Ackermann_Steering_Control

Overview

Ackermann steering condition arises when axes of all wheels in a vehicle intersect at a single turning point. In the case of Ackermann steering the wheels of the vehicle do not skid while turning as opposed to parallel steering. This reduces the tyre wear and increases the energy efficiency. Ackermann steering can be used in various autonomous systems such as self-driving cars, delivery robots which can increase the efficiency of the robot.

During the development the following assumptions are made:

• All robot parameters are known.
• Initially the robot is on the origin of the world frame facing the x axis.
• Robot’s desired heading and velocity are given by the user as input.
• Maximum steering angle is 45 degrees.
• Friction and wheel slippage are considered negligible.

License

MIT License

Copyright (c) 2021 Pratik Bhujbal, Mohammed Maaruf Vazifdar, Maitreya Kulkarni.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Project Technologies:

• Ubuntu 18.04
• Build System: cmake
• Version control: GitHub
• Software Tools: VS Code
• Build Check: Travis
• Code Coverage: Coveralls

External Library:

• pbPlots (Covered under MIT License) : A plotting library used to show convergence to desired goals on graphs.

Deliverables

• Project: A robust Ackermann Steering Control, outputs are wheel angles and velocities.
• Graphical Representation of convergence of heading and speed to set points.
• Overview of proposed work that includes timelines risks and mitigations.
• UML Diagrams.
• Additon of Coveralls and travis for code coverage

Working

As the vehicle travels along a curved path, all four tyres follow unique trajectories around a shared turn centre, as defined by the blue arcs shown below.

For a given turn radius R, wheelbase L, and track width T, the required front steering angles (δ_(f,in) and δ_(f,out)) with the following expressions .And Similarly, we can calculate the wheel speeds using the following equations, where desired drive speed is denoted by 𝑽𝑫 while 𝑽𝑹𝑭, 𝑽𝑳𝑭 are front right and left wheel speed., 𝒍 denotes the length of vehicle, 𝒅 denotes the distance between wheel and kinematic centre and 𝝋 is steer angle.

Risk and Mitigations

• Robot can't go in backward direction. For this case can implement more cases instead of just go around by making a full turn in forward direction.
• User can't give input heading in negative instead have to give positive value from 0-3.14 (in radians).

Results

For a specific set of inputs, the desired speed and the desired heading angle is acheived within expected range of +-5%. Example shown below with convergence for input as 0.1 and 20 for desired heading and speed and output with each forward wheel velocities and angles.

Output on graphs for same inputs showing convergence for speed and heading:

UML Diagrams:

• Activity Diagram

• Class Diagram

Quad Chart

Agile Iterative Process (AIP)

The general idea is to split the development of the software into sequences of repeated cycles (iterations).

Agile Iterative Process Link

Sprint planning notes and review

The purpose of sprint planning is to define what can be delivered in the sprint and how that work will be achieved.

Sprint planning docs link

Phase_2 Video Submission

Final Report file

Build And Execute

After Execution graphs will be saved under build folder.

cd your_ws/
git clone --recursive https://github.com/Prat33k-dev/Ackermann_Steering_Control.git
cd Ackermann_Steering_Control/
mkdir build
cd build/
cmake ..
make 
Running tests: ./test/cpp-test
Running the controller: ./app/ackerman_steering_controller

Run cppcheck and cpplint

For cppcheck

sh run_cppcheck.sh

For cpplint

sh run_cpplint.sh 

Building for code coverage

sudo apt-get install lcov
cmake -D COVERAGE=ON -D CMAKE_BUILD_TYPE=Debug ../
make
make code_coverage

Authors

• Pratik Bhujbal UID: 117555295
  Github URL: https://github.com/prat33k-dev
• Maitreya Kulkarni UID: 117506075
  Github URL: https://github.com/maitreya98
• Maaruf Vazifdar UID: 117509717
  Github URL: https://github.com/maarufvazifdar