CSCE 452/752: Project 2

Logistics

This assignment should be done individually.

Reference material

In addition to the concepts you used in Project 1 (nodes, topics, publishers, subscribers, etc.), you'll need to use services, parameters, and bags. You will likely want to consult the tutorials and reference documentation on those subjects.

Provided software

Download the newly-updated version

sim

package from this link and extract it into the

src

subdirectory in your ROS workspace.

ROS2

sim

package

You should use this package to complete this assignment, but should not modify anything in the

sim

package nor add anything to it.

Overview and purpose

This assignment asks you use the

sim2

simulator, an enhanced version of

sim1

from the previous project, to control the simulated robot to visit collection of sites efficiently and accurately. The purpose is to give some experience using ROS in a non-trivial context, along with some experience controlling the motion of (simulated) robots.

Your task

Create a ROS node that uses the

sim2

simulator to draw a line that visits a given set of targets. Each target is a line segment that the robot must touch. The robot's movement should be accurate (i.e. minimal extraneous movement) and fast. Here is an example of what a visualization of the completed project might look like:

a simulated robot that has visited a series of sites

Notice that this solution has room for improvement: There are at least two places where the robot makes slight turns when traveling straight through would have been faster. You should aim for a solution that does not make these mistakes.

Here are details about how

sim2

is set up to handle this problem:

The
sim2
node accepts a string parameter called
targets
that gives the name of the file from while the target points will be read. To find the file named by this parameter, the
sim2
node will look first in the current directory and then in the
share
directory of the
sim
package. Thus, by setting this parameter, you can test your program with the sample target files provided with the
sim
package and also with your own hand-crafted targets. You will want to learn how to include parameter values on the
ros2 run
command line.
The targets file is simply a list of line segments in YAML format. Each segment is a list of two points, and each point is a list of two floating point numbers. Here's an example, included in the
sim
package, defining four segments:
Contents of file: corners.targets
```
- [[4.0, 6.0],[6.0,4.0]]
- [[-4.0, 6.0],[-6.0,4.0]]
- [[4.0, -6.0],[6.0,-4.0]]
- [[-4.0, -6.0],[-6.0,-4.0]]
```
The visualization markers published by
sim2
include visualizations of the target segments. Your goal is to get the center of the robot to each of these segments. When a target is successfully visited, its color in this visualization will change.
You may discover that
sim2
publishes some other information that you'll find helpful. You are encouraged to explore its behavior.
The
sim2
node provides a
reset
service that returns everything to is initial state. This may be useful for testing your own program multiple times without restarting
sim2
.

Some details about how your program must work:

Before moving the robot, your program should clear any existing drawing using the
reset
service offered by
sim2
.
The robot does not need to visit the segments in the order in which they are given. On the contrary, your program should make intelligent choices about the order to visit the segments, along with the points on each segment to target, to keep the travel time small.
You should move the robot by publishing messages on the
cmd_vel
topic. Your program must publish at least $10$ messages per second on this topic. This is a minimum; you may publish more rapidly than this if you like. You can check this using the
ros2 topic hz
command.
You should visualize the results using
rviz
as in Project 1, including displays for the Robot Model and the Marker Array of simulation markers. It is recommended to use a white background.

The results will be evaluated based on adherence to these requirements, along with the speed of execution, the correctness of the results, and quality of your code.

What to submit

You should submit a single zip archive containing everything listed below:

A PDF report including:
1. A concise description of how the system works. This should be a couple of paragraphs, describing your overall approach at a conceptual level. Some questions to consider: What choices did you make in designing the program, and why? What nodes does your system contain, and what role does each one play? What specific constants are part of your method, and how did you select values for those constants?
2. A short answer to these questions: Did the results meet your expectations? Why or why not?
The source code for your program(s). This will span at least one source code file. Be sure to consult the source code style guide on the course website.
Recordings created by
ros2 bag record
of all topics throughout the entire execution of your program for each of the five input files included in the archive below:

Project 2 Inputs

It is essential for your submitted bags to contain all topics because this information will play a primary role in evaluating the correctness of your solution. We cannot evaluate bags that do not contain recordings of all topics, and will need to assign grades accordingly.
The directory of each bag file must be named with your TAMU netid. followed by a dash, followed by the number of the input bag file. For example, your instructor's submission would include bag directories called
jokane-1
,
jokane-2
, and so on. Incorrectly named bags cannot be graded.
Each rosbag recording is a directory which contains both a db3 file and a yaml file of metadata. You may rename this directory, but you should not modify the names or contents of the db3 or yaml files after recording, or you risk corrupting the rosbag. Corrupted rosbags cannot be graded. You should include the entire directory in your submission.

You may (but are not required to) also include:

A short video demonstrating your system in some way that may be helpful in grading.