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Article_Scientifique/lowtech.tex
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@ -1,7 +1,7 @@
\section{Hardware-Based Six-Step Commutation Controller} \section{Hardware-Based Six-Step Commutation Controller}
\label{sec:sixstep} \label{sec:sixstep}
The basis of this section is the replacement of components who are highly complex, technical and/or are dependant on global supply chains to manufacture. An additional goal is, as for the preceding section, to make a repairable, reliable and manufacturable circuit, this time using these more basic components, based on open-source principles. The controller needs to be performant enough to drive one of the two electric motors used on the LaMAD (La Manufacture Autonome Décentralisée) bicycle cargo trailer. %ref moteur qu'utilise lamad The basis of this section is the replacement of components who are highly complex, technical and/or are dependant on global supply chains to manufacture. An additional goal is, as for the preceding section, to make a repairable, reliable and manufacturable circuit, this time using these more basic components, based on open-source principles. The controller needs to be performant enough to drive one of the two electric motors used on the LaMAD (La Manufacture Autonome Décentralisée) bicycle cargo trailer.\cite{noauthor_ddf-39_nodate}
\subsection{Constraints} \subsection{Constraints}
The electric motors used are supplied using 36/48 Volts at 1000 W. This means that the six-step chopper transistors need to be able to supply up to 28 Amperes of current. This is a lot, considering our restrictions. Additionally, the heat will need to be managed, which may be an even bigger challenge than the current. The electric motors used are supplied using 36/48 Volts at 1000 W. This means that the six-step chopper transistors need to be able to supply up to 28 Amperes of current. This is a lot, considering our restrictions. Additionally, the heat will need to be managed, which may be an even bigger challenge than the current.
@ -21,7 +21,7 @@ but this is a very recent technology, and none of the big material players in Ga
The LAAS semiconductor lab was deemed less reachable and more technologically advanced than the AIME semiconductor lab, as we were told they mostly did research on carbon nanotubes and other fancy semiconductor materials. We therefore chose not to contact the LAAS, and The LAAS semiconductor lab was deemed less reachable and more technologically advanced than the AIME semiconductor lab, as we were told they mostly did research on carbon nanotubes and other fancy semiconductor materials. We therefore chose not to contact the LAAS, and
The AIME is a small research lab located on our campus. Their capabilities and projects were not publicly available, so we decided to contact them. We met two researchers Reasmey Tan and Jean-Baptiste Lincelles to enquire about the manufacturability of certain components, and eventual costs. The AIME specialises in logic circuits, and has not developed any power components at least a decade. Therefore, the research teams have not maintained any know-how in power semiconductors. However, they were very interested in developing this field in their lab, and came with a proposal to start, based on their existing knowledge. Here are some of AIME's capabilities and prices: The AIME is a small research lab located on our campus. Their capabilities and projects were not publicly available, so we decided to contact them. We met two researchers Mr. Tan and Mr. Lincelles to enquire about the manufacturability of certain components, and eventual costs. The AIME specialises in logic circuits, and has not developed any power components at least a decade. Therefore, the research teams have not maintained any know-how in power semiconductors. However, they were very interested in developing this field in their lab, and came with a proposal to start, based on their existing knowledge. Here are some of AIME's capabilities and prices:
\begin{table}[htbp] \begin{table}[htbp]
\caption{AIME capabilities} \caption{AIME capabilities}
@ -29,7 +29,7 @@ The AIME is a small research lab located on our campus. Their capabilities and p
\centering \centering
\begin{tabular}{lcc} \begin{tabular}{lcc}
\toprule \toprule
\textbf{Proposal or capability} & \textbf{Value, if relevant} & \textbf{Price, if relevant} \\ \textbf{Proposal or capability} & \textbf{Value} & \textbf{Price, if relevant} \\
\midrule \midrule
Silicon wafer & 2'' ($\sim$50mm) & 10 € \\ Silicon wafer & 2'' ($\sim$50mm) & 10 € \\
Epitaxial "fancy" wafer & 2'' ($\sim$50mm) & 100-200 € \\ Epitaxial "fancy" wafer & 2'' ($\sim$50mm) & 100-200 € \\
