Perceptive and torque-control NMPC

h1. Perceptive and torque-control NMPC wiki

h2. I - Software Overview

h3. I.1. Openrobots

Collections of all the open-source software used at LAAS. You can find more details in "Openrobots Wiki-Homepage":https://www.openrobots.org/wiki

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h3. I-2. Robotpkg

"Robotpkg":http://robotpkg.openrobots.org/ is a packaging system for installing robotics software developed by the robotic community.

We will use robotpkg to install the required modules for the simulations (state estimation, gazebo interface...) as well as third-party dependencies (qpOases).

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h3. I-3. GenoM

The Generator of Modules, aka GenoM, generator of modules, designed to be middleware independant, i.e. the same module can be compiled for, e.g., ROS or Pocolibs, without any modification.

This allows a great code re-usability and to abstract the user from any specific choice of a middleware.

Originally GenoM has been developed tightly with Pocolibs, then from version 3, aka GenoM3, ROS templates has been provided.

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Another specificity of GenoM is the interaction with and between components.

Each component is started independantly like a linux executable (within a roscore, for ROS, or a h2 intance, for Pocolibs), then the connection between ports (or topics) is made using a supervisor, "Genomix":https://git.openrobots.org/projects/genomix, either with it "Matlab":https://git.openrobots.org/projects/matlab-genomix or "TCL":https://git.openrobots.org/projects/tcl-genomix. 

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h3. I-4. Pocolibs

"Pocolibs":https://www.openrobots.org/wiki/pocolibs/ is a middleware, like ROS.

It aims at being more performant and faster than ROS, when running on a single machine, thanks to the exploitation of shared memory. ROS, on the other hand, uses a network layer for sending messages between nodes, this leads to greater delays and loss of performances.

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h3. I-5. TeleKyb

The "TeleKyb":https://git.openrobots.org/projects/telekyb3 software platform provides the aerial-robotic oriented softwares developped at LAAS-CNRS.

In particular, we will use:

* "mrsim":https://git.openrobots.org/projects/mrsim-genom3 a Multi-Robot SIMulator. It is design to be a transparent interface w.r.t. the real aerial vehicles used in LAAS-CNRS. It makes the transition between simulation and experiment transparent, from the software point of view.

* "pom":https://git.openrobots.org/projects/pom-genom3 a UKF-based state estimator merging state feedback for different sources (e.g. mocap + IMU)

* "optitrack":https://git.openrobots.org/projects/optitrack-genom3 export the motion capture data to the genom software stack

* "rotorcraft":https://git.openrobots.org/projects/rotorcraft-genom3 low-level interface, with either the simulated or real platform

* "nhfc":https://git.openrobots.org/projects/nhfc-genom3 near-hovering flight controller, used for unmodeled take-off and post-failure recovery

* "maneuver":https://git.openrobots.org/projects/maneuver-genom3 a global trajectory planner, providing position and attitude (as quaternions) as well as first and second derivatives. It implement take-off and waypoint-to-waypoint motions. A joystick-based velocity control is implemented, but not used in this project.

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h3. I-6. Gazebo

To simulate the platform, we use the "Gazebo":http://gazebosim.org/ simulator. To interface it with the genom software stack, we use two dedicated components:

* "mrsim-gazebo":https://git.openrobots.org/projects/mrsim-gazebo a plugin to interface the simulated multi-rotor with the genom components (in place of mrsim)

* "optitrack-gazebo":https://git.openrobots.org/projects/optitrack-gazebo emulates the optitrack network interface to publish the model poses

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h2. II - Installation procedure

This section is a tutorial on how to install the software architecture to run the simulations.

Note that everything has been tested on Ubuntu 18.04 since it is the OS used by the LAAS-CNRS robotic platform. It should work seamlessly on other OS, but there is no guarantee.

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h3. II-0. Clone the Perceptive and torque-control NMPC repository

Clone the repo associated to this project. Its root will act as the devel folder for the following.

