RobotPathfinder

           

Robot motion profiler/path planner for tank drive (aka skid-steer or differential drive) robots. Developed by Tyler Tian for use by FRC Team 6135 (Arctos). Inspired by and partially based on Pathfinder by Jaci Brunning.

RobotPathfinder is intended as an improvement over Pathfinder for tank drivetrains. As such, it does not have support for other drivetrains, but has these features:

• Smooth path generation with 3 different fit types
• Respects maximum velocity constraints for both wheels, even when turning
• Allows wheels to turn backwards if turns are too tight
• Simple motion profiles that can be re-generated on-the-fly for maximum speed and accuracy
• Handy methods that allows the mirroring and retracing of trajectories
• Follower class that can be set to follow position, velocity, acceleration and direction
• And much more...!

Purpose

Given an array of waypoints, each with coordinates, a heading, and optionally a velocity, RobotPathfinder generates a smooth path that follows all the waypoints. Then, using that path, it generates left and right wheel trajectories for a robot to follow in order to achieve the desired path.

Example path:
Trajectory for the example path:
These graphs are generated using JMathPlot. You can find its repository here.

A Note on Versions

There are currently 3 major versions of RobotPathfinder (v1, v2 and v3):

• v1 is outdated and inaccurate. You should never use it.
• v2 has been extensively used and tested and is stable.
• v3 is still in its alpha stage. It uses native code to speed up execution and is on average 4 times as fast as v2. The API is still undergoing rapid development, so usage at this moment is not recommended unless you know what you're doing.

Usage

Every release contains 3 jars, 1 zip, and numerous dynamic libraries:

• RobotPathfinder-(VERSION).jar - The basic jar that contains the library, but without some dependencies. This is the jar recommended for use on a robot. It does not contain the dependencies required for graphing.
• RobotPathfinder-(VERSION)-all.jar - The fat jar that contains the library as well as all its dependencies (JMathPlot, Gson).
• Trajectory-Visualizer-(VERSION).jar - The executable jar that contains the GUI Trajectory Visualization Tool (and all its dependencies).
• RobotPathfinder-Doc-(VERSION).zip - The zip that contains the Javadocs for all classes and methods.
• libRobotPathfinder-(PLATFORM).so - (In v3 only) The native dynamic library used by RobotPathfinder for a specific Linux arch.
• RobotPathfinder-(PLATFORM).dll - (In v3 only) The native dynamic library used by RobotPathfinder for a specific Windows arch.

Alternatively, you can build the binaries yourself by navigating to the root directory, and running ./gradlew allArchives --rerun-tasks. (If you're on a Windows machine, make sure you're using PowerShell not cmd!) The archives can then be found under the archives directory.

In order to use RobotPathfinder v3, the correct dynamic library for your platform must be present in either the directory java is invoked from, or the library path.

FRC Usage

GradleRIO

• Put the jar and (v3 only) the native library for roboRIO in a folder somewhere in the project, e.g. lib (if using v3, make sure to rename the dynamic library from libRobotPathfinder-roboRIO.so to just libRobotPathfinder.so!)
• In build.gradle, under dependencies, add this line: compile files('path/to/jar') and (v3 only) nativeLib files('path/to/native-lib')
• Your new dependencies should look something like this:

dependencies {
    compile wpi.deps.wpilib()
    compile wpi.deps.vendor.java()

    compile files('lib/RobotPathfinder-3.0.0-alpha.0.jar')
    nativeLib files('lib/libRobotPathfinder.so') // v3 only
    
    nativeZip wpi.deps.vendor.jni(wpi.platforms.roborio)
    nativeDesktopZip wpi.deps.vendor.jni(wpi.platforms.desktop)
    testCompile 'junit:junit:4.12'
}

Eclipse

• Put the jar in a folder somewhere in the project, e.g. lib
• Expand the project in Eclipse, right-click Referenced Libraries, Build Path -> Configure Build Path
• In the dialog that pops up, click Add Jars, navigate to and select the library jar, and confirm
• Put a copy of the jar or a simlink to it in the WPILib Java libraries directory (C:\Users\USERNAME\wpilib\user\java\lib on Windows and /home/USERNAME/wpilib/user/java/lib on UNIX-based systems).

For RobotPathfinder v3 an extra step is needed to copy the dynamic library.

• In a terminal, copy over the dynamic library using scp:

scp /path/to/dynamic/library [email protected]:/usr/lib/libRobotPathfinder.so

where TE.AM is your team number (e.g. for team 6135 this would be 61.35). Make sure you're connected to the robot's wifi when doing this!

Documentation

All classes and methods are documented with Javadocs, in RobotPathfinder-Doc-(VERSION).zip. The Javadocs of most versions are also available online here. Head over to the wiki for tutorials and examples! Wiki pages for RobotPathfinder v3 are coming soon.

GUI Trajectory Visualization Tool

A GUI Trajectory Visualization Tool in the form of an executable jar is included with every release.

This tool generates path and trajectory graphs from waypoints and robot specification parameters; it can be used to preview paths and trajectories and check if a path is possible without having to write code for it.

Features include:

• Creating path and trajectory graphs
• Saving waypoint data and robot specification parameters (CSV)
• Code generation

To run the Trajectory Visualizer V3, make sure that you have the correct dynamic library on your library path or in the directory where java is invoked!

Building

This project uses Gradle as the build system. From the project root directory, running ./gradlew allArchives will build the project and generate the jars and a zipped Javadoc under the /archives/ directory. Alternatively, here are a list of commonly used tasks:

• ./gradlew build builds the project and generates the library jar under /build/libs/
• ./gradlew test runs all unit tests
• ./gradlew visualizerJar generates the Trajectory Visualization Tool jar under /build/libs/
• ./gradlew copyJars copies the generated jars to /archives/
• ./gradlew javadoc generates Javadocs under /build/docs/javadoc
• (In v3 only) ./gradlew testJavadoc generates Javadocs for the test classes, under /build/docs/testJavadoc
• (In v3 only) ./gradlew completeJavadoc generates Javadocs all classes (main and test), under /build/docs/completeJavadoc
• ./gradlew zipDoc zips the generated docs into /archives/
• ./gradlew allArchives builds all the archives and copies it into /archives/
• (In v3 only) ./gradlew updateJNIHeaders will re-generate the JNI headers and copy them to /src/main/cpp/include/jni
• (In v3 only) ./gradlew copyLibDebug will copy the debug dynamic library for the current platform to the root project folder
• (In v3 only) ./gradlew copyLibRelease will copy the release dynamic library for the current platform to the root project folder
• (In v3 only) ./gradlew jacocoTestReport generates a code coverage report for the test task using JaCoco

For all tasks, see the archives of ./gradlew tasks. Note that the archives directory can be changed by changing the archiveDir property of the project. For example, ./gradlew allArchives -ParchiveDir=myArchiveDir will put all the archives under myArchiveDir.

Note

All classes are currently under the top-level package com.arctos6135.robotpathfinder. This is because when the package was decided, the library was being developed solely for use by Arctos 6135 and under the Arctos6135 organization. It was later transferred under my name because nobody else on the team has actually worked on the project at all whatsoever, and to keep the API consistent, I decided not to change the packages.