fiber intereferometers were used: an IDS3010 from Attocube and a quDIS from QuTools
[fn:3] Using Ansys\textsuperscript{\textregistered}. Flexible Joints and APA Shell are made of a stainless steel allow called /17-4 PH/. Encoder and ruler support material is aluminium. [fn:3] Using Ansys\textsuperscript{\textregistered}. Flexible Joints and APA Shell are made of a stainless steel allow called /17-4 PH/. Encoder and ruler support material is aluminium.
[fn:2] Heidenhain MT25, specified accuracy of $\pm 0.5\,\mu m$ [fn:2] Heidenhain MT25, specified accuracy of $\pm 0.5\,\mu m$
[fn:1] Faro Arm Platinum 4ft, specified accuracy of $\pm 13\mu m$ [fn:1] FARO Arm Platinum 4ft, specified accuracy of $\pm 13\mu m$

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test-bench-struts.tex
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@ -1,4 +1,4 @@
% Created 2024-10-25 Fri 17:22 % Created 2024-11-18 Mon 10:26
% Intended LaTeX compiler: pdflatex % Intended LaTeX compiler: pdflatex
\documentclass[a4paper, 10pt, DIV=12, parskip=full, bibliography=totoc]{scrreprt} \documentclass[a4paper, 10pt, DIV=12, parskip=full, bibliography=totoc]{scrreprt}
@ -53,6 +53,7 @@ It is found that the complex dynamics is due to a misalignment between the flexi
\chapter{Mounting Procedure} \chapter{Mounting Procedure}
\label{sec:test_struts_mounting} \label{sec:test_struts_mounting}
A mounting bench was developed to ensure: A mounting bench was developed to ensure:
\begin{itemize} \begin{itemize}
\item Good coaxial alignment between the interfaces (cylinders) of the flexible joints. \item Good coaxial alignment between the interfaces (cylinders) of the flexible joints.
@ -61,13 +62,12 @@ This is important not to loose to much angular stroke during their mounting into
\item Precise alignment of the APA with the two flexible joints \item Precise alignment of the APA with the two flexible joints
\item Reproducible and consistent assembly between all struts \item Reproducible and consistent assembly between all struts
\end{itemize} \end{itemize}
\section{Mounting Bench}
A CAD view of the mounting bench is shown in Figure \ref{fig:test_struts_mounting_bench_first_concept}. A CAD view of the mounting bench is shown in Figure \ref{fig:test_struts_mounting_bench_first_concept}.
It consists of a ``main frame'' (Figure \ref{fig:test_struts_mounting_step_0}) precisely machined to ensure both correct strut length and strut coaxiality. It consists of a ``main frame'' (Figure \ref{fig:test_struts_mounting_step_0}) precisely machined to ensure both correct strut length and strut coaxiality.
The coaxiality is ensured by good flatness (specified at \(20\,\mu m\)) between surfaces A and B and between surfaces C and D. The coaxiality is ensured by good flatness (specified at \(20\,\mu m\)) between surfaces A and B and between surfaces C and D.
Such flatness was checked using a Faro arm\footnote{Faro Arm Platinum 4ft, specified accuracy of \(\pm 13\mu m\)} (see Figure \ref{fig:test_struts_check_dimensions_bench}) and was found to comply with the requirements. Such flatness was checked using a FARO arm\footnote{FARO Arm Platinum 4ft, specified accuracy of \(\pm 13\mu m\)} (see Figure \ref{fig:test_struts_check_dimensions_bench}) and was found to comply with the requirements.
The strut length (defined by the distance between the rotation points of the two flexible joints) was ensured by using precisely machines dowel holes. The strut length (defined by the distance between the rotation points of the two flexible joints) was ensured by using precisely machined dowel holes.
\begin{figure}[htbp] \begin{figure}[htbp]
@ -128,8 +128,6 @@ These ``sleeves'' have one dowel groove (that are fitted to the dowel holes show
\caption{\label{fig:test_struts_cylindrical_mounting}Preparation of the flexible joints by fixing them in their cylindrical ``sleeve''} \caption{\label{fig:test_struts_cylindrical_mounting}Preparation of the flexible joints by fixing them in their cylindrical ``sleeve''}
\end{figure} \end{figure}
\section{Mounting Procedure}
The ``sleeves'' were mounted to the main element as shown in Figure \ref{fig:test_struts_mounting_step_0}. The ``sleeves'' were mounted to the main element as shown in Figure \ref{fig:test_struts_mounting_step_0}.
The left sleeve has a thigh fit such that its orientation is fixed (it is roughly aligned horizontally), while the right sleeve has a loose fit such that it can rotate (it will get the same orientation as the fixed one when tightening the screws). The left sleeve has a thigh fit such that its orientation is fixed (it is roughly aligned horizontally), while the right sleeve has a loose fit such that it can rotate (it will get the same orientation as the fixed one when tightening the screws).