<pre><code class="shell">

git clone git://redmine.laas.fr/laas/perceptive-torque-nmpc.git

cd ./perceptive-torque-nmpc/

</code></pre>

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To simplify the installation, we provide some environment variables in the @env.sh@ file.

In order to run all the installed executables, we need to setup the path to the newly created folders.

We provide a @env.sh@ script that exports all the required variables. In the root folder, do:

<pre><code class="shell">

source env.sh

</code></pre>

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h3. II-1. Setup robotpkg

(Steps taken from http://robotpkg.openrobots.org/install.html)

h4. 1. Clone the robotpkg lastest release:

<pre><code class="shell">

git clone git://git.openrobots.org/robots/robotpkg

</code></pre>

h4. 2. Create an install folder called @openrobots/@, and update the environement variables accordingly, to ease the future steps:

<pre><code class="shell">

export ROBOTPKG_BASE=`pwd`/openrobots

</code></pre>

h4. 3. Install robotpkg

<pre><code class="shell">

cd robotpkg/bootstrap

./bootstrap --prefix=$ROBOTPKG_BASE

</code></pre>

h4. 4. Install the required components and there dependencies

The installation can be done 'manually' by navigating to the desired folder in @./robotpkg/@ and install with @make update@; but we will simplify the process using a _set_.

To do so, we need to edit the config file: @$ROBOTPKG_BASE/etc/robotpkg.conf@. Add the following at the end of the file:

<pre><code class="shell">

PKG_OPTIONS.%-genom3 = \

        codels \

        pocolibs-server \

        pocolibs-client-c

PKGSET.mpcset = \

    sysutils/arduio-genom3 \

    architecture/genom3 \

    architecture/genom3-pocolibs \

    robots/rotorcraft-genom3 \

    localization/pom-genom3 \

    localization/optitrack-genom3 \

    motion/nhfc-genom3 \

    optimization/qpoases \

    net/genomix \

    supervision/matlab-genomix \

    supervision/tcl-genomix \

    shell/eltclsh \

    simulation/mrsim-genom3 \

    simulation/mrsim-gazebo \

    simulation/libmrsim \

    simulation/optitrack-gazebo

PREFER.lapack = robotpkg

PREFIX.matlab = <path/to/Matlab>

</code></pre>

The last line need to point to the Matlab root folder in the system (e.g. @/opt/Matlab@).

It is recommanded to use Matlab for the proposed simulations since the syntax is more intuitive and comprehensible for the user to modify them. However, we also provide all the launch files in tcl, as well as the environment to run them (@shell/eltclsh@ in the above list is a custom tcl script shell).

Also, all the above is meant for using Pocolibs, not ROS. Futur version of this tutorial might come to use the ROS install.

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Now return to the robotpkg folder and install all the set:

<pre><code class="shell">

cd ..

make update-mpcset

</code></pre>

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During the installation, some required dependencies need to be install with the usual package manager (e.g. @apt@ on Ubuntu). When the install stops, install the required packages and rerun the above command.

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h4. 5. Matlab configuration

The last step is to update Matlab path to use the custom libraries, if relevant.

Add the following paths in the Matlab path window:

<pre><code class="shell">

</path/to/openrobots>/lib/matlab

</path/to/openrobots>/lib/matlab/simulink

</path/to/openrobots>/lib/matlab/simulink/genomix

</code></pre>

(change </path/to/openrobots> to the content of @$ROBOTPKG_BASE@)

h3. II-2. Install custom components

h4. List of the components

The @src/@ folder contains some additional components, in particular:

* *vision-idl*: the type declaration regarding the camera modules

* *camgazebo-genom3*: read the data from the gazebo inate cameras, via the gazebo API

* *camviz-genom3*: record and/or display the images from a camera

* *arucotag-genom3*: detect and filter (EKF-based) the ArUco markers/tags

* *maneuver-genom3*: custom version of maneuver (already mentionned) that publishes the reference trajectory for a specified receding horizon

* *uavmpc-genom3*: the NMPC controller presented in the pape

h4. Install the extra components

Since it they are not considered 'stable' as the one provided in robotpkg, we rather install them in a devel folder.

