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@@ -1,22 +1,187 @@ # Introduction -# Problem statement +\<inleiding iemand?\> -The following is the original project description (translated to English): +# Problem statement -> I would like to bring to market a vehicle that can drive independently from A -> to B. The vehicle must take into account traffic rules, road signs, traffic -> lights, etc. Research is being conducted using a small cart, the Pololu Zumo -> 32U4, on which a camera module Nicla Vision is mounted. The aim is to -> investigate the most appropriate method of recognizing the road, traffic -> signs and traffic lights. This should be demonstrated with a proof of -> concept. The cart does not need to drive fast, so the image processing does -> not need to be very fast. Assume one frame per second (or faster). +The following is the original project description (translated to English). +References have been added in superscript that link to requirements set in +section \ref{specifications}. + +> I would like to bring to market a vehicle that can drive +> independently\req{autonomous} from A to B. The vehicle must take into account +> traffic rules\req{traffic-rules}, road signs\req{signs}, traffic +> lights\req{traffic-lights}, etc. Research is being conducted using a small +> cart, the Pololu Zumo 32U4\req{zumo}, on which a camera module Nicla +> Vision\req{nicla} is mounted. The aim is to investigate the most appropriate +> method of recognizing the road, traffic signs and traffic lights. This should +> be demonstrated with a proof of concept. The cart does not need to drive +> fast\req{drspeed}, so the image processing\req{mvision} does not need to be +> very fast. Assume one frame per second (or faster)\req{imspeed}. # Specifications +The following is a list of specifications derived from the original project +description in section \ref{problem-statement}. + +\begin{enumerate} + \item \label{req:autonomous} + The vehicle is autonomous + \item + The vehicle can detect how its positioned and orientated relative to a road + \item \label{req:traffic-rules} + The vehicle conforms to the following set of traffic rules + \begin{enumerate} + \item Driving when not on a road is not allowed + \item The vehicle can follow a road by steering itself accordingly + \item Driving off the road is only allowed when necessary for the camera to + keep seeing the road + \end{enumerate} + \item \label{req:traffic-lights} + The vehicle handles traffic lights in the following way + \begin{enumerate} + \item Stop at a red traffic light + \item Speed up at an orange traffic light + \item Continue driving normally at a green traffic light + \end{enumerate} + \item \label{req:signs} + The vehicle acts on traffic signs in the following way + \begin{enumerate} + \item Stop at a stop sign, and continue driving after a few seconds + \item Turn left at a left sign + \item Turn right at a right sign + \item Slow down at a low speed limit sign + \item Speed up to normal speed at a high speed limit sign + \end{enumerate} + \item \label{req:zumo} + The vehicle used is a Pololu Zumo 32U4 + \item \label{req:nicla} + The camera module used is an Arduino Nicla Vision + \item \label{req:mvision} + Computer vision / image processing is used as the only input + \item \label{req:drspeed} + There is no minimum speed the car has to drive at + \item \label{req:imspeed} + The image processing pipeline runs at 1 frame per second or higher + \item + The Zumo displays the name of the last detected sign on it's OLED display +\end{enumerate} + # Architecture +## Overview + + + +Figure \ref{fig:architecture-level-0} shows the hardware used in this project. +Both the Pololu Zumo 32U4 (referred to as just "Zumo"), and the Arduino Nicla +Vision ("Nicla") have additional sensors and/or outputs on-board, but are +unused. + +## Distribution of features + +Because creating a software architecture that does all machine vision-related +tasks on the Nicla, and all driving related tasks on the Zumo would create +significant overhead, and because the microcontroller on the Zumo is +significantly harder to debug than the Nicla, a monolithic architecture was +chosen. In this architecture, both the detection of 'traffic objects' and the +decisionmaking on how to handle each object is done on the Nicla board. + +Figure \ref{fig:architecture-level-0} shows that a bidirectional communication +line exists between the Zumo and Nicla. This line is only used to send control +commands to the Zumo. Section \ref{niclazumo-communication-protocol} describes +which commands are sent over these lines. + +## Nicla/Zumo communication protocol + +The communication protocol used to control the Zumo from the Nicla uses UART to +send ranged numbers in a single byte. Table \ref{tab:protocol-ranges} shows +which number ranges correspond to which controls. + +\begin{table} +\centering +\begin{tabular}{rl} +\toprule +\textbf{Description} & \textbf{Range (inclusive)}\\ +\midrule +(unused) & \texttt{0x00}\\ +Signs & \texttt{0x01} - \texttt{0x0f}\\ +Speed & \texttt{0x10} - \texttt{0x1f}\\ +Steering & \texttt{0x20} - \texttt{0xff}\\ +\bottomrule +\end{tabular} +\caption{Protocol command ranges} +\label{tab:protocol-ranges} +\end{table} + +### Signs + +The Zumo stores the last sign received, and displays it's name on the OLED +display using the lookup table in table \ref{tab:protocol-signs}. The sign ID +is calculated by subtracting the start offset of the sign command range from +the command as shown in table \ref{tab:protocol-ranges}. + +\begin{table} +\centering +\begin{tabular}{ll} +\toprule +\textbf{ID} & \textbf{Name}\\ +\midrule +\texttt{0x00} & (clear sign)\\ +\texttt{0x01} & Stop sign\\ +\texttt{0x02} & Turn left\\ +\texttt{0x03} & Turn right\\ +\texttt{0x04} & Low speed limit\\ +\texttt{0x05} & High speed limit\\ +\texttt{0x06} & Traffic light (red)\\ +\texttt{0x07} & Traffic light (orange)\\ +\texttt{0x08} & Traffic light (green)\\ +\bottomrule +\end{tabular} +\caption{Sign lookup table} +\label{tab:protocol-signs} +\end{table} + +### Speed + +The speed value ranges from \num{0} to \num{1}, and is converted from the +command using the following formula: + +$$ v(n) = \frac{n - 16}{15} $$ + +### Steering + +The steering value is similar to the speed value, but ranges from \num{-1} +(left) to \num{1} (right). The zumo has a built in "influence" value, which +limits the smallest radius the robot can turn at. The steering value is +converted using the following formula: + +$$ s(n) = \frac{n - 32}{223}\cdot2-1 $$ + +## Zumo internal motor control functions + +The Zumo robot receives a speed and steering value. Because the protocol has a +limited precision due to the low amount of data sent, the following formula is +used to control motor speeds $M_1$ and $M_2$ from steering value $s$ and speed +value $v$. The constant $C_1$ is used to globally limit the speed the robot can +drive at. $C_2$ represents the amount of influence the steering value has on +the corner radius, where \num{0} is no steering at all and \num{1} completely +turns of one motor when steering fully left or right: + +$$ M_{1,2} = \frac{v(\pm s C_2 - C_2 + 2)}{2} C_1 $$ + +By default, $C_1 = \num{96}$ and $C_2 = \num{0.6}$ + +The Zumo firmware also smooths incoming values for $s$ and $v$ using a PID +controller. The default constants for the PID controller used are: + +\begin{align*} +K_p &= -0.02\\ +K_i &= +0.13\\ +K_d &= -300.0 +\end{align*} + # Research ## Detecting lines @@ -173,7 +338,7 @@ values without interpolation would lead to a garbage-in-garbage-out system. The simplest solution to motion blur is limiting the maximum speed the Zumo robot can drive at, which is the solution we're going to use as speed is not one of the criteria of the complete system\footnote{Problem statement -(\ref{problem-statement})}. +(section \ref{problem-statement})}. In the case the Nicla module crashes or fails to detect the road or roadsigns, it will stop sending commands. If the Zumo robot would naively continue at it's @@ -184,7 +349,7 @@ module is able to process at about 10 frames per second, so 2 seconds is a reasonable time-out period. \def\communicationConclusion{ -The complete protocol will consist of single byte commands. A byte can either +The complete protocol consists of single byte commands. A byte can either change the cart speed or steering direction, both will apply gradually. When no commands have been received for more than 2 seconds, the Zumo robot will gradually slow down until it is stopped. Exact specifications of commands are @@ -193,9 +358,35 @@ nog niet}. } \communicationConclusion +## Compiling and linking code for the Zumo + +This section tries to answer the question "What are possible debugging options +for code running on the Zumo robot?". + +Debugging running code can usually be done using an on-device debugger, and a +program that interfaces with the debugger and gcc on a computer. Because gcc +only gives valuable information when it has access to the executable file +running on the microcontroller, an attempt at making a makefile-based toolchain +was made. + +Pololu provides C++ libraries for controlling various parts of the Zumo's +hardware. These libraries make use of functions and classes that are part of +the Arduino core library. The Arduino libraries are all open source, and can in +theory be compiled and linked using make, but this would take more effort than +it's worth, since the Zumo has very little responsibility in the end product. + +\def\buildSystemConclusion{ +Because making a custom build system would take too much time, and because the +Zumo robot's code is very simple, unit tests are used to debug the Zumo's code. +For compiling and uploading the full Zumo firmware, the Arduino IDE is used in +combination with the standard Pololu boards and Libraries. +} +\buildSystemConclusion + # Conclusion \communicationConclusion +\buildSystemConclusion |