Tutorial: constraint programming for robotics¶
Simon Rohou, Raphael Voges, Luc Jaulin, Benoît Desrochers
26th October – 22th November
This tutorial is proposed in the IROS 2020 Conference (International Conference on Intelligent Robots and Systems). It has also been proposed for the ICRA 2020 Conference this year.
This tutorial is about Constraint Programming (CP), Interval Analysis (IA) and their applications to mobile robotics.
Contents of this page
Presentation of the tutorial for the IROS conference¶
Raphael Voges (co-organizer) provides an overview of the tutorial in the following video:
Welcome message:
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Dear All,
The tutorial has started and we are pleased to see so many of you show interest in constraint programming (CP) and intervals for robotics!
Because the IROS conference became virtual this year, we had to think about some online way to provide the content of the tutorial. We prefer to let you handle the concepts of CP and intervals through programming applications. As a consequence, we provide the full explanations on webpages with equations, programming examples and images, instead of videos. We hope that this format is the best to let you understand these concepts and how to use libraries to apply them, at your own speed.
The tutorial is split into 4 weeks and each week involves 2 lessons. The 8 lessons consist of several questions that will take you step by step towards a comprehensive application of Simultaneous Localization And Mapping (SLAM). We recommend that you answer the questions in one source file per week (Python or C++) and upload it on the MOOC platform by the end of each week. Each Monday, we will post the corrections of the questions of the previous week, in order to ease your progression.
You may have questions about
the tutorial
difficulties to follow the lessons
C++/Python issues
or interrogations related to constraint programming, interval analysis or robotic applications
We will be happy to discuss with you about it, and we propose three ways of communication:
A forum available on the MOOC platform. You may find answers to your questions in previous topics
A Slack workspace for fast interactive exchanges, do not hesitate to use it!
Eventually, individual conversations with the organizers are possible. In this case, you can contact us by private message and we will schedule a slot for some Skype conversation
We do hope that this tutorial brings you a motivating introduction to intervals coupled with CP for robotics!
Let us start the first week with an introduction to the concepts of intervals and contractors (in Lesson A). These tools will be applied to a state estimation problem in Lesson B that requires a robot that is not yet moving to localize itself among three landmarks with range-only measurements.
Good luck!
Constraint programming?¶
There are several ways to deal with state estimation in mobile robotics. The constraint programming approach consists in defining a problem as a set of rules and letting a solver perform the estimation. For mobile robotics, rules are constraints coming from state equations.
Efforts have been done to propose operators and solvers to apply these constraints. The goal of this tutorial is to learn how to use them and understand the efficiency of the approach on realistic robotic applications. We will see that some problems that are difficult to solve with conventional methods (Kalman filters, particle approaches) can be easily dealt with by constraint programming. This is for instance the case of poor observation measurements, time uncertainties, delays, or when the initial conditions of the system are not known.
The tutorial will stand on the Tubex library, that provides tools for computations over sets of reals and trajectories. It has been designed to deal with dynamical systems defined by non-linear differential equations and involving constraints such as trajectory evaluations, time uncertainties or delays. These computations stand on interval analysis, a well suited tool that reliably propagates uncertainties.
Requirements¶
Prerequisite for attending the tutorial are:
basic knowledge of Python or C++ (the exercises are available in both languages);
although the tutorial is about state estimation, you do not need skills in Kalman or particle filters.
Contact and registration¶
Once you are registered, the organizers will be able to send you a link to the Slack workspace of the tutorial (please note that this is not automatic, we will do our best to send you the link as soon as possible).
The tutorial involves three platforms:
the Tubex website (here you are!)
the MOOC platform where you can send your work and get the tutorial diploma
the Slack communication workspace (tubex-tutorial.slack.com) for fast interactive meetings
This tutorial is proposed to the participants of the IROS conference. All the exercises are available on this Tubex website. The registration to the MOOC platform is not mandatory, except if you want to share with the organizers your progression and difficulties, and to obtain the diploma.
Diploma¶
Duration and meeting sessions¶
The tutorial will be held from 26th of October. More information about dates and interactive sessions are coming soon.
Interactive sessions are possible (each Tuesday afternoon, preferably). Just let us know by private message (via Slack or the MOOC platform) if you need to communicate directly with us (discussions can be made via Slack or Skype, let us know your choice).
Content of the tutorial¶
A list of exercises is proposed with realistic robotic applications:
Week 0: (installation)
Before starting the tutorial, you can read some words about the concepts of Constraint Programming and Interval Analysis. This will give you a first glimpse of the philosophy of this tutorial.
To get ready, you need to install the Tubex library on your computer. Please follow the related page of the manual to see how to do it:
Then, depending on your preference between C++ or Python, you can run some Hello World! program to be sure everything is working well so far:
Note
In case you encounter difficulties to install Tubex on your computer, an alternative solution is to try Tubex online with Repl.it. You will find more information on the following page:
Week 1: 26th October – 1st November
Week 2: 2nd November – 8th November
We will go a step further: now the landmarks are perceived with both range and bearing data. The resolution will involve new constraints, and a decomposition will be achieved. In the second part, we will tackle the problem of indistinguishable landmarks. We still assume that we know their position, but the robot is not able to make the association between the map and the observations. The goal of this exercise is to develop our own contractor to solve this problem.
Week 3: 9th November – 15th November
Now, we will make the robot move and see how we can handle uncertainties on trajectories. This will be done by solving the range-only problem of Lesson B, now in a dynamical context with asynchronous measurements.
Week 4: 16th November – 22th November
the video presenting the paper.The following video illustrates the result of Lesson H:
Organizers and technical support¶
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For any question, do not hesitate to use the MOOC platform of this tutorial, so that other participants can reply or see posted answers.
List of people who got the diploma¶
ICRA 2020 conference:
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IROS 2020 conference:
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