Go to the project root, init the devel folder and go to the sources:

<pre><code class="shell">

export DEVEL_BASE=`pwd`/devel

cd src/

</code></pre>

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Each component here has to be installed manually, using @autoconf@. To do so, proceed as follow:

<pre><code class="shell">

cd src/<component>/

./bootstrap.sh

mkdir build

cd build

../configure --prefix=$DEVEL_BASE --with-templates=pocolibs/client/c,pocolibs/server

make

make install

</code></pre>

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The component @vision-idl@ has to be installed first since it defines some type headers used by others.

The installation of the main component, @uavmpc-genom3@, is described in the next subection.

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h4. Install the MPC controller

Before installing the MPC controller, we have to generate the @C@ sources corresponding to the desired model.

To do so, go to the @model_generation/@ folder:

<pre><code class="shell">

cd src/uavmpc-genom3/model_generation

</code></pre>

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There is a README.md file there, explaining the requirements.

In short, the model sources are exported to @C@ using @CasADi@ in @python3@.

@python3@ along with @NumPy@, @SciPy@ and @CasADi@  are required, and easily installable on most Linux distributions (e.g. with @apt@ and @pip3@).

Then, the sources are generated using:

<pre><code class="shell">

python3 gen_model.py <quad or hexa>

</code></pre>

Then install the component as explained before, but add the following flags to the @configure@ command:

<pre><code class="shell">

../configure --prefix=$GENOM_DEVEL --with-templates=pocolibs/client/c,pocolibs/server CFLAGS='-Wall -O3 -march=native -mfpmath=sse' CXXFLAGS='-std=c++14 -Wall -O3 -march=native -mfpmath=sse' CPPFLAGS='-I$ROBOTPKG_BASE/include' LDFLAGS='-L$ROBOTPKG_BASE/lib -Wl,-R$ROBOTPKG_BASE/lib'

</code></pre>

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h3. II-3. Setup the environment

In order to run all the installed executables, we need to setup the path to the newly created folders.

All the required variables are exported in the @env.sh@ file.

h2. III - Running the simulation

We @ws/@ folder contains all the material to run a basic simulation with the NMPC.

In a terminal, launch the @launch.sh@ script. It starts all the genom components, in background. It is used as a console since it displays warnings or error during runtime.

In another terminal, start gazebo with one of the world file provided.

Finally, run @matlab@ or @eltclsh@ and go to the relevant subsection below.

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h3. III.1. Running the simulations with Matlab

Change the flag at the top of the script to use either the quadrotor or the hexarotor.

Change also the variable @devel_path@ to the value of @$DEVEL_BASE@

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The provided scripts are organised as follow

* The two @param_*.m@ scripts provide the parameters for either a standard colinear quadrotor (denoted *qr*) and a tilted-propeller hexarotor (denoted *hr*).

* The @init.m@ script that connects all the components together and call the initialization services for all provided components.

* The @traj_*.m@ that runs the specific trajectories for a specific scenario.

Launch the script then press enter between each step to proceed to the next one. The evolution can be watched in gazebo and in the console terminal in parallel.

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h3. III.2. Running the simulations with tcl

The tcl scripts are called from the @eltclsh@ shell environment.

In order to run the script and keep the variables in the environment, use the @source@ command.

The script architecture is the same as the matlab one. Change the flag and @devel_path@ in the init.tcl script, then:

<pre><code class="tcl">

source init.tcl

source traj_<name_name>.tcl

</code></pre>

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h3. III.3. List of the provided trajectories

* @traj_mpc@ runs a flight using the nmpc without any perceptive constraint, reaching successive waypoints.

* @traj_track@ runs a flight using the nmpc with a couple of perceptive constraints, again reaching successive waypoints.

It corresponds to the experiment presented in section *V-B* in the paper.

* @traj_follow@ runs a flight where we follow a _target_ quadrotor equipped with a marker. The NMPC-controlled UAV needs to stay on top of it, while the _target_ quadrotor is given successive waypoints.

It corresponds to the experiment presented in Section *V-C* in the paper.