@ -41,7 +41,7 @@ The AIME is a small research lab located on our campus. Their capabilities and p
\end{tabular} \end{tabular}
\end{table} \end{table}
The proposed project was based on their logic transistors, scaled up not in size, but in number. As seen in the table \ref{tab:AIME_capabilities}, one of their small logic transistors has a resistance of: The proposed project was based on their logic transistors, scaled up not in size, but in number. As seen in the table above, one of their small logic transistors has a resistance of:
\begin{equation} \begin{equation}
R_{DS_{on}} \approx 1\ k\Omega R_{DS_{on}} \approx 1\ k\Omega
@ -61,7 +61,7 @@ Which is extremely unrealistic for a small component and needs to be investigate
\centering \centering
\begin{tabular}{lcc} \begin{tabular}{lcc}
\toprule \toprule
\textbf{Proposal or capability} & \textbf{Value, if relevant} & \textbf{Price, if relevant} \\ \textbf{Proposal or capability} & \textbf{Value} & \textbf{Price, if relevant} \\
\midrule \midrule
Transistor count & $\sim$400 000 & \\ Transistor count & $\sim$400 000 & \\
Die size & 1-2 cm$^2$ & \\ Die size & 1-2 cm$^2$ & \\
@ -74,24 +74,29 @@ Dies per set of masks & $>$ 1000 dies & \\
\end{tabular} \end{tabular}
\end{table} \end{table}
These costs are much larger than what we have for this project, but are not insurmountable for a department like the GEI. This project also needs a lot of time or more people to be made, more than what we have at our disposal. The researchers were very interested in collaborating on such a project in the future, and considered it very strongly as a replacement for the current AIME project for the 5th year PTP Energie students (currently a CO2 sensor), with GEI's backing and funding. These costs are much larger than what we have for this project, but are not insurmountable for a department like the GEI. This project also needs a lot of time or more people to be made, more than what we have at our disposal. The researchers were very interested in collaborating on such a project in the future, and considered it very strongly as a replacement for the current AIME project for the 5th year PTP Energie students at INSA Toulouse (currently a CO2 sensor), with GEI's backing and funding.
The complexity of manufacturing power transistors made us go for the strategy of choosing readily available and cheap components.
\subsection{Replacing an IC} \subsection{Replacing an IC}
Replacing the IC of a motor controller requires using traditional logic gates. This approach can be done in several methods Replacing the IC of a motor controller requires using traditional logic gates. This approach can be done in several methods. The AIME would easily be able to produce such a circuit at a relatively low cost, but this is neither easily accessible nor repairable. We therefore needed to use another form of logic gates. The simplest form of gates are diode gates, which use two diodes to make either an AND or OR-gate. They cannot make NOT-gates, which need a CMOS-cell (two transistors). We continued by simulating this in LTSpice XVII, based on Mr. Rocacher's circuits. This circuit ended up needing 4 AND-gates, 2 OR-gates and 1 NOT-gate (CMOS cell) per phase, with additional transistors to compensate for voltage lost at the diodes, as well as one additional OR-gate. The total would be like this :
\subsection{Power components} \begin{table}[htbp]
\caption{Minimum number of diodes and transistors needed}
\label{tab:decompte}
\centering
\begin{tabular}{lccc}
\toprule
\textbf{Gate} & Number of gates & \textbf{Number of diodes} & \textbf{Number of transistors} \\
\midrule
AND & 12 & 24 & 0 \\
OR & 7 & 14 & 0 \\
NOT & 3 & 0 & 6\\
\bottomrule
Total & & 38 & 6
\end{tabular}
\end{table}
This is a considerable number of diodes and transistors, but would make the circuit easily repairable and replaceable.
\subsection{Clock}
To calculate the maximum rotation speed, we take the worst conditions of the motor used in the MAD cargo bike; 50 km/h\footnote{http://www.mxusebikekit.com/pro\_info.asp?Pid=25} with a 50 cm wheel\footnote{http://www.mxusebikekit.com/pro\_info.asp?Pid=25}\footnote{https://veloma.org/2022/10/05/la-charrette-version-montagne-ou-comment-transporter-250kg-a-velo-par-monts-et-par-vaux/} (not measured, assumed from the images and the motor specifications).
\begin{equation*}
\omega=\frac{v}{\pi d}=\frac{50\cdot 10^3m/h\cdot\frac{1}{60}h/min}{3,14\cdot 50\cdot 10^{-2}m}=530\ rpm
\end{equation*}
The motor being a three-phase brushless motor, the switching speed needs to be
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