Realtime autonomous car for and ROS2 cross compiling

Jim Huang – National Cheng Kung UniversityColin Cheng – Providence University

Johnson Chang - National Chiao Tung UniversityAhua Wang - National Cheng Kung UniversityEdison Chen - National Cheng Kung UniversityJason Haung - National Cheng Kung University

duckiebot (From MIT)

Lane following

Original image

Homography transform

Line detection

w

Lane control procedure

Do color thresholding to extract the desired color area

Do canny edge detection

Do hough transform and get the segments

Apply Lane filter to get the best lane estimation

Do PID control

Original kernel

Latencymin: 4 (μs)

Avg: 206 (μs) Max: 159001 (μs)

Xenomai patched kernel

Latency:Min: 2 (μs)Avg: 11 (μs)Max: 36 (μs)

ROS2 cross compiling

Tested environment

Target Machine: Raspberry pi 3

Host operating system: Ubuntu 16.04Target operating system: Ubuntu Mate 16.04Cross compiler: Linaro GCC 5.3

CMakeCmake is compatible to do cross compile by setting some variables like:

CMAKE_SYSTEM_NAMECMAKE_C_COMPILERCMAKE_CXX_COMPILERCMAKE_SYSROOT

Please check:http://www.vtk.org/Wiki/CMake_Cross_Compiling

CMake

Please check:

https://github.com/ncku-ros2-research/cross-compile-ros2/blob/master/ros2_ws/rostoolchain.cmake

ROS2 for ARM machine

ROS2 alpha7+ require compiler able to compile C++11 program

And C++11 is only fully support on ARMv6+ machine

Root file systemThe symlink in rootfs directory will broken after copied from target machine because it used to point to an absolute path like: “/usr/lib/libxxx.so” but it is now locate to some path like “~/workspace/rootfs/usr/lib/libxxx.so”

This is quite tricky but can be fixed by writing a shell script

Root file system

Please check:

https://github.com/ncku-ros2-research/cross-compile-ros2/blob/master/tools/fixQualifiedLibraryPaths

Toolchain

Linaro GCC 5.3 (Newest release version right now)

Not recommand to build your own cross compiler (e.g: crosstool-ng)

Pkg-config wrapper

Few pkg-config’s environment variables need to be set for cross compiling purpose

PKG_CONFIG_LIBDIRPKG_CONFIG_SYSROOT_DIR

Pkg-config wrapper

#!/bin/bash#pkg-config wrapperROOTFS=$(realpath ../rootfs)ROS2_WS_PATH=$(realpath ../ros2_ws)

export PKG_CONFIG_DIR=export PKG_CONFIG_LIBDIR=${ROS2_WS_PATH}/install/lib/pkgconfig:${ROOTFS}/usr/lib/arm-linux-gnueabihf/pkgconfig:${ROOTFS}/opt/ros/kinetic/lib/pkgconfig:${ROOTFS}/usr/lib/pkgconfigexport PKG_CONFIG_SYSROOT_DIR=${ROOTFS}

pkg-config $@

Multi-ArchDebian/Ubuntu use multi-arch design and store the libraries in directories like: /usr/lib/arm-none-eabihf

In order to let compiler search these directories, the output message of command “arm-none-eabihf-gcc --print-multiarch” must be set

Native build as alternateSolution (add swap memory)1) $ sudo apt install dphys-swapfile2) $ vi /etc/dphys-swapfile add CONF_SWAPSIZE=40963) $ /etc/init.d/dphys-swapfile stop4) $ /etc/init.d/dphys-swapfile start

Use “htop” to check for new swap memory

LinksDuckietownhttp://duckietown.mit.edu/

Github:https://github.com/ncku-ros2-research/cross-compile-ros2

Slidehttps://www.slideshare.net/secret/BjQIsw6iifmzRa