@ -174,11 +172,10 @@ Thanks to this mounting procedure, the coaxiality and length between the two fle
\chapter{Measurement of flexible modes} \chapter{Measurement of flexible modes}
\label{sec:test_struts_flexible_modes} \label{sec:test_struts_flexible_modes}
\section{Introduction}
A Finite Element Model\footnote{Using Ansys\textsuperscript{\textregistered}. Flexible Joints and APA Shell are made of a stainless steel allow called \emph{17-4 PH}. Encoder and ruler support material is aluminium.} of the struts is developed and is used to estimate the flexible modes. A Finite Element Model\footnote{Using Ansys\textsuperscript{\textregistered}. Flexible Joints and APA Shell are made of a stainless steel allow called \emph{17-4 PH}. Encoder and ruler support material is aluminium.} of the struts is developed and is used to estimate the flexible modes.
The inertia of the encoder (estimated at \(15\,g\)) is considered. The inertia of the encoder (estimated at \(15\,g\)) is considered.
The two cylindrical interfaces were fixed, and the first three flexible modes were computed. The two cylindrical interfaces were fixed (boundary conditions), and the first three flexible modes were computed.
The mode shapes are displayed in Figure \ref{fig:test_struts_mode_shapes}: an ``X-bending'' mode at 189Hz, a ``Y-bending'' mode at 285Hz and a ``Z-torsion'' mode at 400Hz. The mode shapes are displayed in Figure \ref{fig:test_struts_mode_shapes}: an ``X-bending'' mode at 189Hz, a ``Y-bending'' mode at 285Hz and a ``Z-torsion'' mode at 400Hz.
\begin{figure}[htbp] \begin{figure}[htbp]
@ -203,8 +200,6 @@ The mode shapes are displayed in Figure \ref{fig:test_struts_mode_shapes}: an ``
\caption{\label{fig:test_struts_mode_shapes}Spurious resonances of the struts estimated from a Finite Element Model} \caption{\label{fig:test_struts_mode_shapes}Spurious resonances of the struts estimated from a Finite Element Model}
\end{figure} \end{figure}
\section{Measurement Setup}
To experimentally measure these mode shapes, a Laser vibrometer\footnote{OFV-3001 controller and OFV512 sensor head from Polytec} was used. To experimentally measure these mode shapes, a Laser vibrometer\footnote{OFV-3001 controller and OFV512 sensor head from Polytec} was used.
It measures the difference of motion between two beam path (red points in Figure \ref{fig:test_struts_meas_modes}). It measures the difference of motion between two beam path (red points in Figure \ref{fig:test_struts_meas_modes}).
The strut is then excited by an instrumented hammer, and the transfer function from the hammer to the measured rotation is computed. The strut is then excited by an instrumented hammer, and the transfer function from the hammer to the measured rotation is computed.
@ -235,7 +230,6 @@ These tests were performed with and without the encoder being fixed to the strut
\caption{\label{fig:test_struts_meas_modes}Measurement of strut flexible modes} \caption{\label{fig:test_struts_meas_modes}Measurement of strut flexible modes}
\end{figure} \end{figure}
\section{Measured results}
The obtained frequency response functions for the three configurations (X-bending, Y-bending and Z-torsion) are shown in Figure \ref{fig:test_struts_spur_res_frf_no_enc} when the encoder is not fixed to the strut and in Figure \ref{fig:test_struts_spur_res_frf_enc} when the encoder is fixed to the strut. The obtained frequency response functions for the three configurations (X-bending, Y-bending and Z-torsion) are shown in Figure \ref{fig:test_struts_spur_res_frf_no_enc} when the encoder is not fixed to the strut and in Figure \ref{fig:test_struts_spur_res_frf_enc} when the encoder is fixed to the strut.
\begin{figure}[htbp] \begin{figure}[htbp]
@ -589,7 +583,7 @@ Therefore, fixing the encoders to the nano-hexapod plates instead may be an inte
\caption{\label{fig:test_struts_comp_enc_frf_realign}Comparison of the dynamics from \(u\) to \(d_e\) before and after proper alignment using the dowel pins} \caption{\label{fig:test_struts_comp_enc_frf_realign}Comparison of the dynamics from \(u\) to \(d_e\) before and after proper alignment using the dowel pins}
\end{figure} \end{figure}
\chapter{Conclusion} \chapter*{Conclusion}
\label{sec:test_struts_conclusion} \label{sec:test_struts_conclusion}
The Hano-Hexapod struts are a key component of the developed \acrfull{nass}. The Hano-Hexapod struts are a key component of the developed \acrfull{nass}.