CarND-Controls-PID

Self-Driving Car Engineer Nanodegree Program

Overview

This project makes use of a PID controller to steer a car, when the distance from the center of the road is known. The objective of the project is to continously update steering angles such that the car always stays in the center of the road.

PID Controller

PID stands for (P)roportional (I)ntegral and (D)erivative. This type of controller will help us keep the CTE (cross-track error) as small as possible.

cte = road_center_position - car_position
steer_angle = P * cte + I * sum(cte) + D * time-derivate(cte)

##Parameter optimisation

The easiest way is to tune the P, I, and D hyperparameters by hand. For this project, the values for the same were fine-tuned to:

P = 0.2 I = 0.00443 D = 3

##Final Solution

The PID for steering-angle has been tuned for a velocity of 25 mph, and in some parts of the road manages to touch 40-50 mph. Above that, the steering performance degrades.

double speed_factor = 25.0 / (speed + 1.0);
steer_value = speed_factor * pid_value;

Apart from the steering-angle controller, I utilise another PID controller to feedback velocity. This helps in cases where there are sharp turns, allowing the car to slow down.

pid_speed.Init(0.4, 0, 3.5);
double throttle = 0.5 + pid_speed_value;

Disadvantages

The PID controller needs to be very finely tuned and has to have a good update-rate for higher speeds. Also, because of the way the algorithm for the PID controller works, the controller behaves reactively, since it has no vision of the future parts of the road [humans can see and anticipate required steering angle and speed].

Dependencies

cmake >= 3.5
All OSes: click here for installation instructions
make >= 4.1
- Linux: make is installed by default on most Linux distros
- Mac: install Xcode command line tools to get make
- Windows: Click here for installation instructions
gcc/g++ >= 5.4
- Linux: gcc / g++ is installed by default on most Linux distros
- Mac: same deal as make - [install Xcode command line tools]((https://developer.apple.com/xcode/features/)
- Windows: recommend using MinGW
uWebSockets
- Run either ./install-mac.sh or ./install-ubuntu.sh.
- If you install from source, checkout to commit e94b6e1, i.e.
```
git clone https://github.com/uWebSockets/uWebSockets 
cd uWebSockets
git checkout e94b6e1
```
  Some function signatures have changed in v0.14.x. See this PR for more details.
Simulator. You can download these from the project intro page in the classroom.

There's an experimental patch for windows in this PR

Basic Build Instructions

Clone this repo.
Make a build directory: mkdir build && cd build
Compile: cmake .. && make
Run it: ./pid.

Editor Settings

We've purposefully kept editor configuration files out of this repo in order to keep it as simple and environment agnostic as possible. However, we recommend using the following settings:

indent using spaces
set tab width to 2 spaces (keeps the matrices in source code aligned)

Code Style

Please (do your best to) stick to Google's C++ style guide.

Project Instructions and Rubric

Note: regardless of the changes you make, your project must be buildable using cmake and make!

More information is only accessible by people who are already enrolled in Term 2 of CarND. If you are enrolled, see the project page for instructions and the project rubric.

Hints!

You don't have to follow this directory structure, but if you do, your work will span all of the .cpp files here. Keep an eye out for TODOs.

Call for IDE Profiles Pull Requests

Help your fellow students!

We decided to create Makefiles with cmake to keep this project as platform agnostic as possible. Similarly, we omitted IDE profiles in order to we ensure that students don't feel pressured to use one IDE or another.

However! I'd love to help people get up and running with their IDEs of choice. If you've created a profile for an IDE that you think other students would appreciate, we'd love to have you add the requisite profile files and instructions to ide_profiles/. For example if you wanted to add a VS Code profile, you'd add:

/ide_profiles/vscode/.vscode
/ide_profiles/vscode/README.md

The README should explain what the profile does, how to take advantage of it, and how to install it.

Frankly, I've never been involved in a project with multiple IDE profiles before. I believe the best way to handle this would be to keep them out of the repo root to avoid clutter. My expectation is that most profiles will include instructions to copy files to a new location to get picked up by the IDE, but that's just a guess.

One last note here: regardless of the IDE used, every submitted project must still be compilable with cmake and make./

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caje731 / CarND-PID-Control-Project