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Edits to last parts of the intro for better wording.
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moorepants committed Jun 5, 2024
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37 changes: 18 additions & 19 deletions main.tex
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Expand Up @@ -49,8 +49,9 @@ \section{Introduction}
\begin{figure}
\centering
\includegraphics[width=70mm]{figures/balance-assist-bicycle.jpg}
\caption{Balance assist bicycle prototype with steer motor and data
acquisition and control electronics mounted in the rear rack.}
\caption{Balance assist bicycle prototype with electric motor in the steering
column and data acquisition and control electronics mounted in the rear
rack.}
\label{fig:balance-assist-bicycle}
\end{figure}

Expand Down Expand Up @@ -118,37 +119,35 @@ \section{Introduction}

If the steer torque is the sum of the (h)uman applied torque and the (m)otor
applied torque \(T_\delta = T_\delta^\textrm{h} + T_\delta^\textrm{m}\),
\(\mathbf{B} = \begin{bmatrix} \mathbf{B}_\phi \quad \mathbf{B}_\delta
\(\mathbf{B} = \begin{bmatrix} \vec{B}_\phi \quad \vec{B}_\delta
\end{bmatrix}\), and \(T_\delta^\textrm{m} = -k_{\dot{\phi}} \dot{\phi}\) then
the human controlled plant takes the form:

\begin{align}
\dot{\vec{x}} = \left(\mathbf{A} -
\mathbf{B}_\delta
\vec{B}_\delta
\left[0 \quad k_{\dot{\phi}} \quad 0 \quad 0\right]
\right)
\vec{x} + \mathbf{B} \begin{bmatrix} T_{\phi} \\ T_\delta^\textrm{h} \end{bmatrix}
\end{align}

The state matrix \(\mathbf{A}\) and input matrix \(\mathbf{B}\) are both
functions of the equilibrium speed \(v\) and \(k_{\dot{\phi}}\) can be selected
such that the eigenvalues of \(\left(\mathbf{A} - \mathbf{B}_\delta\left[0
\quad k_{\dot{\phi}} \quad 0 \quad 0\right] \right)\) have negative real parts
for \(v_{weave} < v < v_{capsize}\). With gain scheduling with respect to
\(v\), the speed range where the bicycle is stable can be maximized within any
physical actuator magnitude and bandwidth limits. \citet{Schwab2008}
elaborates on some of the possibilities in scheduling the gains for such a
controller on this model.

\todo[inline]{I'm not consistent with the arrow being a vector for $B_\delta$}
such that the eigenvalues of \(\left(\mathbf{A} - \vec{B}_\delta\left[0 \quad
k_{\dot{\phi}} \quad 0 \quad 0\right] \right)\) have negative real parts for
\(v_{min} < v < v_{capsize}\). With gain scheduling with respect to \(v\), the
speed range where the bicycle is stable can be maximized within any physical
actuator magnitude and bandwidth limits. \citet{Schwab2008} elaborates on some
of the possibilities in scheduling the gains for such a controller and shows
that a linear scheduling with respect to speed can give satisfactory stability.

In this paper, we test whether a gain scheduled steer motor controlled bicycle
that is stable at a low speed range when riderless assists in balancing by
investigating whether it is beneficial in preventing the rider from falling.
To do this, we apply varying magnitude mechanical perturbations to the
handlebars while the rider is balancing the bicycle on a treadmill and then
assess the rider's probability of falling with the balance assist steer motor
system on and off.
that is stable in a large low speed range (when riderless) assists the rider in
balancing by investigating whether it is beneficial in preventing falling. To
do this, we apply varying magnitude mechanical perturbations to the handlebars
while the rider is balancing the bicycle on a treadmill and then assess the
rider's probability of falling with the balance assist steer motor system on
and off.

\todo{Talk about the types of real life perturbations an how our perturbation
mimics it.}
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