Mission Planning Optimization

Problem similar to prize-collecting TSP solved with implementation of branch & bound and revised simplex algorithm
as a project for the course of Combinatorial Decision Making and Optimization (Master’s degree in AI) of University of Bologna.

Table of contents

1. Installation
2. Usage
3. Example
4. JSON files
   1. Map and Grid Size
   2. Problem Parameters
   3. Agent Parameters
5. Details
6. Problems

" class="reference-link">Installation

Tested on python3.6 and python3.8, a few changes in the code are required for it to work with python2.

python3 -m pip install numpy matplotlib

" class="reference-link">Usage

The main class can be found in mission_optimizer.py, it requires a few information about the map and the agent,
in particular, it needs:

• The coordinates of all the obstacles
• The coordinates of the starting position
• The coordinates of all the goals
• The reward and the difficulties associated to each goal
• The cost associated to each number of changes of direction
• The maximum time available to collect as much points as possible
• The maximum energy available

All these parameters should be written in json files, as shown in “main.py”.

In order to change the constraints one would need to work on the method “create_A_b”, in “mission_optimizer.py”.

The trajectories are computed by the script “a_star.py” taken from PythonRobotics
and adapted in order to work with multiple goals, the script is called internally by the “MissionPlanOptimizer” class.
The path which maximizes the collected price, while minimizing the cost and keeping the energy
and time requirements under the given thresholds, will be printed on the terminal.

" class="reference-link">Example

An example of usage is given in the script main.py:

python3 main.py

" class="reference-link">JSON files

In the following paragraph are describe the json files used to represent map, obstacles, goals and agent parameters.

" class="reference-link">Map and Grid Size

The map description, along with the grid size with which to discretize the map, should be written in “map.json”, as:

• A dictionary, named “walls”, which contains two lists of integers of coordinates for the vertices of the walls.
  "walls": {"x": [0, 0, 100, 100],"y": [0, 100, 100, 0]}
• A dictionary, named “obs_n”, which contains two lists of integers of coordinates for the vertices of the n-th obstacle, for each obstacle.
  "obs_1": {"x": [10, 10, 30, 30],"y": [10, 30, 30, 10]}
• An integer parameter, called “grid_size”, which is used as value for the discretization of the map.

" class="reference-link">Problem Parameters

The problem parameters, i.e. goals’ coordinates, rewards, difficulties and max time and energy, should be written
in the file “problem_par.json”, as:

• A list of integers, named “goals_x”, with the x-coordinates of the goals
• A list of integers, named “goals_y”, with the y-coordinates of the goals
• A list of integers, named “rewards”, with the reward associated to each goal
• A list of float between 0 and 1, named “difficulties”, with the difficulties associated to each goal
• An integer, called “max_t”, which represents the maximum time available
• An integer, called “max_e”, which represents the maximum energy available

" class="reference-link">Agent Parameters

The file “agent_par.json” contains the parameters associated to the agent, such as:

• An integer, called “robot_radius”, which represents the radius of the agent
• A float, called “vel”, that represents the constant velocity of the agent
• A dictionary, called “costs_changes”, where each key is a number of changes of direction and has as value the cost associated to it;
  one “default” key should also be provided.

" class="reference-link">Details

More information can be found in the pdf report available in the repository.

" class="reference-link">Problems

This repo uses a home-made implementation of branch & bound and revised simplex algorithm, required for the course, but it is not without problem,
these are the first that come to mind:

• Missing anti-cycling rule in “simplex.py”.
• Big-M method used for branching in “mission_optimizer.py” may be not working at its best.

Obviously, one could use a python library, such as pulp, to write the constraints and solve the problem in a more efficient way.